In the first study, researchers from the Instituti Clinici di Perfezionamento in Milan analyzed echocardiogram images from 155 patients who were on a variety of Parkinson's drugs, and compared them to a sample of 90 healthy people. Twenty-three percent of patients on the Parkinson's drug pergolide -- sometimes marketed as Permax -- showed moderate to severe valve problems, as did nearly 29 percent of those taking cabergoline; also known as Dostinex, among other names. None of the patients on other Parkinson's medications and less than 6 percent of the control group showed heart valve problems.
In the second study, conducted by scientists in Berlin and in Montreal, more than 11,400 medical records of U.K. Parkinson's disease patients were reviewed. There was between a five-to-seven-times greater risk of leaky valves in patients on pergolide and cabergline than in those on other Parkinson's medications.
"This is an extraordinarily high risk," said Dr. Bryan Roth, a pharmacology professor at the University of North Carolina at Chapel Hill who was not involved in either study. "It's a bad side effect. As far as I know, there are no medications that can reverse it." He added that valve-replacement surgery is the only recourse for people suffering from heart valve damage.
Parkinson's disease -- which can cause tremors, loss of muscle control, and even death -- is usually brought on by a deficiency of the chemical dopamine in the brain. It afflicts roughly 1.5 million people in the United States, and about 6 million people all over the world. The primary treatment is a drug called levodopa, which promotes dopamine production in the brain.
While neither pergolide nor cabergoline are used as primary treatments for Parkinsons, they are often used in concert with levodopa, or instead of levadopa if the condition worsens over time. Additionally, pergolide is sometimes prescribed for restless-legs syndrome; an often-poorly-diagnosed neurological disorder marked by uncontrollable urges to move the legs to stop uncomfortable or painful sensations.
By the time Eli Lilly and Co. had added heart valve damage to the list of potential side effects, pergolide had been on the market for 14 years and had been prescribed to about half a million people. According to Lilly, the risks were only significantly increased for five in 100,000 users.
A paper previously published by Roth warned that pergolide and cabergoline appeared to set off the same heart-related mechanism as fen-phen, which was pulled from the diet pills market when sold as Pondimin and Redux because evidence suggested it caused heart valve problems.