Sulfasalazine, sold under the brand name Azulfidine among others, is a medication used to treat rheumatoid arthritis, ulcerative colitis, and Crohn's disease. It is considered by some to be a first-line treatment in rheumatoid arthritis. It is taken by mouth. Sulfasalazine was approved for medical use in the United States in 1950. It is on the World Health Organization's List of Essential Medicines. Sulfasalazine is available as a generic medication. In 2020, it was the 284th most commonly prescribed medication in the United States, with more than 1 million prescriptions.