Viagra, the drug used to treat erectile dysfunction, has been shown to be effective in treating the symptoms of a rare lung disease.
According to research published in the New England Journal of Medicine yesterday, sildenafil citrate, the active ingredient of Viagra, improved the exercise capacity of patients with pulmonary arterial hypertension.
The manufacturer Pfizer has renamed the drug Revatio for use in patients with the lung disease.
A rare and ultimately fatal disorder, pulmonary hypertension affects blood vessels in the lungs. Pressure in the pulmonary artery rises above normal, causing the walls of the arteries in the lungs to tighten and thicken.
Symptoms include fatigue, breathlessness and dizziness.
It is most likely to affect women aged between 20 and 40. The incidence of pulmonary hypertension is about 40 per million.
The study of 278 patients with the disease showed Revatio significantly improved both exercise capacity and illness severity.
Patients in the trial showed a 50m improvement in walking distance, as well as a drop in pulmonary arterial pressure.
Improvements were maintained to the end of the year-long study.
Dr Seán Gaine, director of the pulmonary hypertension unit at the Mater hospital, said that as well as acting as a blood vessel dilator, Revatio helps prevent a thickening in the walls of the arteries in the lungs.
Confirming that more than 40 of his pulmonary hypertension patients were taking sildenafil citrate, Dr Gaine said: "It has made a dramatic difference.
"People have experienced an improvement in exercise tolerance and there is emerging evidence that survival is improved with the long-term use of the drug."