Interactions between cialis(tadalafil) and Amprenavir (amprenavir)
amprenavir and tadalafil (Moderate Drug-Drug)
ADJUST DOSE: Coadministration with drugs that are potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of tadalafil, which is primarily metabolized by the isoenzyme. According to the product labeling for tadalafil, ketoconazole (400 mg daily), a selective and potent inhibitor of CYP450 3A4, increased the peak plasma concentration (Cmax) and systemic exposure (AUC) of a single 20 mg dose of tadalafil by 22% and 312%, respectively, compared to administration of tadalafil alone. Ketoconazole (200 mg daily) increased the Cmax and AUC of a single 10 mg dose of tadalafil by 15% and 107%, respectively. Ritonavir (200 mg twice a day), another potent inhibitor of CYP450 3A4, increased the AUC of a single 20 mg dose of tadalafil by 124% with no change in Cmax.
MANAGEMENT: Tadalafil labeling recommends that the dosage not exceed 10 mg once every 72 hours or 2.5 mg once daily in patients treated concomitantly with a potent CYP450 3A4 inhibitor, such as erythromycin, itraconazole, ketoconazole, protease inhibitors, and nefazodone. Patients should be advised to promptly notify their physician if they experience pain or tightness in the chest or jaw, irregular heartbeat, nausea, shortness of breath, visual disturbances, syncope, or prolonged erection (greater than 4 hours).
