Ambrisentan is a drug indicated for use in the treatment of pulmonary hypertension. It functions as an endothelin receptor antagonist, and is selective for the type A endothelin receptor (ETA). Once daily oral ambrisentan 2.5 to 10 mg/day significantly improved exercise capacity (6-minute walk distance) compared with placebo in two double-blind, multicenter trials (ARIES-1 & ARIES-2). Ambrisentan was well tolerated with a lower incidence and severity of liver function test abnormalities compared with the ET(A)/ET(B) ERA, bosentan, and the ET(A)-selective ERA, sitaxsentan. Ambrisentan does not induce or inhibit P450 enzymes; therefore, ambrisentan is unlikely to affect the pharmacokinetics of P450-metabolized drugs. The demonstration of clinical efficacy, low incidence of acute hepatic toxicity, and low risk of drug-drug interactions support the role of ambrisentan for the treatment of PAH.
-O189.gif)