H2 receptor antagonists: ranitidine, famotidine, cimetidine and nizatidine have been widely used in clinical practice. H2 receptor antagonists can bind to histamine H2 receptors in a highly selective manner and competitively antagonize the gastric acid caused by the binding of histamine to H2 receptors. H2 receptor antagonists are used to treat peptic ulcers by competitively antagonizing the secretion of gastric acid caused by the binding of histamine to H2 receptors, resulting in an acid-suppressive effect. Traditionally, the dose is administered in divided daily doses, such as cimetidine 200 mg four times a day or 400 mg twice a day, ranitidine 150 mg twice a day, famotidine 20 mg twice a day, nizatidine 150 mg twice a day, and rosuatidine 75 mg twice a day. The results of recent studies have shown that the basal secretion of histamine is predominantly nocturnal and that nocturnal gastric acidity plays an important role in the pathogenesis of peptic ulcers, especially duodenal ulcers. Daytime gastric acid secretion is associated with acetylcholine and gastrin, and the amount excreted is not only independent of ulcer formation, but also has the following significant physiological effects: maintenance of normal digestive processes, especially protein digestion, since the conversion of pepsinogen to pepsin can only be achieved in a sufficiently acidic environment; a certain level of gastric acidity is important in relation to calcium and iron absorption; normal daytime gastric acid secretion can Maintain a sterile environment in the stomach to avoid Candida from delaying ulcer healing, Helicobacter pylori infection causing premature recurrence of ulcer disease in some patients, and persistent suppression of gastric acid causing diarrhea in some patients. Therefore, it has been suggested that H2 receptor antagonists have a weak acid-suppressive effect during the day, while such drugs given at night can effectively inhibit gastric acid secretion, which can lead to rapid ulcer healing and symptom relief. This is supported by clinical observations that a single daily dose of H2 receptor antagonists given at bedtime is as fast as a single daily dose in terms of ulcer healing, symptom relief, and safety, and that this method of administration improves compliance in patients with ulcer disease. H2 receptor antagonists that have been used clinically are administered as a single one-day dose: cimetidine 800 mg, ranitidine 300 mg, famotidine 40 mg, nizatidine 300 mg, and rosuatidine 150 mg at bedtime.