Certain Impulse-Control Medications May Not Work for Parkinson’s Disease, Study Suggests

Medications used to manage impulse control disorders may not help Parkinson’s disease patients taking Mirapex (pramipexole) and Requip (ropinirole), and may even worsen their episodes, according to new research.

The study, titled “What drugs modify the risk of iatrogenic impulse-control disorders in Parkinson’s disease? A preliminary pharmacoepidemiologic study,” was published in the journal PLoS One.

Mirapex and Requip are dopamine promoters, which are effective in managing Parkinson’s disease symptoms such as muscle spasms and tremors. Parkinson’s is characterized by the death of dopamine-producing (dopaminergic) neurons. Dopamine is an important molecule used for communication between neurons, and loss of this communication leads to many of the observed symptoms.

However, Mirapex and Requip can cause impulse control disorders (ICDs) as a side effect, or aggravate those that normally occur as a part of the disease. These behaviors include compulsive gambling, shopping, and hypersexuality, and can be very disruptive to a person’s daily life.

Treating ICDs poses a challenge in Parkinson’s, as options are limited for both medications and other counteractive strategies. Tapering the doses of Mirapex and Requip, for instance, can worsen other symptoms of Parkinson’s and even lead to dopamine agonist withdrawal syndrome (DAWS), which may produce symptoms such as anxiety, panic attacks, depression, irritability, and fatigue.

The study noted that although clinical trials have identified several types of medication to treat ICDs, there is “no conclusive evidence” that these treatments are useful in Parkinson’s cases. The researchers gathered data from 7,375 adult Parkinson’s patients, who had reported at least one ICD incident. They filtered these to 935 patients who had received Mirapex or Requip at or after their first Parkinson’s diagnosis, had no record of an ICD episode prior to their diagnosis, and were taking at least one of five categories of psychiatric medication to treat ICD.

Three types of medication were most common among these Parkinson’s patients: glutamatergic modulators (mainly amantadine, taken by 86%, followed by memantine, 15.5%), selective serotonin reuptake inhibitors (mostly escitalopram, 72.7%, followed by sertraline, 29.8%, and fluoxetine, 14.1%), and atypical antipsychotics (mainly quetiapine, 91.4%, and olanzapine, 18.1%).

None of these medications seemed to reduce the risk of further ICD episodes. In fact, glutamatergic modulators and selective serotonin reuptake inhibitors appeared to increase that risk.

The authors point out that “the results of this analysis should not be considered conclusive, due to [its] observational nature.” In an observational study, inferences are made based upon past observations, often without knowing whether other factors might have influenced those observations.

These preliminary findings suggest that several key medications to treat ICD may not be appropriate for Parkinson’s disease. This is an important observation, the researchers said, to guide future experiments in more controlled settings and with larger patient sample sizes.