Azathioprine for Crohn's disease and ulcerative colitis

Azathioprine is a medication used in the treatment of inflammatory bowel disease (IBD) - such as Crohn’s disease and ulcerative colitis. It is also used by people with rheumatoid arthritis as well as other inflammatory conditions or following an organ transplant.

In general azathioprine is not one of the first medications used by IBD patients when they are first diagnosed. It has been used by people with Crohn’s disease and ulcerative colitis since the 1960s and is thought to be prescribed to around 1 in 5 patients with IBD.

What is azathioprine?

Azathioprine is part of a group of medications known as thiopurines which are immunosuppressants. This means that azathioprine works to reduce the activity of your immune system. In IBD the immune system is attacking the digestive system which results in inflammation. Azathioprine reduces the number of white blood cells in the body - the immune system relies on these white blood cells and by reducing them it interrupts the immune system’s function. It is chemically very similar to mercaptopurine, although azathioprine is used more often in IBD.

It is a slow-acting drug and can take 3-6 months before any effect is noticed. People are sometimes given azathioprine if they are having difficulty coming off of corticosteroids or as a follow-on from steroids. This allows the dose of steroids to be reduced as the azathioprine takes effect. It may also be used in combination with other medications such as biological drugs infliximab and adalimumab. This is known as combination therapy.

Some people aren’t able to tolerate azathioprine due to high levels of enzymes which can lead to side effects. These people may be given allopurinol to take as well. This drug helps to correct the enzyme imbalance. However, allopurinol can interact with azathioprine so you should only take it if you are prescribed it by your doctor.


How is azathioprine taken?

Azathioprine comes in tablet form which is usually taken once daily with or after food. The dosage will be individual to you depending on the severity of your IBD, your height, weight etc.

Before taking it you will go through some screening tests to check the levels of the enzyme thiopurine methyl transferase (TPMT). Higher levels of TPMT may mean you are more likely to experience side effects. You may also be screened for immunity to some viruses and infections as your immune system function is lower when taking azathioprine.

What are the different types of azathioprine available?

There are different brands of azathioprine available. These include:

  • Imuran
  • Azafalk
  • Azapress

Are there any potential side effects of azathioprine?

As with any medication there are potential side effects of taking azathioprine. You may not experience any of these side effects listed. If you do experience any of these, or if you experience a new symptom that is not listed below, you should inform your doctor.

Reported side effects include:

  • An increased risk of infections. Azathioprine works to reduce your immune system. This means you may be more susceptible to infection and illness.
  • Nausea and vomiting
  • Loss of appetite
  • Inflammation of the pancreas (pancreatitis)
  • Yellowing of the skin and eyes (jaundice)
  • Problems with liver
  • Hair loss
  • Diarrhoea or fatty stools
  • Allergic reaction to the drug which may include dizziness, nausea, vomiting, diarrhoea, fever, shivering, skin rash or pain in muscles or joints
  • Lung inflammation (pneumonitis)
  • Increased risk of certain types of cancer (lymphomas, cancer of cervix/vulva and skin cancer)

Is there anything I should know before taking azathioprine?

  • You will need regular monitoring blood tests. As azathioprine reduces the number of white and red blood cells, as well as platelets you will need blood tests to check levels
  • You will be more sensitive to sunlight. You should avoid sunbeds, strong sunlight and use suncream with a high SPF
  • You may get ill more. As azathioprine suppresses the immune system you may find that you pick up more colds, coughs, infections and other illnesses and find it hard to get rid of them or they may develop into more serious illnesses. You should also avoid contact with people who have illnesses such as chicken pox
  • If you are male or female taking azathioprine and want to have a baby you should discuss this with your doctor before getting pregnant or if you find out you or your partner are pregnant. Manufacturers recommend patients or their partners who are pregnant or likely to get pregnant should not take the drug. However, experts believe it can be taken where the benefits outway the risks
  • If you have liver or kidney problems you should inform your doctor and you may need to be monitored while taking the medication or be given different medication
  • You can be allergic to azathioprine. The symptoms of an allergy are listed in the section above
  • If you are taking other medication you should inform your doctor. This includes all medication for IBD, any other prescribed medication, over-the-counter and herbal medicines. Azathioprine can interact with some other drugs
  • You shouldn’t have any live vaccines while taking azathioprine or within six months of stopping. These include vaccines for polio, yellow fever, tuberculosis, German measles and MMR (measles, mumps and rubella). You can have a flu vaccine as long as it is the inactivated version
  • Azathioprine is often used as a long-term maintenance drug (to keep someone in remission). It is not known to reduce in effectiveness over time. Some people remain on it indefinitely

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