- Current use or anticipated need for treatment with drugs that are known CYP3A4 or cytochrome P450, family 1, subfamily A, polypeptide 2 (CYP1A2) inducers (i.e., carbamazepine, dexamethasone, felbamate, omeprazole, phenobarbital, phenytoin, amobarbital, nevirapine, primidone, rifabutin, rifampin, and St. John's wort)