TUESDAY, April 4 (HealthDay News) -- The commonly prescribed prostate drug doxazosin may increase heart failure risk by blocking specific receptors in heart muscle cells, an animal study suggests.

Doxazosin is used to improve urinary flow in men with enlarged prostates. The drug does this by blocking the action of alpha 1-adrenergic receptors, which increase contraction of smooth muscles. By blocking these receptors, the drug relaxes muscles that control urine flow.

In this study, mice that lacked alpha 1 receptors were subjected to conditions that simulated high blood pressure. Half of the mice that lacked the receptors died of heart failure, and the rest developed a serious form of heart disease called dilated cardiomyopathy. The deaths and heart disease in these mice were apparently due to the lack of alpha 1 signaling ability in heart muscle cells, the researchers said.

When normal mice were subjected to the same kind of high blood pressure-like conditions, they all survived.

The findings appear in the April issue of the Journal of Clinical Investigation.

"While you can't jump to conclusions about humans based on mouse results, it might not be a good idea to block this receptor. I think doctors and researchers need to pay more attention to the possibility that these drugs are making people worse," principal investigator Dr. Paul. C. Simpson, a staff cardiologist at San Francisco VA Medical Center, said in a prepared statement.

The findings also suggest that alpha 1 receptors may provide a new target for drugs to treat heart failure.

"We've studied what happens when these receptors aren't present," added Simpson, who is also a professor of medicine at the University of California, San Francisco. "But what happens when you take a drug that specifically activates them? Can you stimulate them to cause the heart muscle cell to recover when it's injured, or grow stronger when it's weak?"

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about enlarged prostate.