STEADY SHEAR AND DYNAMIC SHEAR RHEOLOGICAL PROPERTIES OF CARBOXY-METHYL LOCUST BEAN GUM INFLUENCING EROSION OF THE POLYSACCHARIDE COAT OF COMPRESSION COATED TABLETS

Rheological properties of carboxymethyl locust bean gum (CMLBG) solutions having different concentrations and solution pH were evaluated through steady shear and oscillatory measurements and were used to describe the erosion propensity of CMLBG coat of compression coated placebo tablets. CMLBG solutions, irrespective of concentration and solution pH, exhibited predominant viscous character as the viscous modulus (G”)> elastic modulus (G’) and phase angle (Tan δ) > 1. The viscous contribution was found to be influenced by both the CMLBG concentration and solution pH. An increase in CMLBG concentration increased the pseudo-plasticity and consistency coefficient and decreased the viscous contribution in all solution pH resulting in a decrease in erosion of CMLBG coat. The higher viscous character of CMLBG in buffer solution of pH 7.4 (Solution B) was responsible for higher erosion of the coat than in acid solution of pH 1.2 (Solution A). When the pH of acid solution of CMLBG was increased dynamically from 1.2 to 7.4, the viscous contribution decreased to some extent than that observed in Solution B leading to a decrease in coat erosion which was albeit more than in Solution A. Rheological parameters could be used as a tool to describe erosion of polysaccharide coated tablets.