Viagra may be famous for helping men in the bedroom, but a new study shows it may also help children with a rare and often fatal lung disease.

Researchers found the active ingredient in Viagra, sildenafil, helped children with pulmonary arterial hypertension (PAH) walk farther and breathe easier when taken over the course of a year.

Pulmonary arterial hypertension occurs when blood pressure in the arteries that supply blood to the lungs becomes dangerously high and causes symptoms including fatigue, dizziness, shortness of breath, and eventually heart failure and death.

"Untreated, children usually die within one year of diagnosis," says researcher Ian Adatia, associate professor of pediatrics at the University of California San Francisco Children's Hospital, in a news release. He says that even with the best available treatment few people live five years after the disease is diagnosed.

But the small, pilot study showed that sildenafil provided significant benefits for children with the lung condition with fewer side effects than existing treatments.

Earlier this month, the FDA approved sildenafil for the treatment of PAH under the brand name Revatio.

Read Web MD's "Viagra May Protect Lungs From Altitude Sickness."

Read Web MD's "Frequently Asked Questions about Hypertension."

Sildenafil Eases Lung Disease

In the study, which appears in the current issue of Circulation: Journal of the American Heart Association, researchers looked at the effects of sildenafil in a group of 14 children with symptomatic pulmonary arterial hypertension.

The children received varying doses of the drug along with other drugs as needed, such as blood thinners. After one year of treatment, the results showed that the children were able to walk farther than typically seen with other drugs used to treat PAH.

For example, the average distance walked in six minutes, a standard measure of PAH severity, increased by 154 meters or more than one and a half football fields.

Researchers say sildenafil appears to help pulmonary hypertension by relaxing the smooth muscle of blood vessels and increasing blood flow. That effect resulted in a 20 percent drop in resistance in the pulmonary arteries and improved breathing for these children.

"Very importantly, the side effects were minimal, the drug was very easy to take, and there were no changes in liver or kidney function that can happen with other drugs [used to treat PAH]," says Adatia.

But researchers stress that this was a very small study and more research is needed to determine the long-term effects of sildenafil in people with the lung disease.

Pfizer, which makes Viagra, funded the study. Pfizer is a WebMD sponsor.

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By Jennifer Warner, reviewed by Charlotte E. Grayson, MD

SOURCES: Humpl, T. Circulation: Journal of the American Heart Association, June 14, 2005; vol 111. News release, American Heart Association. WebMD Medical News: “Viagra Ingredient OK'd for Lung Problem.”