Determination of 7-hydroxymethotrexate in human plasma by reversed phase high-performance liquid chromatography.

A rapid and sensitive reversed phase HPLC method was developed for the detection of 7-hydroxymethotrexate (7-OHMTX) which is the main metabolite in human plasma after high-dose methotrexate (MTX) therapy. The simple clean-up procedure of plasma samples described allows the measurement of 7-OHMTX during clinical management of MTX infusions. Elimination kinetics of 7-OHMTX are given from 53 drug cycles of 6 patients.