Even a low dose of a dopamine agonist medication could cause an impulse control disorder in some people with Parkinson’s, a Scandinavian multi-centre study, IPAPS (Impulse control disorder Parkinson Agonist Pharmacology Study) has found.
Over the past ten years, it has become clear that taking dopamine agonist medications can lead to some people with Parkinson’s developing an impulse control disorder. This is where a person develops extreme behaviours such as compulsive gambling, excessive spending, hypersexuality or binge-eating. This can have a detrimental impact on their lives and relationships with others, as well as have potential financial or legal implications.
Impulse control and dopamine agonist study
Until now, it has been assumed that impulse control problems are related to the dosage size of a dopamine agonist medication. However, the study’s research into two dopamine agonist medications now partly rejects this. As a result, in Norway levodopa is now the recommended first-choice treatment for Parkinson’s symptoms.
Conducted at four sites in Norway and one in Sweden, the clinical and pharmacological study set out to find out more about the mechanisms behind impaired impulse control, and the role of dopamine agonist medications in this.
Starting as a collaboration between the University of Oslo and The Arctic University of Norway in Tromsø, IPAPS recruited 100 people with Parkinson’s who took regular doses of the dopamine agonist medications pramipexole or ropinirole.
The participants were interviewed, examined, and filled in different rating scales for impulse control and other problems related to Parkinson’s.
Blood was drawn for pharmacological analyses three times in one day – just before the daily dopamine agonist dose, and after six and twelve hours – allowing for accurate measurements of dopamine agonist serum concentrations throughout the day. Degrees of impaired impulse control were correlated to dopamine agonist use and serum concentrations.
New findings for pramipexole and ropinirole
Initial results based on a fraction of the study cohort were published by the European Journal of Neurology last year. More exhaustive findings based on all 100 study participants were published in a separate article by the European Journal of Neurology in January this year.
In the case of pramipexole, no correlations between impaired impulse control and pramipexole dose or serum concentrations were found – meaning that even a low dose of it could lead to some people with Parkinson’s developing an impulse control disorder. This finding led the study’s scientists to advise that those who show signs of an impulse control disorder while on pramipexole should stop taking it.*
As regards ropinirole, both daily dose and total drug exposure (serum concentrations throughout the day) showed a weak but significant correlation with impaired impulse control. These results suggest that ropinirole users experiencing problems with impulse control could benefit from reducing their dose.*
Changes to recommendations in Norway
Dr Espen Dietrichs, a neurologist/movement disorder specialist and professor at the Institute for Clinical Medicine at the University of Oslo and one of the study’s senior authors, says: “Taken together, our results seem to imply that pramipexole treatment should be stopped in people with Parkinson’s that develop impaired impulse control, as these problems are not related to dopamine agonist dose or serum concentrations.
“In ropinirole users having similar problems, a dose reduction may be beneficial and could be tried out as both ropinirole dose and serum concentrations seem to have some importance.”
The study’s insights into the risks of impulse control disorders when taking dopamine agonist medication have changed the recommendations for treating Parkinson’s symptoms in Norway.
Whereas previously, dopamine agonist medications and levodopa treatment were considered equal alternatives when starting treatment for those newly diagnosed with Parkinson’s, now five Norwegian Parkinson’s experts have recommended levodopa alone as the first choice for treating the condition’s symptoms.
*Please consult your neurologist before halting or reducing any Parkinson’s medications.
