Simultaneous determination of ifosfamide and its metabolite ifosforamide mustard in human plasma by high performance liquid chromatography

Because ifosforamide mustard (IFM) is the active alkylating metabolite of ifosfamide (IFO) it is of particular interest in the pharmacokinetic analysis of patients undergoing IFO treatment. This paper presents an assay for the simultaneous determination of IFM and IFO after derivatization with diethyldithiocarbamate (DDTC), subsequent liquid-liquid extraction of the plasma with acetonitrile (AcN) and using reversed phase high performance liquid chromatography (RP-HPLC) with ultra-violet (UV) detection at 276 nm. Structural confirmation of the analytes was accomplished using mass spectrometry (MS). Reaction conditions such as incubation duration, temperature, and concentration of derivatization agent were investigated; 30 min at 70°C with 100 mg/mL DDTC was optimal. The presented analytical method proved to be accurate, precise, and linear for IFM and IFO concentrations, ranging from 0.100-50.0 and 0.100-100 μg/mL, respectively, and with lower limits of quantitation of 0.100 μg/mL for both analytes. A typical patient pharmacokinetic profile is presented to demonstrate the applicability of the assay in clinical samples. The analytical method could be employed in high-throughput clinical analysis of IFM and IFO patient samples.