Olsalazine is an anti-inflammatory medication used in the treatment of ulcerative colitis.

[4] Olsalazine itself is a pro-drug of mesalazine (5-aminosalicyclic acid or 5-ASA) and is not absorbed in the small intestine.

Olsalazine thus exerts its anti-inflammatory effect by its colonic breakdown into 5-ASA which inhibits cyclooxygenase and lipoxygenase thereby reducing prostaglandin and leukotriene production.

[4] Olsalazine gained Food and Drug Administration (FDA) approval in 1990.

In 2006 the Australian biotech company Giaconda received a European patent for a combination therapy for treating constipation-predominant irritable bowel syndrome that uses olsalazine and the anti-gout drug colchicine, for trials the following year.