title: Simultaneous determination of L-dopa and 3-O-methyldopa in human platelets and plasma using high-performance liquid chromatography with electrochemical detection.
abstract: Various high-performance liquid chromatographic (HPLC) methods for the determination of plasma levels of L-dopa and of its metabolite, 3-O-methyldopa (3-OMD), have been previously described. In this study, we report a modification of these methods, that enables the assay of these two compounds in platelets and plasma obtained from the same sample of whole blood. Reversed-phase (RP) HPLC with electrochemical (coulometric) detection was used. The within-run and between-run coefficients of variations, for the two compounds, were less than 10%, in both platelets and plasma; the detection limits for platelet levels of L-dopa and 3-OMD were 2 and 6 ng/10(9) platelets, respectively. In plasma, the detection limits for L-dopa and 3-OMD were 1 and 3 ng/ml, respectively. The method is rapid and simple. When applied to a population of patients with Parkinson's disease under treatment with L-dopa, this method revealed detectable levels of L-dopa and 3-OMD in the platelets of all patients. The application of this technique may provide new insights into the pharmacokinetics of L-dopa in patients with Parkinson's disease.
authors.affiliation: Laboratory of Functional Neurochemistry, Neurological Institute C. Mondino, Pavia, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Blandini
authors.forename: E
authors.initials: E
authors.lastname: Martignoni
authors.forename: C
authors.initials: C
authors.lastname: Pacchetti
authors.forename: S
authors.initials: S
authors.lastname: Desideri
authors.forename: D
authors.initials: D
authors.lastname: Rivellini
authors.forename: G
authors.initials: G
authors.lastname: Nappi
mesh_terms: D000328:Adult; D000368:Aged; D000978:Antiparkinson Agents / Q000097:blood* / Q000627:therapeutic use; D001792:Blood Platelets / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry; D005260:Female; D006801:Humans; D007980:Levodopa / Q000097:blood* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000097:blood / Q000188:drug therapy; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use
chemical_list: D000978:Antiparkinson Agents; D014443:Tyrosine; D007980:Levodopa; C008404:3-methoxytyrosine