Mesalazine, also known as Mesalamine or 5-aminosalicylic acid (5-ASA), is an anti-inflammatory drug used to treat inflammation of the digestive tract ulcerative colitis and mild-to-moderate Crohn's disease. Mesalazine is a bowel-specific aminosalicylate drug that acts locally in the gut and has its predominant actions there, thereby having few systemic side effects. As a derivative of salicylic acid, 5-ASA is also thought to be an antioxidant that traps free radicals, which are potentially damaging byproducts of metabolism. 5-ASA is considered the active moiety of sulfasalazine, which is metabolized to sulfapyridine and 5_ASA.