Pharmacokinetic-Pharmacodynamic Modeling of Levodopa in Patients With Advanced Parkinson Disease

The motor complications during long treatment therapy in patients with advanced PD especially with stage 3 Hoehn and Yahr scale were correlated to the higher plasma concentrations of l-dopa. In the presented study, patients with motor complications, especially with DID dyskinesias, exhibited a larger threshold level (EC50). The clinical improvement of a patient who received l-dopa and tolcapone can be explained by tolcapone-induced changes of peripheral and central l-dopa pharmacokinetics, which led to a decrease of l-dopa EC50 and 3-OMD concentrations. Our data indicate that pk/pd analysis may be helpful for monitoring the efficiency of therapeutic strategy applied in PD patients.