Generic Name

Sulfasalazine

Brand Names
Azulfidine EN-tabs, Azulfidine
FDA approval date: June 20, 1950
Classification: Aminosalicylate
Form: Tablet

What is Azulfidine EN-tabs (Sulfasalazine)?

Living with chronic inflammation, whether in the joints or the digestive tract, can deeply affect daily life. Conditions like rheumatoid arthritis and ulcerative colitis can cause persistent pain, fatigue, and discomfort that make even simple activities challenging. Sulfasalazine is a long-established medication that helps manage these inflammatory diseases, improving symptoms, and overall quality of life for many patients.

What does Sulfasalazine do?

Sulfasalazine is primarily used to treat inflammatory bowel disease (IBD) and certain types of arthritis. Doctors commonly prescribe it for:

  • Ulcerative colitis, to reduce inflammation in the colon and relieve symptoms like diarrhea, abdominal pain, and bleeding.
  • Rheumatoid arthritis (RA), to ease joint pain, stiffness, and swelling when other first-line treatments aren’t enough.
  • Juvenile idiopathic arthritis (in children), in select cases.

In ulcerative colitis, sulfasalazine helps patients achieve and maintain remission, meaning fewer flares and more symptom-free days. In rheumatoid arthritis, it acts as a disease-modifying antirheumatic drug (DMARD), which means it not only eases symptoms but also slows joint damage over time.

Clinical studies have shown sulfasalazine to be effective in both gastrointestinal and joint inflammation management, particularly as part of combination therapy for rheumatoid arthritis (O’Dell et al., 1996).

How does Sulfasalazine work?

Sulfasalazine is a combination of two components, sulfapyridine and 5-aminosalicylic acid (5-ASA). When taken orally, gut bacteria break it down into these active parts:

  • 5-ASA reduces inflammation in the colon lining, helping calm ulcerative colitis symptoms.
  • Sulfapyridine contributes to immune-modulating effects, especially beneficial for arthritis.

Although the exact mechanism isn’t completely understood, sulfasalazine appears to suppress overactive immune responses and reduce the release of inflammatory substances like cytokines.

Clinically, this mechanism is valuable because it addresses both local gut inflammation and systemic immune activity, making the drug versatile in autoimmune conditions. By tackling inflammation at its source, sulfasalazine helps restore normal function and prevent long-term complications.

Sulfasalazine side effects

Sulfasalazine has been used for decades and is generally well-tolerated, but like all medications, it can cause side effects.

Common side effects:

  • Nausea or upset stomach
  • Loss of appetite
  • Headache
  • Skin rash
  • Orange-yellow discoloration of urine or skin (harmless but notable)

Less common but serious side effects:

  • Decreased white blood cells or platelets (which can increase infection or bleeding risk)
  • Liver inflammation
  • Allergic reactions such as fever, rash, or difficulty breathing
  • Reduced sperm count (temporary and reversible after stopping the drug)

People with sulfa allergies, liver disease, or blood disorders should avoid this medication unless specifically advised by their doctor.

Patients should seek medical attention immediately for signs of severe rash, persistent fever, sore throat, unusual bruising, or yellowing of the skin or eyes, as these may indicate rare but serious reactions.

Doctors typically order regular blood tests to check liver function, kidney health, and blood cell counts during treatment. These safety checks allow early detection of any potential side effects.

Sulfasalazine dosage

Sulfasalazine is available in tablet form, including delayed-release (enteric-coated) versions to minimize stomach irritation.

For ulcerative colitis, it’s often started at a low dose and gradually increased to manage inflammation effectively while limiting side effects. In rheumatoid arthritis, it is used as part of long-term therapy to help control disease progression.

Monitoring is essential during treatment. Doctors may check:

  • Complete blood counts to ensure healthy white and red blood cell levels.
  • Liver and kidney function tests at regular intervals.
  • Response to therapy, such as reduced joint pain or improved bowel regularity.

Patients are encouraged to stay well hydrated while taking sulfasalazine to prevent kidney-related complications and report any persistent side effects.

Older adults or those with kidney or liver impairment may need closer supervision or dose adjustments.

Does Sulfasalazine have a generic version?

Yes. Sulfasalazine is available in generic form, which is both FDA-approved and widely used. Generic versions are equally safe, effective, and affordable compared to brand-name products.

Common brand names include Azulfidine and Azulfidine EN-Tabs (the enteric-coated formulation). Generic versions are available under the name of sulfasalazine in most pharmacies and hospitals worldwide.

Because the medication has been on the market for decades, access and affordability are generally good, making it an important option in long-term inflammatory disease management.

Conclusion

Sulfasalazine remains a cornerstone therapy for ulcerative colitis and rheumatoid arthritis, thanks to its proven ability to reduce inflammation, control symptoms, and improve long-term outcomes. Its dual action, working locally in the gut and systemically on the immune system, makes it especially valuable for chronic inflammatory conditions.

While side effects and monitoring requirements are important to consider, most patients tolerate the medication well under medical supervision.

When prescribed and monitored by a qualified healthcare provider, sulfasalazine is a safe, effective, and time-tested treatment that can help patients regain comfort, mobility, and control over their condition leading to a better quality of life.

References

  1. U.S. Food and Drug Administration (FDA). (2023). Sulfasalazine prescribing information. https://www.fda.gov/
  2. Mayo Clinic. (2023). Sulfasalazine (oral route) description and precautions. https://www.mayoclinic.org/
  3. O’Dell, J. R., et al. (1996). Treatment of rheumatoid arthritis with methotrexate and sulfasalazine combination therapy. New England Journal of Medicine, 334(20), 1287–1291. https://www.nejm.org/
  4. MedlinePlus. (2024). Sulfasalazine – Drug information. https://medlineplus.gov/

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Brand Information

    Azulfidine (Sulfasalazine)
    1DESCRIPTION
    AZULFIDINE EN-tabs Tablets contain sulfasalazine, formulated in a delayed release tablet (enteric-coated), 500 mg, for oral administration.
    AZULFIDINE EN-tabs Tablets are film coated with cellulose acetate phthalate to retard disintegration of the tablet in the stomach and reduce potential irritation of the gastric mucosa.
    Therapeutic Classification: Anti-inflammatory agent and/or immunomodulatory agent.
    Chemical Designation: 5-([p-(2-pyridylsulfamoyl)phenyl]azo) salicylic acid.
    Chemical Structure:
    Chemical Structure
    Molecular Formula: C18H14N4O5S
    Inactive ingredients: beeswax (white), carnauba wax, cellacefate, magnesium stearate, polyethylene glycol, povidone, propylene glycol, self-emulsifying glycerol monostearate, silica (colloidal anhydrous), starch (pregelatinized), talc.
    2INDICATIONS AND USAGE
    AZULFIDINE EN-tabs Tablets are indicated:
    1. in the treatment of mild to moderate ulcerative colitis, and as adjunctive therapy in severe ulcerative colitis;
    2. for the prolongation of the remission period between acute attacks of ulcerative colitis;
    3. in the treatment of patients with rheumatoid arthritis who have responded inadequately to salicylates or other nonsteroidal anti-inflammatory drugs (e.g., an insufficient therapeutic response to, or intolerance of, an adequate trial of full doses of one or more nonsteroidal anti-inflammatory drugs); and
    4. in the treatment of pediatric patients with polyarticular-course
    AZULFIDINE EN-tabs is particularly indicated in patients with ulcerative colitis who cannot take uncoated sulfasalazine tablets because of gastrointestinal intolerance, and in whom there is evidence that this intolerance is not primarily the result of high blood levels of sulfapyridine and its metabolites, e.g., patients experiencing nausea and vomiting with the first few doses of the drug, or patients in whom a reduction in dosage does not alleviate the adverse gastrointestinal effects.
    In patients with rheumatoid arthritis or juvenile rheumatoid arthritis, rest and physiotherapy as indicated should be continued. Unlike anti-inflammatory drugs, AZULFIDINE EN-tabs does not produce an immediate response. Concurrent treatment with analgesics and/or nonsteroidal anti-inflammatory drugs is recommended at least until the effect of AZULFIDINE EN-tabs is apparent.
    3CONTRAINDICATIONS
    AZULFIDINE EN-tabs Tablets are contraindicated in:
    4ADVERSE REACTIONS
    The most common adverse reactions associated with sulfasalazine in ulcerative colitis are anorexia, headache, nausea, vomiting, gastric distress, and apparently reversible oligospermia. These occur in about one-third of the patients. Less frequent adverse reactions are pruritus, urticaria, rash, fever, Heinz body anemia, hemolytic anemia, and cyanosis, which may occur at a frequency of 1 in 30 patients or less. Experience suggests that with a daily dose of 4 g or more, or total serum sulfapyridine levels above 50 µg/mL, the incidence of adverse reactions tends to increase.
    Similar adverse reactions are associated with sulfasalazine use in adult rheumatoid arthritis, although there was a greater incidence of some reactions. In rheumatoid arthritis studies, the following common adverse reactions were noted: nausea (19%), dyspepsia (13%), rash (13%), headache (9%), abdominal pain (8%), vomiting (8%), fever (5%), dizziness (4%), stomatitis (4%), pruritis (4%), abnormal liver function tests (4%), leukopenia (3%), and thrombocytopenia (1%). One report
    In general, the adverse reactions in juvenile rheumatoid arthritis patients are similar to those seen in patients with adult rheumatoid arthritis except for a high frequency of serum sickness-like syndrome in systemic-course juvenile rheumatoid arthritis (see
    Although the listing which follows includes a few adverse reactions which have not been reported with this specific drug, the pharmacological similarities among the sulfonamides require that each of these reactions be considered when AZULFIDINE EN-tabs is administered.
    Less common or rare adverse reactions include:
    Blood dyscrasias: aplastic anemia, agranulocytosis, megaloblastic (macrocytic) anemia, purpura, hypoprothrombinemia, methemoglobinemia, congenital neutropenia, and myelodysplastic syndrome.
    Hypersensitivity reactions: erythema multiforme, epidermal necrolysis (SJS/TEN) with corneal damage, exfoliative dermatitis, DRESS, anaphylaxis, serum sickness syndrome, interstitial lung disease, pneumonitis with or without eosinophilia, vasculitis, fibrosing alveolitis, pleurisy/pleuritis, pericarditis with or without tamponade, allergic myocarditis, polyarteritis nodosa, lupus erythematosus-like syndrome, hepatitis and hepatic necrosis with or without immune complexes, fulminant hepatitis, sometimes leading to liver transplantation, parapsoriasis varioliformis acuta (Mucha-Haberman syndrome), rhabdomyolysis, photosensitization, arthralgia, periorbital edema, conjunctival and scleral injection and alopecia.
    Gastrointestinal reactions: hepatitis, hepatic failure, pancreatitis, bloody diarrhea, impaired folic acid absorption, impaired digoxin absorption, stomatitis, diarrhea, abdominal pains, and neutropenic enterocolitis.
    Central Nervous System reactions: transverse myelitis, convulsions, meningitis, transient lesions of the posterior spinal column, cauda equina syndrome, Guillain-Barre syndrome, peripheral neuropathy, mental depression, vertigo, hearing loss, insomnia, ataxia, hallucinations, tinnitus, and drowsiness.
    Renal reactions: toxic nephrosis with oliguria and anuria, nephritis, nephrotic syndrome, urinary tract infections, hematuria, crystalluria, proteinuria, and hemolytic-uremic syndrome.
    Other reactions: urine discoloration and skin discoloration.
    The sulfonamides bear certain chemical similarities to some goitrogens, diuretics (acetazolamide and the thiazides), and oral hypoglycemic agents. Goiter production, diuresis and hypoglycemia have occurred rarely in patients receiving sulfonamides.
    Cross-sensitivity may exist with these agents. Rats appear to be especially susceptible to the goitrogenic effects of sulfonamides and long-term administration has produced thyroid malignancies in this species.
    4.1Postmarketing Reports
    The following events have been identified during post-approval use of products which contain (or are metabolized to) mesalamine in clinical practice. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of seriousness, frequency of reporting, or potential causal connection to mesalamine:
    Blood dyscrasias: pseudomononucleosis
    Cardiac disorders: myocarditis
    Hepatobiliary disorders: reports of hepatotoxicity, including elevated liver function tests (SGOT/AST, SGPT/ALT, GGT, LDH, alkaline phosphatase, bilirubin), jaundice, cholestatic jaundice, cirrhosis, hepatitis cholestatic, cholestasis and possible hepatocellular damage including liver necrosis and liver failure. Some of these cases were fatal. One case of Kawasaki-like syndrome, which included hepatic function changes, was also reported.
    Immune system disorders: anaphylaxis
    Metabolism and nutrition system disorders: folate deficiency
    Renal and urinary disorders: nephrolithiasis
    Respiratory, thoracic and mediastinal disorders: oropharyngeal pain
    Skin and subcutaneous tissue disorders: angioedema, purpura, SJS/TEN, DRESS, and AGEP
    Vascular disorders: pallor
    5DRUG ABUSE AND DEPENDENCE
    None reported.
    6OVERDOSAGE
    There is evidence that the incidence and severity of toxicity following overdosage is directly related to the total serum sulfapyridine concentration. Symptoms of overdosage may include nausea, vomiting, gastric distress and abdominal pains. In more advanced cases, central nervous system symptoms such as drowsiness, convulsions, etc., may be observed. Serum sulfapyridine concentrations may be used to monitor the progress of recovery from overdosage.
    There are no documented reports of deaths due to ingestion of large single doses of sulfasalazine. It has not been possible to determine the LD
    6.1Instructions for Overdosage
    Gastric lavage or emesis plus catharsis as indicated. Alkalinize urine. If kidney function is normal, force fluids. If anuria is present, restrict fluids and salt, and treat appropriately. Catheterization of the ureters may be indicated for complete renal blockage by crystals. The low molecular weight of sulfasalazine and its metabolites may facilitate their removal by dialysis.
    7DOSAGE AND ADMINISTRATION
    The dosage of AZULFIDINE EN-tabs Tablets should be adjusted to each individual's response and tolerance.
    Patients should be instructed to take AZULFIDINE EN-tabs in evenly divided doses, preferably after meals, and to swallow the tablets whole.
    7.1Adult Rheumatoid Arthritis
    2 g daily in two evenly divided doses. It is advisable to initiate therapy with a lower dosage of AZULFIDINE EN-tabs, e.g., 0.5 to 1.0 g daily, to reduce possible gastrointestinal intolerance. A suggested dosing schedule is given below.
    In rheumatoid arthritis, the effect of AZULFIDINE EN-tabs can be assessed by the degree of improvement in the number and extent of actively inflamed joints. A therapeutic response has been observed as early as 4 weeks after starting treatment with AZULFIDINE EN-tabs, but treatment for 12 weeks may be required in some patients before clinical benefit is noted. Consideration can be given to increasing the daily dose of AZULFIDINE EN-tabs to 3 g if the clinical response after 12 weeks is inadequate. Careful monitoring is recommended for doses over 2 g per day.
    Suggested Dosing Schedule for Adult Rheumatoid Arthritis:
    7.2Juvenile Rheumatoid Arthritis - polyarticular course
    Children, six years of age and older: 30 to 50 mg/kg of body weight daily in two evenly divided doses. Typically, the maximum dose is 2 g per day. To reduce possible gastrointestinal intolerance, begin with a quarter to a third of the planned maintenance dose and increase weekly until reaching the maintenance dose at one month.
    Some patients may be sensitive to treatment with sulfasalazine. Various desensitization-like regimens have been reported to be effective in 34 of 53 patients,
    8HOW SUPPLIED
    AZULFIDINE EN-tabs Tablets, 500 mg, are elliptical, gold-colored, film enteric-coated tablets, monogrammed "102" on one side and "KPh" on the other. They are available in the following package sizes:
    8.1Storage
    Store at 25°C (77°F); excursions permitted to 15–30°C (59–86°F) [see USP Controlled Room Temperature].
    9REFERENCES
    1. van Rossum MAJ, et al. Sulfasalazine in the treatment of juvenile chronic arthritis: a randomized, double-blind, placebo-controlled, multicenter study. Arth Rheum 1998;41:808–816.
    2. Mogadam M, et al. Pregnancy in inflammatory bowel disease: effect of sulfasalazine and corticosteroids on fetal outcome. Gastroenterology 1981;80:726.
    3. Kaufman DW, editor. Birth defects and drugs during pregnancy. Littleton, MA: Publishing Sciences Group, Inc., 1977:296–313.
    4. Jarnerot G. Fertility, sterility and pregnancy in chronic inflammatory bowel disease. Scand J Gastroenterol 1982;17:1–4.
    5. Imundo LF, Jacobs JC. Sulfasalazine therapy for juvenile rheumatoid arthritis. J Rheumatol 1996;23:360–366.
    6. Hertzberger-ten Cate R, Cats A. Toxicity of sulfasalazine in systemic juvenile chronic arthritis. Clin Exp Rheumatol 1991;9:85–8.
    7. Farr M, et al. Immunodeficiencies associated with sulphasalazine therapy in inflammatory arthritis. British Jnl Rheum 1991;30:413–417.
    8. Korelitz B, et al. Desensitization to sulfasalazine in allergic patients with IBD: an important therapeutic modality. Gastroenterology 1982;82:1104.
    9. Holdworth CG. Sulphasalazine desensitization. Br Med J 1981;282:110.
    10. Taffet SL, Das KM. Desensitization of patients with inflammatory bowel disease to sulfasalazine. Am J Med 1982;73:520–4.
    10PRINCIPAL DISPLAY PANEL - 500 mg Tablet Bottle Label
    Pfizer
    NDC 0013-0102-01
    Azulfidine EN-tabs
    sulfasalazine delayed release
    tablets, USP
    500 mg
    100 Enteric-coated Tablets
    PRINCIPAL DISPLAY PANEL - 500 mg Tablet Bottle Label
    11PRINCIPAL DISPLAY PANEL - 500 mg Tablet Bottle Label - NDC 0013-0102-50
    Pfizer
    NDC 0013-0102-50
    Azulfidine EN-tabs
    sulfasalazine delayed release
    500 mg
    100 Enteric-coated Tablets
    PRINCIPAL DISPLAY PANEL - 500 mg Tablet Bottle Label - NDC 0013-0102-50
    12PRINCIPAL DISPLAY PANEL - 500 mg Tablet Bottle Carton - NDC 0013-0102-50
    Pfizer
    NDC 0013-0102-50
    Azulfidine EN-tabs
    sulfasalazine delayed release
    500 mg
    100 Enteric-coated Tablets
    PRINCIPAL DISPLAY PANEL - 500 mg Tablet Bottle Carton - NDC 0013-0102-50