- Patients must not be receiving any of the following potent cytochrome P450, family 3, subfamily A, polypeptide 4 (CYP3A4) inducers or inhibitors: erythromycin, clarithromycin, azithromycin, ketoconazole, itraconazole, voriconazole, posaconazole, grapefruit juice or St. John's wort