What is azathioprine?

Why is azathioprine prescribed?

What are the possible side-effects?

What are the risks?

What else should I know about azathioprine?

What is azathioprine?

Azathioprine is a type of drug known as a disease-modifying anti-rheumatic drug, or DMARD. These drugs have the effect of dampening down the underlying disease process, rather than simply treating the symptoms. Azathioprine reduces the activity of the immune system (the body’s own defence system), which may be overactive in some rheumatic conditions.

What are the brand names of azathioprine?

The biosimilar versions are Imuran and Imuger.

What type of drug is azathioprine?

Azathioprine is a disease-modifying anti-rheumatic drug (DMARD).

What does it do?

It reduces the activity of the body’s defence system (immune system), which may be overactive in some conditions.

What is it used for?

It is used to treat several different types of rheumatic disease, including systemic lupus erythematosus (SLE), rheumatoid arthritis and other autoimmune and inflammatory diseases.

How is it taken?

It is usually given as tablets, taken once or twice daily.

Are there any side-effects?

In some patients azathioprine can cause nausea (feeling sick), vomiting, diarrhoea, loss of appetite, hair loss and skin rashes. It can also make you more likely to develop infections. It can affect the liver or blood so that you need to have regular blood tests while you are taking it.

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Why is azathioprine prescribed?

Azathioprine is used to suppress an overactive immune system in conditions such as systemic lupus erythematosus (SLE), rheumatoid arthritis and other inflammatory diseases. It is also used to prevent the body from rejecting (turning down) the kidney after a kidney transplant.

When and how do I take azathioprine?

Azathioprine is taken in tablet form either once or twice a day. It is usually taken with or after food. Your doctor will advise you about the correct dose.

How long does azathioprine take to work?

Azathioprine does not work immediately. It may be 6–12 weeks before you notice any benefit. Azathioprine may not work right away, so it’s important to continue taking it even if it doesn’t seem to be working at first. You should also continue taking it as prescribed when your symptoms improve and you start to feel better, as this will keep your condition under control.

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What are the possible side-effects?

Azathioprine can cause nausea (feeling sick), vomiting, diarrhoea, loss of appetite (this may be alleviated by taking with food or last thing at night), hair loss and skin rashes. Taking azathioprine can affect the blood count (one of the effects is that fewer blood cells are made) and can make you more likely to develop infections. It can also affect your liver. You should tell your doctor or nurse specialist straight away if you develop any of the following after starting azathioprine:

• a sore throat
• a fever
• any other symptoms of infection
• unexplained bruising or bleeding
• jaundice (eyes or skin turning yellow)
• any other new symptoms or anything else that concerns you.

What should I look out for?

You should stop azathioprine and see your doctor immediately if:

• any of the symptoms listed above are severe
• you have not had chickenpox and you come into contact with someone who has chickenpox or shingles
• you develop chickenpox or shingles

Chickenpox and shingles can be severe in people on treatments that affect the immune system such as azathioprine. You may need antiviral treatment, which your doctor will be able to prescribe.  If you develop chickenpox or shingles, you should contact your doctor or nurse specialist immediately to discuss whether you need to stop your azathioprine temporarily.

There is a slightly increased risk of certain types of cancer with azathioprine. You should discuss this with your doctor.

You should always read the patient information leaflet included with your medicines package to keep you informed about any possible side effects of your prescribed medications.

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What are the risks?

Will it affect vaccinations?

If you are on azathioprine it is recommended that you avoid live vaccines such as yellow fever. However, in certain situations a live vaccine may be necessary (for example rubella vaccination in women of childbearing age), in which case your doctor will discuss the possible risks and benefits of the vaccination with you.

If you are in your 70s and are offered shingles vaccination (Zostavax) you should seek advice from your rheumatology team – you may be able to have the shingles vaccine if you are on a low dose of azathioprine.

Pneumovax (which gives protection against the commonest cause of pneumonia) and yearly flu vaccines do not interact with azathioprine and is recommended. You should speak to your rheumatology team if you are in any doubt about vaccinations.

Can I drink alcohol while on azathioprine?

You should only drink alcohol in small amounts because azathioprine and alcohol can interact and damage your liver. You should discuss this with your doctor.

Does azathioprine affect fertility or pregnancy?

If you are planning a family or become pregnant while taking azathioprine, you should discuss this with your doctor as soon as possible. As with most drugs, it is best to avoid using azathioprine during pregnancy if possible. However, it is also important that the mother’s health is maintained during pregnancy.  Some studies suggest azathioprine does not greatly increase the risk to the baby, so your doctor may suggest continuing with azathioprine to avoid the risk of a flare of your condition.

Does it affect breastfeeding?

Azathioprine may pass into the breast milk. If you are on azathioprine and wish to breastfeed you should discuss this with your rheumatology team beforehand. Though in the past doctors were very cautious about this, more recent evidence suggests that it is safe in most instances.

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What else should I know about azathioprine?

Are there any alternatives?

A number of other drugs are used in the treatment of rheumatoid arthritis and related conditions. Your doctor and rheumatology nurse specialist will discuss these other options with you.

Will I need any special checks while on azathioprine?

Your doctor should order a test for TPMT (thiopurine s-methyltransferase) before starting azathioprine to find out whether you have adequate levels of this enzyme, which helps to break down and remove azathioprine from the body. Low levels of TPMT may mean there is a little more risk of side-effects from azathioprine so your doctor may suggest a lower dose. If the result is very low, azathioprine may not be the right medication for you. Your doctor will discuss your TPMT result with you and explain how it affects your treatment.

Because azathioprine can affect the blood count and can sometimes cause liver problems, your doctor will arrange for you to have a blood test before you start treatment and then regular blood checks while on azathioprine. You may be asked to keep a record of your blood test results in a booklet, and you should take it with you when you visit your GP or the hospital.

You must not take azathioprine unless you are having regular blood checks.

Can I take other medicines alongside azathioprine?

Azathioprine may be prescribed along with other drugs in treating your condition. Some drugs interact with azathioprine (e.g. allopurinol, which is used to treat gout), so you should discuss any new medications with your doctor before starting them, and you should always tell any other doctor treating you that you are on azathioprine. You should also be aware of the following points:

• Azathioprine is not a painkiller. If you are already on a non-steroidal anti-inflammatory drug (NSAID) or painkillers you can carry on taking these as well as azathioprine, unless your doctor advises otherwise. If azathioprine works for you, you may be able to reduce your painkillers or NSAIDs after a time.
• Do not take over-the-counter preparations or herbal remedies without discussing this first with your doctor, rheumatology nurse specialist or pharmacist.

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Page updated 11 May 2021