Site-specific oral controlled release metformin tablets - development, in vitro, ex vivo and in vivo evaluation

Oral absorption of metformin is confined to the upper part of intestine posing problems in the formulation of extended release tablets. Therefore, the objective of the present study was to develop controlled-release mucoadhesive core tablets and confine the tablets to the specific site in the gastrointestinal tract. A projective coat protects the core tablets from mucoadhesion till the targeted site is reached. Once the tablet reaches the specific site, the coat dissolves exposing the core tablet for mucoadhesion. In vitro coat intactness test and ex vivo tablet bioadhesion test confirmed that the tablets were targeted and contained in the upper intestine. Further, the pharmacokinetic parameters obtained for metformin from the site-specific coated formulation were better (P<0.05) than that of the non-site-specific uncoated formulation in the in vivo studies. Standardized formulation was stable during the stability studies conducted as per ICH Q1C guidelines.