Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or P-glycoprotein (P-gp) may increase the plasma concentrations of apixaban, which is a substrate of both the isoenzyme and efflux transporter. When apixaban was coadministered with the moderate CYP450 3A4 and P-gp inhibitor diltiazem (360 mg once a day), mean apixaban peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 1.3- and 1.4-fold, respectively. Likewise, coadministration with the P-gp inhibitor naproxen (500 mg single dose) increased the mean apixaban Cmax and AUC by approximately 1.6- and 1.5-fold, respectively.

MANAGEMENT: No dosage adjustment for apixaban is required during concomitant therapy with lone inhibitors of CYP450 3A4 or P-gp, or moderate or weak dual inhibitors of both CYP450 3A4 and P-gp. However, caution may be advisable. Closer monitoring of the pharmacologic effects of apixaban may be appropriate whenever a CYP450 3A4 or P-gp inhibitor is added to or withdrawn from therapy. 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).

GENERALLY AVOID: Grapefruit juice may significantly increase the plasma concentrations of midostaurin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Ketoconazole, a potent CYP450 3A4 inhibitor, has been shown to increase midostaurin systemic exposure (AUC) by greater than 10-fold in healthy volunteers. Increased exposure to midostaurin may increase the risk of adverse effects such as nausea, vomiting, diarrhea, edema, hyperglycemia, hyperuricemia, QT prolongation, neutropenia, lymphopenia, thrombocytopenia, and anemia.

ADJUST DOSING INTERVAL: Food enhances the oral bioavailability of midostaurin. Relative to fasting conditions, midostaurin systemic exposure (AUC) increased by approximately 1.2-fold when administered with a standard meal (457 calories; 50 g fat, 21 g proteins, 18 g carbohydrates) and 1.6-fold when administered with a high-fat meal (1007 calories; 66 g fat, 32 g proteins, 64 g carbohydrates), while midostaurin peak plasma concentration (Cmax ) decreased by 20% and 27%, respectively.

MANAGEMENT: The manufacturer recommends taking midostaurin with food. Midostaurin was administered with food in clinical trials. Patients should avoid consumption of grapefruit and grapefruit juice during treatment with midostaurin.