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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 – Organophosphate Poisoning
Sources
Organophosphates are found in both chemical warfare agents—such as sarin, soman, tabun, and VX—and commonly used agricultural insecticides including diazinon, dichlorvos, malathion, and parathion.
Typical Presentation
A classic case involves accidental ingestion or exposure, often in agricultural settings. Patients may present with altered mental status, pinpoint pupils (miosis), excessive secretions, slow heart rate, bronchorrhea, sweating, and respiratory distress requiring airway support.
Mechanism of Action
Organophosphates inhibit acetylcholinesterase at synapses in both the central and peripheral nervous systems, as well as in red blood cells. This leads to accumulation of acetylcholine. Over time, the enzyme undergoes “aging,” making the inhibition irreversible.
Clinical Features
Muscarinic effects are most prominent and include miosis, bradycardia, excessive salivation, sweating, bronchorrhea, bronchospasm, gastrointestinal symptoms (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 toxicity may be fatal.
Management
Treatment begins with decontamination and supportive care. Atropine is administered to counteract muscarinic effects, 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 seen. Pralidoxime is used to reverse neuromuscular effects and is given intravenously over 30 minutes (1–2 g in adults, 20–50 mg/kg in children). Benzodiazepines, especially diazepam, are used for seizures, agitation, and muscle spasms. Repeated dosing or continuous infusions may be necessary. Autoinjectors containing atropine and pralidoxime are commonly used in emergency and military settings.
Sources
Organophosphates are found in both chemical warfare agents—such as sarin, soman, tabun, and VX—and commonly used agricultural insecticides including diazinon, dichlorvos, malathion, and parathion.
Typical Presentation
A classic case involves accidental ingestion or exposure, often in agricultural settings. Patients may present with altered mental status, pinpoint pupils (miosis), excessive secretions, slow heart rate, bronchorrhea, sweating, and respiratory distress requiring airway support.
Mechanism of Action
Organophosphates inhibit acetylcholinesterase at synapses in both the central and peripheral nervous systems, as well as in red blood cells. This leads to accumulation of acetylcholine. Over time, the enzyme undergoes “aging,” making the inhibition irreversible.
Clinical Features
Muscarinic effects are most prominent and include miosis, bradycardia, excessive salivation, sweating, bronchorrhea, bronchospasm, gastrointestinal symptoms (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 toxicity may be fatal.
Management
Treatment begins with decontamination and supportive care. Atropine is administered to counteract muscarinic effects, 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 seen. Pralidoxime is used to reverse neuromuscular effects and is given intravenously over 30 minutes (1–2 g in adults, 20–50 mg/kg in children). Benzodiazepines, especially diazepam, are used for seizures, agitation, and muscle spasms. Repeated dosing or continuous infusions may be necessary. Autoinjectors containing atropine and pralidoxime are commonly used in emergency and military settings.
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Toxicology – Anticholinergic Toxidrome
Common Sources
Anticholinergic toxicity can arise from a wide range of medications and substances, including antihistamines, gastrointestinal and genitourinary antispasmodics, tricyclic antidepressants, antiparkinsonian drugs, skeletal muscle relaxants, antivertigo agents, antipsychotics, and plants such as Jimson weed.
Typical Presentation
A common scenario involves a teenager ingesting Jimson weed seeds for recreational purposes. Within a few hours, the individual may develop abnormal behavior, confusion, and delirium, often appearing to respond to internal stimuli. Physical findings may include dilated pupils, dry lips, rapid heart rate, and absent bowel sounds. Urinary retention is also common and may be significant.
Clinical Features
Key signs and symptoms include mydriasis, dry mucous membranes, tachycardia, hyperthermia, hypertension, decreased or absent bowel sounds, warm flushed skin, urinary retention, and altered mental status ranging from confusion to hallucinations and delirium. Severe cases may involve seizures.
Mechanism of Action
These agents block the effects of acetylcholine at muscarinic receptors within the autonomic nervous system. This affects multiple organ systems, including the brain, heart, glands, and smooth muscle of the gastrointestinal and genitourinary tracts. At higher doses, nicotinic receptor blockade may also occur. Atropine is the classic example of an anticholinergic agent.
Management
Treatment is primarily supportive. This includes intravenous fluids, bladder decompression with a Foley catheter if urinary retention is present, cooling measures for hyperthermia, and benzodiazepines for agitation or seizures. Activated charcoal may be used to reduce further absorption if appropriate. Physostigmine, a reversible acetylcholinesterase inhibitor that crosses the blood–brain barrier, may be used as an antidote in selected cases.
Key Points
Common Sources
Anticholinergic toxicity can arise from a wide range of medications and substances, including antihistamines, gastrointestinal and genitourinary antispasmodics, tricyclic antidepressants, antiparkinsonian drugs, skeletal muscle relaxants, antivertigo agents, antipsychotics, and plants such as Jimson weed.
Typical Presentation
A common scenario involves a teenager ingesting Jimson weed seeds for recreational purposes. Within a few hours, the individual may develop abnormal behavior, confusion, and delirium, often appearing to respond to internal stimuli. Physical findings may include dilated pupils, dry lips, rapid heart rate, and absent bowel sounds. Urinary retention is also common and may be significant.
Clinical Features
Key signs and symptoms include mydriasis, dry mucous membranes, tachycardia, hyperthermia, hypertension, decreased or absent bowel sounds, warm flushed skin, urinary retention, and altered mental status ranging from confusion to hallucinations and delirium. Severe cases may involve seizures.
Mechanism of Action
These agents block the effects of acetylcholine at muscarinic receptors within the autonomic nervous system. This affects multiple organ systems, including the brain, heart, glands, and smooth muscle of the gastrointestinal and genitourinary tracts. At higher doses, nicotinic receptor blockade may also occur. Atropine is the classic example of an anticholinergic agent.
Management
Treatment is primarily supportive. This includes intravenous fluids, bladder decompression with a Foley catheter if urinary retention is present, cooling measures for hyperthermia, and benzodiazepines for agitation or seizures. Activated charcoal may be used to reduce further absorption if appropriate. Physostigmine, a reversible acetylcholinesterase inhibitor that crosses the blood–brain barrier, may be used as an antidote in selected cases.
Key Points
- Activated charcoal should only be administered if bowel function is intact.
- Jimson weed and similar substances are sometimes misused recreationally, especially among adolescents.
- In elderly patients, unexplained confusion and urinary retention should raise suspicion for anticholinergic toxicity, particularly after starting new medications such as antihistamines or cold remedies.
- Anticholinergic drugs should be used cautiously in older adults due to the risk of worsening cognitive impairment.
- Classic description: “dry as a bone, red as a beet, hot as a hare, mad as a hatter, and blind as a bat.”
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Toxicology – Single-Dose Lethal Toxins
Clinicians should be aware that even a single dose of certain medications can be fatal, particularly in infants and children. The following are important high-risk agents and their mechanisms:
Alpha-2 Adrenergic Agonists (e.g., Clonidine)
These centrally acting agents can lead to significant central nervous system depression, bradycardia, hypotension, and respiratory depression.
Beta-Blockers (e.g., Propranolol)
Propranolol is especially dangerous due to its lipophilic nature, allowing central nervous system penetration. Toxicity may result in hypoglycemia, altered mental status, bradycardia, hypotension, heart block, and seizures.
Calcium Channel Blockers
These drugs impair cardiac conduction and contractility, causing bradycardia, hypotension, and heart block. Hyperglycemia may also occur due to reduced insulin release.
Sulfonylureas
These oral hypoglycemic agents can cause profound and prolonged hypoglycemia, leading to altered mental status, seizures, and coma.
Opioids (Narcotics)
Opioids, including heroin and prescription medications, can cause severe respiratory depression or arrest. Ingestion of transdermal patches is a particular risk in children.
Nicotine
Nicotine toxicity can produce cholinergic symptoms such as muscle fasciculations, along with cardiovascular and neurological effects.
Tricyclic Antidepressants (TCAs)
TCAs block cardiac sodium channels, resulting in conduction delays, widened QRS complexes, and potentially fatal arrhythmias.
Salicylates
Substances such as oil of wintergreen and certain bismuth-containing compounds disrupt oxidative phosphorylation, leading to metabolic acidosis, cerebral edema, pulmonary edema, seizures, and death.
Camphor
Camphor ingestion can rapidly cause nausea, vomiting, tachycardia, central nervous system depression, and seizures, especially in children.
Colchicine and Podophyllin
These agents disrupt microtubule formation, impairing cell division. Toxicity presents with gastrointestinal symptoms and can progress to hypotension and multisystem organ failure.
Acetylcholinesterase Inhibitors (AChEIs)
Medications used for Alzheimer disease can lead to a cholinergic toxidrome in overdose, with symptoms including bradycardia, bronchorrhea, and altered mental status.
Quinine and Quinidine
These agents block sodium channels, leading to cardiac conduction abnormalities such as QRS widening, QT prolongation, and potentially life-threatening arrhythmias.
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Clinicians should be aware that even a single dose of certain medications can be fatal, particularly in infants and children. The following are important high-risk agents and their mechanisms:
Alpha-2 Adrenergic Agonists (e.g., Clonidine)
These centrally acting agents can lead to significant central nervous system depression, bradycardia, hypotension, and respiratory depression.
Beta-Blockers (e.g., Propranolol)
Propranolol is especially dangerous due to its lipophilic nature, allowing central nervous system penetration. Toxicity may result in hypoglycemia, altered mental status, bradycardia, hypotension, heart block, and seizures.
Calcium Channel Blockers
These drugs impair cardiac conduction and contractility, causing bradycardia, hypotension, and heart block. Hyperglycemia may also occur due to reduced insulin release.
Sulfonylureas
These oral hypoglycemic agents can cause profound and prolonged hypoglycemia, leading to altered mental status, seizures, and coma.
Opioids (Narcotics)
Opioids, including heroin and prescription medications, can cause severe respiratory depression or arrest. Ingestion of transdermal patches is a particular risk in children.
Nicotine
Nicotine toxicity can produce cholinergic symptoms such as muscle fasciculations, along with cardiovascular and neurological effects.
Tricyclic Antidepressants (TCAs)
TCAs block cardiac sodium channels, resulting in conduction delays, widened QRS complexes, and potentially fatal arrhythmias.
Salicylates
Substances such as oil of wintergreen and certain bismuth-containing compounds disrupt oxidative phosphorylation, leading to metabolic acidosis, cerebral edema, pulmonary edema, seizures, and death.
Camphor
Camphor ingestion can rapidly cause nausea, vomiting, tachycardia, central nervous system depression, and seizures, especially in children.
Colchicine and Podophyllin
These agents disrupt microtubule formation, impairing cell division. Toxicity presents with gastrointestinal symptoms and can progress to hypotension and multisystem organ failure.
Acetylcholinesterase Inhibitors (AChEIs)
Medications used for Alzheimer disease can lead to a cholinergic toxidrome in overdose, with symptoms including bradycardia, bronchorrhea, and altered mental status.
Quinine and Quinidine
These agents block sodium channels, leading to cardiac conduction abnormalities such as QRS widening, QT prolongation, and potentially life-threatening arrhythmias.
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Toxicology – Odor-Associated Toxins
Bitter Almond Odor
This characteristic smell is classically associated with cyanide exposure, although a significant portion of the population cannot detect it due to genetic variation.
Garlic-Like Odor
Substances such as phosphorus, arsenic compounds (arsine), organophosphates, selenium, thallium, and dimethyl sulfoxide (DMSO) may produce a garlic-like smell.
Rotten Egg Odor
Hydrogen sulfide, carbon disulfide, mercaptans, disulfiram, and N-acetylcysteine are known to emit a sulfurous “rotten egg” odor.
Fruity Odor
A sweet or fruity smell may be present in exposures involving nitriles, ketoacidosis, ethanol, isopropanol, chloroform, trichloroethane, paraldehyde, chloral hydrate, methyl bromide, and certain nitrites.
Fishy or Musty Odor
Compounds such as zinc phosphide, aluminum phosphide, and nickel carbonyl may produce a fishy or musty scent.
Ammonia-Like Odor
Ammonia exposure is associated with a sharp, pungent odor that is easily recognizable.
Mothball Odor
Naphthalene, camphor, and p-dichlorobenzene commonly produce the classic mothball smell.
Minty Odor
Methylsalicylate (oil of wintergreen) and menthol can give off a distinct mint-like aroma.
Disinfectant Odor
Phenol and creosote are associated with a strong antiseptic or disinfectant-like smell.
Burnt Rope Odor
This smell may be linked to marijuana or opium exposure.
Carrot-Like Odor
Cicutoxin, found in water hemlock, can produce an odor reminiscent of carrots.
Hay-Like Odor
Phosgene exposure may be associated with a freshly cut hay smell.
Pear-Like Odor
Chloral hydrate may produce a scent resembling pears.
Pepper Odor
Exposure to riot control agents such as CS (tear gas) can result in a pepper-like smell.
Pine Odor
Pine oil is associated with a characteristic pine-like scent.
Peanut Butter Odor
Vacor, a rodenticide, has been described as having a peanut butter-like odor.
Shoe Polish Odor
Nitrobenzene exposure may produce a smell similar to shoe polish.
Tobacco Odor
Nicotine-containing substances often have a distinct tobacco-like smell.
Vinegar Odor
Acetic acid and hydrofluoric acid may emit a sharp, vinegar-like odor.
Violet Odor
Turpentine metabolites excreted in urine may produce a violet-like scent.
New Car Smell
Chemicals such as benzene, cyclohexanone, and styrene, often found in new materials, can produce this recognizable odor.
PEARLS
Bitter Almond Odor
This characteristic smell is classically associated with cyanide exposure, although a significant portion of the population cannot detect it due to genetic variation.
Garlic-Like Odor
Substances such as phosphorus, arsenic compounds (arsine), organophosphates, selenium, thallium, and dimethyl sulfoxide (DMSO) may produce a garlic-like smell.
Rotten Egg Odor
Hydrogen sulfide, carbon disulfide, mercaptans, disulfiram, and N-acetylcysteine are known to emit a sulfurous “rotten egg” odor.
Fruity Odor
A sweet or fruity smell may be present in exposures involving nitriles, ketoacidosis, ethanol, isopropanol, chloroform, trichloroethane, paraldehyde, chloral hydrate, methyl bromide, and certain nitrites.
Fishy or Musty Odor
Compounds such as zinc phosphide, aluminum phosphide, and nickel carbonyl may produce a fishy or musty scent.
Ammonia-Like Odor
Ammonia exposure is associated with a sharp, pungent odor that is easily recognizable.
Mothball Odor
Naphthalene, camphor, and p-dichlorobenzene commonly produce the classic mothball smell.
Minty Odor
Methylsalicylate (oil of wintergreen) and menthol can give off a distinct mint-like aroma.
Disinfectant Odor
Phenol and creosote are associated with a strong antiseptic or disinfectant-like smell.
Burnt Rope Odor
This smell may be linked to marijuana or opium exposure.
Carrot-Like Odor
Cicutoxin, found in water hemlock, can produce an odor reminiscent of carrots.
Hay-Like Odor
Phosgene exposure may be associated with a freshly cut hay smell.
Pear-Like Odor
Chloral hydrate may produce a scent resembling pears.
Pepper Odor
Exposure to riot control agents such as CS (tear gas) can result in a pepper-like smell.
Pine Odor
Pine oil is associated with a characteristic pine-like scent.
Peanut Butter Odor
Vacor, a rodenticide, has been described as having a peanut butter-like odor.
Shoe Polish Odor
Nitrobenzene exposure may produce a smell similar to shoe polish.
Tobacco Odor
Nicotine-containing substances often have a distinct tobacco-like smell.
Vinegar Odor
Acetic acid and hydrofluoric acid may emit a sharp, vinegar-like odor.
Violet Odor
Turpentine metabolites excreted in urine may produce a violet-like scent.
New Car Smell
Chemicals such as benzene, cyclohexanone, and styrene, often found in new materials, can produce this recognizable odor.
PEARLS
- Approximately 40% of individuals are unable to detect the bitter almond odor of cyanide.
- Hydrogen sulfide exposure can quickly lead to olfactory fatigue, reducing the ability to perceive its smell.
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Toxicology – Seizure-Inducing Toxins
Cocaine
Cocaine lowers the seizure threshold through potent stimulation of the central nervous system, similar to other sympathomimetic agents.
Isoniazid
Isoniazid toxicity can cause severe, refractory seizures that are characteristically resistant to standard therapy and require treatment with pyridoxine.
Anticholinergics
Seizures may occur as a late and severe manifestation of anticholinergic toxicity.
Amphetamines
Amphetamines increase catecholamine release and significantly lower the seizure threshold, increasing the risk of seizures.
Organophosphates
These insecticides produce a cholinergic toxidrome and can lead to seizures due to excessive acetylcholine accumulation.
Ethanol Withdrawal
Seizures may develop within 6 to 48 hours after abrupt cessation of alcohol in dependent individuals.
Tricyclic Antidepressants (TCAs)
At high doses, TCAs can induce seizures, often occurring before serious cardiac complications such as arrhythmias or arrest.
Methylanthines
Agents such as theophylline can cause seizures in overdose due to central nervous system stimulation.
Phencyclidine (PCP)
Large doses of PCP may result in severe toxicity, including seizures, hyperthermia, coma, and death.
Lidocaine
Intravenous toxicity from local anesthetics like lidocaine can initially cause seizures, followed by cardiovascular collapse.
Camphor
Camphor exposure, especially in children, can lead to seizures due to increased absorption through ingestion or skin contact.
Sympathomimetics
This class of drugs broadly lowers the seizure threshold through increased adrenergic activity.
Benzodiazepine Withdrawal
Abrupt discontinuation of benzodiazepines can lead to withdrawal symptoms, including seizures. Use of flumazenil may precipitate acute withdrawal in dependent individuals.
Lithium
Severe lithium toxicity may present with neurological complications, including seizures.
Lindane
Lindane, used topically for lice and scabies, can cause seizures when absorbed in excessive amounts, particularly in infants and children.
Lead (Severe Toxicity)
Extremely elevated lead levels can result in neurological toxicity, including seizures.
Treatment
Benzodiazepines such as diazepam or lorazepam are first-line therapy for toxin-induced seizures. If seizures persist, phenobarbital is considered second-line. In refractory cases, propofol with airway protection may be required. Phenytoin and fosphenytoin are generally not effective for toxin-induced seizures. Pyridoxine should be administered when isoniazid or certain mushroom toxicities are suspected.
Cocaine
Cocaine lowers the seizure threshold through potent stimulation of the central nervous system, similar to other sympathomimetic agents.
Isoniazid
Isoniazid toxicity can cause severe, refractory seizures that are characteristically resistant to standard therapy and require treatment with pyridoxine.
Anticholinergics
Seizures may occur as a late and severe manifestation of anticholinergic toxicity.
Amphetamines
Amphetamines increase catecholamine release and significantly lower the seizure threshold, increasing the risk of seizures.
Organophosphates
These insecticides produce a cholinergic toxidrome and can lead to seizures due to excessive acetylcholine accumulation.
Ethanol Withdrawal
Seizures may develop within 6 to 48 hours after abrupt cessation of alcohol in dependent individuals.
Tricyclic Antidepressants (TCAs)
At high doses, TCAs can induce seizures, often occurring before serious cardiac complications such as arrhythmias or arrest.
Methylanthines
Agents such as theophylline can cause seizures in overdose due to central nervous system stimulation.
Phencyclidine (PCP)
Large doses of PCP may result in severe toxicity, including seizures, hyperthermia, coma, and death.
Lidocaine
Intravenous toxicity from local anesthetics like lidocaine can initially cause seizures, followed by cardiovascular collapse.
Camphor
Camphor exposure, especially in children, can lead to seizures due to increased absorption through ingestion or skin contact.
Sympathomimetics
This class of drugs broadly lowers the seizure threshold through increased adrenergic activity.
Benzodiazepine Withdrawal
Abrupt discontinuation of benzodiazepines can lead to withdrawal symptoms, including seizures. Use of flumazenil may precipitate acute withdrawal in dependent individuals.
Lithium
Severe lithium toxicity may present with neurological complications, including seizures.
Lindane
Lindane, used topically for lice and scabies, can cause seizures when absorbed in excessive amounts, particularly in infants and children.
Lead (Severe Toxicity)
Extremely elevated lead levels can result in neurological toxicity, including seizures.
Treatment
Benzodiazepines such as diazepam or lorazepam are first-line therapy for toxin-induced seizures. If seizures persist, phenobarbital is considered second-line. In refractory cases, propofol with airway protection may be required. Phenytoin and fosphenytoin are generally not effective for toxin-induced seizures. Pyridoxine should be administered when isoniazid or certain mushroom toxicities are suspected.
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Toxicology – Radiopaque Toxins
Iron
Iron preparations, particularly ferrous sulfate tablets, are clearly visible on radiographs. In large ingestions, they may accumulate and form a radiopaque pharmacobezoar.
Lead (Pb)
Lead-containing objects such as paint chips, bullets, toys, and figurines are highly radiopaque and easily identified on imaging.
Calcium
Calcium-containing substances are radiopaque, and significant ingestion can result in formation of a visible mass within the gastrointestinal tract.
Barium
Barium is inherently radiopaque and readily detectable on imaging studies.
Potassium
Potassium tablets may be visualized on radiographs, especially when ingested in large amounts, sometimes forming a pharmacobezoar.
Heavy Metals
Various heavy metals are radiopaque and can be identified on plain radiographs.
Enteric-Coated or Sustained-Release Tablets
Large ingestions of these formulations can lead to the formation of a radiopaque pharmacobezoar visible on imaging.
Arsenic
As a metallic element, arsenic is radiopaque and may be seen on radiographic studies.
Iodine
Iodine-containing compounds are radiopaque and can appear on imaging.
Chloral Hydrate and Halogenated Compounds
Certain halogenated substances, such as chloral hydrate and chloroform, may be detectable on x-ray due to their radiopaque properties.
Condom Packets (Body Packers)
Individuals who ingest drug-filled packets may show multiple uniform radiopaque densities on abdominal imaging.
Tricyclic Antidepressants (TCAs)
These medications may demonstrate variable radiopacity depending on dose and preparation.
Phosphorus
Phosphorus can be visualized on radiographs due to its radiopaque nature.
Iron
Iron preparations, particularly ferrous sulfate tablets, are clearly visible on radiographs. In large ingestions, they may accumulate and form a radiopaque pharmacobezoar.
Lead (Pb)
Lead-containing objects such as paint chips, bullets, toys, and figurines are highly radiopaque and easily identified on imaging.
Calcium
Calcium-containing substances are radiopaque, and significant ingestion can result in formation of a visible mass within the gastrointestinal tract.
Barium
Barium is inherently radiopaque and readily detectable on imaging studies.
Potassium
Potassium tablets may be visualized on radiographs, especially when ingested in large amounts, sometimes forming a pharmacobezoar.
Heavy Metals
Various heavy metals are radiopaque and can be identified on plain radiographs.
Enteric-Coated or Sustained-Release Tablets
Large ingestions of these formulations can lead to the formation of a radiopaque pharmacobezoar visible on imaging.
Arsenic
As a metallic element, arsenic is radiopaque and may be seen on radiographic studies.
Iodine
Iodine-containing compounds are radiopaque and can appear on imaging.
Chloral Hydrate and Halogenated Compounds
Certain halogenated substances, such as chloral hydrate and chloroform, may be detectable on x-ray due to their radiopaque properties.
Condom Packets (Body Packers)
Individuals who ingest drug-filled packets may show multiple uniform radiopaque densities on abdominal imaging.
Tricyclic Antidepressants (TCAs)
These medications may demonstrate variable radiopacity depending on dose and preparation.
Phosphorus
Phosphorus can be visualized on radiographs due to its radiopaque nature.
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Toxicology – Non-Anion Gap Metabolic Acidosis (HARD UP)
Hyperalimentation (TPN)
Total parenteral nutrition with excessive chloride content can result in hyperchloremic metabolic acidosis. Management involves reducing chloride and increasing acetate in the formulation. Regular monitoring with daily basic metabolic panels is important in these patients.
Acetazolamide
Acetazolamide inhibits carbonic anhydrase in the proximal tubule, leading to increased urinary bicarbonate loss and a non-anion gap metabolic acidosis. Patients may experience paresthesias in the extremities and a metallic taste.
Renal Tubular Acidosis (RTA)
Renal tubular dysfunction impairs acid and ammonia excretion, resulting in hyperchloremic metabolic acidosis. It is classified into Type I (distal, hypokalemic), Type II (proximal, hypokalemic), and Type IV (hyperkalemic). Type III is no longer recognized as a separate entity.
Diarrhea
Loss of bicarbonate through the gastrointestinal tract leads to non-anion gap metabolic acidosis. Treatment includes intravenous fluids and bicarbonate replacement.
Ureteroenteric Fistula
This condition can cause metabolic acidosis through several mechanisms: reabsorption of ammonium chloride from urine, exchange of chloride for bicarbonate in the bowel, and renal tubular impairment. Risk increases with prolonged urine exposure to bowel mucosa and greater surface area involvement.
Pancreaticoduodenal Fistula
Similar to diarrhea, this condition leads to bicarbonate loss and subsequent non-anion gap metabolic acidosis. Management focuses on fluid resuscitation and correction of electrolyte imbalances.
Hyperalimentation (TPN)
Total parenteral nutrition with excessive chloride content can result in hyperchloremic metabolic acidosis. Management involves reducing chloride and increasing acetate in the formulation. Regular monitoring with daily basic metabolic panels is important in these patients.
Acetazolamide
Acetazolamide inhibits carbonic anhydrase in the proximal tubule, leading to increased urinary bicarbonate loss and a non-anion gap metabolic acidosis. Patients may experience paresthesias in the extremities and a metallic taste.
Renal Tubular Acidosis (RTA)
Renal tubular dysfunction impairs acid and ammonia excretion, resulting in hyperchloremic metabolic acidosis. It is classified into Type I (distal, hypokalemic), Type II (proximal, hypokalemic), and Type IV (hyperkalemic). Type III is no longer recognized as a separate entity.
Diarrhea
Loss of bicarbonate through the gastrointestinal tract leads to non-anion gap metabolic acidosis. Treatment includes intravenous fluids and bicarbonate replacement.
Ureteroenteric Fistula
This condition can cause metabolic acidosis through several mechanisms: reabsorption of ammonium chloride from urine, exchange of chloride for bicarbonate in the bowel, and renal tubular impairment. Risk increases with prolonged urine exposure to bowel mucosa and greater surface area involvement.
Pancreaticoduodenal Fistula
Similar to diarrhea, this condition leads to bicarbonate loss and subsequent non-anion gap metabolic acidosis. Management focuses on fluid resuscitation and correction of electrolyte imbalances.
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Toxicology – Causes of Anion Gap Metabolic Acidosis
Alcohol (Ethanol)
Ethanol intoxication may lead to hypoglycemia, lactic acidosis, and alcoholic ketoacidosis, all of which contribute to an increased anion gap.
Aspirin (Salicylates)
Salicylate toxicity should be suspected in patients with anion gap metabolic acidosis and altered mental status. It typically produces a mixed disorder with metabolic acidosis and respiratory alkalosis due to direct stimulation of the respiratory center. It also increases renal loss of bicarbonate and potassium while promoting lactic and pyruvic acid formation.
Methanol
Methanol poisoning results in a high anion gap and hyperosmolar metabolic acidosis due to accumulation of formic acid, a toxic metabolite.
Ethylene Glycol
Commonly found in antifreeze, ethylene glycol is metabolized into glycolic, glyoxylic, and oxalic acids, producing a severe high anion gap metabolic acidosis.
Metformin
Metformin toxicity can lead to lactic acidosis by increasing production of lactate and other metabolic intermediates, particularly in patients with renal impairment or after contrast exposure.
Diabetic Ketoacidosis (DKA)
DKA occurs due to insulin deficiency, resulting in increased fatty acid metabolism and accumulation of ketoacids such as acetoacetate and β-hydroxybutyrate. Starvation and alcoholic ketosis can produce similar effects.
Uremia
Advanced kidney failure leads to accumulation of nitrogenous waste products and acids such as sulfuric and phosphoric acid, causing an anion gap metabolic acidosis.
Lactic Acidosis
Lactic acid accumulation from anaerobic metabolism is a common cause of anion gap acidosis and may result from hypoxia, hypoperfusion, toxins, or metabolic disorders.
Toluene
Toluene exposure, often through inhalation of solvents, increases production of organic acids such as benzoic and hippuric acid and may also cause renal tubular acidosis with chronic use.
Carbamazepine
Overdose of this antiepileptic drug can lead to metabolic acidosis along with hyperglycemia, ketonuria, altered mental status, seizures, and coma.
Isoniazid (INH)
Isoniazid toxicity can result in lactic acidosis, often accompanied by seizures and altered mental status.
Iron
Iron overdose contributes to metabolic acidosis through hypovolemia, hypotension, and the release of hydrogen ions during its metabolic conversion.
Paraldehyde
This older sedative-hypnotic agent, historically used for seizures, can contribute to anion gap metabolic acidosis in toxic exposures.
Alcohol (Ethanol)
Ethanol intoxication may lead to hypoglycemia, lactic acidosis, and alcoholic ketoacidosis, all of which contribute to an increased anion gap.
Aspirin (Salicylates)
Salicylate toxicity should be suspected in patients with anion gap metabolic acidosis and altered mental status. It typically produces a mixed disorder with metabolic acidosis and respiratory alkalosis due to direct stimulation of the respiratory center. It also increases renal loss of bicarbonate and potassium while promoting lactic and pyruvic acid formation.
Methanol
Methanol poisoning results in a high anion gap and hyperosmolar metabolic acidosis due to accumulation of formic acid, a toxic metabolite.
Ethylene Glycol
Commonly found in antifreeze, ethylene glycol is metabolized into glycolic, glyoxylic, and oxalic acids, producing a severe high anion gap metabolic acidosis.
Metformin
Metformin toxicity can lead to lactic acidosis by increasing production of lactate and other metabolic intermediates, particularly in patients with renal impairment or after contrast exposure.
Diabetic Ketoacidosis (DKA)
DKA occurs due to insulin deficiency, resulting in increased fatty acid metabolism and accumulation of ketoacids such as acetoacetate and β-hydroxybutyrate. Starvation and alcoholic ketosis can produce similar effects.
Uremia
Advanced kidney failure leads to accumulation of nitrogenous waste products and acids such as sulfuric and phosphoric acid, causing an anion gap metabolic acidosis.
Lactic Acidosis
Lactic acid accumulation from anaerobic metabolism is a common cause of anion gap acidosis and may result from hypoxia, hypoperfusion, toxins, or metabolic disorders.
Toluene
Toluene exposure, often through inhalation of solvents, increases production of organic acids such as benzoic and hippuric acid and may also cause renal tubular acidosis with chronic use.
Carbamazepine
Overdose of this antiepileptic drug can lead to metabolic acidosis along with hyperglycemia, ketonuria, altered mental status, seizures, and coma.
Isoniazid (INH)
Isoniazid toxicity can result in lactic acidosis, often accompanied by seizures and altered mental status.
Iron
Iron overdose contributes to metabolic acidosis through hypovolemia, hypotension, and the release of hydrogen ions during its metabolic conversion.
Paraldehyde
This older sedative-hypnotic agent, historically used for seizures, can contribute to anion gap metabolic acidosis in toxic exposures.
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Toxicology – Toxins Causing Cyanosis
Ergotamine
Ergot compounds can lead to acrocyanosis due to intense vasoconstriction, resembling a secondary Raynaud phenomenon affecting peripheral circulation.
Phenazopyridine
This urinary tract analgesic can induce methemoglobinemia, impairing oxygen delivery and resulting in cyanosis.
Aniline
Aniline, a chemical used in the production of dyes and polyurethane, can cause both methemoglobinemia and hemolytic anemia, contributing to cyanotic discoloration.
Dapsone
Dapsone, used in the treatment of leprosy and for Pneumocystis jirovecii pneumonia prophylaxis, is a well-known cause of methemoglobinemia.
Nitrates
Nitrates, sometimes present in contaminated well water, can induce methemoglobinemia, particularly in infants.
Nitrites
Nitrites are used therapeutically to induce methemoglobinemia in cyanide poisoning but may also be abused recreationally for their vasodilatory effects, leading to cyanosis.
Asphyxia
Conditions causing hypoxemia or impaired oxygen delivery increase levels of deoxygenated hemoglobin, resulting in cyanosis.
Treatment
Methylene blue is the treatment of choice for methemoglobinemia. It acts as a reducing agent, converting methemoglobin back to functional hemoglobin, and is typically administered at a dose of 1–2 mg/kg intravenously over 5 minutes.
Ergotamine
Ergot compounds can lead to acrocyanosis due to intense vasoconstriction, resembling a secondary Raynaud phenomenon affecting peripheral circulation.
Phenazopyridine
This urinary tract analgesic can induce methemoglobinemia, impairing oxygen delivery and resulting in cyanosis.
Aniline
Aniline, a chemical used in the production of dyes and polyurethane, can cause both methemoglobinemia and hemolytic anemia, contributing to cyanotic discoloration.
Dapsone
Dapsone, used in the treatment of leprosy and for Pneumocystis jirovecii pneumonia prophylaxis, is a well-known cause of methemoglobinemia.
Nitrates
Nitrates, sometimes present in contaminated well water, can induce methemoglobinemia, particularly in infants.
Nitrites
Nitrites are used therapeutically to induce methemoglobinemia in cyanide poisoning but may also be abused recreationally for their vasodilatory effects, leading to cyanosis.
Asphyxia
Conditions causing hypoxemia or impaired oxygen delivery increase levels of deoxygenated hemoglobin, resulting in cyanosis.
Treatment
Methylene blue is the treatment of choice for methemoglobinemia. It acts as a reducing agent, converting methemoglobin back to functional hemoglobin, and is typically administered at a dose of 1–2 mg/kg intravenously over 5 minutes.
