[Design and development of controlled release of drugs from injectable microcapsules]

Monolithic microcapsules were designed and developed for controlled release of leuprorelin for one month following a single injection. Copoly (DL-lactic/glycolic) acid (PLGA) of copolymer ratio of 75/25 and average molecular weight of 14,000 was suitable for achieving steady serum leuprorelin levels in rats and dogs for 4 weeks. The clinical efficacy of these injectable microcapsules of leuprorelin has been widely proved for prostate cancer, endometriosis, and other sex hormone dependent diseases in about sixty countries. The interaction between the basic functional group of the drug and the carboxylic end group of PLGA was found to be the most important factor in preparing the microcapsules with a small initial burst, as shown with thyrotropin releasing hormone (TRH) and a water-soluble GPIIb/IIIa antagonist (TAK-029).