Sulfasalazine is used in the treatment of inflammatory bowel disease, including ulcerative colitis and Crohn's disease. It is also indicated for use in rheumatoid arthritis and used in other types of inflammatory arthritis (e.g. psoriatic arthritis) where it has a beneficial effect. It is often well tolerated compared to other DMARDS.

In recent British research involving animal studies, and more recently, human trials for the treatment of chronic alcoholics, sulfasalazine has been found to reverse the scarring associated with cirrhosis of the liver. Cells called myofibroblasts, which contribute to scar tissue in a diseased liver, also appear to secrete proteins that prevent the breakdown of the scar tissue. Sulfasalazine appears to retard this secretion.A study at University of Newcastle found that the drug may also act to aid the healing of cirrhosis of the liver.^[1][2]

It is usually not given to children under 2 years of age.

The use of sulfasalazine in inflammatory bowel disease has declined due mainly to the fact that it yields the metabolite sulfapyridine which gives rise to side-effects such as agranulocytosis and hypospermia. However, the other metabolite of sulfasalazine, 5-aminosalicylic acid (5-ASA) is attributed to the drug's therapeutic effect. Therefore, 5-ASA and other derivatives of 5-ASA, are now usually preferred and given alone (as mesalazine), despite their increased cost, due to their more favourable side-effect profile.

Sulfasalazine has also been used successfully to treat cases of idiopathic urticaria that do not respond to antihistamines.^[3]