Mercaptopurine is also called Xaluprine. It is a chemotherapy drug used to treat some types of leukaemia. 

How it works

Mercaptopurine is one of a group of chemotherapy drugs known as anti metabolites. These drugs stop cells making and repairing DNA. Cancer cells need to make and repair DNA so that they can grow and multiply. 

How you have it

Mercaptopurine comes as pale yellow tablets and as a pink to brown liquid (oral suspension). The liquid medicine is called Xaluprine. 

Taking mercaptopurine tablets

You swallow the tablets whole with lots of water. You can take them with food, or on an empty stomach. 

You should take the tablets at the same time each day. You should not take them at the same time as milk or dairy products. You can take them:

• 1 hour before milk or dairy products
• 2 hours after milk or dairy products

If you need to break them in half, wash your hands afterwards and make sure that you don't breathe in any of the powder released by the tablet.

Taking mercaptopurine liquid

Your nurse or pharmacist will show you how to measure the dose of liquid mercaptopurine (Xaluprine) using a syringe. You need to wear disposable gloves while doing this so that the drug doesn't contact your skin.

You take Xaluprine in the evening, with food or on an empty stomach. But whichever you choose, you should do the same thing each day. You should drink some water after taking the liquid.

Milk and dairy products can make this drug less effective so you should take Xaluprine at least 1 hour before or 2 hours after milk or dairy products.   

If you take too much mercaptopurine

If you accidentally take more mercaptopurine than you should you might feel sick, be sick or have diarrhoea. 

Tell your doctor or go to a hospital straight away. Take the medicine pack with you.

If you forget to take mercaptopurine

Don't take a double dose to make up for the dose that you forgot. Tell your doctor or nurse. 

Taking your tablets or capsules

You should take the right dose, not more or less.

Talk to your specialist or advice line before you stop taking a cancer drug.

When you have it

You usually have mercaptopurine as a course of several cycles of treatment. The treatment plan for mercaptopurine depends on which type of cancer you have. 

Tests

You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

Side effects

We haven't listed all the side effects. It is very unlikely that you will have all of these side effects, but you might have some of them at the same time.

How often and how severe the side effects are can vary from person to person. They also depend on what other treatment you are having. For example, your side effects could be worse if you are also having other drugs or radiotherapy.

When to contact your team

Your doctor, nurse or pharmacist will go through the possible side effects. They will monitor you closely during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

• you have severe side effects 
• your side effects aren’t getting any better
• your side effects are getting worse

Early treatment can help manage side effects better. 

Common side effects

These effects happen in more than 1 in 10 people (10%). They include:

Increased risk of getting an infection

Increased risk of getting an infection is due to a drop in white blood cells. Symptoms include a change in temperature, aching muscles, headaches, feeling cold and shivery and generally unwell. You might have other symptoms depending on where the infection is.

Infections can sometimes be life threatening. You should contact your advice line urgently if you think you have an infection. 

Bruising, bleeding gums or nosebleeds

This is due to a drop in the number of platelets in your blood. These blood cells help the blood to clot when we cut ourselves. You may have nosebleeds or bleeding gums after brushing your teeth. Or you may have lots of tiny red spots or bruises on your arms or legs (known as petechia).

Occasional side effects

These effects happen in more than 1 in 100 people (1%). You might have one or more of them. They include:

• diarrhoea
• feeling or being sick
• breathlessness and looking pale (due to low red blood cell counts) and tiredness
• sore mouth
• changes to how your liver works
• blocked bile ducts

Rare side effects

These effects happen in fewer than 1 in 100 people (1%). You might have one or more of them. They include:

• loss of appetite
• skin changes (such as rash)
• inflammation of the pancreas
• aching muscles

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drink

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment with this drug and for at least 3 months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.

Fertility

You may not be able to become pregnant or father a child after treatment with this drug. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men may be able to store sperm before starting treatment. Women may be able to store eggs or ovarian tissue but this is rare.

Breastfeeding

Don’t breastfeed during this treatment because the drug may come through into your breast milk.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment if you need treatment for anything else, including teeth problems.

Lactose and mercaptopurine 

This drug contains lactose (milk sugar). If you have an intolerance to lactose, contact your doctor before taking this medicine.

Immunisations

Don’t have immunisations with live vaccines while you’re having treatment and for up to 12 months afterwards. The length of time depends on the treatment you are having. Ask your doctor or pharmacist how long you should avoid live vaccinations.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and shingles vaccine (Zostavax).

You can:

• have other vaccines, but they might not give you as much protection as usual
• have the flu vaccine (as an injection)
• be in contact with other people who've had live vaccines as injections

Avoid close contact with people who’ve recently had live vaccines taken by mouth (oral vaccines) such as oral polio or the typhoid vaccine.

This also includes the rotavirus vaccine given to babies. The virus is in the baby’s poo for up to 2 weeks and could make you ill. So, avoid changing their nappies for 2 weeks after their vaccination if possible. Or wear disposable gloves and wash your hands well afterwards.

You should also avoid close contact with children who have had the flu vaccine nasal spray if your immune system is severely weakened. 

More information about this treatment

For further information about this treatment go to the electronic Medicines Compendium (eMC) website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.