Viagra may boost high-altitude effort

Scientists have found a performance-enhancing drug that could be exploited by endurance athletes at high altitudes and soldiers in the mountains of Afghanistan: Viagra.

One group of research subjects – riding stationary bicycles and breathing through masks to simulate the low-oxygen conditions found at 12,700 feet – improved its times for six kilometers by an average of 39 percent after taking the erectile dysfunction drug, researchers at Stanford University and the Veterans Affairs Palo Alto Health Care System reported Thursday.

Military researchers are considering a study to see if Viagra could help soldiers function better at high altitudes.

“It provides a pretty clear advantage to some people,” said Anne Friedlander, senior author of the study, which appears in the current issue of the Journal of Applied Physiology.

Originally conceived as a potential treatment for high blood pressure, Viagra, whose chemical name is sildenafil, causes blood vessels in the penis and lungs to relax. It won federal approval in 1998 as the first erectile dysfunction pill, becoming an instant blockbuster for drug maker Pfizer Inc.

Last year, the company won approval for Viagra, under the new name Revatio, to treat pulmonary hypertension, or high fluid pressure in the lungs.

Altitude researchers saw the potential of the drug because pulmonary hypertension is also an effect of exercise in oxygen-poor environments. As blood vessels constrict in the lungs, the heart has to work harder to pump blood through the body.

The latest study, conducted in the controlled environment of a laboratory, measured the performance of 10 trained cyclists.

Over a period of weeks, each cyclist was tested three times on a stationary bike at a simulated altitude of 12,700 feet. The test involved a six-kilometer ride against the clock. Each subject was tested with a placebo, a 50-milligram dose of Viagra and a 100-milligram dose.

Four of the subjects had significant improvements in their times with the 50-milligram dose. The larger dose of Viagra did not increase the benefit.

The researchers found that the other six riders saw no benefit from the drug.

All the cyclists completed a similar set of tests at sea level. There, Viagra did not lead to any improvement.