“We … cisapride with amiodarone, cimetidine (alternatives are famotidine, nizatidine, ranitidine or one of the … and verapamil (the dihydropyridine calcium antagonists are alternatives), grapefruit juice, isoniazid, metronidazole, quinine , quinupristin/dalfopristin and zileuton (montelukast is an alternative).Pharmacodynamic interactions with … have the potential to have additive effects on the QT interval.”