What is azathioprine and how does it work?

Azathioprine is a drug used to suppress the body’s own defence system (the immune system). Doctors prescribe it for some patients on steroid treatment, so that their steroid dose can be kept at a lower level (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, the immune system attacks the body itself.  These diseases can affect just one organ, such as the heart, liver or skin, or a number of organs.

·      There are also diseases in which the body’s immune system becomes overactive, letting the disease persist or even get worse.  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. Most patients who have had a kidney or heart transplant will take azathioprine as part of the combination of drugs used to suppress their immune system.

Which skin conditions are treated with azathioprine?

Azathioprine is used for conditions in which the immune system is too active. It is only licensed to treat pemphigus vulgaris, systemic lupus erythematosus, and dermatomyositis. However drugs that have been around for decades are often used for conditions not included in the original licence application. With 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 can be 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 appear 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 later during the regular monitoring of your blood (see below). 

What are the possible side effects of azathioprine?

Most patients have no side effects. However some do, and they 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).

Azathioprine can make you more prone to infections; so 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 treatment. You should not be given “live vaccines”, such as polio, BCG and rubella (German measles), while you are on azathioprine.  Flu vaccines and pneumovax, however, are safe and can be recommended.

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. This is true for skin cancer, and it is now routine for transplant patients (who usually have to take azathioprine for many years) to limit their sun exposure. You should talk to your doctor about this if you are worried.

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 for the first four weeks of your treatment, or until a maintenance dose has been reached. Your blood will be tested less often after that, falling to a minimum of once every three months until treatment stops.

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

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

Some drugs interact with azathioprine and should be avoided. These include allopurinol (taken to prevent gout) and warfarin (taken to stop the blood clotting). 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 safely be taken 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.

(While every effort has been made to ensure that the information given in this leaflet is accurate, not every treatment will be suitable or effective for every person. Your own doctor will be able to advise in greater detail)