Drug Interaction Report

Coadministration with mild or moderate inhibitors of CYP450 3A4 may modestly increase the plasma concentrations of ruxolitinib, which is primarily metabolized by the isoenzyme. In healthy subjects, administration of a single 10 mg dose of ruxolitinib following pretreatment with the moderate CYP450 3A4 inhibitor erythromycin (500 mg twice daily for four days) resulted in an 8% increase in ruxolitinib peak plasma concentration (Cmax) and a 27% increase in systemic exposure (AUC) compared to administration of ruxolitinib alone. The change in the pharmacodynamic marker, pSTAT3 inhibition, was consistent with the corresponding exposure information. No dosage adjustment is recommended when ruxolitinib is coadministered with mild or moderate CYP450 3A4 inhibitors. However, clinical data for topical ruxolitinib are not available. Consultation with individual package labeling, as well as relevant institutional protocols, may be advisable for further guidance.

GENERALLY AVOID: Grapefruit juice and Seville oranges may increase the plasma concentrations of entrectinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit and Seville oranges Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but pharmacokinetic data are available for the potent CYP450 3A4 inhibitor, itraconazole. When a single 100 mg dose of entrectinib was administered with itraconazole, entrectinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 1.7- and 6-fold, respectively. Coadministration of entrectinib with a moderate CYP450 3A4 inhibitor is predicted to increase entrectinib Cmax and AUC by 2.9- and 3-fold, respectively. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Increased exposure to entrectinib may increase the risk and/or severity of adverse effects such as cognitive impairment, mood disorders, dizziness, sleep disturbances, liver enzyme elevations, hyperuricemia, congestive heart failure, edema, myocarditis, QT prolongation, vision problems, anemia, and neutropenia.

MANAGEMENT: Patients should avoid consumption of grapefruit, grapefruit juice, and Seville oranges during treatment with entrectinib.

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.

The recommended maximum number of medicines in the 'multikinase inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'multikinase inhibitors' category:

• entrectinib
• ruxolitinib

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.