Sounds like 'ay-za-THYE-oh-preen'

Easy-to-read medicine information about azathioprine – what is it, how to take it safely and possible side effects.

Type of medicine Also called
  • Immunosuppressant medication (weakens the body's immune response)
  • Belongs to a class of medicines known as disease-modifying antirheumatic drugs (DMARDs)
  • Imuran®
  • Azamun®
  • Imuprine®

What is azathioprine?

  • Azathioprine is an immunosuppressive medication, which means that it weakens the body's defense system or immune response.  
  • It is used to treat a number of auto-immune conditions related to an 'over-active' immune system such as Crohn's disease, ulcerative colitis, and severe rheumatoid arthritis. Auto-immune means that the body 'attacks' itself, without any real known cause or reason.
  • Azathioprine is also used to suppress transplant rejection in people who have undergone organ transplant surgery. By weakening your immune system it helps your body accept the new organ as if it were your own.
  • Azathioprine will be prescribed for you by a specialist doctor who is experienced in treating your condition.
  • Azathioprine is available as tablets and injection.


  • Always take your azathioprine exactly as your doctor has told you. 
  • The dose of azathioprine will be different for different people.
  • Your doctor will calculate your dose based on your condition, your weight and your response.
  • The pharmacy label on your medicine will tell you how much azathioprine to take, how often to take it, and any special instructions.

How to take azathioprine

  • Take your azathioprine dose once or twice a day, as directed by your doctor. Try to take your dose at the same time each day. 
  • Swallow your tablets with a drink of water.
  • Azathioprine is best taken on an empty stomach, at least 1 hour before or 3 hours after food or milk. But, if you find that azathioprine makes you feel nauseous or sick, or gives you stomach upset, try taking your azathioprine dose after food or at bedtime.  
  • If you forget to take your azathioprine dose, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.    
  • Azathioprine does not work straight away. It usually takes a few weeks or months before you experience the full benefits of azathioprine.   

Special instructions

  • Extra care is needed when taking azathioprine.
  • While you are taking azathioprine you will need to have regular blood tests to monitor for side effects and to determine if the treatment is effective.
  • Since azathioprine weakens your body's defense or immune system, you will be more likely to pickup infections. It is important to avoid anyone who is suffering from chickenpox or shingles. 
  • Azathioprine makes your skin more sensitive to the sun. Protect your skin when you are in the sun, especially between 10 am and 3 pm.
  • If outdoors, wear protective clothing and use a high factor sunscreen (SPF 30+).
  • Make sure you tell anyone providing you with health, dental or medical care that you are taking azathioprine.
  • Do not get pregnant while either you or your partner are taking azathioprine. Speak to your doctor about suitable contraception.

Possible side effects

Like all medicines, azathioprine can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?

  • Feeling sick (nausea)
  • Vomiting
  • Loss of appetite (don't feeling like eating) 
  • These are quite common when you first start taking azathioprine
  • Take your azathioprine with food or in the evening
  • Tell your doctor if troublesome
  • Signs of getting an infection such as feeling unwell, fever, shaking chills  
  • Tell you doctor immediately or ring Healthline on 0800 611 116
  • Signs of changes in your blood cells such as severe sore throat, mouth ulcers, easy bruising, nosebleeds, bleeding gums, short of breath, fever
  • Tell you doctor immediately as you may need a blood test
  • Signs of problems with your liver such as sudden pains in your stomach, loss of appetite, yellowing of the skin and eyes
  • Tell you doctor immediately or ring Healthline on 0800 611 116


  • Azathioprine may interact with a number of medications and herbal supplements so check with your doctor or pharmacist.
  • Also check with a pharmacist before taking over-the-counter anti-inflammatories such as diclofenac (e.g. Voltaren Rapid), ibuprofen (e.g. Nurofen), naproxen (e.g. Naprogesic). Taking these together with azathioprine may increase your risk of side effects.

Learn more

The following links provide further information on azathioprine. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Azamun Medsafe NZ Consumer Information Sheet
Azathioprine Arthritis Research UK
Azathioprine Arthritis Australia

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft. Health Navigator NZ Last reviewed: 15 Jan 2018