Evaluation of acrylic-based modified-release film coatings

Abstract

Although insoluble pharmaceutical additives have been generally incorporated into film-coating formulations to impart a particular color to a solid dosage form or to reduce tackiness during the coating process, the inclusion of insoluble excipients in Eudragit E 30 D formulations, instead of the commonly used hydrophilic polymers, generated predictable modified-release reservoir systems. Dissolution studies of Eudragit E 30 D-coated pellets indicated that the release profiles depended not only on the physicochemical properties of the drug, particularly solubility, but also on the coating levels and the ratio of the additive to Eudragit resin in the dry film. Moreover, the integrity of the coating material and hence the release rates were found to be independent of the pH of the dissolution medium. Storing the coated pellets below the softening temperature of the Eudragit film for an extended period of time did not lead to a significant change in the release profiles. The predominant mechanism of drug release appears to be diffusion through water-filled pores in the film coat. The pellets were overcoated with a water-soluble hydrophilic polymer to prevent aggregation and enhance flowability. The overcoat did not affect the rate or extent of drug release.