Azathioprine

Azathioprine has been available for more than forty years. It was developed initially to stop rejection of transplanted organs, such as kidneys, although it is now used to treat a wide range of illnesses. It works by suppressing the body’s own defense system (the immune system), either by itself or in combination with other drugs.

The benefits of suppressing the body's own defense are;


• • 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. 
    
  • After transplant surgery, the immune system has to be suppressed to stop the transplanted organ being rejected.

Conditions best 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 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.

• • 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.
    

What is involved in taking Azathioprine?

• Azathioprine is usually taken for many months or even years. 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
  
• Azathioprine is taken either once or twice a day, with or after food.
  
• Your doctor will advise you on dosage.
  
• Azathioprine is usually taken as a tablet, and doses fall within the range of 50-250 mg per day. The dose prescribed for you will depend on your weight and on the results of blood tests carried out before you start treatment and as part of the regular monitoring of your blood during treatment.

Side effects of Azathioprine treatment

Most patients have few or no side effects. However, potential side effects include nausea, diarrhea, and loss of appetite. Azathioprine can affect the bone marrow (where the blood is made), which may cause anemia, 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, sore throats, mouth ulcers, bleeding and bruising should be reported to your doctor promptly. Azathioprine can also impair the functioning of the liver.

Taking azathioprine for a number of years may increase your risk of getting some types of cancer, including skin cancer, although this is not quantifiable. It is advisable for those taking azathioprine to protect themselves from undue sunlight exposure by modifying their behaviour, wearing suitable clothing and using appropriate sunscreens (with a sun protection factor of at least 30).

Azathioprine can make you more prone to infections. If you have not had chicken pox but have come into contact with a person with chicken pox or 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. Influenza and pneumococcal vaccines, however, are safe and can be recommended. If you need any immunizations it is important that you inform the staff providing these that you are taking azathioprine.

Monitoring for the side effects of Azathioprine treatment

Blood tests (to check the blood count and liver function) 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.

If you are pregnant

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 breastfeed if you are taking azathioprine.

Alcohol and medications while on AzathioprineYes, within reasonable limits.

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.