A 19-year-old man is brought in comatose after a suspected tricyclic antidepressant overdose. ECG shows sinus tachycardia with a QRS duration of 140 ms and blood pressure is 84/50 mmHg. The single most appropriate immediate treatment is:

• A Intravenous calcium gluconate
• B Intravenous sodium bicarbonate bolus ✓
• C Oral activated charcoal alone with cardiac monitoring
• D Intravenous amiodarone infusion

Explanation

TCA cardiotoxicity results from fast sodium channel blockade, producing QRS widening, hypotension, and arrhythmias. Intravenous sodium bicarbonate alkalinises the blood and raises extracellular sodium, overcoming the channel blockade; it is the first-line therapy for QRS widening above 100 ms or shock. Amiodarone is avoided because of additive sodium channel blockade, calcium treats hyperkalaemia and calcium blocker toxicity, and charcoal alone cannot address established cardiotoxicity.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

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