Plasma concentration of levodopa in Parkinsonism before and after inhibition of peripheral decarboxylase

Abstract

Levodopa has been administered to Parkinsonian patients with and without an extracerebral decarboxylase inhibitor. Dyskinesia was the commonest dose-limiting factor on both regimens. For each individual patient dyskinesia occurred at the same plasma concentration of levodopa. In view of this “within-patient” correlation between dyskinesia and the plasma concentration of levodopa, attempts to improve therapeutic results by augmenting the plasma levodopa are unlikely to be successful except in those patients with severe gastrointestinal side-effects.