Release of mifepristone from biodegradable matrices: experimental and theoretical evaluations

Diffusion of mifepristone in poly [(D,L) lactide-co-glycolide)] films was s tudied by release experiments. Five 50/50 copolymers of increasing molecula r weights were used. The degradation effects were shown by gel permeation c hromatography (GPC). Release kinetics show the effect of copolymer molecula r weights on diffusion and degradation properties of loaded films. A new th eoretical model for drug release from a biodegradable matrix was proposed w ith two assumptions: correlation of the diffusion coefficient with the poly mer molecular weight and existence of a first order degradation kinetic. Hi guchi's equation is verified at early time and the diffusion coefficient in the non-degraded polymer can be measured. The degradation constant is dete rmined at long time and is compared with the results of GPC. (C) 2000 Elsev ier Science B.V. All rights reserved.