A young adult is brought to the emergency department after ingesting an unknown quantity of amitriptyline. She is comatose with seizures, and the ECG shows a QRS duration of 140 ms with hypotension. The single most appropriate immediate therapy is:

• A Intravenous amiodarone
• B Oral activated charcoal with gastric lavage alone
• C Intravenous calcium gluconate
• D Intravenous sodium bicarbonate ✓

Explanation

Tricyclic antidepressant cardiotoxicity results from fast sodium channel blockade, producing QRS widening, hypotension, and arrhythmias. Intravenous sodium bicarbonate alkalinises the blood and raises sodium load, which displaces the drug from cardiac sodium channels and is the specific antidotal therapy; it narrows the QRS and improves blood pressure. Amiodarone is avoided because class III agents can worsen conduction abnormalities. Calcium treats calcium channel blocker toxicity, and charcoal alone does not reverse established cardiotoxicity.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.