Abstract: The invention provides a hydrogen-type sustained-release preparation comprising (1) at least one drug, (2) an additive which insures a penetration of water into the core of the preparation and (3) a hydrogen-forming polymer, wherein said preparation is capable of undergoing substantially complete gelation during its stay in the upper digestive tract such as stomach and small intestine and is capable of releasing the drug in the lower digestive tract including colon. By the preparation of the invention, the drug is efficiently released and absorbed even in the colon so that a steady and sustained release effect can be achieved.