Medications and Drugs

Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: sulfasalazine

BRAND NAME: Azulfidine

DRUG CLASS AND MECHANISM: Sulfasalazine is a drug that is used primarily for treating ulcerative colitis. It is a prodrug, that is, it is not active in its ingested form. It is broken down by bacteria in the colon into 5-aminosalicylic acid (5-ASA), and sulfapyridine. (5-ASA is also marketed as mesalamine (Lialda, Rowasa, Pentasa, Canasa Apriso, and Asacol.) The 5-ASA has therapeutic benefit, but it is not clear if sulfapyridine adds any additional therapeutic benefit. The inflammation of ulcerative colitis and other inflammatory diseases is caused, in part, by excessive production of chemicals (for example, prostaglandins) that produce inflammation. Prostaglandins are produced by two enzymes, cyclooxygenase and lipoxygenase, and these enzymes are over-active in individuals with ulcerative colitis. 5-ASA may reduce inflammation by blocking the activity of cyclooxygenase and lipoxygenase thereby reducing the production of prostaglandins. Sulfasalazine was approved by the FDA in 1950.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets: 500 mg.

STORAGE: The tablets should be kept at room temperature, 15-30 C (59-86 F).

PRESCRIBED FOR: Sulfasalazine is used for the treatment of mild to severe ulcerative colitis, and treatment of rheumatoid arthritis. It has also been used "off label" (unapproved by the FDA) for Crohn's disease and ankylosing spondylitis.

DOSING: Adult doses range from 1000 mg to 4000 mg daily. Sulfasalazine is administered 2 to 4 times daily depending on the disease for which it is used. Sulfasalazine should be taken with a full glass of water after meals or with food to minimize upset stomach. Patients with kidney diseases may need to use lower doses of sulfasalazine.

DRUG INTERACTIONS: Sulfasalazine may cause reduced absorption of folic acid and digoxin (Lanoxin). Reduced folic acid absorption may cause folic acid deficiency and result in anemia. Reduced digoxin absorption may reduce the effectiveness of digoxin. Sulfapyridine (a byproduct of sulfasalazine) is a sulfonamide, and sulfonamides increase blood levels of methotrexate (Rheumatrex, Trexall), resulting in increased methotrexate toxicity. Conversely, methotrexate can increase the occurrence of the anemia caused by sulfonamides because methotrexate also causes folic acid deficiency. Sulfonamides can increase the risk of kidney damage from cyclosporine by an unknown mechanism. They also may increase the blood glucose lowering effect of oral anti-diabetic drugs and potentially cause excessive reductions in blood sugar (hypoglycemia) by decreasing elimination of anti-diabetic drugs by the liver and elevating the levels of the anti-diabetic drugs in the blood.

Combining 5-ASA with drugs that affect kidney function such as nonsteroidal antiinflammatory drugs, for example, ibuprofen (Advil), may increase the likelihood of kidney dysfunction. Concurrent use of 5-ASA and 6-mercaptopurine or azathioprine (Imuran) may increase the likelihood of blood disorders. 5-ASA may increase the blood thinning effect of warfarin (Coumadin).

PREGNANCY: In hundreds of pregnant women with ulcerative colitis or Crohn's disease treated with sulfasalazine, there has been no increase in the risk of fetal malformations relative to other women with these illnesses who have not been treated with sulfasalazine. Additionally, there have not been ill effects on pregnant animals given high doses of sulfasalazine. Thus, sulfasalazine may be used during pregnancy if the physician feels the benefit outweighs the possible risk.

It should also be noted, however, that sulfasalazine may reduce sperm count and sperm function in men. These effects are reversible upon stopping the drug.

NURSING MOTHERS: Caution should be exercised by women who are nursing their infants. Sulfasalazine and its constituents are secreted into breast milk. There is a small risk that sulfapyridine (a byproduct of sulfasalazine) may displace bilirubin from albumen in the blood of infants and cause jaundice.

SIDE EFFECTS: Gastrointestinal disturbances frequently occur in patients taking sulfasalazine. Nausea, vomiting, gastric distress, and anorexia (loss of appetite) commonly occur. Sulfasalazine may cause the skin or the urine to change color. Development of an orange-yellow discoloration is no cause for concern.

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.

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.

Reference: FDA Prescribing Information