Pfizer was celebrating yesterday after the US Food and Drug Administration gave the thumbs up to market its top-selling erectile dysfunction drug, Viagra (sildenafil), under the brand name Revatio as a the treatment for pulmonary arterial hypertension.

PAH is a rare, aggressive and life-shortening vascular disease, characterised by dangerously high pressure in the blood vessels that lead from the heart to the lungs, which is thought to affect around 100,000 people worldwide. If left untreated, patients have an average survival time of less than three years from diagnosis.

The Revatio dossier was assessed under priority review status, with final approval granted on the back of a 277-patient clinical trial. The study measured the exercise capability of patients after 12 weeks of treatment with one of three doses of Revatio or placebo. All three treatment groups showed highly significant improvements in the six-minute walk distance – the standard measure of efficacy in PAH trials – versus placebo. Patients taking Revatio also showed improvements in mean pulmonary artery pressure and other measures of cardiac function.

Pfizer says that Revatio is the first oral treatment for PAH to be approved for patients with an early stage of the disease. It is expected to be available from the middle of July as a white, round pill, to distinguish it from the blue diamond-shaped ED pill.

The new approval will likely be a boost for the world’s largest pharmaceutical company, which is jostling for space in the ED market it once dominated thanks to heightened competition from Bayer/GlaxoSmithKline’s Levitra (vardenafil) and Lilly/Icos’ Cialis (tadalafil). And Viagra’s safety came under fire last month after the FDA said the drug could require a label change after its use was linked to a form of blindness [[31/05/05a]].