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.

ADJUST DOSING INTERVAL: Coadministration with food increases the oral bioavailability of etravirine. The mechanism is unknown. Compared to administration following a meal, the systemic exposure (AUC) to etravirine was decreased by about 50% when the drug was administered under fasting conditions. The types of meal studied (ranging from 345 kilocalories containing 17 grams fat to 1160 kilocalories containing 70 grams fat) did not appear to make a difference with respect to impact on etravirine bioavailability.

MANAGEMENT: Etravirine should always be administered following a meal.

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.