Decreased absorption of ketoconazole, itraconazole. Decreased serum levels of atazanavir, nelfinavir. Increased plasma conc of CYP2C19-metabolised drugs eg, diazepam, citalopram, imipramine, clomipramine, phenytoin. Decreased clearance of diazepam. Increased trough plasma levels of phenytoin. Increased voriconazole Cmax
& AUC. Increased AUC & prolonged t½
of cisapride. Doubled exposure by CYP3A4 inhibitors eg, clarithromycin. Monitor w/ warfarin or other coumarin derivatives.