Drug Interaction Report

ADJUST DOSE: Coadministration with inhibitors of P-glycoprotein (P-gp) may significantly increase the plasma concentrations of betrixaban, which is a substrate of the efflux transporter. When administered with the potent P-gp inhibitor verapamil, betrixaban peak plasma concentration (Cmax) increased by nearly 5-fold and systemic exposure (AUC) increased by approximately 3-fold compared to betrixaban administered alone. When given with ketoconazole, another P-gp inhibitor, betrixaban Cmax and AUC increased by a little more than 2-fold each. In the Acute Medically Ill Prevention with Extended Duration Betrixaban (APEX) Study, use of betrixaban at a 50% dosage reduction in combination with P-gp inhibitors or in the presence of severe renal impairment was associated with increased relative risks of bleeding, including major bleeding, compared to treatment with enoxaparin.

MANAGEMENT: When used with P-gp inhibitors, the recommended dosage of betrixaban is an initial single dose of 80 mg followed by 40 mg once daily. Patients should be routinely evaluated for signs and symptoms suggesting blood loss such as a drop in hemoglobin and/or hematocrit, hypotension, or fetal distress (in pregnant women). Concomitant use of betrixaban with P-gp inhibitors should be avoided in patients with severe renal impairment (CrCl<30 mL/min).

ADJUST DOSING INTERVAL: Food reduces the oral bioavailability of betrixaban. When administered with a low-fat (900 calories; 20% fat) or high-fat (900 calories; 60% fat) meal, betrixaban peak plasma concentration (Cmax) and systemic exposure (AUC) decreased relative to administration in the fasting state by an average of 70% and 61%, respectively, with the low-fat meal and 50% and 48%, respectively, with the high-fat meal. The effect of food on betrixaban pharmacokinetics could be observed for up to 6 hours after meal intake.

MANAGEMENT: The manufacturer recommends taking betrixaban at the same time each day with food.

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.