NPPB and pulmonary arterial hypertension: Retrospective analysis of the ARIES-1 and -2 trials,30 which were randomized placebo-controlled clinical studies testing the therapeutic effect of ambrisentan over 12 weeks in PAH yielded results in support of this proof-of-concept.31 Among participants randomized to ambrisentan 10 mg/d, patients using spironolactone (N=21) as part of their standard of care medical regimen had a trend toward improved 6-MWD by 94% at week 12, improved plasma BNP concentration by 1.7-fold, and improved WHO FC status compared to patients not taking spironolactone (N=10).