Drug Interaction Report

GENERALLY AVOID: Coadministration with inducers of the P-glycoprotein (P-gp) efflux transporter and/or the uridine diphosphate glucuronosyltransferase (UGT) enzymes may decrease the plasma concentrations of letermovir according to the product labeling. Because letermovir is a substrate of P-gp and UGT 1A1 and 1A3, induction of the efflux transporter and metabolic enzymes may theoretically increase the clearance of letermovir. Concomitant use of rifampin initially resulted in a clinically insignificant increase in letermovir plasma concentrations (due to inhibition of organic anion transporting polypeptide [OATP] 1B1/3 and/or P-gp), followed by clinically significant decreases in letermovir plasma concentrations with continued rifampin coadministration (due to induction of P-gp/UGT).

MANAGEMENT: Due to the potential loss of efficacy, use of letermovir with inducers of the P-glycoprotein (P-gp) efflux transporter and/or the uridine diphosphate glucuronosyltransferase (UGT) enzymes is not recommended.

Administration with food may delay the absorption of modafinil (the racemate) and armodafinil (the R-enantiomer) without significantly affecting their overall bioavailability. According to the product labeling, modafinil's absorption may be delayed by approximately one hour if taken with food. Similarly, the time to reach peak plasma concentration (Tmax) of armodafinil may be delayed by approximately 2 to 4 hours in the fed state.