Azathioprine

What azathioprine is for

Azathioprine is a type of medicine called a DMARD (disease-modifying anti-rheumatic drug).

DMARDs are immunosuppressants, which means they work by calming your immune system or changing the way it responds.

It's used to treat autoimmune conditions, where your body's natural defence system mistakenly attacks healthy parts of your body, such as:

• Crohn's disease and ulcerative colitis
• rheumatoid arthritis
• lupus
• myasthenia gravis

It's also used to help your body accept a new organ if you've had an organ transplant and is sometimes used to treat severe skin conditions.

How to take azathioprine

Azathioprine comes as tablets or a liquid you swallow (oral solution).

You usually take it once a day, but how much you take and for how long depends on why you're taking it. Your doctor will explain your dose to you.

When taking azathioprine:

• swallow tablets whole with a drink of water
• use the cup or measuring spoon that comes with the liquid medicine to measure the correct dose
• you can take the tablets with or without food, but avoid having milk or other dairy products from 1 hour before taking them until 2 hours afterwards
• avoid having a meal, milk or other dairy products from 1 hour before taking the liquid medicine, until 2 hours afterwards
• use sunscreen, avoid intense sunlight, and wear a hat and clothes that cover your arms and legs and if you're going to be outdoors – the medicine can make your skin more sensitive to sunlight

Always check the packet or leaflet that comes with your medicine. Ask a pharmacist or doctor for advice if you're not sure how to take it or have any problems taking it.

If you miss a dose of azathioprine

If you forget to take a dose of azathioprine, skip the dose you missed and take your next dose at the usual time.

Do not take 2 doses to make up for a missed dose.

If you take too much azathioprine

Taking an extra dose of azathioprine can be dangerous.

Side effects of azathioprine

Like all medicines, azathioprine can cause side effects, although not everyone gets them.

Common side effects

Common side effects of azathioprine include:

• feeling sick (nausea)
• your skin being more sensitive to sunlight

Azathioprine will not usually affect your ability to drive, ride a bike or use machinery.

Serious side effects

Azathioprine can also sometimes cause more serious side effects, such as:

• being more likely to get illnesses or infections
• feeling very tired or weak, getting headaches or looking more pale than usual (anaemia)
• muscle or joint pain, dizziness and shaking
• an allergic reaction (anaphylaxis) – which can cause symptoms such as a swollen throat or tongue, a raised, itchy rash or difficulty breathing
• a severe skin reaction (Stevens-Johnson syndrome) – causing flu-like symptoms, a rash, blisters and sores
• bone marrow problems – causing symptoms such as a high temperature, bruises, or bleeding for a long time after an injury
• liver problems – causing symptoms such as being sick, not feeling hungry, and yellowing of the whites of your eyes or skin (this may be harder to see on brown or black skin)

You will need to have regular blood tests to monitor your liver and bone marrow.

Who can and cannot take azathioprine

Most adults and children can take azathioprine.

But it's not suitable for everyone. For example, it may not be suitable if:

• you've had an allergic reaction or serious side effect from azathioprine or a similar medicine before
• you have liver or kidney problems
• you have recently been vaccinated using a live vaccine, such as for chickenpox or yellow fever
• you've had hepatitis B

Before taking azathioprine, tell your doctor if you have any medical conditions.

Breastfeeding and azathioprine

Speak to a doctor if you're breastfeeding. Azathioprine is not usually recommended but can be used if the benefits outweigh the risks.

It's rare for breastfed babies to get any side effects from medicine you're taking, but speak to a healthcare professional if you have any concerns about your baby.

Pregnancy and azathioprine

Speak to your doctor if you're pregnant or planning to get pregnant while taking azathioprine.

Azathioprine can be used in pregnancy if recommended by a specialist. They will speak to you about the benefits and risks, and any side effects you need to check for.

Find out more about taking azathioprine during pregnancy on the Bumps (Best Use of Medicines in Pregnancy) website

Taking azathioprine with other medicines, food and drink

There are some medicines, remedies and supplements that may not mix well with azathioprine.

This includes:

• some types of antibiotics, such as trimethoprim and co-trimoxazole
• medicines to help lower the chance of blood clots (anticoagulants), such as warfarin
• medicines to treat inflammatory bowel disease, such as mesalazine and sulfasalazine
• some medicines used to treat high blood pressure or heart failure, such as ACE inhibitors
• some medicines to treat gout, such as allopurinol or febuxostat

Before taking azathioprine, tell your doctor if you're taking any other medicines, herbal remedies, vitamins or supplements.

Vaccines and azathioprine

Azathioprine can make you more likely to get infections, so it's important to have any vaccinations you're offered.

But always tell the person giving the vaccine that you take azathioprine, as some types of vaccine may not be suitable for you.

People who live with you can reduce the risk of passing on an infection to you by also having any vaccinations they're offered.

Food, drink and alcohol with azathioprine

When taking azathioprine tablets, avoid having dairy products (such as milk, cheese, yoghurt or butter) from 1 hour before taking them until 2 hours afterwards.

If you're taking the liquid medicine, avoid having meals or any dairy products from 1 hour before taking it until 2 hours afterwards.