You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is 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? and explain in detail?
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 Cisapride was previously used for the treatment of GERD but it has been withdrawn in some countries due to its QT prolonging action.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.