Heart valve defects are linked with two drugs once commonly used to treat Parkinson's disease, according to a scientific study.

The drugs - pergolide and cabergoline - cause the defects in as many as a quarter of the patients who use them, said the study published by the Los Angeles Times on Friday.

The risk is much higher than suspected in previous smaller studies, said the study conducted by Italian and German scientists.

"This is not a rare side effect," said Dr. Bryan L. Roth of the University of North Carolina at Chapel Hill. "That's an extraordinarily high incidence. That makes this a serious problem."

The drugs cause the heart valves to develop fibrous deposits that produce leakage of blood back into the heart. That causes the heart to overwork, which can lead to heart failure and death.

Many U.S. physicians have stopped prescribing pergolide in light of the earlier reports, and cabergoline is not approved in this country for treatment of Parkinson's, said Robin A. Elliott, executive director of the Parkinson's Disease Foundation.

The drugs are much more widely used in Europe and developing countries because they cost less than newer drugs that do the same thing,

Cabergoline, however, is approved for other uses, such as treating brain tumors, and is sometimes used off-label for the treatment of Parkinson's.

The drugs, which are available in generic form from a variety of producers, "have been around a long time, and a large number of people have potentially been exposed to them," said Dr. Michael S. Okun, medical director of the National Parkinson Foundation.

Parkinson's, which strikes as many as 100,000 Americans each year, is characterized by severe tremors and rigidity in the limbs, and loss of muscle control. It results from the death of brain cells that produce the neurotransmitter dopamine, which plays a key role in transmitting commands from the brain's muscle-control centers.

Source: Xinhua