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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.
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.
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.
There are different brands of azathioprine available. These include:
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:
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