Levodopa-induced dyskinesia: clinical observations.

In 144 patients receiving prolonged treatment with levodopa for Parkinson's disease, an attempt was made to establish possible correlations between the incidence of levodopa-induced dyskinesias and the age of the patient at the onset of the disease, the clinical form of the disease, the duration of symptoms before initiation of the levodopa therapy, the duration of the levodopa therapy and the influence of the concomitant treatment. Levodopa-induced dyskinesia was observed in 92 patients (64%). The age at onset of the disease of patients with dyskinesia was significantly different from the age at onset of those without dyskinesia, the means being 54.8 and 68.9 years respectively. Levodopa-induced dyskinesia occurred less often in the group with preponderant tremor than in those with preponderant bradykinesia (29% vs. 69%). The patients treated with levodopa from the very beginning of their disease were less susceptible to dyskinesia than those who had parkinsonism for some time before receiving levodopa. The influence of the duration of levodopa treatment on the manifestation of dyskinesia could not be confirmed because this side-effect usually appeared during the first year of treatment. The concomitant anti-parkinsonian treatment appeared to have no influence on the incidence of dyskinesia. Biochemical and practical implications of these observations are discussed.