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A clergyman who rarely visits a casino, and then loses no more than $20 at
a pop, suddenly becomes a compulsive gambler and starts bleeding his bank
account dry. Another man becomes so aroused that he chases his wife around
the house demanding sex. They both developed addictive behaviours after taking a particular type of drug to treat Parkinson's disease, say researchers at the Mayo Clinic in Rochester, Minn. And their study shows that patients who suddenly developed a pathological need to try to beat the odds against one-armed bandits, a roll of dice or a hot hand of cards completely lost the compulsive behaviour after stopping the drug. "One patient said it was like a light switch going off," said Dr. Leann Dodd, a Mayo Clinic psychiatrist and co-author of the study. The study reports on two women and nine men with Parkinson's disease who came in for routine appointments with their neurologists and mentioned they were gambling too much, or a family member said they were acting out of character. After hearing reports that certain drugs - called dopamine agonists - appeared to be linked to compulsive behaviour, the neurologists began tapering their patients off the medications. Some of the patients had already stopped taking the drugs on their own. "They began to hear back from the patients that this created a dramatic resolution of their symptoms," Dr. Dodd said Monday from Rochester. Dopamine agonists work on certain receptors in the brain to boost the levels of dopamine, a chemical that is diminished in people with Parkinson's disease. These D3 receptors are clustered in the limbic system, "which has a lot to do with a person's emotional behaviour and mood and internal reward system," Dr. Dodd said. Among the dopamine agonists, a drug called Mirapex (pramipexole) appears to have the strongest effect on these receptors. She hypothesizes that D3 receptors in some Parkinson's patients are genetically more sensitive to the drug, "so that when that chemical hits that receptor it does something different with them." "These are tragic cases," she said, noting that the clergyman drove by a casino for many, many years, stopping in "every five years or so and maybe lost $20." "Then he began to have to go there all the time, every day, and losing quite bit of money, keeping this secret from his wife. So there were very devastating character difficulties and moral character difficulties that he was having." But the patients weren't affected by just compulsive gambling. About half reported suddenly developing addictions to food, alcohol or sex. "At least in a couple of cases, spouses stated that the patients (men) became very hypersexual, to the point of chasing the spouse around the house seeking out sex. "These are things that can destroy relationships and that's why it's so important to get both clinicians and patients aware that if something a little out of character's going on, they really need to get with their physician and discuss it." Still, Dr. Dodd stressed the side-effect is rare. One study of more than 500 Parkinson's patients taking Mirapex estimated that about 1.5 per cent developed addictive behaviours. "The main thing I want people to realize is that this still is a very unusual occurrence, that they don't need to be panicked and discontinue their medication, because these are still really good medications for their disease process." Parkinson's disease is a progressive disorder of the central nervous system that affects movement, muscle control and balance. The exact cause is unknown, but research has shown that by the time symptoms develop, patients have lost up to 90 per cent of dopamine-producing cells in the brain.
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