REVIEW The mechanism of action of 5-aminosalicylic acid is unknown, but appears exert its anti-inflammatory effects locally (in the GI tract) rather than systemically. Mucosal production of arachidonic acid metabolites, both through the cyclooxygenase pathways (catalyzes the formation of prostaglandin precursors from arachidonic acid), and through the lipoxygenase pathways (catalyzes the formation of leukotrienes and hydroxyeicosatetraenoic acids from arachidonic acid and its metabolites), is increased in patients with chronic inflammatory bowel disease. Therefore, it is possible that 5-aminosalicylic acid diminishes inflammation by blocking production of arachidonic acid metabolites in the colon through both the inhibition of cyclooxygenase and lipoxygenase.
Wiggins JB, Rajapakse R: Balsalazide: a novel 5-aminosalicylate prodrug for the treatment of active ulcerative colitis. Expert Opin Drug Metab Toxicol. 2009 Oct;5(10):1279-84.
Ragunath K, Williams JG: Review article: balsalazide therapy in ulcerative colitis. Aliment Pharmacol Ther. 2001 Oct;15(10):1549-54.