A novel microparticle preparation comprising microparticles of a polymer which contain a drug and are at least partially or wholly coated with a water-soluble inorganic salt, a water-soluble organic acid or a water-soluble salt of an organic acid, which acts as an agent for preventing aggregation of the microparticle preparation is disclosed. The preparation is produced by spraying a polymer solution containing a drug and a solution or dispersion of a water-soluble inorganic salt, a water-soluble organic acid or a water-soluble salt of an organic acid from different nozzles and contacting them with each other in a spray dryer. In this procedure, if desired, a non-ionic surfactant may be added to the solution of the water-soluble inorganic salt, the water-soluble organic acid or the water-soluble salt of organic acid, or a solution of non-ionic surfactant may be sprayed from the other nozzle simultaneously. |