Tioguanine

Tioguanine is a type of chemotherapy. It is a treatment for some types of leukaemia. You usually have it with other chemotherapy drugs.

How tioguanine works

Tioguanine 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 tioguanine

You take tioguanine as tablets. You swallow them whole with a glass of water.

If you need to break your tablet in half, wash your hands straight afterwards. Be careful not to breathe in any powder that the tablet releases.

If you accidentally take more tioguanine than you should tell your doctor straight away or go to a hospital. Take the medicine pack with you.

Tell your doctor if you forget to take tioguanine. Don't take a double dose to make up for the missed dose.

Taking your tablets

You must take tablets according to the instructions your doctor or pharmacist gives you.

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 tioguanine

You usually have tioguanine chemotherapy as a course of several cycles of treatment. The treatment plan 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

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

Contact your doctor or nurse immediately if you have signs of infection, including a temperature above 37.5C or below 36C.

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

Common side effects

These side effects happen in more than 10 in 100 people (10%). You might have one or more of them. They include:

Increased risk of 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 nose bleeds

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 petechiae).

Breathlessness and looking pale

You might be breathless and look pale due to a drop in red blood cells. This is called anaemia.

Liver problems

You have regular blood tests to check for changes to the liver. Long term use of tioguanine can cause serious liver problems. Tell your doctor if you have:

  • yellowing of the skin or whites of the eyes (jaundice)
  • itchy skin,
  • dark urine 
  • pale coloured poo (stools)
  • sickness or feel sick
  • tiredness

Occasional side effects

These side effects happen in between 1 and 10 out of every 100 people (1 to 10%). You might have one or more of them. They include:

  • a sore mouth or mouth ulcers
  • feeling or being sick
  • diarrhoea
  • high levels of uric acid in your blood that could stop your kidneys from working properly

Rare side effects

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

  • bowel problems which can cause severe stomach ache, being sick, diarrhoea and fever
  • severe liver damage when used with other chemotherapy drugs, oral contraceptives and alcohol

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 drinks

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.

Tioguanine contains lactose (milk sugar). If you have been told by a doctor that you have an intolerance to some sugars, contact your specialist before taking this drug.

Loss of 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 might be able to store sperm before starting treatment. And women might be able to store eggs or ovarian tissue. But these services are not available in every hospital, so you would need to ask your doctor about this.    

Contraception and pregnancy

This treatment might harm a baby developing in the womb. It is important not to become pregnant or father a child while you're having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.

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.

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 one of the shingles vaccines called Zostavax.

You can have:

  • other vaccines, but they might not give you as much protection as usual
  • the flu vaccine (as an injection)
  • the coronavirus (COVID-19) vaccine - talk to your doctor or pharmacist about the best time to have it in relation to your cancer treatment

Members of your household who are aged 5 years or over are also able to have the COVID-19 vaccine. This is to help lower your risk of getting COVID-19 while having cancer treatment and until your immune system Open a glossary item recovers from treatment.

Contact with others who have had immunisations - You can be in contact with other people who have had live vaccines as injections. Avoid close contact with people who have recently had live vaccines taken by mouth (oral vaccines) such as the oral typhoid vaccine.

If your immune system is severely weakened, you should avoid contact with children who have had the flu vaccine as a nasal spray as this is a live vaccine. This is for 2 weeks following their vaccination.

Babies have the live rotavirus vaccine. The virus is in the baby’s poo for about 2 weeks and could make you ill if your immunity is low. Get someone else to change their nappies during this time if you can. If this isn't possible, wash your hands well after changing their nappy.

Lesche-Nyhan syndrome

It is possible that tioguanine may not work for people who have Lesche-Nyhan syndrome. This syndrome is an inherited disorder in which people have very low levels of a protein needed to make tioguanine work.

TPMT (thiopurine methyltransferase)

Tioguanine may cause very severe side effects if you have a condition where your body produces too little of something called TPMT (thiopurine methyltransferase). Your doctor may do blood tests to check if there is a risk of developing severe side effects from this drug.

Sensitivity to the sun

You may become sensitive to sunlight which can cause skin discolouration or a rash. Avoid too much sun by staying in the shade, covering up and using sunscreen.

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.

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