An object of the invention is to provide a drug which is reduced in the side effects such as digestive tract disorder, has such a high safety as to permit long-term administration, and has anti-inflammatory, antipyretic, analgesic and and antiallergic activities. The drug comprises a compound represented by general formula (I) or a salt thereof, wherein R¹ represents phenyl, halophenyl or C₃-C₈ cycloalkyl; R² represents hydrogen or C₁-C₅ alkyl; and R³ represents hydrogen, C₁-C₇ alkyl, C₃-C₈ cycloalkyl, C₃-C₅ alkenyl or benzyl; or alternatively R² and R³ are combined together to represents a 5- to 7- membered heterocyclic group in combination with the nitrogen atom to which they are bonded.