Drug Interaction Report

Coadministration with inducers of CYP450 3A4 and/or P-glycoprotein may decrease the plasma concentrations of mirabegron, which has been shown in vitro to be a substrate of the isoenzyme and efflux transporter. However, in vivo results indicate that these pathways may play a limited role in the overall elimination. In healthy study subjects, mirabegron peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by less than 50% when a single 100 mg dose of mirabegron was administered following multiple dosing of rifampin 600 mg once daily. No dosage adjustment is recommended when mirabegron is administered in combination with rifampin and probably other CYP450 3A4/P-gp inducers.

ADJUST DOSING INTERVAL: Administration with food increases the plasma concentrations of efavirenz and may increase the frequency of adverse reactions. According to the product labeling, administration of efavirenz capsules (600 mg single dose) with a high-fat/high-caloric meal (894 kcal, 54 g fat, 54% calories from fat) or a reduced-fat/normal-caloric meal (440 kcal, 2 g fat, 4% calories from fat) was associated with mean increases of 39% and 51% in efavirenz peak plasma concentration (Cmax) and 22% and 17% in systemic exposure (AUC), respectively, compared to administration under fasted conditions. For efavirenz tablets, administration of a single 600 mg dose with a high-fat/high-caloric meal (approximately 1000 kcal, 500-600 kcal from fat) resulted in a 79% increase in mean Cmax and a 28% increase in mean AUC of efavirenz relative to administration under fasted conditions.

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of efavirenz. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

MANAGEMENT: Efavirenz should be taken on an empty stomach, preferably at bedtime. Dosing at bedtime may improve the tolerability of nervous system symptoms such as dizziness, insomnia, impaired concentration, somnolence, abnormal dreams and hallucinations, although they often resolve on their own after the first 2 to 4 weeks of therapy . Patients should be advised of the potential for additive central nervous system effects when efavirenz is used concomitantly with alcohol or psychoactive drugs, and to avoid driving or operating hazardous machinery until they know how the medication affects them.

Food reduces the oral absorption and bioavailability of mirabegron. According to the product labeling, administration of a 50 mg tablet with a high-fat meal decreased mirabegron peak plasma concentration (Cmax) and systemic exposure (AUC) by 45% and 17%, respectively, whereas administration with a low-fat meal decreased mirabegron Cmax and AUC by 75% and 51%, respectively. In phase 3 clinical studies demonstrating both safety and efficacy, mirabegron was administered without regards to food content and intake. Therefore, mirabegron can be taken with or without food at the recommended dosage.