The Combination Ambrisentan Plus Spironolactone in Pulmonary Arterial Hypertension Study

A prospective, double blind, placebo-controlled clinical study involving 30 patients with World Health Organization (WHO) Group 1 pulmonary arterial hypertension being treated with ambrisentan randomized to receive placebo or spironolactone (50 mg/d) for 90 days using a cross-over trial design. Eligible participants will be randomized to receive placebo or spironolactone (50 mg/d) for 90 days (Phase I). At the completion of Phase I, participants will undergo repeat end-point assessment followed by a 21-day drug washout period. Then, the 90 day crossover phase of the trial will occur (Phase II), in which participants randomized to placebo in Phase I will be treated with spironolactone (50 mg/d) in Phase II and vice versa. At the conclusion of Phase II, end-point measures are reassessed. Spironolactone is a diuretic used in treatment of PAH patients. Spironolactone is usually added to medical treatment when doses of Lasix/Torsemide are increased and patients are at risk for hypokalemia. Study procedures being done for this research study are the standard procedures performed on all PAH patients when they are in clinic for follow-up except for the Cardiopulmonary Exercise Test (CPET) with Innocor.