Ambrisentan is a drug indicated for use in the treatment of pulmonary hypertension.the peptide endothelin constricts muscles in blood vessels, increasing blood pressure. ambrisentan, which relaxes those muscles, is an endothelin receptor antagonist, and is selective for the type a endothelin receptor (eta).ambrisentan is indicated for the treatment of pulmonary arterial hypertension (who group 1) in patients with who class ii or iii symptoms to improve exercise capacity and delay clinical worsening.