Abstract
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 language | English |
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Pages (from-to) | 1287-1292 |
Number of pages | 6 |
Journal | Neurology |
Volume | 44 |
Issue number | 7 |
Publication status | Published - 1994 |
ASJC Scopus subject areas
- Arts and Humanities (miscellaneous)
- Clinical Neurology
- Neuroscience(all)