A Cochrane review «Dopamine agonist therapy in early Parkinson's disease»1 «Stowe RL, Ives NJ, Clarke C, van Hilten J, Ferreira J, Hawker RJ, Shah L, Wheatley K, Gray R. Dopamine agonist therapy in early Parkinson's disease. Cochrane Database Syst Rev 2008 Apr 16;(2):CD006564»1 included 29 studies with a total of 5 247 subjects. Participants randomised to a dopamine agonist were less likely to develop dyskinesia (OR 0.51, 95% CI 0.43 to 0.59), dystonia (OR 0.64, 95% CI 0.51 to 0.81) and motor fluctuations (OR 0.75, 95% CI 0.63 to 0.90) than levodopa-treated participants. However, various 'non-motor' side-effects, including oedema (OR 3.68, 95% CI 2.62 to 5.18), somnolence (OR 1.49, 95% CI 1.12 to 2.00), constipation (OR 1.59, 95% CI 1.11 to 2.28), dizziness (OR 1.45, 95% CI 1.09 to 1.92), hallucinations (OR 1.69, 95% CI 1.13 to 2.52) and nausea (OR 1.32, 95% CI 1.05 to 1.66) were all increased in agonist-treated participants (compared with levodopa-treated participants). Agonist-treated participants were also significantly more likely to discontinue treatment due to adverse events (OR 2.49, 95% CI 2.08 to 2.98). Finally symptomatic control of Parkinson's disease was better with levodopa than with agonists, but data were reported too inconsistently and incompletely to meta-analyse.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment and unclear intention-to-treat adherence). The balance of risks and benefits remains unclear; data on patient-rated overall quality of life is lacking.