Longitudinal monitoring of the levodopa concentration-effect relationship in Parkinson’s disease

Manuela Contin, R. Riva, P. Martinelli, P. Cortelli, F. Albani, A. Baruzzi

Research output: Contribution to journalArticlepeer-review


We prospectively evaluated over 4 years the intrasubject relationship betweenlevodopa plasma concentration and the tapping effect after a standard oral levodopa test in28 patients with mild-to-moderate idiopathic Parkinson’s disease. The onset and duration of the tapping effect significantly shortened over years; response amplitude did notvary. Levodopa plasma kinetics remained unchanged. Pharmacodynamic modeling indicated aprogressive decrease in the equilibration half-life between plasma drug concentration andeffect, which correlated with the shorter motor response. No clear-cut change in maximum response (Emax) emerged, but levodopa concentration needed to yield 50%of maximum effect (EC50) significantly increased. These data indicate thatthe duration of motor response becomes a major determinant of drug efficacy over years.The modifications in levodopa effect-compartment equilibration half-life and EC50 further support the suggestion thatalterations in cerebral levodopa kinetics have an important role in the development ofresponse fluctuations.

Original languageEnglish
Pages (from-to)1287-1292
Number of pages6
Issue number7
Publication statusPublished - 1994

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Clinical Neurology
  • Neuroscience(all)


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