The present invention provides a coated solid preparation applicable to a one-dosepack, wherein, even when the preparation is in an unpacked state, thestability againstmoisture of valproic acid or a pharmacologically acceptable salt thereofcontained therein ismaintained and the deliquescence is suppressed. The present invention providesa coatedsolid preparation which contains, as an active ingredient, valproic acid or apharmacologicallyacceptable salt thereof and is coated with a coating layer containingpolyvinyl alcohol andswelling clay, wherein the mass ratio of the polyvinyl alcohol to the swellingclay is 8:2 to 3:7and the swelling clay is dispersed as a laminated structure. The polyvinylalcohol and theswelling clay occupy 88 mass percent or more of the coating, and the swellingclay isbentonite or magnesium aluminum silicate. Other ingredient(s) in thepreparation are one ormore pharmaceutical excipient(s).
