Drug Interaction Report

MONITOR: Coadministration with vemurafenib may increase the plasma concentrations and the risk of adverse effects of drugs that are substrates of CYP450 2C8. The proposed mechanism, based on in vitro data, is decreased clearance due to vemurafenib-mediated inhibition of CYP450 2C8.

MANAGEMENT: Caution is advised if vemurafenib is used concomitantly with drugs that are substrates of CYP450 2C8, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring should be considered whenever vemurafenib is added to or withdrawn from therapy with these drugs. Since vemurafenib has a long half-life, a wash-out period of 8 days following the discontinuation of vemurafenib has been suggested to avoid an interaction with subsequent therapy. Patients should be monitored for the development of adverse effects.

GENERALLY AVOID: The combined use of ethanol and isotretinoin may result in a disulfiram-like reaction. The mechanism has not been established.

MANAGEMENT: Alcohol consumption should be avoided during isotretinoin therapy.