As well as erectile dysfunction, sildenafil citrate is also effective in the rare diseasepulmonary arterial hypertension
(PAH). It relaxes the arterial wall, leading to decreased pulmonary
arterial resistance and pressure. This, in turn, reduces the workload of
the right ventricle of the heart and improves symptoms of right-sided heart failure.
Because PDE5 is primarily distributed within the arterial wall smooth
muscle of the lungs and penis, sildenafil acts selectively in both these
areas without inducing vasodilation in other areas of the body. Pfizer
submitted an additional registration for sildenafil to the United States Food and Drug Administration
(FDA), and sildenafil was approved for this indication in June 2005.
The preparation is named Revatio, to avoid confusion with Viagra, and
the 20 milligram tablets are white and round. Sildenafil joins bosentan and prostacyclin-based therapies for this condition.