Can't stop gambling or shopping? Parkinson's meds may be to blame, JAMA study finds

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When Parkinson's disease patients start taking new meds, doctors go on the lookout for the usual side effects: dizziness, nausea, and the like. But according to a new study, they need to think weird, too. The risk of compulsive behavior--gambling, shopping, sex--is much higher than previously thought.

Red flags about impulse control problems have surfaced before; in fact, patients have sued Boehringer Ingelheim, blaming its drug Mirapex triggered pathological gambling. But the side effects were considered rare. Untrue, says Thomas Moore of the Institute of Safe Medication Practices and a lead author of the JAMA Internal Medicine study.

And given the fact that these meds aren't restricted to Parkinson's patients, but used in patients with such ailments as restless leg syndrome, that means thousands of people may be behaving in ways they never dreamed possible. Pathological gambling, compulsive shopping, sexual obsessions--the sort of behavior that people aren't likely to share with their families voluntarily, much less their doctors.

"These psychiatric side effects appear to occurring among at least 10% of patients," Moore told HealthDay. "If you compare that with, say, the risk of suicide among patients who take antidepressant drugs, this is much higher. It's an astronomical rate, in terms of adverse event risk."

The authors are calling on the FDA to add a "black box" warning to the labels on dopamine agonists, a class that includes such drugs as GlaxoSmithKline's ($GSK) Requip, Boehringer Ingelheim's Mirapex, and UCB's Neupro. According to the study, the link to compulsive behaviors was strongest for Mirapex and Requip, with patients 277 times more likely to report such problems than patients using other drugs.

These drugs are "a cornerstone of treatment" in Parkinson's, however, so they're not likely to be tossed aside, said Joshua Gagne, an assistant professor at Harvard Medical School and Brigham and Women's Hospital. But patients need to feel free to talk about problems with self-control, he said; right now, the issues probably go underreported. "It's easy to imagine that a patient would be ashamed if they're losing a lot of money gambling or doing things that they generally don't want their family to know about," he said (as quoted by HealthDay). And that means that the problems are probably underestimated even now.

"[W]hile they should continue to be used, it's equally important to know what the risks are," said Gagne, who wrote a commentary accompanying the JAMA study. "So, while more research is done, we need to encourage physicians and pharmacists and patients to discuss the concern, and to help patients be more open about it when these issues take hold."

Parkinson's drugs aren't the only meds linked to behavior changes. Pfizer's ($PFE) stop-smoking remedy Chantix affects dopamine as well, and its current black box warning about psychiatric side effects was backed last week by an FDA advisory panel.

- read the JAMA Internal Medicine abstract