Drug Interactions between relugolix and Vosevi

GENERALLY AVOID: Coadministration with inhibitors of the P-glycoprotein (P-gp) efflux transporter may increase the plasma concentrations of relugolix, particularly when the inhibitors are given orally. Relugolix is a substrate for intestinal P-gp. In vitro, it is metabolized primarily by CYP450 3A and, to a lesser extent, by CYP450 2C8. When relugolix was coadministered with erythromycin, a combined P-gp and moderate CYP450 3A inhibitor, relugolix peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 6.2-fold. Increased exposure to relugolix may increase the risk and/or severity of adverse effects such as hot flushes; weight gain; decreased sex drive; erectile function difficulties; QT interval prolongation; musculoskeletal pain; constipation; diarrhea; increases in glucose, triglyceride, and liver transaminase levels; and decreased hemoglobin. No clinically significant differences in the pharmacokinetics of relugolix were observed when coadministered with voriconazole, a strong CYP450 3A inhibitor that does not inhibit P-gp.

MANAGEMENT: Concomitant use of relugolix with orally administered P-gp inhibitors should generally be avoided. If coadministration is required, the manufacturer recommends taking relugolix first and separating the dosing by at least 6 hours. Patients should be monitored more frequently for adverse effects. Alternatively, when relugolix is used as monotherapy for the treatment of prostate cancer, the prescribing information states that treatment with relugolix may be interrupted for up to two weeks if a short course of treatment with a P-gp inhibitor is necessary. Following interruption of relugolix for more than 7 days, the manufacturer recommends restarting therapy with a loading dose of 360 mg on the first day, then continuing with a dose of 120 mg once daily.

MONITOR: Coadministration with inhibitors of organic anion transporting polypeptides (OATP) 1B1 and/or 1B3 may increase the plasma concentrations of voxilaprevir, which is a substrate of the hepatic uptake transporters. When a single 100 mg dose of voxilaprevir was administered with a single 600 mg dose of the potent OATP 1B1/1B3 inhibitor cyclosporine (n=24), mean voxilaprevir peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 19.0- and 9.4-fold, respectively. Inhibition of P-glycoprotein (P-gp)- and breast cancer resistance protein (BCRP)-mediated intestinal transport and CYP450 3A4-mediated metabolism of voxilaprevir may also contribute to the overall interaction with cyclosporine. The safety of such high levels of voxilaprevir has not been established.

MANAGEMENT: Caution and monitoring are advised when voxilaprevir is used with OATP 1B1 or 1B3 inhibitors.