Introduction

Gemifloxacin mesylate is a third group of fluoroquinolone active against s.pneumonia.  It is useful in treatment of chronic bronchitis and mild to moderate pneumonia.  It is chemically, (R,S)-7-[4z-3-(amino methyl)-4-(methoxy imino)-1-pyrrolidinyl]-1-cyclopropyl-6-fluoro-1, 4 dihydro-4-oxo-1, 8- naphthyridine-3-carboxylic acid¹.  A through survey of literature revealed only LCMS was reported for the determination of Gemifloxacin mesylate in human plasma². The analytically useful function groups of Gemifloxacin mesylate have not been fully exploited.  The authors have made some attempts in this direction and succeeded in developing this spectrophotometric method for the assay.  Method is based on reaction of Gemifloxacin mesylate with Fe³⁺ and 0.1 M hydrochloric acid to produce orange chromogen (l_max at 471nm).

Meterial and Methods

Instrumentation

Spectral and absorbance measurements were made with Shimadzu UV-Visible Double beam spectrophotometer model-1700 with pair of 10 mm quartz cell.

Reagents

All the chemicals used were of analytical grade. Pure raw material of Gemifloxacin mesylate was obtained as a gift sample from Orchid Pharmaceuticals, Chennai. The formulations  used were purchased from local pharmacy.   All the solutions were freshly prepared with double distilled water. Freshly prepared solutions were always used 1%w/v ferric nitrate reagent was prepared by dissolving 1gm of ferric nitrate in 100ml of  3M nitric acid.

Standard and Sample solution of Gemifloxacin mesylate

About 100mg of Gemifloxacin mesylate (bulk and formulations) was accurately weighed and dissolved in 100ml of 0.1M hydrochloric acid in a volumetric flask to make a solution of 1 mg/ml standard solution and further dilutions are made with the same solvent.

Assay procedure

Aliquots 1 to 5 ml of standard Gemifloxacin mesylate  (100mg/ml) was transferred to a series of 10ml volumetric flask.  Each 10ml volumetric flask, added 0.6ml of 1%w/v ferric nitrate reagent solution and made up to the mark with 0.1M hydrochloric acid and kept aside for few minutes. The absorbance of the orange colour chromogen was measured at 471nm against the reagent blank.  The amount of Gemifloxacin mesylate was computed from the calibration curve.

Results and Discussion

The proposed method was based on redox reaction in which Gemifloxacin mesylate is oxidized by ferric nitrate.  The same method was already reported for the gatifloxacin, which is a analogue of the our drug.  The optical characteristics such as absorption maxima, beer’s law limit, molar absorptivity and sandell’s sensitivity for this method were presented in Table -1.  The regression analysis using the method of least squares was made for the slope (a), intercept (b) and correlation coefficient (r) obtained from different concentrations was summarized in Table -1.

Table 1: Optical characteristics of Gemifloxacin mesylate.

*Y = mx+c, where ‘Y’ is the absorbance and c is the

concentration of Gemifloxacin mesylate in mg/ml

** For six replicates

The accuracy of this method was ascertained by comparing the results obtained with the proposed method in the case of formulations and is presented in Table 2.  As an additional check on the accuracy of this method, adding known amounts of pure drug to pre-anaylzed formulations.  Performed recovery experiment and percent recovery values obtained are listed in Table 2.  Recovery experiment indicated the absence of interferences from the commonly encountered pharmaceutical additives and excipients.

Table 2: Assay and recovery studies of Gemifloxacin mesylate in Pharmaceutical formulations.

* mean of three estimation at each levels

Thus, the proposed method is simple and sensitive with reasonable precision and accuracy.  This can be used for the routine determination of Gemifloxacin mesylate in quality control analysis.

Acknowledgement

The authors are grateful to Management, Adhiparasakthi College of Pharmacy, Melmaruvathur for their continuous support and encouragement and for providing the necessary facilities.  They also thankful to Orchid Pharmaceuticals, Chennai for the gift sample of Gemifloxacin mesylate.

References

1. Sweetman, S. C., Martindale; The Complete Drug Reference. 35^th edn. Pharm. Press, London, 251 (2007).
2. Doyle, E., Fowles, S.E, Ncdinnell, D.F, Mc Carthy, R. and White, S.A. “Rapid determination of gemifloxacin in human plasma by high-performance liquid chromatography-tandem mass spectrometry”. J Chromatogr Biomed Sci, 15:191-8 (2000).