When Tammy Rothwell started taking a prescription drug called Mirapex for the symptoms of her Parkinson’s disease, she thought she had finally found peace after 25 years.
But as Rothwell’s muscle tremors faded under the medication, a new problem arose.
Rothwell, who said she had never gambled and was careful with her money before starting Mirapex, began compulsively spending $200 a day on scratch-off lottery tickets and making irrational purchases like 100 tubes of lipstick. The habits escalated so rapidly, Rothwell said, she ran through more than $70,000 in two years.
“It was night and day. There was another person there,” Rothwell said. “I was manic to the point where there was another person inside of me. I knew that I could not do anything about it, I had no control whatsoever, and I’m a control freak.”
Neurologists have long observed dramatic changes in the behavior of patients receiving treatment for Parkinson’s disease, with some developing gambling problems, heightened sexual interest or compulsive spending and eating habits where there had previously been no sign of such disorders.
Now, the largest study ever conducted on the phenomenon has found that more than 13 percent of patients taking a particular class of drug called dopamine agonists, sold under brand names including Mirapex and Requip, suffer from at least one of four serious behavioral addictions.
The results, presented in June at the International Congress of Parkinson’s Disease and Movement Disorders conference in Chicago, could change the way neurologists choose to treat certain patients with movement disorders like Parkinson’s.
But the observation that a drug may trigger dramatic behavioral changes in some people _ changes many said switched off almost immediately when they stopped taking the drug _ also offers new evidence that issues like gambling and shopping addictions have roots in the balance of chemicals in the brain.
“It offers a real window that’s hard to duplicate in other populations; it’s hard to make a gambling problem or an eating problem go away relatively quickly,” said Dr. Daniel Weintraub, assistant professor of psychiatry at the University of Pennsylvania and lead author on the study. “I think this research really opens up a lot of interesting questions, not only for Parkinson’s disease but perhaps for the general population as well.”
Parkinson’s disease, marked by motor symptoms such as muscle tremors, rigidity and slow, uncoordinated movements, results from the depletion of the neurotransmitter dopamine in the brain. As such, most drugs given to Parkinson’s patients are meant to replace the missing dopamine and restore normal motor function.
Yet dopamine controls more than motor function; it also plays a role in the brain’s response to rewards like eating, drugs and sex. Powerfully activating the dopamine system with drugs could cause people to find such stimuli more rewarding than normal, inducing them to repeat behaviors to the point of physical or financial harm.
“It’s a good thing to have sex, a good thing to eat, good thing to be risky,” said Celeste Napier, professor of pharmacology at Rush University Medical Center. “But if these natural good things get exaggerated by having so much dopamine in critical parts of brain, that may enhance impulsivity and compulsive behaviors.”
But other researchers caution that the brains of Parkinson’s patients are changed drastically by the disease, and the link between dopamine and compulsive behaviors may not be so clear-cut in the general population. That only a subset of Parkinson’s patients on dopamine agonists develop behavioral addictions also suggests the presence of unknown factors that make certain brains more sensitive to the drugs than others.
“The whole issue of how Parkinson’s disease presents the biology of this is not clear yet,” said Dr. Un Jung Kang, professor of neurology at University of Chicago, “but it really provides a fascinating neurobiological angle.”
The study, which looked at more than 3,000 patients from 46 medical centers in the United States and Canada, found that Parkinson’s patients on dopamine agonists are nearly three times more likely to have at least one impulse control disorder compared to patients receiving other treatments.
The study was funded by Boehringer Ingelheim, the German pharmaceutical company that produces Mirapex, one of the most commonly prescribed drugs for Parkinson’s disease.
Kate O’Connor, spokeswoman for the company, said that warnings about the potential development of compulsive behaviors have been included with the drug’s package insert for several years.
“We do feel we are already making people aware so they can watch for any such behavior in patients, so that choices can be made about treatment,” O’Connor said. “There is nothing about the study that told us anything should be changed in the way the drug is used.”
But while neurologists agreed that drugs like Mirapex have helped thousands of Parkinson’s sufferers control their symptoms, the occurrence of such severe behavioral side effects have made them cautious about their use.
Dr. Eric Ahlskog, a neurologist at the Mayo Clinic who has treated Parkinson’s patients for 25 years, said he no longer is comfortable starting patients on dopamine agonists after three patients in his practice last year developed significant gambling and sexual problems.
One patient, a middle-aged man, suddenly began expressing hypersexuality and was arrested for publicly exposing himself.
“If you get hit in the head often enough, you learn to look up,” Dr. Ahlskog said. “You realize it’s such a tragedy … whatever good they get from the drug is far overshadowed by these tragic developments in their life.”
Other neurologists said they won’t stop prescribing the dopamine agonists but have started using smaller doses and closely monitoring patients for the onset of harmful addictions.
Because many patients don’t associate their new habits with the drug, or might be embarrassed to bring such problems up with their neurologist, some doctors now ask patients and their families about compulsive behaviors like gambling and sexual fantasies as part of routine patient checkups.
“Some patients think they’re morally weak people, they think it’s their fault,” said Dr. Kathleen Shannon, a neurologist at Rush University Medical Center. “I sometimes really have to convince people it’s the drug. But as soon as people come off of it they realize have a whole different feeling about gambling … it’s really an amazing observation.”
Cindy Horn of Bloomingdale, Ill., said she didn’t associate the drug she was taking for her Parkinson’s symptoms – Requip, manufactured by Glaxo SmithKline – with any behavioral issues until her doctor asked about her spending habits.
The question made her realize that her spending had spiraled out of control while on a high dose of the drug, spending nearly $30,000 and maxing out several credit cards on what she now recognizes were irrational, impulsive purchases of clothing, appliances and vacation packages.
“Instead of buying just one, I would buy 10,” Horn said. “My children were trying to put the brakes on, but no one could tell me what to do. I didn’t know who it was; it was somebody else.”
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