Pharmacologyendothelian receptor antagonist that blocks endothelin receptors on endothelium and vascular smooth muscle (stimulation of these receptors is associated with vasoconstriction). bosentan blocks both eta and etb receptors, with a slightly higher affinity for the a subtype. indicationspulmonary arterial hypertension: treatment of pulmonary artery hypertension (pah) (who group i) in patients with who/nyha class ii, iii, or iv symptoms to improve exercise capacity and decrease the rate of clinical deterioration. note: according to treatment guidelines from the fifth world symposium on pulmonary hypertension (wsph), only a small number of pah patients with who-fc iv symptoms (ie, severely ill patients) were included in clinical trials, therefore, most experts consider bosentan second-line therapy in these patients (wsph [gail
2013]).