Drugs Trigger Compulsive Gambling

Drugs called dopamine agonists that are used to treat patients with Parkinson's disease have been found to be associated with habitual, compulsive gambling and large losses of money by people who previously never or only occasionally gambled.

Doctors at the Mayo Clinic (Rochester, MN, USA) learned about the gambling of 11 patients during routine clinic visits. Four of the patients had never gambled before starting dopamine agonist treatment. "Most of the time, the patient came in for a routine exam and would sheepishly admit ‘I've been gambling too much,' or family members would mention that a loved one had been gambling excessively, that this behavior was totally out of character for them, and that gambling was causing problems in their lives,” said Dr. M. Leann Dodd, a Mayo Clinic psychiatrist. Losses of up to $200,000 were reported.

Researchers assessed the relationship of the gambling behavior to the patients' medications and found that all were taking dopamine agonist medications at levels appropriate for Parkinson's treatments. Eight of the patients were also taking the drug carbidopa/levodopa. The researchers located case reports in medical literature associating Parkinson's disease treatment with pathologic gambling, and compared their patients' experiences with those reported in the literature. This revealed that some patients stopped gambling when the use of a dopamine agonist was discontinued.

In seven patients, pathologic gambling developed within one to three months of reaching the maintenance dose or with dose escalation of dopamine agonist treatment. None of the patients reported compulsive gambling while treated with carbidopa/levodopa alone. The other four patients reported compulsive gambling 12-30 months after starting dopamine agonist therapy. Excessive gambling abated in all four within months of discontinuing dopamine agonist treatment. Six of the patients developed additional behavioral issues that subsided when they quit the dopamine agonist medication, including compulsive eating with weight gain, increased alcohol consumption, and hypersexuality.

The dopamine agonist drugs associated with pathologic gambling appear to be those that specifically target the D3 dopamine receptors, according to Dr. Dodd. These receptors are located in the limbic system of the brain, which controls the emotions, affect, and one's internal "reward system.” When this area of the brain is overstimulated, it can lead to more impulsive behaviors and produce a feeling of pleasure from even a previously undesirable activity, such as compulsive gambling or alcohol consumption.

The Mayo Clinic researchers explain that because pathologic gambling is so infrequently associated with dopamine agonist treatment, this potential side effect would not be a reason to stop prescribing it. Instead, doctors should urge patients to be very candid about gambling or other problems that may arise after starting medication. These findings appeared in the July 2005 issue of Archives of Neurology.