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Anticholinergic toxidrome — RACP Adult Medicine MCQ

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HardClinical pharmacology and toxicologyAnticholinergic toxidromeRACP Adult Medicine

An agitated patient has mydriasis, dry flushed skin and urinary retention after an unknown overdose. ECG shows QRS 148 ms and a terminal R wave in aVR. Which treatment is most appropriate before considering any antidote for delirium?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Give intravenous sodium bicarbonate and obtain urgent toxicology advice

Explanation lettering: B = shown as A · A = shown as B · E = shown as D · D = shown as E

A is correct because this ECG pattern suggests tricyclic sodium-channel blockade; sodium bicarbonate, resuscitation and poison-centre advice take priority. B is hazardous when conduction delay or a mixed overdose suggests tricyclic toxicity. C neither treats this toxidrome nor is safe in an unknown overdose. D ignores a potentially fatal electrophysiological problem. E can worsen shock and conduction disturbance. Physostigmine, where used, is reserved for carefully selected pure anticholinergic delirium under expert supervision.

Reference: Queensland Poisons Information Centre, Sodium bicarbonate for sodium-channel blockade: https://www.poisonsinfo.health.qld.gov.au/for-health-professionals/antidote-stocking-recommendations/sodium-bicarbonate