Published: May 2008

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Impulsive Behaviours with Dopamine Agonists

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Prescriber Update 29(1): 9
May 2008

Barry Snow, Neurologist, Department of Neurology, Auckland Hospital

Impulse control disorders such as pathological gambling and hypersexuality can occur in patients taking dopamine agonists for Parkinson's disease.  Due to the unusual nature of these behaviours, often an association is not made with the medicine.  High doses and dose increases of dopamine agonists can trigger the development of impulsive behaviours.  Patients and their family/caregiver should be alerted to the possibility of these reactions and encouraged to seek help from their doctor if they notice unusual behaviours.

Some people with Parkinson's disease develop bizarre behaviours when taking dopamine agonists.  This first came to attention when people taking pramipexole started to gamble pathologically.  This was such an unusual side effect that it took some time to associate the pathological gambling with the medicine.  Since that time, it has become apparent that patients taking other dopamine agonists, such as ropinirole (Requip), pergolide (Permax), bromocriptine (Parlodel) and lisuride (Dopergin), can also develop this disorder.  There have been very few cases of pathological gambling reported with levodopa alone.

Pathological gambling is part of a spectrum of disorders known as impulse control disorders or dopamine dysregulation syndrome.  Other compulsions can include compulsive shopping, eating, and increased sexuality. The dopamine system, as well as controlling movement, is associated with reward.  It seems likely that dopamine agonists can cause patients to feel rewarded by these excessive behaviours.  The impulsive behaviours are bizarre, often embarrassing and shameful.  For this reason, patients may not associate their behaviours with the medicine; or they may feel ashamed and not discuss them with their doctors, or hide them from their families.

The frequency of these disorders has been reported as between 2.8% and 8% of patients with Parkinson's disease who are taking dopamine agonists.  This compares with about 1% in the general population.  The actual prevalence may be higher than previously thought because of the potential concealment by patients.  Risk factors for pathological gambling include being young, male, and having psychiatric co-morbidity. High doses increase the risk of gambling, and patients may develop the disorder shortly after an increase in the dose of their dopamine agonist.

Dopamine agonists remain an important part of the therapeutic options for Parkinson's disease.  Patients and their family or caregiver should be alerted about these potential problems, however, as they can have disastrous personal and financial consequences.  There is no proven treatment for these impulse control disorders, but reduction or elimination of the dopamine agonist is obviously the first step.  SSRI antidepressants may help control the impulsive behaviour.

Competing interests (author): none declared.

Address for correspondence: Department of Neurology, Auckland Hospital, Private Bag 92024, Auckland.

Reference

Gallagher DA, O'Sullivan SS, Evans AH, et al. Pathological gambling in Parkinson's disease: Risk factors and differences from dopamine dysregulation. An analysis of published case series. Movement Disorders 2007;22(12):1757-1763.