Anticholinergic (Antimuscarinic) Toxicity — Pathway

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

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Full pathway

1. [Decision] Toxidrome severity / wide QRS
   Anticholinergic toxidrome — severe delirium / wide QRS? (Antagonism of M receptors (antihistamines/TCAs/antipsychotics/atropine-scopolamine/jimsonweed, etc.). Mnemonic: 'hot as a hare (anhidrotic hyperthermia), dry as a bone, red as a beet, blind as a bat (mydriasis), mad as a hatter (delirium/hallucinations/picking), full as a flask (urinary retention)' + tachycardia, reduced bowel sounds. Dry skin + reduced bowel sounds distinguish it from sympathomimetic toxicity. Diphenhydramine/TCAs cause wide QRS from sodium-channel blockade (check ECG).)
   • Severe agitation-delirium / hyperthermia / wide QRS → Severe → benzodiazepines / bicarbonate
   • Mild–moderate → Mild–moderate · support
2. [End] Mild–moderate · support
   Mild–moderate: mainly supportive — monitoring, fluids, cooling, check ECG; activated charcoal if early (<1 h, airway protected); benzodiazepines for agitation. Catheterize for urinary retention. Central symptoms may resolve later than peripheral ones, so observe.
3. [End] Severe → benzodiazepines / bicarbonate
   Severe agitation-delirium/hyperthermia/seizures: benzodiazepines first-line for agitation/seizures + active cooling; wide QRS (diphenhydramine/TCA sodium-channel blockade) → bicarbonate. Physostigmine is for severe pure anticholinergic delirium — contraindicated with TCA/wide QRS/sodium-channel blockade, conduction block, asthma, intestinal/bladder obstruction (causes asystole/seizures), needs ECG monitoring with atropine ready. ICU support.

Source guidelines & references

• Anticholinergic toxicity (EMCrit IBCC; StatPearls; CHEMM)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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