Production of microparticle

PURPOSE: To obtain a microparticle formulation having a continuously sustained release character over a specific time by adding a solution of a peptide medicinal, etc., to a solution of a polymeric base material to effect dispersion followed by addition of a phase inducer and an oil-in-water emulsion. CONSTITUTION: This microparticle formulation is obtained by the following process: (A) a polymeric base material is dissolved in a solvent insoluble for the medicinal compound (pref. a water-soluble peptide), (B) a solution of the medicinal compound prepared by dissolving the compound in a solvent insoluble for the polymer is added to the solution in the process A to effect dispersion, (C) a phase inducer is added to the resultant dispersion to induce the formation of microparticles, (D) an oil-in-water emulsion is added to the above dispersion to effect coagulation of the microparticles, and (E) the microparticles are recovered to obtain the objective microparticle formulation. In an embodiment, for example, an aqueous medium solution of somatostatin at 2.5 g/10 mL and an organic solvent solution of polylactide-co-glycolide at 40 g/100 mL incompatible with the above aqueous medium are vigorously mixed with each other in a weight ratio of e.g. (1:16) and via the above processes C to E, to obtain the microparticles.