Gastrointestinal disturbances frequently occur in patients taking sulfasalazine that may include:
- gastric distress, and
- loss of appetite.
Headache, allergic reactions, and photosensitivity (development of a rash when exposed to sunlight) may develop during sulfasalazine therapy and require medical attention. Some of the allergic reactions may progress from a rash to difficulty in swallowing, blistering, peeling, or loosening of the skin, aching joints and muscles, and unusual tiredness or weakness. It may be accompanied by fever. The more severe allergic reactions are rare. Sulfasalazine may cause the skin or the urine to change color. Development of an orange-yellow discoloration of the urine is no cause for concern. Several potentially dangerous side effects have been reported rarely with sulfasalazine. A drop in white blood cell count or a type of anemia in which red blood cells are disrupted (hemolyzed) may occur. These effects are characterized by fever, pale skin, sore throat, fatigue, and unusual bleeding and bruising, and require discontinuation of the drug. Liver failure, pancreatitis, and kidney failure also have been associated with sulfasalazine.