The influence of Metolose structure on the free volume and the consequent metoprolol tartrate release of patches.

Matrix-type patches containing Metoprolol tartrate were prepared from two types of Metolose and acrylate polymers. Metolose SM 4000 and Metolose 90SH 100.000SR were applied in different proportions in the patches where the total polymer content was kept constant in each sample. The purpose of the study was to investigate the effect of Metolose structure on the free volume of the patches and the consequent drug release profile. The drug release profiles were characterized by zero-order and first-order models. The results indicate that Metolose, containing hydroxypropyl ether groups and methyl ether groups, enables the formation of H-bonds, thus increasing the free volume holes and the consequent extent and rate of drug release of patches.