Effects of the catechol-O-methyltransferase inhibitor tolcapone in Parkinson's disease: correlations between concentrations of dopaminergic substances in the plasma and cerebrospinal fluid and clinical improvement.

We compared the concentrations of dopaminergic substances in the plasma and cerebrospinal fluid (CSF) with clinical severity in patients with Parkinson's disease (PD) under L-dopa/carbidopa treatment and under L-dopa/carbidopa+tolcapone treatment. Compared with treatment with L-dopa/carbidopa alone, the co-administration of tolcapone produced a significant decrease in clinical severity; a remarkable reduction in the 3-O-methyldopa (3-OMD) concentration and significant increase in the L-dopa concentration both in the plasma and CSF; and a significant increase in the dopamine concentration in the CSF. The clinical effects of tolcapone were closely correlated with the reduction in the 3-OMD concentration, but not with the increase in the dopamine and L-dopa concentrations in the CSF.