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Toxicology – Irritant Gases (Low Water Solubility)
Source
Low-solubility irritant gases include phosgene, nitrogen dioxide, and chlorine (moderate solubility). Phosgene is used in chemical manufacturing, nitrogen dioxide is produced from nitric acid fumes and agricultural silos, and chlorine is widely used in industrial cleaning and plastic production.
Typical Presentation
Exposure often occurs in industrial accidents or environmental releases. Patients may initially appear stable but later develop significant respiratory symptoms.
Clinical Features
Symptoms primarily involve the lower respiratory tract. Patients may develop coughing, wheezing, and signs of acute lung injury. Because these gases are poorly soluble in water, early upper airway irritation may be minimal. More severe complications include pneumonitis and delayed pulmonary edema, which can occur 12–24 hours after exposure. In cases of high-dose exposure, upper airway symptoms such as runny nose, cough, breathing difficulty, and stridor may also occur.
Mechanism of Action
Due to their low water solubility, these gases penetrate deeply into the lungs before reacting. Once in the lower airways, they form acids (e.g., hydrochloric acid from chlorine or phosgene, nitric acids from nitrogen dioxide), leading to direct injury of alveolar tissue, inflammation, and fluid accumulation.
Management
Immediate removal from the exposure source is essential. Treatment includes administration of high-flow oxygen and supportive respiratory care. Bronchodilators may be used for airway symptoms, and pulmonary edema should be managed appropriately. There is no specific antidote.
Key Points
Source
Low-solubility irritant gases include phosgene, nitrogen dioxide, and chlorine (moderate solubility). Phosgene is used in chemical manufacturing, nitrogen dioxide is produced from nitric acid fumes and agricultural silos, and chlorine is widely used in industrial cleaning and plastic production.
Typical Presentation
Exposure often occurs in industrial accidents or environmental releases. Patients may initially appear stable but later develop significant respiratory symptoms.
Clinical Features
Symptoms primarily involve the lower respiratory tract. Patients may develop coughing, wheezing, and signs of acute lung injury. Because these gases are poorly soluble in water, early upper airway irritation may be minimal. More severe complications include pneumonitis and delayed pulmonary edema, which can occur 12–24 hours after exposure. In cases of high-dose exposure, upper airway symptoms such as runny nose, cough, breathing difficulty, and stridor may also occur.
Mechanism of Action
Due to their low water solubility, these gases penetrate deeply into the lungs before reacting. Once in the lower airways, they form acids (e.g., hydrochloric acid from chlorine or phosgene, nitric acids from nitrogen dioxide), leading to direct injury of alveolar tissue, inflammation, and fluid accumulation.
Management
Immediate removal from the exposure source is essential. Treatment includes administration of high-flow oxygen and supportive respiratory care. Bronchodilators may be used for airway symptoms, and pulmonary edema should be managed appropriately. There is no specific antidote.
Key Points
- Symptoms may be delayed, especially pulmonary edema.
- Low-solubility gases primarily affect the lower respiratory tract.
- Early symptoms may be mild despite significant exposure.
- Prompt monitoring is important due to risk of delayed deterioration.
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Toxicology – Nerve Agent Toxicity
Source
Nerve agents are highly toxic chemicals developed for warfare and terrorist use. They are classified into two main groups:
Typical Presentation
Exposure typically occurs via inhalation, skin contact, or ingestion. Patients often present rapidly with symptoms of excessive cholinergic activity affecting multiple organ systems.
Clinical Features
Findings are consistent with a cholinergic toxidrome. Common features include pinpoint pupils (miosis), slow heart rate (bradycardia), excessive secretions (salivation, tearing, bronchorrhea), bronchospasm, vomiting, diarrhea, and urination. Neuromuscular effects include muscle twitching (fasciculations), weakness, seizures, and coma. Respiratory failure is a major cause of death.
Mechanism of Action
Nerve agents are organophosphate compounds that irreversibly inhibit acetylcholinesterase. This leads to accumulation of acetylcholine at synapses, resulting in continuous stimulation of both muscarinic and nicotinic receptors. Over time, the enzyme–toxin complex undergoes “aging,” making inhibition permanent.
Management
Immediate removal from the exposure source and decontamination are critical. Atropine is administered to counteract muscarinic effects by blocking acetylcholine receptors. Pralidoxime (2-PAM) can reactivate acetylcholinesterase if given early, before aging occurs. Benzodiazepines are used to control seizures. Supportive care, including airway management, is essential.
Key Points
Source
Nerve agents are highly toxic chemicals developed for warfare and terrorist use. They are classified into two main groups:
- G-series agents (developed in Germany): tabun (GA), sarin (GB), soman (GD), and cyclosarin (GF)
- V-series agents (developed in the United Kingdom): VE, VG, VM, VR, and VX
Typical Presentation
Exposure typically occurs via inhalation, skin contact, or ingestion. Patients often present rapidly with symptoms of excessive cholinergic activity affecting multiple organ systems.
Clinical Features
Findings are consistent with a cholinergic toxidrome. Common features include pinpoint pupils (miosis), slow heart rate (bradycardia), excessive secretions (salivation, tearing, bronchorrhea), bronchospasm, vomiting, diarrhea, and urination. Neuromuscular effects include muscle twitching (fasciculations), weakness, seizures, and coma. Respiratory failure is a major cause of death.
Mechanism of Action
Nerve agents are organophosphate compounds that irreversibly inhibit acetylcholinesterase. This leads to accumulation of acetylcholine at synapses, resulting in continuous stimulation of both muscarinic and nicotinic receptors. Over time, the enzyme–toxin complex undergoes “aging,” making inhibition permanent.
Management
Immediate removal from the exposure source and decontamination are critical. Atropine is administered to counteract muscarinic effects by blocking acetylcholine receptors. Pralidoxime (2-PAM) can reactivate acetylcholinesterase if given early, before aging occurs. Benzodiazepines are used to control seizures. Supportive care, including airway management, is essential.
Key Points
- Rapid onset and high lethality require immediate intervention.
- G-series agents are volatile; V-series agents are persistent and more difficult to remove.
- Early administration of pralidoxime is crucial before irreversible enzyme inhibition occurs.
- Respiratory failure is the primary life-threatening complication.
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Toxicology – Vesicants (Blistering Agents)
Source
Vesicants are chemical warfare agents that include sulfur mustard, nitrogen mustard, and Lewisite. Another related compound, phosgene oxime, is considered a nettle agent because it causes immediate irritation rather than true blister formation. These agents have been used historically in warfare and can cause severe tissue injury.
Typical Presentation
Exposure may occur through skin contact, inhalation, or eye exposure. Symptoms may be immediate or delayed depending on the specific agent involved.
Clinical Features
Skin exposure initially causes redness (erythema), followed by the formation of fluid-filled blisters (vesicles and bullae), which may rupture. Eye exposure can lead to pain, tearing, and temporary vision loss due to corneal injury. Inhalation results in irritation of the respiratory tract, potentially causing coughing, breathing difficulty, and airway damage. The severity of injury depends on the concentration, duration, and form of exposure (liquid vs gas).
Mechanism of Action
Vesicants are highly reactive alkylating agents that damage cells by interfering with essential metabolic processes, leading to tissue destruction. They are readily absorbed through the skin, eyes, respiratory tract, and mucous membranes. Effects from some agents (e.g., Lewisite) occur rapidly, while others (e.g., mustard agents) may have delayed onset.
Management
Immediate removal from the exposure source and thorough decontamination are critical. Treatment is largely supportive, focusing on wound care, respiratory support, and symptom management. In cases of Lewisite exposure, a specific antidote—dimercaprol (British anti-Lewisite, BAL)—may be administered.
Key Points
Source
Vesicants are chemical warfare agents that include sulfur mustard, nitrogen mustard, and Lewisite. Another related compound, phosgene oxime, is considered a nettle agent because it causes immediate irritation rather than true blister formation. These agents have been used historically in warfare and can cause severe tissue injury.
Typical Presentation
Exposure may occur through skin contact, inhalation, or eye exposure. Symptoms may be immediate or delayed depending on the specific agent involved.
Clinical Features
Skin exposure initially causes redness (erythema), followed by the formation of fluid-filled blisters (vesicles and bullae), which may rupture. Eye exposure can lead to pain, tearing, and temporary vision loss due to corneal injury. Inhalation results in irritation of the respiratory tract, potentially causing coughing, breathing difficulty, and airway damage. The severity of injury depends on the concentration, duration, and form of exposure (liquid vs gas).
Mechanism of Action
Vesicants are highly reactive alkylating agents that damage cells by interfering with essential metabolic processes, leading to tissue destruction. They are readily absorbed through the skin, eyes, respiratory tract, and mucous membranes. Effects from some agents (e.g., Lewisite) occur rapidly, while others (e.g., mustard agents) may have delayed onset.
Management
Immediate removal from the exposure source and thorough decontamination are critical. Treatment is largely supportive, focusing on wound care, respiratory support, and symptom management. In cases of Lewisite exposure, a specific antidote—dimercaprol (British anti-Lewisite, BAL)—may be administered.
Key Points
- Effects may be delayed, especially with mustard agents.
- Skin, eyes, and respiratory tract are most commonly affected.
- Early decontamination significantly reduces injury severity.
- BAL is an antidote specifically for Lewisite exposure
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Toxicology – Sulfonylurea Toxicity
Source
Sulfonylureas are oral medications used to treat diabetes by lowering blood glucose levels. They are divided into first-generation agents (e.g., chlorpropamide, tolbutamide) and second-generation agents (e.g., glipizide, glyburide, glimepiride), with the latter generally having longer durations of action.
Typical Presentation
Toxicity often occurs in children after accidental ingestion or in adults due to overdose. Patients typically present with symptoms of low blood sugar, which may be severe and prolonged.
Clinical Features
The hallmark finding is hypoglycemia, which can manifest as confusion, dizziness, sweating, nausea, vomiting, fainting, seizures, or coma. Symptoms may recur due to the long-lasting effect of these medications.
Mechanism of Action
Sulfonylureas stimulate insulin release from pancreatic beta cells. They act by blocking potassium channels on these cells, leading to membrane depolarization, opening of calcium channels, and increased insulin secretion. This results in decreased blood glucose levels.
Management
Immediate treatment involves intravenous dextrose (e.g., D50) to correct hypoglycemia. Continuous glucose monitoring and repeated glucose administration may be necessary. Octreotide (a somatostatin analog) can be used to suppress insulin release and reduce the risk of recurrent hypoglycemia. Activated charcoal may be considered in early presentations. Patients should be admitted for observation due to the risk of prolonged or recurrent symptoms.
Key Points
Source
Sulfonylureas are oral medications used to treat diabetes by lowering blood glucose levels. They are divided into first-generation agents (e.g., chlorpropamide, tolbutamide) and second-generation agents (e.g., glipizide, glyburide, glimepiride), with the latter generally having longer durations of action.
Typical Presentation
Toxicity often occurs in children after accidental ingestion or in adults due to overdose. Patients typically present with symptoms of low blood sugar, which may be severe and prolonged.
Clinical Features
The hallmark finding is hypoglycemia, which can manifest as confusion, dizziness, sweating, nausea, vomiting, fainting, seizures, or coma. Symptoms may recur due to the long-lasting effect of these medications.
Mechanism of Action
Sulfonylureas stimulate insulin release from pancreatic beta cells. They act by blocking potassium channels on these cells, leading to membrane depolarization, opening of calcium channels, and increased insulin secretion. This results in decreased blood glucose levels.
Management
Immediate treatment involves intravenous dextrose (e.g., D50) to correct hypoglycemia. Continuous glucose monitoring and repeated glucose administration may be necessary. Octreotide (a somatostatin analog) can be used to suppress insulin release and reduce the risk of recurrent hypoglycemia. Activated charcoal may be considered in early presentations. Patients should be admitted for observation due to the risk of prolonged or recurrent symptoms.
Key Points
- Even small ingestions can cause significant hypoglycemia, especially in children.
- Recurrent hypoglycemia is common due to prolonged drug action.
- Toxicity may be increased when combined with certain medications or alcohol.
- Close monitoring is essential until blood glucose levels stabilize.
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Toxicology – Insulin Overdose
Source
Insulin is used in various formulations for the management of diabetes mellitus. These include rapid-acting types (e.g., aspart, lispro, glulisine), short-acting (regular insulin), intermediate-acting (NPH), and long-acting forms (e.g., glargine, detemir). Each differs in onset and duration of action.
Typical Presentation
Patients may present after intentional or accidental overdose, often with altered consciousness. Severe cases may involve seizures or coma due to profound hypoglycemia.
Clinical Features
The primary manifestation is hypoglycemia, which can present with sweating, tachycardia, tremors, confusion, seizures, or coma. Some individuals may tolerate low glucose levels with minimal symptoms, while others deteriorate rapidly. Electrolyte abnormalities such as low potassium and magnesium may lead to cardiac arrhythmias. Additional findings may include hypothermia and, in severe cases, focal neurological deficits that can mimic stroke. Pulmonary edema and low phosphate levels have also been reported in significant overdoses.
Mechanism of Action
Insulin promotes the uptake of glucose into cells, particularly in the liver, muscle, and adipose tissue. Excess insulin leads to a rapid drop in blood glucose levels. The duration and severity of hypoglycemia depend on the type and amount of insulin administered.
Management
Immediate treatment involves administration of intravenous dextrose (e.g., D50) to rapidly correct hypoglycemia and restore neurological function. Continuous glucose monitoring with frequent checks is essential. Ongoing intravenous dextrose infusion may be required, along with correction of electrolyte imbalances.
Key Points
Source
Insulin is used in various formulations for the management of diabetes mellitus. These include rapid-acting types (e.g., aspart, lispro, glulisine), short-acting (regular insulin), intermediate-acting (NPH), and long-acting forms (e.g., glargine, detemir). Each differs in onset and duration of action.
Typical Presentation
Patients may present after intentional or accidental overdose, often with altered consciousness. Severe cases may involve seizures or coma due to profound hypoglycemia.
Clinical Features
The primary manifestation is hypoglycemia, which can present with sweating, tachycardia, tremors, confusion, seizures, or coma. Some individuals may tolerate low glucose levels with minimal symptoms, while others deteriorate rapidly. Electrolyte abnormalities such as low potassium and magnesium may lead to cardiac arrhythmias. Additional findings may include hypothermia and, in severe cases, focal neurological deficits that can mimic stroke. Pulmonary edema and low phosphate levels have also been reported in significant overdoses.
Mechanism of Action
Insulin promotes the uptake of glucose into cells, particularly in the liver, muscle, and adipose tissue. Excess insulin leads to a rapid drop in blood glucose levels. The duration and severity of hypoglycemia depend on the type and amount of insulin administered.
Management
Immediate treatment involves administration of intravenous dextrose (e.g., D50) to rapidly correct hypoglycemia and restore neurological function. Continuous glucose monitoring with frequent checks is essential. Ongoing intravenous dextrose infusion may be required, along with correction of electrolyte imbalances.
Key Points
- Large or subcutaneous injections may create a “depot effect,” leading to prolonged hypoglycemia.
- Delayed absorption can result in recurrent or persistent symptoms.
- Early treatment is critical; prolonged hypoglycemia worsens prognosis.
- Elevated C-peptide levels suggest endogenous insulin production rather than exogenous overdose.
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Toxicology – Baclofen Toxicity
Source
Baclofen is a prescription muscle relaxant used to treat spasticity in conditions such as spinal cord injury, cerebral palsy, and multiple sclerosis. It is available in oral form and can also be administered via intrathecal pumps for targeted delivery.
Typical Presentation
Toxicity may occur following overdose or misuse. Patients often present with progressive central nervous system depression, which may initially resemble intoxication and later advance to severe neurological impairment.
Clinical Features
Findings are consistent with a sedative-hypnotic toxidrome. Symptoms include drowsiness, poor coordination, ataxia, slurred speech, nausea, vomiting, and altered mental status. Cardiovascular effects may include either low or high blood pressure and slow or fast heart rate. Neurologically, decreased reflexes, muscle relaxation, coma, seizures, apnea, and respiratory arrest can occur. In some cases, paradoxical muscle rigidity or spasms may be seen. Severe toxicity is more likely with large ingestions and may require prolonged intensive care support.
Mechanism of Action
Baclofen acts as a GABA(B) receptor agonist, producing inhibitory effects within the central nervous system. Abrupt discontinuation after chronic use can lead to a withdrawal syndrome similar to that seen with alcohol or benzodiazepines.
Management
Treatment is supportive, with close monitoring of airway, breathing, and circulation. Mechanical ventilation may be required in cases of significant respiratory depression.
Key Points
Source
Baclofen is a prescription muscle relaxant used to treat spasticity in conditions such as spinal cord injury, cerebral palsy, and multiple sclerosis. It is available in oral form and can also be administered via intrathecal pumps for targeted delivery.
Typical Presentation
Toxicity may occur following overdose or misuse. Patients often present with progressive central nervous system depression, which may initially resemble intoxication and later advance to severe neurological impairment.
Clinical Features
Findings are consistent with a sedative-hypnotic toxidrome. Symptoms include drowsiness, poor coordination, ataxia, slurred speech, nausea, vomiting, and altered mental status. Cardiovascular effects may include either low or high blood pressure and slow or fast heart rate. Neurologically, decreased reflexes, muscle relaxation, coma, seizures, apnea, and respiratory arrest can occur. In some cases, paradoxical muscle rigidity or spasms may be seen. Severe toxicity is more likely with large ingestions and may require prolonged intensive care support.
Mechanism of Action
Baclofen acts as a GABA(B) receptor agonist, producing inhibitory effects within the central nervous system. Abrupt discontinuation after chronic use can lead to a withdrawal syndrome similar to that seen with alcohol or benzodiazepines.
Management
Treatment is supportive, with close monitoring of airway, breathing, and circulation. Mechanical ventilation may be required in cases of significant respiratory depression.
Key Points
- High doses are associated with severe CNS depression, seizures, and prolonged coma.
- Baclofen toxicity can sometimes mimic brain death.
- The drug has potential for misuse due to its sedative and euphoric effects.
- Intrathecal administration requires much smaller doses compared to oral use.
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Toxicology – Carisoprodol Toxicity
Source
Carisoprodol is a centrally acting skeletal muscle relaxant, often prescribed alone or in combination with other agents such as aspirin or codeine. It has a relatively rapid onset (about 30 minutes) and a short duration of action. The drug is metabolized into meprobamate, an active compound with sedative properties.
Typical Presentation
Patients may present with overdose or misuse, often in combination with other substances such as opioids or alcohol. Requests for specific medications and recurrent visits may raise suspicion for misuse.
Clinical Features
Toxicity produces features of a sedative-hypnotic syndrome. Symptoms include central nervous system depression, drowsiness, poor coordination, ataxia, slurred speech, nausea, vomiting, hypotension, and bradycardia. Severe cases may progress to coma, seizures, respiratory depression, or arrest. Some patients may paradoxically exhibit increased muscle tone, hyperreflexia, or abnormal posturing.
Mechanism of Action
Carisoprodol and its metabolite meprobamate enhance activity at GABA(A) receptors, producing sedative effects similar to barbiturates. Abrupt discontinuation after chronic use can lead to withdrawal symptoms resembling those seen with alcohol or benzodiazepines.
Management
Treatment is supportive, with attention to airway protection, breathing, and circulation. Monitoring is essential, especially in cases of suspected coingestion with other central nervous system depressants.
Key Points
Source
Carisoprodol is a centrally acting skeletal muscle relaxant, often prescribed alone or in combination with other agents such as aspirin or codeine. It has a relatively rapid onset (about 30 minutes) and a short duration of action. The drug is metabolized into meprobamate, an active compound with sedative properties.
Typical Presentation
Patients may present with overdose or misuse, often in combination with other substances such as opioids or alcohol. Requests for specific medications and recurrent visits may raise suspicion for misuse.
Clinical Features
Toxicity produces features of a sedative-hypnotic syndrome. Symptoms include central nervous system depression, drowsiness, poor coordination, ataxia, slurred speech, nausea, vomiting, hypotension, and bradycardia. Severe cases may progress to coma, seizures, respiratory depression, or arrest. Some patients may paradoxically exhibit increased muscle tone, hyperreflexia, or abnormal posturing.
Mechanism of Action
Carisoprodol and its metabolite meprobamate enhance activity at GABA(A) receptors, producing sedative effects similar to barbiturates. Abrupt discontinuation after chronic use can lead to withdrawal symptoms resembling those seen with alcohol or benzodiazepines.
Management
Treatment is supportive, with attention to airway protection, breathing, and circulation. Monitoring is essential, especially in cases of suspected coingestion with other central nervous system depressants.
Key Points
- Frequently abused due to its sedative and euphoric effects.
- Often taken in combination with opioids or alcohol, increasing risk of severe toxicity.
- Withdrawal can occur with abrupt cessation after prolonged use.
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Toxicology – Nonsteroidal Anti-Inflammatory Drug (NSAID) Toxicity
Source
NSAIDs are widely used medications for pain relief, inflammation, and fever reduction. Ibuprofen is the most commonly encountered agent. Other examples include diclofenac, naproxen, indomethacin, ketorolac, meloxicam, and sulindac.
Typical Presentation
Most cases involve mild overdose, often in young individuals, presenting with gastrointestinal discomfort. Severe toxicity is uncommon but may occur with large ingestions.
Clinical Features
Symptoms are usually mild and include abdominal pain, nausea, and vomiting. Occasionally, patients may develop gastrointestinal bleeding. In more severe overdoses, complications can include acute kidney injury, hyperkalemia, tinnitus, seizures, coma, or cardiovascular collapse. Symptoms typically begin within a few hours of ingestion and resolve within 24 hours in uncomplicated cases.
Mechanism of Action
NSAIDs inhibit cyclooxygenase enzymes (COX-1 and COX-2), reducing prostaglandin production. While this provides therapeutic effects, it can also impair kidney function and damage the gastrointestinal lining, especially with high doses or prolonged use.
Management
Treatment is supportive. Intravenous fluids and antiemetics are commonly used. There is no specific antidote. Patients with mild symptoms and stable vital signs may be observed for several hours and discharged if no complications develop.
Key Points
Source
NSAIDs are widely used medications for pain relief, inflammation, and fever reduction. Ibuprofen is the most commonly encountered agent. Other examples include diclofenac, naproxen, indomethacin, ketorolac, meloxicam, and sulindac.
Typical Presentation
Most cases involve mild overdose, often in young individuals, presenting with gastrointestinal discomfort. Severe toxicity is uncommon but may occur with large ingestions.
Clinical Features
Symptoms are usually mild and include abdominal pain, nausea, and vomiting. Occasionally, patients may develop gastrointestinal bleeding. In more severe overdoses, complications can include acute kidney injury, hyperkalemia, tinnitus, seizures, coma, or cardiovascular collapse. Symptoms typically begin within a few hours of ingestion and resolve within 24 hours in uncomplicated cases.
Mechanism of Action
NSAIDs inhibit cyclooxygenase enzymes (COX-1 and COX-2), reducing prostaglandin production. While this provides therapeutic effects, it can also impair kidney function and damage the gastrointestinal lining, especially with high doses or prolonged use.
Management
Treatment is supportive. Intravenous fluids and antiemetics are commonly used. There is no specific antidote. Patients with mild symptoms and stable vital signs may be observed for several hours and discharged if no complications develop.
Key Points
- Most acute NSAID overdoses are mild and self-limiting.
- Serious toxicity is more likely with very high doses (e.g., >400 mg/kg).
- Use caution in elderly patients and those with kidney disease, even at normal doses.
- Chronic overuse increases the risk of gastrointestinal bleeding and renal injury.
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Toxicology – Salicylate Toxicity
Source
Salicylates are present in many over-the-counter and prescription medications used for pain, fever, and inflammation. Common sources include aspirin, methyl salicylate (oil of wintergreen), combination cold remedies, topical analgesics, bismuth subsalicylate (e.g., Pepto-Bismol), and effervescent formulations like Alka-Seltzer.
Typical Presentation
Toxicity may occur acutely after a large ingestion or chronically from repeated high dosing, especially in elderly patients. Acute cases often present with gastrointestinal and auditory symptoms, whereas chronic toxicity may present more subtly.
Clinical Features
Acute Toxicity
Patients commonly develop nausea, vomiting, abdominal pain, rapid breathing (tachypnea), ringing in the ears (tinnitus), and confusion. Severe cases may progress to hypoglycemia, seizures, pulmonary edema, and coma. A classic finding is a mixed acid–base disorder: respiratory alkalosis combined with metabolic acidosis.
Chronic Toxicity
Typically seen in older individuals, presenting with confusion, dehydration, and metabolic acidosis. Symptoms are often nonspecific and can mimic other illnesses, making diagnosis more challenging.
Mechanism of Action
Salicylates stimulate the respiratory center in the brain, causing hyperventilation and respiratory alkalosis. They also uncouple oxidative phosphorylation, leading to increased acid production and metabolic acidosis. Additionally, they irreversibly inhibit cyclooxygenase (COX) enzymes.
Management
Treatment is supportive and includes careful monitoring. If intubation is required, maintaining adequate hyperventilation is critical to prevent worsening acidosis. Sodium bicarbonate is administered to alkalinize the blood (target pH ≥7.4) and urine (target pH 7.5–8.5), which enhances salicylate elimination.
Gastrointestinal decontamination with multiple-dose activated charcoal or whole bowel irrigation may be considered. Hemodialysis is indicated in severe toxicity, particularly with high salicylate levels or significant clinical deterioration. Patients should also be monitored for complications such as pulmonary edema.
Key Points
Source
Salicylates are present in many over-the-counter and prescription medications used for pain, fever, and inflammation. Common sources include aspirin, methyl salicylate (oil of wintergreen), combination cold remedies, topical analgesics, bismuth subsalicylate (e.g., Pepto-Bismol), and effervescent formulations like Alka-Seltzer.
Typical Presentation
Toxicity may occur acutely after a large ingestion or chronically from repeated high dosing, especially in elderly patients. Acute cases often present with gastrointestinal and auditory symptoms, whereas chronic toxicity may present more subtly.
Clinical Features
Acute Toxicity
Patients commonly develop nausea, vomiting, abdominal pain, rapid breathing (tachypnea), ringing in the ears (tinnitus), and confusion. Severe cases may progress to hypoglycemia, seizures, pulmonary edema, and coma. A classic finding is a mixed acid–base disorder: respiratory alkalosis combined with metabolic acidosis.
Chronic Toxicity
Typically seen in older individuals, presenting with confusion, dehydration, and metabolic acidosis. Symptoms are often nonspecific and can mimic other illnesses, making diagnosis more challenging.
Mechanism of Action
Salicylates stimulate the respiratory center in the brain, causing hyperventilation and respiratory alkalosis. They also uncouple oxidative phosphorylation, leading to increased acid production and metabolic acidosis. Additionally, they irreversibly inhibit cyclooxygenase (COX) enzymes.
Management
Treatment is supportive and includes careful monitoring. If intubation is required, maintaining adequate hyperventilation is critical to prevent worsening acidosis. Sodium bicarbonate is administered to alkalinize the blood (target pH ≥7.4) and urine (target pH 7.5–8.5), which enhances salicylate elimination.
Gastrointestinal decontamination with multiple-dose activated charcoal or whole bowel irrigation may be considered. Hemodialysis is indicated in severe toxicity, particularly with high salicylate levels or significant clinical deterioration. Patients should also be monitored for complications such as pulmonary edema.
Key Points
- Chronic toxicity is often missed due to nonspecific symptoms.
- Mixed respiratory alkalosis and metabolic acidosis is a hallmark finding.
- Oil of wintergreen is highly concentrated and potentially lethal, especially in children.
- Chronic toxicity generally carries a worse prognosis than acute overdose.
- Adequate ventilation must be maintained in intubated patients.
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Toxicology – Acetaminophen (Paracetamol) Toxicity
Source
Acetaminophen is a commonly used over-the-counter medication for pain relief and fever reduction. It is available as a single agent and is frequently combined with other drugs, including opioids and “cold and flu” preparations. In adults, doses below 4 grams per day are generally considered safe.
Typical Presentation
Patients may present after intentional or accidental overdose. Early on, individuals often appear well, which can make diagnosis challenging without a clear history.
Clinical Features
In the initial phase, symptoms may be minimal or limited to mild nausea and vomiting. Within 24–48 hours, laboratory abnormalities begin to appear, including elevated liver enzymes (ALT, AST) and prolonged coagulation times (PT/PTT). As toxicity progresses, patients may develop altered mental status, metabolic acidosis, liver failure, and kidney injury. Severe cases can lead to encephalopathy and death.
Mechanism of Action
Acetaminophen is metabolized primarily through glucuronidation and sulfation. A smaller portion is metabolized via the cytochrome P450 system, producing a toxic metabolite (NAPQI). Under normal conditions, NAPQI is neutralized by glutathione. In overdose, glutathione stores are depleted, allowing NAPQI to accumulate and cause liver cell damage.
Management
An acetaminophen level should be measured approximately 4 hours after ingestion and interpreted using the Rumack-Matthew nomogram. If levels fall within the treatment range, N-acetylcysteine (NAC) should be administered. NAC acts as a glutathione substitute and helps detoxify the harmful metabolite. It is most effective when given early but can still be beneficial later in the course. NAC is available in both oral and intravenous forms. Severe liver failure may require liver transplantation.
Key Points
Source
Acetaminophen is a commonly used over-the-counter medication for pain relief and fever reduction. It is available as a single agent and is frequently combined with other drugs, including opioids and “cold and flu” preparations. In adults, doses below 4 grams per day are generally considered safe.
Typical Presentation
Patients may present after intentional or accidental overdose. Early on, individuals often appear well, which can make diagnosis challenging without a clear history.
Clinical Features
In the initial phase, symptoms may be minimal or limited to mild nausea and vomiting. Within 24–48 hours, laboratory abnormalities begin to appear, including elevated liver enzymes (ALT, AST) and prolonged coagulation times (PT/PTT). As toxicity progresses, patients may develop altered mental status, metabolic acidosis, liver failure, and kidney injury. Severe cases can lead to encephalopathy and death.
Mechanism of Action
Acetaminophen is metabolized primarily through glucuronidation and sulfation. A smaller portion is metabolized via the cytochrome P450 system, producing a toxic metabolite (NAPQI). Under normal conditions, NAPQI is neutralized by glutathione. In overdose, glutathione stores are depleted, allowing NAPQI to accumulate and cause liver cell damage.
Management
An acetaminophen level should be measured approximately 4 hours after ingestion and interpreted using the Rumack-Matthew nomogram. If levels fall within the treatment range, N-acetylcysteine (NAC) should be administered. NAC acts as a glutathione substitute and helps detoxify the harmful metabolite. It is most effective when given early but can still be beneficial later in the course. NAC is available in both oral and intravenous forms. Severe liver failure may require liver transplantation.
Key Points
- Early stages may be asymptomatic despite significant toxicity.
- Always consider acetaminophen exposure in mixed or unknown overdoses.
- The nomogram is not reliable for chronic ingestion or certain extended-release formulations.
- Toxic doses are generally ≥7.5 g in adults and ≥140 mg/kg in children.
