Modification of a Previously Published HPLC-UV Method for Metformin Determination, Validation and Application to Test Bioequivalence

The aims were to overcome the problem of peak deterioration caused by HCl used in a sample preparation andvalidate and apply the modified method to test the bioequivalence of Glystor (Algorithm S.A.L., Lebanon) andGlucophage® (Merck Santé S.A.S., France) tablets. Non-acidified samples were prepared by protein precipitationfollowed by washing with dichloromethane. The mobile phase consisted of acetonitrile and phosphate buffer(65:35) pH 7.5. A Hypersil silica column was used. The method was validated according to the FDA guidanceand applied to test bioequivalence. No deterioration in the peak shape was observed. Only two columns wereused during validation and analysis. Good separation of atenolol and metformin was achieved. Calibrationcurves (40-2000 ng/ml) were linear. Accuracy and precisions were within required limits. Absolute recoverieswere 78.30%. Metformin was stable in stock solution and in plasma during processing and storage. Statisticalanalysis of pharmacokinetic parameters demonstrated bioequivalence. In conclusion, the modified method wasfunctional and the two products were bioequivalent