Anatomical Therapeutic Chemical Classification System
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.