Simultaneous determination of etoposide and its catechol metabolite in theplasma of pediatric patients by liquid chromatography/tandem mass spectrometry

The anticancer drug etoposide is associated with leukemias with MLL gene tr anslocations and other translocations as a treatment complication. The geno type of cytochrome P450 3A4 (CYP3A4), which converts etoposide to its catec hol metabolite, influences the risk. In order to perform pharmacokinetic st udies aimed at further elucidation of the translocation mechanism, we have developed and validated a liquid chromatography/electrospray/tandem mass sp ectrometry assay for the simultaneous analysis of etoposide and its catecho l metabolite in human plasma. The etoposide analog teniposide was used as t he internal standard. Liquid chromatography was performed on a YMC ODS-AQ c olumn. Simultaneous determination of etoposide and its catechol metabolite was achieved using a small volume of plasma, so that the method is suitable for pediatric patients. The limits of detection were 200 ng ml(-1) etoposi de and 10 ng ml(-1) catechol metabolite in human plasma and 25 ng ml(-1) et oposide and 2.5 ng ml-1 catechol metabolite in protein-free plasma, respect ively. Acceptable precision and accuracy were obtained for concentrations i n the calibration curve ranges 0.2-100 mug ml(-1) etoposide and 10-5000 ng ml(-1) catechol metabolite in human plasma. Acceptable precision and accura cy for protein-free human plasma in the range 25-15000 ng ml(-1) etoposide and 2.5-1500 ng ml(-1) etoposide catechol were also achieved. This method w as selective and sensitive enough for the simultaneous quantitation of etop oside and its catechol as a total and protein-free fraction in small plasma volumes from pediatric cancer patients receiving etoposide chemotherapy. A pharmacokinetic model has been developed for future studies in large popul ations. Copyright (C) 2001 John Wiley & Sons, Ltd.