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Toxicology – Carbamate Poisoning
Sources
Carbamates are commonly found in insecticides such as carbaryl, aldicarb, carbofuran, and methomyl. They are also present in certain medications, including acetylcholinesterase inhibitors used for Alzheimer disease (e.g., rivastigmine) and therapeutic agents like neostigmine and physostigmine.
Typical Presentation
A common scenario involves accidental or intentional ingestion, particularly in children exposed to insecticides. Patients typically present with features of a cholinergic toxidrome, including excessive secretions, altered mental status, and respiratory symptoms.
Mechanism of Action
Carbamates inhibit acetylcholinesterase at synapses in both the central and peripheral nervous systems, as well as in red blood cells. Unlike organophosphates, this inhibition is reversible because carbamates do not cause “aging” of the enzyme, making their toxicity generally less severe.
Clinical Features
Muscarinic symptoms predominate and include miosis, bradycardia, salivation, sweating, bronchorrhea, bronchospasm, nausea, vomiting, diarrhea, lacrimation, and urinary incontinence. Central nervous system effects include confusion, lethargy, coma, and seizures. Nicotinic effects include muscle fasciculations and weakness. Severe cases may lead to death.
Management
Treatment involves prompt decontamination and supportive care. Atropine is administered to control muscarinic symptoms, particularly respiratory secretions, starting at 2–5 mg IV in adults (0.05 mg/kg in children) and repeated every 3–5 minutes with dose escalation until improvement is achieved. Pralidoxime may be used for neuromuscular symptoms, although its role is less critical compared to organophosphate poisoning. Benzodiazepines are indicated for agitation, muscle spasms, and seizures. Autoinjectors containing atropine and pralidoxime are available for emergency use.
Key Points
Sources
Carbamates are commonly found in insecticides such as carbaryl, aldicarb, carbofuran, and methomyl. They are also present in certain medications, including acetylcholinesterase inhibitors used for Alzheimer disease (e.g., rivastigmine) and therapeutic agents like neostigmine and physostigmine.
Typical Presentation
A common scenario involves accidental or intentional ingestion, particularly in children exposed to insecticides. Patients typically present with features of a cholinergic toxidrome, including excessive secretions, altered mental status, and respiratory symptoms.
Mechanism of Action
Carbamates inhibit acetylcholinesterase at synapses in both the central and peripheral nervous systems, as well as in red blood cells. Unlike organophosphates, this inhibition is reversible because carbamates do not cause “aging” of the enzyme, making their toxicity generally less severe.
Clinical Features
Muscarinic symptoms predominate and include miosis, bradycardia, salivation, sweating, bronchorrhea, bronchospasm, nausea, vomiting, diarrhea, lacrimation, and urinary incontinence. Central nervous system effects include confusion, lethargy, coma, and seizures. Nicotinic effects include muscle fasciculations and weakness. Severe cases may lead to death.
Management
Treatment involves prompt decontamination and supportive care. Atropine is administered to control muscarinic symptoms, particularly respiratory secretions, starting at 2–5 mg IV in adults (0.05 mg/kg in children) and repeated every 3–5 minutes with dose escalation until improvement is achieved. Pralidoxime may be used for neuromuscular symptoms, although its role is less critical compared to organophosphate poisoning. Benzodiazepines are indicated for agitation, muscle spasms, and seizures. Autoinjectors containing atropine and pralidoxime are available for emergency use.
Key Points
- Carbamates cause reversible inhibition of acetylcholinesterase and are generally less toxic than organophosphates.
- Central-acting acetylcholinesterase inhibitors such as donepezil and tacrine, used in Alzheimer disease, can produce cholinergic toxicity in overdose.
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Toxicology – Opioid (Opiate) Toxidrome
Sources
Opioid toxicity can result from a wide range of substances, including natural and synthetic narcotics such as morphine, heroin, codeine, oxycodone, hydrocodone, fentanyl, methadone, hydromorphone, buprenorphine, oxymorphone, meperidine, propoxyphene, opium, and kratom. These agents may be taken orally, inhaled, or injected. Many prescription formulations combine opioids with acetaminophen, and fentanyl is also available as a transdermal patch.
Typical Presentation
Patients often present with decreased level of consciousness and respiratory depression. A classic presentation includes somnolence, slow breathing, pinpoint pupils, and evidence of intravenous drug use such as track marks. Administration of naloxone can rapidly reverse symptoms, leading to abrupt awakening.
Clinical Features
Common findings include central nervous system depression, bradypnea, bradycardia, reduced bowel sounds, and miosis. Peripheral vasodilation may result in hypotension and hypothermia. Severe toxicity can lead to respiratory arrest and coma. Complications may include noncardiogenic pulmonary edema and, in certain cases such as methadone use, QT prolongation. Repeated dosing of meperidine may provoke seizures.
Mechanism of Action
Opioids exert their effects by binding to specific opioid receptors in the central nervous system and gastrointestinal tract, leading to decreased neuronal excitability and slowed physiological functions.
Management
Treatment is primarily supportive, with airway and breathing support as needed. Naloxone is the antidote and should be administered in small, titrated doses (0.4–2 mg in adults, 0.1 mg/kg in children) every 1–2 minutes until adequate ventilation is restored. Care should be taken to avoid precipitating acute withdrawal. For long-acting opioids, a continuous naloxone infusion (approximately two-thirds of the effective reversal dose per hour) may be required. Whole bowel irrigation may be considered in cases of ingestion of sustained-release formulations or transdermal patches.
Key Points
- Naloxone has a shorter duration of action than many opioids, so repeated dosing or infusion may be necessary.
- Prolonged unconsciousness can lead to complications such as rhabdomyolysis.
- Some opioids, such as propoxyphene, may cause cardiac conduction abnormalities and seizures.
- Many opioid combination products contain acetaminophen, increasing the risk of combined toxicity.
- Transdermal systems and “abuse-deterrent” formulations may still be misused through extraction methods.
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Toxicology – Sedative–Hypnotic (Hypnosedative) Toxidrome
Sources
This toxidrome is associated with a broad group of central nervous system depressants, including alcohols, anticonvulsants, barbiturates, benzodiazepines, chloral hydrate, gamma-hydroxybutyrate (GHB), phenobarbital, meprobamate, methaqualone, muscle relaxants, tranquilizers, and sedative-hypnotic agents such as zolpidem.
Typical Presentation
Patients often present with decreased level of consciousness, ranging from drowsiness to coma. A common scenario involves combined use of substances (e.g., benzodiazepines with alcohol), leading to enhanced sedative effects. Individuals may appear intoxicated, with slurred speech, poor coordination, and impaired balance.
Clinical Features
Findings resemble alcohol intoxication and include respiratory depression, bradycardia, hypotension, ataxia, slurred speech, lethargy, disinhibition, decreased muscle tone, nystagmus, and progressive central nervous system depression. Severe cases may progress to stupor or coma. Effects are typically dose-dependent and often worsened by coingestion with alcohol. Certain agents such as GHB and methaqualone may lower the seizure threshold, while abrupt withdrawal from chronic use can lead to seizures and may be life-threatening.
Mechanism of Action
Most sedative–hypnotic agents exert their effects by enhancing gamma-aminobutyric acid (GABA) activity in the central nervous system, resulting in generalized neuronal inhibition.
Management
Treatment is primarily supportive, with attention to airway protection and hemodynamic stability. In patients with altered mental status, cervical spine precautions and neuroimaging may be necessary to exclude other causes. Endotracheal intubation should be considered in cases of compromised airway or respiratory depression. Flumazenil may be used cautiously in benzodiazepine-naïve patients, but it is generally avoided in chronic users due to the risk of precipitating severe withdrawal and seizures.
Key Points
- Alkalinization of urine can enhance elimination of certain barbiturates.
- Meprobamate toxicity may be managed with dialysis in severe cases.
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Toxicology – Sources of Sedative–Hypnotic Agents
Sedative–hypnotics are substances that produce calming effects and promote sleep. With repeated use, individuals can develop tolerance, dependence, and addiction. Abrupt discontinuation after prolonged use may result in withdrawal symptoms, and cross-tolerance between agents is common.
Alcohols
Various alcohols—including ethanol, methanol, ethylene glycol, and isopropanol—can produce sedative effects. Methanol and ethylene glycol are particularly dangerous due to toxic metabolite formation, while isopropanol can cause profound central nervous system depression.
Barbiturates
This group includes agents such as phenobarbital, pentobarbital, secobarbital, amobarbital, and butalbital, all of which act as potent central nervous system depressants.
Benzodiazepines
Common examples include diazepam, lorazepam, alprazolam, clonazepam, midazolam, oxazepam, triazolam, chlordiazepoxide, flurazepam, and flunitrazepam. These are widely used for anxiety, sedation, and seizure control.
Chloral Hydrate
Available in both liquid and tablet forms, chloral hydrate can cause significant sedation and may lead to unconsciousness when combined with alcohol. It is also associated with cardiac arrhythmias.
Gamma-Hydroxybutyrate (GHB)
This group includes GHB, gamma-butyrolactone (GBL), and 1,4-butanediol. These substances produce rapid sedation and are sometimes misused recreationally.
Non-Benzodiazepine Sedative-Hypnotics (Sleeping Pills)
Medications such as zolpidem, zaleplon, eszopiclone, and zopiclone are commonly prescribed for insomnia and act on similar pathways as benzodiazepines.
Sedative–hypnotics are substances that produce calming effects and promote sleep. With repeated use, individuals can develop tolerance, dependence, and addiction. Abrupt discontinuation after prolonged use may result in withdrawal symptoms, and cross-tolerance between agents is common.
Alcohols
Various alcohols—including ethanol, methanol, ethylene glycol, and isopropanol—can produce sedative effects. Methanol and ethylene glycol are particularly dangerous due to toxic metabolite formation, while isopropanol can cause profound central nervous system depression.
Barbiturates
This group includes agents such as phenobarbital, pentobarbital, secobarbital, amobarbital, and butalbital, all of which act as potent central nervous system depressants.
Benzodiazepines
Common examples include diazepam, lorazepam, alprazolam, clonazepam, midazolam, oxazepam, triazolam, chlordiazepoxide, flurazepam, and flunitrazepam. These are widely used for anxiety, sedation, and seizure control.
Chloral Hydrate
Available in both liquid and tablet forms, chloral hydrate can cause significant sedation and may lead to unconsciousness when combined with alcohol. It is also associated with cardiac arrhythmias.
Gamma-Hydroxybutyrate (GHB)
This group includes GHB, gamma-butyrolactone (GBL), and 1,4-butanediol. These substances produce rapid sedation and are sometimes misused recreationally.
Non-Benzodiazepine Sedative-Hypnotics (Sleeping Pills)
Medications such as zolpidem, zaleplon, eszopiclone, and zopiclone are commonly prescribed for insomnia and act on similar pathways as benzodiazepines.
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Toxicology – Sympathomimetic Toxidrome
Sources
Sympathomimetic agents are substances that stimulate the sympathetic nervous system by increasing catecholamine activity. They may act directly on receptors (e.g., alpha- or beta-agonists) or indirectly by increasing catecholamine release, blocking reuptake, or inhibiting breakdown. Common examples include cocaine, amphetamines, MDMA, ephedrine, pseudoephedrine, epinephrine, MAO inhibitors, and synthetic stimulants such as “bath salts” (e.g., mephedrone).
Typical Presentation
Patients typically present in an agitated, hyperactive state. A common scenario involves stimulant use followed by symptoms such as chest pain, anxiety, and marked vital sign abnormalities including hypertension, tachycardia, and hyperthermia.
Clinical Features
This toxidrome reflects a “fight-or-flight” response. Key findings include tachycardia, hypertension, hyperthermia, dilated pupils, diaphoresis, hyperreflexia, and preserved bowel sounds. Patients may also exhibit agitation, pressured speech, paranoia, tremors, teeth grinding (bruxism), chest pain, and rhabdomyolysis. Unlike anticholinergic toxicity, patients are typically sweaty rather than dry.
Mechanism of Action
These agents stimulate the autonomic nervous system either by directly activating adrenergic receptors or indirectly by increasing catecholamine availability through enhanced release, decreased reuptake, or reduced metabolism.
Management
Treatment is largely supportive. Intravenous fluids are administered for hydration and to prevent or treat rhabdomyolysis. Benzodiazepines are first-line therapy for agitation, anxiety, and chest pain. Severe hyperthermia requires rapid cooling measures. Hypertension may be managed with benzodiazepines, vasodilators such as sodium nitroprusside, or alpha-blockers like phentolamine.
Key Points
Sources
Sympathomimetic agents are substances that stimulate the sympathetic nervous system by increasing catecholamine activity. They may act directly on receptors (e.g., alpha- or beta-agonists) or indirectly by increasing catecholamine release, blocking reuptake, or inhibiting breakdown. Common examples include cocaine, amphetamines, MDMA, ephedrine, pseudoephedrine, epinephrine, MAO inhibitors, and synthetic stimulants such as “bath salts” (e.g., mephedrone).
Typical Presentation
Patients typically present in an agitated, hyperactive state. A common scenario involves stimulant use followed by symptoms such as chest pain, anxiety, and marked vital sign abnormalities including hypertension, tachycardia, and hyperthermia.
Clinical Features
This toxidrome reflects a “fight-or-flight” response. Key findings include tachycardia, hypertension, hyperthermia, dilated pupils, diaphoresis, hyperreflexia, and preserved bowel sounds. Patients may also exhibit agitation, pressured speech, paranoia, tremors, teeth grinding (bruxism), chest pain, and rhabdomyolysis. Unlike anticholinergic toxicity, patients are typically sweaty rather than dry.
Mechanism of Action
These agents stimulate the autonomic nervous system either by directly activating adrenergic receptors or indirectly by increasing catecholamine availability through enhanced release, decreased reuptake, or reduced metabolism.
Management
Treatment is largely supportive. Intravenous fluids are administered for hydration and to prevent or treat rhabdomyolysis. Benzodiazepines are first-line therapy for agitation, anxiety, and chest pain. Severe hyperthermia requires rapid cooling measures. Hypertension may be managed with benzodiazepines, vasodilators such as sodium nitroprusside, or alpha-blockers like phentolamine.
Key Points
- Beta-blockers are generally avoided due to the risk of unopposed alpha-adrenergic vasoconstriction.
- Stimulant drugs can be easily manufactured or obtained, contributing to their widespread use.
- Sympathomimetics lower the seizure threshold, increasing the risk of seizures.
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Toxicology – Ototoxic Drugs
Overview
Ototoxic medications can damage the inner ear, affecting either the cochlea (leading to sensorineural hearing loss), the vestibular system (causing balance disturbances), or both.
Clinical Features
Patients may present with hearing impairment, ringing in the ears (tinnitus), or problems with balance and coordination (disequilibrium). Symptoms can vary depending on whether cochlear or vestibular structures are involved.
Common Drug Classes
Medications known to cause ototoxicity include aminoglycoside antibiotics, loop diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, platinum-based chemotherapeutic agents, quinidine, quinine, salicylates, tetracyclines, and valproic acid.
Management
The primary approach is prompt discontinuation of the offending agent when possible. Patients should be referred for evaluation by an ear, nose, and throat (ENT) specialist and audiology testing to assess the extent of hearing or balance dysfunction.
Overview
Ototoxic medications can damage the inner ear, affecting either the cochlea (leading to sensorineural hearing loss), the vestibular system (causing balance disturbances), or both.
Clinical Features
Patients may present with hearing impairment, ringing in the ears (tinnitus), or problems with balance and coordination (disequilibrium). Symptoms can vary depending on whether cochlear or vestibular structures are involved.
Common Drug Classes
Medications known to cause ototoxicity include aminoglycoside antibiotics, loop diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, platinum-based chemotherapeutic agents, quinidine, quinine, salicylates, tetracyclines, and valproic acid.
Management
The primary approach is prompt discontinuation of the offending agent when possible. Patients should be referred for evaluation by an ear, nose, and throat (ENT) specialist and audiology testing to assess the extent of hearing or balance dysfunction.
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Toxicology – Cardiac Physiology (Key Mechanisms)
Beta-Adrenergic Activation
Beta-agonists bind to β-receptors on cardiac cells, leading to activation of intracellular G proteins that initiate downstream signaling.
Adenylyl Cyclase Activation
The activated G protein stimulates adenylyl cyclase, an enzyme that converts ATP into cyclic AMP (cAMP), a key second messenger.
Glucagon Pathway
Glucagon can independently stimulate adenylyl cyclase, increasing cAMP levels through an alternative (“bypass”) pathway that does not rely on β-receptors.
Calcium Influx
Elevated cAMP activates protein kinase A, which enhances calcium channel opening and increases intracellular calcium entry, strengthening cardiac contraction.
cAMP Breakdown
cAMP is eventually degraded into inactive 5′-AMP by phosphodiesterase enzymes, terminating its effects.
Digitalis Effect
Digitalis inhibits the Na⁺/K⁺-ATPase pump, leading to increased intracellular sodium and secondary rise in intracellular calcium, which enhances cardiac contractility.
Key Points
Beta-Adrenergic Activation
Beta-agonists bind to β-receptors on cardiac cells, leading to activation of intracellular G proteins that initiate downstream signaling.
Adenylyl Cyclase Activation
The activated G protein stimulates adenylyl cyclase, an enzyme that converts ATP into cyclic AMP (cAMP), a key second messenger.
Glucagon Pathway
Glucagon can independently stimulate adenylyl cyclase, increasing cAMP levels through an alternative (“bypass”) pathway that does not rely on β-receptors.
Calcium Influx
Elevated cAMP activates protein kinase A, which enhances calcium channel opening and increases intracellular calcium entry, strengthening cardiac contraction.
cAMP Breakdown
cAMP is eventually degraded into inactive 5′-AMP by phosphodiesterase enzymes, terminating its effects.
Digitalis Effect
Digitalis inhibits the Na⁺/K⁺-ATPase pump, leading to increased intracellular sodium and secondary rise in intracellular calcium, which enhances cardiac contractility.
Key Points
- Beta-blockers inhibit β-adrenergic receptors, reducing cardiac stimulation.
- Glucagon is useful in beta-blocker overdose because it increases cAMP independently of β-receptors.
- Calcium channel blockers reduce calcium entry into cells, decreasing contractility and conduction.
- Phosphodiesterase inhibitors increase cAMP levels, thereby promoting calcium influx and enhancing cardiac function.
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Toxicology – Marijuana (Cannabis)
Source
Marijuana is derived from the female Cannabis plant and can be used in various forms, including smoking, ingestion, or as a brewed preparation.
Typical Presentation
A common scenario involves recreational use in social settings, leading to feelings of relaxation, euphoria, altered perception, and impaired coordination. Users may describe changes in time perception and sensory experiences.
Clinical Features
Psychological effects include euphoria, calmness, altered perception, impaired attention, decreased concentration, and possible hallucinations. Physical findings may include increased heart rate, elevated blood pressure, dry mouth, rapid breathing, red eyes (conjunctival injection), and increased appetite. Coordination and motor function may also be impaired.
Mechanism of Action
The primary psychoactive component, delta-9-tetrahydrocannabinol (THC), is highly lipophilic and rapidly absorbed, with peak levels occurring shortly after inhalation. THC acts on cannabinoid receptors (CB1 in the central nervous system and CB2 in peripheral tissues), modulating neurotransmitter release. Due to its fat solubility, THC accumulates in adipose tissue and may remain detectable for extended periods, especially in frequent users.
Management
Treatment is supportive. Reassurance is often sufficient, and benzodiazepines may be used for significant anxiety or agitation.
Key Points
Source
Marijuana is derived from the female Cannabis plant and can be used in various forms, including smoking, ingestion, or as a brewed preparation.
Typical Presentation
A common scenario involves recreational use in social settings, leading to feelings of relaxation, euphoria, altered perception, and impaired coordination. Users may describe changes in time perception and sensory experiences.
Clinical Features
Psychological effects include euphoria, calmness, altered perception, impaired attention, decreased concentration, and possible hallucinations. Physical findings may include increased heart rate, elevated blood pressure, dry mouth, rapid breathing, red eyes (conjunctival injection), and increased appetite. Coordination and motor function may also be impaired.
Mechanism of Action
The primary psychoactive component, delta-9-tetrahydrocannabinol (THC), is highly lipophilic and rapidly absorbed, with peak levels occurring shortly after inhalation. THC acts on cannabinoid receptors (CB1 in the central nervous system and CB2 in peripheral tissues), modulating neurotransmitter release. Due to its fat solubility, THC accumulates in adipose tissue and may remain detectable for extended periods, especially in frequent users.
Management
Treatment is supportive. Reassurance is often sufficient, and benzodiazepines may be used for significant anxiety or agitation.
Key Points
- Cannabis can be consumed by smoking, ingestion, or brewing into beverages.
- Oral use has a delayed onset (typically 1–3 hours) and may lead to stronger or unpredictable effects.
- Marijuana may sometimes be contaminated with other substances such as PCP or stimulants.
- Substances marketed as “formaldehyde-treated” marijuana are often actually contaminated with PCP rather than formaldehyde itself.
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Toxicology – Pancreatitis and Pancreatic Toxins
Overview
Pancreatitis is inflammation of the pancreas with multiple possible causes. While many cases are due to common conditions like gallstones and alcohol use, toxins, drugs, and metabolic abnormalities also play significant roles.
Common Causes
Gallstones
Gallstones are one of the leading causes of pancreatitis and, together with alcohol, account for the majority of cases.
Ethanol (Alcohol)
Alcohol is a major contributor to both acute and chronic pancreatitis due to its direct toxic effects on pancreatic cells.
Idiopathic
In some cases, no clear cause can be identified despite thorough evaluation.
Trauma
Blunt or penetrating injury to the abdomen can damage the pancreas and trigger inflammation.
Steroids and Hormones
Both corticosteroids and certain hormonal therapies have been associated with pancreatitis.
Infections
Viruses such as mumps, cytomegalovirus (CMV), and coxsackievirus can lead to pancreatic inflammation.
Malignancy
Pancreatic cancer may present with or contribute to pancreatitis and generally carries a poor prognosis.
Autoimmune Causes
Autoimmune pancreatitis is a form of chronic inflammation that often responds well to steroid therapy.
Scorpion Envenomation
Although uncommon, scorpion stings have been reported to trigger pancreatitis.
Metabolic Causes
Hypercalcemia
Elevated calcium levels, often due to hyperparathyroidism, can precipitate pancreatitis.
Hypertriglyceridemia
Very high triglyceride levels (typically >1,000 mg/dL) are a well-recognized cause.
Procedural Causes
Post-ERCP
Pancreatitis may occur after endoscopic retrograde cholangiopancreatography (ERCP), with a notable incidence in clinical practice.
Drug-Induced Pancreatitis
Common Drug Classes
Corticosteroids, antiretroviral (HIV) medications, chemotherapeutic agents, and thiazide diuretics are associated with pancreatic inflammation.
Specific Medications
Drugs known to cause pancreatitis include azathioprine, carbamazepine, cisplatin, didanosine, lamivudine, mercaptopurine, mesalamine, pentamidine, sulindac, tetracycline, valproic acid, and steroids.
Overview
Pancreatitis is inflammation of the pancreas with multiple possible causes. While many cases are due to common conditions like gallstones and alcohol use, toxins, drugs, and metabolic abnormalities also play significant roles.
Common Causes
Gallstones
Gallstones are one of the leading causes of pancreatitis and, together with alcohol, account for the majority of cases.
Ethanol (Alcohol)
Alcohol is a major contributor to both acute and chronic pancreatitis due to its direct toxic effects on pancreatic cells.
Idiopathic
In some cases, no clear cause can be identified despite thorough evaluation.
Trauma
Blunt or penetrating injury to the abdomen can damage the pancreas and trigger inflammation.
Steroids and Hormones
Both corticosteroids and certain hormonal therapies have been associated with pancreatitis.
Infections
Viruses such as mumps, cytomegalovirus (CMV), and coxsackievirus can lead to pancreatic inflammation.
Malignancy
Pancreatic cancer may present with or contribute to pancreatitis and generally carries a poor prognosis.
Autoimmune Causes
Autoimmune pancreatitis is a form of chronic inflammation that often responds well to steroid therapy.
Scorpion Envenomation
Although uncommon, scorpion stings have been reported to trigger pancreatitis.
Metabolic Causes
Hypercalcemia
Elevated calcium levels, often due to hyperparathyroidism, can precipitate pancreatitis.
Hypertriglyceridemia
Very high triglyceride levels (typically >1,000 mg/dL) are a well-recognized cause.
Procedural Causes
Post-ERCP
Pancreatitis may occur after endoscopic retrograde cholangiopancreatography (ERCP), with a notable incidence in clinical practice.
Drug-Induced Pancreatitis
Common Drug Classes
Corticosteroids, antiretroviral (HIV) medications, chemotherapeutic agents, and thiazide diuretics are associated with pancreatic inflammation.
Specific Medications
Drugs known to cause pancreatitis include azathioprine, carbamazepine, cisplatin, didanosine, lamivudine, mercaptopurine, mesalamine, pentamidine, sulindac, tetracycline, valproic acid, and steroids.
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Toxicology – QT Interval Prolongation on ECG
Overview
The QT interval represents the total time for ventricular depolarization and repolarization, measured from the beginning of the Q wave to the end of the T wave. Because it varies with heart rate, the corrected QT (QTc) is used for accuracy. Normal QTc is generally less than 420 milliseconds. Prolongation occurs when potassium channel activity is impaired, delaying repolarization. When the QTc exceeds 500 milliseconds, there is a significant risk of torsades de pointes, a potentially life-threatening ventricular arrhythmia.
High-Risk Medications
Macrolide Antibiotics
Agents such as erythromycin and clarithromycin are well-known to prolong the QT interval.
Butyrophenones
Drugs like haloperidol, droperidol, and domperidone can significantly increase QT duration.
Class Ia Antiarrhythmics
Quinidine, procainamide, and disopyramide prolong cardiac repolarization and increase arrhythmia risk.
Class Ic Antiarrhythmics
Flecainide, propafenone, and moricizine can also contribute to QT prolongation.
Class III Antiarrhythmics
Medications such as amiodarone, sotalol, ibutilide, dofetilide, and dronedarone are strongly associated with QT prolongation.
Methadone
This opioid is a notable cause of QT prolongation and increases risk of torsades de pointes.
Moderate-Risk Medications
Fluoroquinolone Antibiotics
Ciprofloxacin, levofloxacin, moxifloxacin, and gatifloxacin may prolong the QT interval.
Selective Serotonin Reuptake Inhibitors (SSRIs)
Fluoxetine, paroxetine, sertraline, and particularly citalopram (and less commonly escitalopram) are associated with QT prolongation.
Atypical Antipsychotics
Quetiapine, risperidone, and ziprasidone may increase QT duration.
Other Agents
Azithromycin, lithium, octreotide, and tizanidine have also been implicated in QT prolongation.
Management
Intravenous magnesium sulfate is the treatment of choice. For QTc prolongation (>500 ms), 2 g IV may be administered and repeated every 6 hours until normalization. In cases of torsades de pointes, 2 g IV should be given rapidly (over about 60 seconds) and repeated every 5–15 minutes as needed. Continuous infusion may be required for persistent arrhythmias.
Mechanism of Treatment
Magnesium stabilizes cardiac membranes and suppresses abnormal electrical activity without significantly affecting heart rate or directly shortening the QT interval.
Key Points
Overview
The QT interval represents the total time for ventricular depolarization and repolarization, measured from the beginning of the Q wave to the end of the T wave. Because it varies with heart rate, the corrected QT (QTc) is used for accuracy. Normal QTc is generally less than 420 milliseconds. Prolongation occurs when potassium channel activity is impaired, delaying repolarization. When the QTc exceeds 500 milliseconds, there is a significant risk of torsades de pointes, a potentially life-threatening ventricular arrhythmia.
High-Risk Medications
Macrolide Antibiotics
Agents such as erythromycin and clarithromycin are well-known to prolong the QT interval.
Butyrophenones
Drugs like haloperidol, droperidol, and domperidone can significantly increase QT duration.
Class Ia Antiarrhythmics
Quinidine, procainamide, and disopyramide prolong cardiac repolarization and increase arrhythmia risk.
Class Ic Antiarrhythmics
Flecainide, propafenone, and moricizine can also contribute to QT prolongation.
Class III Antiarrhythmics
Medications such as amiodarone, sotalol, ibutilide, dofetilide, and dronedarone are strongly associated with QT prolongation.
Methadone
This opioid is a notable cause of QT prolongation and increases risk of torsades de pointes.
Moderate-Risk Medications
Fluoroquinolone Antibiotics
Ciprofloxacin, levofloxacin, moxifloxacin, and gatifloxacin may prolong the QT interval.
Selective Serotonin Reuptake Inhibitors (SSRIs)
Fluoxetine, paroxetine, sertraline, and particularly citalopram (and less commonly escitalopram) are associated with QT prolongation.
Atypical Antipsychotics
Quetiapine, risperidone, and ziprasidone may increase QT duration.
Other Agents
Azithromycin, lithium, octreotide, and tizanidine have also been implicated in QT prolongation.
Management
Intravenous magnesium sulfate is the treatment of choice. For QTc prolongation (>500 ms), 2 g IV may be administered and repeated every 6 hours until normalization. In cases of torsades de pointes, 2 g IV should be given rapidly (over about 60 seconds) and repeated every 5–15 minutes as needed. Continuous infusion may be required for persistent arrhythmias.
Mechanism of Treatment
Magnesium stabilizes cardiac membranes and suppresses abnormal electrical activity without significantly affecting heart rate or directly shortening the QT interval.
Key Points
- QT prolongation increases the risk of torsades de pointes, especially when QTc exceeds 500 ms.
- Among SSRIs, citalopram is most strongly associated with QT prolongation.
- Octreotide has also been recognized as a potential contributor to QT interval prolongation.
