WEDNESDAY, April 5, 2006 (HealthDay News) -- New research provides more evidence that some Parkinson's drugs have rare and unusual side effects: They seem to make patients oversexed and turn them into compulsive gamblers.
The behaviors appear in only a small percentage of Parkinson's patients, but they're still more common than in ordinary people, a new study suggests. And the side effects can be serious: 10 people who developed a gambling compulsion after going on drugs such as levodopa lost an average of $150,000 each.
The compulsive behavior in patients who take the drugs "is treatable and reversible, but people need to be aware of it," said study co-author Dr. Valerie Voon, a research fellow at the National Institute of Neurological Disorders and Stroke.
Researchers have known about links between Parkinson's drugs and compulsive behavior since the 1970s when doctors noticed that some patients were "hypersexual," Voon said. In 2005, a study reported on 11 Parkinson's patients who became compulsive gamblers after taking drugs to treat the disease; eight stopped the behavior after going off the medications.
In the new study, Voon and her colleagues surveyed 296 Parkinson's disease patients, many of whom were in their 60s and had developed the illness in their 50s.
The findings were to be presented Wednesday at the American Academy of Neurology annual meeting, in San Diego.
The researchers found that 10 patients -- 3.4 percent -- showed signs of compulsive gambling, about double the percentage seen in the general population. Patients preferred slot machines, Voon said. The devices don't "require as much cognitive process, and there's much more immediate gain as opposed to playing poker or waiting for the lotto to come through," she explained.
The researchers also found signs of oversexed behavior -- including excessive use of Internet pornography and visits to prostitutes -- in seven patients and compulsive shopping in two.
The patients who received two kinds of Parkinson's drugs -- levodopa and dopamine agonists -- were more likely to suffer from the apparent side effects. Sixteen percent of those who used both drugs showed signs of compulsive behavior, compared to 6 percent of those who just used one.
The link between the drugs and the behavior isn't clear. "There's probably some kind of underlying susceptibility," Voon said. "Whether it's an individual [issue] or Parkinson's-related is a separate question."
One potential explanation lies in the actions of dopamine, a brain chemical that sends a "reward" signal to the brain and assists with movement and balance.
If they work properly, Parkinson's drugs adjust dopamine levels to help patients fend the instability caused by the disease. But it's also possible "that the dopamine reward system in the brain is stimulated by these drugs," leading to compulsive behavior, said Paul R. Sanberg, director of the University of South Florida's Center of Excellence for Aging and Brain Repair.
What to do? There's no reason for Parkinson's patients to panic, Voon said. The side effects affect only a small proportion of patients, "and the majority of people do fine."
Still, she said, there's reason to carefully monitor some patients, especially those who have a history of alcoholism and are risk-takers. "If you see those factors, it is possible that person may be more prone to developing these behaviors. Following them carefully would make a lot of sense."
More information
For more on Parkinson's disease, visit the National Institute of Neurological Disorders and Stroke.
