Azathioprine and Mercaptopurine

  • Reference Number: HEY-093/2015
  • Departments: Gastroenterology


This leaflet has been produced to give you general information about your treatment.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and your doctor, but may act as a starting point for discussion.   If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team caring for you.

What are Azathioprine and 6-Mercaptopurine?

Azathioprine and 6-Mercaptopurine are immunosuppressant drugs; they are often used in the treatment of inflammatory bowel disease (IBD) when steroid therapy has failed to bring symptoms under control or if you need repeated courses of steroids. They are often mentioned as `steroid sparing agents`.

How do these medications work?

The role of immune system is to fight infections but sometimes the immune system can fight against the body’s own cells causing disease – this forms the basis of use of immunosuppressant drugs in IBD. It is not yet understood fully how immunosuppressant drugs decrease the activity of IBD. The most likely way these drugs work is by reducing the activity of the immune system and thereby reducing inflammation in the bowel.

It may take more than 3 months for the benefit of these medications to become effective and full benefit may not be felt for up to 6 months. These medications do not work in all patients.

Before starting these drugs, your doctor or the specialist nurse will discuss with you in detail regarding the expected benefits and the potential side effects. If you are unsure regarding any of the aspects, you will have the opportunity to ask questions either in person or by using the helpline. Your doctor or specialist nurse will organise some precautionary tests, which may indicate whether you are at higher risk of side effects.

Are there any side effects?

These medications have been in use for over 30 years and are used in other conditions such as rheumatoid arthritis and in general are considered to be well tolerated by the majority of patients. However, as with all medications, there are potential side effects. These include;

  • Nausea / vomiting and loss of appetite.
  • Inflammation of pancreas (pancreatitis) manifested by severe abdominal pain – stop the drug immediately if you develop this.
  • Low white blood cell count.
  • Unusual bleeding / bruising due to low blood counts.
  • Hair loss.
  •  Rashes.
  •  Fever, weakness, fatigue.
  • Jaundice (rare).
  •  See also section on male and female fertility, pregnancy and breast feeding below.

Occasionally, some patients may become prone to infections and very rarely serious infections. There is a small increase in risk of lymphoma (a type of cancer affecting lymphatic system) on use over many years although this may be related to your disease.

What about children and the over 60’s?

There are no particular problems with children receiving these medications. In people over 60 there may be a slight increase in the risk of side effects.

What about monitoring?

Whilst taking this medication it is absolutely essential that you have regular blood test monitoring. A plan on where and who will monitor your blood tests will have to be made before you start these medications. The blood tests will normally be carried out at your GP practice or in the outpatient. Usually you will have your Full Blood Count and Liver Function Test checked.

The standard monitoring regimen is:

  •  Weekly for four weeks (following starting the medication).
  •  Fortnightly for two months.
  •  One to Three monthly thereafter.

The timings may vary slightly from those listed above depending on your individual circumstances. In addition, you may need to have additional or more frequent checks on your blood if there are any suspected side effects. If in doubt contact the IBD helpline overleaf.

Blood monitoring booklets are available so that you can keep a track of your blood test results.

What about male and female fertility, pregnancy and breast feeding?

Azathioprine maybe continued during pregnancy. There have been some reports of low birth weights and also of spontaneous miscarriage in people taking Azathioprine.

The miscarriages have been reported in cases where either the mother or father has taken Azathioprine.

Breast feeding should be avoided whilst taking Azathioprine.

6-Mercaptapurine should NOT be taken during pregnancy or breast feeding.

You should speak to your specialist or IBD nurse if you require further information regarding the benefits and any potential risks of these drugs in pregnancy.

Will Azathioprine and 6-Mercaptopurine react with my other medications?

These drugs do interact with some other medications. The important drugs that may potentially cause harm if used along with Azathioprine or 6-mercapturpurine are:

Allopurinol-for gout Warfarin-blood thinning
Co-trimoxazole- antibiotic Trimethoprim-antibiotic

You should always inform your doctor, nurse or pharmacist before commencing any new medication including herbal or complementary therapies.

Other information

  • Avoid over exposure to sunlight as these medications may make you more sensitive to sunlight, ensure you use sun screen and protective clothing.
  •  Avoid LIVE immunisations (Influenza and Pneumovax II can be taken).
  •  There are no known problems related to alcohol intake but consumption should be within government recommendations.

When should I contact my Specialist Nurse for advice?

  •  If you experience side effects.
  • If you want to alter your dose.
  •  If your blood tests are abnormal.
  • If you have been in contact with anyone with chickenpox or shingles and you are not immune.
  •  If you develop any kind of infection.
  • If you want to start a family / if you or your partner become pregnant / if you want to breast feed.
  •  If you develop a sore throat.
  • If you develop any unusual bleeding or bruising.

Useful Contacts

  •  Crohn’s and Colitis UK –
  • European Federation of Crohn’s and Ulcerative Colitis Associations (EFCCA)

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact IBD Nurse Specialists Tel no: (01482) 608982

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.