Therefore, CYP2C19 genotyping appears to be a useful tool for determining optimal treatment to prevent bleeding from artificial ulcers and delayed bleeding from artificial ulcers within 24 h after ESD, as the onset of gastric acid secretion inhibition by H2RA drugs is more rapid than that of PPIs, suggesting that H2RA may be more effective, particularly in CYP2C19 RMs, than PPI [57]. Here, CYP2C19 is linked to ulcer disease.