Drug Interaction Report

MONITOR: Coadministration with inhibitors of organic anion transporting polypeptides (OATP) 1B1 and/or 1B3 may increase the plasma concentrations and effects of momelotinib, which is a substrate of the hepatic uptake transporters. Clinical studies have demonstrated that concomitant use with a single dose of the OATP1B1/B3 inhibitor rifampin increased the peak plasma concentration (Cmax) and systemic exposure (AUC) of momelotinib by 40% and 57% respectively. The Cmax and AUC of the active metabolite of momelotinib, M21, was also increased, by 6% and 12%, respectively.

MANAGEMENT: Caution is advised if momelotinib is used in combination with inhibitors of OATP1B1 and/or 1B3. Dosage adjustments of momelotinib may be required. Patients should be advised to report any momelotinib-related adverse reactions such as bacterial or viral infection, thrombocytopenia, neutropenia, hepatotoxicity, thrombosis, and adverse cardiovascular events.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of pazopanib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. Although not studied, the interaction may increase the risk of QT interval prolongation and torsade de pointes arrhythmia as well as severe and fatal hepatotoxicity associated with the use of pazopanib.

ADJUST DOSING INTERVAL: Food increases the oral bioavailability of pazopanib. The mechanism of interaction is unknown. Administration of pazopanib with a high-fat or low-fat meal results in an approximately 2-fold increase in peak plasma concentration (Cmax) and systemic exposure (AUC).

MANAGEMENT: Patients treated with pazopanib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Pazopanib should be administered at least one hour before or two hours after a meal.