By JERE LONGMAN


SCRANTON, Pennsylvania - When George Downey volunteered along with other lacrosse players at Marywood University here to take Viagra for a study, he received a snickering nickname from his high school coach. Inquiring minds sent messages to his Facebook page.

“They’re making fun of me,”Mr.Downey, 19, said good-naturedly.“Deep down, I think they’re looking for tips.”

Except that the Marywood study does not involve the bedroom, but the playing field. It is being financed by the World Anti-Doping Agency, which is investigating whether the diamond-shaped blue pills create an unfair competitive advantage in dilating an athlete’s blood vessels and unduly increasing oxygencarrying capacity. If so, the agency will consider banning the drug.

Viagra, or sildenafil citrate, was devised to treat pulmonary hypertension, or high blood pressure in arteries of the lungs. The drug works by suppressing an enzyme that controls blood flow, allowing the vessels to relax and widen. The same mechanism facilitates blood flow into the penis of impotent men. In the case of athletes, increased cardiac output and more efficient transport of oxygenated fuel to the muscles can enhance endurance.

“Basically, it allows you to compete with a sea level, or near-sea level, aerobic capacity at altitude,” Kenneth W.Rundell, the director of the Human Performance Laboratory at Marywood, said of Viagra.

Some experts are more skeptical. Anthony Butch, the director of the Olympic drug-testing lab at the University of California, Los Angeles, said it would be “extremely difficult, if not impossible” to prove that Viagra provided a competitive edge, given that the differences in performance would be slight. But some athletes do not need proof - only a belief - that a drug works before using it, Dr.Butch said.

“I think it’s going to be a problem,”he said.

A study conducted at Stanford University in California and published in 2006 in The Journal of Applied Physiology indicated that some participants taking Viagra improved their performances by nearly 40 percent in 10-kilometer cycling time trials conducted at a simulated altitude of 3,870 meters - a height far above general elite athletic competition. Viagra did not significantly enhance performance at sea level, where blood vessels are fully dilated in healthy athletes.

Last May, the cyclist Andrea Moletta was removed from the Tour of Italy after a search of his father’s car turned up 82 Viagra pills, as well as syringes concealed in a tube of toothpaste, according to news accounts. An investigation ended without formal accusations of doping.

The World Anti-Doping Agency , based in Montreal, is financing two studies related to Viagra and performance enhancement in sports.

The study at Marywood University is measuring the potential effects of Viagra as an antidote to air pollution. Studies involving animals, and children in Mexico City, have indicated that pollution causes pulmonary hypertension. If that could be alleviated for athletes by Viagra,“performance is going to be enhanced,”said Dr.Rundell, the lead researcher of the pollution study.

The earliest that the World Anti-Doping Agency could place Viagra on its list of prohibited substances would be September 2009, five months before the 2010 Winter Olympics in Vancouver, British Columbia, a spokesman said.

“My guess is, it’s a pretty easy decision to make,”Dr.Rundell said.“It clearly provides an unfair advantage, at least at altitude.”