Sulfasalazine is used to treat ulcerative colitis (a condition which causes swelling and sores in the lining of the colon [large intestine] and rectum) and also to maintain improvement of ulcerative colitis symptoms. Sulfasalazine delayed-release (Azulfidine EN-tabs) is also used to treat rheumatoid arthritis in adults whose disease has not responded well to other medications or could not be tolerated. Sulfasalazine delayed-release (Azulfidine EN-tabs) is also used to treat polyarticular juvenile idiopathic arthritis (PJIA; a type of childhood arthritis that affects five or more joints during the first six months of the condition, causing pain, swelling, and loss of function) in children who have not been helped by other medications. Sulfasalazine is in a class of medications called anti-inflammatory drugs. It works by reducing inflammation (swelling) inside the body.