Sulfasalazine is used to treat a certain type of bowel disease called ulcerative colitis. This medication does not cure this condition, but it helps decrease symptoms such as fever, stomach pain, diarrhea, and rectal bleeding. After an attack is treated, sulfasalazine is also used to increase the amount of time between attacks. This medication works by reducing irritation and swelling in the large intestines. In addition, delayed-release tablets of sulfasalazine are used to treat rheumatoid arthritis. Sulfasalazine helps to reduce joint pain, swelling, and stiffness. Early treatment of rheumatoid arthritis with sulfasalazine helps to reduce/prevent further joint damage so you can do more of your normal daily activities. This medication is used with other drugs, rest, and physical therapy in patients who have not responded to other medications.