Bilayer Tablet Formulation of Metformin Hydrochloridea and Glipizide a Novel Approach in the Treatment of Diabetes.

In 1985, there were approximately 30 million people with diabetes worldwide; by 1995, this number had escalated to 135 million and by 2025, it is projected that there will be an increase in the incidence of diabetes, affecting 300 million people. Most of the expected increase will be in type 2 diabetes, which accounts for >90% of cases of diabetes, while the incidence of Type 1 diabetes is anticipated to remain stable. By 2025 the countries with largest number of people with diabetes will be in India (>57 million, prevalence 6%), China (>37 million, prevalence 3.4%), and the United States (>21 million, prevalence 8.9%). Metformin hydrochloride sustained release tablets and Glipizide immediate release tablets were prepared using direct compression and solid dispersion techniques respectively. HPMC used as matrix forming polymer for the Metformin layer enables drug release for up to 9-10 hours. Among the different grades of HPMC no significant difference in the resulting Metformin release profiles from the SR layer of the tablets was found. This indicates that the viscosity of the polymer does not affect drug release rate when drug is water soluble and the dose is high. The formulation F1 can be preferred as integrity was maintained. Glipizide release shows that the dissolution rate of glipizide can be enhanced considerably by formulating it as a solid dispersion with SSG using kneading method. Incorporation of super disitnegrants in the solid dispersions played a critical role in dissolution enhancement. SR fixed dose bilayer matrix tablets containing 500mgMetformin HCl as SR from one layer and 5mg Glipizide as IR from another layer have been prepared by solid dispersion method. Formulations F1 and F4 are selected for preparation of bilayer tablet F7. From formulation F7 Metformin hydrochloride and glipzide were found to be released for 10 hours and 20 minutes respectively.