Validation of an efficient LC-microdialysis method for gemifloxacin quantitation in lung, kidney and liver of rats

A liquid chromatography method has been established for the reliable determination of unbound gemifloxacin concentrations in kidney, lung and liver microdialysates of rats. Microdialysis probes were inserted into tissues of rats, and then dialysates were collected at regular time intervals after intravenous administration of gemifloxacin (40 mg kg(-1)). A pilot study was performed to assess gemifloxacin penetration in lung, kidney and liver of rats. Gemifloxacin was separated on a C-18 column eluted using triethylamine solution (0.5%, v/v), adjusted to pH 3.0 +/- 0.1 with 85% phosphoric acid, methanol and acetonitrile (71:15:14, v/v/v) as mobile phase at a flow rate of 1.1 mL min(-1). The fluorescence detector was set at excitation and emission wavelengths of 344 nm and 399 nm, respectively. The limit of quantitation was found to be 50 ng mL(-1). Linearity was found to be over a concentration range of 50-2000 ng mL(-1). The intra-assay and inter-assay precision and accuracy values were determined from the analysis of six quality control samples. The results obtained at three concentration levels showed R.S.D. values lower than 6.06% and 4.10% for repeatability and intermediate precision, respectively. The accuracy (R.E.%) ranged from 90.0 to 106.5%. The chromatographic run time of each sample was performed in 9 mm. Drug stability in microdialysates was shown at room temperature for 8 h, after three freeze-thaw cycles, in freezer at -80 degrees C for 14 days, and in the autosampler after processing for 8 h. The relative recoveries determined by extraction efficiency (EE) and retrodialysis (RD) in vitro employing a flow rate of 1.5 mu Lmin(-1) were 29.24 +/- 3.67% and 23.67 +/- 3.31%, respectively. In vivo recoveries determined by RD in Wistar rats' kidney, lung and liver were 27.69 +/- 2.09%, 23.12 +/- 3.79% and 17.38 +/- 0.68%, respectively. The method was successfully applied to investigate tissue penetration of unbound gemifloxacin into the kidney, lung and liver of rats. (C) 2013 Elsevier B.V. All rights reserved.