[Long-term problems of levodopa therapy in Parkinson disease]

The dependence of motor side effects of L-DOPA therapy on clinical and pharmacodynamic parameters was investigated in 28 patients with Parkinson's disease. Duration of disease and degree of motor impairment were significantly less in a first group of 12 patients without motor side effects than in a second group of 16 patients with fluctuations of antiparkinsonian effects and dyskinesias. The two groups showed different pharmacodynamic patterns: the antiparkinsonian effect in the first group remained unchanged, with decreasing DOPA plasma concentrations (Type I), whereas in the second group a direct correlation between DOPA plasma levels and antiparkinsonian effect was observed (Type II). A possible mechanism for the different pharmacodynamic patterns and its relevance for therapy are discussed.