Olsalazine

Upon administration, the azo bond connecting two molecules of mesalamine (also known as 5-aminosalicylic acid or 5-ASA) is cleaved by azoreductase-containing bacteria in the colon. The two molecules of mesalamine are released to mediate therapeutic effects. The exact mechanism of action of olsalazine and its active moiety mesalamine in ulcerative colitis has not been elucidated; however, it is understood that mesalamine mediates an anti-inflammatory action on epithelial cells of the colon. The COX-derived (i.e., prostanoids such as prostaglandin E2) and lipoxygenase-derived products (i.e., leukotrienes [LTs] and hydroxyeicosatetraenoic acids [HETEs]) of arachidonic acid metabolism have been implicated in the pathogenesis and maintenance of inflammatory disorders, including ulcerative colitis and inflammatory bowel disease. Mesalamine may attenuate inflammation by blocking the COX enzyme and inhibiting prostaglandin production in the colon. Olsalazine was also shown to inhibit xanthine oxidase, an enzyme that generates oxygen-derived free radicals.

Olsalazine may attenuate intestinal inflammation by limiting macrophage migration to inflamed intestinal mucosa: it was shown to inhibit in vitro migration of intestinal macrophages in response to leukotriene B4. Olsalazine may also act as a free radical scavenger, and mesalazine may suppress fatty acid peroxidation.