Azathioprine (Imuran)

What is it?
Azathioprine is a drug that affects the immune response in the body (i.e. an immunosuppressant).

Indications for use
The main use is in organ transplantation to prevent rejection of the donor organ. However, it has proved beneficial in patients with severe chronic inflammatory bowel disease which has not responded to steroids alone, or in patients who are dependent on high dose steroids to control symptoms. It is useful in those patients who frequently relapse on reducing the dose of steroids and thus has a steroid sparing effect.

How is it taken?
It is taken as a tablet that must be swallowed whole with plenty of water. The dosage is calculated according to your body weight - usually 2 mg per kg, however your doctor will tell you the correct dose for you.

The tablets may be taken altogether, although taking them in divided doses and after meals may reduce any associated nausea.

You will not usually notice any effects straight away, as it can take up to 6 weeks before it begins to work and the real benefits may not be noticed for 3 months or more. For this reason treatment is often commenced in conjunction with oral steroids for more immediate relief of symptoms with the dose gradually being tapered as the Azathioprine begins to exert its effect.

Due to the potential risk of treatment on the bone marrow and the liver, it is extremely important to have regular blood checks whilst taking the treatment. The type and frequency of monitoring should be as follows:
Full blood counts and liver function tests on a weekly basis for the first 2 months, then 3 monthly thereafter whilst taking the treatment.

Results should be recorded in the monitoring book given to you by the doctor. Tests can be carried out at the hospital or GP surgery, but it is important that the doctor, or nurse, tells you that it is safe to continue.

You should not take this drug if you have previously had a reaction to this or to 6 mercaptopurine.

*Special precautions
If you are considering becoming pregnant, or become pregnant whilst taking treatment, speak to your doctor or nurse as soon as possible. Your doctor may well tell you to continue treatment, particularly if you have troublesome disease that has only been under control on this treatment. If you are planning a pregnancy, and you have been in remission for some time, you may be advised to try stopping treatment before trying to become pregnant.

Treatment should not be initiated during pregnancy.

Azathioprine should be stopped in all but minor infections as the body defences may be reduced and delay your recovery or cause a worsening of the condition. Speak to the nurse or doctor before stopping any treatment and you will be advised when it is safe to restart.

Are there any side effects?
Azathioprine can be very effective in providing remission from the symptoms caused by inflammatory bowel disease, and in allowing smaller doses of steroids to be used effectively whilst reducing the risk of relapse and steroid induced side effects. However it is possible that some side effects may occur during treatment. Symptoms, such as diarrhoea, nausea, mild aches and pains may occur initially but should settle within 2 weeks. Others, which are potentially more serious, may occur. These may include some of the following:
• Feeling generally unwell
• Dizziness
• Vomiting
• Fever
• Rigors
• Muscle pains
• Joint pains
• Abnormal liver function
• Jaundice
• Disturbances in heart rhythm
• Low blood pressure
• Kidney problems
• Skin rash

These may be due to a hypersensitivity reaction and you may need to stop the treatment. You must contact your doctor or IBD nurse immediately for further advice.

Other reactions may occur such as:
• Reduced bone marrow activity i.e. low white cells [neutrophils are particularly important in fighting infection], low platelets [important in helping the blood to clot], low haemoglobin [iron in the blood].
• Hair loss

These may respond to a dose reduction or temporarily stopping treatment and reintroducing at a lower dose.

It may rarely cause inflammation of the pancreas or lungs. This is reversible on stopping treatment, but the drug should not be restarted on recovery.

Although these side effects may sound quite alarming, many patients manage to take the drug safely with little, or no, trouble. You should be reassured that you will be monitored closely whilst taking this treatment and that if side effects do arise, they will be dealt with accordingly.

Your compliance with the monitoring programme is essential in the safety of your treatment.

Are there any interactions?
Azathioprine may react with other drugs and it is therefore important that you tell your doctor about any other tablets you may be taking. You should not start any new medication before discussing this with your doctor or IBD nurse first. Interactions include:

• Allopurinol- given for gout. Enhances the effect and therefore, increases the toxicity of Azathioprine. However it has recently been suggested that by giving small doses of azathioprine together with allopurinol, the beneficial effects may be achieved using a smaller dose and thus reducing the risk of side effects.
• Antibacterials - given to treat infection e.g. rifampicin.