The Release Mechanism of an Oral Controlled-Release Delivery System for Indomethacin

ABSTRACTThis study was carried out to fully characterize the release kinetics of an oral controlled-release tablet formulation of indomethacin with xanthan gum. Matrix swelling, matrix erosion, and drug diffusion studies were performed to elucidate the operative release mechanisms of a tablet compressed from a ternary mixture of indomethacin-xanthan gum-lactose. Drug release tests were performed according to the USP paddle method in phosphate buffer pH 7.4, concurrently with the dissolution of the gum. Mean dissolution time (MDT) of the drug was calculated from the release profile and it was used as a parameter to evaluate the influence of (a) polymer content in the dosage form, (b) ionic strength of the medium, and (c) the rotation speed of the paddle on the release characteristics of the drug. There is a linear relationship between MDT and the inverse of polymer content. Within the range of ionic strength of the gastrointestinal tract, the salt concentration of the dissolution medium has a negative (inh...