A unique application and characterization of Eudragit E 30 D film coatings in sustained release formulations

Abstract

Eudragit is an aqueous dispersion of an acrylic resin that is based on poly(ethylacrylate-methylmethacrylate) esters. The polymer is neutral in character and hence is not sensitive to differences in pH. Incorporation of insoluble pharmaceutical additives in Eudragit E 30 D coating formulations instead of the commonly used hydrophilic polymers generated not only programmable sustained release reservoir systems but also protective coatings that are relatively resistant to water vapor permeation. The additives, such as kaolin and talc which are used as received without any pretreatment, exist as discrete particles within the polymeric matrix. Although they are not dispersed at the molecular level as are hydrophilic polymers, the insoluble solids are mixed uniformly within the polymeric dispersion to provide a homogeneous coat. The homogeneity of the coating material was confirmed both by dissolution studies and a microanalydcal technique that utilizes an energy dispersive X-ray spectrometer. In addition, scanning electron microscopic examination of the surface morphology of coated pellets that released their contents during dissolution and those which were not subjected to dissolution indicated that the physical adsorption of the insoluble additive in the polymeric matrix is permanent. These properties ensure both short- and long-term stability of the coating material and reproducible in vitro and in vivo release profiles.