Disclosed is a stabilized preparation which comprises a drug unstable in a polyethylene glycol-containing preparation and a coating agent comprising a copolyvidone instead of polyethylene glycol with which the drug is coated, wherein the unstable drug in the polyethylene glycol-containing preparation is a compound represented by the formula: (see formula II) wherein: Ar represents an optionally substituted aromatic group, X represents a divalent C1-6 aliphatic hydrocarbon group which optionally have 1 or 2 divalent groups selected from the group consisting of -O-, -S-, -CO-, -SO-, -SO2- and -COO-, Y represents a divalent C1-6 aliphatic hydrocarbon group, R and R are the same or different and each represents a hydrogen atom or an optionally substituted C1-6 alkyl, ring A represents a benzene ring which may be further substituted, and ring B represents a 4- or 8- membered ring which may be further substituted, or a pharmaceutically acceptable salt thereof.
