A compound represented by the formula (I): wherein R 1 is a monocyclic nitrogen-containing heterocyclic group optionally condensed with a benzene ring or a heterocycle, the monocyclic nitrogen-containing heterocyclic group optionally condensed with a benzene ring or a heterocycle optionally has substituent(s), R 2 is an optionally substituted C 6-14 aryl group, an optionally substituted thienyl group or an optionally substituted pyridyl group, R 3 and R 4 are each a hydrogen atom, or one of R 3 and R 4 is a hydrogen atom and the other is an optionally substituted lower alkyl group, an acyl group, a halogen atom, a cyano group or a nitro group, and R 5 is an alkyl group, or a salt thereof, for use for the treatment or prophylaxis of peptic ulcer, Zollinger-Ellison syndrome, gastritis, erosive esophagitis, reflux esophagitis, symptomatic gastroesophageal reflux disease (Symptomatic GERD), functional dyspepsia, gastric cancer, stomach MALT lymphoma, or gastric hyperacidity； or the inhibition of upper gastrointestinal hemorrhage due to peptic ulcer, acute stress ulcer, hemorrhagic gastritis or invasive stress, or for use for the eradication of helicobacter pylori.
