A patient on treatment with ketoconazole for a fungal disease develops Gastroesophageal Reflux Disease (GERD). Which of the following drugs should not be prescibed to him:
High-Yield Explanation
Answer is A (Cisapride) Co-administration of ketoconazole with cisapride is contraindicated secondary to an increased risk of cardiovascular adverse effects such as lorsades-de-pointes', ventricular tachycardia or ventricular fibrillation'. Drugs with High Risk of Generating Pharmakokinetic Interactions Drug Mechanism Examples Antacids Reduced absorption Antacids/tetracyclines Bile acid sequestrants Cholestyramine/digoxin Proton pump inhibitors Altered gastric pH Ketoconazole absorption decreased H2 -receptor blockers Rifampin Induction of Hepatic Decreased concentration and effects of : Warfarin Carbamazepine Metabolism Barbiturates Quinidine Phenytoin Cyclosporine St. John's wo Losaan Glutethimide Oral contraceptives Methadone Tricyclic antidepressants Inhibitors of CYP2D6 Increased effect of many 13 blockers Fluoxetine Decreased codeine effect Quinidine Cimetidine Inhibitor of multiple CYPs Increased concentration and effects of Warfarin Theophylline Phenytoin Ketoconazole, Itraconazole Inhibitor of CYP3A Increased concentration and toxicity of some Erythromycin, Clarithromycin Calcium channel blockers HMG-CoA reductase inhibitors, cyclosporine, cisapride, terjenadine (now withdrawn) Ritonavir Increased concentration and effects of indinavir (With ritonavir) Decreased clearance and dose requirement for cyclosporine (with calcium channel blockers) Allopurinol Xanthine oxidase inhibitor Azathioprine and 6-mercaptopurine toxicity Amiodarone Inhibitor of many CYPs and Decreased clearance (risk of toxicity) for Warfarin of P-glycoprotein Digoxin Quinidine Gemfibrazole CYP3A inhibition Rhabdomyolysis when co-prescribed with some HMG-CoA (and other fibrates) reductase Inhibitors Quinidine P-glycoprotein inhibition Risk of digoxin toxicity Amiodarone . Verapamil Cyclosporine Itraconazole Erythromycin Phenylbutazone Inhibition of renal tubular Increased risk of methotrexate toxicity with salicylate Probenecid transpo Salicylates