Preparation and evaluation of dual modified Godare ( Colocasia esculenta) starch as a sustained release excipient in tablet formulations
Starch obtained from Colocasia esculenta, Araceae (locally known as godare) has been pregelatinized, cross-linked and evaluated as a sustained release excipient and hydrophilic matrix former in tablet formulations. The pregelatinized starch (PGS) was cross-linked in a microwave oven at three different powers (90, 220 and 350 W) and reaction times ranging from 1 to 6 min, using sodium hexametaphosphate (SHMP) as cross-linking agent. Theophylline tablets containing 30, 40, and 50% and the modified starches were compressed at a constant compression force. Dissolution profiles of theophylline were determined in 0.1 N HCl for the first 2 h and then in phosphate buffer pH 6.8 for the remaining 10 h. Degree of cross-linking (DC) increased with increasing reaction power and time. The resulting modified starches were found to be freely flowing, moisture and acid resistant. Two of the nine theophylline tablet formulations sustained the release over the study period of 12 h releasing about 90% of the drug. The in vitro drug release showed best fit to Higuchi and Hixson-Crowell models depending on the polymer-drug ratio and the type of matrix formers. The dual modified starch in a concentration ranging from 40 to 50% exhibited the attributes of sustained release matrix-forming polymer in the tablet formulations studied.
Keywords: godare starch, dual modification, microwave, sustained release, hydrophilic matrix