The application of microspheres from the copolymers of lactide and epsilon-caprolactone to the controlled release of steroids

The microspheres made of the copolymers of lactide and epsilon-caprolactone were used for the controlled release of progesterone and beta-estradiol. T he copolymers contained 83-94% of L or D,L-lactide. The influence of the mi crostructure of lactidyl blocks in the copolymer chains on the drug release rate was studied. More uniform release rate was observed in the case of th e copolymer derived from D,L-lactide as composed to L-lactide. For the copo lymer containing 83-94% of D,L-lactide units the progesterone and beta-estr adiol release rate in vitro was found to be practically constant within ove r 40 days. The in vivo studies performed on rats revealed that the period o f constant release rate of beta-estradiol can be prolonged to about 70 days . The microspheres made of the applied poly-(D,L-lactide-co-epsilon-caprola ctone) are the convenient system for long time release of steroids. (C) 199 8 Elsevier Science B.V. All rights reserved.