Design and Comparative Evaluation of In-vitro Drug Release, Pharmacokinetics and Gamma Scintigraphic Analysis of Controlled Release Tablets Using Novel pH Sensitive Starch and Modified Starch- acrylate Graft Copolymer Matrices

The present investigation deals with the development of controlled release tablets of salbutamol sulphate using graft copolymers (St-g-PMMA and Ast-g-PMMA) of starch and acetylated starch. Drug excipient compatibility was spectroscopically analyzed via FT-IR, which confirmed no interaction between drug and other excipients. Formulations were evaluated for physical characteristics like hardness, friability, weight variations, drug release and drug content analysis which satisfies all the pharmacopoeial requirement of tablet dosage form. Release rate of a model drug from formulated matrix tablets were studied at two different pH namely 1.2 and 6.8, spectrophotometrically. Drug release from the tablets of graft copolymer matrices is profoundly pH-dependent and showed a reduced release rate under acidic conditions as compared to the alkaline conditions. Study of release mechanism by Korsmeyer's model with n values between 0.61-0.67, proved that release was governed by both diffusion and erosion. In comparison to starch and acetylated starch matrix formulations, pharmacokinetic parameters of graft copolymers matrix formulations showed a significant decrease in Cmax with an increase in tmax, indicating the effect of dosage form would last for longer duration. The gastro intestinal transit behavior of the formulation was determined by gamma scintigraphy, using (99m)Tc as a marker in healthy rabbits. The amount of radioactive tracer released from the labelled tablets was minimal when the tablets were in the stomach, whereas it increased as tablets reached to intestine. Thus, in-vitro and in-vivo drug release studies of starch-acrylate graft copolymers proved their controlled release behavior with preferential delivery into alkaline pH environment.