Drug Interaction Report

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of macitentan, which is primarily metabolized by the isoenzyme. In ten healthy male subjects pretreated with macitentan (30 mg initially, followed by 10 mg once daily) for 5 days, coadministration with the potent CYP450 3A4 inducer rifampin (600 mg once daily) on days 6 through 12 reduced macitentan systemic exposure (AUC) by 79% and trough plasma concentration (Cmin) by 93% compared to macitentan administered alone. There was no significant effect on the AUC of the active metabolite, which has been reported to be approximately 5-fold less potent than macitentan in vitro, but whose systemic exposure in human is 2.5-fold higher than that of macitentan.

MANAGEMENT: Caution is advised when macitentan is used with CYP450 3A4 inducers. The possibility of diminished therapeutic effects should be considered.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.