Ambrisentan for the treatment of pulmonary arterial hypertension: improving outcomes

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature that is associated with severe functional impairment and a poor prognosis. Ambrisentan is a selective endothelin type A receptor antagonist approved for the treatment of patients with PAH World Health Organization group 1. The efficacy and safety of ambrisentan has been evaluated in the ARIES series (Ambrisentan for the Treatment of Pulmonary Arterial Hypertension, Randomized, Double-Blind, Placebo-Controlled, Multicenter, Efficacy Studies), which has established its use as both monotherapy or in conjunction with other PAH therapies. Specifically, ambrisentan is effective at increasing exercise tolerance, decreasing the risk of functional class deterioration, and prolonging time to clinical worsening. Further, ambrisentan has a favorable effect on mortality, with an 88% patient survival rate after two years of therapy compared with a 61% survival rate as estimated by the National Institute of Health Registry. Ambrisentan is generally well tolerated in all patient groups, with the main side effects of peripheral edema, sinusitis, flushing, and nasal congestion considered to be mild to moderate in nature. Ambrisentan has several favorable qualities that potentially make it more acceptable to patients, including once-daily administration, limited adverse drug reactions and drug-drug interactions, and minimal risk of liver enzyme elevation. Because of the potential risk of teratogenicity associated with ambrisentan, it is only available through a limited distribution program, ie, LEAP (the Letairis Education and Access Program). Ongoing clinical trials will help to clarify the role of ambrisentan in the treatment of PAH.