It is intended to avoid dose dumping of a drug and improve the dissolution properties of the drug in the lower gastrointestinal tract, and thereby provide a sustained-release pellet preparation for oral administration that reliably exhibits its main pharmacological effect when orally administered once or twice a day. The present invention provides a sustained-release preparation obtained by mixing of (A) a pharmacologically active drug, (B) hydroxypropyl methylcellulose acetate succinate, (C) a plasticizer, and (D) polyethylene glycol followed by extrusion granulation.
