Generic Name: azathioprine, Oral tablet

Azasan,Imuran

All Brands

  • Azasan
  • Imuran
SECTION 1 of 4

Highlights for azathioprine

Oral tablet
1

Azathioprine is an oral medication used to treat rheumatoid arthritis and to keep your immune system from attacking a new kidney after a transplant.

2

Common side effects include nausea, vomiting, and diarrhea.

3

Using this medication for a long time may increase your risk of developing certain types of cancer.

4

To treat your condition, this medication lowers the activity of your immune system. This can increase your risk of infections.

5

Azathioprine is a category D pregnancy drug. It has a risk of adverse effects to a fetus. It should only be used during pregnancy in serious cases where it's needed to treat a dangerous condition in the mother.

IMPORTANT INFORMATION

FDA Warning

This drug has a Black Box Warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients to potentially dangerous effects.

Cancer. Long-term use of azathioprine may increase your risk of developing certain types of cancer, such as lymphoma, leukemia, and solid tumors.

Increased risk of infections

This medication lowers the activity of your immune system. This may increase your risk of infections.

May cause stomach problems

Azathioprine may lead to a serious reaction that can cause nausea and vomiting, as well as:

  • diarrhea
  • rash
  • fever
  • tiredness
  • muscle aches
  • liver damage
  • dizziness
  • low blood pressure

These effects usually happen within the first few weeks after starting the medication. If your doctor stops the drug, your symptoms should go away.

Low blood cell counts

Azathioprine increases your risk of developing a low blood cell count, such as low white blood cell counts. Having certain genetic problems can also increase your risk of a blood disorder. Your doctor will give you blood tests to monitor for these blood disorders. They may lower your dose or stop the medication.

Drug Features

Azathioprine is a prescription medication. It’s available in oral tablet form.

It’s also available in a generic version. Generic drugs usually cost less. In some cases they may not be available in every strength or form as the brand. Talk to your healthcare provider to see if the generic will work for you.

This drug may be used as part of a combination therapy. That means you may need to take it with other drugs.

Why It's Used

Azathioprine is used to treat rheumatoid arthritis (RA) and to keep your immune system from attacking a kidney transplant.

More Details

How It Works

Azathioprine works by lowering the activity of your body’s immune system. For RA, this keeps your immune system from attacking and damaging your joints.

More Details

Why It's Used

Azathioprine is used to treat rheumatoid arthritis (RA) and to keep your immune system from attacking a kidney transplant.

When you receive a kidney transplant, your immune system views the kidney as something that doesn’t belong in your body. This may cause your body to attack the kidney, which can lead to serious health problems or death. Azathioprine is used to stop your immune system from attacking your kidney.

In RA, your body attacks your joints, which can cause swelling, pain, and loss of function. Azathioprine is used to stop your immune system from attacking your joints.

How It Works

Azathioprine works by lowering the activity of your body’s immune system. For RA, this keeps your immune system from attacking and damaging your joints. For a kidney transplant, the drug keeps your immune system from attacking the newly transplanted kidney.

Azathioprine belongs to a class of drugs called immunosuppressants. 

SECTION 2 of 4

azathioprine Side Effects

Oral tablet

Most Common Side Effects

The most common side effects that occur with azathioprine include:

  • low white blood cell counts

  • infections

  • stomach problems, including nausea, diarrhea, and vomiting

Serious Side Effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening or if you think you’re experiencing a medical emergency, call 9-1-1.

  • gastrointestinal drug hypersensitivity. Symptoms may include:

    • nausea and vomiting
    • diarrhea
    • skin rash
    • fever
    • muscle aches
    • liver damage
    • dizziness
    • low blood pressure. Symptoms of low blood pressure may include dizziness, feeling faint, and trouble breathing.

    These problems usually happen within the first few weeks of starting the medication. Your doctor may stop the medication and your symptoms should go away.

  • extreme tiredness

  • pancreatitis. Symptoms may include:

    • severe abdominal pain
    • fatty stools
  • excessive weight loss

  • significant allergic reaction. Symptoms may include:

    • wheezing
    • chest tightness
    • itching
    • swelling of your face, lips, tongue, or throat
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Azathioprine does not cause drowsiness.

Mild side effects may go away within a few days or a couple of weeks. Talk to your doctor or pharmacist if they’re more severe or don’t go away.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 4

azathioprine May Interact with Other Medications

Oral tablet

Azathioprine can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist. 

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Medications That Might Interact with This Drug

Gout drugs
  • allopurinol. Using this drug with azathioprine can increase the levels of azathioprine in your body and increase your risk of side effects. Your doctor may lower your dose of azathioprine if you’re taking allopurinol.
  • febuxostat: Using this drug with azathioprine can increase the levels of azathioprine in your body and increase your risk of side effects. These medications shouldn’t be used together.

Inflammatory bowel disease drug
  • aminosalicylates. Using this drug with azathioprine can increase the levels of azathioprine in your body and increase your risk of bleeding disorders.

Inflammation drugs

These are TNF-modifier drugs. They work to reduce inflammation and immune system response. These include:

  • adalimumab
  • certolizumab
  • infliximab
  • golimumab

Medication that affects your immune system
  • cotrimoxazole 

Using this drug with azathioprine can decrease the amount of white blood cells in your body necessary to fight an infection. This increases your risk of infection. 

Using this drug with azathioprine can also increase your risk of side effects of both drugs.

Blood pressure drugs
  • ACE Inhibitors

Using these drugs with azathioprine can increase the levels of azathioprine in your body and increase your risk of blood disorders.

Blood thinning drug
  • warfarin

Using warfarin with azathioprine can decrease the levels of warfarin in your body. This would make warfarin less effective for you. Your doctor may closely monitor your levels of warfarin when starting and stopping treatment with azathioprine.

Hepatitis C drug
  • ribavirin

Using ribavirin with azathioprine can increase the levels of azathioprine in your body and increase your risk of side effects.

Vaccines
  • live vaccine. Receiving live vaccines while taking azathioprine may increase your risk of having negative side effects from the vaccine. Examples are:
    • nasal flu vaccine
    • measles, mumps, rubella vaccine
    • chickenpox (varicella) vaccine
  • inactivated vaccine. Receiving this type of vaccine while taking azathioprine may lower the effectiveness of the vaccine.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

People with thiopurine S-methyltransferase (TPMT) deficiency

TPMT is an enzyme in your body that breaks down azathioprine. When you don’t have enough TPMT, you’re at increased risk of side effects and blood disorders from azathioprine. Your doctor may do a test to check the levels of TPMT in your body.

People with low blood cell counts

Azathioprine raises your risk of lowered blood cell counts. Having certain genetic problems can also increase your risk. Your doctor may do blood tests and may lower your dose or stop the medication.

People with infections

This medication lowers the activity of your immune system. This may make infections that you have even worse.

People with liver problems

Azathioprine can increase your risk of liver problems, usually in kidney transplant patients. Your doctor will take blood tests to check how well your liver is working. Liver problems usually happen within 6 months of kidney transplant and usually go away when azathioprine is stopped.

Pregnant women

Azathioprine is a category D pregnancy drug. That means two things:

  1. Studies show a risk of adverse effects to the fetus when the mother takes the drug.
  2. This drug should only be used during pregnancy in serious cases where it's needed to treat a dangerous condition in the mother.

Tell your doctor if you’re pregnant or plan to become pregnant. Azathioprine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Women who are nursing

Azathioprine passes into breast milk and may cause side effects in a breastfeeding child. Breastfeeding isn’t recommended while taking this medication.

For Seniors

The safety and effectiveness of azathioprine haven’t been established in people aged 65 years and older.

For Children

The safety and effectiveness of azathioprine haven’t been established in people under the age of 18 years.

Allergies

Azathioprine can cause a severe allergic reaction. Symptoms may include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal.

SECTION 4 of 4

How to Take azathioprine (Dosage)

Oral tablet

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What Are You Taking This Medication For?

Kidney transplant
Form: Oral Tablet
Strengths: 50 mg tablet (Imuran and generic azathioprine only), 75 mg (Azasan only), and 100 mg (Azasan only)
Adult Dosage (ages 18 years and older)
  • Dosage is based on a person’s weight in kilograms (kg).
  • The starting dose is 3–5 mg per kilogram of body weight taken once on the day of transplant.
  • In certain cases, this dose may be given 1–3 days before the kidney transplant.
  • The maintenance dose is 1–3 mg/kg of body weight per day.
Child Dosage (ages 0-17 years)

A safe and effective dose hasn’t been established for this age group.

Special Considerations

Kidney Problems: Your dose of azathioprine may need to be lowered if you have kidney problems in which you don’t urinate regularly.

TPMT deficiency: Your dose of azathioprine may need to be lowered if tests show that you have TPMT deficiency. This enzyme helps to break down the drug. Not having enough of the enzyme can lead to an increased risk of side effects, including bleeding problems.

Rheumatoid arthritis
Form: Oral Tablet
Strengths: 50 mg tablet (Imuran and generic azathioprine only), 75 mg (Azasan only), and 100 mg (Azasan only)
Adult Dosage (ages 18 years and older)
  • Dosage is based on a person’s weight in kilograms (kg).
  • The starting dose is 50–100 mg taken once per day or split into two daily doses.
  • After 6–8 weeks of being on the initial dose, your doctor may increase your dose by 0.5 mg/kg of body weight per day.
  • Your doctor may make dose changes every 4 weeks if necessary.
  • The maximum daily dose is 2.5 mg/kg of body weight per day.
  • For a maintenance dose, doses can be lowered by 0.5 mg/kg of body weight per day every 4 weeks.
Child Dosage (ages 0-17 years)

A safe and effective dose hasn’t been established for this age group.

Special Considerations

Kidney Problems: Your dose of azathioprine may need to be lowered if you have kidney problems in which you don’t urinate regularly.

TPMT deficiency: Your dose of azathioprine may need to be lowered if tests show that you have TPMT deficiency. This enzyme helps to break down the drug. Not having enough of the enzyme can lead to an increased risk of side effects, including bleeding problems.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Azathioprine comes with serious risks if you don't take it as prescribed.

If You Don't Take It At All

For kidney transplant: You’re at increased risk of experiencing negative, possibly fatal side effects from your transplanted kidney or having to undergo another kidney transplant.

For rheumatoid arthritis: Your symptoms may not improve or they may even get worse over time.

If You Stop Taking It Suddenly

For kidney transplant: If you stop taking azathioprine suddenly, you may experience transplant rejection and kidney failure.

For rheumatoid arthritis: If you stop taking azathioprine suddenly, your symptoms of rheumatoid arthritis may come back again.

If You Don't Take It on Schedule

For both conditions: You may not see a full benefit of this medication. If you double up your dose or take it too close to your next scheduled time, you may be at higher risk of experiencing serious side effects.

What to Do If You Miss a Dose

If you miss a dose, take it as soon as you can. However, it it’s just a few hours until your next dose, skip the missed dose and take the next one only.

Never try to catch up by taking two doses at once. This could result in toxic side effects.

How to Tell If the Drug Is Working

You may be able to tell if this drug is working for RA if you have less swelling and pain in your joints and if you’re able to move around better. This should happen after about 12 weeks of being on the medication.

For a kidney transplant, you may be able to tell if it’s working if your kidneys are functioning and you aren’t experiencing symptoms of organ rejection. These symptoms can include discomfort or ill feeling, fever, flu-like symptoms, and pain or swelling around the organ. Your doctor will also do blood tests to check for kidney damage.

This is a long-term medication.

Important Considerations for Taking Azathioprine
take after a meal Take this medication after a meal. This may help lower your risk of stomach problems
storage Store in temperatures from 59–77°F (15–25°C) See Details
refillable Prescription is refillable
luggage Travel See Details
clinical monitoring Clinical Monitoring See Details
sun Sun Sensitivity See Details
not usually stocked Not every pharmacy stocks this drug, so call ahead
prior authorization needed Insurance See Details

Store in temperatures from 59–77°F (15–25°C)

Store it in a dry place and protected from light. Don’t freeze azathioprine and keep it away from high temperatures.

Note: Keep your medications away from areas where they could get wet, such as bathrooms. Store them away from moisture and damp locations.

Travel

When traveling with your medication: 

  • Always carry it with you or in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt this medication.
  • You may need to show your pharmacy’s preprinted label to identify the medication. Keep the original prescription-labeled box with you when traveling.

Clinical Monitoring

Blood tests: Your doctor may do blood tests to check for bleeding disorders once per week during the first month of starting the medication. After that, they may do blood test twice per month for the next two months. They may move blood tests to once per month after that.

Liver and kidney tests: Your doctor may take blood tests periodically to check how well your liver and kidneys are working.

TPMT deficiency: Your doctor may do a blood test to see if you have TPMT deficiency, because this may cause bleeding disorders.

Sun Sensitivity

People taking this medication may have a higher risk of the cancer-causing effects of too much sun exposure. Limit your exposure to the sun. Wear sunscreen and protective clothing, such as a hat and long sleeves.

Insurance

Many insurance companies will require a prior authorization before they approve the prescription and pay for azathioprine.

What does the pill look like?

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Are There Any Alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.


Show Sources

Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on May 26, 2015

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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