Peripheral aromatic L-amino acids decarboxylase inhibitor in Parkinsonism. I. Effect on O-methylated metabolites of L-dopa-2- 14 C.

The effects of MK-486, an inhibitor of peripheral aromatic L-amino acids decarboxylase, on the urinary metabolites derived from orally administered L-Dopa-2-(14)C were studied in three Parkinsonian patients. Treatment with MK-486 before L-Dopa-2-(14)C markedly reduced radioactivity found in catecholamines fraction by 70-80% during 48 hr, but increased 3-O-methyldopa fraction by threefold, as compared with a nonpretreated base line value. Pretreatment with MK-486 for a period of 1 wk resulted in less inhibition of O-methylated amine and acid metabolite fractions than that measured after a single dose of the inhibitor.