Sulfasalazine is an anti-inflammatory indicated for the treatment of ulcerative colitis and rheumatoid arthritis. The mode of action of Sulfasalazine or its metabolites, 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), is still under investigation, but may be related to the anti-inflammatory and/or immunomodulatory properties that have been observed in animal and in vitromodels, to its affinity for connective tissue, and/or to the relatively high concentration it reaches in serous fluids, the liver and intestinal walls, as demonstrated in autoradiographic studies in animals. In ulcerative colitis, clinical studies utilizing rectal administration of Sulfasalazine, SP and 5-ASA have indicated that the major therapeutic action may reside in the 5-ASA moiety. The relative contribution of the parent drug and the major metabolites in rheumatoid arthritis is unknown. Sulfasalazine is used for the treatment of Crohn's disease and rheumatoid arthritis as a second-line agent. Sulfasalazine is marketed under the trade name Azulfidine among others.