INTRODUCTION:

Cefixime (CEFI) (6R, 7R)-7-[2-(2-amino-4- thiazolyl) glyoxylamido]-8-oxo-3-vinyl-5-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid,7-9z)-[o-carboxymethyl)-oxime] trihydrates is third generation cephalosporin antibiotic¹. Ofloxacin (OFLO)chemically 9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-piperazinyl)-7-oxo-7H-pyrido(1,2,3-di)-1,4-benzoxazine carboxylic acid used as an antibacterial and clinically used in the treatment of susceptible infections including gonorrhea, otitis media, bronchitis, urinary tract infections².Literature survey reveals cefixime and ofloxacin estimated by high performance liquid chromatographic (HPLC) in tablet dosage form^3,5. Spectrophotometric method for simultaneous estimation of cefixime with other drugs also reported⁶ . spectrophotometric method for simultaneous estimation of ofloxacin with other drugs also reported⁷. No report was found for the simultaneous estimation of cefixime and ofloxacin in bulk and tablet dosage form by spectrophotometric method. Present work describes a simple, accurate, rapid and economical methods for simultaneous estimation of cefixime and ofloxacin in bulk and in combined tablet dosage forms.

MATERIAL AND METHODS:

Reagents and Chemicals:

Ethanol (AR Grade) was used as solvent, procured from Universal Laboratories private limited, Mumbai. Pure Standard gift sample of cefixime provided by Glen mark pharmaceutical Ltd, and Ofloxacin by Aristo Pharmaceuticals Pvt. Ltd, Mumbai. Combined dose of cefixime and ofloxacin tablets (label claim 200mg) were purchased from local market.

Instrumentation:

A double-beam Elico UV-visible spectrophotometer, with spectral bandwidth of 0.2nm, wavelength accuracy ± 0.1 nm and a pair of 1 cm matched quarts cells were used to measure absorbance of the resulting solution.

Preparation of standard stock solution:

Standard stock solutions of cefixime (100μg/ml) and ofloxacin (40µg/ml) were prepared in ethanol and used for the analysis.

Methods:

Method A: Simultaneous Equation Method

Simultaneous equations method based on measurements at two wavelengths. Two dissimilar chromophores must necessary have different powers of light absorption at some points or in linear absorption.

A set of two simultaneous equations obtained by using mean absorptivity values are given below

A₂ ay₁-A₁ay₂

C_X= --------------------- -------------------- (1)

ax₂ ay₁-ax₁ay₂

A₂ ay₁-A₁ay₂

C_Y= --------------------- ---------------------- (2)

ax₂ ay₁-ax₁ay₂

Where, A1 and A2 are absorbance of the sample at 290.4nm and 297.4 nm respectively, ax₂_, ax_1
=denote absorptivities of X at 290.4 nm and 297.4nm respectively, ay₁,ay_2
=denote absorptivities of Y at 290.4 nm and 297.4nm respectively, CX = concentration of cefexime; CY = concentration of ofloxacin.

Method B. Absorbance Ratio Method:

It depends on the property that, for a substance which obey Beers law at all wavelengths is constant value independent of concentration or path length.

From the following set of equations the concentration of each component in sample can be alculated.

For Cefixime:

Qm – Qy A1

Cx = -------------- X ----- ---------------------- (3)

Q x – Qy a

For Ofloxacin:

Qm – Qx A1

CY= ------------- X ------ ---------------------- (4)

Qy – Qx a

Where, Cx = Concentration of Cefixime, CY = Concentration of Ofloxacin, A1 = Absobance of sample at iso-absorptive wavelength 282.0 nm, a = Mean absorptivity of CEFI and OFLO at iso-absorptive 282.0 nm,

Absorbance of sample solution at290.4nm

Qm = ____________________________________

Absorbance of sample solution at 282.0 nm

Absorptivity of Cefixime at290.4 nm

Qx = ____________________________________

Absorptivity of Cefixime at 282.0 nm

Absorptivity of Ofloxacin at 297.4 nm

Qy = ____________________________________

Absorptivity of Ofloxacin at 282.0 nm

Spectral characteristics of CEFI and OFLO:

Solutions of CEFI and OFLO (10 μg/ml, each), were prepared separately by appropriate dilution of standard stock solution. Both the solutions were scanned in the spectrum mode from 400 nm to 200 nm. Overlay absorption spectra were recorded (Fig. 1).

Preparation of calibration curves

Appropriate dilutions of the standard stock solution were done separately to get 5,10,15,20, and 25 μg/ml of CEFI and 2, 4, 6, 8, and 10μg/ml of OFLO. The absorption spectra of all solutions were recorded between 200-400 nm. The absorbances were measured at 290.4 nm (λmax of CEFI) 297.4 nm (λmax of OFLO) and 282.0 nm (iso-absorptive point).Beer’s lamberts range for CEFI and OFLO were selected and working calibration curves of both the drugs were plotted separately.

Determination of Absorptivity Value of CEFI and OFLO:

Appropriate dilutions of the standard stock solution were done to get 10 μg/ml of each CEFI and OFLO, respectively. The absorbances were measured for CEFI and OFLO at 290.4 nm (λmax of CEFI), 297.4 nm (λmax of OFLO) and 282.0 nm (iso-absorptive point). The absorptivity values of the drugs were determined at the selected wavelengths.

Assay of tablet formulation:

Twenty tablets were weighed and average weight was calculated. The tablets were crushed to obtain fine powder. Tablet powder equivalent to 100 mg of CEFI was transferred to 100.0 ml volumetric flask, ethanol added, ultrasonicated for 10 minutes and volume was made-up to the mark with ethanol. The solution was then filtered through a Whatman filter paper (No. 41). The filtrate was further diluted with ethanol to obtain 10 μg/ml of CEFI and 10 μg/ml of OFLO. The concentration of both CEFI and OFLO were determined by measuring the absorbance of the sample at 290.4 nm, 297.4 nm Calculated using (method A, simultaneous equation method) and (method B, absorbance ratio method). Concentration of sample solution was determined by using above equations1, 2,3 and 4.The results are reported in the Table 1.

RESULTS AND DISCUSSION:

The present method could be provided a convenient and accurate method for simultaneous analysis of CEFI and OFLO. In simultaneous equation method, wavelengths selected for analysis were 290.4nm (λmax of Cefixime) and 297.4 nm (λmax of Ofloxacin). In both the methods linearity for detector response was observed in the concentration range of 5-25 μg/ml for CEFI and 2-10 μg/ml for OFLO. Absorptivity coefficient were calculated for both the drugs at selected wavelengths and substituted in equations for determining concentration of CEFI and OFLO in tablet sample solution. Percent label claim for CEF and OFLO in tablet analysis, by both the method was found in the range of 98.54 % to 100.5%. Standard deviation and coefficient of variance for six determinations of tablet sample, by both the methods, was found to be less than ± 2.0 indicating the precision of both the methods. Accuracy of proposed methods was determined by recovery studies. The percent recovery for CEFI and OFLO, the methods was found in the range of 98.19 % – 100.45 %. The developed method could be employed for routine analysis of Cefixime and Ofloxacin in combined dose tablet formulation.

ablet Analysis and Recovery Studies of Cefixime and Ofloxacin

Method	Label Claim (mg/tab)		Amount Found (%)		Standard Deviation		% Recovery
Method	CEFI	OFLO	CEFI	OFLO	CEFI	OFLO	CEFI	OFLO
A	200	200	100.5	94.8	±0.33419	±0.2494	100.9±0.1647	95.2±0.1452
B	200	200	98.4	95.8	±0.2487	±0.1984	99.8±.6428	97.7±0.1587

Fig.-1: Overlain Spectra of Cefixime (CEFI) and Ofloxacin (OFLO)

ACKNOWLEDGEMENTS:

The authors are grateful to RVS College of Pharmaceutical Sciences, Coimbatore for providing necessary facilities.

REFERENCES:

1. WWW.Wikipedia.org/Wiki/Cefixime

2. Sweet man S.C., Martindale. The complete Drug Reference. 32nd Edn. Pharmaceutical press.

3. WWW.Wikipedia.org/Wiki/ofloxacin

4. Zendelovska D.,Stafilov T., Milosevski P.“High performance liquid chromatographic method for determination of cefixime and cefotaxime in human plasma”. Bulletin of the chemists and Technologists of Macedonia.2003;22: 39-45.

5. Rathinavel G., Mukherjee P. B., Valarmathy J., Samueljoshua L., Sivakumar T. “A Validated RP – HPLC method for simultaneous estimation of cefixime and cloxacillin in tablets” Journal of chemistry.2008; 5: 648-651.

6. Jovanovic E. S., Agbaba D. Zivanov‐Stakic S. “HPTLC determination of csftriaxone;cefixime and cefotaxime in dosage forms” J. Pharm. Biomed. Anal. 1998; 18: 893‐898.

7. Senthilraja M. “Simultaneous UV spectrophotometric method for estimation of nitazoxanide and ofloxacin in combined dosage form”. Int. J. Pharm. Tech. 2008; 1: 469-471.

Received on 29.06.2011 Accepted on 30.06.2011

Asian J. Pharm. Ana. 1(2): April-June 2011; Page 36-38