Toxicology – Chromium

Core concept

Chromium toxicity depends critically on oxidation state.

The clinically important distinction is:

Hexavalent chromium [Cr(VI)] = highly toxic, corrosive, oxidizing, sensitizing, and carcinogenic

whereas:

Trivalent chromium [Cr(III)] = poorly absorbed and substantially less toxic

The characteristic acute severe syndrome after ingestion of a soluble Cr(VI) compound is:

Caustic gastroenteritis → GI hemorrhage/fluid loss → shock + acute kidney injury + hepatic injury ± coagulopathy/multiorgan failure

Chronic occupational Cr(VI) exposure primarily causes:

Nasal/airway irritation + septal ulceration/perforation + dermatitis/chrome ulcers + occupational asthma + increased lung-cancer risk

The most important modern management principle is:

Treat acute Cr(VI) ingestion as both a severe caustic exposure and a potentially systemic multiorgan poison.

There is no proven specific antidote.

Important Chromium Species

Chromium exists in several oxidation states, but the most relevant are:

Chromium(0)

Metallic chromium.

Used in:

• Stainless steel
• Alloys
• Metal production

It is much less biologically reactive than Cr(VI).

Chromium(III)

Examples include:

• Chromium chloride
• Chromium sulfate
• Chromium oxide

Cr(III):

• Crosses cell membranes poorly
• Is poorly absorbed from the GI tract
• Is much less systemically toxic than Cr(VI)

However:

“Less toxic” does not mean completely harmless.

Specific Cr(III) salts, dusts, or formulations may still cause:

• Local irritation
• Dermatitis
• Occupational exposure problems

The older statement that there is essentially no evidence of Cr(III) toxicity is therefore too broad.

Chromium(VI)

Important Cr(VI) compounds include:

• Chromic acid
• Chromium trioxide
• Potassium chromate
• Potassium dichromate
• Sodium chromate
• Sodium dichromate
• Ammonium dichromate
• Zinc chromate
• Strontium chromate

Cr(VI) is the principal toxicologic concern.

NIOSH lists chromic acid/chromates as capable of causing:

• Respiratory irritation
• Nasal septal perforation
• Kidney/liver injury
• Eye injury
• Skin ulceration
• Sensitization dermatitis
• Lung cancer.

Common Occupational Sources

Exposure occurs particularly during:

• Chrome electroplating
• Stainless-steel welding/cutting
• Chromate pigment manufacture/use
• Stainless-steel and alloy production
• Aerospace painting
• Metal finishing
• Leather tanning
• Wood preservation
• Textile/dye work
• Chromate chemical production
• Work with wet cement containing trace Cr(VI)

NIOSH specifically identifies welding, steel work, electroplating, chromate painting, wood preservation, textile dyeing, and cement work as important Cr(VI) exposure settings.

Why Cr(VI) Is So Much More Toxic

Cr(VI) resembles:

• Sulfate
• Phosphate

anions.

Therefore:

Cr(VI) → enters cells through nonspecific anion transporters

Once intracellular:

Cr(VI) → Cr(V) → Cr(IV) → Cr(III)

during reduction by substances such as:

• Ascorbate
• Glutathione
• Cysteine

This intracellular reduction generates:

• Reactive intermediates
• Reactive oxygen species
• DNA adducts
• DNA-protein cross-links
• Oxidative DNA injury

and contributes to both:

Acute cellular toxicity + carcinogenesis

EPA describes this cellular uptake/reduction mechanism as central to Cr(VI) genotoxicity.

Extracellular Reduction Can Be Protective

An important paradox is:

Cr(VI) reduced to Cr(III) before cellular uptake → generally less toxic

because Cr(III) crosses membranes much less readily.

But:

Cr(VI) reduced after entering the cell → reactive intermediates + cellular damage

This is important when considering proposed vitamin C therapy.

Toxic Dose

There is no sufficiently reliable single dose threshold to guide clinical management.

Historical estimates have placed severe or potentially lethal oral Cr(VI) exposure in approximately the:

50–70 mg/kg range

but major interindividual variation exists, and case reports include both death and survival across a wide range of doses. OSHA has historically cited lethal oral chromate exposures around this range.

Therefore:

Do not use a reported “0.5–1 g lethal dose” as a fixed rule.

Severity depends on:

• Specific Cr(VI) compound
• Concentration
• Solubility
• Dose
• Route
• Delay to treatment
• Degree of caustic GI injury

Acute Ingestion – Clinical Syndrome

Soluble Cr(VI) salts are powerful oxidizing corrosives.

The early syndrome often begins with:

Oral/GI chemical burn → nausea/vomiting → abdominal pain → profuse diarrhea ± GI bleeding

Severe systemic poisoning may then progress to:

Shock → AKI + hepatic injury + coagulopathy → multiorgan failure

Fatal dichromate poisonings have demonstrated rapid progression from gastrointestinal symptoms to hemorrhage, renal/hepatic injury and systemic collapse.

Gastrointestinal Effects

Possible findings include:

• Burning of mouth/throat
• Odynophagia
• Dysphagia
• Severe abdominal pain
• Nausea
• Vomiting
• Diarrhea
• Hematemesis
• Hematochezia
• GI mucosal necrosis

Severe exposures can cause:

• Massive GI hemorrhage
• Perforation
• Peritonitis
• Profound fluid loss
• Hemorrhagic shock

The clinical picture may resemble ingestion of a strong acidic corrosive.

Cardiovascular

Severe Cr(VI) poisoning can produce:

• Tachycardia
• Hypotension
• Circulatory collapse
• Shock

Mechanisms include:

• GI fluid loss
• Hemorrhage
• Capillary/tissue injury
• Metabolic derangement
• Multiorgan toxicity

Renal Toxicity

The kidneys are major systemic target organs.

Possible manifestations include:

• Proteinuria
• Hematuria
• Acute tubular injury
• Oliguria/anuria
• Acute kidney injury

Renal failure is a classic complication of major dichromate poisoning.

Hepatic Toxicity

Severe systemic poisoning may cause:

• Aminotransferase elevation
• Hepatocellular injury
• Acute hepatitis
• Severe hepatic dysfunction

Combined:

AKI + hepatic injury + GI hemorrhage

is particularly suggestive of major systemic dichromate poisoning when exposure history is compatible.

Hematologic Toxicity

Severe poisoning may cause:

• Anemia
• Thrombocytopenia
• Hemolysis
• Coagulopathy
• DIC-like abnormalities

Methemoglobinemia has also been reported in catastrophic dichromate poisoning, but it is not a universal or defining feature.

Neurologic Toxicity

Neurologic effects are usually secondary to severe systemic illness and may include:

• Confusion
• Lethargy
• Encephalopathy
• Coma

Possible contributors include:

• Shock
• Acidosis
• Renal failure
• Hepatic failure
• Hypoxemia

Respiratory Toxicity – Acute Inhalation

Cr(VI) dusts and mists can cause:

• Nasal irritation
• Sore throat
• Cough
• Dyspnea
• Bronchospasm
• Wheezing
• Chemical airway injury

High-level exposures may produce:

• Pulmonary inflammation
• Pulmonary edema

NIOSH recognizes the respiratory tract as a major target organ of chromic acid/chromates.

Occupational Asthma

Cr(VI) can function as a respiratory sensitizer.

Sensitized workers may develop:

• Wheezing
• Chest tightness
• Cough
• Occupational asthma

even after exposures lower than those producing obvious corrosive injury.

OSHA specifically identifies chromium-associated occupational asthma.

Nasal Septal Injury

A classic chronic occupational finding is:

Nasal irritation → ulceration → septal perforation

Symptoms may include:

• Epistaxis
• Nasal irritation
• Crusting
• Ulcers
• Septal perforation

This has historically been particularly associated with:

• Chrome plating
• Chromate production
• Welding

OSHA identifies repeated Cr(VI) exposure as capable of damaging nasal mucosa and causing septal perforation.

“Pneumoconiosis” – Important Correction

The old chapter emphasizes chromium-associated pneumoconiosis.

That is not the most useful modern description of chronic Cr(VI) respiratory disease.

The major recognized occupational pulmonary problems are:

• Chronic upper-airway irritation
• Nasal ulceration/perforation
• Occupational asthma
• Respiratory irritation
• Lung cancer

rather than a characteristic chromium-specific pneumoconiosis.

Skin Toxicity

Chrome ulcers

A classic Cr(VI) lesion is the:

“Chrome hole”

These are often:

• Painless
• Deep
• Punched-out ulcers

and occur particularly on:

• Fingers
• Hands
• Forearms

especially where skin is:

• Cut
• Abraded
• Chronically contaminated

Irritant Dermatitis

Direct exposure can cause:

• Erythema
• Burning
• Irritant contact dermatitis
• Chemical burns

Allergic Contact Dermatitis

Chromium is an important skin sensitizer.

After sensitization:

Very small subsequent exposures can provoke eczema.

OSHA recognizes both irritant and allergic chromium dermatitis, including disease associated with wet Portland cement.

Ocular Exposure

Cr(VI) solutions, dusts, or mists may cause:

• Conjunctivitis
• Severe irritation
• Corneal injury
• Chemical burns

Immediate irrigation is required.

Carcinogenicity

This is one of the most important chronic toxicology points.

Hexavalent chromium compounds are established human carcinogens.

IARC classifies:

• Cr(VI) compounds → Group 1, carcinogenic to humans
• Metallic chromium → Group 3
• Cr(III) compounds → Group 3

with sufficient human evidence particularly for occupationally associated lung cancer.

NIOSH similarly considers Cr(VI) compounds occupational carcinogens and recognizes increased lung-cancer risk in exposed workers.

Cancer Sites

The strongest human evidence is for:

Lung cancer

Occupational data also support concern for:

• Nasal cancer
• Sinonasal cancer

in heavily exposed populations.

Thus, the old statement that chromium “may” cause bronchogenic cancer understates the evidence specifically for Cr(VI).

Diagnosis

Diagnosis depends mainly on:

Exposure history + route + clinical syndrome

Important questions include:

• What chromium compound?
• Cr(VI) or Cr(III)?
• Chromate/dichromate?
• Concentration?
• Ingestion, inhalation, skin, or eye exposure?
• Occupational process?
• Duration/frequency?
• PPE?
• Other metals or chemicals present?

Obtaining the:

• Safety Data Sheet
• Product label
• Workplace exposure information

can be extremely helpful.

Acute Laboratory Evaluation

For significant Cr(VI) ingestion obtain:

• CBC
• Electrolytes
• Bicarbonate
• Glucose
• BUN
• Creatinine
• AST/ALT
• Bilirubin

For severe poisoning also obtain:

• Blood gas
• Lactate
• PT/INR
• aPTT
• Fibrinogen
• LDH
• Haptoglobin
• Reticulocyte count
• Urinalysis
• Type and crossmatch

Consider:

• Methemoglobin concentration

if cyanosis or unexplained hypoxia is present.

ECG

Obtain an ECG in significant systemic poisoning.

Continuous monitoring is appropriate with:

• Shock
• Major electrolyte abnormalities
• Severe acidosis
• Multiorgan failure

Chromium Measurements

Chromium concentrations may document exposure but have important limitations.

Blood / Serum

Chromium clears relatively rapidly from plasma.

Cr(VI) can enter erythrocytes and be reduced to Cr(III), becoming bound intracellularly.

Therefore:

• Serum chromium primarily reflects relatively recent exposure
• RBC chromium can support significant Cr(VI) exposure

ATSDR notes that Cr(VI), unlike Cr(III), enters red cells, so comparing erythrocyte and plasma/serum chromium may sometimes help characterize exposure.

Urinary Chromium

Urinary chromium largely reflects:

Recent absorption over roughly the preceding 1–2 days

and is used more often for occupational biomonitoring than for acute bedside decision-making.

Important

A chromium level is not a clinical severity score.

ATSDR notes that elevated chromium values have not been reliably correlated with specific physiologic effects.

Therefore:

Do not delay resuscitation or caustic-injury evaluation while waiting for chromium measurements.

Hair and Nail Testing

Hair or nail chromium testing is generally:

Not clinically useful

for diagnosing an individual exposure because external contamination cannot be reliably distinguished from incorporated chromium.

Acute GI Injury Assessment

A substantial Cr(VI) ingestion should be managed partly according to modern caustic-ingestion principles.

Consider:

• Gastroenterology
• Surgery
• Medical toxicology/poison center

early.

Endoscopy

For significant symptomatic or intentional Cr(VI) ingestion:

Early upper GI endoscopy is generally considered within approximately 12–24 hours, provided the patient is stable and perforation is not already apparent.

Endoscopy helps determine:

• Esophageal injury
• Gastric injury
• Burn severity
• Future stricture risk

Modern caustic literature generally recommends early endoscopic evaluation when clinically indicated.

CT

Contrast-enhanced CT of the:

• Neck
• Chest
• Abdomen

may be particularly useful in severe poisoning to assess:

• Transmural necrosis
• Perforation
• Mediastinal injury
• Peritoneal injury
• Adjacent structures

CT complements endoscopy rather than being replaced by routine broad CT/MRI scanning of the entire body.

Important Correction to the Old Imaging Advice

The older recommendation:

“CT or MRI from the nose to abdomen in the first few days because abscess develops late”

is not a standard contemporary chromium-poisoning protocol.

Imaging should be:

Targeted to the suspected complication.

Examples:

• CXR/CT chest → severe inhalational injury
• Contrast CT chest/abdomen → suspected deep GI necrosis/perforation
• ENT imaging/endoscopy → severe chronic nasal disease when clinically indicated

Treatment

1. Rescuer / Healthcare Worker Safety

For industrial contamination:

• Wear appropriate gloves
• Eye protection
• Protective clothing
• Respiratory protection if dust/mist remains airborne

Avoid secondary contamination from:

• Contaminated clothing
• Wet solutions
• Chromate dust

2. Airway and Breathing

For significant inhalation or major ingestion:

Assess:

• Airway edema
• Respiratory distress
• Oxygenation
• Ventilation

Provide:

• Oxygen for hypoxemia
• Bronchodilator for bronchospasm

Early intubation is appropriate for:

• Progressive airway edema
• Severe respiratory failure
• Coma
• Inability to manage secretions

3. Circulation

Severe dichromate poisoning may produce profound shock.

Treat with:

• IV isotonic crystalloid when clinically appropriate
• Blood products for major hemorrhage

If shock persists:

Norepinephrine is generally a reasonable contemporary first-line vasopressor.

Correct:

• Acidosis
• Electrolyte abnormalities
• Hypoglycemia

as clinically indicated.

Gastrointestinal Decontamination

Do not induce vomiting

Never induce emesis.

Cr(VI) salts can be intensely corrosive.

Vomiting:

• Re-exposes the esophagus
• Increases aspiration risk
• Can worsen hemorrhage

ATSDR specifically states that vomiting should not be induced because of Cr(VI)’s corrosive effects and risk of rapid clinical deterioration.

Routine Milk/Water Dilution

The older recommendation for routine milk/water dilution should not be carried forward.

Modern caustic-ingestion guidance finds little evidence for benefit, and dilution may produce:

• Vomiting
• Distention
• Aspiration

Thus:

Do not routinely force milk or water after significant Cr(VI) ingestion.

Do Not Neutralize

Do not attempt chemical neutralization with:

• Alkali
• Acid
• Household chemicals

Neutralization can cause an:

Exothermic reaction → additional thermal injury

Activated Charcoal

Routine activated charcoal is not established therapy for Cr(VI) ingestion.

Problems include:

• Caustic injury occurs rapidly
• Aspiration risk
• Vomiting
• Interference with endoscopic visualization
• Uncertain chromium adsorption benefit

Modern caustic guidance advises against routine charcoal for corrosives.

Gastric Lavage

Do not perform routine gastric lavage.

Potential harms include:

• Esophageal re-exposure
• Hemorrhage
• Perforation
• Aspiration

Modern corrosive-ingestion guidance considers lavage contraindicated.

Nasogastric Tubes

Avoid blind NG/OG placement through a severely injured esophagus.

If enteral access is required:

Use endoscopic/surgical guidance when feasible.

Dermal Decontamination

Immediately:

• Remove contaminated clothing
• Remove contaminated jewelry/PPE
• Wash exposed skin thoroughly with soap and water

NIOSH recommends immediate soap flushing after chromic acid/chromate skin contamination.

Do not aggressively scrub damaged skin.

Ascorbic Acid Skin Soaks – Historical Practice

Older toxicology references recommend:

10–20% ascorbic acid skin soaking

after Cr(VI) contamination.

Experimental and historical occupational evidence suggests extracellular reduction of Cr(VI) may reduce local toxicity, and ATSDR discusses older reports of 10% ascorbate reducing chromium dermatitis/ulceration.

However:

This is not a substitute for immediate copious decontamination and is not a routine modern emergency requirement.

Immediate:

• Clothing removal
• Soap/water washing

remains the priority.

Eye Exposure

Immediately:

Irrigate copiously

with:

• Water
• Saline

for at least 15–20 minutes and longer if needed.

Remove contact lenses when possible.

Persistent:

• Pain
• Photophobia
• Corneal injury
• Visual disturbance

requires urgent ophthalmologic evaluation.

NIOSH recommends immediate irrigation after eye exposure.

Ascorbic Acid as an “Antidote”

This is one of the biggest updates to the old chapter.

The theoretical reaction is:

Cr(VI) + reducing agent → Cr(III)

which should reduce membrane penetration if it occurs before cellular uptake.

This is the rationale for vitamin C.

However:

There is no established human clinical evidence supporting a standardized ascorbic-acid antidote regimen for acute Cr(VI) poisoning.

ATSDR specifically states that although extracellular reduction may theoretically protect, human efficacy of ascorbate or other reducing agents has not been established, and intracellular ascorbate can have complex effects on Cr(VI) toxicity.

Therefore the old formula:

“1 g vitamin C per 0.135 g elemental chromium”

should not be used as an established modern antidote protocol.

Practical approach

For a very recent major soluble Cr(VI) exposure:

Discuss any proposed ascorbate therapy with a medical toxicologist/poison center.

It must not delay:

• Resuscitation
• Airway management
• Caustic injury assessment
• Treatment of shock

Dimercaprol (BAL)

The old chapter states:

“Dimercaprol has been used successfully.”

Modern interpretation is different.

BAL is not an established effective antidote for chromium poisoning.

ATSDR states that chelating agents such as:

• Dimercaprol
• EDTA

have not been shown effective in human chromium poisoning.

Therefore:

Routine BAL should not be used.

EDTA and Other Chelators

Similarly:

• CaNa₂EDTA
• Other experimental chelators

do not have an established clinical role.

A toxicokinetic potassium-dichromate case found Ca-EDTA did not meaningfully alter serum, RBC, or urinary chromium kinetics.

Chelation should therefore not be routine therapy.

Hemodialysis

Toxin removal

Chromium rapidly enters cells and binds intracellularly.

Consequently:

Conventional hemodialysis does not reliably remove enough chromium to function as an effective antidotal therapy.

In one detailed case, combined urinary and dialysis elimination represented only about:

0.16% of the ingested chromium dose

despite prompt dialysis.

Other severe cases similarly found little clinically meaningful chromium removal by:

• Hemodialysis
• Hemoperfusion
• Exchange transfusion.

When Dialysis IS Appropriate

Hemodialysis remains appropriate for conventional renal indications such as:

• Refractory metabolic acidosis
• Severe hyperkalemia
• Volume overload
• Uremic complications
• Severe AKI

Thus:

Dialysis treats the renal/metabolic consequences—not reliably the chromium body burden.

ATSDR likewise states that hemodialysis has not been shown effective as a specific chromium-removal treatment.

Hemoperfusion / Exchange Transfusion

These are not routine therapies.

Historical reports failed to demonstrate reliable clinical benefit or meaningful removal of the largely intracellular chromium burden.

GI Hemorrhage

Treat severe bleeding with:

• Large-bore IV access
• Type/crossmatch
• Packed RBCs
• Appropriate plasma/platelets when indicated

Early:

• Gastroenterology
• Surgery

involvement is appropriate.

Perforation / Transmural Necrosis

Suspect perforation with:

• Severe worsening abdominal/chest pain
• Peritoneal signs
• Pneumomediastinum
• Free intraperitoneal air
• Sepsis
• Shock
• Rising lactate/acidosis

This requires:

Immediate surgical evaluation.

Nutrition

Significant Grade IIb/III caustic injury may require:

• Temporarily restricted oral intake
• Carefully planned enteral feeding
• Postpyloric feeding
• Occasionally parenteral nutrition

The old automatic recommendation for parenteral nutrition after severe injury is overly broad.

Modern practice favors:

Enteral nutrition whenever it can be delivered safely.

Antibiotics

Routine prophylactic antibiotics are not indicated merely because chromium was ingested.

Use antibiotics for:

• Perforation
• Mediastinitis
• Peritonitis
• Aspiration pneumonia
• Documented infection

Corticosteroids

There is no established role for corticosteroids to treat systemic chromium poisoning.

For caustic esophageal injury, routine systemic steroids are also not reliably proven to prevent strictures.

Their use should therefore not be automatic.

Inhalational Exposure – Treatment

Remove from exposure.

Provide:

• Fresh air
• Oxygen if hypoxemic
• Inhaled β₂ agonist for bronchospasm

Severe respiratory injury may require:

• Noninvasive support in selected cases
• Intubation
• Lung-protective ventilation

For sensitization/occupational asthma:

Removal from continued chromium exposure is critical.

Chronic Dermatitis / Chrome Ulcers

Management includes:

• Eliminate ongoing exposure
• Local wound care
• Treat secondary infection only when present
• Occupational-health evaluation

Allergic dermatitis may require:

• Topical anti-inflammatory therapy
• Dermatology/occupational medicine assessment
• Avoidance of further chromium exposure

Repeated exposure after sensitization may provoke dermatitis at very low concentrations.

Nasal Disease

Workers with:

• Recurrent epistaxis
• Nasal ulceration
• Persistent crusting
• Septal damage

need:

• Removal/reduction of exposure
• Occupational medicine evaluation
• ENT assessment when clinically indicated

The old recommendation to wash the nose daily and routinely apply zinc/barium ointment is not a modern standard treatment strategy.

Exposure control is far more important.

Occupational Cancer Prevention

Because Cr(VI) is a carcinogen:

Engineering controls and exposure prevention are the central long-term intervention.

Important measures include:

• Local exhaust ventilation
• Process enclosure
• Substitution when feasible
• Appropriate respiratory protection
• Skin protection
• Hygiene facilities
• Exposure monitoring
• Occupational medical surveillance

Current Workplace Standards – Cr(VI)

The workplace limits in the old chapter are substantially outdated.

OSHA

Current federal OSHA Cr(VI) standard:

PEL = 5 μg/m³ as an 8-hour TWA

and:

Action level = 2.5 μg/m³ as an 8-hour TWA

This equals:

0.005 mg/m³

not the old 0.25 mg/m³ value.

NIOSH

Current NIOSH recommended exposure limit:

0.2 μg/m³ = 0.0002 mg/m³ as Cr(VI), 8-hour TWA

NIOSH treats Cr(VI) as an occupational carcinogen.

This is 25-fold lower than the OSHA PEL.

ACGIH

Current OSHA chemical-data listings cite an ACGIH value of:

0.0002 mg/m³ inhalable particulate TWA

with:

0.0005 mg/m³ STEL

for Cr(VI).

NIOSH IDLH

For chromic acid/chromates:

IDLH = 15 mg/m³ as Cr(VI)

Do Not Apply Cr(VI) Limits to All Chromium

Occupational limits differ by oxidation state.

For example, NIOSH lists much higher limits for:

• Chromium metal
• Cr(II)
• Cr(III)

reflecting their markedly different toxicology.

Therefore:

Always specify the chromium species when discussing occupational exposure.

Occupational Biomonitoring

Urinary chromium can help assess recent occupational uptake.

However:

• It varies between individuals
• It reflects mainly recent exposure
• It does not directly predict disease
• It may normalize despite a clinically important past exposure

ATSDR emphasizes these limitations and notes that urinary chromium primarily represents absorption within the previous 1–2 days.

Occupational monitoring is best interpreted with:

• Air measurements
• Job/task assessment
• PPE evaluation
• Clinical findings

rather than in isolation.

Admission

ICU admission

ICU-level management is appropriate after significant Cr(VI) ingestion with:

• Severe GI burns
• GI hemorrhage
• Hypotension/shock
• Severe metabolic acidosis
• AKI
• Hepatic injury
• Coagulopathy
• Altered mental status
• Respiratory failure
• Multiorgan dysfunction

Hospital Admission

Admission is generally appropriate for:

• Any clearly significant soluble Cr(VI) ingestion
• Persistent vomiting/diarrhea
• Dysphagia/odynophagia
• Abdominal or chest pain
• Hematemesis
• Renal abnormalities
• Hepatic abnormalities
• Significant inhalational injury

A deliberate Cr(VI) ingestion should not be discharged merely because initial vital signs are normal.

Disposition After Minor Exposure

A truly trivial exposure to:

• Metallic chromium
• Low-risk Cr(III) material

may require only decontamination and assessment.

However:

Known ingestion of soluble Cr(VI) deserves a low threshold for prolonged medical evaluation

because systemic renal/hepatic injury can evolve after the initial corrosive symptoms.

Prognosis

Minor local exposure

Usually favorable after adequate decontamination.

Chronic occupational exposure

Can result in:

• Persistent sensitization
• Chronic dermatitis
• Nasal septal damage
• Occupational asthma
• Increased cancer risk

Severe Cr(VI) ingestion

Can produce:

• Massive GI hemorrhage
• AKI
• Hepatic failure
• Coagulopathy
• Shock
• Multiorgan failure
• Death

Case reports demonstrate that deterioration may be rapid despite aggressive therapy.

Long-Term GI Follow-Up

Patients with significant caustic esophageal injury are at risk for:

• Esophageal stricture
• Dysphagia
• Gastric outlet obstruction

Grade IIb/III caustic injuries require gastroenterology follow-up.

Later progressive dysphagia warrants:

• Contrast evaluation
• Endoscopy

as appropriate.

Pregnancy

There is no chromium-specific antidotal therapy that should supersede maternal resuscitation.

After severe exposure:

Maternal airway, oxygenation, circulation, renal function, and caustic injury management are priorities.

Occupational Cr(VI) exposure during pregnancy should be minimized according to exposure-control standards.

Important Pitfalls

1. Treating all chromium as equally toxic

This is the fundamental error.

Cr(VI) ≫ Cr(III) in toxicologic importance.

2. Calling Cr(VI) merely a “heavy-metal poisoning”

Acute soluble Cr(VI) ingestion is also:

A severe corrosive ingestion

with potentially catastrophic local GI injury.

3. Using the old fixed lethal dose

The old:

0.5–1 g = lethal

rule is unreliable.

Risk depends on compound, dose, concentration, and clinical findings.

4. Missing systemic toxicity after the initial GI burn

After vomiting/abdominal pain, monitor for:

AKI + hepatic injury + coagulopathy + shock

5. Calling chromium pneumoconiosis the dominant chronic lung disease

The major chronic Cr(VI) respiratory hazards are:

• Nasal injury
• Asthma
• Respiratory irritation
• Lung cancer

6. Underestimating cancer risk

Cr(VI) compounds are IARC Group 1 human carcinogens.

7. Assuming Cr(III) and metallic chromium have the same carcinogenic classification

IARC classification:

• Cr(VI) → Group 1
• Cr(III) → Group 3
• Metallic chromium → Group 3

8. Inducing vomiting

Cr(VI) salts are corrosive.

Do not induce emesis.

ATSDR specifically advises against it.

9. Routinely diluting with milk/water

Modern caustic management does not support forced dilution because clinical benefit is unproven.

10. Giving activated charcoal routinely

Chromium-associated caustic injury is not a standard charcoal indication.

Airway safety and endoscopic visualization matter more.

11. Performing gastric lavage

Routine lavage is contraindicated.

It can provoke:

• Hemorrhage
• Re-exposure
• Aspiration
• Perforation

12. Treating vitamin C as a proven antidote

Reduction of extracellular Cr(VI) to Cr(III) is mechanistically attractive.

But:

Human efficacy and dosing are not established.

13. Using the old fixed vitamin-C formula

The historical:

1 g vitamin C per 0.135 g chromium

regimen is not an evidence-based modern standard.

14. Routinely giving BAL

Dimercaprol has not been shown effective in human chromium poisoning.

15. Assuming EDTA works because chromium is a metal

CaNa₂EDTA does not have an established therapeutic role.

Chromium toxicity should not be managed by automatically applying lead-poisoning chelation protocols.

16. Using dialysis as a chromium antidote

Chromium rapidly becomes intracellular.

Hemodialysis may remove only a tiny fraction of a major dose.

Use dialysis for:

AKI/metabolic indications

rather than expecting reliable toxin clearance.

17. Relying on chromium blood/urine levels to grade severity

They can confirm recent exposure but correlate poorly with clinical effects.

Treat the patient, not the chromium number.

18. Using hair chromium analysis

Hair/nail testing is easily confounded by external contamination and is generally not clinically useful for individual diagnosis.

19. Using the old occupational PEL

Old chapter:

~0.25 mg/m³

Modern OSHA Cr(VI) PEL:

0.005 mg/m³ = 5 μg/m³

High-Yield Toxicology Pearls

Chromium toxicology = always ask which valence state

Think:

Cr(VI) = corrosive + systemic poison + occupational carcinogen

Key points:

• Important forms:
• Chromium metal
• Cr(III)
• Cr(VI)
• Cr(VI) is much more toxic than Cr(III)
• Important Cr(VI) compounds:
• Chromic acid
• Chromium trioxide
• Potassium dichromate
• Sodium dichromate
• Chromates
• Mechanism:
• Cr(VI) resembles sulfate/phosphate
• Enters cells via anion transporters
• Intracellular reduction → Cr(V)/Cr(IV)/Cr(III) + ROS
• DNA/protein injury
• Acute ingestion:
• Caustic GI burns
• Vomiting/diarrhea
• GI hemorrhage
• Shock
• AKI
• Hepatic injury
• Coagulopathy
• Multiorgan failure
• Skin:
• Chrome holes
• Irritant dermatitis
• Allergic contact dermatitis
• Respiratory:
• Nasal irritation
• Septal ulceration/perforation
• Occupational asthma
• Cancer:
• Cr(VI) = IARC Group 1
• Strong association with lung cancer
• Cr(III) and metallic chromium:
• IARC Group 3
• Diagnosis is primarily:
• Exposure history
• Clinical syndrome
• Blood/urine chromium:
• Can document recent exposure
• Do not reliably grade toxicity
• Urinary chromium mainly reflects exposure over the previous 1–2 days
• Significant Cr(VI) ingestion → evaluate as caustic ingestion
• Endoscopy generally within ~12–24 h when indicated
• Contrast CT helps evaluate deep/transmural injury
• Do not induce vomiting
• Do not neutralize
• Routine milk/water dilution is not recommended
• Routine activated charcoal is not established
• Gastric lavage is contraindicated/not routine
• Skin:
• Remove clothing
• Immediate soap-and-water decontamination
• Eyes:
• Immediate copious irrigation
• No proven antidote
• Vitamin C:
• Mechanistically reduces Cr(VI) → Cr(III)
• Human therapeutic benefit is unproven
• Old fixed-dose protocol should not be used routinely
• BAL:
• Not recommended routinely
• EDTA:
• No established role
• Hemodialysis:
• Poor chromium removal after intracellular uptake
• Use for standard AKI/metabolic indications
• Modern occupational Cr(VI) limits:
• OSHA PEL: 5 μg/m³ 8-h TWA
• OSHA action level: 2.5 μg/m³
• NIOSH REL: 0.2 μg/m³ 8-h TWA
• NIOSH IDLH: 15 mg/m³ as Cr(VI)
• Prevention and occupational exposure control are central because chronic Cr(VI) exposure is carcinogenic

Toxicology – Cholinergic Agonist Medications

Core concept

Direct cholinergic agonists produce toxicity by stimulating acetylcholine receptors directly rather than by inhibiting acetylcholinesterase.

The characteristic syndrome is predominantly:

Muscarinic receptor stimulation → salivation + lacrimation + diaphoresis + vomiting/diarrhea + miosis + bradycardia + bronchospasm/bronchorrhea

The most important severe manifestations are:

Bronchospasm/bronchial secretions + bradycardia/hypotension → respiratory and cardiovascular compromise

The principal antidote is:

Atropine

A crucial distinction from organophosphate poisoning is:

Pralidoxime has no mechanistic role in an isolated direct cholinergic agonist overdose

because acetylcholinesterase has not been inhibited.

Classification

Cholinergic drugs are divided into:

1. Direct-acting cholinergic agonists

These drugs bind directly to cholinergic receptors.

Important examples include:

Choline esters

• Acetylcholine
• Bethanechol
• Carbachol
• Methacholine

Alkaloid/direct muscarinic agonists

• Pilocarpine
• Cevimeline
• Muscarine
• Arecoline

Current reviews classify acetylcholine, methacholine, carbachol, bethanechol, pilocarpine, muscarine, and cevimeline as direct-acting parasympathomimetics.

2. Indirect cholinergic agonists

These increase acetylcholine by inhibiting acetylcholinesterase.

Examples include:

• Neostigmine
• Pyridostigmine
• Physostigmine
• Donepezil
• Rivastigmine
• Organophosphates
• Carbamate insecticides
• Nerve agents

These are different toxicologic entities, particularly because oximes such as pralidoxime act on inhibited AChE and therefore apply principally to selected anticholinesterase poisonings, not direct receptor agonists.

Important Current Agents

Acetylcholine

Current U.S. MIOCHOL-E contains acetylcholine chloride for:

Intraocular use to produce rapid miosis during ophthalmic surgery.

Acetylcholine is rapidly hydrolyzed by cholinesterases, so systemic toxicity from correct intraocular use is unusual.

It activates both:

• Muscarinic receptors
• Nicotinic receptors

but has an extremely short duration.

Bethanechol

Bethanechol is primarily a:

Muscarinic receptor agonist

It is relatively resistant to acetylcholinesterase and has little clinically important nicotinic action.

Current oral dosing remains approximately:

10–50 mg three or four times daily

for selected urinary-retention indications.

Typical adverse/toxic effects include:

• Salivation
• Sweating
• Flushing
• Abdominal cramping
• Diarrhea
• Urinary urgency
• Miosis
• Bronchoconstriction
• Hypotension

Current labeling explicitly identifies atropine as the antidote for bethanechol overdose.

Carbachol

Carbachol is distinctive because it has:

Both muscarinic and nicotinic cholinergic agonist activity

Current MIOSTAT 0.01% is used intraocularly to:

• Produce miosis during surgery
• Reduce early postoperative intraocular-pressure elevation after cataract surgery.

2026 update

A new ophthalmic combination:

YUVEZZI — carbachol 2.75% + brimonidine 0.1%

received U.S. approval in 2026 for treatment of:

Presbyopia in adults.

Therefore the older view of carbachol solely as an intraoperative/glaucoma medication is incomplete.

Methacholine

Methacholine is primarily a:

Muscarinic agonist

and the old description grouping methacholine with strongly nicotinic drugs is misleading.

Current PROVOCHOLINE is used for:

Methacholine bronchial-challenge testing

to diagnose airway hyperresponsiveness in adults and children ≥5 years without clinically apparent asthma.

It is deliberately administered to provoke:

M3 receptor activation → bronchial smooth-muscle contraction → bronchoconstriction

Current labeling carries a boxed warning for:

Severe bronchoconstriction

even at low doses.

It is contraindicated when baseline:

• FEV₁ <60% predicted
• or
• Adult FEV₁ <1.5 L.

Severe methacholine-induced bronchospasm should be reversed promptly with a:

Rapid-acting inhaled β₂ agonist

such as albuterol/salbutamol.

Pilocarpine

Pilocarpine is predominantly a:

Direct muscarinic agonist

Current systemic oral pilocarpine is indicated for:

• Xerostomia following radiotherapy for head/neck cancer
• Xerostomia associated with Sjögren syndrome.

Ophthalmic pilocarpine remains used in selected ophthalmologic settings.

Systemic effects can include:

• Profuse sweating
• Salivation
• Nausea
• Diarrhea
• Urinary frequency
• Bradycardia
• Hypotension
• Bronchospasm

Current labeling notes historical fatal overdoses at doses presumed to exceed approximately:

100 mg

and regards 100 mg as potentially fatal, although this should not be interpreted as a precise clinical threshold.

Cevimeline

Cevimeline should be added to the modern list.

It is a direct muscarinic agonist currently used for:

Dry mouth in Sjögren syndrome.

It can cause:

• Sweating
• Salivation
• Nausea
• Bronchoconstriction
• Bradycardia/hemodynamic changes

Current labeling warns that it may:

• Increase airway resistance
• Increase bronchial smooth-muscle tone
• Increase bronchial secretions

and it is contraindicated in uncontrolled asthma.

Natural Cholinergic Agonists

The older source mixes several natural products together; these require correction.

Pilocarpus

Pilocarpus plants contain pilocarpine, not arecoline.

Areca Nut

The seed of:

Areca catechu

contains:

Arecoline

Arecoline is predominantly a muscarinic partial agonist but also has activity at selected nicotinic acetylcholine receptors.

Acute areca-nut exposure can produce:

• Salivation
• Sweating
• GI hyperactivity
• Tachycardia or bradycardia
• Tremor
• CNS stimulation

Important terminology correction

“Betel quid” commonly contains:

• Areca nut
• Betel leaf
• Lime
• Sometimes tobacco

The principal source of arecoline is the areca nut, not the Piper betle leaf itself.

Muscarine-Containing Mushrooms

Muscarinic mushroom poisoning is classically associated with:

• Inocybe
• Clitocybe

species.

The older inclusion of Boletus as a principal muscarine-containing genus is not appropriate for the classic muscarinic mushroom syndrome.

Symptoms usually begin rapidly—often within:

30 minutes to 2 hours

and include:

• Salivation
• Lacrimation
• Diaphoresis
• Miosis
• Vomiting/diarrhea
• Bronchospasm
• Bradycardia/hypotension

Atropine produces rapid improvement when muscarinic symptoms are clinically significant.

Pathophysiology

Muscarinic receptors

Five muscarinic receptor subtypes exist:

M1–M5

The most clinically important toxic effects involve:

M2 — heart

Activation causes:

• Reduced SA-node firing
• Reduced AV conduction
• Bradycardia

M3 — glands/smooth muscle

Activation causes:

• Salivation
• Lacrimation
• Sweating
• Bronchoconstriction
• Bronchial secretion
• GI hypermotility
• Bladder contraction
• Miosis

Thus:

M3 activation → wet patient

while:

M2 activation → slow heart

Nicotinic Receptors

Nicotinic receptor stimulation may cause:

• Ganglionic autonomic activation
• Tachycardia
• Hypertension
• Skeletal-muscle fasciculations
• Weakness

However:

Pronounced nicotinic neuromuscular toxicity is much more characteristic of anticholinesterase poisoning than of most therapeutic direct muscarinic agonists.

Carbachol has meaningful nicotinic activity.

Arecoline also has some nicotinic activity.

By contrast:

• Bethanechol → predominantly muscarinic
• Methacholine → predominantly muscarinic
• Pilocarpine → predominantly muscarinic

Therefore the old chapter overstates expected nicotinic toxicity from methacholine.

Clinical Syndrome

A useful mnemonic remains:

DUMBELS

• D — Diarrhea / diaphoresis
• U — Urination
• M — Miosis
• B — Bradycardia / bronchospasm / bronchorrhea
• E — Emesis
• L — Lacrimation
• S — Salivation

Another practical approach is:

Wet + wheezy + slow

HEENT

Possible findings:

• Miosis
• Blurred vision
• Lacrimation
• Salivation
• Rhinorrhea

Ophthalmic exposure may produce:

• Ciliary spasm
• Brow ache/headache
• Miosis
• Blurred vision
• Reduced night vision

Dermatologic

Muscarinic stimulation of eccrine sweat glands causes:

Profuse diaphoresis

The patient may therefore be:

• Wet
• Cool
• Clammy

rather than dry as in an anticholinergic toxidrome.

Cardiovascular

Possible findings include:

• Bradycardia
• Hypotension
• AV block
• Reduced cardiac output

Low-dose vasodilatory effects may sometimes produce:

Hypotension → reflex tachycardia

so tachycardia does not absolutely exclude a muscarinic drug exposure.

Pilocarpine and cevimeline labeling both warn that cholinergic effects may alter heart rate and hemodynamics, particularly in patients with underlying cardiovascular disease.

Respiratory

The most immediately dangerous manifestations are:

Bronchospasm + increased bronchial secretions

Patients may develop:

• Cough
• Wheezing
• Chest tightness
• Dyspnea
• Hypoxemia

Patients with:

• Asthma
• COPD
• Other obstructive lung disease

are at higher risk.

Pilocarpine can increase airway resistance, bronchial tone, and secretions.

Methacholine is deliberately bronchoconstrictive and can cause severe bronchospasm even during properly conducted diagnostic testing.

Gastrointestinal

Typical findings:

• Nausea
• Vomiting
• Abdominal cramping
• Borborygmi
• Diarrhea

Severe vomiting/diarrhea can produce:

• Volume depletion
• Electrolyte abnormalities

Genitourinary

Muscarinic stimulation can cause:

• Urinary urgency
• Increased bladder contraction
• Incontinence

Bethanechol’s therapeutic effect itself depends on increasing detrusor activity.

Neurologic

Most direct peripheral muscarinic agonists produce less dramatic CNS toxicity than organophosphate poisoning.

Possible manifestations include:

• Headache
• Dizziness
• Tremor
• Confusion

Seizures and coma are uncommon in isolated routine direct-agonist overdose and should prompt consideration of:

• Massive exposure
• Hypoxia
• Coingestant
• Alternative diagnosis
• Anticholinesterase poisoning

The older chapter likely overstates seizure/coma as routine manifestations of this medication class.

Neuromuscular Findings

Significant:

• Fasciculations
• Generalized weakness
• Flaccid paralysis

should raise suspicion for:

Organophosphate/carbamate anticholinesterase poisoning

rather than a straightforward bethanechol or pilocarpine overdose.

Carbachol and arecoline can have some nicotinic effects, but profound neuromuscular paralysis is not the usual syndrome of therapeutic direct muscarinic agonists.

Toxic Dose

There is no useful class-wide statement that:

“Two or three times the daily dose is toxic.”

The agents vary greatly in:

• Potency
• Route
• Absorption
• Duration
• Receptor selectivity

For example:

• Methacholine is inhaled in tightly controlled diagnostic doses
• Acetylcholine is predominantly intraocular
• Pilocarpine is orally systemically active
• Carbachol is commonly ophthalmic/intraocular
• Bethanechol is oral
• Cevimeline is oral

Therefore:

Risk assessment must be agent-specific.

Diagnosis

Diagnosis is primarily clinical:

Known direct cholinergic exposure + predominantly muscarinic toxidrome

Look for:

Salivation + diaphoresis + GI hyperactivity + miosis + bronchospasm ± bradycardia

Cholinesterase Levels

This is an important distinction from pesticide poisoning.

RBC acetylcholinesterase and plasma butyrylcholinesterase levels are not useful for direct cholinergic agonist poisoning.

These drugs stimulate receptors directly.

They do not require inhibition of acetylcholinesterase.

Therefore:

Normal cholinesterase activity is expected and does not argue against direct muscarinic-agonist toxicity.

Laboratory Testing

Mild toxicity

No routine laboratory testing may be necessary.

Moderate/severe toxicity

Consider:

• Glucose
• Electrolytes
• Bicarbonate
• BUN
• Creatinine

For significant vomiting/diarrhea:

• Potassium
• Magnesium

For severe respiratory illness:

• Blood gas
• Lactate

For repeated seizures/prolonged immobilization:

• CK

ECG

Obtain an ECG and cardiac monitoring for:

• Bradycardia
• Syncope
• Hypotension
• Significant systemic overdose
• Cardiovascular symptoms

Possible abnormalities include:

• Sinus bradycardia
• AV block
• Reflex tachycardia

Respiratory Assessment

Patients with:

• Wheezing
• Dyspnea
• Bronchospasm

should have:

• Pulse oximetry
• Serial lung examination

Peak flow/spirometry may be helpful in selected cooperative patients.

Chest radiography is not routine but may be appropriate with:

• Persistent hypoxemia
• Aspiration
• Suspected pulmonary edema
• Alternative pulmonary diagnosis

Differential Diagnosis

Most important toxicologic differential

Organophosphate poisoning

Produces:

• Muscarinic excess
• Nicotinic weakness/fasciculations
• CNS effects

and typically causes cholinesterase inhibition.

Carbamate insecticides

Also inhibit acetylcholinesterase, usually reversibly.

Therapeutic AChE inhibitors

Examples:

• Donepezil
• Rivastigmine
• Galantamine
• Neostigmine
• Pyridostigmine

Muscarinic mushrooms

Especially:

• Inocybe
• Clitocybe

Nicotine

May produce a mixed:

• Cholinergic
• Adrenergic
• Neuromuscular

syndrome.

Treatment

1. Airway and breathing

Assess immediately:

• Ability to handle secretions
• Bronchospasm
• Work of breathing
• Oxygenation
• Ventilation

Provide:

• Suction
• Oxygen when indicated
• Assisted ventilation if necessary

Intubate for:

• Severe respiratory failure
• Inability to protect airway
• Refractory bronchospasm with fatigue
• Severe CNS depression

2. Atropine

Atropine is the specific pharmacologic antagonist for dangerous muscarinic toxicity.

It competitively blocks muscarinic receptors.

Atropine improves:

• Bronchial secretions
• Bronchospasm
• Salivation
• Bradycardia
• Muscarinic hypotension
• GI hyperactivity

It does not directly reverse nicotinic skeletal-muscle weakness.

Current references specifically recommend parenteral atropine for overdose of direct parasympathomimetic drugs.

Atropine Dosing

Direct muscarinic-agonist poisonings often require much less atropine than severe organophosphate poisoning.

Current product labeling provides examples:

Pilocarpine overdose

Atropine 0.5–1 mg IV or SC, titrated to clinical response.

Bethanechol overdose

Current labeling recommends approximately:

0.6 mg atropine in adults

with repeat dosing according to response.

In severe poisoning

When clinically important:

• Bronchorrhea
• Bronchospasm
• Bradycardia
• Hypotension

persist, IV atropine should be repeated and titrated clinically rather than limited by an arbitrary maximum dose.

Atropine Endpoint

Treat the dangerous physiology rather than the pupils.

The most useful endpoints are:

Adequate ventilation + controlled bronchial secretions + improvement in bronchospasm + adequate perfusion

Do not continue atropine simply to produce:

• Complete mouth dryness
• Mydriasis
• A particular heart rate

Avoid Over-Atropinization

Because most direct agonist overdoses are shorter and milder than organophosphate poisoning, excessive atropine can easily produce an anticholinergic toxidrome:

• Tachycardia
• Dry flushed skin
• Hyperthermia
• Urinary retention
• Ileus
• Agitation
• Delirium

Thus:

Use enough atropine to control dangerous muscarinic effects—not automatically massive organophosphate-style doses in every patient.

Pralidoxime (2-PAM)

Pralidoxime is NOT indicated for an isolated direct cholinergic agonist overdose.

Mechanism:

Pralidoxime → reactivates inhibited acetylcholinesterase

But with:

• Bethanechol
• Pilocarpine
• Methacholine
• Carbachol
• Cevimeline

there may be no inhibited enzyme to reactivate.

Therefore:

Direct agonist → atropine

not:

Direct agonist → atropine + pralidoxime

When Pralidoxime May Still Be Appropriate

If the exposure is unclear and the patient could instead have:

• Organophosphate poisoning
• Mixed pesticide exposure
• Nerve-agent exposure

then manage according to the suspected anticholinesterase syndrome, which may include pralidoxime.

Methacholine-Specific Bronchospasm

If severe bronchoconstriction follows methacholine challenge:

Give a rapid-acting inhaled β₂ agonist immediately

such as:

• Albuterol
• Salbutamol

This is specifically required by current Provocholine labeling.

Atropine may be appropriate if there are broader systemic muscarinic manifestations, but inhaled β₂ agonist treatment is central to reversing methacholine-provoked bronchoconstriction.

Bronchospasm From Other Muscarinic Agonists

Treat with:

• Atropine
• Inhaled β₂ agonist as an adjunct

Oxygen and ventilatory support are added according to severity.

Do not rely on albuterol alone if marked:

• Secretions
• Bradycardia
• Generalized cholinergic toxicity

are present.

Hypotension

First assess whether hypotension reflects:

• Muscarinic bradycardia
• Vasodilation
• Volume depletion from vomiting/diarrhea

Initial therapy

• Atropine when bradycardia/cholinergic excess is contributing
• Isotonic crystalloid if volume responsive

If persistent shock remains:

Norepinephrine is generally an appropriate contemporary vasopressor.

The historical use of Trendelenburg positioning as therapy is obsolete.

Seizures

Although uncommon with isolated therapeutic direct agonists, toxin-induced seizures should be treated with:

Benzodiazepines first-line

Examples:

• Midazolam
• Lorazepam
• Diazepam

For refractory seizures:

• Phenobarbital
• Propofol in an intubated patient

Also correct:

• Hypoxia
• Hypoglycemia
• Electrolyte abnormalities

Gastrointestinal Decontamination

Do not induce vomiting

No ipecac or induced emesis.

Spontaneous vomiting and respiratory secretions increase aspiration risk.

Activated Charcoal

Activated charcoal is not routinely necessary for every direct cholinergic drug exposure.

A single dose may be considered after a:

• Recent
• Clinically significant
• Oral ingestion

if:

• The airway is intact/protected
• Vomiting is not severe
• Aspiration risk is acceptable

Airway and respiratory treatment always take priority.

Gastric Lavage

The older recommendation for routine gastric lavage after a significant ingestion is outdated.

Routine gastric lavage is not recommended.

Only an extraordinary:

• Immediately life-threatening
• Very recent

ingestion could justify considering lavage after:

• Airway protection
• Specialist toxicology consultation

Eye / Skin Exposure

For significant inadvertent topical exposure:

• Remove contaminated clothing
• Wash skin with soap and water

For inappropriate ocular exposure to a non-ophthalmic preparation:

• Irrigate with water/saline
• Evaluate persistent ocular symptoms

Therapeutic miotic eye drops themselves are not managed by simply “washing them out” once absorbed; treatment is symptom directed.

Succinylcholine – Important Distinction

Anticholinesterase poisoning can prolong succinylcholine paralysis because cholinesterase activity is inhibited.

However:

An isolated direct receptor agonist does not inhibit cholinesterase.

Therefore the blanket warning to avoid succinylcholine in every “cholinergic” drug poisoning does not automatically apply to a confirmed direct muscarinic agonist exposure.

If organophosphate/carbamate poisoning is possible, a nondepolarizing paralytic such as rocuronium remains preferable.

Enhanced Elimination

There is no established routine role for:

• Hemodialysis
• Hemoperfusion
• Urinary alkalinization
• Forced diuresis

for typical direct cholinergic agonist medication poisoning.

Pilocarpine labeling specifically states that whether it is dialyzable is unknown.

Supportive care and atropine are generally sufficient.

Monitoring

Symptomatic patients should have:

• Respiratory monitoring
• Pulse oximetry
• Frequent lung examinations
• Blood-pressure monitoring

Continuous ECG monitoring is appropriate with:

• Bradycardia
• Hypotension
• Syncope
• Significant systemic poisoning

Reassess:

• Secretions
• Wheezing
• Heart rate
• Blood pressure
• Mental status

after every atropine dose.

Observation

The old statement that toxicity routinely:

“peaks within 6–12 hours and may take days to recover”

is too broad for this diverse class.

Duration depends heavily on the agent.

For example:

• Acetylcholine has extremely brief activity
• Methacholine challenge effects are generally short and actively reversed
• Bethanechol commonly acts for several hours or less
• Oral pilocarpine/cevimeline can produce more sustained systemic effects
• Natural-product ingestion may have a different time course

Therefore:

Observation should be agent- and symptom-specific rather than a fixed 4–6-hour rule.

Admission

Hospital admission is appropriate for:

• Clinically important bronchospasm
• Persistent bronchial secretions
• Recurrent atropine requirement
• Significant bradycardia
• Hypotension
• AV block/dysrhythmia
• Hypoxemia
• Severe vomiting/diarrhea with dehydration
• Altered mental status
• Seizure

ICU-level care is appropriate for:

• Respiratory failure
• Intubation
• Severe bronchospasm
• Hemodynamic instability
• Recurrent serious dysrhythmia

Not every mildly symptomatic patient requires ICU admission, contrary to the older recommendation.

Discharge

Patients may be discharged when:

• Symptoms have fully resolved
• Oxygenation is normal
• No clinically important bronchospasm remains
• Heart rate/BP are stable
• No recurrent atropine is required
• Oral intake is tolerated when appropriate
• The expected duration of the specific agent has been considered

Intentional overdose also requires appropriate psychiatric/safety assessment.

Pregnancy

The historical FDA Pregnancy Category C system is obsolete.

Pregnancy safety data vary considerably between individual drugs.

For acute poisoning:

Maternal airway, oxygenation, and circulation take priority.

Atropine should not be withheld when needed to treat life-threatening muscarinic toxicity.

The potential maternal and fetal consequences of:

• Severe bronchospasm
• Hypoxia
• Bradycardia
• Hypotension

are more immediately dangerous than appropriate antidotal atropine therapy.

Prognosis

Most isolated direct cholinergic medication exposures have:

Good prognosis with prompt supportive care and atropine when required.

Severe morbidity is more likely when:

• Bronchospasm is not recognized
• Excess secretions compromise ventilation
• Profound bradycardia/hypotension develops
• Exposure is massive
• Coingestants are present

Direct agonist medication poisoning generally resolves faster than severe organophosphate poisoning because there is no persistent AChE phosphorylation or aging process.

Important Pitfalls

1. Treating all cholinergic poisonings as organophosphate poisoning

Direct agonists stimulate receptors.

Organophosphates inhibit AChE.

This fundamentally changes the role of pralidoxime.

2. Giving pralidoxime for confirmed bethanechol or pilocarpine overdose

There is no inhibited AChE enzyme for pralidoxime to reactivate.

Use atropine.

3. Checking cholinesterase levels to diagnose direct agonist toxicity

Cholinesterase levels are not expected to fall.

A normal level is therefore unsurprising.

4. Calling methacholine a major nicotinic agonist

Methacholine’s clinically important action is:

Muscarinic bronchoconstriction

Current Provocholine specifically warns about severe bronchospasm.

5. Missing severe methacholine bronchospasm

Treat rapidly with:

Inhaled β₂ agonist

rather than waiting for spontaneous recovery.

6. Assuming all direct cholinergic agents cause paralysis

Profound:

• Fasciculations
• Weakness
• Flaccid paralysis

are more suggestive of substantial nicotinic excess from anticholinesterase poisoning.

7. Using massive organophosphate atropine doses automatically

Direct muscarinic agonist overdose often responds to much smaller atropine doses.

Titrate to the patient.

8. Titrating atropine to pupil size

Treat:

• Bronchial secretions
• Bronchospasm
• Bradycardia/perfusion

not persistent miosis.

9. Forgetting atropine toxicity

Over-treatment can transform:

Cholinergic toxicity → anticholinergic delirium

especially because direct agonist poisoning is often relatively short-lived.

10. Assuming methacholine is a treatment for asthma

It does the opposite.

Methacholine is a:

Diagnostic bronchoprovocation agent

and current labeling carries a boxed warning for severe bronchoconstriction.

11. Using the old natural-product classification

Correct associations:

• Pilocarpus → pilocarpine
• Areca catechu nut → arecoline
• Inocybe/Clitocybe → muscarine

The betel leaf itself is not the primary source of arecoline.

12. Forgetting cevimeline

Cevimeline is an important modern direct muscarinic agonist used for:

Sjögren-associated xerostomia.

13. Missing new carbachol ophthalmic formulations

As of 2026, YUVEZZI (carbachol + brimonidine) is FDA-approved for adult presbyopia, expanding current therapeutic exposure beyond the older intraoperative preparations.

14. Using routine gastric lavage

Modern poisoning management does not support routine lavage for these pharmaceutical ingestions.

Supportive care and atropine matter far more.

High-Yield Toxicology Pearls

Direct cholinergic agonists = primarily muscarinic toxidrome

Think:

Wet + wheezy + slow

Typical syndrome:

Salivation + lacrimation + diaphoresis + diarrhea/vomiting + miosis + bronchospasm + bradycardia

Key points:

• Direct agonists bind cholinergic receptors directly
• They do not require acetylcholinesterase inhibition
• Important agents:
• Acetylcholine
• Bethanechol
• Carbachol
• Methacholine
• Pilocarpine
• Cevimeline
• Bethanechol → predominantly muscarinic
• Methacholine → predominantly muscarinic
• Pilocarpine → predominantly muscarinic
• Carbachol → muscarinic + nicotinic
• Arecoline → mainly muscarinic partial agonist with some nicotinic activity
• Major dangerous manifestations:
• Bronchospasm
• Bronchial secretions
• Bradycardia
• Hypotension
• Main antidote:
• ATROPINE
• Direct agonist overdose often needs much less atropine than severe OP poisoning
• Pilocarpine label example:
• Atropine 0.5–1 mg IV/SC, titrated
• Treat to:
• Controlled bronchial secretions
• Improved bronchospasm
• Adequate perfusion
• Do not titrate atropine to pupil size
• Pralidoxime is NOT indicated for confirmed isolated direct agonist poisoning
• Cholinesterase measurements are not clinically useful
• Severe methacholine bronchospasm:
• Rapid-acting inhaled β₂ agonist
• Methacholine challenge:
• Approved for airway-hyperreactivity testing in patients ≥5 years
• Contraindicated when baseline FEV₁ <60% predicted
• Pilocarpine:
• Used for xerostomia after head/neck radiation and Sjögren syndrome
• Cevimeline:
• Used for Sjögren-associated xerostomia
• Carbachol:
• Intraocular miotic
• 2026: carbachol/brimonidine YUVEZZI approved for presbyopia
• Natural sources:
• Areca nut → arecoline
• Inocybe/Clitocybe mushrooms → muscarine
• Pilocarpus → pilocarpine
• Do not induce vomiting
• Activated charcoal only for selected recent oral exposures with a protected airway
• Routine gastric lavage is obsolete
• No routine role for dialysis
• Most isolated direct-agonist poisonings recover completely with prompt supportive care and atropine

Toxicology – Chlorine

Core concept

Chlorine (Cl₂) is a highly reactive, water-soluble pulmonary irritant gas that primarily damages the eyes, upper airway, and lungs.

The classic exposure syndrome is:

Chlorine inhalation → immediate eye/throat burning + cough → bronchospasm/chest tightness → chemical pneumonitis ± noncardiogenic pulmonary edema/ARDS

The most important treatment is:

Remove from exposure + airway/oxygenation support + inhaled bronchodilators for bronchospasm

There is:

No specific antidote

Most mild exposures resolve completely, but significant exposures can cause progressive lung injury over several hours and occasionally persistent reactive airways dysfunction syndrome (RADS). Current CDC guidance notes that lung function usually returns toward baseline within about 7–14 days after uncomplicated exposure, although more serious exposures can produce prolonged respiratory problems.

Physical Properties

Chlorine is:

• Chemical formula: Cl₂
• Greenish-yellow gas at room temperature
• Pungent, highly irritating odor
• Approximately 2.5 times heavier than air
• Shipped industrially as a liquefied compressed gas
• Nonflammable, but a powerful oxidizing agent

It can accumulate in:

• Basements
• Pits
• Low-lying areas
• Poorly ventilated enclosed spaces

and may react dangerously with many combustible or reducing materials.

Important Terminology

Chlorine Gas ≠ Household Bleach

These are related but distinct exposures.

Chlorine gas

Cl₂

Primary toxicity:

Inhalational pulmonary injury

Household bleach

Usually contains:

Sodium hypochlorite (NaOCl)

Primary toxicity:

• Local irritation
• Caustic injury if concentrated
• Generation of toxic gases if mixed with other cleaners

Therefore, a patient who “drank chlorine” usually ingested hypochlorite solution, not gaseous molecular chlorine.

How Household Mixing Produces Toxic Gas

This is one of the most important practical chlorine toxicology points.

Bleach + Acid

For example:

• Toilet-bowl cleaner
• Hydrochloric-acid cleaner
• Vinegar

can produce:

CHLORINE GAS

Hypochlorite + acid → Cl₂ release

Bleach + Ammonia

Mixing hypochlorite bleach with ammonia-containing products produces:

CHLORAMINES

rather than simply molecular chlorine.

Chloramine gases are also respiratory irritants and can produce:

• Eye burning
• Cough
• Dyspnea
• Bronchospasm
• Pulmonary injury

Practical rule

Never mix bleach with another household cleaner.

Sources and Uses

Important exposure settings include:

• Water-treatment facilities
• Sewage treatment
• Swimming-pool maintenance
• Chemical manufacturing
• Pulp/paper and textile bleaching
• Plastics and synthetic-material production
• Cleaning accidents
• Industrial chlorine-cylinder leaks
• Accidental mixing of household cleaning agents

Chlorine has also historically been used as a chemical warfare agent.

Routes of Exposure

Inhalation

By far the most important route.

Eyes

Gas or liquid splashes can produce significant injury.

Skin

Concentrated chlorine gas, liquid chlorine, or chlorine-generating solutions can cause chemical injury.

Ingestion

Elemental chlorine is a gas at room temperature, so ingestion typically refers to:

Sodium/calcium hypochlorite solutions

rather than Cl₂ itself.

Toxic Dose / Concentration

Toxicity is determined by:

Concentration × duration of exposure

There is no single clinically reliable toxic dose.

Historical human observations suggest:

• Approximately 1–10 ppm can produce irritation
• Concentrations above roughly 15 ppm can cause significant respiratory distress
• Very high concentrations can produce rapidly fatal pulmonary injury

ATSDR historically estimated a lowest lethal concentration around 430 ppm for 30 minutes, but such numbers should not be interpreted as safe/unsafe cutoffs.

A far more useful occupational emergency threshold is:

NIOSH IDLH = 10 ppm

meaning 10 ppm is considered immediately dangerous to life or health.

Pathophysiology

Chlorine readily reacts with water present on moist respiratory surfaces.

A simplified reaction produces:

Cl₂ + H₂O → hydrochloric acid + hypochlorous acid

This initiates:

• Oxidative injury
• Chlorination reactions
• Free-radical formation
• Direct epithelial damage

The older concept that chlorine toxicity is simply due to formation of hydrochloric acid and hypochlorous acid is incomplete.

Modern understanding emphasizes:

Oxidative injury + epithelial disruption + inflammatory signaling

as major contributors to pulmonary damage.

Airway and Lung Injury

Chlorine causes:

Epithelial injury → increased permeability → inflammation → bronchoconstriction + alveolar-capillary leak

This can produce:

• Bronchospasm
• Airway edema
• Chemical pneumonitis
• Noncardiogenic pulmonary edema
• ARDS

The degree of water solubility means much of the gas is absorbed in the upper respiratory tract, but sufficiently high exposure reaches and injures distal bronchioles and alveoli.

Why Symptoms Can Worsen Later

Severe chlorine injury does not always peak immediately.

The sequence may be:

Exposure → irritation/cough → transient improvement → increasing dyspnea/hypoxemia → pulmonary edema

Pulmonary injury in symptomatic patients can progress for several hours after exposure.

Therefore:

A normal early chest radiograph does not exclude evolving serious lung injury.

Risk Factors for Severe Toxicity

Greater risk occurs with:

• High concentration
• Longer exposure
• Enclosed-space exposure
• Delayed escape
• Preexisting asthma
• COPD
• Other chronic pulmonary disease

Children may be especially vulnerable because:

• Smaller airway diameter
• Greater minute ventilation per kilogram
• Short stature may place them closer to heavier-than-air chlorine concentrations near ground level.

Clinical Features

Mild Exposure

Typical findings:

• Eye irritation
• Lacrimation
• Rhinorrhea
• Burning nose/throat
• Sore throat
• Cough
• Mild chest burning
• Headache

Symptoms usually begin rapidly.

Moderate Exposure

Possible findings:

• Persistent cough
• Chest tightness
• Dyspnea
• Wheezing
• Hoarseness
• Tachypnea
• Bronchospasm
• Hypoxemia

A patient may describe:

“Burning in the chest”

which is characteristic of significant irritant-gas exposure.

Severe Exposure

High-dose exposure can cause:

• Severe bronchospasm
• Upper-airway edema
• Stridor
• Hemoptysis
• Diffuse crackles
• Severe hypoxemia
• Noncardiogenic pulmonary edema
• ARDS
• Respiratory failure
• Cardiovascular collapse

Severe hypoxia can cause:

• Confusion
• Syncope
• Seizures
• Cardiac arrest

HEENT

Common findings include:

• Blepharospasm
• Conjunctival injection
• Tearing
• Nasal irritation
• Pharyngeal irritation

Severe exposure can cause:

• Corneal epithelial injury
• Corneal burns

Upper Airway

Warning findings include:

• Hoarseness
• Drooling
• Stridor
• Progressive respiratory distress
• Inability to manage secretions

Significant laryngeal edema can make later intubation difficult.

Therefore:

Progressive upper-airway obstruction → secure the airway early.

Pulmonary

Common respiratory findings include:

• Cough
• Wheezing
• Rhonchi
• Crackles
• Tachypnea

More severe toxicity:

• Hemoptysis
• Hypoxemia
• Pulmonary edema
• ARDS

Current systematic reviews find that the dominant clinical features of civilian chlorine exposures are cough and dyspnea; the majority recover completely, although severe exposures can be fatal.

Cardiovascular

Cardiac abnormalities are usually secondary to:

• Hypoxemia
• Severe pulmonary injury
• Physiologic stress

Possible findings:

• Tachycardia
• Initial hypertension
• Later hypotension
• Cardiovascular collapse in profound exposure

Chlorine does not characteristically cause a primary cardiotoxic dysrhythmia syndrome.

Neurologic

Mild:

• Headache
• Dizziness
• Lightheadedness

Severe:

• Confusion
• Syncope
• Seizures/coma secondary to major hypoxia

Marked altered consciousness should prompt consideration of:

• Severe hypoxemia
• Additional toxicant
• Trauma
• Alternative diagnosis

Acid–Base Effects

Massive inhalation can occasionally produce:

Hyperchloremic metabolic acidosis

although metabolic acidosis in critically ill patients may also reflect:

• Hypoxia
• Shock
• Lactate accumulation

Skin

Gas exposure usually causes mild irritation.

More concentrated exposure may cause:

• Burning
• Erythema
• Blistering
• Chemical burns

Liquefied chlorine

Contact with liquefied compressed chlorine can additionally produce:

Frostbite

because of rapid evaporative cooling.

Ocular Exposure

Possible findings:

• Immediate burning
• Tearing
• Blepharospasm
• Conjunctivitis

Severe exposure:

• Corneal epithelial injury
• Corneal burn

Persistent:

• Pain
• Photophobia
• Visual change

requires formal ophthalmologic evaluation.

Household Bleach Ingestion

Low-concentration household sodium hypochlorite exposures are generally much less dangerous than concentrated industrial hypochlorite.

Small accidental swallows commonly cause:

• Oral irritation
• Nausea
• Vomiting
• Abdominal discomfort

More concentrated products can cause:

True caustic injury

including:

• Odynophagia
• Dysphagia
• Esophagitis
• Gastric injury
• Hematemesis
• Perforation in extreme cases

Modern household products vary in concentration; some are more concentrated than the traditional 3–6% bleach formulations.

Diagnosis

Diagnosis of chlorine inhalation is primarily:

Clinical

based on:

• Exposure history
• Characteristic odor/event
• Immediate mucosal irritation
• Respiratory findings

There is no clinically useful:

• Serum chlorine concentration
• Urinary chlorine assay

for routine emergency diagnosis.

Differential Diagnosis

Other pulmonary irritant exposures include:

• Ammonia
• Bromine
• Phosgene
• Nitrogen dioxide
• Sulfur dioxide
• Acrolein
• Smoke inhalation
• Chloramine gases

Also consider:

• Asthma exacerbation
• Anaphylaxis
• Pneumonia
• Pulmonary edema
• Aspiration

In structure-fire patients, also consider:

• Carbon monoxide
• Cyanide
• Multiple combustion products

Investigations

Mild Exposure

No laboratory testing is usually needed when symptoms:

• Are minor
• Resolve quickly
• Have a reliable low-level exposure history

Respiratory Evaluation

For significant respiratory symptoms obtain:

• Continuous pulse oximetry
• Serial lung examination

Consider:

• Blood gas
• Chest radiograph

for:

• Persistent dyspnea
• Hypoxemia
• Severe cough
• Crackles
• Hemoptysis
• Significant exposure

Chest Radiograph

Possible abnormalities include:

• Diffuse infiltrates
• Pulmonary edema
• Patchy chemical pneumonitis

However:

An early normal CXR does not exclude later pulmonary edema.

Clinical observation remains important.

Laboratory Tests

Moderate/severe exposures may warrant:

• Electrolytes
• Bicarbonate
• BUN
• Creatinine
• Glucose

For critical illness:

• Blood gas
• Lactate

CBC may be obtained when:

• Serious pulmonary injury
• Infection differential
• Critical illness

is present.

Pulmonary Function

Peak expiratory flow or spirometry can be useful in patients with:

• Bronchospasm
• Persistent respiratory symptoms
• Suspected RADS

but is not required in every acute exposure.

Bronchoscopy

Routine bronchoscopy is not necessary.

It may be considered for:

• Severe airway injury
• Persistent unexplained respiratory failure
• Suspected inhalational mucosal injury
• Airway obstruction requiring direct assessment

Treatment

1. Rescuer Safety

Do not enter a high-concentration chlorine environment without appropriate respiratory protection.

For unknown or dangerous concentrations:

Positive-pressure self-contained breathing apparatus (SCBA) is required.

Because chlorine is heavier than air:

Move upwind and to higher ground when practical.

2. Remove From Exposure

The single most important immediate intervention is:

Fresh air

Move the patient rapidly away from the contaminated environment.

A patient exposed only to chlorine gas without contaminated clothing or liquid chemical generally does not remain a significant secondary contamination hazard once removed from the source.

3. Airway

Assess for:

• Hoarseness
• Stridor
• Progressive edema
• Severe respiratory distress
• Altered consciousness

If airway compromise is evolving:

Intubate early

Use direct visualization/video laryngoscopy or other controlled techniques.

Severe edema can make delayed airway management extremely difficult.

4. Oxygen

Give supplemental oxygen for:

• Dyspnea
• Hypoxemia
• Significant respiratory distress

Patients with severe toxicity may require:

• High-flow oxygen
• Noninvasive support in carefully selected cases
• Endotracheal intubation/mechanical ventilation

Current systematic evidence supports exposure cessation and oxygen as core supportive therapies.

5. Bronchospasm

Inhaled β₂ agonists are standard treatment.

Examples:

• Albuterol
• Salbutamol

Ipratropium may be added for severe bronchospasm according to standard obstructive-airway management.

Systematic review evidence supports inhaled bronchodilators as standard therapy for chlorine-associated bronchoconstriction.

6. Pulmonary Edema / ARDS

Treat according to standard supportive critical-care principles:

• Oxygen
• Appropriate PEEP
• Lung-protective ventilation
• Conservative fluid strategy once shock is corrected

Chlorine-induced pulmonary edema is generally:

Noncardiogenic

so routine diuretics are not an antidote and should not be automatically administered unless there is an independent indication.

7. Corticosteroids

Important modernization

The older text recommends prednisone or methylprednisolone rather broadly after chlorine inhalation.

Modern evidence does not support routine corticosteroids for every chlorine exposure.

Human studies are limited and confounded because steroids are usually administered together with:

• Oxygen
• Bronchodilators
• Other therapies

Systematic reviews conclude that the independent benefit of corticosteroids remains uncertain.

Reasonable use

Steroids may be considered when there is:

• Significant asthma/reactive-airway exacerbation
• Persistent bronchospasm consistent with usual asthma indications

But:

Routine prophylactic steroids to prevent pulmonary edema or fibrosis are not evidence-based.

Nebulized Sodium Bicarbonate

This requires correction from the older text.

The older chapter states that sodium bicarbonate is ineffective and may itself cause chemical pneumonitis.

Current evidence is more nuanced.

A randomized human study using nebulized bicarbonate in chlorine-induced RADS found modest improvement in FEV₁ at 2 and 4 hours, but no evidence that it prevents major outcomes such as:

• Intubation
• Pulmonary edema
• Long-term lung disease
• Mortality

Therefore:

Nebulized sodium bicarbonate is not established first-line therapy.

It may be considered as an adjunct in selected symptomatic patients after consultation with a poison center/medical toxicologist.

It should never replace:

• Fresh air
• Oxygen
• Bronchodilators
• Airway management

No Specific Antidote

There is no antidote for chlorine gas toxicity.

Current CDC and NIOSH guidance emphasizes supportive respiratory care.

Skin Decontamination

For liquid/chlorine-generating chemical contamination:

• Remove contaminated clothing
• Rinse exposed skin/hair with copious tepid water
• Wash with mild soap
• Rinse again

Patients exposed only to gas and without skin/eye irritation usually do not require full decontamination.

Liquefied Chlorine Frostbite

If liquefied chlorine causes frostbite:

• Do not rub
• Remove constricting items
• Rewarm in water approximately 40–42°C

until tissue perfusion returns.

Eye Decontamination

Immediately:

Irrigate with copious water or saline for at least 15 minutes

Remove contact lenses when easily possible.

Then assess:

• Visual acuity
• Cornea

Persistent:

• Pain
• Photophobia
• Vision change
• Corneal injury

requires urgent ophthalmology assessment.

Hypochlorite Ingestion

Do NOT induce vomiting

Never induce emesis.

This risks:

• Re-exposure of the esophagus
• Aspiration

CDC/ATSDR guidance specifically advises against induced vomiting.

Activated Charcoal

Do not routinely give activated charcoal for hypochlorite ingestion.

It provides little benefit and may:

• Promote vomiting
• Increase aspiration risk
• Complicate subsequent endoscopic assessment

Gastric Lavage / Aspiration

The older recommendation for nasogastric aspiration after a large ingestion is not modern routine practice.

Routine gastric lavage is not recommended.

Potential complications include:

• Perforation
• Aspiration
• Additional mucosal trauma

ATSDR specifically notes that gastric lavage is generally not recommended for hypochlorite ingestion.

Oral Dilution After Bleach Ingestion

Older guidance recommends 4–8 oz of milk or water.

Modern practice is more conservative.

After a small recent lower-concentration household bleach exposure, an alert patient who can swallow normally may rinse the mouth and take a small amount of water.

However:

Do not force oral dilution in a symptomatic patient or significant caustic ingestion.

Avoid oral fluids with:

• Drooling
• Dysphagia
• Repeated vomiting
• Airway compromise
• Severe pain
• Suspected perforation

The patient’s airway and GI injury assessment take priority.

Endoscopy After Hypochlorite Ingestion

Routine endoscopy is unnecessary after an uncomplicated small household bleach exposure.

Consider GI/endoscopic evaluation with:

• Concentrated product
• Intentional large ingestion
• Persistent vomiting
• Drooling
• Odynophagia/dysphagia
• Chest or abdominal pain
• Hematemesis
• Other evidence of caustic injury

Severe hypochlorite ingestion should be managed according to general caustic-ingestion principles.

Antibiotics

Routine prophylactic antibiotics have no established role after isolated chlorine inhalation.

Use antibiotics only when there is evidence of:

• Bacterial pneumonia
• Aspiration infection
• Another infectious process

Chemical pneumonitis alone is not an indication for antibiotics.

Monitoring

Symptomatic patients should be monitored for:

• Respiratory rate
• Oxygen saturation
• Work of breathing
• Bronchospasm
• Progression of chest symptoms

Continuous cardiac monitoring is reasonable in:

• Severe hypoxemia
• Critical illness
• Significant coexposures

Observation

The older concept of a rigid observation interval is less useful than clinical severity.

Minor exposure

Patients with only:

• Transient throat/eye irritation
• Minimal cough
• Normal oxygenation

who become fully asymptomatic may often be discharged after an appropriate period of observation.

ATSDR notes that minor symptoms commonly resolve within about an hour.

Significant exposure

Patients with:

• Persistent cough
• Dyspnea
• Chest tightness
• Wheezing
• Hypoxemia
• High-concentration exposure

should be observed longer because:

Pulmonary injury may progress over several hours.

Admission

Hospital admission is appropriate for:

• Persistent dyspnea
• Severe/persistent cough
• Significant bronchospasm
• Hypoxemia
• Hemoptysis
• Upper-airway edema
• Stridor
• Abnormal CXR with pulmonary injury
• Noncardiogenic pulmonary edema
• Significant ocular/skin burns
• Significant caustic hypochlorite ingestion

ICU care is appropriate for:

• Progressive hypoxemia
• Respiratory failure
• ARDS
• Mechanical ventilation
• Hemodynamic instability

Discharge

Discharge requires:

• Resolution or clear improvement of respiratory symptoms
• Normal/reassuring oxygenation
• No progressive airway findings
• Ability to ambulate without significant dyspnea
• Reliable return precautions

Patients should return urgently for:

• Increasing cough
• Wheezing
• Dyspnea
• Chest pain
• Hemoptysis

because deterioration can occur after apparent early improvement.

Long-Term Pulmonary Effects

Most patients recover completely.

Systematic civilian data reported full recovery in approximately 90% of cases with available follow-up.

However, significant exposure can produce:

Reactive Airways Dysfunction Syndrome (RADS)

which is irritant-induced asthma developing after a major exposure.

Symptoms may include:

• Persistent cough
• Wheezing
• Exercise intolerance
• Airway hyperreactivity

ATSDR reports that chlorine-induced RADS has occasionally persisted for years.

Pulmonary Fibrosis

Older sources often emphasize interstitial fibrosis as a common sequela.

Persistent structural lung disease can occur after severe exposure, but:

Permanent pulmonary fibrosis is not the expected outcome of most chlorine exposures.

Most patients recover substantially, while persistent airway hyperreactivity/RADS is a more clinically recognized long-term syndrome.

Pregnancy

The older claim that concentrated hypochlorite is clearly teratogenic should not be directly extrapolated to human chlorine-gas poisoning.

Available data are insufficient to establish a specific human teratogenic syndrome from chlorine exposure.

In significant maternal poisoning, the main fetal threats are likely secondary to:

• Maternal hypoxemia
• Respiratory failure
• Hemodynamic instability

Therefore:

Maternal airway and oxygenation are the priorities.

Do not withhold appropriate oxygen, bronchodilators, airway support, or critical care because of pregnancy.

Occupational Exposure Standards – Chlorine

The old workplace values are outdated.

Current NIOSH

REL: ceiling 0.5 ppm (1.45 mg/m³) over 15 minutes

Current OSHA

PEL: ceiling 1 ppm (3 mg/m³)

NIOSH IDLH

10 ppm

Important correction

The older chapter states:

• OSHA TWA 0.5 ppm
• OSHA STEL 1 ppm
• IDLH 25 ppm

Those values should not be used.

Current federal OSHA is a 1-ppm ceiling, while current NIOSH IDLH is 10 ppm.

Chlorine Dioxide Is a Different Chemical

Chlorine dioxide (ClO₂) is not interchangeable with chlorine gas.

Current occupational values:

• NIOSH REL TWA: 0.1 ppm
• NIOSH STEL: 0.3 ppm
• OSHA PEL TWA: 0.1 ppm
• NIOSH IDLH: 5 ppm

Chlorine Trifluoride Is Also Distinct

Chlorine trifluoride (ClF₃) is a highly reactive fluorinating agent with additional extreme chemical hazards.

Current values:

• NIOSH REL ceiling: 0.1 ppm
• OSHA PEL ceiling: 0.1 ppm
• NIOSH IDLH: 12 ppm

It should not be managed as simply another formulation of ordinary chlorine gas.

Important Pitfalls

1. Confusing chlorine gas with bleach

Bleach contains hypochlorite.

The most dangerous household inhalational exposures frequently occur when bleach reacts with another cleaner.

2. Saying bleach + ammonia produces ordinary chlorine

More precisely:

Bleach + ammonia → chloramines

whereas:

Bleach + acid → chlorine gas

3. Trusting an early normal chest radiograph

Pulmonary edema may develop later.

Normal early CXR ≠ safe after a significant exposure.

4. Sending home a persistently symptomatic patient

Persistent:

• Dyspnea
• Severe cough
• Chest tightness

warrants continued observation/admission because lung injury can progress for several hours.

5. Giving steroids routinely

Evidence for corticosteroids specifically preventing chlorine lung injury is weak.

Use primarily when there is a separate clinical indication such as significant reactive-airway/asthma physiology.

6. Calling nebulized bicarbonate useless

Evidence shows a possible modest short-term spirometric benefit, but not proven major outcome benefit.

Therefore:

Possible adjunct—not standard antidote.

7. Forgetting bronchodilators

Bronchospasm is common and:

Inhaled β₂ agonists are standard therapy.

8. Treating pulmonary edema automatically with diuretics

Chlorine pulmonary edema is typically:

Permeability/noncardiogenic edema

Treat primarily with respiratory support.

9. Giving charcoal after bleach ingestion

Activated charcoal is not recommended for hypochlorite ingestion.

10. Performing gastric lavage after concentrated bleach ingestion

Routine lavage is inappropriate and may worsen caustic injury.

11. Missing airway edema

Hoarseness and stridor after major exposure may precede severe airway compromise.

Intubate before edema makes intubation impossible.

12. Ignoring low-lying chlorine accumulation

Chlorine is approximately 2.5 times heavier than air.

Children and incapacitated individuals near floor level can receive greater exposure.

13. Assuming the patient contaminates the ED indefinitely

After gas-only exposure, patients generally pose little secondary contamination risk once removed to clean air.

Liquid chemical contamination is different and requires decontamination.

14. Using the old IDLH

Current:

NIOSH IDLH = 10 ppm

not 25 ppm.

High-Yield Toxicology Pearls

Chlorine = water-soluble pulmonary irritant gas

Think:

Bleach/industrial chlorine exposure → burning eyes/throat + cough + bronchospasm → delayed pulmonary edema in severe cases

Key points:

• Chlorine is:
• Greenish-yellow
• Pungent
• Heavier than air
• Main route of serious exposure: inhalation
• Mechanism:
• Reaction with water
• Hypochlorous/hydrochloric acid formation
• Oxidative epithelial injury
• Main targets:
• Eyes
• Upper airway
• Bronchi
• Lungs
• Household chemistry:
• Bleach + acid → chlorine gas
• Bleach + ammonia → chloramines
• Mild exposure:
• Eye/throat irritation
• Cough
• Moderate:
• Chest tightness
• Wheezing
• Bronchospasm
• Severe:
• Stridor
• Hemoptysis
• Hypoxemia
• Noncardiogenic pulmonary edema
• ARDS
• Symptoms may worsen for several hours
• Normal early CXR does not exclude serious injury
• Treatment:
• Fresh air
• Oxygen when symptomatic/hypoxemic
• Inhaled β₂ agonists for bronchospasm
• Early airway control if progressive edema
• Lung-protective ventilation for ARDS
• Routine corticosteroids are not proven
• Nebulized sodium bicarbonate:
• May modestly improve short-term FEV₁
• Not established first-line therapy
• Consider only as an adjunct
• No specific antidote
• Eye exposure:
• Immediate irrigation ≥15 min
• Liquid chlorine can cause frostbite
• Small household-bleach swallows usually cause GI irritation
• Concentrated hypochlorite can cause caustic esophagogastric injury
• Do not induce vomiting
• Do not give routine activated charcoal
• Routine gastric lavage is not recommended
• Significant bleach ingestion + dysphagia/hematemesis → evaluate as caustic ingestion
• Major long-term complication:
• RADS / irritant-induced asthma
• Occupational chlorine limits:
• NIOSH ceiling: 0.5 ppm / 15 min
• OSHA ceiling: 1 ppm
• NIOSH IDLH: 10 ppm
• Chlorine dioxide and chlorine trifluoride are distinct chemicals with separate exposure limits and hazards

Toxicology – Chloral Hydrate

Core concept

Chloral hydrate is an old sedative-hypnotic that is rapidly converted to the active CNS depressant trichloroethanol (TCE).

The characteristic severe overdose syndrome is:

CNS depression → respiratory depression/coma + myocardial depression + catecholamine-sensitive ventricular dysrhythmias

The distinctive toxicologic danger is the combination of:

Coma + refractory ventricular dysrhythmias

Severe poisoning may produce:

• Respiratory failure
• Hypotension
• Ventricular tachycardia
• Torsades de pointes
• Ventricular fibrillation
• Cardiac arrest

Treatment is primarily:

Airway/ventilatory support + continuous ECG monitoring + targeted treatment of dysrhythmias

There is no specific chemical antidote.

Current Status and Uses

Chloral hydrate was historically used for:

• Insomnia
• Sedation
• Pediatric procedural sedation
• Preanesthetic medication
• Alcohol withdrawal

Most of these uses have largely been replaced by medications with better:

• Pharmacokinetics
• Safety margins
• Reversibility

such as benzodiazepines and dexmedetomidine.

The former U.S. product Somnote is listed by FDA as a discontinued chloral hydrate product with no generic equivalent. (FDA Access Data⁠)

Chloral hydrate nevertheless remains in use in some countries and institutions, particularly for pediatric diagnostic/procedural sedation, and may also be encountered through compounded preparations. Contemporary pediatric literature still describes its procedural use internationally. (PubMed Central (PMC)⁠)

In the United States, chloral hydrate remains a:

Schedule IV controlled substance

because of abuse/dependence potential. (PubChem⁠)

Forms

Historically available formulations included:

• Oral solution/syrup
• Capsules/tablets
• Rectal preparations

Current availability varies significantly by country.

The older routine adult insomnia dose of 0.5–1 g is mainly of historical relevance rather than a preferred modern insomnia regimen.

Toxic Dose

There is no reliably safe numerical cutoff after overdose.

Significant toxicity can occur after relatively modest supratherapeutic doses, particularly with:

• Other CNS depressants
• Cardiovascular disease
• Young age
• Delayed airway management

Historical reports describe fatalities after approximately:

4–10 g

but survival has also occurred after much larger doses with aggressive critical care and extracorporeal treatment. (PubMed⁠)

Thus:

Clinical toxicity is more important than the reported dose.

Pathophysiology

Active Metabolite – Trichloroethanol

Chloral hydrate itself has an extremely short presence in the circulation and is rapidly converted, primarily through alcohol dehydrogenase, to:

Trichloroethanol (TCE)

TCE accounts for much of the:

• Sedation
• Hypnosis
• CNS depression

Chloral hydrate and TCE are believed to enhance inhibitory signaling involving:

GABA-A receptors

although their mechanism is less precisely characterized than that of modern benzodiazepines. (PubMed Central (PMC)⁠)

Metabolism

A simplified pathway is:

Chloral hydrate → trichloroethanol → glucuronide metabolites

and:

Chloral hydrate → trichloroacetic acid (TCA)

TCE is the major active metabolite.

At therapeutic exposure its half-life is approximately:

8–12 hours

but in overdose its elimination can be markedly prolonged, with reported half-lives extending toward 24–35 hours or longer. (PubMed Central (PMC)⁠)

Therefore:

Clinical depression may substantially outlast disappearance of the parent chloral hydrate.

Ethanol Interaction

The older description of a simple “disulfiram-like reaction” is incomplete.

The more clinically important interaction is:

Chloral hydrate + ethanol → enhanced and prolonged CNS depression

Human pharmacokinetic studies found that ethanol can increase and prolong plasma TCE concentrations, while TCE can inhibit ethanol metabolism. (ASCPT⁠)

Thus:

Alcohol + chloral hydrate is a particularly dangerous sedative combination.

This interaction contributed historically to chloral hydrate’s notorious use in drug-facilitated intoxication.

Cardiac Toxicity

Cardiotoxicity is one of the most distinctive features of severe chloral hydrate poisoning.

Effects include:

• Reduced myocardial contractility
• Increased cardiac automaticity
• Shortened refractory periods
• Sensitization of the myocardium to catecholamines

This catecholamine sensitization predisposes to:

Ventricular ectopy → VT → VF

especially when endogenous or administered catecholamines are high. (PubMed Central (PMC)⁠)

Clinical Features

Neurologic

Possible manifestations include:

• Dizziness
• Lightheadedness
• Ataxia
• Dysarthria
• Somnolence
• Confusion
• Depressed reflexes

Severe poisoning:

• Coma
• Respiratory depression
• Rare seizures

The dominant neurologic syndrome is generally:

Sedative-hypnotic CNS depression

Respiratory

Severe poisoning may cause:

Bradypnea → hypoventilation → hypercapnia → apnea

Additional complications include:

• Loss of airway reflexes
• Aspiration
• Hypoxic injury

Early intubation is appropriate for:

• Progressive CNS depression
• Inadequate ventilation
• Loss of airway protection
• Severe cardiovascular toxicity

Current pediatric toxicology guidance specifically emphasizes early intubation when CNS or cardiovascular toxicity is progressing. (Royal Children’s Hospital⁠)

Cardiovascular

Possible effects include:

• Sinus tachycardia
• Hypotension
• Myocardial depression
• Ventricular ectopy
• Bigeminy
• Supraventricular tachyarrhythmias
• Ventricular tachycardia
• Torsades de pointes
• Ventricular fibrillation

A case series reported transient bigeminy after an estimated 219 mg/kg ingestion and torsades/VF after a much larger ingestion. (PubMed⁠)

Cardiovascular toxicity can dominate the presentation even when ventilation is being supported.

Gastrointestinal

Chloral hydrate is directly irritating to the GI tract.

Possible symptoms:

• Nausea
• Vomiting
• Epigastric pain
• Esophageal discomfort
• Abdominal pain

Gastric mucosal irritation can be substantial after large ingestion.

HEENT

Reported findings include:

• Miosis
• Mucosal irritation
• Occasionally a characteristic pungent/pear-like odor on the breath

These findings are neither sensitive nor specific enough to establish the diagnosis.

Hypothermia

Like other sedative-hypnotic poisonings, severe intoxication may result in:

Hypothermia

particularly after prolonged coma or environmental exposure.

Diagnosis

Diagnosis is generally:

Exposure history + sedative toxidrome ± characteristic ventricular dysrhythmias

There is no routine rapidly available serum chloral hydrate concentration that guides emergency management.

Laboratory Investigations

For significant poisoning obtain:

• Bedside glucose
• Electrolytes
• Potassium
• Magnesium
• Calcium
• Bicarbonate
• BUN
• Creatinine

In severe toxicity consider:

• Blood gas
• Lactate
• Liver enzymes
• CK after prolonged coma/seizures

For intentional overdose obtain appropriate coingestant testing, including:

• Acetaminophen concentration
• Salicylate concentration

when relevant.

ECG

Every significant chloral hydrate overdose requires an ECG and continuous cardiac monitoring.

Look for:

• Ventricular ectopy
• Bigeminy
• QT abnormalities
• Ventricular tachycardia
• Torsades
• VF

Serious dysrhythmias may occur abruptly.

Trichloroethanol Levels

Specialized laboratories can measure:

• TCE
• Trichloroacetic acid
• Related metabolites

However:

These levels are generally not rapidly available and should not guide initial emergency treatment.

Treatment remains clinical.

Differential Diagnosis

Consider other causes of CNS depression including:

• Ethanol
• Benzodiazepines
• Barbiturates
• Opioids
• Meprobamate
• Carisoprodol
• Baclofen
• Other sedative-hypnotics

If prominent ventricular dysrhythmias are present, also consider:

• Tricyclic antidepressants
• Cocaine
• Sodium-channel blockers
• Chlorinated hydrocarbons
• Electrolyte abnormalities

Treatment

1. Airway and Ventilation

The cornerstone of therapy is:

Aggressive supportive airway management

Provide:

• Oxygen
• Ventilatory assistance as necessary
• Continuous pulse oximetry
• Capnography when available

Intubate early for:

• Progressive coma
• Hypoventilation
• Recurrent vomiting with impaired consciousness
• Cardiovascular deterioration

Do not wait for profound hypoxemia.

2. Continuous ECG Monitoring

Significant poisoning requires:

• Cardiac monitor
• Defibrillator immediately available
• Frequent blood-pressure measurement
• Serial electrolytes

Correct:

• Hypokalemia
• Hypomagnesemia
• Hypocalcemia

because electrolyte abnormalities can amplify ventricular dysrhythmia risk.

3. Ventricular Dysrhythmias – Key Toxicology Point

Chloral-hydrate dysrhythmias may be unusually resistant to routine antiarrhythmics because of:

Myocardial catecholamine sensitization

Historical and modern case literature repeatedly describes successful control with:

β-adrenergic blockade

particularly:

• Esmolol
• Propranolol

(PubMed⁠)

Esmolol

Esmolol is particularly attractive in severe poisoning because:

• Very short half-life
• Rapid titratability
• Can be quickly discontinued if hypotension worsens

Thus:

Refractory catecholamine-sensitive ventricular tachydysrhythmia → consider esmolol with toxicology/cardiology input.

This is not routine therapy for uncomplicated sinus tachycardia.

Torsades de Pointes

Treat according to standard principles:

• Immediate defibrillation if unstable/pulseless
• Correct potassium
• Correct magnesium

Give:

IV magnesium sulfate

for torsades, although case guidance notes that it may not completely suppress chloral-hydrate–driven dysrhythmia. (Royal Children’s Hospital⁠)

β-blockade may still be needed when catecholamine sensitization is driving recurrent ventricular arrhythmia.

Ventricular Tachycardia

For unstable VT:

• Immediate synchronized cardioversion when appropriate

For pulseless VT/VF:

• Defibrillate according to ACLS

Lidocaine has occasionally been successful, but response is inconsistent. (PubMed⁠)

Therefore:

Do not repeatedly cycle through standard antiarrhythmics while ignoring the characteristic catecholamine-sensitive mechanism.

Catecholamines – Important Pitfall

Because chloral hydrate sensitizes the myocardium to catecholamines:

Exogenous β-adrenergic stimulation can precipitate or worsen ventricular dysrhythmias.

Pediatric toxicology guidance therefore advises avoiding catecholamine inotropes when possible in chloral hydrate poisoning. (Royal Children’s Hospital⁠)

One reported severe poisoning switched norepinephrine to the predominantly α-adrenergic agent phenylephrine because of this concern. (PubMed Central (PMC)⁠)

Practical approach

For hypotension:

1. Optimize oxygenation/ventilation
2. Give cautious isotonic fluid if volume responsive
3. Correct dysrhythmias
4. Seek toxicology/critical-care input early

If a vasopressor is necessary, an α-predominant strategy such as phenylephrine may be considered when catecholamine-sensitive ventricular arrhythmias are present.

This is a specialized situation; profound shock requires individualized critical-care management.

4. Hypotension

Possible mechanisms include:

• Myocardial depression
• Dysrhythmia
• Vasodilation
• Sedative toxicity

Give:

• Isotonic crystalloid when clinically fluid responsive

Avoid:

• Unnecessary large fluid loads
• Unnecessary β-adrenergic stimulation

If persistent shock accompanies severe cardiotoxicity, involve:

• Medical toxicology/poison center
• Critical care
• Cardiology

early.

5. Seizures

Treat with:

Benzodiazepines first-line

Examples:

• Lorazepam
• Midazolam
• Diazepam

For refractory seizures consider:

• Phenobarbital
• Propofol in an appropriately intubated patient

Also correct:

• Hypoglycemia
• Hypoxia
• Electrolyte abnormalities

Gastrointestinal Decontamination

Do Not Induce Vomiting

Never induce emesis.

Rapid CNS depression creates substantial aspiration risk.

The old ipecac recommendation is obsolete.

Activated Charcoal

Activated charcoal should not be given routinely.

It may be considered after a substantial recent ingestion only when:

• The potential benefit is meaningful
• The patient is fully alert with intact airway reflexes

or:

• The airway has been protected by intubation

Current chloral-hydrate poisoning guidance specifically considers charcoal unsafe when the airway is not protected. (Royal Children’s Hospital⁠)

Because deterioration may be rapid:

Airway management takes priority over charcoal.

Gastric Lavage

The old routine recommendation:

“Large ingestion + presentation within 1 hour → gastric lavage”

does not reflect contemporary poisoning practice.

Modern toxicology guidance recommends that gastric lavage not be performed systematically after pharmaceutical overdose because outcome benefit is unproven and complications are significant. (PubMed Central (PMC)⁠)

Therefore:

Routine gastric lavage is not recommended.

Only an extraordinary, immediately life-threatening, very recent ingestion with:

• Protected airway
• Appropriate expertise
• Poison-center/medical-toxicology involvement

could justify consideration.

Antidote

There is no established specific antidote.

Management is primarily:

• Airway/ventilation
• Cardiac monitoring
• β-blockade for selected severe dysrhythmias
• Defibrillation/cardioversion when indicated
• Hemodynamic support
• Extracorporeal therapy in exceptional severe cases

Flumazenil

Because chloral hydrate/TCE likely modulate GABA-A signaling, isolated case observations have suggested possible effects from flumazenil.

However:

Flumazenil is not an established antidote for chloral hydrate overdose.

Its efficacy is uncertain, and seizure risk becomes especially problematic when:

• Exposure is mixed
• Chronic sedative dependence exists
• Proconvulsant coingestants are possible

Therefore routine use is not recommended.

Extracorporeal Elimination

Hemodialysis

Chloral hydrate’s active metabolite TCE is dialyzable.

Historical pharmacokinetic cases demonstrate substantial TCE clearance during hemodialysis, including reduction of TCE half-life from approximately:

35 hours → ~6 hours

in one massive overdose. (PubMed⁠)

Another study found high clearance of:

• TCE
• TCE glucuronide
• TCA

with both hemodialysis and hemoperfusion. (PubMed⁠)

When to Consider Hemodialysis

Modern pediatric toxicology guidance suggests considering hemodialysis with:

• Ongoing hemodynamic instability
• Persistent serious dysrhythmias

despite supportive care. (Royal Children’s Hospital⁠)

Additional reasonable considerations include:

• Prolonged profound coma requiring ventilation
• Massive known ingestion with persistent deterioration
• Refractory cardiotoxicity

Important

Evidence is based primarily on:

• Case reports
• Pharmacokinetic studies

There are no validated numerical serum thresholds or modern randomized trials establishing when dialysis must be used.

Thus:

Hemodialysis is a rescue therapy for severe refractory poisoning—not routine treatment.

Hemoperfusion

Charcoal/resin hemoperfusion can also clear TCE.

However:

• Equipment is less widely available
• Hemodialysis is technically simpler in many modern centers
• Hemoperfusion can cause complications including thrombocytopenia

Older comparative pharmacokinetic work found hemodialysis and hemoperfusion similarly efficient, with investigators favoring hemodialysis because of practical safety considerations. (PubMed⁠)

Thus:

If extracorporeal treatment is required, intermittent hemodialysis is generally the more practical modern option.

Forced Diuresis

Forced diuresis is not useful for enhanced elimination.

Do not use it routinely. (PubChem⁠)

Dependence and Withdrawal

Chronic high-dose chloral hydrate use can cause:

• Tolerance
• Psychological dependence
• Physical dependence

Abrupt withdrawal has historically produced a syndrome resembling severe sedative-hypnotic or alcohol withdrawal, including:

• Anxiety
• Tremor
• Agitation
• Delirium
• Hallucinations
• Psychosis
• Seizures

(PubChem⁠)

Therefore:

Chronic heavy users should not automatically have chloral hydrate abruptly discontinued without considering sedative-hypnotic withdrawal.

Modern management would generally use a better-characterized sedative agent and specialist supervision rather than restarting unsupervised chloral hydrate.

Monitoring

Significant poisoning requires:

• Continuous ECG
• Continuous respiratory monitoring
• Frequent blood pressure assessment
• Serial neurologic examination

Monitor for:

• Hypoventilation
• Aspiration
• Ventricular ectopy
• VT/VF
• Hypotension
• Recurrent CNS depression

Electrolytes—especially:

• Potassium
• Magnesium
• Calcium

should be corrected aggressively when arrhythmias are present.

Admission

Hospital admission is appropriate for:

• Significant CNS depression
• Ataxia preventing safe ambulation
• Respiratory depression
• Hypotension
• Ventricular ectopy
• Any significant dysrhythmia
• Seizures
• Large intentional ingestion

ICU care is indicated for:

• Coma
• Mechanical ventilation
• VT/VF
• Recurrent dysrhythmias
• Shock
• Need for extracorporeal treatment

Observation and Disposition

The older blanket:

“4–6 hours asymptomatic → discharge”

should be used cautiously.

Chloral hydrate itself is rapidly converted, but:

TCE has a much longer half-life

and overdose elimination can be prolonged.

A truly small isolated exposure with:

• Normal mental status
• Normal vital signs
• Normal ECG
• No evolving symptoms

may be discharged after an appropriate observation period.

However, significant intentional overdose warrants longer observation because:

• CNS depression can persist
• Cardiotoxicity can be severe
• TCE persists for many hours

Do not discharge until:

• Normal/baseline consciousness
• Normal ventilation
• Stable hemodynamics
• Reassuring ECG
• No recurrent dysrhythmia

Pregnancy

The old FDA Pregnancy Category C system is obsolete.

Published safety data are limited because chloral hydrate is now rarely used therapeutically in many settings.

For acute poisoning:

Maternal stabilization takes priority.

Treat:

• Hypoxia
• Respiratory failure
• Dysrhythmias
• Shock

aggressively.

Historical case literature documents successful maternal and fetal recovery after hemodialysis for severe poisoning during pregnancy. (PubMed⁠)

Breastfeeding

Chloral hydrate and its active metabolite enter breast milk.

Current LactMed guidance states that:

• Occasional/short-term use is unlikely to harm most older infants
• Other sedative-hypnotics are preferred for prolonged use
• Particular caution is warranted in neonates and premature infants

Monitor the infant for:

• Sedation
• Poor feeding
• Poor weight gain

because TCE has a prolonged half-life. (NCBI⁠)

Prognosis

Most uncomplicated exposures recover completely with appropriate supportive care.

Severe poisoning can be rapidly fatal from:

Respiratory failure or malignant ventricular dysrhythmias

Good outcomes are possible even after massive overdose when:

• Airway is secured
• Ventilation is maintained
• Dysrhythmias are recognized promptly
• Extracorporeal treatment is used when necessary

Important Pitfalls

1. Thinking chloral hydrate is simply an old benzodiazepine-like sedative

Its overdose has an unusually important:

Cardiotoxic component

with potentially lethal ventricular dysrhythmias.

2. Ignoring trichloroethanol

The parent drug disappears rapidly, but:

TCE remains active for 8–12 hours or much longer in overdose. (PubMed Central (PMC)⁠)

3. Giving catecholamines reflexively

Chloral hydrate can:

Sensitize the myocardium to catecholamines

and β-adrenergic stimulation may worsen ventricular dysrhythmias. (PubMed Central (PMC)⁠)

4. Missing the characteristic role for β-blockade

Recurrent ventricular dysrhythmias refractory to routine therapy have repeatedly responded to:

Esmolol/propranolol. (PubMed⁠)

Use this as a specialist-directed therapy, not for routine sinus tachycardia.

5. Calling the ethanol interaction merely “disulfiram-like”

The major toxicologic issue is:

Mutually enhanced/prolonged sedative toxicity with increased TCE exposure and impaired ethanol elimination. (ASCPT⁠)

6. Giving charcoal to a somnolent patient

Rapid progression to coma and aspiration makes this dangerous.

Protect the airway first.

7. Performing routine gastric lavage

Modern poisoning practice does not support systematic lavage after pharmaceutical overdose. (PubMed Central (PMC)⁠)

8. Assuming there is no role for dialysis

Severe refractory poisoning is unusual among sedative-hypnotic overdoses because:

TCE can be efficiently removed by hemodialysis. (PubMed⁠)

9. Using hemoperfusion automatically because older texts prefer it

Both methods clear TCE, but modern intermittent:

Hemodialysis is generally more available and practical

and historical comparative data found similar clearance. (PubMed⁠)

10. Forgetting dependence and withdrawal

Chronic use can produce:

• Tolerance
• Dependence
• Delirium
• Psychosis
• Seizures after withdrawal

High-Yield Toxicology Pearls

Chloral hydrate = sedative-hypnotic poisoning with distinctive ventricular cardiotoxicity

Think:

Coma + respiratory depression + ventricular ectopy/VT after old sedative exposure

Key points:

• Chloral hydrate is rapidly converted to trichloroethanol (TCE)
• TCE produces most of the prolonged CNS effects
• Mechanism probably involves GABA-A enhancement
• TCE half-life:
• Usually ~8–12 h
• May extend toward 24–35 h in overdose
• Parent drug toxicity may therefore outlast its brief plasma presence
• Current U.S. conventional chloral hydrate products such as Somnote are discontinued
• Chloral hydrate remains a U.S. Schedule IV substance
• Main acute toxicity:
• CNS depression
• Respiratory depression
• Hypotension
• Ventricular dysrhythmias
• Characteristic cardiac mechanism:
• Myocardial sensitization to catecholamines
• Dysrhythmias may include:
• Bigeminy
• VT
• Torsades
• VF
• Obtain continuous ECG monitoring after significant ingestion
• Airway/ventilation is the main treatment
• Ventricular dysrhythmias may respond especially well to:
• Esmolol
• Propranolol
• Torsades → magnesium + correction of K/Mg + defibrillation when required
• Avoid unnecessary β-adrenergic catecholamine stimulation
• If severe hypotension coexists with arrhythmias, consider specialist-guided α-predominant vasopressor therapy
• Ethanol greatly increases danger:
• More/prolonged TCE
• Longer ethanol effects
• Greater CNS depression
• Do not induce vomiting
• Activated charcoal only for selected large recent ingestions with an intact/protected airway
• Routine gastric lavage is obsolete
• No specific antidote
• Flumazenil is not established therapy
• Severe refractory toxicity can be treated with hemodialysis
• Consider dialysis for:
• Persistent severe dysrhythmias
• Ongoing hemodynamic instability
• Prolonged severe poisoning despite support
• Hemoperfusion can remove TCE but is no longer the practical default
• Forced diuresis is ineffective
• Chronic use can produce sedative-hypnotic dependence and withdrawal

The next chapter can be modernized in the same toxicology-reference format.

Toxicology – Caustics—Basic (Alkaline Corrosives)

Core concept

Strong alkalis cause corrosive injury by saponifying membrane lipids and producing liquefactive necrosis, allowing deep tissue penetration.

The classic injury sequence is:

Strong alkali contact → fat saponification + protein dissolution → liquefactive necrosis → deep esophageal injury → perforation or later stricture

Compared with acids, alkalis classically cause more prominent esophageal injury because many alkaline products are viscous and remain in contact with the esophageal mucosa.

However:

The acid-versus-alkali distinction should not be used to predict injury severity in an individual patient.

Both can cause devastating:

• Esophageal necrosis
• Gastric injury
• Perforation
• Airway edema
• Death

Modern management centers on:

Early airway assessment + resuscitation + injury staging with endoscopy and/or contrast-enhanced CT

There is no specific antidote.

Important Alkaline Caustics

Common clinically important alkalis include:

• Sodium hydroxide — lye/caustic soda
• Potassium hydroxide — caustic potash
• Calcium hydroxide
• Calcium oxide / quicklime
• Ammonia/ammonium hydroxide
• Sodium metasilicate
• Sodium carbonate
• Potassium carbonate
• Trisodium phosphate
• Portland cement
• Some drain cleaners
• Oven cleaners
• Industrial degreasers
• Hair relaxers

Important modernization

The older list includes several compounds that are not equally corrosive simply because they are alkaline or are found in cleaning products.

Corrosive potential depends on:

Concentration + titratable alkalinity + physical form + amount + duration of contact

rather than the chemical name or pH alone.

Household Sources

Potential sources include:

• Drain openers
• Oven cleaners
• Industrial cleaners
• Dishwasher products
• Hair-relaxing products
• Cement/lime products
• Degreasers
• Metal cleaners

Some household detergents are only irritants, whereas concentrated drain cleaners containing sodium or potassium hydroxide can cause profound necrosis after very small ingestions.

Toxic Dose

There is no reliable universal toxic dose.

Only a few milliliters of concentrated sodium or potassium hydroxide may cause major injury.

Risk depends on:

• Concentration
• pH
• Titratable alkalinity
• Volume
• Viscosity
• Solid vs liquid formulation
• Contact duration

pH

A product with:

pH >11–11.5

raises concern for significant alkaline corrosive potential.

But:

pH alone does not determine injury severity.

A high-pH product with low titratable alkalinity may behave differently from concentrated lye with a similar measured pH.

Pathophysiology

Liquefactive Necrosis

Strong bases cause:

Hydroxide ion → lipid saponification + protein dissolution → cellular destruction

This produces:

Liquefaction necrosis

Unlike coagulative necrosis, liquefactive injury does not form an effective protective eschar.

Therefore alkali can continue penetrating:

Mucosa → submucosa → muscularis → adventitia

leading to:

• Deep ulceration
• Vascular thrombosis
• Transmural necrosis
• Perforation

Esophageal Predominance

Alkalis traditionally produce greater esophageal injury because:

• Many are viscous
• They adhere to mucosa
• They may remain in the esophagus longer

This contrasts with strong acids, which often produce substantial gastric injury.

However:

Severe alkaline ingestion can injure the stomach and duodenum as well.

Tissue Evolution

First hours

• Edema
• Erythema
• Necrosis
• Vascular thrombosis

First several days

• Mucosal sloughing
• Inflammation
• Bacterial infiltration
• Progressive tissue weakness

Healing phase

• Granulation
• Collagen deposition
• Fibrosis

leading to:

Esophageal stricture ± gastric outlet obstruction

The injured GI wall can become particularly friable during the healing period, making unnecessary instrumentation hazardous.

Clinical Features

Oropharyngeal

Possible findings include:

• Burning pain
• Lip/tongue burns
• Oral ulceration
• Drooling
• Dysphagia
• Odynophagia
• Hoarseness
• Stridor

Critical pearl

The mouth may look completely normal despite severe esophageal injury.

Absence of oral burns does not safely exclude clinically important GI injury. (NCBI⁠)

Airway

Caustic exposure can cause:

• Supraglottic edema
• Laryngeal edema
• Laryngospasm
• Stridor
• Airway obstruction

Aspiration or inhalation can also cause:

• Bronchospasm
• Chemical pneumonitis
• Pulmonary edema
• ARDS

Warning signs include:

• Progressive hoarseness
• Stridor
• Drooling/inability to handle secretions
• Hypoxemia
• Increasing respiratory effort

Therefore:

A threatened airway should be secured early.

Do not wait until progressive edema makes intubation extremely difficult.

Gastrointestinal

Symptoms may include:

• Dysphagia
• Odynophagia
• Retrosternal pain
• Epigastric pain
• Nausea
• Vomiting
• Hematemesis
• Abdominal tenderness

Severe poisoning can cause:

• Gastrointestinal hemorrhage
• Mediastinitis
• Peritonitis
• Esophageal/gastric perforation
• Shock

Perforation

Suspect transmural injury/perforation with:

• Severe or worsening chest pain
• Severe abdominal pain
• Guarding/rebound
• Subcutaneous emphysema
• Pneumomediastinum
• Pneumoperitoneum
• Fever/sepsis
• Hemodynamic instability
• Rising lactate/metabolic acidosis

This is a:

Surgical emergency

A normal plain radiograph does not reliably exclude serious transmural injury.

Cardiovascular

Severe caustic injury may produce:

• Tachycardia
• Hypotension
• Hemorrhagic shock
• Inflammatory/distributive shock
• Cardiovascular collapse

Shock can result from:

• GI hemorrhage
• Massive third-spacing
• Necrotic tissue injury
• Perforation
• Sepsis

Renal / Metabolic

Possible complications include:

• Metabolic acidosis
• Lactic acidosis
• Acute kidney injury
• Electrolyte abnormalities

These usually indicate:

• Severe tissue necrosis
• Shock
• Hemorrhage

rather than a characteristic direct systemic effect of sodium hydroxide itself.

Skin Exposure

Alkaline solutions may produce surprisingly deep burns because liquefactive necrosis continues while the chemical remains in contact.

Possible manifestations:

• Pain
• Slippery/soapy sensation
• Erythema
• Blistering
• Ulceration
• Deep/full-thickness burn

Portland cement

Wet cement is particularly important because prolonged skin contact may produce:

Delayed deep alkaline burns

sometimes with little early pain.

Calcium Oxide / Dry Lime

Dry quicklime reacts with water:

CaO + H₂O → Ca(OH)₂ + heat

Therefore:

Brush off dry particulate material before beginning copious water irrigation.

Once dry material is removed, irrigate thoroughly.

This principle also applies to contaminated clothing containing large amounts of dry caustic powder.

Ocular Exposure

Alkali eye injuries are especially dangerous because bases can penetrate ocular tissues rapidly.

Possible complications include:

• Conjunctival burns
• Corneal epithelial loss
• Stromal injury
• Limbal ischemia
• Corneal opacification
• Cataract
• Glaucoma
• Globe perforation
• Permanent blindness

Alkali ocular exposure is an emergency requiring immediate irrigation.

Inhalational Exposure

Aerosols, dusts, or ammonia-containing alkaline products may cause:

• Upper-airway irritation
• Cough
• Wheezing
• Bronchospasm
• Laryngospasm
• Pulmonary edema
• Chemical pneumonitis
• ARDS

Patients with significant inhalational exposure require careful observation because respiratory injury may evolve after the initial contact.

Diagnosis

Diagnosis depends on:

Exposure history + physical examination + assessment of injury depth

Do not determine severity from:

• Mouth appearance alone
• Product pH alone
• Reported volume alone

Whenever possible obtain:

• Product name
• Ingredient list
• Concentration
• Amount
• Time of exposure
• Intentional vs accidental exposure

Differential Diagnosis

Consider:

• Acid ingestion
• Button battery ingestion
• Hydrogen peroxide
• Phenol
• Formaldehyde
• Zinc chloride
• Mercuric chloride
• Iron preparations
• Severe GI irritants

Important

Button batteries are a distinct emergency.

Their injury results largely from:

Electrical current → local hydroxide generation → liquefactive necrosis

and they require their own urgent removal algorithm.

Laboratory Testing

Minor exposure

No routine testing may be necessary after a clearly trivial accidental exposure in a completely asymptomatic patient.

Symptomatic/significant exposure

Consider:

• CBC
• Electrolytes
• Bicarbonate
• BUN
• Creatinine
• Glucose

For severe toxicity:

• Blood gas
• Lactate
• PT/INR
• aPTT
• Fibrinogen
• Type and crossmatch
• Liver enzymes

Abnormal:

• Acidosis
• Leukocytosis
• Renal dysfunction
• Lactate

may help identify patients with substantial tissue injury, but no laboratory value replaces direct injury assessment.

Plain Imaging

Chest and abdominal radiographs may identify:

• Pneumomediastinum
• Pleural abnormalities
• Pneumoperitoneum

but:

Normal plain films do not exclude transmural necrosis or perforation.

Contrast-Enhanced CT

Modern management increasingly incorporates:

Contrast-enhanced CT of the neck/chest/abdomen

in significant adult caustic ingestions.

CT can evaluate:

• Esophageal-wall injury
• Gastric injury
• Periesophageal inflammation
• Mediastinal injury
• Intramural gas
• Free air
• Adjacent-organ involvement
• Transmural necrosis

The most important CT feature suggesting irreversible transmural injury is:

Absent post-contrast wall enhancement

WSES guidance considers this an indication for emergency surgical management when convincing transmural necrosis is present. (PubMed Central (PMC)⁠)

CT vs Endoscopy

This is an evolving area.

WSES supports a CT-based approach in adults because CT may be superior for detecting transmural necrosis. (PubMed Central (PMC)⁠)

However, a 2025 comprehensive review concluded that evidence is still insufficient to universally replace EGD; endoscopy remains the predominant first-line assessment in many centers, while CT is increasingly used as a complementary or alternative tool in high-risk adults. (PubMed Central (PMC)⁠)

Therefore:

EGD and CT should be viewed as complementary, not automatically competing, tests.

A useful conceptual distinction:

EGD → mucosal/luminal injury

CT → depth of injury/transmural necrosis + extraluminal structures

Upper Gastrointestinal Endoscopy

EGD remains important after:

• Significant intentional ingestion
• Large/concentrated ingestion
• Drooling
• Dysphagia
• Odynophagia
• Persistent vomiting
• Chest/abdominal pain
• Significant oral/pharyngeal injury
• Other concerning clinical features

When indicated, it is commonly performed:

Within approximately 12–24 hours

after ingestion.

The exact approach depends on local GI, surgical, radiology, and toxicology expertise. (PubMed Central (PMC)⁠)

When EGD May Not Be Necessary

Routine endoscopy is not required after every childhood “taste.”

A patient with a clearly:

• Small accidental exposure
• Low-concentration household product
• Normal examination
• No symptoms
• Normal swallowing

may be managed without invasive evaluation after appropriate risk assessment.

Intentional adult ingestion is substantially different and usually deserves formal assessment.

Zargar Endoscopic Classification

Grade 0

Normal mucosa

Grade I

• Edema
• Hyperemia

Generally excellent prognosis.

Grade IIa

• Friability
• Hemorrhage
• Erosions
• Blisters
• Superficial ulcers
• Exudate

Usually relatively low stricture risk.

Grade IIb

Grade IIa features plus:

Deep or circumferential ulceration

This carries substantial risk of later stricture.

Grade IIIa

Focal necrosis

Grade IIIb

Extensive necrosis

Grade III injury carries major risk of:

• Perforation
• Hemorrhage
• Systemic complications
• Death

Endoscopy cannot always accurately determine whether necrosis extends through the entire wall, which is why CT has become increasingly important. (PubMed Central (PMC)⁠)

Treatment

1. Airway First

Immediately assess:

• Voice
• Secretions
• Stridor
• Respiratory effort
• Oropharyngeal edema
• Oxygenation

If airway edema is progressing:

Intubate early

Ideally use:

• Experienced airway operator
• Video laryngoscopy or fiberoptic techniques as appropriate
• Surgical airway backup

Repeated traumatic attempts can worsen edema and bleeding.

2. Breathing

For inhalational injury:

• Remove from exposure
• Oxygen if hypoxemic
• Inhaled β₂ agonist for bronchospasm

Severe chemical lung injury is managed with:

• Appropriate ventilatory support
• Lung-protective ventilation if ARDS develops

3. Circulation

Establish IV access.

Treat significant volume loss or shock with:

• Isotonic crystalloid when appropriate
• Blood products for significant hemorrhage

If hypotension persists despite adequate resuscitation:

Norepinephrine is generally an appropriate first vasopressor.

4. Do NOT Induce Vomiting

Never induce emesis.

Vomiting causes a second caustic exposure to the esophagus and increases aspiration risk.

Ipecac has no role.

5. Do NOT Neutralize Alkali With Acid

The historical idea of giving:

• Vinegar
• Lemon juice
• Other acids

is dangerous.

Neutralization can cause:

Acid + base reaction → heat generation → additional thermal injury

Therefore:

Do not attempt chemical neutralization.

6. Routine Milk/Water Dilution Is No Longer Recommended

Older texts advise approximately 4 oz of milk or water.

Modern guidance does not recommend routine dilution.

Potential concerns include:

• Vomiting
• Aspiration
• Gastric distention
• No proven clinical outcome benefit

Any theoretical effect would require administration almost immediately after exposure, and supporting human data are poor. (NCBI⁠)

Therefore:

Do not routinely force oral water or milk after caustic ingestion.

7. No Gastric Lavage

Gastric lavage is contraindicated/not routinely appropriate.

It can:

• Re-expose the esophagus
• Cause perforation
• Cause bleeding
• Increase aspiration

8. Activated Charcoal

Activated charcoal has no routine role in isolated alkali ingestion.

Most caustic alkalis are poorly adsorbed, and charcoal may:

• Induce vomiting
• Increase aspiration risk
• Obscure endoscopic visualization

Use charcoal only when there is a separate clinically important charcoal-adsorbable coingestant and the airway is safe.

9. Avoid Blind NG/OG Tube Placement

Blind instrumentation through a severely injured esophagus may cause:

• Bleeding
• Perforation

If enteral access is necessary:

Place the tube under endoscopic or surgical guidance when feasible.

Skin Decontamination

Immediately:

• Remove contaminated clothing
• Remove jewelry
• Remove retained chemical

For liquid alkali:

Copious water irrigation

should begin promptly.

For dry powder/quicklime:

• Brush away dry material first
• Then irrigate copiously

Do not attempt acid neutralization.

Eye Decontamination

Irrigate immediately—before any other detailed examination.

Use:

• Water
• Saline

Remove:

• Contact lenses
• Retained particulate matter

A topical ocular anesthetic may facilitate adequate irrigation when appropriate.

Continue irrigation until the ocular surface approaches physiologic pH and remains stable after irrigation pauses.

Then evaluate:

• Visual acuity
• Corneal epithelial defect
• Limbal ischemia
• Anterior chamber
• Intraocular pressure when appropriate

Significant alkali burns require:

Urgent ophthalmology consultation

Antidote

There is no specific antidote for alkaline caustic poisoning.

Management is based on:

• Immediate decontamination
• Airway support
• Injury assessment
• Surgical management when required
• Treatment of complications

Corticosteroids

Major modernization

The older text recommends corticosteroids for Grade II burns.

This is not supported as routine modern therapy.

A systematic review/meta-analysis of randomized trials found:

No demonstrated significant reduction in esophageal stricture formation with systemic corticosteroids. (PubMed⁠)

Earlier pooled clinical analyses likewise failed to support routine steroid therapy for Grade II caustic burns. (PubMed⁠)

Therefore:

Do not routinely give systemic steroids solely to prevent strictures.

Nuance

Selected pediatric protocols have investigated high-dose corticosteroids in specific Grade IIb injuries, so this remains an area of specialty debate.

If considered, it should involve:

• Pediatric gastroenterology/GI
• Medical toxicology
• Surgery

rather than automatic treatment based simply on “second-degree burn.”

Antibiotics

Routine prophylactic antibiotics are not indicated.

Use antibiotics when there is:

• Perforation
• Mediastinitis
• Peritonitis
• Aspiration pneumonia
• Documented infection
• Severe necrotic injury managed according to a surgical protocol

Antibiotics do not reliably prevent strictures.

Proton-Pump Inhibitors

PPIs are frequently used in significant upper-GI caustic injury.

However:

Evidence that they improve major outcomes or prevent strictures remains limited.

They may be reasonable as adjunctive acid suppression but are not antidotal therapy. (NCBI⁠)

Nutrition

Nutrition should be determined by injury severity.

Grade 0–I / selected IIa

If swallowing is comfortable and there is no significant injury:

• Oral intake may be resumed as clinically appropriate

Grade IIb–III

May require:

• Initial bowel rest
• Carefully planned enteral nutrition
• Jejunal access
• Occasionally parenteral nutrition

The goal is to maintain nutrition while avoiding unnecessary trauma to the injured esophagus.

Surgery

Emergency surgical consultation is required with:

• Perforation
• Peritonitis
• Mediastinitis
• Uncontrolled hemorrhage
• Extensive transmural necrosis
• Progressive shock attributable to GI necrosis

CT evidence of:

Absent mural enhancement

strongly suggests full-thickness necrosis and may indicate emergency resection. (PubMed Central (PMC)⁠)

The old recommendation to operate simply because endoscopy shows “Grade III” is too simplistic; depth of necrosis and clinical/CT findings now play a major role.

Stricture Formation

The most important delayed GI complication is:

Esophageal stricture

Risk is greatest after:

• Grade IIb injury
• Grade III injury

Strictures usually become clinically apparent after the acute healing phase, commonly beginning approximately:

3 weeks onward

Symptoms include:

• Progressive dysphagia
• Food impaction
• Regurgitation
• Weight loss

Stricture Management

First-line treatment for established esophageal strictures is generally:

Endoscopic dilation

using:

• Balloon dilation
• Bougie dilation

Repeat procedures are often necessary.

Complex/refractory strictures may require:

• Advanced endoscopic techniques
• Feeding access
• Surgical reconstruction

Routine prophylactic stenting to prevent strictures is not standard care.

Gastric Outlet Obstruction

Deep gastric burns can heal with fibrosis and produce:

• Early satiety
• Postprandial vomiting
• Weight loss
• Gastric retention

This may appear several weeks after the ingestion.

Long-Term Cancer Risk

Previous severe caustic injury is associated with increased risk of:

Esophageal squamous cell carcinoma

usually many years to decades later.

Published literature commonly reports development approximately:

30–40 years after injury, although the exact magnitude of risk is uncertain. (PubMed Central (PMC)⁠)

The older claim of a precise fold-increase should be interpreted cautiously because much of the evidence comes from older observational series.

Surveillance

Long-term surveillance is reasonable after major caustic esophageal injury/stricture, but:

There is no universally validated endoscopic surveillance schedule.

Follow-up should be individualized with gastroenterology.

Occupational Exposure – Sodium Hydroxide

The older workplace section requires one correction.

OSHA

PEL: 2 mg/m³ as an 8-hour TWA

NIOSH

REL: 2 mg/m³ CEILING

ACGIH

TLV: 2 mg/m³ CEILING

NIOSH IDLH

10 mg/m³

(OSHA⁠)

Thus, the old statement:

“ACGIH TLV TWA 2 mg/m³”

is incorrect; ACGIH lists a ceiling value.

Monitoring

Patients with significant injury should be monitored for:

• Airway edema
• Hypoxemia
• Bronchospasm
• GI hemorrhage
• Perforation
• Shock
• Metabolic acidosis
• Renal injury

Serial:

• Vital signs
• Respiratory examinations
• Abdominal examinations
• Laboratory studies

are appropriate according to severity.

Admission

Admit patients with:

• Intentional significant ingestion
• Drooling
• Dysphagia/odynophagia
• Persistent vomiting
• Chest/abdominal pain
• Stridor
• Respiratory distress
• Hematemesis
• Significant oral injury after concerning exposure
• Abnormal EGD/CT
• Grade IIb/III injury
• Hemodynamic instability

ICU care is appropriate for:

• Threatened airway
• Respiratory failure
• Shock
• Major hemorrhage
• Full-thickness necrosis
• Perforation

Disposition

A fixed historical:

“6-hour observation = safe discharge”

should not replace clinical risk assessment.

A patient after a clearly trivial accidental taste may often be discharged when:

• Completely asymptomatic
• Normal examination
• Swallowing normally
• Tolerating oral intake
• Exposure is clearly low-risk
• Reliable home observation is available

Intentional or concentrated alkali exposures deserve a much lower threshold for:

• CT
• Endoscopy
• Admission
• Multidisciplinary evaluation

Prognosis

Grade 0–I

Usually excellent.

Grade IIa

Generally favorable.

Grade IIb

High risk of:

• Esophageal stricture
• Prolonged nutritional problems

Grade III

High risk of:

• Hemorrhage
• Transmural necrosis
• Perforation
• Mediastinitis/peritonitis
• Shock
• Stricture
• Death

A key determinant of survival is early recognition of:

Full-thickness necrosis before catastrophic perforation occurs.

Important Pitfalls

1. Assuming “basic pH” automatically means a dangerous caustic

Corrosive potential depends on:

Concentration + titratable alkalinity + contact time

not pH alone.

2. Using pH 11.5 as an absolute cutoff

A pH above approximately 11–11.5 raises concern, but:

There is no universal safe pH threshold.

Evaluate the actual product and exposure.

3. Assuming a normal mouth means a normal esophagus

Absence of oral burns does not exclude severe distal injury.

(NCBI⁠)

4. Waiting for obvious airway obstruction

Progressive caustic edema can make late intubation extremely difficult.

Stridor/hoarseness/progressive edema → early airway planning.

5. Inducing vomiting

Never induce emesis.

6. Neutralizing alkali with acid

Do not give:

• Vinegar
• Citrus juice
• Other acidic neutralizers

The reaction may generate heat and worsen injury.

7. Automatically giving milk or water

Routine oral dilution is no longer recommended because clinical benefit is unproven and vomiting/distention may occur. (NCBI⁠)

8. Giving activated charcoal

Charcoal is generally not useful for isolated sodium/potassium hydroxide ingestion and may interfere with management.

9. Performing gastric lavage

Routine gastric lavage has no role.

10. Blindly inserting a nasogastric tube

Severely injured tissue may perforate.

Use guided placement when enteral access is required.

11. Automatically giving steroids for Grade II burns

Modern evidence does not show reliable prevention of strictures. (PubMed⁠)

12. Giving prophylactic antibiotics to everyone

Antibiotics are reserved for:

• Infection
• Perforation
• Mediastinitis/peritonitis
• Selected severe necrotic cases

13. Treating CT and EGD as interchangeable

They answer somewhat different questions:

EGD → mucosal injury

CT → transmural/extra-esophageal injury

A 2025 review concludes that the evidence is not yet sufficient to universally replace EGD with CT. (PubMed Central (PMC)⁠)

14. Assuming Grade III endoscopy automatically mandates resection

Modern surgical decision-making relies heavily on:

• Clinical status
• CT evidence of transmural necrosis
• Perfusion
• Perforation

not mucosal appearance alone.

15. Irrigating dry quicklime without first removing particulate

Dry calcium oxide reacts exothermically with water.

Brush off dry material first → then irrigate.

16. Missing delayed complications

Patients can initially recover and later develop:

• Esophageal stricture
• Gastric outlet obstruction
• Nutritional problems

17. Forgetting long-term cancer risk

Severe caustic injury/stricture increases the later risk of:

Esophageal squamous cell carcinoma

often decades later. (PubMed Central (PMC)⁠)

High-Yield Toxicology Pearls

Alkaline caustics = liquefaction necrosis with potentially deep tissue penetration

Think:

Lye ingestion → drooling/dysphagia + chest pain → deep esophageal injury ± perforation

Key points:

• Strong alkalis cause liquefactive necrosis
• Mechanism:
• Fat saponification
• Protein dissolution
• Deep tissue penetration
• Common agents:
• NaOH
• KOH
• Caustic drain/oven cleaners
• Cement/lime
• Hair relaxers
• pH >11–11.5 raises concern but is not an absolute toxicity threshold
• Concentration and titratable alkalinity matter
• Alkalis classically injure the esophagus
• Severe exposures may also injure stomach/duodenum
• Normal oral examination does not exclude esophageal injury
• Main emergency priorities:
• Airway
• Hemodynamic support
• Injury staging
• Progressive hoarseness/stridor → early intubation
• Do not induce vomiting
• Do not neutralize with acid
• Routine milk/water dilution is not recommended
• Activated charcoal has no routine role
• Gastric lavage has no role
• Avoid blind NG placement
• Significant exposure → EGD and/or contrast CT
• EGD is commonly performed within 12–24 h
• CT is particularly valuable for detecting transmural necrosis
• Absent mural enhancement on CT → major concern for full-thickness necrosis
• Grade IIb/III injury → high stricture risk
• Emergency surgery for:
• Perforation
• Mediastinitis/peritonitis
• Full-thickness necrosis
• Major hemorrhage
• Progressive shock
• Routine systemic corticosteroids do not reliably prevent strictures
• Routine prophylactic antibiotics are not indicated
• Esophageal strictures usually emerge weeks later
• First-line established-stricture therapy → endoscopic dilation
• Severe prior injury carries a later esophageal SCC risk
• Sodium hydroxide occupational limits:
• OSHA: 2 mg/m³ TWA
• NIOSH: 2 mg/m³ ceiling
• ACGIH: 2 mg/m³ ceiling
• NIOSH IDLH: 10 mg/m³
• No specific antidote

I can keep the next toxicology chapter in this same modernized, high-yield format.

Toxicology – Caustics—Acidic

Core concept

Strong acids cause immediate chemical injury to skin, eyes, respiratory mucosa, and the gastrointestinal tract.

The major acute hazards are:

Airway edema + esophageal/gastric necrosis + hemorrhage + perforation + shock

A useful sequence is:

Strong-acid contact → protein denaturation/coagulative necrosis → mucosal ulceration/necrosis → edema/bleeding → perforation or later stricture

However, the traditional statement that acids cause only superficial coagulation necrosis while alkalis cause deep liquefaction is an oversimplification.

Concentrated acids can produce profound transmural esophageal and gastric necrosis.

Modern management centers on:

Airway protection + resuscitation + early assessment of injury depth with endoscopy and/or contrast-enhanced CT

There is no specific antidote.

Important terminology

Simply having a:

pH <7

does not make a substance clinically “caustic.”

Many weak acids encountered in foods are harmless.

The potential for corrosive injury depends on:

• Concentration
• pH
• Titratable acidity
• Volume ingested
• Contact time
• Viscosity
• Chemical composition
• Solid vs liquid formulation

Thus:

Concentrated strong acid ≠ ordinary acidic liquid

Important acidic caustics

Examples include:

• Hydrochloric acid
• Sulfuric acid
• Nitric acid
• Phosphoric acid
• Concentrated acetic acid / glacial acetic acid
• Formic acid
• Oxalic acid

Special acids with important systemic toxicities are often managed separately, particularly:

• Hydrofluoric acid
• Chromic acid
• Boric acid
• Selenium-containing acids

Common sources

Household and industrial products include:

• Toilet-bowl cleaners
• Metal cleaners
• Rust removers
• Descaling agents
• Battery acid
• Industrial cleaning solutions
• Laboratory reagents
• Metal-pickling solutions
• Fertilizer/chemical manufacturing
• Etching and engraving products

The exact commercial formulation matters because products may contain:

• Additional corrosives
• Oxidizers
• Metals
• Surfactants
• Solvents

Toxic dose

There is no useful universal toxic dose.

Severity depends much more on:

Agent × concentration × volume × contact time

than on a simple number of milliliters.

A small amount of a highly concentrated industrial acid may produce devastating injury, while a larger exposure to a weakly acidic household solution may produce little damage.

Intentional ingestions generally carry much higher risk because they involve:

• Larger volumes
• Higher concentrations
• Longer contact

Pathophysiology

Gastrointestinal injury

Strong acids cause:

H⁺-mediated protein denaturation → coagulative necrosis

with:

• Edema
• Erosion
• Ulceration
• Thrombosis of small vessels
• Eschar formation

Classically, acids were thought to injure the stomach more than the esophagus because:

• Liquids transit the esophagus rapidly
• Pylorospasm may retain acid in the stomach

However:

Severe esophageal injury absolutely can occur after acid ingestion.

Do not use the acid-vs-alkali distinction to determine whether endoscopy is needed.

Tissue evolution

Caustic injury evolves over time.

Early:

• Edema
• Hyperemia
• Thrombosis
• Necrosis

Over subsequent days:

• Mucosal sloughing
• Inflammation
• Bacterial invasion
• Granulation tissue

The damaged GI wall becomes mechanically weak during the healing phase, increasing concern for perforation after instrumentation.

Later:

Fibrosis → esophageal stricture and/or gastric outlet obstruction

Respiratory injury

Acid fumes or aspiration can cause:

Upper-airway irritation → laryngeal edema

and:

Lower-airway irritation → bronchospasm → chemical pneumonitis → ARDS

Nitric acid exposure deserves particular caution because associated nitrogen oxides can cause significant delayed pulmonary injury.

Clinical features

HEENT / Oropharyngeal

Possible findings include:

• Oral pain
• Lip/tongue burns
• Oral ulceration
• Drooling
• Dysphonia
• Hoarseness
• Dysphagia
• Odynophagia
• Stridor

Critical pitfall

Absence of visible oral burns does not exclude severe esophageal or gastric injury.

Oropharyngeal examination cannot reliably grade distal injury.

Airway

Warning signs include:

• Hoarse voice
• Stridor
• Drooling
• Progressive swelling
• Respiratory distress
• Hypoxemia
• Inability to handle secretions

Airway edema can progress rapidly.

Therefore:

Secure a threatened airway early rather than waiting until intubation becomes impossible.

Gastrointestinal

Possible manifestations include:

• Severe mouth/throat burning
• Retrosternal pain
• Epigastric pain
• Dysphagia
• Odynophagia
• Vomiting
• Hematemesis
• Abdominal tenderness

Severe injury may progress to:

• GI hemorrhage
• Mediastinitis
• Peritonitis
• Perforation
• Shock

Perforation

Suspect esophageal or gastric perforation with:

• Sudden severe chest/abdominal pain
• Peritoneal signs
• Subcutaneous emphysema
• Pneumomediastinum
• Free intraperitoneal air
• Fever/sepsis
• Hemodynamic collapse

This requires:

Immediate surgical evaluation

Cardiovascular

Severe exposures may cause:

• Tachycardia
• Hypotension
• Hemorrhagic shock
• Distributive/inflammatory shock
• Cardiovascular collapse

Shock may result from:

• GI hemorrhage
• Third-spacing
• Tissue necrosis
• Perforation/sepsis

Metabolic

Severe poisoning may cause:

• Lactic acidosis
• High anion-gap metabolic acidosis
• Hyperkalemia
• Acute kidney injury

Some specific acids produce additional systemic metabolic abnormalities.

Acid-specific systemic toxicities

Concentrated acetic acid

Severe ingestion may cause:

• Intravascular hemolysis
• Hemoglobinuria
• AKI
• DIC
• Hepatic injury

Formic acid

May cause:

• Severe metabolic acidosis
• Hemolysis
• Multiorgan injury

Oxalic acid

Can bind calcium and produce:

• Hypocalcemia
• Tetany
• Dysrhythmias
• Calcium oxalate nephropathy
• AKI

Phosphoric acid

Large systemic exposures may produce:

• Hyperphosphatemia
• Secondary hypocalcemia

Thus:

Not every acidic caustic is merely a local burn.

Identify the precise acid whenever possible.

Dermatologic exposure

Acid skin exposure may range from:

• Erythema
• Pain
• Superficial chemical burn

to:

• Deep dermal necrosis
• Full-thickness injury

Concentrated acids can continue to cause injury while chemical remains on the skin or clothing.

Ocular exposure

The eye is particularly vulnerable.

Possible injury includes:

• Conjunctivitis
• Corneal epithelial defects
• Corneal ulceration
• Stromal damage
• Corneal opacification
• Perforation
• Permanent blindness

This is an ocular emergency.

Diagnosis

Diagnosis is based on:

Known/suspected corrosive exposure + clinical evaluation + assessment of tissue injury

Do not rely on:

• Oral appearance alone
• pH of the product alone
• Amount reported alone

Initial investigations

For a minor asymptomatic exposure, laboratory testing may not be necessary.

For significant or symptomatic exposure consider:

• CBC
• Electrolytes
• Bicarbonate
• BUN/creatinine
• Glucose

For severe poisoning:

• Blood gas
• Lactate
• PT/INR
• aPTT
• Fibrinogen
• Liver enzymes
• Type and crossmatch

Agent-specific testing may include:

• Calcium
• Phosphate
• Hemolysis profile

depending on the acid involved.

Imaging

Plain radiographs

Chest/abdominal radiographs may demonstrate:

• Pneumomediastinum
• Pneumoperitoneum
• Pleural abnormalities

but a normal radiograph does not exclude serious injury.

Contrast-enhanced CT

Modern management increasingly uses:

Contrast-enhanced CT of the neck/chest/abdomen

in severe caustic ingestion.

CT can evaluate:

• Esophageal wall enhancement
• Transmural necrosis
• Gastric necrosis
• Mediastinal injury
• Perforation
• Adjacent-organ injury

A particularly concerning finding is:

Loss of mural enhancement → possible full-thickness necrosis

which may indicate a need for emergency surgery. WSES guidance supports CT-based emergency assessment, particularly for identifying transmural injury.

Current nuance

There is still debate over whether CT should completely replace endoscopy.

A 2025 review found that although CT is increasingly valuable—especially for detecting deep necrosis—EGD remains the predominant first-line assessment in many centers, and evidence is not yet sufficient to universally replace endoscopy with CT.

Thus:

EGD and CT are complementary tools, with local expertise determining the exact algorithm.

Upper GI endoscopy

EGD remains a central method for grading mucosal injury.

Strongly consider EGD after:

• Intentional ingestion
• Significant deliberate exposure
• Drooling
• Dysphagia/odynophagia
• Vomiting
• Oral/pharyngeal burns
• Chest or abdominal pain
• Inability to tolerate liquids
• Other concerning symptoms

Current reviews generally recommend performing EGD:

Within approximately 24 hours

when indicated.

When endoscopy may be deferred

An asymptomatic patient after a clearly:

• Accidental
• Small-volume
• Low-concentration

exposure, with:

• No oral injury
• Normal examination
• Ability to swallow normally

may not require routine EGD.

This decision should consider the actual agent and exposure reliability.

Endoscopy cautions

Endoscopy requires particular caution when there is:

• Suspected perforation
• Hemodynamic instability
• Severe airway compromise
• Extensive necrosis

In these situations:

Resuscitation and CT/surgical evaluation take priority.

Zargar endoscopic classification

Grade 0

Normal mucosa

Grade I

• Edema
• Hyperemia

Generally low risk of late stricture.

Grade IIa

• Friability
• Hemorrhage
• Erosions
• Blisters
• Superficial ulcers
• Exudates

Stricture risk is usually low.

Grade IIb

Grade IIa findings plus:

Deep or circumferential ulceration

High risk of stricture.

Grade IIIa

Focal areas of necrosis

High risk of stricture and perforation.

Grade IIIb

Extensive necrosis

Very high risk of:

• Perforation
• Systemic complications
• Death

These grades remain useful for prognosis, although CT may better assess whether injury is actually transmural.

Treatment

1. Airway first

Assess immediately for:

• Stridor
• Hoarseness
• Drooling
• Oropharyngeal edema
• Progressive respiratory distress

When airway compromise is anticipated:

Intubate early

Ideally use:

• Experienced airway personnel
• Video or fiberoptic techniques as appropriate
• Surgical-airway backup

because edema and distorted anatomy can make later airway control very difficult.

2. Circulation

Establish IV access.

For shock:

• Give isotonic crystalloid when appropriate
• Transfuse blood products for significant hemorrhage

Persistent hypotension despite adequate resuscitation generally warrants:

Norepinephrine

rather than the older routine preference for dopamine.

3. Do NOT induce vomiting

Never induce emesis.

Re-exposure of the esophagus can:

• Worsen injury
• Increase aspiration risk

Ipecac has no role.

4. Do NOT neutralize

Do not give:

• Sodium bicarbonate after acid ingestion
• Other alkaline neutralizing agents

Neutralization can produce:

Exothermic reaction → additional thermal injury

and unpredictable gas generation.

Modern guidance does not support therapeutic neutralization.

5. Routine milk/water dilution is no longer recommended

The older recommendation:

“Give 4–8 oz milk or water within 30 minutes”

is no longer standard clinical practice.

Possible problems include:

• Vomiting
• Gastric distention
• Aspiration
• Lack of demonstrated human benefit

Current toxicology guidance states that dilution might theoretically help only within the first few minutes but lacks evidence and is not routinely recommended.

Thus:

Do not routinely force oral dilution after significant caustic ingestion.

6. No activated charcoal

Activated charcoal is generally not indicated for isolated acid ingestion because:

• Acids are poorly adsorbed
• Charcoal can provoke vomiting
• Aspiration is dangerous
• It may obscure subsequent endoscopy

Modern charcoal guidance specifically lists acids and alkalis among substances not meaningfully adsorbed by activated charcoal.

Use charcoal only for a clinically important separate coingestant when its benefits clearly outweigh the risks.

7. No gastric lavage

Gastric lavage is contraindicated/routinely avoided.

It can:

• Re-expose the esophagus
• Cause perforation
• Cause aspiration

There is no routine role for lavage after caustic acid ingestion.

8. Avoid blind NG/OG tube insertion

Blind insertion may:

• Perforate injured tissue
• Increase bleeding

If enteral access is required:

Placement should generally be performed under endoscopic or surgical guidance.

Modern reviews recommend avoiding blind NG placement because of perforation risk.

Skin decontamination

Immediately:

• Remove contaminated clothing/jewelry
• Brush away dry chemical if applicable
• Irrigate skin with copious water

Continue irrigation until all residual chemical is removed.

Exception

Agent-specific exceptions may exist—for example hydrofluoric acid has additional specific treatment—and should be managed separately.

Ocular decontamination

Immediately irrigate with:

• Water
• Normal saline

Do not delay irrigation while searching for a special solution.

Continue copiously and reassess:

Conjunctival-sac pH

after irrigation, allowing a brief pause before measurement to avoid falsely measuring the irrigant.

Continue until physiologic pH is restored and remains stable.

Significant ocular burns require urgent:

Ophthalmology evaluation

Inhalational exposure

Move patient to fresh air.

Provide:

• Oxygen for hypoxemia
• Bronchodilator for bronchospasm

Patients with:

• Stridor
• Progressive edema
• Hypoxemia
• Significant respiratory distress

require aggressive airway/respiratory management.

Chemical pneumonitis or ARDS is treated supportively with lung-protective ventilation when required.

Proton-pump inhibitors

PPIs are commonly given after significant upper GI caustic injury.

However:

Evidence that PPIs change major outcomes such as stricture formation is limited.

They may be reasonable for:

• Significant mucosal injury
• Stress-ulcer/acid suppression

but should not be described as an antidote.

Current literature regards their definitive role as uncertain.

Corticosteroids

Major modernization

The older text suggests steroids should be considered for second-degree burns.

Routine systemic corticosteroids are now:

NOT recommended for prevention of caustic esophageal strictures

A systematic review/meta-analysis of randomized trials found no significant reduction in stricture formation with corticosteroid therapy.

A broader pooled analysis likewise failed to support routine steroids in grade II burns.

Nuance

Some pediatric/selected protocols have investigated high-dose steroids for grade IIb injury, but this remains controversial.

Therefore:

Do not routinely prescribe steroids solely to prevent strictures.

Any selected use should involve:

• Gastroenterology
• Toxicology
• Surgery/pediatric GI as appropriate

Antibiotics

Routine prophylactic antibiotics are not indicated for uncomplicated caustic injury.

Use antibiotics when there is:

• Perforation
• Mediastinitis
• Peritonitis
• Aspiration pneumonia
• Documented/suspected infection
• Selected severe necrotic injury according to surgical protocol

Do not give antibiotics simply because a caustic agent was swallowed.

Nutrition

Nutrition should be individualized according to injury severity.

Mild injury

Patients with:

• Grade 0/I or selected IIa injury
• Ability to swallow normally
• No significant pain/vomiting

may resume oral intake as clinically appropriate.

Severe injury

Grade IIb/III injury may require:

• NPO initially
• Enteral feeding through carefully placed access
• Jejunal feeding
• Occasionally parenteral nutrition

The modern goal is:

Use the gut when safely possible rather than prolonged unnecessary starvation.

Emergency surgery

Immediate surgical consultation is required for evidence of:

• Perforation
• Peritonitis
• Mediastinitis
• Uncontrolled hemorrhage
• Extensive transmural necrosis
• Progressive abdominal catastrophe
• Refractory shock attributable to GI necrosis

Contrast CT evidence of:

Absent esophageal/gastric wall enhancement

is a major sign suggesting full-thickness necrosis and can guide urgent surgical management.

Acid-specific treatment

Individual acids may require additional management.

For example:

Oxalic acid

Monitor/treat:

• Hypocalcemia
• Dysrhythmias
• AKI

Concentrated acetic/formic acid

Monitor:

• Hemolysis
• Hemoglobin
• LDH
• Haptoglobin
• Bilirubin
• Renal function
• Coagulation

Phosphoric acid

Monitor:

• Phosphate
• Calcium
• Renal function

Hydrofluoric acid

Requires its own emergency management because:

Fluoride toxicity → hypocalcemia/hypomagnesemia + dysrhythmias

and calcium therapy may be lifesaving.

Antidote

There is no general antidote for strong-acid caustic injury.

Treatment is:

• Immediate decontamination
• Airway management
• Hemodynamic support
• Assessment of injury depth
• Surgical treatment when required
• Management of acid-specific systemic toxicity

Stricture formation

The most important delayed GI complication is:

Esophageal stricture

Risk is greatest after:

• Grade IIb injury
• Grade III injury

Symptoms may appear approximately:

3 weeks or later

after ingestion.

Symptoms include:

• Progressive dysphagia
• Food sticking
• Regurgitation
• Weight loss

Gastric outlet obstruction

Deep gastric injury may heal with fibrosis producing:

• Early satiety
• Postprandial vomiting
• Weight loss
• Gastric retention

This may develop within several weeks; older series commonly describe onset around 5–6 weeks after severe injury.

Stricture treatment

Established esophageal strictures are generally managed with:

Endoscopic dilation

using:

• Balloon dilators
• Bougie dilation

Repeat procedures are often required.

Complex/refractory strictures may require:

• Advanced endoscopic therapy
• Feeding access
• Surgical reconstruction

Routine prophylactic esophageal stenting solely to prevent strictures is not standard practice.

Long-term cancer risk

Severe caustic injury is associated with an increased long-term risk of:

Esophageal squamous cell carcinoma

often decades after the original exposure.

Expert reviews describe cancer developing typically around:

10–40 years later

although the exact magnitude of risk is uncertain.

Some experts suggest surveillance endoscopy beginning approximately:

10–20 years after severe caustic injury

with repeat examinations every few years, but:

There is no universally validated surveillance schedule.

Occupational carcinogenicity

The old text broadly states:

“Acid mists are associated with laryngeal cancer.”

The more precise modern statement is:

Occupational exposure to strong inorganic acid mists is carcinogenic to humans (IARC Group 1), with sufficient evidence for laryngeal cancer.

Historically this classification was strongly associated with sulfuric-acid–containing mists.

This does not mean every brief exposure to any household acid carries a meaningful cancer risk.

Occupational limits – Hydrochloric Acid

Current NIOSH/OSHA limits:

NIOSH REL ceiling: 5 ppm (7 mg/m³)

OSHA PEL ceiling: 5 ppm (7 mg/m³)

NIOSH IDLH: 50 ppm

The old numerical HCl workplace limits remain broadly accurate.

Occupational limits – Nitric Acid

Current values:

NIOSH REL TWA: 2 ppm (5 mg/m³)

NIOSH STEL: 4 ppm (10 mg/m³)

OSHA PEL TWA: 2 ppm (5 mg/m³)

NIOSH IDLH: 25 ppm

Correction to the old text

The 4-ppm STEL is a NIOSH recommendation, not part of the current federal OSHA PEL.

Monitoring

Patients with significant injury require monitoring for:

• Airway edema
• Respiratory failure
• Hemorrhage
• Perforation
• Shock
• Electrolyte abnormalities
• AKI

Severe injury generally warrants:

• ICU-level monitoring
• Gastroenterology consultation
• Surgical consultation

depending on findings.

Admission

Admit patients with:

• Significant intentional ingestion
• Drooling
• Dysphagia/odynophagia
• Oral/pharyngeal burns plus concerning exposure
• Stridor
• Respiratory symptoms
• Significant chest/abdominal pain
• Hematemesis
• Hemodynamic instability
• Abnormal CT/EGD
• Grade IIb or III injury

ICU care is appropriate for:

• Threatened airway
• Respiratory failure
• Shock
• Severe bleeding
• Full-thickness necrosis
• Perforation

Disposition

Patients with a clearly trivial accidental exposure may be discharged when:

• Completely asymptomatic
• Able to eat/drink normally
• Normal examination
• No concerning product characteristics
• Reliable observation is available

For significant exposure:

Do not use an arbitrary fixed observation period as a substitute for risk assessment.

Intentional ingestions generally deserve formal GI injury assessment even when symptoms initially appear mild.

Prognosis

Grade 0–I

Usually excellent.

Grade IIa

Generally favorable, with low stricture risk.

Grade IIb

Substantial risk of:

• Esophageal stricture
• Nutritional complications

Grade III

High risk of:

• Hemorrhage
• Perforation
• Mediastinitis/peritonitis
• Shock
• Stricture
• Death

Outcome depends heavily on recognizing transmural necrosis before perforation occurs.

Important Pitfalls

1. Defining a caustic simply as “pH <7”

Acidity alone does not determine corrosive potential.

Concentration and titratable acidity matter greatly.

2. Assuming acids only injure the stomach

Acids may produce:

Severe esophageal as well as gastric injury.

3. Using oral burns to rule injury in or out

The mouth may look normal despite serious distal injury.

4. Waiting too long to secure the airway

Progressive laryngeal edema can make later intubation extremely difficult.

Hoarseness + stridor + progressive swelling → early airway intervention.

5. Inducing vomiting

Never induce emesis.

6. Neutralizing acid with alkali

Never routinely neutralize.

The reaction may generate heat and worsen injury.

7. Automatically giving milk or water

The old 4–8 oz dilution recommendation is no longer routine modern practice.

Benefit is unproven and adverse effects are possible.

8. Giving activated charcoal

Charcoal poorly adsorbs acids and can interfere with endoscopy.

Routine charcoal is contraindicated/not useful.

9. Performing gastric lavage

Caustic injury + instrumentation = increased perforation risk.

Routine lavage has no role.

10. Blindly inserting an NG tube

Use endoscopic/surgical guidance when GI access is necessary.

11. Giving routine steroids for grade II injury

Modern evidence does not demonstrate consistent prevention of strictures.

12. Giving prophylactic antibiotics to everyone

Antibiotics are for:

• Infection
• Perforation
• Selected severe necrosis

not routine uncomplicated exposure.

13. Treating EGD and CT as competitors

Modern severe-ingestion assessment often uses them complementarily:

EGD → luminal/mucosal grading

Contrast CT → depth/transmural necrosis + adjacent structures

14. Missing acid-specific systemic effects

Think beyond the burn:

• Oxalic → hypocalcemia/renal injury
• Acetic/formic → hemolysis/systemic toxicity
• Phosphoric → hyperphosphatemia
• HF → life-threatening fluoride toxicity

15. Forgetting long-term follow-up

Deep injuries can produce:

• Strictures
• Gastric outlet obstruction
• Long-term esophageal cancer risk

even after the acute episode resolves.

High-Yield Toxicology Pearls

Acid caustic ingestion = airway + GI necrosis problem

Think:

Drooling/dysphagia + chest/abdominal pain after strong acid → significant corrosive injury until assessed

Key points:

• “pH <7” alone does not define a dangerous caustic
• Strong acids classically cause coagulative necrosis
• Concentrated acids can still cause deep transmural injury
• Gastric injury is common, but severe esophageal injury also occurs
• Normal mouth does not exclude severe esophageal/gastric burns
• Threatened airway → early intubation
• Do not induce vomiting
• Do not neutralize with alkali
• Routine milk/water dilution is no longer recommended
• Activated charcoal is not useful for acids
• Gastric lavage is contraindicated/not routine
• Avoid blind NG placement
• Significant symptomatic or intentional ingestion → early GI injury assessment
• EGD is generally performed within ~24 h when indicated
• Contrast-enhanced CT is especially valuable for:
• 
  
• Suspected deep necrosis
• Perforation
• Surgical decision-making
• CT finding of absent wall enhancement suggests transmural necrosis
• Zargar IIb/III injury → high stricture risk
• Emergency surgery for:
• 
  
• Perforation
• Peritonitis/mediastinitis
• Full-thickness necrosis
• Uncontrolled hemorrhage
• Routine corticosteroids do not reliably prevent strictures
• Routine prophylactic antibiotics are not indicated
• Strictures may become symptomatic ~3 weeks or later
• Established strictures → endoscopic dilation
• Severe previous caustic injury carries increased long-term esophageal SCC risk
• Occupational strong inorganic acid mists are IARC Group 1 carcinogens
• HCl:
• 
  
• OSHA/NIOSH ceiling 5 ppm
• IDLH 50 ppm
• Nitric acid:
• 
  
• OSHA/NIOSH TWA 2 ppm
• NIOSH STEL 4 ppm
• IDLH 25 ppm
• There is no general antidote

Toxicology – Carisoprodol

Core concept

Carisoprodol is a centrally acting sedative muscle relaxant that is metabolized to the longer-acting sedative-hypnotic meprobamate.

The characteristic overdose syndrome is:

CNS depression + ataxia → respiratory depression/coma ± hypotension

However, unlike a simple sedative overdose, carisoprodol can also cause:

• Agitation
• Myoclonus or abnormal movements
• Seizures
• Delirium
• Serotonergic features

Severe poisoning is especially dangerous when combined with:

Opioids + benzodiazepines + alcohol or other CNS depressants

because respiratory-depressant effects are additive. Current labeling documents fatal overdoses both from carisoprodol alone and particularly in multidrug exposures.

The main treatment is:

Airway protection + ventilation + supportive cardiovascular care

There is no established specific antidote.

Current Forms and Uses

Carisoprodol remains available as an oral prescription muscle relaxant.

Current U.S. labeling recommends:

250–350 mg orally three times daily and at bedtime

for the relief of discomfort associated with:

Acute painful musculoskeletal conditions

Treatment should be limited to:

2–3 weeks

because longer-term effectiveness has not been established and dependence/abuse become increasingly important concerns.

Pediatric use

The older text states that the drug is not recommended below age 12.

Current labeling states:

Safety, efficacy, and pharmacokinetics have not been established in patients <16 years.

Controlled Substance / Abuse Potential

In the United States, carisoprodol is a:

Schedule IV controlled substance

and has recognized potential for:

• Abuse
• Misuse
• Dependence
• Diversion
• Withdrawal

This is clinically important because many severe overdoses occur in people also using:

• Opioids
• Benzodiazepines
• Alcohol
• Other sedatives

A 2025 UK government review similarly emphasized increased overdose danger when carisoprodol is combined with opioids or benzodiazepines.

Combination Products

Carisoprodol has historically been marketed in combination preparations containing:

• Aspirin/salicylate
• Aspirin + codeine

Therefore, whenever a commercial combination preparation is involved:

Do not attribute the entire syndrome to carisoprodol.

Specifically consider:

• Salicylate toxicity
• Opioid toxicity

according to the actual ingredients.

Toxic Dose

There is no reliable single toxic dose.

Gram-level ingestion can produce serious toxicity, but severity varies greatly depending on:

• Opioid/sedative tolerance
• Coingestants
• Age
• Renal function
• Hepatic function
• CYP2C19 phenotype
• Chronic carisoprodol exposure

The older concept that “gram quantities intoxicate an adult” remains qualitatively useful, but there is no validated numerical dose that separates mild from severe poisoning.

Therefore:

Clinical findings matter more than the reported dose.

Pathophysiology

Central nervous system effects

The precise therapeutic mechanism is still not completely established.

Current FDA labeling states that carisoprodol:

• Acts centrally
• Does not directly relax skeletal muscle
• Is associated experimentally with altered interneuronal activity in the spinal cord and descending reticular formation.

Modern pharmacologic evidence also supports modulation of:

GABA-A receptor activity

which helps explain its:

• Sedative
• Anxiolytic
• Abuse
• Respiratory-depressant

properties.

Meprobamate – Important Active Metabolite

Carisoprodol undergoes hepatic metabolism through:

CYP2C19

to form:

Meprobamate

Meprobamate has significant:

• Sedative
• Anxiolytic
• CNS-depressant

activity.

This creates a clinically important two-stage toxicology picture:

Carisoprodol exposure → parent-drug effects → conversion to longer-acting meprobamate

Pharmacokinetics

Current labeling gives approximate half-lives of:

Carisoprodol

~2 hours

Meprobamate

~10 hours

Therefore:

Sedation can persist substantially longer than the parent carisoprodol concentration would suggest.

This is especially relevant after:

• Large overdose
• Repeated dosing
• Chronic misuse
• Renal dysfunction

CYP2C19 Pharmacogenetics

CYP2C19 activity varies substantially between individuals.

Poor metabolizers can have approximately:

4-fold greater carisoprodol exposure

with correspondingly reduced conversion to meprobamate.

This may partly explain variation in:

• Clinical effects
• Duration
• Neuroexcitation versus sedation

Drug Interactions

CNS depressants

The most clinically important interaction is:

Carisoprodol + another CNS depressant → additive sedation/respiratory depression

Important agents include:

• Opioids
• Benzodiazepines
• Alcohol
• Tricyclic antidepressants
• Sedating antihistamines
• Other muscle relaxants

CYP2C19 inhibitors

Examples include:

• Omeprazole
• Fluvoxamine

These may:

↑ carisoprodol exposure + ↓ meprobamate formation

CYP2C19 inducers

Examples include:

• Rifampin
• St John’s wort

These may:

↓ carisoprodol exposure + ↑ meprobamate formation

Clinical Features

CNS Depression

The most common overdose manifestation is:

CNS depression

which may progress through:

• Dizziness
• Drowsiness
• Ataxia
• Dysarthria
• Poor coordination
• Stupor
• Coma

Current FDA labeling specifically reports:

• Coma
• Respiratory depression
• Death

after overdose.

Respiratory

Severe toxicity may cause:

Respiratory depression → hypoventilation → hypercapnia/hypoxia → respiratory arrest

Risk increases substantially with:

• Opioids
• Benzodiazepines
• Alcohol

Patients with profound CNS depression may lose airway reflexes and require intubation.

Neuroexcitation / Abnormal Movements

Carisoprodol poisoning is unusual among sedatives because some patients develop marked CNS excitation.

Reported manifestations include:

• Agitation
• Tremor
• Myoclonus
• Rigidity
• Dystonic reactions
• Choreiform or unusual “robot-like” movements
• Hyperreflexia
• Delirium

The clinical pattern can differ from that of pure meprobamate poisoning.

The 2025 UK toxicology review describes parent carisoprodol toxicity as more likely to produce:

• Tachycardia
• Tremor
• Shivering
• Myoclonus/abnormal movements
• Agitation

whereas meprobamate more typically causes:

CNS depression + hypotension + hyporeflexia/flaccidity.

Seizures

Seizures have been reported in overdose.

Current labeling notes that many seizure cases involve:

• Multiple drug overdoses
• Alcohol
• Drugs of abuse

rather than pure isolated therapeutic exposure.

Serotonin Toxicity

Current FDA labeling states that:

Serotonin syndrome has been reported with carisoprodol intoxication.

Possible findings include:

• Agitation
• Tremor
• Hyperreflexia
• Clonus/myoclonus
• Hyperthermia
• Tachycardia

However:

Serotonin toxicity is not the usual presentation of carisoprodol overdose.

It should be particularly considered when there is:

• Marked neuromuscular excitation
• Hyperthermia
• Clonus
• Coexposure to serotonergic drugs

Case-series evidence has described serotonergic features after high-dose intoxication.

Cardiovascular

Possible manifestations include:

• Tachycardia
• Postural hypotension
• Hypotension
• Syncope

Severe poisoning may produce:

• Profound hypotension
• Cardiovascular instability

Current labeling specifically identifies hypotension as a possible serious overdose manifestation.

Gastrointestinal

Possible effects include:

• Nausea
• Vomiting
• Epigastric discomfort

These are generally less clinically important than respiratory/CNS toxicity.

Pupils / Eyes

Reported overdose findings include:

• Nystagmus
• Blurred vision
• Mydriasis

Thus pupil findings are nonspecific and should not be used to distinguish carisoprodol reliably from other sedatives.

Withdrawal

An important feature largely underemphasized in older descriptions is physical dependence.

Abrupt cessation after prolonged/high-dose use may cause:

• Insomnia
• Anxiety
• Vomiting
• Abdominal cramps
• Headache
• Tremor
• Muscle twitching
• Ataxia
• Hallucinations
• Psychosis

The syndrome can resemble withdrawal from other sedative-hypnotics.

Therefore:

Do not abruptly discontinue heavy chronic carisoprodol use without considering withdrawal risk.

Diagnosis

Diagnosis is mainly clinical:

Exposure history + CNS depression or mixed sedative/neuroexcitant toxidrome

There is no rapidly available serum concentration routinely required for treatment.

Differential Diagnosis

Carisoprodol overdose may resemble:

• Ethanol
• Benzodiazepines
• Barbiturates
• Meprobamate
• Other muscle relaxants
• Gabapentinoids
• Opioids
• Sedating antihistamines
• Clonidine

If abnormal movements, hyperreflexia, or agitation predominate, consider:

• Serotonin syndrome
• Stimulant intoxication
• Anticholinergic poisoning
• Withdrawal syndromes

Essential Assessment

Evaluate:

• Airway
• Respiratory rate
• Depth of ventilation
• Mental status
• Blood pressure
• Heart rate
• Temperature
• Bedside glucose

Pulse oximetry should be used, but remember:

Supplemental oxygen can maintain a normal SpO₂ despite significant hypoventilation.

Therefore, in significant CNS depression consider:

• Continuous capnography
• Venous/arterial blood gas

Laboratory Tests

In moderate/severe poisoning consider:

• Electrolytes
• Glucose
• BUN
• Creatinine
• Bicarbonate
• Blood gas
• CK after seizures/prolonged immobilization

Obtain an ECG in:

• Significant overdose
• Syncope
• Hypotension
• Suspected coingestion

For intentional overdose, consider:

• Acetaminophen concentration
• Salicylate concentration