Increased risk of somnolence with the new dopamine agonists in patients with Parkinson's disease - A meta-analysis of randomised controlled trials

Background: Recent case reports and letters have alerted practitioners to the risk of sleep attacks, usually preceded by somnolence, in patients with Parkinson's disease treated with pramipexole and ropinirole. Objective: To quantify the risk of somnolence with the new dopamine agonists pramipexole and ropinirole in patients with Parkinson's disease. Methods: We searched MEDLINE, EMBASE, International Pharmaceutical Abstracts and Cochrane Library, contacted experts and pharmaceutical manufacturers, and manually reviewed all references retrieved to identify possible articles to include. Information on randomisation, blinding, type of treatment and reporting of somnolence were abstracted by 2 independent reviewers. Disagreements were resolved by a third author. Analysis: We made 2 separate analyses. The first analysis compared the risk of somnolence in patients taking either pramipexole or ropinirole to that in patients taking placebo. The second analysis compared the risk of somnolence with these drugs (plus levodopa) versus that with levodopa alone. We calculated pooled relative risk estimates using the random effects model and when no heterogeneity was detected we used the fixed effects model. Results: Four trials were included in the analysis of patients taking pramipexole or ropinirole. compared with those taking placebo. The pooled relative risk of somnolence in this analysis was 4.98 [95% confidence interval (CI) 1.79 to 13.89]. Seven trials were included in the analysis of patients taking levodopa and pramipexole or ropinirole compared with those taking levodopa alone. The pooled relative risk was 2.06 (95% CI 1.47 to 2.88). Conclusion: Patients with Parkinson's disease using pramipexole or ropinirole are at higher risk of experiencing somnolence relative to patients taking placebo. Patients taking levodopa plus either one of these dopamine agonists are at higher risk than those taking levodopa alone. Clinicians should carefully weigh this risk against the benefit of these agents when prescribing these drugs.