What is Azathioprine?

Azathioprine is a medication that is classed as a DMARD- a disease modifying anti-rheumatic drug. This means it acts on the disease itself, to reduce the effects of the immune system.

The immune system causes inflammation that protects the body from infections and injury. In certain diseases however, the immune system is over active and this can target healthy tissues such as joints. This results in pain, swelling and tenderness and eventually permanent damage.

Azathioprine works to suppress the over activity of the immune system and prevent the inflammation from occurring, reducing the long-term risk of permanent joint damage.


What is Azathioprine used for?

Azathioprine is used for a number of conditions that cause inflammation around the body, the most common conditions it is used in are Systemic lupus erythematosus, myositis and rheumatoid arthritis.


How is it taken?

Azathioprine is taken as a daily tablet with or without food. The tablets should be taken whole and not crushed.

The medication is processed in the body by a specific enzyme called TPMT. Everybody has different levels of this enzyme in their bodies and to ensure that it is safe for you to take azathioprine, your doctor will check this with a blood test. If the level is low you will not be given azathioprine due to the risk of side effects.

The dose is based on how much you weigh and its started at a low dose initially and gradually increased up. The usual regime that is used is:


Take 50mg daily for 2 weeks

Then 100mg daily for 2 weeks

Then 150mg daily thereafter


It can take up to 12 weeks to have an effect, so it is important you continue to take it even though it may not seem to have any effect straight away.

It is a long-term treatment.


You will receive the first 8 weeks of tablets from the hospital. As the medication can affect the blood counts, liver and kidneys, your blood tests will be checked before you start the tablets and then at intervals during taking it. Initially you will need bloods taken at 2 weeks, 4 weeks and 6 weeks, then once a month for 3 months and then every 3 months whilst you remain on the medication.

Following the initial 8 weeks of monitoring by the rheumatology nurse specialists, they will contact you via the phone to ensure you are managing well and hand over the prescription and blood monitoring to your GP.


Side effects

Occasionally a few people develop side effects when they first start taking azathioprine, these can include:



As the immune system is targeted by azathioprine, it is important to get your blood tests checked. Should you develop signs of infection, stop taking your azathioprine and speak to your GP as you may require antibiotics. Once you are feeling better and have completed any antibiotics you can restart taking your tablets.

Azathioprine can also affect the blood cell counts, liver and kidneys. If you notice any yellow discoloration to your skin or eyes, bruising and bleeding you should let your doctor know.

If you develop, or come into contact with anyone with shingles or chickenpox, you should speak to your doctor as you may need treatment and to stop taking your azathioprine temporarily.


Cautions of use

Interactions with other medications

Contraindications with other conditions


During pregnancy and breastfeeding




Useful Links

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