Drug Interactions between conivaptan and ospemifene

MONITOR: Coadministration with potent inhibitors of CYP450 3A4 may increase the plasma concentrations of ospemifene, which is partially metabolized by the isoenzyme. In 12 postmenopausal women given the potent CYP450 3A4 inhibitor ketoconazole 400 mg once daily for 8 days, administration of ospemifene 60 mg after breakfast on day 5 of ketoconazole treatment resulted in 1.5- and 1.4-fold increases in ospemifene peak plasma concentration (Cmax) and systemic exposure (AUC), respectively, compared to administration of ospemifene alone. The potential for increased risk of adverse events such as hot flush, thromboembolism, and endometrial or breast cancer should be considered.

MANAGEMENT: Caution is advised when ospemifene is used with potent CYP450 3A4 inhibitors. Patients should be advised to seek medical attention if they develop potential signs and symptoms of thromboembolism such as chest pain, shortness of breath, and pain or swelling in the arms or legs.