Mercaptopurine (Xaluprine)

You will be prescribed mercaptopurine by a specialist cancer doctor.

Your doctor will discuss with you the possibility of unwanted side-effects. You will have an increased risk of infection so it's important you let your doctor know straightaway if you develop a high temperature (fever), your throat becomes sore or you feel generally unwell.

Type of medicineAn antimetabolite anti-cancer medicine
Used forTreatment of leukaemia
Also calledXaluprine®
Available asTablets and oral liquid medicine

Leukaemia is a cancer of cells in the bone marrow. The cancerous cells in the bone marrow spill out into the bloodstream. Most types of leukaemia arise from cells which normally develop into white blood cells. There are several different types of leukaemia and treatments for the different types vary. Mercaptopurine is a treatment used for acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), and chronic myeloid leukaemia (CML).

In cancers like leukaemia, certain cells in the body grow and multiply too fast. Anti-cancer medicines like mercaptopurine work by stopping the growth of the cancer cells. They do this by affecting the genetic material of the cells. This reduces the number of new cells that your body makes.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking mercaptopurine, it is important that your doctor knows:

  • If you are pregnant, or intend to have children in the future.
  • If you are breast-feeding.
  • If you have ever been told by a doctor that you lack certain enzymes which help remove medicines from your body. In particular, tell your doctor if you know your body produces too little of an enzyme called thiopurine methyltransferase (TPMT).
  • If you have any problems with the way your liver works or how your kidneys work.
  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines. It is particularly important that your doctor knows if you are taking a medicine for gout, called allopurinol.
  • If you have ever had an allergic reaction to a medicine. 
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack and any other written information you are given. The manufacturer's leaflet will give you more information about mercaptopurine and a full list of the side-effects which you may experience from taking it.
  • Mercaptopurine will be prescribed for you by a specialist doctor who is experienced in treating your condition. Your dose will be calculated from your weight and height, although it may be adjusted from time to time depending on the results of some of the tests you will need to have. It is important that you take the tablets/medicine exactly as your doctor tells you to. The dose you have been prescribed will be printed on the label of your pack to remind you what your doctor has said.
  • You can take mercaptopurine either before or after food, but it is better if you stick to one or the other for every dose. Also, you should take your dose at least one hour before any milk or dairy food, or wait until two hours afterwards.
  • If you (or your child) are taking the liquid medicine (Xaluprine®) take care not to get any on the skin or in the eyes or nose. If this happens, wash the area well with soap and water. If you are a parent or carer giving the liquid medicine to a child, wash your hands thoroughly before and after use or wear disposable gloves when handling the medicine.
  • Use the oral syringe provided to measure out your doses. Your nurse or doctor will show you how to do this.
  • If you are taking tablets, they should be swallowed whole with a drink of water.
  • It will help you to remember to take your doses if you try to take them at the same times each day. Unless you have been told otherwise, take your doses in the evening as it is more effective then. 
  • If you do forget to take a dose, take the next dose when it is due and remember to let your doctor know about the missed dose. Do not take two doses together to make up for a missed dose.
  • You must try to keep your regular appointments with the doctor or hospital. This is so your progress can be checked. You will need to have regular blood tests during your treatment with this medicine.
  • You must avoid getting pregnant or fathering a child while you are on mercaptopurine. Make sure you have discussed with your doctor which types of contraception are suitable for you and your partner. Many anti-cancer treatments are associated with reduced fertility (particularly in men), so you may also want to ask your doctor for family planning advice if you intend to have children in the future.
  • If you are due to have an operation or dental treatment, tell the person carrying out the treatment that you are taking mercaptopurine.
  • Do not have any immunisations (vaccinations) while you are taking this medicine and for several months afterwards, without talking to your doctor first. Mercaptopurine lowers your body's resistance and there is a chance that you may get an infection from some vaccines.
  • If you buy any medicines, check with a pharmacist that they are suitable to take with your other medicines.
  • Any unwanted tablets or medicine must be disposed of in a special way - ask your local or hospital pharmacy for advice about what to do.

Mercaptopurine will lower the number of white cells in your blood, increasing the chance of you getting an infection. You should take certain precautions to reduce the risk of infection - if possible, avoid people with infections and let your doctor know if you think you are getting a sore throat or if you have a high temperature.

Your doctor will discuss with you the possibility of unwanted side-effects of treatment. The table below contains some of the most common ones associated with mercaptopurine. You will find a full list in the manufacturer's information leaflet supplied with your tablets/medicine. Let your doctor know if you experience any of the following, or if you develop any other symptoms which you think may be due to this medicine:

Common mercaptopurine side-effects
What can I do if I experience this?
A high temperature or feeling feverish, sore throat, infections (due to changes in the number of blood cells)Let your doctor know about this as soon as possible
Feeling sick (nausea) or being sick (vomiting), loss of appetiteEat simple meals (avoid rich or spicy foods). If this becomes troublesome, let your doctor know, as you can be prescribed an anti-sickness medicine
Sore mouth, diarrhoeaSpeak with your doctor about either of these
Liver or blood problemsYour doctor will check for these
  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

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Further reading & references

Current Version:
Mr Michael Stewart
Peer Reviewer:
Dr Helen Huins
Document ID:
1077 (v25)
Last Checked:
21 March 2017
Next Review:
20 March 2020
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