Azathioprine for rheumatoid arthritis


Generic Name Brand Name
azathioprine Azasan, Imuran

Azathioprine is taken orally in pill form.

How It Works

Azathioprine is an immunosuppressive medicine, which means that it decreases the action of your body's immune system. By interrupting the immune process, azathioprine reduces inflammation and slows joint damage caused by rheumatoid arthritis. But lowering your immune function may make you more susceptible to infection.

Azathioprine is a disease-modifying antirheumatic drug (DMARD), which means it slows the progression of the disease. DMARDs are also called immunosuppressive drugs or slow-acting antirheumatic drugs (SAARDs).

Why It Is Used

Azathioprine is used for severe rheumatoid arthritis that has not responded to other treatments.

How Well It Works

While azathioprine has been found to reduce inflammation and slow disease progress in some people with rheumatoid arthritis, it does not appear to be as effective as some other DMARDs.1

Side Effects

Serious side effects from azathioprine may include:

  • Suppression of blood cell production, which may increase the risk of infection or cause anemia.
  • Inflammation of the liver (hepatitis) or pancreas (pancreatitis).

Because azathioprine decreases the activity of your body's natural immune system, fever and chills are considered serious side effects that should be reported to your health professional immediately.

Less serious side effects of azathioprine may include:

  • Nausea.
  • Vomiting.
  • Diarrhea.
  • Abdominal pain.
  • Rash.
  • General feeling of being ill.

Azathioprine, like some other DMARDs, may slightly increase your risk of cancer of the lymph glands (lymphoma) in the future.

Risk of infection

Azathioprine decreases the activity of your body's immune system, which increases the risk of a serious bacterial infection. Some people who take azathioprine develop an infection that requires oral antibiotics. A smaller number of people will develop an infection that requires intravenous antibiotics and hospitalization. Contact your health professional if you develop any of the following symptoms:

  • Fever or chills
  • Increased frequency of or burning during urination
  • A cough with yellow sputum or shortness of breath
  • A skin infection
  • Severe abdominal pain or diarrhea
  • A severe sore throat
  • Sinus pain with yellow mucus
  • A painful, burning rash in a band across one side of your body (shingles)
  • Painful, widespread mouth sores

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Azathioprine and other immunosuppressive medicines may be more toxic than other DMARDs, such as methotrexate, and should be used only under the supervision of a specialist in rheumatic disease (rheumatologist) who is familiar with their side effects.

Azathioprine should not be used by pregnant women or women of childbearing age who are not using reliable birth control. If you are going to take azathioprine, you should be on some form of reliable birth. If you plan to become pregnant, check with your health professional before stopping birth control and trying to become pregnant.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.



  1. Walker-Bone K, Fallow S (2007). Rheumatoid arthritis, search date June 2005. Online version of BMJ Clinical Evidence. Also available online:

Last Updated: August 18, 2008

Author: Shannon Erstad, MBA/MPH

Medical Review: Anne C. Poinier, MD - Internal Medicine & Stanford M. Shoor, MD - Rheumatology

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