A 45-year-old woman with treatment-resistant depression is prescribed a tricyclic antidepressant (TCA). She accidentally overdoses. She presents with QRS widening (>120 ms), hypotension, and ventricular arrhythmias. What is the CORRECT treatment for TCA-induced cardiac toxicity?

• A Physostigmine
• B Sodium bicarbonate IV bolus ✓
• C Flumazenil
• D Activated charcoal alone is sufficient

Explanation

TCAs in overdose cause sodium channel blockade (fast Na+ channel in cardiac conduction), leading to QRS widening and ventricular arrhythmias. The specific antidote is IV sodium bicarbonate, which works by (1) increasing extracellular sodium concentration, overcoming the sodium channel block, and (2) alkalinization, which reduces TCA binding to sodium channels (TCAs bind less at alkaline pH). Target: serum pH 7.45–7.55. Physostigmine is contraindicated in TCA overdose (can worsen arrhythmias and cause seizures by reversing anticholinergic effects abruptly). Flumazenil is for benzodiazepine overdose.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.