Feb. 1, 2005 -- A new use for Viagra may be in the works. The erectile dysfunction drug may help protect against lung problems resulting from high altitudes, say French researchers.
High altitude can sometimes cause illness, especially in people with existing heart and lung problems. The thinner air or lack of oxygen at higher altitudes can cause blood vessels to constrict. When this occurs within the lungs, the constriction of blood vessels can put more force on the heart, leading to life-threatening heart failure. The higher altitude can cause blood vessels in the lung to leak fluid and build up in the lung, interfering with oxygen exchange.
Viagra works by relaxing blood vessels, allowing more blood to flow freely through vessels. The researchers used this drug to block the effects of high altitude on blood vessels on the lung. They looked at whether the use of Viagra would help the lungs continue to get oxygen while ascending to higher altitudes.
In a recent experiment, Viagra was better than a placebo at protecting men's lungs. The results appear in the February issue of the American Journal of Respiratory and Critical Care Medicine.
This was no ordinary lab test. Instead, 12 men perched on a French mountain about 2.7 miles (4,350 meters) above sea level, pushing their lungs to the limits in the name of science.
The participants were normal, healthy men around 29 years old. They weren't mountaineers. None was used to high altitudes. The closest any of them had gotten to Mount Everest was probably seeing it in a photo.
But they were in for an adventure when they enrolled in the study.
High-Altitude Tests
Jean-Paul Richalet, MD, PhD, and colleagues wanted to see if Viagra (sildenafil) helped stop dangerous high-altitude health conditions.
High-altitude pulmonary edema (HAPE) occurs when high altitude and low air pressure causes fluid to leak from blood vessels and builds up in the lungs. HAPE has a mortality rate of 44% if untreated, say the researchers. It's triggered by intense physical exertion at high altitudes that people aren't accustomed to.
The study started at sea level, where the men had baseline measurements taken. Then they left their normal lives behind for the mountains.
First stop: Chamonix. The French mountain town is located about 0.6 miles (1,035 meters) above sea level in the Alps, near the Swiss border. The men spent a day there to start adjusting to altitude. The next day, they strapped into a helicopter and soared almost 10,000 feet (3,000 meters) higher to Observatoire Vallot, located just below the summit of Mont Blanc, the highest point in Western Europe.
For five days, they stayed in the mountain observatory. Afterwards, they came back down the mountain for follow-up tests.
While on the mountain, the men filled out surveys checking for signs of acute mountain sickness three times a day. Their breathing was also monitored at rest. In addition, they rode stationary bikes until they couldn't pedal any more, exercising until exhaustion on their second and fifth days on the mountain.
Half of the men received Viagra. The rest were given a placebo. The Viagra group took 40 milligrams of the drug three times a day, starting on their first day on the mountain.
At first, both groups struggled to adjust. "Subjects suffered from acute mountain sickness until day four," say the researchers.
High altitudes caused a host of problems. Their blood pressure rose 29% higher than at sea level. Dizziness and stomach problems were similar in both groups.
After one or two days, the Viagra group's blood pressure started to normalize. By the sixth day, it was 6% lower than before the experiment. But for the placebo group, it remained high, leveling off about 21% higher than normal.
As expected, high altitude made breathing rougher for all of the men. But the Viagra group had less of a setback at rest and during exercise than the placebo group. Side effects were minor, such as muscle pain, say the researchers.
More studies should be done to see if Viagra can replace the current treatment (calcium-channel blockers or steroids) to treat HAPE, say Richalet and colleagues.