Azathioprine

Sounds like 'ay-za-THYE-oh-preen'

Key points about azathioprine

  • Azathioprine is used to treat autoimmune conditions including Crohn's disease, ulcerative colitis, rheumatoid arthritis and autoimmune liver disease.
  • Azathioprine is commonly called Imuran or Azamun.
  • Find out how to take it safely and possible side effects.
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Azathioprine is an immunosuppressant medicine, which means it weakens your body’s defence (immune) response. It's used to treat several autoimmune conditions related to an ‘overactive’ immune system. Autoimmune means that your body ‘attacks’ itself, without any real known cause or reason. 

  • Crohn's disease and ulcerative colitis – azathioprine helps to reduce flareups. 
  • Rheumatoid arthritis – azathioprine helps to slow down the disease and its effects on your joints rather than just treating the symptoms of pain and swelling. 
  • Autoimmune liver disease – azathioprine helps to reduce inflammation in the liver and prevent scarring (fibrosis) and cirrhosis.

Azathioprine is also used to stop transplant rejection for people who've had an organ transplant surgery.

In Aotearoa New Zealand azathioprine is available as tablets (25 mg and 50 mg) and as an injection (but this is usually only given in hospital). 

  • The dose of azathioprine is different for different people, depending on what it's being used for, your weight and how well it's working.
  • Always take your azathioprine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it and any special instructions.

  • Timing of your doses: Try to take your dose at the same time each day. Azathioprine is best taken on an empty stomach, at least 1 hour before or 3 hours after food or milk. 
  • Swallow your tablets whole with a drink of water: Don't break, chew or crush the tablets.
  • Missed dose: If you forget to take your azathioprine dose, take it as soon as you remember. But if it's nearly time for your next dose, take the next dose at the right time. Don't take double the dose.    
  • Keep taking azathioprine regularly: Azathioprine doesn't work straight away. It usually takes a few weeks or months before you notice the full benefits.  

Here are some things to know when you're taking azathioprine. Other things may be important as well, so ask your healthcare provider what you should know about.


Tests and monitoring

Azathioprine weakens your immune system, making it harder for your body to fight infections. Before you start azathioprine, you may need tests to make sure you don't have any infections such as tuberculosis (TB), HIV, hepatitis B or hepatitis C.

While you're taking azathioprine, you will need regular blood tests to monitor for side effects and to check whether the treatment is working. Blood tests are very important during the first few months of treatment. Over time, these tests are needed less often.


Risk of infections

Azathioprine weakens your body’s defence (immune) system, so you are more likely to pick up infections. It's important to avoid anyone who has chickenpox, shingles or measles.


Vaccinations

Azathioprine makes your immune system weaker, putting you at increased risk of infections. Vaccines are a good way to prevent some infections. You should have all the vaccinations you need before you start treatment with azathioprine, because some vaccines shouldn't be taken while you're taking azathioprine. Always check with your doctor or pharmacist first. It's safe for you to have the annual flu vaccine. Keep your flu vaccinations up to date to reduce your risk of getting the flu.


Other medicines

Azathioprine may interact with a few medicines and herbal supplements, so check with your doctor or pharmacist before starting azathioprine or before starting any new medicines, including those you may buy over the counter.


Sun protection

Azathioprine makes your skin more sensitive to the sun. Protect your skin when you're in the sun, especially between 10am and 3pm. Wear protective clothing and use a high factor sunscreen (SPF 30+) when you're outside.


Pregnant or planning a pregnancy

You should avoid becoming pregnant while you or your partner are taking azathioprine. Discuss with your healthcare provider which types of contraception are suitable for you both.

Like all medicines, azathioprine can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Feeling sick (nausea)
  • Vomiting (being sick)
  • Loss of appetite (don't feel like eating) 
  • This is quite common when you first start taking azathioprine.
  • Try taking it with food.
  • Tell your doctor if these bother you.
  • Signs of getting an infection, such as feeling unwell, fever or chills  
  • Tell your doctor immediately or phone Healthline on 0800 611 116.
  • Signs of changes in your blood cells, such as a severe sore throat, mouth ulcers, easy bruising, nosebleeds, bleeding gums, shortness of breath or fever
  • Tell your doctor immediately or phone Healthline on 0800 611 116.
  • Signs of problems with your liver, such as sudden pains in your stomach, loss of appetite or yellowing of your skin and eyes
  • Tell your doctor immediately or phone Healthline on 0800 611 116.
  • Signs of an allergic reaction such as skin rash or swelling of your lips, or problems breathing. 
  • Tell your doctor immediately or phone Healthline on 0800 611 116.
For more information on side effects, see the Medsafe consumer information leaflets Azamun(external link) and Imuran(external link).

Read more about medicines and side effects and reporting a reaction you think might be a side effect.

Ulcerative colitis | Mate kōpiro nui
Rheumatoid arthritis | Mate rumatiki
Crohn's disease | Mate whēkau pauku
Autoimmune disease topics

The following links have more information about azathioprine. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

Azathioprine(external link) (Azathioprine for transplant patients(external link)) NZ Formulary
Azathioprine(external link) RheumInfo
Azamun(external link) Consumer Information Sheet, Medsafe, NZ
Azathioprine(external link) Australian Rheumatology Association

References

  1. Azathioprine(external link) NZ Formulary
  2. Azamun(external link) Data Sheet, Medsafe, NZ

Brochures

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5 questions to ask about your medications

5 questions to ask about your medications

Health Quality and Safety Commission, NZ, 2019 English, te reo Māori

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

Last reviewed:

Read more at: https://healthify.nz/medicines-a-z/a/azathioprine/
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