Pharmacodynamic modeling of oral levodopa: Clinical application in Parkinson's disease

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

Research output: Contribution to journalArticlepeer-review


We investigated the relationship between levodopa plasma concentration and the tapping effect, after a standard oral levodopa test, by kinetic-dynamic modeling in 40 parkinsonian patients with stable or fluctuating response to levodopa, and found no difference in levodopa plasma pharmacokinetics between stable and fluctuating patients. Conversely, levodopa equilibration half-life between plasma and effect-site concentration was five-fold shorter on average in fluctuating patients. Overall, levodopa equilibration half-life highly correlated with the duration of tapping response and provided a reliable quantitative index of central mechanisms that affect the length of clinical effect. Individual fitting of tapping measures to modeled drug effect-site concentrations by sigmoid Emax model revealed that fluctuating patients required almost two-fold higher levodopa concentrations (EC50) to elicit almost the same motor response (Emax). These findings suggest that shortening of levodopa clinical effect may be accompanied by a reduced drug affinity for the nigrostriatal dopaminergic system (EC50), with no change in its intrinsic activity (Emax).

Original languageEnglish
Pages (from-to)367-371
Number of pages5
Issue number2
Publication statusPublished - Feb 1993

ASJC Scopus subject areas

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

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