A controlled-release anti-inflammatory drug. Studies on microcapsules

A procedure to obtain a controlled-release microencapsulated anti-inflammatory drug based on a solvent evaporation method is described. The present method makes use of ethylcellulose as the polymer and methylene chloride as solvent. The evaporation of solvent is controlled by means of an air stream. Variations in the preparative procedure and their effects on capsule dimensions and permeabilities were studied. The release behavior of the drug is determined, and two different diffusion constants are also determined: 7.0 X 10(-10) cm2/s and 1.2 X 10(-10) cm2/s, corresponding to low and high release time. Based on these results it is proposed that these microcapsules have a nonhomogeneous polymeric wall, and are more porous in the outer surface. This model might be applicable to the microcapsules obtained by means of the solvent evaporation method.