Tadalafil: in pulmonary arterial hypertension

Tadalafil is a selective cyclic guanosine monophosphate-specific phosphodiesterase type 5 inhibitor that is effective in improving exercise ability, the time to clinical worsening and health-related quality of life (HR-QOL) scores in patients with pulmonary arterial hypertension (PAH). In a large, 16-week, randomized, double-blind, placebo-controlled, multicentre, phase III trial (PHIRST) in patients aged >or=14 years with PAH (WHO group I), tadalafil 40 mg once daily (the recommended dosage) significantly increased the mean placebo-corrected 6-minute walk distance (6MWD) by 33 m from baseline (primary endpoint). In treatment-naive patients, tadalafil 40 mg once daily significantly increased the mean placebo-corrected 6MWD by 44 m at week 16, whereas in patients receiving bosentan 125 mg twice daily as background therapy there was a mean change of 23 m, which was not significant. Both the time to the first occurrence of clinical worsening and the incidence of clinical worsening were significantly reduced in recipients of tadalafil 40 mg once daily compared with recipients of placebo. Furthermore, at week 16, tadalafil improved most HR-QOL outcomes from baseline to a significantly greater extent than placebo. Preliminary data from an extension of the PHIRST trial suggest that the improvements in 6MWD are maintained for up to 1 year in recipients of tadalafil 20 or 40 mg once daily. Treatment with tadalafil was generally well tolerated, with adverse events that were transient in nature and of mild to moderate intensity.