Explanation

Mercaptopurine (also called Puri-Nethol®) is a medicine used to treat leukaemia. It is a type of medicine called a cytotoxic.

What does it do?

Mercaptopurine works by stopping cancer cells from multiplying and killing them. This helps stops cancer from growing and spreading around your body.

What does it look like?

Mercaptopurine comes as a small white tablet that you swallow.

When do I take it?

Your doctor will tell you when to take your mercaptopurine. You will probably need to take it once a day.

But what if I don't feel like taking it?

You need to keep taking your mercaptopurine until your doctor is sure that all the cancer in your body has gone. If you stop taking it before your doctor says it's okay, then the cancer can grow back.

It's really important to keep taking it, even if it's making you feel sick and horrible. Just remember, you won't have to take it forever. Keep thinking about all the cancer cells it's killing inside you! Each cancer cell it kills is one more step towards getting better.

What if I forget to take it?

If you forget to take your mercaptopurine, tell your doctor or the person looking after you.

Don't take twice as much next time to catch up. Remember the three Ds: Don't Double Dose!

How much do I take?

This depends on how serious your condition is, how much you weigh and what other medicines you are taking. Your doctor will decide the perfect dose for you.

What are the most likely side effects I might get?

The side effects you are most likely to get from taking mercaptopurine are:

Feeling or being sick

Problems with your liver

Anaemia

Not feeling very hungry

If you notice these or any other side effects, tell your doctor or an adult who looks after you.

What other side effects might I get?

Mercaptopurine can cause other, less likely, side effects, like:

Ulcers in your mouth

An inflamed pancreas, which can cause pain in your side near your tummy and make you sick

Losing your hair (but don't worry, your hair usually grows back after treatment is stopped)

If you notice these or any other side effects, tell your doctor or an adult who looks after you.

Are there any other side effects you haven't mentioned?

Mercaptopurine has been linked with problems with your white blood cells and ulcers in your small intestine, but this is very unusual.

If you notice any of the side effects in the list below, tell your doctor or a person who looks after you straight away:

Signs of an allergic reaction, like a swollen face, skin rash, high temperature or problems breathing

Unexpected bruising

A high temperature or feeling unwell

Feeling generally unwell

Your skin or the whites of your eyes going a yellowish colour

Runny poo (diarrhoea)

Feeling or being sick

Is it safe for me to be taking mercaptopurine?

Before you are treated with mercaptopurine, tell your doctor about any other medical problems that you know you have, or if you know that you are allergic to it.

Is it okay for me to take mercaptopurine if I'm already taking other medicines?

You should tell your doctor about any other medicines that you are taking, or have taken, recently, including herbal medicines. It's especially important to mention if you are taking:

allopurinol, which is used to treat gout (an illness that causes aching joints)

warfarin, which is used to stop your blood clotting too easily

olsalazine, mesalazine or sulfasalazine

If you are going to have a vaccine, you should also tell your doctor first.

Is there anything else I need to know about mercaptopurine?

When you are having mercaptopurine, your doctor will give you a blood test every week to check that your blood cells and/or liver are working properly.

What if I have any more questions?

If you have any other questions, you can ask your doctor, or chat to other people about Mercaptopurine in the Medikidz forums and virtual world, Mediland.