Colonic drug delivery using amylose films: the role of aqueous ethylcellulose dispersions in controlling drug release

Abstract

Amylose, a plant polysaccharide from starch, can be combined with ethylcellulose to produce a film coating capable of effecting colon specific drug release from a dosage form through bacterial fermentation of the amylose component. Ethylcellulose is present in the system as a structuring agent in the form of the aqueous dispersion Surelease® grade EA-7100. There are, however, two other grades of Surelease® (E-7-7050 and E-7-19010), which vary slightly in terms of their composition. The aim of the study was to establish whether these grades differ in their drug release profiles, when used as a film coat, either as one-component coatings, or in combination with amylose. The dissolution profiles of Surelease® coated pellets were investigated and it was found that there was no difference between the grades when used as coating materials on their own. However, when used in combination with amylose, it was found that grade EA-7100 showed retardation of drug release in simulated upper gastro-intestinal (GI) conditions, whereas grades E-7-7050 and E-7-19010 did not limit the release to the same extent. E-7-19010 showed very poor controlled release properties when combined with amylose. These differences could not be attributed to the minimum film forming temperature (MFT) of the coating formulation, which was found to be independent of the grade of Surelease®. It was also confirmed that the film coated pellets prepared from amylose and EA-7100 showed good release in human faecal slurry, i.e. simulated colonic conditions. It was concluded that the grades of Surelease®, when combined with amylose, are not interchangeable.