Sustained release micropellets showing a stable controlled-release of a drug without being affected by the changes in pH value etc., characterized by being produced by coating core particles with a layer containing a water-soluble drug and further forming a film layer containing a water-insoluble polymer compound and a plasticizer on the thus obtained particles, locating a water-soluble filler layer between the water soluble drug-containing layer and the film layer, and having an average particle size of 300 μm or less medicinal compositions containing these micropellets and a process for producing the same.
