5ASA

5-aminosalicylic acid (5-ASA) is a salicylate anti-inflammatory medication used primarily for inflammatory bowel disease. It is the active moiety in several ulcerative colitis therapies, including mesalamine, and is released in the colon from prodrugs such as sulfasalazine, balsalazide, and olsalazine. It is employed to induce and maintain remission in mild-to-moderate ulcerative colitis and is also used in Crohn's disease that involves the colon.

The exact mechanism of action is not fully understood. 5-ASA is believed to act locally on the intestinal mucosa, inhibiting inflammatory mediators such as prostaglandins and leukotrienes, scavenging reactive oxygen species, and modulating signaling pathways including nuclear factor kappa B and cytokine production. Formulations that release 5-ASA in the colon maximize local effects while minimizing systemic exposure.

Formulations and administration vary. Mesalamine comes in several oral release forms (immediate and various colon-targeted systems). Sulfasalazine combines 5-ASA with sulfapyridine, the latter of which is released in the gut and may cause more adverse effects; the 5-ASA component is the therapeutic part. Dosing for ulcerative colitis generally ranges from about 1 to 4 grams per day, given in divided doses, with lower doses used for maintenance. In Crohn's disease with colonic involvement, similar dosing is used; efficacy for isolated small-bowel disease is more limited.

Adverse effects are typically mild but can include headache, nausea, abdominal pain, and rash. Rare but serious risks include nephrotoxicity (interstitial nephritis), hepatotoxicity, pancreatitis, and hypersensitivity reactions. Caution is advised in renal impairment or sulfa allergies, and drug interactions should be reviewed with a clinician.