INTRODUCTION:

Cefixime (CEF) is an oral third generation cephalosporin antibiotic. Chemically it is (6R,7R)-7-{[2-(2-amino-1,3-thiazol-4-yl)-2-(carboxymethoxyimino)acetyl]amino}-3-ethenyl-8-oxo-5-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylic acid, clinically used in the treatment of susceptible infections including gonorrhoea, otitis media, pharyngitis, lower respiratory-tract infections such as bronchitis, and urinary-tract infections¹. Erdosteine (ERD) is a mucolytic agent, chemicaly, it is (+)-1S-(2-[N-3-(2-oxotetrahydrothienyl)aceta- mido)thioglycolic acid, a thiol derivative developed for the treatment of chronic obstructive bronchitis, including acute infective exacerbation of chronic bronchitis². Erdosteine contains two blocked sulfhydryl groups which are released following first-pass metabolism. The three active metabolites exhibit mucolytic and free radical scavenging activity. Erdosteine modulates mucus production and viscosity and increases mucociliary transport, thereby improving expectoration. It also exhibits inhibitory activity against the effects of free radicals produced by cigarette smoke. Clinical trial showed that combination therapy of 200 mg of CEF and 300 mg ERD significantly shows good effect when compared to either treatment alone.

The synthetic mixture of combination of both the drug were prepared in the ratio of 200: 300 (CEF: ERD) by using excipients like microcrystalline cellulose, Polyvinylpyrrolidone and magnesium stearate which required for tablet formulation.

Literature survey reveals that cefixime can be estimated by spectrophotometrically³, HPLC^4-8 and by HPTLC⁹ in bulk drugs and human plasma while Erdosteine is estimated by HPLC^10-11, HPTLC¹² and LC-MS/MS¹³.

However, no method has been reported for simultaneous estimation of Cefixime and Erdosteine in its combination. In the present investigation, two simple, rapid and accurate methods have been developed for simultaneous estimation of Cefixime and Erdosteine from their synthetic mixture.

Material and Methods:

A Shimadzu UV/Visible double beam spectrophotometer model 1700 was employed, with a pair of 10 mm quartz cells. Gift samples of CEF and ERD were obtained from Glenmark Pharmaceuticals Ltd, Nashik. The synthetic mixture containing CEF 200 mg and ERD 300 mg were prepared by using common excipients. Methanol (AR Grade) was used as solvent, procured from Universal Laboratories Private limited, Mumbai.

Procedure:

Standard stock solutions having 100 µg/ml of CEF and ERD were prepared by dissolving separately 10 mg of each drug in 100 ml methanol.

For the simultaneous equation method, appropriate dilutions of two drugs were prepared separately by using standard stock solutions and the same were scanned in the range of 400 nm to 200 nm to obtain overlain spectra. The absorbance maximum observed for CEF and ERD at 289.0 nm and at 235.0 nm, respectively. Thus for the estimation of CEF and ERD, the working wavelengths selected, were 289.0 nm and 235.0 nm (Fig 1).

Table 1: Assay and Recovery Studies of Cefixime and Erdosteine in Synthetic Mixture

Method	Label Claim (mg/tab)		*Amount Found (%)		*Standard Deviation		% Recovery*
Method	CEF	ERD	CEF	ERD	CEF	ERD	CEF	ERD
A	200	300	99.62	99.66	±0.7413	±0.6423	99.50±0.5748	99.77±0.4013
B	200	300	100.18	100.07	±0.5040	±0.4624	98.93±0.3765	99.46±0.6778

*denotes n = 6, average of six estimations.

Where, A – Simultaneous equation, B –Multicomponent analysis, CEF – Cefixime, ERD – Erdosteine.

Fig. I: Overlain Spectra of Cefixime and Erdosteine

Various dilutions were made of two drugs individually and same were scanned in the range of 400 nm to 200 nm. CEF and ERD showed linearity in the range of 10-50 µg/ml at their respective wavelengths. The absorptivity coefficients of each of the two drugs were calculated at 289.0 nm and 235.0 nm.

A set of two simultaneous equations using the absorptivity coefficient values A_{1 =} 22.51 × C₁ + 17.19 × C_{2 …} (I) and A_{2 =} 25.40 × C₁ + 3.45 × C_{2 …...}(II), where, C₁ and C₂ are concentrations of CEF and ERD respectively in g/l in the sample solution. A₁ and A₂ are absorbance’s of sample solution measured at 289.0 nm and at 235.0 nm of CEF and ERD respectively, The mixed standards of CEF and ERD were prepared in the ratio of concentration 200: 300 µg/ml and their absorbance were measured at selected wavelengths. The amounts of drug present in the mixed standard solution were obtained by using the above equation.

In the second method, multicomponent mode of the instrument was used which has inbuilt software to calculate the concentration of the individual component in a mixture. The sampling wavelengths selected for the estimation of CEF and ERD were 289.0 nm and 235.0 nm respectively. The concentrations of mixed standard solution were entered in multicomponent mode. The absorbance spectra of mixed standard and sample solutions were measured at selected wavelength (Fig. 2). The instrument processes the data and gives individual concentration of the two drugs present in sample solution directly.

The synthetic mixture of both drugs in combination was prepared in the ratio 200:300 (CEF:ERD) using most commonly used excipients like microcrystalline cellulose, Polyvinyl pyrrolidone, magnesium stearate. From this mixture the powder equivalent to 100 mg of CEF was weighed and transferred to a 100 ml volumetric flask and

Fig. 2: Multicomponent Analysis of Mixed Standards

the solution was then filtered through Whatman filter paper (No.41), subsequent dilutions were made to obtain 10 mg/ml and 15 mg/ml for CEF and ERD respectively, and analyzed by two methods as mentioned above. The analysis procedure was repeated six times. The results of analysis of synthetic mixture are given in Table-1.

Accuracy of the analysis was determined by performing recovery studies of CEF and ERD at 80%, 100% and 120% level as per ICH guidelines.

Result and Discussion:

The proposed methods for simultaneous estimation of CEF and ERD in sample solutions were found to be simple, accurate and reproducible. In simultaneous equation method, wavelengths selected for analysis were 289.0 nm (λmax of CEF) and 235.0 nm (λmax of ERD). In the second method, multi-component mode of the instrument was used which has inbuilt software to calculate the concentration of the individual component in a mixture. The sampling wavelengths selected for the estimation of CEF and ERD were 289.0 nm and 235.0 nm respectively. In both the methods linearity for detector response was observed in the concentration range of 10-50 µg/ml for both CEF and ERD. Absorptivity coefficient were calculated for both the drugs at selected wavelengths and substituted in equations for determining concentration of CEF and ERD. Percent estimation for CEF and ERD in synthetic mixure, by simultaneous equation method was found to be 99.62 ±0.7413 and 99.66 ±0.6423 respectively. Similarly percent estimation for CEF and ERD in synthetic mixure, by multi-component mode method was found to be 100.18 ±0.5040 and 100.07 ±0.4624 respectively. Standard deviation and coefficient of variance for six determinations of 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 ascertained by recovery studies. The percent recovery for CEF and ERD, by both the methods, was found in the range of 98.44% – 100.20%. The proposed method could be employed for routine quality control of Cefixime and Erdosteine in its combined dose formulation.

Acknowledgements:

Authors are very thankful to Dr. Avinash D. Deshpande, Director of Pharmacy, Pad. Dr. D.Y.Patil Institute of Pharmaceutical Sciences and Research, Pimpri, Pune, for providing necessary facilities and also to Glenmark Pharmaceuticals Pvt. Ltd, Nashik, for providing gift samples of Cefixime and Erdosteine, to carry out this work.

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Received on 14.06.2009 Modified on 12.07.2009

Research J. Pharm. and Tech.2 (3): July-Sept. 2009,;Page 582-584