Pharmacokinetic-pharmacodynamic relationship of levodopa with and without tolcapone in patients with Parkinson's disease.

Objective: To investigate the effect of administration of the catechol-Omethyltransferase (COMT) inhibitor tolcapone on the concentration-effect relationship of levodopa in patients with advanced Parkinson's disease and on-off fluctuations.

Design: Nonblind single-group 2-period pharmacokinetic-pharmacodynamic study.

Patients And Participants: 12 patients, mean age 59 years, with idiopathic Parkinson's disease and response fluctuations.