A quinolinone derivative with anti-ulcer and anti-inflammatory activities. Rebamipide induces cyclooxygenase 2 (COX2) synthesis which results in an increase in endogenous prostaglandin synthesis in the gastric mucosa. This agent also inhibits H. pylori-induced production of tumor necrosis factor (TNF) alpha and subsequent inflammation of the gastric mucosa. In addition, rebamipide scavenges oxygen-derived free radicals that potentially cause mucosal injury, and stimulates prostaglandin EP4 receptor gene expression followed by mucous secretion, thereby enhancing the gastric mucosal defense.