Drug Interaction Report

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of maribavir, which is primarily metabolized by the isoenzyme. When maribavir (400 mg twice daily) was administered with the potent CYP450 3A4 inducer, rifampin (600 mg once daily), maribavir peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 39% and 60%, respectively. The interaction has not been studied with other, less potent inducers.

MANAGEMENT: The potential for diminished pharmacologic effects of maribavir should be considered during coadministration with CYP450 3A4 inducers. Alternative treatments may be required if an interaction is suspected.

ADJUST DOSING INTERVAL: The tolerability of allopurinol may be improved by giving it after a meal. Additionally, when the dose is greater than 300 mg, dividing the total daily dose into smaller doses administered more often may be appropriate to help minimize gastrointestinal irritation.

MONITOR: Concomitant use of allopurinol with central nervous system (CNS) depressants, including alcohol, may potentiate adverse effects such as somnolence and sedation.

MANAGEMENT: To improve tolerability, some manufacturers suggest administering allopurinol after a meal. Additionally, if the daily dose is greater than 300 mg, administering allopurinol in divided doses may help reduce gastrointestinal intolerance. Patients should also be counseled to avoid or limit consumption of alcohol and to avoid activities requiring mental alertness such as driving or operating hazardous machinery until they know how the medication affects them.