Pfizer Inc said the US FDA has approved Revatio (sildenafil citrate) as a treatment for pulmonary arterial hypertension (PAH), a rare, aggressive and life-shortening vascular disease. Sildenafil citrate is the active ingredient in Viagra, Pfizer's erectile dysfunction medication used by more than 26 million men worldwide.

PAH is characterized by dangerously high pressure in the blood vessels that lead from the heart to the lungs. It is estimated to affect approximately 100,000 people worldwide. Symptoms include difficulty breathing, dizziness and fatigue. Left untreated, patients have an average survival time of less than three years from the time of diagnosis.

"Pfizer undertook a six-year clinical development programme in PAH because patients with this devastating disease needed more medical options, and there was evidence that sildenafil could be an effective treatment," said Dr. Joe Feczko, Pfizer's chief medical officer. "Revatio demonstrates our commitment to developing treatments for unmet medical needs, including rare conditions such as PAH, regardless of commercial potential," Dr. Joe Feczko added.

The FDA granted Revatio a priority review. The FDA approval was based on results of a large randomized, double-blind, placebo-controlled study involving 277 patients with PAH. Patients taking Revatio also showed improvements in mean pulmonary artery pressure and other measures of cardiac function.