Drug Interactions between atazanavir / cobicistat and encorafenib

Using encorafenib together with atazanavir may alter the blood levels and effects of both medications. Specifically, the blood levels of encorafenib may increase. This may increase the risk of serious side effects such as bleeding complications, eye and vision problems, liver problems, irregular heart rhythm, and development of new skin cancers. At the same time, encorafenib may cause the blood levels of atazanavir to decrease which may make atazanavir less effective. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

CONTRAINDICATED: Coadministration of cobicistat with a drug that is both a substrate as well as a potent inducer of CYP450 3A4 may result in significantly decreased plasma concentrations of cobicistat and significantly increased concentrations of the other drug. Cobicistat is a substrate and a potent inhibitor of CYP450 3A4. In a study of 12 healthy volunteers, coadministration of the potent CYP450 3A4 inducer carbamazepine (200 mg twice daily) with cobicistat-elvitegravir (150 mg-150 mg once a day) reduced the cobicistat systemic exposure (AUC) and peak plasma concentration (Cmax) by 84% and 72%, respectively, and the elvitegravir AUC and Cmax by 69% and 45%, respectively. In addition, the AUC and Cmax of carbamazepine increased by 43% and 40%, respectively, due to inhibition of the CYP450 3A4-mediated metabolism by cobicistat.

MANAGEMENT: Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic drug levels along with the risk of serious and/or life-threatening adverse effects associated with elevated plasma levels, the concomitant use of antiretroviral regimens containing cobicistat with potent CYP450 3A4 inducers that are also sensitive CYP450 3A4 substrates is considered contraindicated.