Drug Interaction Report

MONITOR: Coadministration with inhibitors of P-glycoprotein (P-gp) may increase the plasma concentrations of mitoxantrone, which is a substrate of the efflux transporter also known as ABCB1 or MDR1. The interaction has been studied with cyclosporine, a potent P-gp inhibitor. In a pharmacokinetic study of 38 children with de novo acute myeloid leukemia, mitoxantrone 6 mg/m2 administered daily in combination with cyclosporine resulted in a 42% decrease in mean mitoxantrone clearance and 12% increase in systemic exposure (AUC) compared to mitoxantrone 10 mg/m2 administered daily without cyclosporine. There were no differences in the rates of stomatitis or infection between the two groups, but an increased incidence of hyperbilirubinemia was observed in the cyclosporine group, which rapidly reversed upon conclusion of treatment. Therefore, it appears a 40% dose reduction of mitoxantrone given with cyclosporine produced statistically similar systemic exposure and toxicity as mitoxantrone given alone.

MANAGEMENT: Caution is advised if mitoxantrone is prescribed in combination with a P-gp inhibitor. Patients should be closely monitored for increased adverse effects including cardiotoxicity and myelosuppression.

ADJUST DOSE: Smoking tobacco may decrease the steady-state systemic exposure of istradefylline by 38% to 54%.

MANAGEMENT: The possibility of reduced therapeutic effects of istradefylline should be considered in smokers. The manufacturer recommends an istradefylline dosage of 40 mg once daily in patients who smoke 20 or more cigarettes (or the equivalent amount of another tobacco product) per day.