Mercaptopurine (6-MP, Purinethol )

• What mercaptopurine is
• Common side effects
• Occasional side effects
• Rare side effects
• Important points to remember
• Immunisations and chemotherapy

Mercaptopurine is a chemotherapy drug that doctor use to treat some types of cancers, including acute leukaemia. It is one of a group of chemotherapy drugs known as anti metabolites. These stop cells making and repairing DNA. Cancer cells need to make and repair DNA in order to grow and multiply.

Mercaptopurine comes as fawn coloured 50mg tablets that you swallow with lots of water. You should take them at the same time each day, 30 to 60 minutes before eating.

You usually have chemotherapy as a course of several cycles of treatment. The treatment plan for mercaptopurine depends on which type of cancer you have. There is more about planning chemotherapy in the main chemotherapy section of CancerHelp UK.

The side effects of mercaptopurine are listed below. You can use the links to find out more about each side effect or click on search at the top of the page.

With this drug, many people have a temporary drop in the number of blood cells made by the bone marrow, leading to the following side effects

• Increased risk of getting an infection from a drop in white blood cells - it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, sore throat, pain passing urine or feel cold and shivery. 
• Tiredness and breathlessness due to a drop in red blood cells (anaemia) - you may need a blood transfusion
• Bruising more easily due to a drop in platelets - you may have nosebleeds, bleeding gums after brushing your teeth, or lots of tiny red spots or bruises on your arms or legs (known as petechia).

These effects on your bone marrow can begin about 7 days after each treatment and usually go back to normal after about 21 to 28 days. Some of these side effects can be life threatening, particularly infections.  You should contact your doctor if you have any of these side effects.  Your doctor will check your blood counts regularly to see how well your bone marrow is working.

• Fatigue (tiredness)during and after treatment – most people find their energy levels are back to normal within 6 months to a year

 

Some people may have one or more of the following side effects

• Diarrhoea - drink plenty of fluid and tell your doctor if diarrhoea becomes severe, or continues for more than 3 days
• Feeling or being sick is usually well controlled with anti sickness drugs medications
• Sore mouth and throat
• Liver changes that are very mild and unlikely to cause symptoms – the liver will almost certainly go back to normal when treatment is finished, but you will have regular blood tests to check how well your liver is working
• Loss of fertility we don’t know exactly how this drug affects fertility so do talk with your doctor before starting treatment if this is important to you
• Women may stop having periods (amenorrhoea) but this may only be temporary
• Mercaptopurine may have a harmful effect on a developing baby – do talk to your doctor about contraception before having treatment if there is any chance that you or your partner could become pregnant
• Doctors do not recommend breast feeding while taking mercaptopurine in case the drug could be passed on in the milk
• An itchy rash

• Hair loss is rare, but can begin 2 to 5 weeks after treatment starts
• Kidney changes that are mild and unlikely to cause symptoms may occur – they will almost certainly go back to normal when treatment is finished, but you will have regular blood tests to check how well your kidneys are working
• Reddening of the skin in areas where you have had radiotherapy in the past, and the skin may get dry and flaky and feel sore and hot – this goes away on its own but keep affected areas out of the sun
• Fever and chills

 

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

• How many times you've had the drug before
• Your general health
• The amount of the drug you have (the dose)
• Other drugs you are having

Some side effects are inconvenient or upsetting but not damaging to your health.

Some side effects are serious medical conditions and need treating. Where we have urged you to contact your doctor, this is because

• Your side effect may need treating
• Your drug dose may need reducing to try to prevent the side effect

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and other over the counter remedies - some drugs can react together.

Talk to your doctor, pharmacist or nurse about all your side effects so that they can help you manage them.

Your chemotherapy nurse, clinic or ward nurse will have given you a contact number. You can ring if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.

You should not have immunisations with live vaccines while you are having chemotherapy or for at least 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG and yellow fever. You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered from your chemotherapy.

It is perfectly safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with oral vaccines, but no one in the UK is given an oral vaccine now. So there is no problem in being with any baby or child who has recently had any vaccination in the UK. If you live abroad, you might need to make sure that you aren't in contact with anyone who has had oral polio or oral typhoid vaccination recently.