Azathioprine, Azasan

Introduction

Written by Sarah Lewis, PharmD
Medically reviewed by Alex Brewer, PharmD, MBA
Updated on August 18, 2023

Azathioprine (ay za THYE oh preen) is a generic medication prescribed for after a kidney transplant or to treat rheumatoid arthritis. Azathioprine belongs to a group of drugs called immunosuppressants.

Boxed warning: Risk of cancer

Azathioprine has a boxed warning about an increased risk of cancer. Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA).

For details, see the “Interactions and warnings for azathioprine” section.

Side effects of azathioprine

Azathioprine may cause mild or serious side effects. More common mild side effects of azathioprine and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

Ask your doctor or pharmacist to learn more about azathioprine’s side effects. You can also refer to the prescribing information for azathioprine listed in the “Resources” section.

Mild side effects

More common mild side effects reported with azathioprine are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about azathioprine’s side effects, refer to the prescribing information for azathioprine listed in the “Resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Mild side effects for azathioprine oral tablet and liquid solution for injection include:

• diarrhea
• nausea
• vomiting
• mild allergic reaction*

* For details about this side effect, see the “Interactions and warnings for azathioprine” section.

Serious side effects

Serious side effects of azathioprine are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about azathioprine’s side effects based on the form, refer to the prescribing information for azathioprine listed in the “Resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, azathioprine’s serious side effects include:

• hair loss
• liver damage
• pancreatitis (inflammation of the pancreas)
• reversible lung problems
• serious infection
• severe low blood cell counts
• Sweet’s syndrome (a rare inflammatory skin condition)
• boxed warning: increased risk of cancer*
• severe allergic reaction*

* For details about this side effect, see the “Interactions and warnings for azathioprine” section.

Uses of azathioprine

The Food and Drug Administration (FDA) approves prescription drugs such as azathioprine for certain conditions. Approved uses for azathioprine are described below.

Use for helping prevent rejection after kidney transplant

Doctors may prescribe azathioprine oral tablet and liquid solution for injection* to help prevent organ rejection after a kidney transplant. It’s used for this purpose in adults. It’s usually prescribed as a long-term treatment.

With a kidney transplant, you get a kidney from a donor. In some cases, the immune system may not accept the kidney and may attack it. It does this because it responds to the kidney as something foreign in your body. This is called rejection.

Symptoms of organ rejection can include fever, flu-like symptoms, swelling, and very high blood pressure.

Azathioprine is prescribed together with other medications that help prevent organ rejection after a kidney transplant.

* This medication is given as an injection or infusion into a vein.

Use for rheumatoid arthritis

Doctors may prescribe azathioprine oral tablet and liquid solution for injection* to treat rheumatoid arthritis (RA). It’s used for this purpose in adults. It’s usually prescribed as a long-term treatment.

With RA, the immune system attacks healthy joint tissues by mistake. This causes joint inflammation and damage. Symptoms can include swollen, painful, and stiff joints. Other symptoms may include fever and fatigue (low energy).

Azathioprine may be prescribed together with other drugs for RA treatment. Examples are aspirin, nonsteroidal anti-inflammatory drugs, or low dose corticosteroids.

Doctors may not prescribe azathioprine oral tablet or liquid solution for injection in certain situations. This includes for people who have already taken certain drugs called alkylating agents.

* This medication is given as an injection or infusion into a vein.

Common questions about azathioprine

Below you’ll find answers to a few commonly asked questions about azathioprine.

What is azathioprine’s mechanism of action? How does the drug work?

Azathioprine works by lowering the level of activity in the immune system. For people who have had a kidney transplant, this helps prevent the immune system from attacking the involved kidney. For people with rheumatoid arthritis (RA), this stops the immune system from attacking the joint tissues.

Azathioprine will start to work as soon as you take it. But it can take up to 12 weeks to experience the full effect. For people with RA, symptoms may start to ease within about 4–8 weeks.

If you’d like to know more about this, talk with your doctor or pharmacist.

Are there brand names available for azathioprine?

Azathioprine is available as the brand-name drugs Azasan and Imuran.

A generic medication is an identical copy of the active drug in a brand-name medication. (An active drug is the ingredient that makes a medication work.) Generic drugs are believed to be as effective and safe as brand-name drugs. And generic drugs usually cost less compared with brand-name drugs.

To learn more about these brand-name products, talk with your doctor or pharmacist.

Interactions and warnings for azathioprine

Below, you’ll find information about azathioprine’s possible interactions and warnings.

Interactions of azathioprine

Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take azathioprine, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription or over-the-counter drugs
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for azathioprine” section below.

Warnings for azathioprine

Some people should not take azathioprine, and others should take it cautiously.

Boxed warning: Risk of cancer

Azathioprine has a boxed warning about an increased risk of cancer. Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA).

Taking azathioprine can make it more likely for someone to develop certain cancers. This is because the drug suppresses the immune system. These cancers include skin cancers and blood cancers called lymphoma and leukemia.

Symptoms of cancer will vary depending on the type involved. Skin cancers can cause new areas of damaged or unusual skin to appear, or they can cause changes to existing moles. Leukemias and lymphomas can cause fever, night sweats, weakness, frequent infections, and other symptoms.

If you experience any concerning symptoms, tell your doctor. They’ll likely recommend tests to determine the cause. Your doctor can also recommend ways to help monitor for cancer, such as having routine skin exams.

To learn more, talk with your doctor or pharmacist.

Other warnings

Azathioprine could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether azathioprine is a safe option for you.

Ask your doctor about specific warnings for azathioprine, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Azathioprine can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to azathioprine or any of its ingredients, your doctor will likely not prescribe azathioprine. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

In addition, a rare allergic reaction that causes severe nausea and vomiting has happened in people taking azathioprine. This reaction can also include other symptoms such as skin rash, fever, and joint pain.

This reaction is most likely during your first few weeks of treatment with azathioprine. And the symptoms go away once treatment is stopped. Call your doctor right away if you experience nausea or vomiting that is severe.

If you have an allergic reaction to azathioprine, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of azathioprine

If you take azathioprine by mouth, you should not take more azathioprine than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.

If you think you’ve taken too much azathioprine, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Pregnancy or breastfeeding and azathioprine

Information about azathioprine and pregnancy and breastfeeding is described below.

Azathioprine and pregnancy

Azathioprine should not be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication. Your doctor may suggest birth control options to use during treatment with azathioprine.

Azathioprine and breastfeeding

Azathioprine should not be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication. Your doctor may recommend other ways to feed your child during treatment with azathioprine.

What to ask your doctor

Let your doctor know if you have questions about azathioprine or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• How does azathioprine compare with other medications that could treat my condition?
• How often will I need lab tests while taking azathioprine?
• How can I reduce the risk of side effects such as infection and skin cancer?

Resources

• Azathioprine sodium for injection, USP. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/9ffe79a1-ac91-4a7b-a9e3-7c84bfa9ddf0/spl-doc
• Azathioprine tablets, 50 mg. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/ceab8e8b-d022-4d0c-a552-cc5782446248/spl-doc
• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm

Disclaimer: Optum Perks 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 another 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.