What is azathioprine and how does it work?

Azathioprine is a drug used to suppress the body’s own defence system (the immune system). It may be prescribed on its own but it can be used in combination with steroid tablets to reduce the amount of steroid required to control symptoms (this is known as a ‘steroid sparing’ effect).   

How long has azathioprine been available?

Azathioprine has been available for more than forty years. It was developed as a “steroid-sparing treatment” for patients who had been given a transplanted organ such as a kidney.  It is now used to treat a wide range of illnesses.

Why suppress the immune system?

There are several reasons:

• In “auto-immune” diseases,  one or more of the body’s organs are attacked by the immune system
• There are also  conditions in which the body’s immune system becomes ‘overactive’ resulting in inflammation, such as atopic eczema.  Suppressing the immune system can then be helpful.
• After transplant surgery, the immune system has to be suppressed to stop the transplanted organ being rejected. .  

Which skin conditions are treated with azathioprine?

Azathioprine is used for conditions in which the immune system is too active or is directed against the body’s own organs. It is only licensed to treat pemphigus vulgaris, systemic lupus erythematosus, and dermatomyositis. However sometimes drugs  are used for conditions not included in the original licence application.  In the case of azathioprine, these are atopic eczema, bullous pemphigoid, pyoderma gangrenosum, chronic actinic dermatitis, and cutaneous vasculitis.

Will azathioprine cure my skin condition?

None of the skin conditions for which azathioprine is used are “cured” by this treatment. Usually a gradual improvement is followed by resolution. However this may take many years.  

How long will I need to take azathioprine?

Azathioprine  is often taken for months or even years, but it is not usually given for short periods as the benefits of treatment are slow to start and may not be apparent  for 2-3 months.

When should I take azathioprine?

Azathioprine is taken either once or twice a day, with or after food. 

What dose should I take?

Your doctor will advise you here.  Azathioprine is usually taken as a tablet, and doses fall within the range of 50 - 250mg per day. The dose you take will depend on your weight and on the results of blood tests carried out before you start the azathioprine treatment and  during the regular monitoring of your blood (see below). 

What are the possible side effects of azathioprine?

Most patients have no side effects.  Side effects that can occur include nausea, diarrhoea, liver damage and loss of appetite. Azathioprine can affect the bone marrow (where the blood is made) and so lead to anaemia, a low white cell count (which carries an increased risk of infection) and a low platelet count (giving an increased risk of bruising and bleeding). Flu-like symptoms, bleeding and bruising should be reported to your doctor promptly. 

Azathioprine can make you more prone to infections.  If you have not had chicken pox, but come into contact with it or with shingles, you should go to your doctor straight away, as you may need special preventative treatment.  You should not be given “live vaccines”, such as oral polio, BCG and rubella (German measles), while you are on azathioprine. Inactivated rather than oral polio vaccine should also be used for other members of your household. Flu vaccines and pneumovax, however, are safe and can be recommended. If you need any immunizations it is important that you inform staff providing these that you are taking azathioprine

What about the risk of late side effects? Are there any other side effects if azathioprine is taken for a long time?

Taking azathioprine for a number of years increases your risk of getting some types of cancer,  including skin cancer although this is not quantifiable.  It is now routine for transplant patients (who usually have to take azathioprine for many years) to limit their sun exposure.  

How will I be monitored for the side effects of azathioprine treatment? 

Blood tests (to check the blood count and the way the liver is working) will be carried out weekly  until a maintenance dose has been reached.   After that blood tests will be less frequent, falling to a minimum of once every three months  while  treatment  continues. It is important that you ensure you attend for your  blood tests as advised by your doctor

Does azathioprine affect fertility or pregnancy?

You should not normally take azathioprine if you are pregnant. You should discuss this with your doctor as soon as possible if you are planning a family, or become pregnant while taking azathioprine. You should not breast feed if you are taking azathioprine. 

May I drink alcohol while taking azathioprine?

Yes, within reasonable limits.

Can I take other medicines at the same time as azathioprine?

Some drugs interact with azathioprine and  care should be taken. These include allopurinol,warfarin, ACE inhibitors (angiotensin converting enzyme inhibitors), co-trimoxazole and sulphasalazine. You should always tell any doctor or pharmacist treating you that you are on azathioprine. Similar caution must apply to drugs sold over the counter and to some herbal remedies.  However, many drugs can  be taken safely with azathioprine. 

Where can I find out more about azathioprine?

If you want to know more about azathioprine, or if you are worried about your treatment, you should speak to your doctor or pharmacist. This information sheet does not list all of the side effects of azathioprine.  For fuller details, look at the drug information sheet which comes as an insert with your prescription for azathioprine.

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