QT interval prolongation and torsades de pointes due to a coadministration of metronidazole and amiodarone.

This report documents the occurrence of torsades de pointes (TdP) caused by marked QT interval prolongation in the case of a 71-year-old woman receiving both metronidazole and amiodarone for the treatment of pseudomembranous colitis and paroxysmal atrial fibrillation. The case highlights a previously unknown drug interaction. The role of inhibition of cytochrome P-450 CYP3A4 is discussed.