The present invention relates to a solid preparation having an easily controllable elution property of a drug, and a method for improving dissolution of a drug.A solid preparation 1 comprises a drug-containing unit 2 containing a drug, and a gel-forming layer 4 for covering the drug-containing unit 2 and forming a gel by water absorption, and optionally an intermediate layer 3 interposed between the drug-containing unit 2 and the gel-forming layer 4. The solid preparation 1 improves the elution property of the drug by incorporating an effervescent agent (e.g., sodium hydrogencarbonate) into the drug-containing unit 2 and/or the intermediate layer 3. The drug-containing unit 2 may contain a cationic or basic drug. The gel-forming layer 4 may contain an anionic or acidic polymer. The gel-forming layer 4 may be covered with a surface layer (anti-adhesive layer) 5.
