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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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