The impact of treatment with levodopa on Parkinson's disease.

The progress of 178 patients with Parkinson's disease who began treatment with levodopa between November 1969 and December 1972 is reviewed after six years. One hundred and twenty-five patients showed an initial improvement of their individual total disability scores exceeding 25 per cent, but after six years of sustained treatment only 37 patients still obtained similar benefit. By 1978 only five patients had maintained their initial improvement compared to 69 patients after two years therapy; however, 47 patients were still better than before treatment. The overall mortality ratio--the ratio of observed to expected death rate--for all the patients was 1.45:1. In those patients who unable to tolerate levodopa for longer than two years the ratio was 2.38:1; in those who were able to tolerate sustained medication, life expectancy was normal (ratio of 0.91:1 for males and 1.14:1 for females). Involuntary movements were the commonest complication of treatment. Three main types were distinguished. Peak dose dyskinesias, beginning 20 to 90 minutes after an oral dose and most severe midway through the inter-dose period, affected 80 per cent of patients. Early morning and end-of-dose dystonia occurred in 20 per cent of patients and biphasic dyskinesia--two distinct episodes of involuntary movements within each inter-dose period--was the least common pattern affecting 3 per cent of patients. Involuntary movements increased in frequency and severity as treatment continued. End-of-dose deterioration ('wearing-off' effect of individual doses) occurred in 65 per cent of patients: unpredictable oscillations in motor performance (the 'on-off' phenomenon) unrelated to the time and dosage of levodopa, occurred in 10 per cent. Psychiatric side effects included toxic confusional states, visual pseudohallucinations and paranoid psychoses and constituted the most frequent reason for stopping medication. Forty (22 per cent) of the patients had suffered severe depression before the onset of disease and levodopa had no sustained antidepressant effect in this group. After six years of treatment with levodopa, 32 per cent of the patients had unequivocal dementia.