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antirheumatic (disease-modifying)

bowel disease (inflammatory) suppressant

lupus erythematosus suppressant


Azathioprine (ay-za-THYE-oh-preen) belongs to the group of medicines known as immunosuppressive agents. It is used to reduce the body’s natural immunity in patients who receive organ transplants. It is also used to treat rheumatoid arthritis. Azathioprine may also be used for other conditions as determined by your doctor.

Azathioprine is a very strong medicine. You and your doctor should talk about the need for this medicine and its risks. Even though azathioprine may cause side effects that could be very serious, remember that it may be required to treat your medical problem.

Azathioprine is available only with your doctor’s prescription, in the following dosage forms:


Tablets (U.S. and Canada)


Injection (U.S. and Canada)

Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For azathioprine, the following should be considered:

Allergies-Tell your doctor if you have ever had any unusual or allergic reaction to azathioprine. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy-Use of azathioprine is not recommended during pregnancy. It may cause birth defects if either the male or the female is using it at the time of conception. The use of birth control methods is recommended. If you have any questions about this, check with your doctor.

Breast-feeding-Azathioprine passes into breast milk. Because this medicine may cause serious side effects, breast-feeding is generally not recommended while you are using it.

Children-This medicine has been tested in children and, in effective doses, has not been shown to cause different side effects or problems than it does in adults.

Older adults-Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of azathioprine in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults.

Other medicines-Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking or receiving azathioprine it is especially important that your health care professional know if you are taking any of the following:

Allopurinol (e.g., Zyloprim)-May interfere with removal of azathioprine from the body; effects of azathioprine (including toxicity) may be increased Chlorambucil (e.g., Leukeran) or Corticosteroids (cortisone-like medicine) or Cyclophosphamide (e.g., Cytoxan) or Cyclosporine (e.g., Sandimmune) or Mercaptopurine (e.g., Purinethol) or Muromonab-CD3 (monoclonal antibody) (e.g., Orthoclone OKT3)-There may be an increased risk of infection and cancer because azathioprine reduces the body’s ability to fight them.

Other medical problems-The presence of other medical problems may affect the use of azathioprine. Make sure you tell your doctor if you have any other medical problems, especially:

Chickenpox (including recent exposure) or Herpes zoster (shingles)-Risk of severe disease affecting other parts of the body

Gout-Allopurinol (used to treat gout) may increase wanted and unwanted effects of azathioprine

Infection-Azathioprine decreases your body’s ability to fight infection

Kidney disease or Liver disease-Effects of azathioprine may be increased because of slower removal from the body

Pancreatitis (inflammation of the pancreas)-Azathioprine can cause pancreatitis

Proper Use of This Medicine

Use this medicine only as directed by your doctor. Do not use more or less of it, and do not use it more often than your doctor ordered. The exact amount of medicine you need has been carefully worked out. Taking too much may increase the chance of side effects, while taking too little may not properly treat your condition.

This medicine is sometimes given together with certain other medicines. If you are using a combination of medicines, make sure that you take each one at the proper time and do not mix them up. Ask your health care professional to help you plan a way to remember to take your medicines at the right times.

Do not stop taking this medicine without first checking with your doctor.

Azathioprine sometimes causes nausea or vomiting. Taking this medicine after meals or at bedtime may lessen stomach upset. Ask your health care professional for other ways to lessen these effects.

If you vomit shortly after taking a dose of azathioprine, check with your doctor. You will be told whether to take the dose again or to wait until the next scheduled dose.


The dose of azathioprine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of azathioprine. If your dose is different, do not change it unless your doctor tells you to do so.

The number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are taking azathioprine.

For oral dosage form (tablets):

For transplant rejection:

Adults, teenagers, and children: Dose is based on body weight or size. The usual beginning dose is 3 to 5 milligrams (mg) per kilogram (kg) (1.5 to 2 mg per pound) of body weight a day. As time goes on, your doctor may lower your dose to 1 to 2 mg per kg (0.5 to 1 mg per pound) a day.

For rheumatoid arthritis:

Adults, teenagers, and children: Dose is based on body weight or size. The usual beginning dose is 1 mg per kg (0.5 mg per pound) of body weight a day. Your doctor will increase this dose as needed. The highest dose is usually not more than 2.5 mg per kg (1 mg per pound) a day. Your doctor may then lower your dose as needed.

For injection dosage form:

For transplant rejection:

Adults, teenagers, and children: Dose is based on body weight or size. The usual beginning dose is 3 to 5 milligrams (mg) per kilogram (kg) (1.5 to 2 mg per pound) of body weight a day. As time goes on, your doctor may lower your dose to 1 to 2 mg per kg (0.5 to 1 mg per pound) a day.

Missed dose-If you miss a dose of this medicine and your dosing schedule is:

One dose a day-Do not take the missed dose at all and do not double the next one. Instead, go back to your regular dosing schedule and check with your doctor.

More than one dose a day-Take the missed dose as soon as you remember it. If it is time for your next dose, take both doses together, then go back to your regular dosing schedule. If you miss more than one dose, check with your doctor.

Storage-To store this medicine:

Keep out of the reach of children.

Store away from heat and direct light.

Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.

Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly and to check for unwanted effects.

While you are being treated with azathioprine, and after you stop treatment with it, do not have any immunizations (vaccinations) without your doctor’s approval.

Azathioprine lowers your body’s resistance and there is a chance you might get the infection the immunization is meant to prevent. In addition, other persons living in your household should not take oral polio vaccine since there is a chance they could pass the polio virus on to you. Also, avoid persons who have recently taken oral polio vaccine.

Do not get close to them, and do not stay in the same room with them for very long. If you cannot take these precautions, you should consider wearing a protective face mask that covers the nose and mouth.

Azathioprine can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.

Check with your doctor immediately if you notice any unusual bleeding or bruising; black, tarry stools; blood in urine or stools; or pinpoint red spots on your skin.

Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your health care professional before having any dental work done.

Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.

Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.

Avoid contact sports or other situations where bruising or injury could occur.

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Some side effects will have signs or symptoms that you can see or feel. Your doctor will watch for others by doing certain tests.

Also, because of the way these medicines act on the body, there is a chance that they might cause other unwanted effects that may not occur until months or years after the medicine is used. These delayed effects may include certain types of cancer, such as leukemia, lymphoma, or skin cancer. However, the risk of cancer seems to be lower in people taking azathioprine for arthritis. Discuss these possible effects with your doctor.

Check with your doctor immediately if any of the following side effects occur:

More common

Unusual tiredness or weakness

Less common

Cough or hoarseness; fever or chills; lower back or side pain; painful or difficult urination


Black, tarry stools; blood in urine or stools; fast heartbeat; fever (sudden); muscle or joint pain; nausea, vomiting, and diarrhea (severe); pinpoint red spots on skin; redness or blisters on skin; stomach pain (severe) with nausea and vomiting; unusual bleeding or bruising; unusual feeling of discomfort or illness (sudden)

Check with your doctor as soon as possible if any of the following side effects occur:


Shortness of breath; sores in mouth and on lips; stomach pain; swelling of feet or lower legs

This medicine may also cause the following side effect that your doctor will watch for:

Less common

Liver problems

For patients taking this medicine for rheumatoid arthritis:

Signs and symptoms of blood problems (black, tarry stools; blood in urine or stools; cough or hoarseness; fever or chills; lower back or side pain; painful or difficult urination; pinpoint red spots on skin; unusual tiredness or weakness; or unusual bleeding or bruising) are less likely to occur in patients taking azathioprine for rheumatoid arthritis than for transplant rejection. This is because lower doses are often used.

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

More common

Loss of appetite; nausea or vomiting

Less common

Skin rash

After you stop using this medicine, it may still produce some side effects that need attention. During this period of time check with your doctor immediately if you notice any of the following:

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

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

Additional Information

Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although these uses are not included in product labeling, azathioprine is used in certain patients with the following medical conditions:

Bowel disease, inflammatory

Hepatitis, chronic active

Cirrhosis, biliary

Lupus erythematosus, systemic


Nephrotic syndrome

Myopathy, inflammatory

Myasthenia gravis

Dermatomyositis, systemic



Other than the above information, there is no additional information relating to proper use, precautions, or side effects for these uses.

Copyright © 1998 The United States Pharmacopeial Convention, Inc. (“USP”)