A patient is on long term ketoconazole therapy. He developed gastroesophageal reflux disease (GERD). Which of the following drug should not be used for treatment of GERD in this patient?

Cisapride, mosapride, renzapride, prucalopride and tegaserod are 5-HT4 agonistic drugs with no action on D2 receptors (no antiemetic propey). These drugs increase whole GI motility including colon. Cisapride was previously used for the treatment of GERD but it has been withdrawn in some countries due to its QT prolonging action. It is metabolized by CYP 3A4 and therefore should not be administered with microsomal enzyme inhibitors like ketoconazole and erythromycin (increased chances of Torsades' de pointes, an arrhythmia with QT prolongation). Mosapride and renzapride do not prolong QT interval.