title: High-performance liquid chromatographic determination of methotrexate, 7-hydroxymethotrexate, 5-methyltetrahydrofolic acid and folinic acid in serum and cerebrospinal fluid.
abstract: A method for the simultaneous determination of the antifolates methotrexate and 7-hydroxymethotrexate as well as the folates 5-methyltetrahydrofolic acid and folinic acid (5-formyltetrahydrofolic acid) in serum and cerebrospinal fluid (CSF) is described. High-performance liquid chromatography with gradient elution and dual detection (ultraviolet absorption and fluorescence) was used to separate and quantitate the analytes. Serum samples containing high levels of the substances of interest and CSF samples were injected directly onto the HPLC column. For determination of low concentrations, serum samples were subjected to a solid-phase extraction method for clean-up and concentration purposes. The determination limits were 10 ng/ml for both antifolates, 100 ng/ml for folinic acid, and 0.1 ng/ml for the physiologically occurring methylated folate which is about 1/100 the serum concentration in healthy children. The suitability of the method for pharmacokinetic monitoring of high-dose methotrexate therapy combined with leucovorin rescue administered to children with acute lymphoblastic leukemia was demonstrated. Minimum values of the serum folate during treatment ranged from 0.2 to 3.1 ng/ml. Even those very low concentrations could be reliably measured.
authors.affiliation: Universitätsklinikum Rudolf Virchow Kinderklinik, Freie Universität Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Belz
authors.forename: C
authors.initials: C
authors.lastname: Frickel
authors.forename: C
authors.initials: C
authors.lastname: Wolfrom
authors.forename: H
authors.initials: H
authors.lastname: Nau
authors.forename: G
authors.initials: G
authors.lastname: Henze
mesh_terms: D002138:Calibration; D002648:Child; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005493:Folic Acid Antagonists / Q000097:blood* / Q000134:cerebrospinal fluid; D006801:Humans; D002955:Leucovorin / Q000097:blood* / Q000134:cerebrospinal fluid; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000097:blood* / Q000134:cerebrospinal fluid; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000097:blood / Q000134:cerebrospinal fluid; D013048:Specimen Handling; D013763:Tetrahydrofolates / Q000097:blood* / Q000134:cerebrospinal fluid
chemical_list: D005493:Folic Acid Antagonists; D013763:Tetrahydrofolates; D002955:Leucovorin; C005984:5-methyltetrahydrofolate; C011864:7-hydroxymethotrexate; D008727:Methotrexate