Synergistic Homopolysaccharide:Heteropolysaccharide Interactions-Rheological Investigation and Development of Sustained Release Tablets

Polymers used in combinations, the net effect produced by them is much greater than that given when used alone. Pronounced synergistic interactions have been observed when homopolysaccharide (galactomannan) and heteropolysaccharide, xanthan gum (XG) used together. Polymers from galactomannan category like guar gum (GG) and locust bean gum (LBG) and heteropolysaccharide were evaluated for optimum viscosity synergism. Viscosity studies of aqueous solutions of individual polymers and their combinations were carried out to find out the optimum ratio for synergism. The polymeric synergism and nature was confirmed using modern techniques of analysis like x-ray diffractometry (XRD), Differential scanning calorimetry (DSC) and Fourier Transform Infrared Spectrophotometry (FTIR). Matrix tablets were formulated using Metoprolol tartarte as a model drug and evaluated for erosion and swelling indices to correlate with the in vitro dissolution data. The in vitro dissolution data of the optimized formulation batches was compared with the matrices formulated using different grades of HPMC. XG:LBG and XG:GG in the ratio of 2:8 and 6:4 shown maximum viscosity synergism. Erosion was found to decrease in the order of LBG>>>>GG>XG>XG>XG:GG>XG:LBG. The highest swelling index, axial and radial, was obtained for the matrices containing combination of XG:LBG and XG:GG. XRD and FTIR spectra did not show any change in polymeric characteristics and chemical interactions respectively. However, the physical origin of synergistic interactions has been confirmed by DSC study. The advantage of using synergistically interacting materials to control drug release is that relatively smaller tablets can be produced that have a more precisely tailored drug delivery profile.