Chronic inflammatory bowel diseases are a group of diseases that still do not have a specific cause of their occurrence, are characterized by a particularly complex pathogenesis, a variety of clinical manifestations and a significant impact on the patient’s quality of life. Crohn’s disease and non-specific ulcerative colitis are diseases that run with the risk of severe exacerbations and can also lead to the patient’s disability. The main task in the treatment of inflammatory bowel diseases is the initiation of the remission stage and its long-term maintenance. For this, several groups of drugs are used, among which the drug of the first line of therapy is Mesalazine (Mesacol®), its effect on the intestinal wall consists in preventing the development of the inflammatory process by reducing the synthesis of pro-inflammatory prostaglandins and leukotrienes, slowing down the migration, degranulation and phagocytosis of neutrophils. In addition, mesalazine neutralizes free radicals, which increases the protective effect on the intestinal wall.