Viagra Found to Help High-Altitude Athletes

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% 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 whether 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 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.

Early studies showed some promise. In 2004, a study of mountaineers at Mt. Everest Base Camp, elevation 17,600 feet, showed that Viagra increased the heart’s maximum workload.

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 -- which research dubbed the drug responders -- had significant improvements in their times with the 50-milligram dose. Their average time was 10 minutes, 48 seconds, compared to 15 minutes when they took a placebo.

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.

The researchers are uncertain why only four of the riders responded to Viagra, but they noticed that they were the ones whose times suffered most at high altitude when they took only a placebo. Viagra merely allowed them to make up the performance they lost.

Friedlander said the side effects of Viagra at high altitude still need more study. None of the cyclists reported an erection during the trials, she said.

Scientists do not understand why some people are more susceptible to the effects of altitude.

Any decision to ban Viagra from competition might consider whether this susceptibility could be considered a handicap.

“We want a level playing field,” said Dr. Gary Wadler, a New York University internist who serves on the World Anti-Doping Agency committee that maintains the list of restricted substances. “If somebody has an illness or disability, you can use a [drug] to level the field.”

Wadler added that because the performance-enhancing effect of Viagra is not seen at sea level -- and has never been tested at the moderate altitudes -- sports regulators have never seriously considered banning the drug.

Scientists said more studies were needed to find the elevation where the benefit disappeared.

Pfizer currently has no plans to pursue Viagra as a high-altitude drug, said Francisco Gebauer, a company spokesman.

Military researchers, though, might begin testing Viagra’s effects on about a dozen soldiers at a military laboratory on Colorado’s Pikes Peak, elevation 14,110, later this summer, said Charles Fulco, a research physiologist and high-altitude expert at the U.S. Army Research Institute of Environmental Medicine in Natick, Mass.

“If we send a group of guys into the mountains of Afghanistan, they need to be able to deal with the altitude,” Fulco said.