- Patients cannot be receiving enzyme-inducing antiepileptic drugs (EIAEDs; e.g., phenytoin, carbamazepine, phenobarbital) nor any other cytochrome P450, family 3, subfamily A, polypeptide 4 (CYP3A4) inducer such as rifampin or St. John's wort, as these may decrease temsirolimus levels; use of agents that potently inhibit CYP3A (and hence may raise temsirolimus levels), such as ketoconazole, is discouraged, but not specifically prohibited; the appropriateness of use of such agents is left to physician discretion