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Tricyclic antidepressant overdose — SCE Acute Medicine MCQ

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HardToxicology and OverdoseTricyclic antidepressant overdoseSCE Acute Medicine

A 58-year-old woman is brought in 90 minutes after taking an unknown quantity of amitriptyline. She is hypotensive and drowsy; ECG shows QRS 164 ms with a prominent terminal R wave in aVR. Which treatment most directly reverses the cardiotoxic mechanism?

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Correct answer: A — Intravenous sodium bicarbonate

Amitriptyline blocks fast cardiac sodium channels, causing QRS widening, hypotension and ventricular arrhythmia. Intravenous sodium bicarbonate increases sodium availability and alkalinises serum, reducing drug binding to sodium channels. Repeat boluses are guided by QRS narrowing, haemodynamics and a mildly alkalinaemic target while ventilation and electrolytes are controlled.

Reference: https://bnf.nice.org.uk/treatment-summaries/poisoning-emergency-treatment/