- Palbociclib is a substrate of CYP3A. Caution should be exercised when dosing Palbociclib concurrently with CYP3A inducers or inhibitors. Furthermore, patients who are taking concurrent medications that are strong inducers/inhibitors or substrates of CYP3A4 should be switched to alternative medications to minimize any potential risk. A list of CYP3A4 substrates, inducers and/or inhibitors is provided in Appendix B. The following medications with strong potential for interaction are not allowed: indinavir nelfinavir ritonavir clarithromycin itraconazole ketoconazole nefazodone saquinavir telithromycin carbamazepine phenobarbital phenytoin pioglitazone rifabutin rifampin St. John's wort Troglitazone