Amantadine for levodopa-induced dyskinesias - A 1-year follow-up study

Background: In a recent acute study, amantadine was found to have antidyski netic effect against levodopa-induced motor complications in patients with Parkinson disease. The longevity of this effect was not addressed but is of interest in light of the controversy in the literature regarding the durat ion of amantadine's well-established antiparkinsonian action. Objective: To determine the duration of the antidyskinetic effect of amanta dine in advanced Parkinson disease. Design: One year after completion of an acute, double-blind, placebo-contro lled, crossover study, patients returned for re-evaluation of motor symptom s and dyskinesias using a nonrandomized, double-blind, placebo-controlled f ollow-up paradigm. Setting: National Institutes of Health Clinical Center. Patients: Seventeen of the original 18 patients with advanced Parkinson dis ease complicated by dyskinesias and motor fluctuations participated in this study; 1 was lost to follow-up. Thirteen of the 17 individuals had remaine d on amantadine therapy for the entire year. Interventions: Ten days prior to the follow-up assessment, amantadine was r eplaced with identical capsules containing either amantadine or placebo. Main Outcome Measures: Parkinsonian symptoms and dyskinesia severity were s cored using standard rating scales, while subjects received steady-state in travenous levodopa infusions at the same rate as I year earlier. Results: One year after initiation of amantadine cotherapy, its antidyskine tic effect was similar in magnitude (56% reduction in dyskinesia compared w ith 60% 1 year earlier). Motor complications occurring with the patients' r egular oral levodopa regimen also remained improved according to the Unifie d Parkinson's Disease Rating Scale (UPDRS-IV). Conclusion: The beneficial effects of amantadine on motor response complica tions are maintained for at least 1 year after treatment initiation.