Design and characterization of calcium-free in-situ gel formulation based on sodium alginate and chitosan

AbstractThe aim of this study was to prepare and evaluate calcium-free sustained release drug delivery systems, based on the in-situ gelation of oral suspensions containing chitosan, sodium alginate and Ranitidine as drug model. The combined effects of polymer concentrations and their interactions on the rheological characteristics of both gels and suspensions and, on the kinetics of drug release were evaluated by using a central composite face-centered design. Rheological analysis showed that suspensions were potentially stable, with a viscosity increased by 1000 times compared to that of water. In addition, the obtained gels were consistent; their storage modulus could reach values close to 50 kPa when alginate concentration was greater than 7.5 g/100 mL and chitosan was fixed to 0.5 g/100 mL. In these conditions gels should have a higher gastric residence time, in comparison to the standard gastric emptying time (∼2 h). Evaluation of the in-vitro release kinetics of Ranitidine showed that the associati...