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Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Generic drug name: azathioprine (aze THY o prin)
Brand name(s): IMURAN
GENERIC: not available FAMILY: Drugs for Arthritis and Gout
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Immune system and skeletal abnormalities have occurred in infants of women taking azathioprine during pregnancy. This drug should not be used by pregnant women.

Breast-feeding Warning

Azathioprine is excreted in human milk. Because of the potential for adverse effects in nursing infants, including the possibility of tumors, you should not take this drug while nursing.

Safety Warnings For This Drug [top]


Chronic immunosuppression with this purine antimetabolite increases risk of neoplasia [cancer] in humans. Physicians using this drug should be very familiar with this risk as well as with the mutagenic potential to both men and women and with possible hematologic [blood cell] toxicities.[1]

Facts About This Drug [top]

Azathioprine (IMURAN) is a potent drug reserved for severe conditions. It prevents rejection of transplanted organs, particularly kidneys, by suppressing the immune system. When all other treatments (rest, anti-inflammatory drugs, gold compounds) fail to relieve rheumatoid arthritis, azathioprine may slow damage to the joints and control symptoms but does not cure any condition. It is an alternative when surgery for some disabling joint injury cannot be done, and is used to lower the dose of...

Azathioprine (IMURAN) is a potent drug reserved for severe conditions. It prevents rejection of transplanted organs, particularly kidneys, by suppressing the immune system. When all other treatments (rest, anti-inflammatory drugs, gold compounds) fail to relieve rheumatoid arthritis, azathioprine may slow damage to the joints and control symptoms but does not cure any condition. It is an alternative when surgery for some disabling joint injury cannot be done, and is used to lower the dose of steroids, often given along with azathioprine. It may take several weeks or even a few months for improvement to show.

Older people with age-related decrease in kidney function are more likely to need a low dose. In all ages, the lowest effective dose should be used.

Side effects

During the first couple of weeks of therapy with azathioprine, nausea is common. Since azathioprine affects your immune system, you may get infections, which can more easily become fatal. Azathioprine increases the risk of skin cancer, cervical cancer, Kaposi’s sarcoma and leukemia.[2] These risks increase when the drug is used for transplants and after the drug has been used for five years.[3] Azathioprine can also irritate the pancreas, damage bone marrow, and harm the liver enough to be life threatening. This liver damage is more apt to happen to men.[4] Lowering the dose may reverse some of these problems.

An article published in Prescrire International in May 2011 found that azathioprine and mercaptopurine (PURINETHOL) use was associated with an increased risk of lymphoma. The authors of the article stated that in these patients the risk of lymphoma was found to be about four times higher than in patients who had never used this medication and that a risk-benefit assessment should be considered when treating these patients.[5]

Health Canada (an agency similar to the FDA) issued an advisory in 2014 that cases of a type of rare, aggressive and often fatal blood cancer (hepatosplenic T-cell lymphoma –[HSTCL]) have been reported in patients using azathioprine or mercaptopurine (PURINETHOL). Deaths from HSTCL also have been reported in connection with use of these drugs.[6]

Regulatory actions surrounding azathioprine

2011: The Food and Drug Administration (FDA) informed the public that it continues to receive reports of a rare cancer of white blood cells (known as Hepatosplenic T-Cell Lymphoma or HSTCL), primarily in adolescents and young adults being treated for Crohn’s disease and ulcerative colitis with tumor necrosis factor blockers (REMICADE, ENBREL, and HUMIRA), associated with azathioprine and/or mercaptopurine, which were added to the list of drugs associated with this risk.[7]

2014: The FDA issued an advisory that it has received reports of progressive multifocal leukoencephalopathy (a potentially fatal viral infection that destroys the material that covers and protects the nerve fibers of the brain) associated with azathioprine. [8]

Before You Use This Drug [top]

Because your risk of developing cancer would rise, discuss the benefit/risk balance of using azathioprine with your doctor if you are taking or have previously taken: ALKERAN, chlorambucil, cyclophosphamide, CYTOXAN, LEUKERAN, melphalan.

Do not use if you are:

  • pregnant or breast-feeding

Tell your doctor if you have or have had:

  • allergy to azathioprine
  • chicken pox
  • gout
  • hepatitis zoster
  • herpes
  • infection
  • kidney or liver problems
  • pancreatitis
  • radiation therapy
  • severe xanthine oxidase deficiency
  • previous exposure to cytotoxic drugs or radiation

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

When You Use This Drug [top]

  • Keep your appointments for lab work. For the first two months blood tests should be done at least weekly, and at least monthly thereafter.
  • Your doctor should be experienced in immunosuppressive therapy.
  • Avoid places and people that expose you to bacterial or viral infections. Avoid crowds during flu seasons. Report the first sign of any infection to your doctor: cough, hoarseness, fever, chills, lower back or side pain, or painful or difficult urination.
  • Avoid immunizations unless approved by your doctor. Others in patient’s household should avoid oral polio vaccine.
  • Check with your doctor immediately if you have unusual bleeding or bruising, black, tarry stools, blood in urine or stools, or pinpoint red spots on skin.
  • Practice good hygiene. Wash your hands before touching your eyes or the inside of your nose.
  • Check with your dentist about teeth-cleaning methods suited to your condition. Check with your physician before having dental work done.
  • Be cautious using knives, razors, nail clippers, and other sharp objects.
  • Avoid engaging in contact sports, moving heavy objects, and activities where you might get bruised.
  • Continue to rest, get physical therapy, and use anti-inflammatory drugs if you have rheumatoid arthritis.
  • If you undergo emergency care, or surgery, including dental, tell your doctor that you take azathioprine.
  • If you must take allopurinol, your dose of azathioprine should be reduced to one-fourth the usual dose.

How to Use This Drug [top]

  • If you miss a dose, use the following guidelines: If you take the drug once a day, do not take the missed dose nor double the next dose. If you take the drug several times a day, then take it as soon as you remember or double the next dose only. Check with your doctor if you miss more than one dose.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Swallow tablet whole or break in half. If you take azathioprine once a day, take it at bedtime to reduce stomach upset. Otherwise, take it after a meal.
  • If your doctor prescribes a suspension, shake it well before measuring.
  • Store tablets at room temperature with lid on firmly. Do not expose to light and heat. Store other forms according to the prescription label. Keep out of reach of children.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

allopurinol, BACTRIM, co-trimoxazole, COUMADIN, warfarin (do not suddenly stop taking azathioprine or warfarin; check with your doctor), ZYLOPRIM.

The use of angiotensin converting enzyme (ACE) inhibitors to lower blood pressure together with azathioprine has been reported to cause a severe decrease in white blood cells.

Avoid live virus vaccines, such as polio vaccines, for at least three months after stopping azathioprine. Not only might the vaccine be ineffective, but you may be more apt to have adverse reactions to the vaccine. It is very important that you not come in close contact with anyone else, such as your grandchildren, getting live virus vaccines. If you must come in contact, especially with infants, wear a mask over your mouth and nose. Let someone else change and dispose of their diapers.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • bloody or black, tarry, or pale stools
  • unusual bleeding or bruising
  • difficulty breathing
  • chills
  • cough, hoarseness
  • severe diarrhea
  • dizziness
  • sudden fever
  • rapid heartbeat
  • severe nausea or vomiting
  • pain in lower back, muscles, joints, side, or stomach
  • pinpoint red spots, redness, blisters on skin
  • sores in mouth or lips
  • swelling of feet or legs
  • unusual tiredness or weakness
  • painful or difficult urination
  • dark or bloody urine
  • yellowing of eyes or skin
  • unusual feeling of discomfort or illness

Call your doctor if these symptoms continue:

  • abdominal pain
  • constipation
  • depression[9]
  • hair loss
  • headache
  • heartburn
  • loss of appetite
  • low blood pressure
  • nausea or vomiting
  • skin rash, itching
  • unusually deep suntan[10]
  • blurred vision[9]

Call your doctor if these symptoms continue after you stop taking this drug:

  • black, tarry stools
  • blood in urine
  • cough or hoarseness
  • fever or chills
  • lower back or side pain
  • painful or difficult urination
  • pinpoint red spots on skin
  • unusual bleeding or bruising

Signs of overdose:

  • pinpoint red spots on skin
  • unusual bleeding or bruising
  • diarrhea
  • fever or chills
  • cough or hoarseness
  • lower back or side pain
  • painful or difficult urination
  • nausea or vomiting

If you suspect an overdose, call this number to contact your poison control center: (800) 222-1222.

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

  • complete blood count
  • liver function tests

last reviewed February 29, 2024