Simultaneous determination of zidovudine and its monophosphate in mouse plasma and peripheral red blood cells by high-performance liquid chromatography

Novel prodrugs for the intracellular delivery of zidovudine monophosphate ( AZTMP) have recently been designed. To investigate the bioconversion and ph armacokinetic profiles of these compounds, an analytical method for the sim ultaneous determination of zidovudine (AZT) and AZTMP in mouse plasma and p eripheral red blood cells was developed. Mouse whole blood samples were tre ated with TBAHS, EDTA and NaH2PO4, and separated into plasma and red blood cell portions. Samples were processed by solid-phase extraction using Bond Elut C-18 cartridges. Chromatography was performed using an Hypersil ODS co lumn and a mobile phase of 2.9% (v/v) acetonitrile and 97.1% (v/v) phosphat e buffer, pH 7.50, with UV detection at 267 nm. The average extraction reco veries of AZTMP and AZT in plasma were approximately 85% and 97% over their linear ranges of 0.05-5 mu g/ml and 0.125-25 mu g/ml, respectively. Extrac tion recoveries of AZTMP and AZT from peripheral red blood cells averaged 5 6 and 69% over their linear ranges of 0.125-5 mu g/ml and 0.125-25 mu g/ml, respectively. The accuracy of the assay was 90-100%. The intra- and inter- day variations of the assay were less than 14%. The analytical method was f ound to be applicable, reliable and suitable for pharmacokinetic studies. ( C) 2000 Elsevier Science B.V. All rights reserved.