amiodarone × sertraline

Both drugs prolong the QT interval (amiodarone strongly via IKr potassium channel blockade; sertraline modestly). Additive QT prolongation increases the risk of torsades de pointes, especially with hypokalemia and hypomagnesemia.

Obtain a baseline ECG (QTc) and repeat 1–2 weeks after starting or increasing sertraline. QTc > 500 ms or an increase > 60 ms warrants reassessment. Keep potassium ≥ 4.0 mmol/L and magnesium ≥ 1.0 mmol/L. Antidepressant alternatives with minimal QT effect include mirtazapine and bupropion.