Initial treatment of early Parkinson's disease: a review of recent, randomized controlled trials

Many studies have shown dopamine agonists to significantly improve parkinsonian symptoms compared with placebo in early Parkinson's disease (PD), but how do agonists compare with the standard treatment of levodopa? Recently, three large, multicenter, randomized controlled studies directly comparing a dopamine agonist with levodopa as initial therapy in early PD have been published. These studies suggest that although both agents effectively ameliorate parkinsonian symptoms, levodopa was superior to dopamine agonists as measured by improvement in Unified Parkinson's Disease Rating Scale (UPDRS) scores. However, levodopa was more frequently associated with dopaminergic motor complications, and the dopamine agonists were more commonly associated with adverse events. Until further studies clearly demonstrate the beneficial effects of one therapeutic strategy over another, the decision to initiate treatment in early PD with either an agonist or levodopa will be based on the favorable motor complication profile of agonists versus the more potent antiparkinsonian effects and the favorable side-effect profile of levodopa.