Azathioprine and Mercaptopurine for Inflammatory Bowel Disease

Telephone: 0191 4453148

Dose of Azathioprine or Mercaptopurine

Blood test monitoring

Blood tests are required regularly whilst taking Azathioprine or Mercaptopurine. Initially, this is every 2 weeks for the first 4 months and then monthly for 3 months. Once you are on a stable dose, you will need bloods every 3 months. 

You can use the box below to record the dates you need to attend for bloods.

This leaflet contains information about Azathioprine and Mercaptopurine to treat inflammatory bowel disease (IBD)

Why have I been given this leaflet?

The leaflet will help you to remember what your doctor has told you about this medicine. It will also help you to decide whether you want to go ahead with the treatment.

This leaflet aims to provide information regarding Azathioprine or Mercaptopurine for your inflammatory bowel disease (IBD): ulcerative colitis or Crohn’s disease.

What are Azathioprine and Mercaptopurine and how do they work?

Azathioprine and Mercaptopurine are immunosuppressants. This means they make your immune system weaker. The immune system protects us by fighting infections. But in Crohn’s disease and ulcerative colitis, the immune system goes wrong and starts fighting the gut instead. This causes inflammation and ulcers in the gut. Azathioprine and Mercaptopurine make the immune system weaker so it can’t fight the gut anymore. This reduces the inflammation.

Azathioprine and Mercaptopurine work in a similar way. Your IBD team will decide on which drug to start or may switch from one to the other if you get side effects.

How do I take these tablets?

Azathioprine

Azathioprine is usually taken as a tablet once per day and comes in two different strengths, 25mg and 50mg. The dose you are given depends on your body weight (between 2mg and 2.5mg per kilogram of body weight a day). Depending upon how well the tablets work for you, the dose and number of tablets that you need to take may change.

The tablets should be swallowed with a glass of water. Azathioprine may be taken with food or on an empty stomach. It is important that you take it at the same time each day, especially with respect to food (i.e., always take with food or always take without). Some patients experience nausea when first given Azathioprine – taking after meals may help with this. It may also help to divide the dose and take it twice a day. Speak to your IBD team if you want to try this.

Mercaptopurine

Mercaptopurine is usually taken once a day and comes as 50mg tablets. The dose you are given depends on your body weight (between 0.75mg and 1.5mg per kilogram of body weight a day). Depending how well the tablets work for you the dose may change.

You can take Mercaptopurine with food or on an empty stomach, but it shouldn’t be taken with milk or any dairy products. Take Mercaptopurine tablets one hour before or two hours after you drink milk or eat any dairy products. This includes cream, butter, cheese, and yoghurt made with milk from cows, goats, or sheep. It’s important to take your medicine in the same way every day.

For both Azathioprine and Mercaptopurine – take care to handle the tablets as little as possible and wash your hands after handling them. Store them at room temperature and out of reach of children. If you miss a dose, you should not ‘double up’. Take the next dose at the normal time and completely omit the missed dose. If you miss several doses, then contact your doctor or specialist nurse for advice on what to do next.

Pregnancy and Breastfeeding

Talk to your doctor if you are pregnant, plan to get pregnant or think you are pregnant to ensure Azathioprine or Mercaptopurine are still appropriate. Azathioprine or Mercaptopurine are one of the safer options in pregnancy; therefore, please do not stop taking them if you discover you are pregnant without discussing with the team.

Azathioprine or Mercaptopurine can also be found in breast milk. If you are breastfeeding or planning to breastfeed, talk to your doctor or pharmacist before taking them.

When should Azathioprine or Mercaptopurine not be used?

You should find a list of conditions that mean you should not take these medicines in the manufacturers patient information leaflet found in the box of tablets. Please tell your doctor if you have any of the conditions listed in the leaflet.

Do I need any checks before I start treatment?

You will require some screening tests to check if you have been exposed to a variety of viral infections including HIV, hepatitis B and C. We will also check if you have been exposed to chickenpox or Epstein Barr virus (which causes glandular fever) in the past. If you haven’t had chickenpox, you may be advised to get vaccinated before starting treatment.

Levels of TPMT (thiopurine methyl transferase) will be checked before you start treatment. This makes sure Azathioprine does not stay too long in your body. If levels are too low, this can cause serious side effects such as bone marrow suppression. If you have low TPMT levels, the dose of Azathioprine or Mercaptopurine can be reduced. If you have no TPMT then these medicines cannot be started.

Do I need any special checks while on Azathioprine or Mercaptopurine?

Azathioprine and Mercaptopurine reduce the production of white blood cells making you more vulnerable to infections and can sometimes affect the liver. Blood tests will show if you are developing any side effects. If you are being affected, your treatment will be changed or stopped immediately.

It is important that you do not miss your blood tests. You must not take Azathioprine or Mercaptopurine unless you are having regular blood tests. When you start Azathioprine or Mercaptopurine, you will need a blood test every 2 weeks for 4 months, then monthly for 3 months and then every 3 months when your dose is stable. Your doctor may increase or decrease the number of tablets you take at each dose depending upon the results of your tests.

Are there any Side Effects?

Most medicines have side effects. The manufacturer’s leaflet contains a list of the known side effects for this medicine. Everyone reacts differently to medicines. You may have some side effects or none at all.

Common side – effects include

• Feeling sick (nausea), being sick (vomiting) and loss of appetite. These reactions can be especially strong during the first few weeks of treatment. Taking your medication after eating or in two smaller doses each day instead my help reduce these side effects.
• Flu-like symptoms with fever and general aches and pain a few days or weeks after starting treatment. Tell your doctor if you feel unwell in this way.
• Diarrhoea

Other side effects

Because Azathioprine and Mercaptopurine act on the immune system, it can have some more serious side effects. Your IBD team will continue to monitor you to minimise risks but let them know if you:

• think you have an infection including having a fever, sore throat, and achiness
• have a bump or open sore which isn’t healing
• have yellowing of your skin, feel sick or are sick
• have new warts.

Suppression of normal bone marrow function

This can cause a reduction of red blood cells (anaemia), white blood cells (leucopenia) and platelets (thrombocytopenia). This can lead to weakness, breathlessness, and fatigue, being more likely to get infections, and a tendency to bruise or bleed easily. Regular monitoring should pick up a reduced blood count, but it is important that you contact your doctor if you develop an infection of any kind.

Liver inflammation

Your treatment monitoring will include regular liver function tests (LFTs) to check any changes to your liver function. Go to Accident and Emergency if you notice a yellowing of your skin or eyes, which may be a sign of jaundice.

Pancreatitis

This is inflammation of the pancreas, a digestive gland in the tummy. This can cause severe pain in the centre of the tummy that steadily gets worse then moves to the back. People often also feel very unwell. Usually this occurs within three weeks of starting treatment. Go to Accident and Emergency if you experience this type of symptom.

Shingles

There is an increased risk of shingles (herpes zoster reactivation). If you develop blister-like skin eruptions, you should stop the medication immediately and contact your IBD team. You can normally restart the drug once the rash has healed.

There is a slightly increased risk of certain types of cancer such as skin cancer and lymphomas and your doctor should explain this risk before starting treatment. Take care to avoid too much sun,

cover up and use a sunscreen with a high protection factor to reduce the risk of skin cancer.

Uncommon side effects (experienced by around 1 in 1000 people) may include sensitivity to sunlight, hair loss (which in many cases settles even with continuing treatment) and skin rashes

Will Azathioprine or Mercaptopurine affect any other medicines?

Tell your doctor or pharmacist about all the other medicines you take. This includes any medicines you have had prescribed by another doctor as well as medicines bought from a pharmacy or supermarket and any herbal remedies.

Some medicines interact with Azathioprine and include:

• Allopurinol (used to treat gout) unless your IBD team has prescribed it
• Warfarin (used to prevent blood clots)
• some antibiotics
• Febuxat (used to treat gout).

Whenever you are prescribed a new medicine or want to buy a medicine e.g., from a pharmacy or supermarket, it is important that you tell the doctor or pharmacist about all the medicines that you take, including Azathioprine. You should also tell your dentist when you see him / her. See the leaflet in with your tablets for more information.

Azathioprine and Mercaptopurine are sometimes given together with biologic medicines such as infliximab and adalimumab. This combination can be more effective and can reduce the risk of anti-drug antibodies being produced against these biologics.

Will Azathioprine or Mercaptopurine affect any vaccinations?

Live vaccinations (such as yellow fever or MMR vaccine) should be avoided unless it is advised to be safe for you by the IBD team. Non-live (inactivated) vaccinations may be less effective. The pneumonia, flu and COVID vaccines are all safe and recommended. There is also a non-live shingles vaccine now available which is also safe for you to have.

If you need to have a vaccine while taking this medication talk to your doctor first. They will be able to advise you on what vaccines you can have.

Can I drink alcohol while I am taking Azathioprine or Mercaptopurine?

Azathioprine and Mercaptopurine do not interact with alcohol.  However, it is recommended that you do not exceed the national guidelines, which is 14 units a week.

If you have been diagnosed with liver cirrhosis, then we advise complete abstinence from alcohol (i.e., drink no alcohol).

Where should I store Azathioprine or Mercaptopurine at home?

Store your medication in a cool, dry place away from direct sunlight.

It is important that all medicines are stored out of reach of children