Aim of the present investigation was to study the effect of combination of hydrophilic polymer polyethylene oxide (PEO) and Gellan gum on extended release behavior of Metformin hydrochloride using full factorial design. Extended release matrix tablets were prepared by wet granulation technique. A 32 full factorial design were applied to carry out systematic studies. Content of PEO (X1) and content of Gellan gum (X2) were selected as independent variables. The percent drug release at 1 h (Q1), time required for 50% (t50) and 80% (t80) drug release were selected as dependent variables. Optimization studies were carried out by using the Design Expert software (version 8.0.1). The release data were subjected to various release kinetic models and also compared with those of a commercial brand. The physicochemical characteristics of all the granules and tablets were satisfactory. The values of dependent factors Q1, t50 and t80 are strongly dependent on the independent variables. The value of similarity factor indicate that there is no significant difference in drug release profiles of market formulation and formulation PG8 (f2=94.3). Formulation showed combine mechanism of drug release diffusion control release and anomalous effect. The results of storage-stability showed that optimized formulation was stable for at least 6 months under stress condition (40°C±2°C, RH 75%±5%). Use of Gellan gum along with hydrophilic polymer PEO effectively controls the initial rapid release and extends the drug release of a highly water soluble drug such as Metformin hydrochloride by formation of strong and stable gel layer.
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