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Mercaptopurine

Sounds like 'mer-CAP-toe-PURE-een'

Key points about mercaptopurine

Mercaptopurine is used to treat autoimmune conditions such as Crohn's disease or ulcerative colitis.
Mercaptopurine is also called Puri-Nethol.
Find out how to take it safely and possible side effects.

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Mercaptopurine is an immunosuppressant medicine, which means it weakens your body’s defence (immune) response. It's used to treat inflammatory bowel disease (eg, Crohn's disease and ulcerative colitis) when the condition has been difficult to control, for example if many courses of steroid therapy are needed. Read more about Crohn's disease and ulcerative colitis.

Higher doses of mercaptopurine are used to treat some cancers like leukaemia.

In Aotearoa New Zealand mercaptopurine is available as tablets (50mg).

The dose of mercaptopurine is different for different people, depending on your condition, weight and response to treatment.
Always take mercaptopurine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it and any special instructions.

Timing of your doses: Mercaptopurine is best taken on an empty stomach, at least 1 hour before or 3 hours after food or milk. Try to take your dose at the same time each day. Swallow your tablets whole with a drink of water. Don't break, chew or crush the tablets.
Missed dose: If you forget to take your mercaptopurine dose, take it as soon as you remember. But if it is nearly time for your next dose, take the next dose at the right time. Don't take double the dose.
Keep taking mercaptopurine regularly. Mercaptopurine doesn't work straight away. It usually takes a few weeks or months before you notice the full benefits.

Here are some things to know when you're taking mercaptopurine. Other things may be important as well, so ask your healthcare provider what you should know about.

You will need to have regular blood tests to monitor for side effects and to check whether the treatment is effective. Blood tests are very important during the first few months of treatment.
Mercaptopurine weakens your body’s defence (immune) system, so you're more likely to pick up infections. It's important to avoid anyone who has chickenpox or shingles.
You should avoid becoming pregnant while you or your partner are taking mercaptopurine. Talk to your healthcare provider about which types of contraception are suitable for you and your partner.
Some vaccines should not be taken if you are on mercaptopurine. Always check with your doctor or pharmacist first. It's safe for you to have the annual flu vaccine.
Mercaptopurine may interact with a few medicines and herbal supplements, so check with your doctor or pharmacist before starting mercaptopurine or before starting any new medicines – including those you buy over-the -counter.

Like all medicines, mercaptopurine can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects	What should I do?
Feeling sick (nausea) Vomiting (being sick) Loss of appetite (don't feel like eating) Headache Aches and pains	This is quite common when you first start taking mercaptopurine. Tell your doctor if these bother you.
Signs of changes in your blood cells, eg, a severe sore throat, mouth ulcers, easy bruising, nosebleeds, bleeding gums, shortness of breath or fever.	Tell your doctor immediately as you may need a blood test and your treatment may need to be adjusted.
Signs of getting an infection, such as feeling unwell, fever or chills	Tell your doctor immediately or phone Healthline on 0800 611 116.
Signs of problems with your liver, such as sudden pains in your stomach, loss of appetite or yellowing of your skin and eyes	Tell you doctor immediately or phone Healthline on 0800 611 116.
For more information on side effects, see the Medsafe consumer information leaflet Puri-Nethol(external link). Read more about medicines and side effects and reporting a reaction you think might be a side effect.