May inhibit metabolism & elevate serum levels of drugs metabolized by CYP3A isozyme eg, alprazolam, astemizole, carbamazepine, cilostazol, cisapride, cyclosporine, disopyramide, ergot alkaloids, lovastatin, methylprednisolone, midazolam, omeprazole, oral anticoagulants (eg, warfarin), pimozide, quinidine, rifabutin, sildenafil, simvastatin, tacrolimus, terfenadine, triazolam, vinblastine; other isozymes of CYP450 eg, phenytoin, theophylline, valproate.