ATC Group: A07EC Aminosalicylic acid and similar agents
Anatomical Therapeutic Chemical Classification System
Mesalazine is an aminosalicylate. The mechanism of action of mesalazine is not fully understood, but appears to have a topical anti-inflammatory effect on the colonic epithelial cells. Mucosal production of arachidonic acid metabolites, both through the cyclooxygenase and lipoxygenase pathways, is increased in patients with chronic inflammatory bowel disease, and it is possible that mesalazine diminishes inflammation by blocking cyclooxygenase and inhibiting prostaglandin production in the colon.
Olsalazine is bioconverted to 5-aminosalicylic acid (5-ASA), which has anti-inflammatory activity in ulcerative colitis. The conversion of olsalazine to mesalamine (5-ASA) in the colon is similar to that of sulfasalazine, which is converted into sulfapyridine and mesalamine. The mechanism of action of mesalamine (and sulfasalazine) is unknown, but appears to be topical rather than systemic.
Therapeutic benefit of sulfasalazine appears to be due to a local action of the sulfasalazine and its split product 5-aminosalicylic acid on the mucous membrane and deeper colonic structures.