5-aminosalicylic acid (5-ASA) is a medication primarily used to treat inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease. It works by reducing inflammation in the lining of the intestines, helping to alleviate symptoms like abdominal pain and diarrhea. 5-ASA is available in various forms, including oral tablets and rectal suppositories. It is often prescribed as part of a long-term treatment plan to maintain remission and prevent flare-ups of these conditions. Common brand names for 5-ASA include Asacol and Pentasa.