Drug Interaction Report

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of ruxolitinib, which is primarily metabolized by the isoenzyme. In healthy subjects, administration of a single 50 mg dose of ruxolitinib following pretreatment with the potent CYP450 3A4 inducer rifampin (600 mg once daily for ten days) resulted in a 32% decrease in ruxolitinib peak plasma concentration (Cmax) and a 61% decrease in systemic exposure (AUC) compared to administration of ruxolitinib alone. In addition, the relative exposure to ruxolitinib's active metabolites increased approximately 100%. This increase may partially explain the reported disproportionate 10% reduction in the pharmacodynamic marker, pSTAT3 inhibition.

MANAGEMENT: No dosage adjustment is recommended when ruxolitinib is coadministered with a CYP450 3A4 inducer. However, patients should be closely monitored and the dose titrated based on safety and efficacy.

MONITOR: Isolated case reports have suggested that the ingestion of alcohol during griseofulvin therapy may rarely cause disulfiram-like reactions, flushing, tachycardia, or increased effects of alcohol. The mechanism is unknown.

MANAGEMENT: Patients should be advised of the possibility of increased adverse effects or a disulfiram-like reaction.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of ruxolitinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

MANAGEMENT: Patients treated with ruxolitinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Ruxolitinib may be administered with or without food.