Drug interactions between cilostazol and Prilosec

ADJUST DOSE: Coadministration with inhibitors of CYP450 3A4 and/or 2C19 may increase the plasma concentrations of cilostazol and or its pharmacologically active metabolites, which are substrates of these isoenzymes. The possibility of prolonged and/or increased pharmacologic effects of cilostazol should be considered. In pharmacokinetic studies, pretreatment with a 400 mg priming dose of ketoconazole (a potent CYP450 3A4 inhibitor) one day prior to coadministration of single doses of ketoconazole 400 mg and cilostazol 100 mg resulted in a 94% increase in cilostazol peak plasma concentration (Cmax) and a 117% increase in cilostazol systemic exposure (AUC). Coadministration of the less potent inhibitor erythromycin (500 mg every 8 hours) with a single 100 mg dose of cilostazol resulted in a 47% and 73% increase in cilostazol Cmax and AUC, respectively, while AUC of 4-trans-hydroxy-cilostazol (an active metabolite with 1/5 the pharmacologic activity) increased by 141% as a result of the inhibition of cilostazol metabolism via CYP450 3A4. Coadministration with 180 mg of diltiazem, a moderate CYP450 3A4 inhibitor, decreased cilostazol clearance by 30% and increased its Cmax by 30% and AUC by 40%. In contrast, cilostazol metabolism was not significantly affected when coadministered with omeprazole, a potent CYP450 2C19 inhibitor, but the systemic exposure to 3,4-dehydro-cilostazol (the most active metabolite of cilostazol) was increased by 69%.

MANAGEMENT: The manufacturer recommends a 50% dosage reduction of cilostazol (i.e., 50 mg twice a day) in patients receiving the CYP450 3A4 inhibitors ketoconazole, itraconazole, erythromycin, and diltiazem, or the 2C19 inhibitor omeprazole. Other potent inhibitors include clarithromycin, telithromycin, troleandomycin, fluconazole, miconazole, voriconazole, delavirdine, nefazodone, and protease inhibitors. Close clinical and laboratory monitoring is advised whenever a potent CYP450 3A4 and/or 2C19 inhibitor is added to or withdrawn from cilostazol therapy. Patients should be advised to contact their physician if they experience adverse effects of cilostazol such as headache, dizziness, nausea, diarrhea, or irregular heartbeat.