Drug Interaction Report

MONITOR: Coadministration with potent inhibitors of CYP450 3A4 or moderate to potent inhibitors of P-glycoprotein (P-gp) or breast cancer resistant protein (BCRP) may increase the plasma concentrations of riociguat, which is partially metabolized by CYP450 3A and also a substrate of the P-gp and BCRP efflux transporters. Increased levels of riociguat may increase the risk for hypotension. When riociguat was administered with ketoconazole, a potent CYP450 3A4 inhibitor that also inhibits P-gp and BCRP, riociguat peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 1.5- and 2.5-fold, respectively. The Cmax and AUC of the active metabolite, M1, which has 1/10th to 1/3rd the pharmacologic activity of riociguat, were reduced by approximately 50% and 25%, respectively. Administration with the potent CYP450 3A4 inhibitor clarithromycin increased the AUC of riociguat by about 30%. The Cmax and AUC of M1 were not significantly altered (i.e., <20% increase).

MANAGEMENT: Caution is advised when riociguat is prescribed with potent CYP450 3A4 inhibitors or moderate to potent P-gp or BCRP inhibitors. Patients should be monitored for signs and symptoms of hypotension, and the dosage of riociguat adjusted if necessary.

ADJUST DOSING INTERVAL: Food significantly enhances the oral bioavailability of telaprevir. When given with a meal containing 533 kcal and 21 g fat, telaprevir systemic exposure (AUC) increased by 237% compared to administration under fasting conditions. The type of meal also affects the exposure to telaprevir. Relative to fasting, telaprevir AUC increased by approximately 117% with a low-fat meal (249 kcal; 3.6 g fat) and 330% with a high-fat meal (928 kcal; 56 g fat). In Phase 3 clinical trials, telaprevir doses were administered within 30 minutes of completing a meal or snack containing approximately 20 grams of fat.

MANAGEMENT: Telaprevir should be administered with food containing approximately 20 grams of fat. Patients should be advised that the fat content of the meal or snack is critical to the absorption of telaprevir. Food taken with telaprevir should be ingested within 30 minutes prior to each dose. Examples of some foods that could be taken with telaprevir include: bagel with cream cheese; half cup of nuts; 3 tablespoons of peanut butter; 1 cup of ice cream; 2 ounces of American or cheddar cheese; 2 ounces of potato chips; or half cup of trail mix.

ADJUST DOSE: Smoking may decrease the plasma concentrations of riociguat. The proposed mechanism is induction of the CYP450 1A1-mediated metabolism of riociguat by polycyclic aromatic hydrocarbons present in cigarette smoke. CYP450 1A1 is responsible for the formation of the major active metabolite, M1, which has just 1/3 to 1/10 the pharmacologic activity of riociguat. According to the product labeling, plasma concentrations of riociguat are reduced by 50% to 60% in smokers compared to nonsmokers.

MANAGEMENT: Patients should be advised to stop smoking. Riociguat dosages higher than 2.5 mg three times a day may be considered in cigarette smokers, if tolerated, to match the exposure seen in nonsmoking patients. However, safety and effectiveness of higher dosages have not been established. A dosage reduction should be considered in patients who stop smoking during treatment with riociguat. The tablet form of riociguat can generally be taken with or without food. Some authorities recommend not to switch between fed and fasted riociguat intake because of increased peak plasma levels of riociguat in the fasting compared to the fed state.