Injectable microcapsules prepared with biodegradable poly(α-hydroxy) acids for prolonged release of drugs

In this paper, microencapsulation techniques for the preparation of drug-containing monolithic microcapsules for prolonged release using biodegradable poly(alpha-hydroxy) acids, such as polylactic acid, poly(lactide-co-glycolide) and copoly(lactic/glycolic) acid are reviewed. Phase separation, solvent evaporation, and spray drying procedures are discussed. In order to achieve controlled-release formulations of highly water-soluble drugs that are entrapped efficiently, various manufacturing techniques and procedures have been developed. Degradation of poly(alpha-hydroxy) acids is altered by the copolymer ratio and molecular weight of the polymer used to make microcapsules and the amounts of released microencapsulated drugs correlate almost linearly with polymer degradation, indicating that controlled-release formulations, which release drugs over different times, can be prepared using suitable poly(alpha-hydroxy) acids with different degradation rates.