To obtain a preparation orally administered which is coated with sustained-release preparation coats, enables to use crystals obtained by the production of an effective substance as it is without expensive pharmaceutical manufacturing processes and is regulated in the release of opioid analgesics.

The preparation orally administered, which is in the form of crystals with a particle size of 10 μm-3 mm, preferably 50 μm-1 mm, and is coated with at least one kind of sustained-release preparation coats and regulated in the release of opioid analgesics, is obtained. It is favorable that the crystals have a single crystalline or polycrystalline structure and the sustained- release preparation coats are mainly composed of a polymer and contain a nonsustained-release polymer not more than 30 wt.%. As the polymer, an acrylic resin and/or a cellulose derivative, preferably an alkylcellulose, is preferably used. Further, hydromorphone, oxycodone, morphine, levorphanol, methadone, dihydrocodein or the like is preferably used as the opioid analgesic.