Interactions between propecia(finasteride) and Fluconazole (fluconazole)
fluconazole and finasteride (Moderate Drug-Drug)
MONITOR: Coadministration with fluconazole may increase the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme. The mechanism is decreased clearance due to inhibition of CYP450 3A4 activity by fluconazole. A case of carbamazepine (a CYP450 3A4 substrate) toxicity secondary to significantly increased serum drug concentrations was reported in a patient shortly after the addition of fluconazole. Other drugs metabolized by CYP450 3A4 whose plasma levels reportedly are increased by fluconazole include oral contraceptives (ethinyl estradiol and levonorgestrel), cyclosporine, tacrolimus, and cisapride. These interactions have usually been observed with higher dosages of fluconazole (200 mg/day or more).
MANAGEMENT: Caution is advised if fluconazole must be used concurrently with medications that undergo metabolism by CYP450 3A4, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever fluconazole is added to or withdrawn from therapy.
