An open-label, multicentre clinical trial to determine the levodopa dose-sparing capacity of pramipexole in patients with idiopathic Parkinson's disease

Summary. Ninety-three patients with idiopathic Parkinson's disease (PD) entered a 12 week open-label, baseline controlled, multicentre study. The study was designed to determine the levodopa sparing effect of pramipexole as add-on treatment in PD while maintaining an optimal clinical improvement in motor performance. The overall reduction in adjusted levodopa dose was the primary endpoint. Unified Parkinson's Disease Rating Scale (UPDRS) subscores as well as motor fluctuations, frequency and severity of dyskinesia (assessed by patient diaries) were secondary endpoints. Pramipexole permitted a median reduction of adjusted levodopa by 40% while maintaining or improving the UPDRS scores in 61 patients (per protocol [PP] analysis). The intent-to-treat (ITT) analysis (90 patients) similarly revealed a median reduction of 40%. An anticipated short-term levodopa dose reduction as substantiated by 95% confidence interval calculations lies within a range of 35% to 50%. If unadjusted levodopa doses were considered, a median reduction of 42% (PP) or 43% (ITT) was achieved. 47% patients (ITT) had a levodopa dose reduction (adjusted) of more than 40% while maintaining or improving their level of efficacy, and 72.2% had a reduction of at least 20%. Motor fluctuations improved compared to baseline according to patient diaries and UPDRS part IV. These findings suggest that pramipexole can markedly reduce the daily levodopa dosage without deterioration of motor response and support that this new selective D2/D3 receptor agonist also improves later levodopa-associated motor complications. Received November 11, 1999; accepted April 7, 2000