Azathioprine is used to control severe active RA, usually as an ‘add on’ treatment to supplement the main DMARD or to enable the reduction of regular steroid treatment.  


Azathioprine is used to control severe active rheumatoid arthritis, usually as an ‘add on’ treatment to supplement the main disease modifying drug (DMARD) or to enable the reduction of regular steroid treatment.

Azathioprine is now only used rarely since the continuing development of more effective targeted treatments (see Biologics and Biosimilars, P.46 and 49)

Azathioprine is also used to minimise the possibility of rejection of transplanted organs as well as for other inflammatory conditions.

Azathioprine damps down the immune system by slowing the rate of cell division amongst the inflammatory cells.


Azathioprine has been widely prescribed since the 1960s. The benefit of treatment with azathioprine can take weeks or months to be established.  

Most commonly reported side effects  

As with any medication, azathioprine has a number of possible side effects, although it is important to remember that these are only potential side effects and they may not occur at all.

Close monitoring of weekly blood tests for the first 8 weeks (or as advised) of treatment is very important.

Side effects may include: nausea, vomiting, diarrhoea, throat ulcers, fever, infections, bruising and bleeding but this is not exhaustive.

More information on side effects can be found in the patient information leaflet for azathioprine that comes with your medicine.

Remember to report any concerns about possible side effects to your doctor, pharmacist or nurse.

Azathioprine with other medicines  

There are some significant potential drug interactions between azathioprine and many other medicines. It is particularly important that a full and complete medical history is given to the prescribing doctor.

Remember to take care when using any other medicines or complementary therapies (even if ‘bought over the counter’ for colds, flu or other home remedies). Remember to check with a doctor, pharmacist or nurse that they are safe to take with azathioprine as well as with any other medication taken.

Azathioprine during pregnancy and breast-feeding  

Azathioprine can be prescribed for use throughout pregnancy and while breastfeeding, and can also be used by men whose partners are trying to conceive.

Pregnancy information in this booklet is based on British Society for Rheumatology (BSR) guidelines on prescribing drugs in pregnancy and breastfeeding.

Before starting a family it is recommended that you get advice from the consultant or clinical nurse specialist about when to start a pregnancy.

Azathioprine and immunization/vaccination  

Live vaccines (measles, mumps, rubella (MMR), chickenpox, oral polio (NOT injectable polio), BCG, oral typhoid and yellow fever) cannot be given to anyone already taking azathioprine.

The possible response to killed vaccines (any vaccine that is not ‘Live’) is likely to be diminished because of azathioprine treatment and this results in a reduction of the protection that the vaccination provides.

The annual flu vaccination and ‘pneumovax’ protection against pneumonia is permitted. If possible the ‘pneumovax’ vaccination should be given before starting azathioprine.

Medicines in rheumatoid arthritis

We believe it is essential that people living with RA understand why certain medicines are used, when they are used and how they work to manage the condition.


Updated: 01/09/2020