OCTENYL SUCCINATE CASSAVA STARCH AS AN EXCIPIENT FOR CONTROLLED RELEASE OF THEOPHYLLINE: MICROWAVE-ASSISTED SYNTHESIS, CHARACTERIZATION AND IN-VITRO DRUG RELEASE STUDIES

Octenyl succinate derivatives (OSA) of cassava starch having different degree of substitution (DS) were synthesized by microwave irradiation in solid state using a monomode reactor and the drug, theophylline (Thp) was successfully incorporated in the modified starches for getting controlled release properties. The reaction conditions were optimized for maximizing the DS by response surface methodology and it ranged from 0.002 to 0.021, for the different modified starches. Pre-formulation study was done by Fourier transformed infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) for testing the drug-excipient compatibility. Drug incorporated tablets were prepared using the modified starches and their properties were studied. The spectral and DSC studies showed that there was a good compatibility between OSA starch matrix and theophylline. The in vitro drug release study was performed under different conditions of pH and time as well as after storage of the tablets for different time durations.  The in vitro release rate was found to be significantly related to the DS of the modified starch and more sustained release of the drug was observed with the matrix incorporated with OSA starch of higher DS. Kinetics studies showed that the drug release obeyed Higuchi model and the release mechanism was coupled diffusion and erosion.