Fig. 6From: Efficacy of 1, 5, and 20 mg oral sildenafil in the treatment of adults with pulmonary arterial hypertension: a randomized, double-blind study with open-label extensionChanges from baseline in BNP (a) and pro-BNP (b) during double-blind (week 12) and open-label (week 24) phases of the study. All patients received sildenafil 20 mg TID in the open-label phase of the study (weeks 13–24). BNP = B-type natriuretic peptide; TID = 3 times dailyBack to article page