Simultaneous quantification of antofloxacin and its major metabolite in human urine by HPLC-MS/MS, and its application to a pharmacokinetic study.

This study presents a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the simultaneous determination of antofloxacinin and its main metabolite - N-demethylated metabolite (N-DM) - in human urine. Ornidazole was used as the internal standard. This was a clinical urine recovery study, in which 10 healthy Chinese volunteers were intravenously administered a single 200 mg dose of antofloxacin hydrochloride. Compounds were extracted by albumen precipitation, after which samples were isocratically eluted using a Poroshell 120 SB-C18 column, and were analysed using HPLC-MS/MS under electronic spray ionization positive ion mode. The method was successfully applied in a urine pharmacokinetic study of antofloxacinin, with a detection range of 0.02/0.01 to 200/100 μg/mL (for antofioxacin/N-DM).The average percentages of antofioxacin/N-DM measured in urinary excretion frp, 10 volunteers were 54.9 ± 5.7/8.2 ± 2.5% in 120 h duration.