In tricyclic antidepressant (TCA) toxicity, which treatment helps correct QRS prolongation?

• A. Sodium bicarbonate
• B. Diphenhydramine
• C. Amiodarone
• D. Glucose

Answer: (A)

QRS prolongation in TCA toxicity comes from blockade of cardiac fast sodium channels, which slows conduction and widens the QRS. The treatment that best addresses this is sodium bicarbonate because it provides a sodium load to overcome the channel blockade and alkalinizes the serum. The extra extracellular sodium helps push the drug off the sodium channels, improving conduction, while the higher pH also reduces the drug’s interaction with those channels. In practice, give an IV bicarbonate bolus (roughly 1–2 mEq/kg, commonly 50–100 mEq) and repeat as needed, aiming for a serum pH around 7.45–7.55 and careful monitoring of electrolytes and ECG. This approach narrows the QRS and lowers the risk of life-threatening arrhythmias in TCA overdose.