Drug implicated in prolonging QT interval is:

Ans. (C) Cisapride(Ref: KDT 8th/e p715)Cisapride is a 5HT4 agonist that is useful as a prokinetic agent. At high plasma concentration, it can block cardiac K+ channels leading to polymorphic ventricular tachycardia (torsades de pointes). It is manifested in the ECG as QT prolongation. Therefore, cisapride should not be combined with microsomal enzyme inhibitors like erythromycin and ketoconazole. Other important drugs causing QT prolongation areTerfenadineAstemizoleZiprasidone