Disclosed i s a preparation which, m an orally last-disintegrating tablet having as an active ingredient z-(3-cyano-4- isobutyloxyphenyl)-4-methyl-5-thiazole carboxylic acid, causes basically n o irritation i n the mouth or throat, retains good dis solv ability and oral disintegration even when stored under high temperature or high humidity conditions. The disclosed orally fast-dis integrating tablet i s formed t o contain particles comprising nuclear particles which contain 2-(3-cyano-4-isobutyloxyphenyl)-4- methyl-5-thiazole carboxylic acid, which are covered b y a layer containing a methacrylic acid copolymer, and wmch are further coated with an outer layer containing water-soluble sugars, such that after two weeks o f storage under conditions with the cap open at 40C / 75% RH, a dissolution test performed according t o the Japanese Pharmacopoeia Paddle Method at 50 revolutions per minute (test solution: pH6.0Mcllvaine buffer) evaluates the dissolution rate of the 2-(3-cyano-4-isobutyloxyphenyl)-4- methyl-5-thiazole carboxylic acid at 70% or greater after 10 minutes.
