CHICAGO — Evidence continues to mount that dopaminergic therapy increases the odds of impulse control disorders in patients with Parkinson's disease.

Dopamine agonist (DA)-treated patients had two- to threefold elevated odds of having a current impulse control disorder (ICD), compared with non-DA-treated patients (17% vs. 7%, odds ratio 2.72, P less than .001) in an international, cross-sectional study of 3,090 patients with idiopathic Parkinson's disease.

This pattern was observed across all four impulse control disorders assessed: pathological gambling (3.5% vs. 1.6%, OR 2.15), compulsive sexual behavior (4.4% vs. 1.7%, OR 2.59), compulsive buying (7.2% vs. 2.9%, OR 2.53), and binge-eating disorder (5.6% vs. 1.7%, OR 3.34), Dr. Daniel Weintraub and associates reported in a late-breaking poster at the 12th International Congress of Parkinson's Disease and Movement Disorders.

Previous case reports and cross-sectional studies have suggested an association between DA treatment and ICDs in Parkinson's.

However, they have typically assessed convenience samples of patients, have had relatively small sample sizes, and have not concurrently assessed for all commonly reported ICDs in Parkinson's, according to Dr. Weintraub, a psychiatrist at the University of Pennsylvania, Philadelphia.

Patients in the current study were prospectively recruited from 46 movement disorder centers in the United States and Canada, and assessed using a modified Massachusetts Gambling Screen, a modified Minnesota Impulsive Disorders Interview for compulsive sexual behavior and buying, and DSM-IV Text-Revised proposed research criteria for binge eating.

Their mean age was 64 years, 420 patients (14%) had at least one current ICD, and 36% of patients with an ICD had more than one.

ICD frequencies were similar in patients treated with pramipexole (228 of 1,286, 18%) ropinirole (101/651, 16%) and pergolide (11/50, 22%), suggesting that DA treatment as a class may be a risk factor for ICD development in Parkinson's, the authors concluded.

An ICD was present in 18% of patients taking both a DA and levodopa, 14% of patients taking a dopamine agonist without levodopa, and 7% of patients taking levodopa without a DA.

Dr. Weintraub said that physicians should notify patients that ICDs are a potential adverse event associated with dopamine-agonist and levodopa treatment, and should conduct routine questioning in the context of clinical care.

Dr. Weintraub acknowledged that ICDs have been reported as a complication of deep brain stimulation, but said most patients with an ICD prior to surgery do better after surgery, probably because of decreased medication.

In a logistic regression analysis, independent risk factors for ICD development included: age of 65 years or younger (OR 2.39), dopamine agonist treatment (OR 2.76) and higher DA dosage (greater than 150 mg, OR 2.15), levodopa treatment (OR 1.53) and higher levodopa dosage (greater than 450 mg, OR 1.45), not being married (OR 1.47), and self-reported family history of gambling problems (OR 2.21).

The study was funded by Boehringer Ingelheim. Dr. Weintraub has received consulting fees, honoraria, or grant support from Boehringer Ingelheim, BrainCells, EMD Serono, Novartis, Ovation, and Wyeth.

Impulse Control Disorders Often Go Undiagnosed

Impulse control disorders in Parkinson's disease are often undiagnosed as patients tend to deny or minimize their existence, according to Dr. Howard D. Weiss, a neurologist with Sinai Hospital in Baltimore.

Among 165 patients with idiopathic Parkinson's followed in community-based neurology practices, 23 (14%) were diagnosed with a current or past impulse control disorder (ICD). Nine patients had multiple ICD diagnoses.

However, only 10 cases were identified before participation in the study, according to Dr. Weiss, who reported the findings in a poster at the 12th International Congress of Parkinson's Disease and Movement Disorders.

In 12 cases, the family member was the crucial source of information necessary to make the diagnosis. “We often lack the time or [fail to] ask the right questions,” Dr. Weiss said in an interview.

In one case, a daughter reported that her father was spending large amounts of money at the race track. When specifically asked if he went to the track, said he had no reason to go because he didn't gamble.

Another patient said she was a churchgoer and didn't believe in gambling. However, when asked if she bought lottery tickets, she admitted to spending &dollar;200 a week on tickets and said they were like a magnet she couldn't resist.

Patients with a current or past ICD were significantly younger than were those without an ICD (mean 60 vs. 67 years), had an earlier age of Parkinson's onset (50 vs. 60 years) and diagnosis (51 vs. 61 years), had longer disease duration (10.3 vs. 7 years), had worse Unified Parkinson's Disease Rating Scale motor scores (23.4 vs. 17.5), and used higher doses of dopaminergic medications (917 vs. 589 total daily L-dopa equivalents).

Patients treated with dopamine agonists had an increased odds of developing an ICD (odds ratio 7.1). The odds increased further with a combination of a dopamine agonist and L-dopa (OR 9.9). Levodopa alone was not significantly associated with an ICD.

Dopa Therapy May Up Impulse Disorders in PD