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Tioguanine (thioguanine, 6-TG, 6-tioguanine)

Find out what tioguanine is, how you have it and other important information about taking tioguanine.

Tioguanine is a chemotherapy drug and is also known as thioguanine, 6-TG or 6-tioguanine.

It is a treatment for: 

  • acute myeloid leukaemia
  • acute lymphoblastic leukaemia
  • chronic myeloid leukaemia

How it 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 it

You have tioguanine as tablets.

Take them on an empty stomach with plenty of water (for example, at least 1 hour before or 2 hours after meals). 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. 

If you forget to take tioguanine tell your doctor. 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. 


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

Important information

Other medicines, foods and drink

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.

Pregnancy and contraception

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.


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 may be able to store sperm before starting treatment. Women may be able to store eggs or ovarian tissue but this is rare.


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.

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 the levels before you start treatment. 


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 shingles vaccine (Zostavax).

You can:

  • have other vaccines, but they might not give you as much protection as usual
  • have the flu vaccine (as an injection)
  • be in contact with other people who've had live vaccines as injections

Avoid close contact with people who’ve recently had live vaccines taken by mouth (oral vaccines) such as oral polio or the typhoid vaccine.

This also includes the rotavirus vaccine given to babies. The virus is in the baby’s poo for up to 2 weeks and could make you ill. So, avoid changing their nappies for 2 weeks after their vaccination if possible. Or wear disposable gloves and wash your hands well afterwards.

You should also avoid close contact with children who have had the flu vaccine nasal spray if your immune system is severely weakened. 

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.

Information and help

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