Determination of gemifloxacin in different tissues of rat after oral dosing of gemifloxacin mesylate by LC-MS/MS and its application in drug tissue distribution study.

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to evaluate the accumulation of gemifloxacin in different tissues of Wister albino rat. The analytical method consists of the homogenization of tissues followed by simple liquid-liquid extraction and determination of gemifloxacin by an LC-MS/MS. The analyte was separated on a Peerless basic C(18) column (33 mm x 4.6 mm, 3 microm) with an isocratic mobile phase of methanol-water containing formic acid (1.0%, v/v) (9:1, v/v) at a flow rate of 0.6 ml/min. The MS/MS detection was carried out by monitoring the fragmentation of m/z 390.100-->372.100 for gemifloxacin and m/z 332.100-->314.200 for ciprofloxacin (internal standard; IS) on a triple quadrupole mass spectrometer. The validated method was accurate, precise and rugged with good linearity in all tissue homogenates. The accuracy and precision value obtained from six different sets of quality control samples of all tissues and serum analyzed in separate occasions within 91.833-102.283% and 0.897-5.291%, respectively. The method has been successfully applied to tissue distribution studies of gemifloxacin. The present study demonstrates that the highest tissue concentration of gemifloxacin was obtained in lung (11.891 ng/g), followed by liver (10.110 ng/g), kidney (10.095 ng/g), heart (4.251 ng/g), testis (3.750 ng/g), stomach (3.182 ng/g), adipose tissue (1.116 ng/g) and brain (0.982 ng/ml) in 3h after multiple oral dosing of 200mg gemifloxacin mesylate for 7 days. This method may also be used for gemifloxacin tissue distribution modeling study in rat tissues and antibiotic residue analyses in other animal tissues.