A common class of drugs prescribed to control Parkinson's disease symptoms increases the risk of gambling, excess shopping and compulsive sexual behaviour, a new study finds.

Canadian and American researchers found that study subjects who were taking dopamine agonist drugs, which help control movement problems, were two to three times more likely to have at least one of four common impulse control disorders.

About 13 per cent of subjects had at least one disorder, while one third of the subjects had more than one disorder.

The disorders are pathological gambling, compulsive buying, compulsive sexual behaviour and binge eating.

Of the subjects who were taking dopamine agonists:

  • 4 per cent developed compulsive sexual behaviour.
  • 5 per cent began binge eating.
  • 6 per cent became pathological gamblers.
  • 7 per cent started shopping compulsively.

"The disorders are important because they're often under recognized, they are often not admitted to by the patients," said Toronto Western Hospital's Dr. Anthony Lang, another of the study's authors. "They are behaviours at some times that the patients are seeming to enjoy, at least to begin with, before they become a significant source of disability."

The findings were presented at The Movement Disorder Society's 12th International Congress of Parkinson's Disease and Movement Disorders in Chicago.

Researchers analyzed data from almost 3,100 North American study participants. Subjects were monitored for each impulse control disorder over a period of six months.

This is the first study to evaluate all four common impulse disorders at one time.

Despite the study's findings, patients are not keen to stop the medication. They say the benefits outweigh the risks.

For Parkinson's patient Mary Martin, the drug Mirapex got her out of a wheelchair. She can now walk and take care of herself.

However, the drug has made her want to shop and eat more, as well as gamble obsessively.

"The side effects, although they are bad with this drug, with the compulsive behaviour, I wouldn't trade it," Martin said. "Because I would be afraid to go back to the way I was."

Martin's husband, John, said they were warned of the risks of developing a gambling problem before Mary went on the medication.

But he, too, says its better for he and his wife to work hard to control her gambling than let her health regress so she once again becomes dependent on others.

"To give up Mirapex over something we think we can control, and I hope we don't lose control, as long as we can control the gambling, we sure want the benefits this class of drugs can bring," John said.

Doctors believe that the drugs stimulate the pleasure-seeking regions of the brain. This effect could trigger addictions in patients who already have a genetic predisposition to obsessive behaviours.

"It may be it's not that the drug exclusively causes it," Lang said. "You have to have fertile ground that then the drug plays on and adds to that creates the more problematic behaviour."

Doctors hope to develop a test to determine which patients are most at risk for compulsive behaviours. Then, scientists will be able to create new drugs that won't lead to such side effects.

With a report from CTV medical correspondent Avis Favaro and producer Elizabeth St. Philip.

Abstract:

Dopaminergic Therapy and Impulse Control Disorders in Parkinson's Disease: Top Line Results of a Cross-Sectional Study of Over 3,000 Patients

Authors: Daniel Weintraub, MD, Juergen Koester, PhD, Marc N. Potenza, MD, PhD, Andrew D. Siderowf, MD, MSCE, Mark A. Stacy, MD, Jacqueline Whetteckey, MD, Glen R. Wunderlich, PhD, and Anthony E. Lang, MD, FRCPC, for the DOMINION Study Group

Objective: To ascertain the prevalence estimates of four impulse control disorders (ICDs; problem/pathological gambling, compulsive buying, compulsive sexual behavior, and binge-eating disorder) in treated Parkinson's disease (PD) patients and examine the association of ICDs with different PD medications.

Background: Case reporting and preliminary cross-sectional studies in PD have suggested an association between dopamine agonist (DA) treatment and ICDs. However, studies to date have typically assessed convenience samples of patients, have had relatively small sample sizes, and have not concurrently assessed for all commonly reported ICDs in PD.

Methods: Patients with idiopathic PD, age range 30-75 years, were recruited for study participation in the context of routine clinical care based on predetermined, site-specific recruitment plans designed to minimize selection bias. Subjects were assessed for a current (past 6 months) ICD using a modified Massachusetts Gambling Screen (MAGS) for problem/pathological gambling, a modified Minnesota Impulsive Disorders Interview (MIDI) for compulsive sexual behavior and buying, and DSM-IV research criteria for binge-eating disorder. Odds ratios with 95% confidence intervals were calculated and a Cochran-Mantel-Haenszel test was performed for comparing of ICD frequencies in DAversus non DA- treated groups and pramipexole- versus ropinirole-treated groups.

Results: A total of 3090 patients (64.1% male; mean age =63.8 years; DA treatment =66.0%) at 46 sites in the United States (N=33) and Canada (N=13) completed the initial assessment. One or more current ICDs were identified in 13.6% of patients. ICD patients were slightly younger than non-ICD patients (mean age =60.2 vs. 64.4 years, respectively; P<.001) and were more likely to have a self-reported family history of gambling problems (7.1% vs. 3.6%, respectively; P<.001); there were no between-group differences in gender (P=.71) or disease severity as measured by Hoehn and Yahr stage (P=.93). ICDs as a group were more common in DA-treated than non DA-treated patients (17.1% versus 6.9%, respectively; odds ratio [95% CI] =2.72 [2.08;3.54], P<.001). This same pattern was observed for each of the ICDs evaluated. Overall ICD frequency for DA treatment alone versus DA plus levodopa treatment was similar (14.1% vs. 17.7%, respectively; P=.10). Among individual DAs, there was no difference in overall ICD frequency for pramipexole- and ropinirole-treated patients (17.7% vs. 15.5%, respectively; odds ratio [95% CI] =1.22[0.94;1.57], P=.14). In DA-treated patients, the most common ICD was compulsive buying (7.2%), followed by problem/pathological gambling (6.4%; pathological gambling =3.5%), binge-eating (5.6%), and compulsive sexual behavior (4.4%).

Conclusions: In this study the DA-treated group had a two- to three-fold elevated odds of having at least one of the four commonly reported ICDs in PD compared with the non DA-treated group, a finding which applied to each of the ICDs assessed. The elevated odds represented a class, as opposed to a specific medication, finding. Although previous ICD research in PD has focused on pathological gambling, a broad range of ICDs is observed in PD patients. Additional analyses will examine other clinical correlates of ICDs in this patient population.