TABLE 1.

Pharmacodynamic and pharmacokinetic properties of ET receptor antagonists approved for clinical use

	Bosentan	Macitentan	Active Metabolite of Macitentan	Ambrisentan	Sitaxentan (Withdrawn from Clinical Use in 2010)
Trade name	Tracleer,	Opsumit		Letairis, Volibris	Thelin
Chemical Name	benzenesulfonamide	sulfamide	sulfamide	benzenepropanoic acid	3-thiophenesulfonamide
Inhibition [125I]-ET-1 IC50 (nM, *Ki)
ETA	5*	0.5	3	0.3	1
ETB	97*	391	185	185	9800
ET plasma levels after administration	↑↑	↑↑	—	↑	↓
Bioavailability	∼50%	Not reported	Not reported	High	70–100%
Time to max plasma concentration	3–5	4-12	30	1.7–3.3	1–4
Terminal half-life (h)	5.4	16	40.2-65.6	15	10
Excretion in urine (%)	<3	50%	—	Low	50–60

(Weber et al., 1996;1999; Spence et al., 2008; Opitz et al., 2008; Sidharta et al., 2013)