The side effects of H2-blockers include nausea, vomiting, dizziness, dry mouth, constipation, increased heart rate, etc. H2-blockers can effectively inhibit the secretion of gastric acid and are mainly used in the treatment of gastric ulcer and duodenal ulcer, and have a strong protective effect on the gastric mucosa. The most common adverse effects of long-term use are gastrointestinal reactions, and in some cases, neurological reactions, such as dizziness and headache, are also seen. Long-term use of the drug may also lead to mastocytosis in men and overflowing breast in women. Most of these adverse reactions are mild and do not require special treatment, and will disappear slowly after discontinuation of the drug. Side effects do not manifest themselves in exactly the same way depending on the generation level of the drug and the physical condition of the patient.