Studies on Preparation and Characterization of Carboxymethyl high Amylose Starch: As a Novel Polymeric Carrier in Oral Controlled Drug Delivery

Abstract

The present study involved the use of old biomaterial starch as excipient for oral controlled drug delivery in which the properties of starch are tailored by chemical modification. Among the various commercially available starches, high amylose starch (HAS) was chosen and chemically modified by reaction with monochloro acetic acid in the presence of sodiumhydroxide to carboxymethyl high amylose starch (CM HAS). The starch derivative was synthesized with three different degree of substitution (CM HAS 1(DS 0.63), CM HAS 2(DS 0.35) and CM HAS 3(DS 0.21)) by varying the molar concentration of monochloro acetic acid in non-aqueous medium (organic solvent method). The prepared polymeric excipients were characterized by FT IR, DSC, 1H NMR, acute toxicity studies and solubility studies. The CM HAS matrix tablets (F1-F18) were formulated using nimodipine as model drug with different polymer concentrations by direct compression method and the physicochemical parameters were evaluated. The in vitro release profile showed a low drug release in acid pH followed by controlled drug release in phosphate buffer pH 6.8 and best fit to zero order release kinetics. The mechanism of drug release followed was found to be supercase II transport release mechanism. The absence of immediate and fast disintegration of the CM HAS matrix tablets proved as a promising new excipient for the development oral controlled drug delivery system. It was concluded that CM HAS with higher DS (0.35 and 0.63) at above 40% concentration were able to control drug release up to 12hrs.