It is known that gastritis, gastroduodenitis and peptic ulcer belong to the group of acid-dependent diseases, which occupy a significant proportion among the digestive system diseases. Despite the use of proton pump inhibitors in therapy, the discovery of an important role of H. pylori infection in the genesis of these diseases and the development of eradication schemes, the urgency of the problem persists due to the development of formidable complications (bleeding, perforation). The modern therapeutic concept of treatment of peptic ulcer (including gastroduodenitis) provides active therapeutic tactics and includes multicomponent drug regimens. Along with proton pump inhibitors, the dietary recommendations, appointment of gastro-cytoprotectors, including ones of natural origin, and the individual approach to the patient in each specific case have not outlived their usefulness. Methylmethionine sulfonium chloride (vitamin U) Gastrarex, which improves the secretory and reparative function of the stomach, may be administered as one of the components of the complex therapy of peptic ulcer and gastroduodenitis.