COATING OF CERTAIN MATRIX CORES WITH AQUEOUS-BASED SYSTEMS OF ACRYLATE METHACRYLATE, A WATER-INSOLUBLE COPOLYMER AND DRUG RELEASE PROFILES

Physical mixtures of an acrylate methacrylate copolymer (in fine powder) and salicyclic acid (drug model) in a ratio of 1:4, have been compressed directly (i.e. without further granulation) to matrix (non-disintegrating) tablets to serve as core models. A coacervation technique was used to form an aqueous-based coating system consisting of a water-insoluble copolymer and sucrose in varying proportions. Film coatings were applied on the matrix cores to a thickness 75 +/- 3-mu-m (SEM). Drug-release rates increased as a linear function of the initial sucrose content in the film coatings. The amount of sucrose leached from the film coatings into the leaching fluid also increased linearly and in parallel with the increase in release rates. The release profiles obtained with cores with coating thickness of 75-mu-m were generally without a time-lag. Doubling the coating thickness introduced a time-lag (preceding the onset of release) of about 2.5 h, 1.3 h or 0.5 h for polymeric coatings without sucrose, or with sucrose 12.5% w/w, or 25% w/w, respectively. Coatings with a higher sucrose content did not display the release time-lag. Overall release rates were hardly affected by the increase in coating thickness.