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
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
You should not take this drug if you have previously had a reaction
to this or to 6 mercaptopurine.
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.
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:
• Muscle pains
• Joint pains
• Abnormal liver function
• 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:
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.