Azathioprine is a drug used to treat both Crohn’s Disease and Ulcerative Colitis – the two main forms of Inflammatory Bowel Disease (IBD). You may be given azathioprine if you keep getting flare-ups even though you are on other medicines for your Crohn's or Colitis, or to help you cut down on steroids. You may be also be given azathioprine soon after diagnosis if your Crohn's or Colitis is troublesome to start with.
Azathioprine may be known by a brand name, such as ‘Imuran’. There is another drug similar to azathioprine which is prescribed by some hospitals called mercaptopurine. Mercaptopurine can sometimes be used in people who cannot tolerate azathioprine. In general, the information below can be applied just as much to mercaptopurine as azathioprine.
Azathioprine is an immunosuppressant, meaning it suppresses (damps down) the over-active cells in your immune system. While this helps to reduce and control the inflammation in your digestive system (gut) it can also place you at higher risk of infections.
Azathioprine usually comes as round yellow tablets, in two sizes: 25 mg and 50 mg. The colour of the tablets, however, can vary.
Your doctor or specialist nurse will tell you how much azathioprine you need to take and how often. This will depend on your age and weight, and how ill you are. The way tablets need to be taken varies according to the drug and its formulation, making it important to take the medicine exactly as your doctor tells you. Avoid taking mercaptopurine with cow’s milk which contains chemicals that may inactivate the drug. You may be started on a lower dose and then gradually build up to your full dose.
No, azathioprine is a slow-acting drug and it can take several months before you start to feel better. But if it works well for you, you may be able to keep taking it for several years, or as long as you don’t get any serious side effects.
Azathioprine affects the way your body produces new blood cells. It can also affect your liver. A blood test before you start azathioprine and then regular blood tests while you are on azathioprine can check if this is happening. You will probably start off with weekly blood tests, changing to monthly tests as your dose builds up and you get used to azathioprine. Eventually you will probably only need tests every two or three months. You will also need to have your kidneys monitored every six months to check that azathioprine has not affected them. Your doctor or specialist nurse will make sure you have all the correct tests before and while you are on your treatment.
Azathioprine has an established record in settling down inflammation and therefore symptoms in patients with Crohn’s Disease or Ulcerative Colitis, but as with all drugs it can occasionally cause side effects. Your doctor or nurse will talk you through the benefits of taking azathioprine and the side effects it might cause before you start your treatment. Not everybody gets side effects with azathioprine and some of these side effects may go away as your body gets used to it. However, you may notice side effects such as:
- Nausea (feeling sick), vomiting, and a loss of appetite, especially during the first few weeks of treatment
- A flu-like illness with fever and general aches and pains
- Weakness and breathlessness and a tendency to bruise or bleed easily
- Yellowing of the skin, which is a sign of jaundice and may mean you have liver inflammation. This is uncommon.
- Pain in your stomach that could mean that your pancreas has become inflamed (pancreatitis)
- Very occasionally, dizziness, hair loss and skin rashes.
- Tell your doctor or IBD team if you notice any of these symptoms. It may be that a change in how you take azathioprine can help. Or it may mean azathioprine doesn’t suit you.
- Azathioprine may help to make some cancers less likely – but it can also make it slightly more likely that you might develop:
- Lymphoma - a type of cancer affecting the lymph glands
- Some types of skin cancer (non melanoma skin cancer which is generally not life threatening) - see below for what you can do to help reduce this risk.
Your regular blood tests will help pick up if you are developing problems like these or inflammation in your liver or pancreas. If you have any concerns about cancer, this is something that can be discussed with your IBD team.
- Avoid close contact with people with infections - and tell your doctor or IBD team if you have an infection that is not getting better, even if it is a simple cold, sore throat or chill. Because azathioprine is an immunosuppressant it means you are more likely to catch infections like colds and flu, and that simple infections like these may make you quite unwell if you don’t get them treated.
- Have an annual flu vaccination. This will help protect you from flu and is safe to have because the flu vaccine is a ‘killed’ inactive vaccine. You should not have any ‘live’ vaccines like those used in the new nasal spray flu vaccine for children, MMR, rubella or BCG (tuberculosis) vaccinations
- Tell your doctor if you come into close contact with anyone who has chickenpox, shingles, measles or pneumonia. These infections can make you quite unwell if you are on azathioprine. Your doctor may be able to give you a protective injection before you start your treatment.
- Use a strong sunscreen (factor 50 or above) and wear a hat and light clothing when out in bright sunlight. Azathioprine makes your skin more sensitive to sunlight and simple precautions like these can help reduce the risk of skin cancer. Don’t use a sun bed!
- Always check with your doctor or IBD team before you start taking any new medicines, even over the counter medicines, herbal medicines, complementary or alternative medicines. Some medicines, including certain antibiotics, can interact with azathioprine.
- If you go to another doctor or a dentist for treatment, tell them you are taking azathioprine. This is because if they don’t know, they might give you a medicine that will interact with azathioprine.
- Regular blood tests are essential when taking azathioprine. The frequency of these will vary depending on your local hospital. Always ensure you keep
- up-to-date with your blood tests as they may pick up any side effects from the medication.
- Only drink alcohol in moderation. While alcohol is not known to have any interaction with azathioprine, both alcohol and azathioprine can affect the liver. Anecdotal reports suggest that combining alcohol and azathioprine can lead to ‘extreme hangovers’ the next day.
For further information about azathioprine and mercaptopurine, see our information on Azathioprine and Mercaptopurine. If you have any worries or concerns, even if you feel it’s just a small thing, talk to your IBD doctor or specialist nurse. They will be happy to help you with any questions about your Crohn's or Colitis or your treatment.
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Last reviewed: April 2016