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News in Brief

Dopamine Agonists Linked to Impulse Control Disorders in PD

People with Parkinson’s disease (PD) who take dopamine agonists are about three times more likely than those who do not to develop certain compulsive behaviors, according to a study in the May issue of Archives of Neurology.

In the largest study to date of impulse control disorders (ICD) in PD, researchers led by Daniel Weintraub, M.D., at the University of Pennsylvania School of Medicine, interviewed more than 3,000 people with Parkinson’s being treated at 46 centers in the United States (US) and Canada.  Nearly all of the participants were taking levodopa and/or a dopamine agonist.  Dopamine agonists are a class of Parkinson’s medications that include pramipexole (Mirapex®) and ropinirole (Requip®). 

Using standardized assessment tools, the researchers identified impulse control disorders in 13.6 percent of participants.  Earlier studies on dopamine agonists and ICD had focused primarily on pathological gambling.  The new report; however, found that four impulse control disorders occurred at similar rates: problem gambling (5 percent), compulsive sexual behavior (3.5 percent), compulsive shopping (5.7 percent), and binge eating (4.3 percent).  The researchers identified two or more disorders in 3.9 percent of participants.

People taking both levodopa and a dopamine agonist had the highest rate of impulse control disorders, 17.7 percent.  These disorders were identified in 14 percent of people treated only with a dopa­mine agonist, and in 7.2 percent of those taking levodopa alone.  There was no difference in rates between people who took pramipexole and those who took ropinirole.

Patterns of impulse control disorders among study participants mirrored those in the general population.  Those who developed the disorders tended to be younger than those who did not.  They also were less likely to be married, and more likely to smoke cigarettes and to have a family history of gambling problems.  Men were more likely to develop compulsive sexual behavior, whereas women were more likely to be diagnosed with compulsive buying and binge-eating disorders.  The researchers also found that participants living in the US developed problem gambling and compulsive buying behaviors more often than those living in Canada. 

Compulsive behaviors among people with PD who are treated with dopamine drugs are distressful and potentially harmful.  Researchers increasingly recognize the high prevalence of these behaviors in people with PD.  If you or your loved one with Parkinson’s experiences compulsive behaviors, such as gambling, over-eating, shopping, or excessive Internet use, it is important to discuss these issues with your treating physician.

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Deep Brain Stimulation Provides Added Benefit to Medication

Treating advanced Parkinson’s disease (PD) with both deep brain stimulation (DBS) and drug therapies improves quality of life more than drug therapies alone for eligible individuals, according to a report in the online April issue of The Lancet Neurology.

Researchers led by Adrian Williams, M.D., of Queen Elizabeth Hospital in Birmingham, England, studied 366 people whose PD symptoms were not adequately controlled by medical therapy.  In this randomized, multi-center study, half of the participants were assigned to undergo deep brain stimulation — a surgical treatment available for PD that used the now-standard techniques of electrode implantation — and receive state-of-the-art medication treatment.  A second group, matched for age, duration and severity of Parkinson’s, received “best medical therapy” alone.

Participants were treated at medical centers in the United Kingdom.  Many of them received continuous infusion of apomorphine, a Parkinson’s medication not widely used in the US.

The primary goal of the study was to determine the effect of DBS surgery on the quality of life experienced by each participant.  One year after entering the study, all participants answered the 39-item Parkinson’s disease quality of life questionnaire.  The main result was that people in the surgically treated group experienced important improvements in their quality of life, as compared to those in the medication-only group.  These improvements in the surgical group were associated with improvements in mobility, independence in performing activities of daily living and physical discomfort.

As reported in many previous studies, DBS was associated with improvements in many other areas, including rating scale measurements of Parkinson’s symptoms and signs, dyskinesias, and reduction in medication usage.  The surgery was also associated with higher risks than medical treatment alone: nearly 20 percent of the participants receiving DBS had a serious adverse event related to the surgery, including hemorrhage (2 percent), post-operative confusion (3 percent), and infection (9 percent).  

As researchers noted, the primary flaw in the study is that it was not blinded: both the participants and the investigators were aware of who had the surgery.  This type of “open label” trial can lead to a biased result in favor of surgery due to the placebo effect, especially when the primary study outcome is the person’s own measure of quality of life.  To address the potential for a placebo-effect explanation for the DBS benefits, and to evaluate the long-term benefit of surgery, the researchers plan to monitor study participants for up to nine years.

Deep brain stimulation surgery is now a standard treatment for people with Parkinson’s who experience disabling tremors, wearing-off fluctuations and dyskinesias.  This study has confirmed the results of DBS reported in previous studies and is significant because it is the largest randomized study to date, and has focused on quality of life as the main outcome.

For further information, consult PDF’s booklet, Deep Brain Stimulation for Parkinson’s Disease, Third Edition.

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FDA Reviews Safety of Parkinson’s Drug

The US Food and Drug Administration (FDA) announced on March 31 that it is evaluating a possible link between entacapone/carbidopa/levodopa, or Stalevo®,  and increased risk for prostate cancer.  The medication is currently indicated for people living with Parkinson’s who experience end-of-dose “wearing-off.”

The FDA is conducting the investigation due to data that emerged from a clinical trial called, “Stalevo Reduction in Dyskinesia Evaluation — Parkinson’s Disease (STRIDE-PD).“  STRIDE-PD evaluated the onset of dyskinesia (twisting and writhing movements) in people with Parkinson’s who took Stalevo compared to those who took carbidopa/levodopa only.  The trial resulted in an unexpected finding: a greater number of people taking Stalevo were observed to develop prostate cancer than those taking carbidopa/levodopa alone.

The FDA notes that prostate cancer is commonly diagnosed in men of the same age as those included in the trial.  Additionally, earlier trials of Stalevo did not yield increased rates of prostate cancer, and neither did trials of entacapone (Comtan®), a key ingredient of Stalevo.  More study is needed to determine whether there is any relationship between the use of Stalevo and the development of prostate cancer.

In the meantime, men taking Stalevo are advised to discuss their use of the medication with their treating neurologist, and to continue to follow the normal guidelines for annual prostate screening with their internists.  For updates on this topic, check PDF's web site or visit www.fda.gov.