In the result of recent meta-analysis, there was no improvement in symptoms with the first administration of PPI in about 75% of GERD patients, and symptoms were still sustained in about 50% of patients after administration of more than 3 days. Especially the nocturnal secretion of gastric acid was not effectively inhibited, and about 25% of GERD patients could not achieve the proper therapeutic effects even after PPI treatment twice daily for 4-8 weeks.