Mechanistic evaluation of the effect of thermal-treating on Eudragit RS matrices

Thermal treatment of acrylic matrices was recently introduced as a tool for prolonging the release of drug. Thermal treatment at temperatures above the T_g of the polymer can decrease drug release rate. In this research we studied the mechanism of the effect of thermal treatment on Eudragit RS matrices. Indomethacin was used as model drug. The results showed that polymer chain movement and redistribution of the polymer in the tablet matrix structure after thermal-treating is the possible mechanism of drug release prolongation. The melting and resolidification of the polymer, due to the thermal treatment has apparently resulted in a redistribution of the polymer throughout the matrix and a change in the porosity of the tablet. FTIR results did not show any drug–polymer interaction due to heat-treatment. DSC and PXD studies ruled out the occurrence of solid solution and polymorphic change of the drug.