- Current use or anticipated need for treatment with drugs that are known CYP3A4 or cytochrome P450 1A2 (CYP1A2) inducers (ie, carbamazepine, dexamethasone, felbamate, omeprazole, phenobarbital, phenytoin, amobarbital, nevirapine, primidone, rifabutin, rifampin, and St. John's wort)