MILWAUKEE -- The risk of heart valve damage with two drugs for Parkinson's disease may be far greater than was known, new research suggests.
The drugs are not the main treatment for Parkinson's. One of them is also sometimes used to treat restless legs syndrome.
A study by Italian researchers found that about one-fourth of Parkinson's patients taking pergolide or cabergoline -- sold as Permax, Dostinex, and other brands -- had moderate to severe heart valve problems.
Another study, by German doctors, found that users of either drug were five to seven times more likely to have leaky heart valves than patients on other types of Parkinson's medications. Both studies were reported in today's New England Journal of Medicine.
"This is an extraordinarily high risk," said Dr. Bryan Roth, a pharmacology professor at the University of North Carolina at Chapel Hill.
"It's a bad side effect. As far as I know, there are no medications that can reverse it," and valve replacement surgery is the only solution, he said.
Roth had no role in the studies but directs a drug screening program for the National Institute of Mental Health. He also published a paper several years ago warning that these drugs appeared to trigger the same heart-related mechanism that the fen-phen diet combination did. The diet pills, sold as Pondimin and Redux, were pulled from the market in 1997 after they were linked to valve problems.
The Parkinson's drug pergolide, sold as Permax and other brands, also is used to treat restless legs syndrome. Cabergoline, sold as Dostinex, Cabaser and other names, is mostly used in Europe.
About half a million people had taken Permax during its first 14 years on the market when its developer,
Roth believed there were more cases, a theory he said the new studies confirmed.
"This is an example of, if you don't look for it, you don't see it," said Dr. C. Warren Olanow, chairman of neurology at Mount Sinai School of Medicine in New York, who had no role in the work. The findings will lead more doctors to prescribe other Parkinson's treatments, he said.
About 1.5 million Americans and 6 million people worldwide have Parkinson's disease, which results in tremors, loss of muscle control, and sometimes death.
The condition is caused by a lack of the brain chemical dopamine. The main treatment is levodopa, which spurs the body to make more dopamine. Pergolide and cabergoline often are given in addition to that drug or in place of it, especially if symptoms worsen.
In one study, Dr. Renzo Zanettini and others at the Instituti Clinici di Perfezionamento in Milan obtained echocardiogram images of the hearts of 155 patients taking various Parkinson's medications, and heart images of a comparison group of 90 healthy people.
Moderate to severe valve problems were seen in 23 percent of those on pergolide and nearly 29 percent of those on cabergoline, but none were seen on people taking other Parkinson's drugs. The rate of heart problems among those in the comparison group was less than 6 percent. The study was paid for by the Milan clinic and two Parkinson's foundations.
In the other study, Dr. Rene Schade and colleagues in Berlin and in Montreal used records from more than 11,400 Parkinson's patients in the United Kingdom. The rate of newly diagnosed leaky valves was increased among pergolide and cabergoline users but not the others, they found.
Pergolide sales amounted to more than $10 million last year in the United States.