Determination of sitafloxacin in human plasma by liquid chromatography–tandem mass spectrometry method: Application to a pharmacokinetic study

• An LC–MS/MS method has been developed for determining sitafloxacin in human plasma.
• The method has some merits: high sensitivity, small sample volume and short runtime.
• It is successfully applied to the pharmacokinetic study of sitafloxacin in human.

A high-performance liquid chromatographic–tandem mass spectrometric (HPLC–MS/MS) method was developed and validated to determine sitafloxacin in human plasma with dextrorphan as internal standard. Chromatographic separation was performed on a ZORBAX SB-C18 column (3.5 μm, 2.1 mm × 100 mm) with the mobile phase of methanol/water (containing 0.1% formic acid) (46:54, v/v) at a flow rate of 0.2 mL/min. Quantification was performed using multiple-reaction monitoring of the transitions at m/z 410.2 ⟶ 392.2 for sitafloxacin and m/z 258.1 ⟶ 157.1 for dextrorphan, respectively. The calibration curve was linear over the range of 5–2500 ng/mL with the lower limit of quantification of 5 ng/mL for sitafloxacin. The intra- and inter-day precisions were less than 8.3% and the deviations of assay accuracies were within ±4.1%. Sitafloxacin was sufficiently stable under all relevant analytical conditions. This method was successfully applied to the pharmacokinetic study of sitafloxacin in healthy Chinese volunteers.