HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF STABILIZED 4-HYDROXYIFOSFAMIDE IN HUMAN PLASMA AND ERYTHROCYTES

A method using reversed-phase high-performance liquid chromatography ( RP-HPLC) is described for the measurement of the stabilized activated metabolite of ifosfamide, 4-hydroxyifosfamide (4-OHIF), in human plasm a and erythrocytes. Immediately after sample collection and plasma-ery throcyte separation at 4 degrees C, 4-OHIF was stabilized by derivatiz ation with semicarbazide (SCZ). The sample pretreatment involved liqui d-liquid extraction with ethyl acetate. RP-HPLC was executed with a C- 8 column and acetonitrile-0.025 M potassium dihydrogenphosphate buffer (pH 7.40)-triethylamine (13.5:86:0.5, v/v) as mobile phase. The analy te was determined with UV detection at 230 nm. Complete validation, op timisation and stability studies were performed and the method proved to be specific, sensitive and with a stable analyte in the range of cl inically relevant concentrations (0.1-10 mu g/ml) after conventional d osing. The lower limit of quantitation was 100 ng/ml using 1.00 ml of sample. Accuracy was between 94.1 and 107.0%. Within-day and between-d ay precisions were less than 6.2% and 7.2%, respectively. 4-OHIF-SCZ w as found to be stable in the biological matrix at -20 degrees C for at least 1 month. A pharmacokinetic study conducted in a patient receivi ng 9 g/m(2) over 3 days by means of a continuous infusion, demonstrate d the applicability of this method. (C) 1998 Elsevier Science B.V. All rights reserved.