title: Enzymatic assay for methotrexate in erythrocytes.
abstract: Methotrexate (MTX) accumulates in erythrocytes in MTX-treated patients. We present a modified enzymatic assay measuring MTX concentrations between 10 and 60 nmol/l in erythrocytes, adapted for a centrifugal analyser (Cobas Bio). About 40 patient's samples could be analysed within 1 h. The detection limit was 3 nmol/l. Within run and between-run precision was 7.4% and 13.5% for control 10 nmol/l and 1.2% and 3.2% for control 50 nmol/l. Recovery was 85-115% of MTX added to haemolysed erythrocytes. We found the method useful for pharmacokinetic studies of MTX in erythrocytes in MTX-treated patients.
mesh_terms: D002498:Centrifugation; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007202:Indicators and Reagents; D008722:Methods; D008727:Methotrexate / Q000097:blood*; D013762:Tetrahydrofolate Dehydrogenase
chemical_list: D007202:Indicators and Reagents; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate