Treatment of parkinsonism with L-threo-3,4-dihydroxyphenylserine: a pharmacokinetic study.

We have examined the kinetics of oral L-threo-3,4-dihydroxyphenylserine (DOPS) alone and combined with peripheral decarboxylase inhibitors in patients with Parkinson's disease and other degenerative diseases of the brain. Combined administration of L-threo-DOPS and carbidopa or benserazide produced higher plasma concentrations of L-threo-DOPS and suppressed the increase in plasma norepinephrine. This finding indicates some advantages of combined therapy with L-threo-DOPS and decarboxylase inhibitors. Measurable quantities of DL-threo-DOPS were found in the CSF during repeated administration, but there was no consistent change in norepinephrine concentration.