Visible Spectrophotometric Methods For Estimation Of Repaglinide In Pharmaceutical Formulation

A. Goyal * and I. Singhvi **  

^* B. N. P.G. College of Pharmacy, Udaipur (Raj.) 313002

** Department of Pharmaceutical Sciences, M. L. Sukhadia University, Udaipur
(Raj.) 313001

* For correspondence :Mailing Address: 277,Sector
11, Hiran Magari, Udaipur(Raj.), 313001.Telephone No. : 02942584851, Mobile:
09828135201,e-mail-goyalanjugoyal@yahoo.com

Abstract:

Two simple, economical, precise, convenient and reproducible visible
spectrophotometric methods have been developed for the estimation of repaglinide
in tablet formulation. The developed methods are based on the formation of chloroform
extractable complex of repaglinide with chlorophenol red and bromophenol blue
in acidic medium. The extracted complex with chlorophenol red shows absorbance
maxima at 406.4 nm and the extracted complex with bromophenol blue shows absorbance
maxima  at  407.0 nm.   Both  the   developed 
methods  show   linearity   in   the  
concentration  range 10-50 mg/ml. Results of analysis for both the methods
were validated statistically and by recovery studies.

Key Words:  Colorimetry, Repaglinide,Tablet Formulation.

Introduction:

Repaglinide, chemically, (S)-2-Ethoxy-4- [2-[[3-methyl-1-[2-(1-piperidinyl)phenyl] butyl] amino]-2-oxoethyl] benzoic acid, is a new nonsulphonyl urea oral  hypoglycemic drug¹. It is used in the treatment of type-2 diabetes mellitus². It is official in USP³  which describes liquid chromatographic method for its quantitation. Literature survey reveals HPLC^4-6 methods for the estimation of repaglinide from plasma and pharmaceutical formulation.

The objective of the present investigations was to develop simple, accurate and economical visible  spectrophotometric methods for estimation of repaglinide in tablet formulation.

Materials and Methods:

Instrument:

Thermospectronic UV1, UV/Vis double beam spectrophotometer with spectral bandwidth of 2 nm, wavelength accuracy of  ± 0.5 and 1 cm matched quartz cells was used for analytical method development.

Chemicals:

All the chemicals and reagents used were of analytical grade.  Chlorophenol red (CDH) reagent was prepared in acid phthalate buffer of pH 2.0 and bromophenol blue (Thomas Baker) reagent was prepared in acid phthalate buffer of pH 4.0.  Both the reagents were prepared in double distilled water and extracted several times with chloroform so as to remove chloroform soluble impurities. Tablet formulation of repaglinide (Torrent) was procured from local market. Standard solution of repaglinide was prepared by  dissolving 10 mg  in  100 ml  of chloroform  to   give  stock solution of concentration

100 mg/ml of drug.

Preparation of standard stock solution:

In   a  series of 10 ml   volumetric   flasks, aliquots of  standard drug  solution  (100 mg/ml) in chloroform were transferred and diluted with same so as to give several dilutions in concentration range of 10-50 mg/ml of repaglinide. To 5 ml of each dilution taken in a separating funnel, 5 ml of chlorophenol red reagent (For method I) and 5 ml of bromophenol blue reagent (For method II) was added. Reaction mixture was shaken gently for 5 min and allowed to stand for 5 min so as to separate aqueous and chloroform layer. The chloroform layer was separated out and absorbance maxima measured at 406.4 nm (For method I) and at 407.0 nm (For method II) against a respective reagent blank. Calibration curve was plotted between concentration of repaglinide and respective measured absorbance.

For analysis of tablet formulation, forty tablets (0.5 mg and 1.0 mg) of repaglinide were weighed accurately  and  finely  powdered.  An  accurately  weighed  portion of powdered sample, equivalent to

10 mg of repaglinide was taken in a 100 ml volumetric flask containing 40 ml of chloroform, sonicated for 20 minutes. The resultant was filtered through whatman filter paper No. 41 into another 100 ml volumetric flask. The filter paper was washed several times with chloroform. The washings were added to the filtrate and the final volume was made up to the mark with chloroform.

For both the methods, filtrate (3 ml) of the sample solution   was diluted   to 10 ml with chloroform and treated as per the procedure of the respective calibration curve. Amount of the drug present in sample was computed from respective calibration curve.

The procedure of analysis from tablet formulation for both the methods was repeated five times with two different strengths of tablet formulation. Results of analysis are reported in Table 1.

Recovery studies were carried out for both the methods by the addition of known amount of standard drug solution of repaglinide to pre-analyzed tablet sample solution at three different concentration level. The resulting solutions were analyzed by proposed methods. The results of recovery studies were found to be satisfactory and are reported in Table 1.

Results and Discussion:

These proposed methods were found to be simple, accurate, economical and rapid. Recovery studies were found close to 100 percent that indicates accuracy and precision of the proposed methods. Statistical analysis was carried out and the results of which were satisfactory.  Beer’s law was obeyed in the concentration range of 10-50 mg/ml, value of correlation coefficient was found to be 0.9989 for method I and 0.9996 for method II.  Standard deviation and relative standard deviation values were statistically low indicating reproducibility of the proposed methods. It was observed that excipients did not interfere in the determination of repaglinide. Hence these developed methods could be used for routine estimation of repaglinide in its tablet dosage forms.

Acknowledgement:

The authors are thankful to Torrent Laboratories Pvt. Ltd., Ahmedabad, for providing gift sample of repaglinide.

References:

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2)Martindale, The Complete Drug Reference, Pharmaceutical Press, 33rd
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3)United State Pharmacopoeia, USP Convention Inc., Rockville M.D., Asian
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4)Greischel, A., Beschke, K., Rapp, H. and Roth, W., Quantitation of the new
hypoglycaemic agent AG-EE 388 ZW in human plasma by automated HPLC with electrochemical
detection,  J. Chromatogr., 1991, 568(1), 246-52.

5)Gandhimathi, M., Ravi, T. K. and Renu, S.K.,  Determination of Repaglinide
in Pharmaceutical Formulations by HPLC with UV Detection, Anal. Sci.,
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6)Krishna Reddy, K.V.S.R., MosesBabu, J., Mathad, V.T., Eswaraiah, S., Reddy,
S.  M., Dubey, P.K. and Vyas, K., Impurity Profile Study of Repaglinide,
J. Pharm. Biomed. Anal., 2003,   32 (3), 461-467.       

                  
Table 1:  Results of Analysis and Recovery Studies

 * Average of five determinations

 ** Average of recovery studies at three different concentration levels