Sulfasalazine is used to treat bowel inflammation, diarrhea (stool frequency), rectal bleeding, and abdominal pain in patients with ulcerative colitis, a condition in which the bowel is inflamed. Sulfasalazine delayed-release (Azulfidine EN-tabs) is also used to treat rheumatoid arthritis in adults and children whose disease has not responded well to other medications. Sulfasalazine is in a class of medications called anti-inflammatory drugs.