Quadruple therapy is used to eradicate H. pylori, often consisting of two antibiotics plus a bismuth agent and a proton pump inhibitor, with the following side effects Antibiotics, such as amoxicillin and clarithromycin, may cause allergic reactions during use, as well as have a killing effect on the flora of the intestine, leading to dysbiosis of the intestinal flora, manifesting as bloating, abdominal pain, constipation and diarrhea. Bismuth agents such as colloidal pectin bismuth may show constipation, dark stools and dark tongue after use. The side effects of proton pump inhibitors, such as omeprazole, are relatively small.