Validation of Dyskinesia Rating Scales

This study will evaluate the responsiveness of a variety of available dyskinesia rating scales to treatment with amantadine or placebo in Parkinson's disease patients with dyskinesia. The study will be a parallel, double-blind, randomized trial of 68 patients treated with amantadine or placebo for 8 weeks. Pre-treatment evaluations will be performed and compared to end of study evaluations on the best treatment dose (200 or 300 mg amantadine or matching placebo) daily. Safety evaluations will be conducted. The responsiveness of the different scales will be evaluated statistically with a mixed model in which changes in the outcome measures over time will include a fixed effect of treatment group assignment. The model will additionally account for random effects of intercepts (the scale scores at baseline) that will include both random variation (person-specific) and specific variation associated with rate of change in outcome. The investigators may include adjustments for possible confounding covariates, including baseline demographics and center. The goal of the program is to provide researchers with the best scale(s) to distinguish dyskinesia change in Parkinson's disease (PD) associated with amantadine in comparison to placebo and to establish the magnitude of effect achievable with amantadine as a comparator "gold standard" that must be met or surpassed by future anti-dyskinetic agents. Additionally, with the use of paper and pencil questionnaires, the study will investigate the impact of patient optimism and patient and rater expectation of positive effects on the dyskinesia rating outcomes.