Excretion of L-Dopa and Its Metabolites in Urine of Parkinson's Disease Patients Receiving L-Dopa Therapy

Abstract

Abstract L-Dopa and its major metabolites were separated from daily 24-h urines from patients with Parkinson’s disease, who were being treated with increasing doses of the drug, up to 4 g per day. An aliquot of each sample was passed through three different ion-exchange columns. Catecholamines (dopamine, epinephrine, norepinephrine, metanephrine, and normetanephrine) were retained on a cation-exchange column, eluted with boric acid, and quantitated by fluorometric analysis. Catechol acids, present in the effluent of the cation-exchange column, were retained on an anion-exchange column. An aliquot of the eluate of the anion-exchange column was used for colorimetric determination of 3,4-dihydroxyphenylacetic acid, while the effluent from this column was used for colorimetric determination of dopa. A second aliquot of the eluate from this column was passed over a column of alumina, which retained all the acidic metabolites except homovanillic acid, which was measured fluorometrically in the effluent from the alumina column. Vanilmandelic acid was determined in another aliquot of each urine sample by use of paper electrophoresis. The excretion pattern elicited suggests a major metabolic pathway for the L-dopa administered to patients with Parkinson's disease.