Drug Interaction Report

MONITOR: Coadministration with inhibitors of P-glycoprotein (P-gp), uridine diphosphate glucuronosyltransferase (UGT) 1A1 or 2B7, and/or breast cancer resistance protein (BCRP) may increase the plasma levels and risk of adverse effects of binimetinib. The proposed mechanism involves the reduced metabolic clearance of binimetinib through inhibition of P-gp, UGT 1A1, UGT 2B7, and/or BCRP. The clinical significance of this interaction is unknown as no clinically relevant drug interactions have been demonstrated with binimetinib.

MANAGEMENT: Until further information is available, caution is recommended if binimetinib must be used concomitantly with P-gp, UGT 1A1, UGT 2B7, and/or BCRP inhibitors. Binimetinib should be monitored more closely whenever a P-gp, UGT 1A1, UGT 2B7, and/or BCRP inhibitor is added to or withdrawn from therapy, and the binimetinib dosage adjusted as necessary.

ADJUST DOSE: Coadministration with grapefruit juice may increase the plasma concentration of valbenazine. The mechanism is inhibition of CYP450 3A4-mediated first-metabolism in the gut wall by certain compounds present in grapefruits. The use of valbenazine has been associated with modest prolongation of the QT interval. However, clinically significant QT prolongation may occur in patients taking a strong CYP450 3A4 inhibitor due to increased concentrations of valbenazine and its active metabolite (+)-alfa-dihydrotetrabenazine. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). The extent of drug-induced QT prolongation is dependent on the particular drugs involved and dosages of the drugs.

MANAGEMENT: Pharmacologic response to valbenazine should be monitored more closely whenever a strong inhibitor of CYP450 3A4 is added to or withdrawn from therapy. Assessment of baseline QT interval and periodic monitoring during therapy may be considered. The manufacturer recommends reducing the dose of valbenazine to 40 mg once daily during concomitant administration with strong CYP450 3A4 inhibitors. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope. In addition, patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.