A highly selective, sensitive and rapid hydrophilic liquid interaction chromatographic method was developed and validated for determination of gemifloxacin on dried blood spots. The chromatographic separation was achieved on a reversed-phase zwitterionic hydrophilic interaction liquid chromatographic ZIC®HILIC-C₁₈ (4.6 × 100 mm; 5 µm) column using acetonitrile-10 mM ammonium acetate (pH 3.5; 80:20, v/v) as a mobile phase in an isocratic elution mode at a flow rate 0.6 mL/min at 27 °C. An on-line fluorescence detector set at excitation and emission wavelengths of 269 and 393 nm, respectively was used for monitoring column eluents. Ciprofloxacin was used as an internal standard. The method was validated for accuracy, precision, linearity and selectivity by design of experiments following ICH guidelines. The assay exhibited a linear range of 25-5000 ng/mL for gemifloxacin on dried blood spots. The lower limit of detection was found to be 10 ng/mL. The intra- and inter-assay coefficients of variation did not exceed 7.4% deviation of the nominal concentration. The recovery of GFX from dried blood spots was >95.0% and its stability was excellent with no evidence of degradation during sample processing for at least 3 months storage in a freezer at -20 °C.

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A validated stability indicating RP-HPLC assay of gemifloxacin mesylate was developed by separating its related substances on an Inertsil-ODS3V-C18 (4.6 × 250 mm; 5 μm) column using 0.1% trifluoroaceticacid (pH 2.5) and methanol as a mobile phase in a gradient elution mode at a flow rate of 1.0 mL/min at 27°C. The column effluents were monitored by a photodiode array detector set at 287 nm. The method was validated in terms of accuracy, precision and linearity as per ICH guidelines. Forced degradation of gemifloxacin (GFX) was carried out under acidic, basic, thermal, photolysis and peroxide conditions and the degradation products were separated and characterized by ESI-MS/MS, (1) H and (13) C NMR spectroscopy. The method was successfully applied to the analysis of bulk drugs and the recoveries of gemifloxacin and impurities were in the range of 97.60-102.90 and 96.99-102.10%, respectively. No previous reports were found in the literature on identification of degradation products of gemifloxacin.

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Stereochemistry in drug action is gaining importance because the enantiomers often differ in their biological activity and pharmacokinetic profiles. The use of racemic drugs may contribute to adverse effects owing to the presence of either inactive or toxic enantiomers. Most of the drugs currently used to treat psychiatric disorders, including depression, contain one or more chiral centers and are mostly sold as racemates. Single-enantiomer drugs provide greater selectivity for their biological targets, improved therapeutic indices and better pharmacokinetics compared with racemates. Therefore it is of great importance to monitor body fluid/tissue levels of drugs used to treat depression and psychiatric disorders. The present manuscript gives an overview of liquid chromatographic and mass spectrometric techniques reported during 2000-2013 for enantiomeric separation of various classes of antidepressants, viz. selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, noradrenergic and specific serotonergic antidepressants, norepinephrine reuptake inhibitors, norepinephrine-dopamine reuptake inhibitors, nonamphetamine central nervous system stimulants, serotonin and dopamine inhibitors and γ-aminobutyric acid receptor agonists in biological matrices. Techniques used for extraction, separation and quantification are discussed.