Gastroretentive drug delivery of metformin hydrochloride: formulation and in vitro evaluation using 3(2) full factorial design.

Metformin Hydrochloride (MF) is glucose lowering agent that is widely used for management for type II diabetes. MF is reported to be absorbed mainly in upper part of GIT. It is having narrow absorption window and high water solubility, and it would be more beneficial to retain the drug in stomach for prolonged duration so as to achieve maximum absorption and better bioavailability. A conventional oral CR formulation releases most of the drug content at the colon, which requires that the drug will be absorbed from the colon. The present investigation is aimed to develop novel gastroretentive (GR) drug delivery system, which not only release the drug in the absorption window but also provides controlled release drug profile that may result patient compliance and therapeutic success. Floating tablets of MF was prepared using sodium alginate, and sodium carboxymethylcellulose was used as a gelling agent, and release modifiers, respectively. Eudragit NE 30 D was used as sustained release polymer to control the initial burst release. Drug and excipients compatibility studies were monitored by thermal analysis by using differential scanning calorimeter. 32 full factorial design was applied to optimize the formulation. The DSC thermogram of drug, polymer and physical mixtures revealed that there was no known interaction between drug and polymers. The prepared tablets were evaluated for in vitro dissolution, in vitro buoyancy, percentage swelling, percentage erosion and similarity factors with marketed tablets. The optimization study using a 32 full factorial design revealed that the amount of sodium alginate and sodium carboxymethylcellulose had a significant effect on t50, t90, Flag and f2. Thus, by selecting a suitable composition of release rate modifier and gel forming agent, Gastro retentive system can be developed with the desired dissolution profile. This study indicated that the MF GR tablets prepared using sodium alginate and sodium carboxymethylcellulose can successfully be employed as a once-a-day oral controlled release drug delivery system.