Anticholinergic Toxidrome

All combined, this is a scary patient. Often they are very agitated, flushed and uncooperative - Central East Prehospital Care Program

Anticholinergic Toxidrome
Anticholinergic Toxidrome

image by: Being a Doctor

HWN Suggests

Toxicology 101: Talking Tox with The Dantastic Mr. Tox & Howard

Really we are talking about antimuscarinics and NOT antinicotinic agents, which cause paralysis. Parasympathetics control all glandular secretions. A pure antimuscarinic like atropine will give you the classic textbook symptoms: “Everything in your body that makes juice, is blocked” (Rusyniak 2018). Symptoms include dry mouth armpit. Some body systems like the heart and the eye are dually innervated by the sympathetic and parasympathetic systems. Blocking cholinergic receptors (the parasympathetic system) leaves the sympathetic system without a counterbalance and hence tachycardia and mydriasis (dilated pupils).

However, many drugs (like quetiapine) may have sympatholytic effects…

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 Toxicology 101: Talking Tox with The Dantastic Mr. Tox & Howard

Pupils (anticholinergic vs sympathomimetic) – In the anticholinergic state, the pupillary constrictors are paralyzed, whereas in the sympathomimetic state, the dilators are being stimulated. When looking at the reaction to light, a sympathomimetic pupil will constrict and an anticholinergic pupil will remain dilated.

Benadryl OD

A single therapeutic adult dose of diphenhydramine ranges from 25 to 100 mg every six hours. Manifestations of toxicity may occur after ingestion of three to five times the daily dose. The fatal oral dose is estimated to be between 20 to 40 mg/kg.

EMCrit Project

???? Dilated pupils. ???? Delirium. ???? Tachycardia. ???? Dry skin – This is an essential element, which helps separate anticholinergic toxidromes from sympathomimetic toxidromes.

Life in the Fastlane

Anticholinergic Toxidrome was one of the first flashcards I designed. I wanted to make a play on the old mnemonic: mad as a hatter, hot as hell, red as a beat, dry as a bone, and blind as a bat. I thought of the opening scene from Fear and Loathing in Las Vegas,...


Anticholinergic toxicity is commonly seen in the emergency department but is rarely fatal.


Differential Diagnosis: Sympathomimetic toxicity, Red, dry skin and absent bowel sounds favors anticholinergic toxicity' Encephalitis. Head trauma. ETOH/sedative withdrawal. Neuroleptic Malignant Syndrome (NMS). Acute psychotic disorder.

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