Drug Interaction Report

ADJUST DOSE: Coadministration with inhibitors of P-glycoprotein (P-gp) may increase the plasma concentrations of edoxaban, which is a substrate of the efflux transporter. In healthy volunteers, single-dose edoxaban systemic exposure (AUC) increased approximately 80% to 90% by erythromycin, dronedarone, and ketoconazole; 70% to 80% by cyclosporine and quinidine; 50% by verapamil; and 40% by amiodarone. The peak plasma concentration (Cmax) of edoxaban also increased by approximately 45% to 90% with these drugs.

MANAGEMENT: When used for the treatment of deep vein thrombosis and pulmonary embolism, the manufacturer recommends that edoxaban dosage be reduced to 30 mg once daily in patients receiving concomitant treatment with certain P-gp inhibitors including azithromycin, clarithromycin, erythromycin, oral itraconazole, oral ketoconazole, quinidine, and verapamil. This dosage recommendation is based on data from a clinical study, the Hokusai VTE study, and is limited to use with the specific P-gp inhibitors mentioned. Other P-gp inhibitors were not permitted in the study, and patients on antiretroviral therapy (ritonavir, nelfinavir, indinavir, saquinavir) as well as cyclosporine were excluded from the study. Following discontinuation of the P-gp inhibitor, edoxaban dosage should be returned to the regular dosage of 60 mg once daily. No dosage adjustment is recommended for edoxaban when used in the treatment of nonvalvular atrial fibrillation.

GENERALLY AVOID: Grapefruit and grapefruit juice may significantly increase the plasma concentrations of orally administered ranolazine. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Because ranolazine prolongs QT interval in a dose-dependent manner, high plasma levels of ranolazine may increase the risk of ventricular arrhythmias such as ventricular tachycardia, ventricular fibrillation, and torsade de pointes.

MANAGEMENT: Patients treated with ranolazine should avoid consumption of grapefruit juice and other grapefruit products if possible. Otherwise, the dosage of ranolazine should be limited to 500 mg twice a day.