Mechanism of Action
Endothelin receptor antagonist (ET); prevents binding of ET-1 to both ET-A and ET-B receptors with high affinity to ET receptors in pulmonary arterial smooth muscle cells; active metabolite 20% as potent as parent compound
Absorption
Peak plasma time: 8 hr
Absolute bioavailability: Unknown
Distribution
Protein bound: >99%; mainly to albumin and to a lesser extent alpha-1-glycoprotein
Vd: 50 L; 40 L (active metabolite)
Metabolism
Metabolized by liver: Mainly by CYP3A4, minor amount by CYP2C19; primarily metabolized by oxidative depropylation of the sulfamide to active metabolite
Active metabolite: At steady state, systemic exposure of active metabolite is 3-times the exposure of macitentan; active metabolite thought to contribute approximately 40% of total pharmacologic activity
Elimination
Half-life: 16 hr; 48 hr (active metabolite)
Excretion: 50% urine; 24% feces