MONDAY, Aug. 26, 2002 (HealthDayNews) -- Animal studies show Viagra could shield your heart against damage.
The drug, renowned for its ability to correct erectile dysfunction, causes the release of substances that precondition and protect cardiac muscle, says a report from Dr. Rakesh C. Kukreja, a professor of internal medicine at Virginia Commonwealth University.
"Our studies show that Viagra given to rabbits prior to experimental heart block causes a significant reduction in damage to heart tissue," Kukreja says.
Kukreja and his colleagues have been working on this preconditioning for more than a decade. The idea is that depriving the heart of blood flow for very brief periods can prepare the heart for something more serious. Kukreja cites studies showing that people who experience angina -- heart pain -- before a heart attack have a lower risk of death and fewer complications than those who do not.
While Viagra produces a preconditioning effect by reducing blood flow, its possible use as a way of protecting the heart is a daring concept. Because the drug has been linked to drastic drops in blood pressure and heart attacks in men who were also taking nitroglycerin for a cardiovascular condition, the U.S. Food and Drug Administration requires prescription labels to warn against its use by men with heart conditions.
"We are not challenging that existing warning," Kukreja says, adding that much more animal work is needed before human trials can even be contemplated.
A report in the September issue of the American Journal of Physiology -- Heart and Circulatory Physiology describes how rabbits were given Viagra, either orally or by injection, and then were subjected to heart damage. A reduction in damage was observed within 30 minutes, and the effect lasted for almost 24 hours, the report says.
"Definitely more animal work should be done," Kukreja says, not only to study the effect in more detail but also to determine the most effective dose of Viagra. "Some of our studies seem to suggest that the drug provides protection at a much lower dose than needed to treat impotence," he says.
Kukreja says he has begun those studies, estimating it may take two to three years to produce the kind of evidence needed to warrant human trials.
The idea of preconditioning "has been around for a while," says Dr. George Vetrovec, chairman of cardiology at the Virginia Commonwealth University School of Medicine. Some animal studies indicate the effect could last as long as several weeks, he adds.
Viagra is just one of a number of agents that have been tested for their preconditioning effect, Vetrovec says, and although it has "a potent preconditioning effect" it might not be the drug that would eventually be used if and when the idea enters clinical practice.
"In animal research, one thing you keep looking for is the mechanism of action," he says. "If you can figure out the mechanism, you could come up with a drug you could use in the setting of an acute heart attack."
Viagra or another preconditioning drug could eventually be given to someone at high risk of a heart attack, such as a person suffering unstable angina, Vetrovec says.
"Or it could be used before bypass surgery, to induce a transient decrease in blood flow," he says. "Patients who are at risk of a small heart attack during bypass surgery would most probably benefit from it."
What to Do
You can get more information about the established use of Viagra from the U.S. Food and Drug Administration.
Or, here are some frequently asked questions about the drug.
