High-performance liquid chromatographic determination of methotrexate, 7-hydroxymethotrexate, 5-methyltetrahydrofolic acid and folinic acid in serum and cerebrospinal fluid.

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.

[Severe renal impairment of methotrexate elimination after high dose therapy]. / Schwere renale Methotrexat-Ausscheidungsstörung nach Hochdosis-Therapie.

Even in patients with normal renal function, high-dose methotrexate therapy (HDMTX) may be followed by extremely prolonged MTX elimination through alkaline diuresis is performed correctly. By inquiry in Germany, Austria and Switzerland for HDMTX infusions with MTX plasma concentration 42 h after start of exposure (MTX-42) higher than 5 mumol/l (microM), we analyzed data from 21 patients in whom impairment of renal methotrexate elimination had received 5 g/m2.24h, 3 had received 12 g/m2.4h. They presented with MTX-48 serum level between 1.7 and 1404 microM. There was no recognizable causative factor. As early signs for impaired elimination, we identified enhanced vomiting during MTX infusion in 8/21, elevated steady-state-MTX in 11/15, and a rise of serum creatinine greater than 50% in 14/16 patients in whom respective data were available. Creatinine rose to a maximum of 1.0-4.9 mg/dl within 1-4 days in 19/21 patients (accompanied by diuresis problems in only 5 patients) and normalized within 3-17 days in all but two patients. Creatinine maximum correlated weakly with MTX-48 (r = 0.34) and with extrarenal toxicity. 8 patients had normal (WHO 0-II degree), 8 other had intensified (III-IV degrees) but not critical extrarenal MTX toxicity with calcium folinate (CF) doses of 0.2-1.6 mg/kg.microM MTX q 6 h started 28-54 h after beginning of MTX exposure. 5 patients had unusual toxicity. 2 patients suffered from severe but reversible encephalopathies with CF doses of 0.05 and 1 mg/kg.microM MTX q 6 h started after 51 and 36 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)