Ambrisentan for the management of pulmonary arterial hypertension

BACKGROUND: Approved by the US Food and Drug Administration in 2007, ambrisentan is the second oral endothelin A-receptor antagonist available for the management of pulmonary arterial hypertension (PAH) in patients with World Health Organization class II or III symptoms. OBJECTIVE: This article examines the clinical pharmacology of ambrisentan, its efficacy and adverse effects, and future directions for research. METHODS: Pertinent articles and abstracts were identified through searches of MEDLINE and Current Contents from 1966 to January 15, 2008, using the term ambrisentan. The reference lists of identified articles were searched for additional publications. Abstracts presented at professional meetings from 2005 through 2007 were also reviewed. RESULTS: The literature review identified 3 studies of ambrisentan in PAH: 1 dose-ranging study; 2 randomized, double-blind, placebo-controlled studies; and 1 drug-conversion study. In the dose-ranging study, ambrisentan at doses of 1 to 10 mg was associated with significant improvements from baseline in the 6-minute walk distance at 12 weeks that ranged from 33.9 m with ambrisentan 1 mg (P = 0.003) to 38.1 m with ambrisentan 5 mg (P = 0.001). In the placebo-controlled studies, ambrisentan at doses of 2.5 to 10 mg/d was associated with significant improvements versus placebo in the 6-minute walk distance at 12 weeks that ranged from 22 m with ambrisentan 2.5 mg (P = 0.022) to 59 m with ambrisentan 5 mg (P