Azathioprine

What is azathioprine?

Azathioprine is a prescription-only medicine used to suppress the immune system and relieve symptoms of various conditions. It is classed as an immunosuppressant, commonly used when the immune system needs to be reduced – such as after an organ transplant or in certain autoimmune conditions[1]. 

What is azathioprine used for?

Azathioprine is used to treat many autoimmune conditions such as rheumatoid arthritis, Crohn’s disease, ulcerative colitis, lupus and myasthenia gravis. It may also be prescribed for skin conditions, such as eczema and pemphigus, severe liver, skin, or artery inflammation, or to prevent organ rejection following a transplant, such as a kidney or liver transplant[1]. 

How does azathioprine work?

Azathioprine works by interfering with the production of DNA in immune cells. This action reduces the activity of the immune system – helping to control inflammation and prevent it from attacking the body’s own tissues[1]. 

Who can take azathioprine?

Azathioprine can be taken by most adults and some children. However, it may not be suitable for people who[1]: 

• Have liver or kidney problems 

• Have a condition that affects the bone marrow 

• Have a history of cancer 

• Are due to have surgery 

• Have Lesch Nyhan syndrome 

• Have any unusual bleeding or bruising 

• Are pregnant or breastfeeding  

• People with untreated infections. 

People with a deficiency in an enzyme called TPMT (thiopurine methyltransferase), which is needed to process the medicine, may be recommended an alternative treatment other than azathioprine[1].  

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].  

How do you take azathioprine?

Azathioprine is normally taken once or twice per day. It should be taken at the same time each day, preferably after food to reduce nausea, by swallowing tablets whole with water. Do not crush or chew them as this may change or limit how they work[1]. 

What is the typical dosage of azathioprine?

The usual dose of azathioprine varies depending on your condition. Treatment usually starts with a low dose, which can then be increased gradually according to how you react. After a transplant, the usual dose is between 1mg and 2.5mg for each kilogram you weigh (1 to 2.5 mg/kg), taken daily. For anything else, the usual dose is 1mg to 3mg for each kilogram you weigh (1 to 3 mg/kg), taken daily. Regular blood tests are required to monitor your response and check for side effects while you are taking this medication[1]. 

Can you stop taking azathioprine suddenly?

You should not stop taking azathioprine suddenly unless your doctor tells you to. Stopping it abruptly could cause your condition to flare up. Instead, if you need to stop, your doctor will advise you how to do so gradually and safely[1]. 

What should you do if you take too much azathioprine?

Taking too much azathioprine can be dangerous, and the symptoms of overdose may include nausea, vomiting, diarrhoea, and an increased risk of infection. If you think you or anyone else has taken too much, get immediate medical attention by calling 999 or going to A&E[1]. 

What should you do if you forget a dose of azathioprine?

If you forget to take a dose, take it as soon as you remember. If it is nearly time for your next dose, you can skip the one you missed and continue from the next one. Do not take two doses at once to make up for a missed dose[1]. 

What medicines should you avoid while taking azathioprine?

Azathioprine can interact with other medicines, particularly[1]: 

• Allopurinol, which is used to treat gout 

• Warfarin, a blood thinner 

• Immunosuppressants like ciclosporin or tacrolimus 

• ACE inhibitors used for blood pressure 

• Some antibiotics, including co-trimoxazole 

• Live vaccines, such as yellow fever 

• Chemotherapy 

• Any recent or upcoming vaccinations 

However, you can usually take over-the-counter painkillers like paracetamol and non-live vaccines alongside azathioprine. 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of azathioprine?

The most common side effects when taking azathioprine include feeling sick or nauseous, a loss of appetite, increased risk of infections, and feeling tired or dizzy[1]. 

There are also some more serious side effects. If you experience any of the following while taking azathioprine, seek medical attention[1]: 

• Yellowing of the skin or eyes (jaundice) 

• Unexplained bruising or bleeding 

• Severe stomach pain or back pain 

• Tiredness, dizziness or sore joints and muscles 

• Confusion or weakness 

• Lumps on your body 

• Vomiting or diarrhoea 

• Signs of infection such as a high temperature or sore throat 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

Symptoms of anaphylaxis include[1]:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional. 

Frequently asked questions about azathioprine

How long does azathioprine take to work? 

When you start taking azathioprine it usually takes between six and twelve weeks to start working at its best[1]. 

Can I drink alcohol while taking azathioprine? 

Yes, you can safely drink alcohol while taking azathioprine – but only in moderation. Avoid heavy drinking as this can detrimentally affect the liver[1]. 

Is azathioprine safe during pregnancy? 

Azathioprine may be used during pregnancy if it’s been prescribed by a specialist. Do not take it unless advised by your doctor or pharmacist that it is safe to do so[1]. 

Can I take azathioprine with food? 

Yes, you can take azathioprine with food, and it is often recommended to reduce nausea[1]. 

Do I need regular blood tests while taking azathioprine? 

Yes, regular blood tests are needed while you take azathioprine. This is to check your liver function and blood count while taking the medicine[1]. 

Can I get vaccines while on azathioprine? 

You should avoid live vaccines when you’re on azathioprine. Most non-live vaccines are safe – but always check with your doctor or pharmacist[1]. 

Will azathioprine affect my fertility? 

Azathioprine may reduce fertility in men, which can be a potentially concerning side effect. Speak to your doctor or pharmacist if this is a concern[1]. 

Can I take herbal supplements while taking azathioprine? 

It’s best to check with your doctor or pharmacist before taking any herbal or dietary supplements that may interact with azathioprine[1]. 

What if I feel unwell while taking azathioprine? 

If you’re feeling unwell while taking azathioprine, contact your doctor or pharmacist for advice. This is especially true if you have signs of infection or any unexplained symptoms[1]. 

Is azathioprine a lifelong medication? 

Some people and conditions require azathioprine in the long term. Meanwhile, others may only need to take it for a limited period[1]. 

For the official NHS guide to azathioprine, visit their website.