CA2358495A1 — Prolonged release microsphere encapsulating luteinizing hormone-releasing hormone analogues and method for preparing the same

USPTO Abstract

There is disclosed a prolonged release microsphere which can constantly release medicinal drugs, such as luteinizing hormone-releasing hormone analogues and encapsulate them at high content rates. It is prepared by dissolving a copolymer of lactide and gycolide in methylene chloride, dissolving a luteinizing hormone-releasing hormone analogue and a release-controlling material in a subsidiary solvent, combining the above two solutions with each other to produce an emulsion phase, dispersing the emulsion phase in a solution of polyvinyl alcohol in distilled water to give a single emulsion system, removing the combined solvent of the emulsion phase to generate a polymeric microsphere; freeze-drying the polymeric microsphere. The microsphere prepared has a much finer inner structure, by virtue of which the microsphere is secured in a constant release rate. The single emulsion system which simplifies the preparation, allows for the maintenance of a drug content of 10 % or more. The charged groups of the release-controlling materials associated with the polymers minimize the excess release of the oppositely charged drugs at an initial stage, playing an important role in keeping the release rate constant.