Medication Information Leaflet

What is this medication for?

Azathioprine is a medicine that modifies your immune system. It is prescribed for treating conditions such as Systemic Lupus Erythematosus (SLE), inflammatory myositis, uveitis, vasculitis and inflammatory bowel disease. Occasionally, it is also used in the management of rheumatoid arthritis.

How should I take/use this medication?

  • Take azathioprine tablet(s) with or after food to reduce stomach upset. It can cause nausea and vomiting at the start of therapy, but if the dose is increased slowly, your body will usually get used to it.

  • Dosage of azathioprine will depend on your body weight, disease activity and response to the medication.

  • This medicine does not work immediately. It may take between 6 to 12 weeks before you notice any benefit. Thus, it is important that you take your medication regularly, otherwise you may not benefit from the medication at all.

  • Before starting on azathioprine, your doctor may conduct blood some blood test (i.e. TPMT/NUDT) and adjust your medication dose.

  • Do not stop taking your medication without checking with your healthcare professional.

  • Other medications such as corticosteroids, non-steroidal anti-inflammatory drugs (NSAIDs) or disease modifying anti-rheumatic drugs (DMARDs) may be taken with azathioprine.

What should I do if I forget to take/use this medication?

If you miss a dose, take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular dose. Do not take double doses to make up for the missed dose.

What precautions should I take?

Inform your healthcare professional if:

  • You are allergic to this medication or any of the other ingredients of this medication.

  • You plan to start a family or to breastfeed. Azathioprine is generally considered safe in pregnancy.

  • You are taking any other medications, including over-the-counter medicines, supplements, traditional medications and herbal remedies.

If you develop a fever, sore throat or feel generally unwell, see a doctor immediately as you may be more susceptible to infections while on azathioprine. The doctor whom you consult should be told that you are on azathioprine.

What are some common side-effects of this medication?

  • Nausea, vomiting, diarrhoea or loss of appetite

    • Take medication after food to minimise the side effects. Sucking hard, sugar-free candy may reduce nausea and vomiting. Inform your doctor if symptoms are severe or if you experience loss of appetite.

  • Loss of hair

    • This is harmless and may not be obvious. It often resolves spontaneously.

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:

  • Swollen face/eyes/lips/tongue

  • Difficulty in breathing

  • Itchy skin rashes over your whole body

If you experience any of these symptoms, you should stop your medication and see your doctor immediately.

  • Liver disorder (Warning signs: Yellowing of eye whites or skin, dark or tea-coloured urine or constant pain in the lower tummy area)

    • Avoid alcohol. Inform your doctor if you previously had jaundice or hepatitis (liver inflammation).

  • Blood disorder [rare side effect] (Warning signs: May be asymptomatic; unusual bleeding or bruising, lip or mouth ulcers with flu-like symptoms may occur)

    • It is important to monitor the effects of your new treatment, particularly during the first three months of treatment. For your safety, you need to do regular blood tests for monitoring.

What food or medication should I avoid when I take this medication?

  • Avoid going to overcrowded places and eating raw or undercooked food.

  • Pneumococcal and influenza (flu) vaccinations are safe and may be given if required. Avoid live vaccines such as MMR (measles, mumps and rubella), OPV (oral polio vaccine), yellow fever or BCG (tuberculosis). Discuss with your doctor before receiving any vaccines. Also, avoid direct contact with persons who have taken oral polio vaccine or those with infections.

  • Allopurinol and febuxostat (medications for gout) should NOT be taken with azathioprine as it may interfere with removal of azathioprine from the body, increasing its immunosuppressive effects as well as side effects. Let your doctor know that you are on azathioprine if they intend to start any gout medications for you.

  • Do not drink alcohol while on azathioprine as alcohol can increase the risk of liver problems.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack this medication into a black trash bag and seal it tightly before throwing it into the rubbish chute or bin.


If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Jun 2022

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