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: Consumption of food has led to a 27% decrease in the bioavailability of orally administered tacrolimus.

MANAGEMENT: Tacrolimus should be administered at least one hour before or two hours after meals.

GENERALLY AVOID: Grapefruit juice has been reported to increase tacrolimus trough concentrations. Data are limited, but inhibition of the CYP450 enzyme system appears to be involved.

MANAGEMENT: The clinician may want to recommend that the patient avoid ingesting large amounts of grapefruit juice while taking tacrolimus.

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.