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To learn more about adverse effects of treatment with dopamine agonist pramipexole or with levodopa in Parkinson disease (PD), researchers took a closer look at data from the study, Comparison of the Agonist Pramipexole versus Levodopa on Motor Complications of Parkinson's Disease (CALM-PD).
Two-year and four-year analyses in CALM-PD showed a lower incidence of wearing off and dyskinesias in the pramipexole group and improved motor function in the levodopa group. Secondary analyses revealed that somnolence, edema, and hallucinations were more common than anticipated, and these findings were the impetus for the current investigation.
Within 4 years of treatment, 35% of all patients had new or worsened somnolence, 45% had new or worsened edema, and 17% developed hallucinations. Comorbid illness, type of initial dopaminergic therapy, age, gender, and cognitive status were all important risk factors for these adverse effects. Somnolence was associated with male sex, burden of comorbid illness, and initial treatment with pramipexole. Edema was associated with female sex, comorbid cardiac disease, and pramipexole. Development of hallucinations was associated with older age, worse Mini-Mental State Exam scores, and burden of comorbid disease. Initial pramipexole treatment was not found to independently increase the risk of hallucinations, and the authors suggested that previously reported associations might have been overstated or might apply only to patients with advanced disease. Curiously, younger patients treated with pramipexole were at higher risk for hallucinations than those treated with levodopa. The authors noted that this finding contradicted conventional wisdom and therefore would need confirmation.
Biglan KM et al. Risk factors for somnolence, edema, and hallucinations in early Parkinson disease. Neurology 2007 Jul 10; 69:187.
Comment
These findings add to an important and emerging literature about risk factors for somnolence, edema, and hallucinations associated with PD. Comorbid illnesses are often overlooked when treating patients, and this paper emphasizes their importance. The authors are insightful in drawing attention to the need for counseling when initiating PD therapies. Patients and families should be prepared for these potential side effects and for another not covered in this paper: compulsive and impulsive behaviors. Neurologists and general practitioners must weigh the pros and cons of available therapies, based on existing information, and this study should help guide them.