A thiopurine (also spelled thioguanine)
Tioguanine
A thiopurine used mainly for some leukaemias, needing regular blood-count and liver monitoring.
What is Tioguanine?
Tioguanine, sometimes spelled thioguanine, is a thiopurine medicine used mainly to treat certain types of leukaemia, and occasionally in inflammatory bowel disease under specialist care. Like other thiopurines it slows fast-dividing cells and calms the immune system, which lowers the blood counts and raises the risk of infections. Regular blood tests are essential to watch the blood counts and the liver, and a particular concern with tioguanine is a liver problem affecting its blood vessels, so it is usually used for shorter courses. The TPMT enzyme is often checked before starting, and it should not be combined carelessly with other immune-lowering medicines.
Education and reference only. This is a plain-language guide to Tioguanine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Tioguanine is a thiopurine, in the same family as mercaptopurine and azathioprine, that both fights some cancers and dampens the immune system. It is used mainly in certain leukaemias, often as part of combination treatment, and occasionally in inflammatory bowel disease when other options are unsuitable. It is taken as tablets by mouth. It is a specialist medicine needing regular blood monitoring, and tends to be used for shorter periods because of a specific liver concern.
How it works
Tioguanine interferes with the building blocks cells need to copy their DNA, which slows down fast-dividing cells such as leukaemia cells and overactive immune cells. This helps control the conditions it treats. Because it also affects the normal blood-forming cells of the bone marrow, it lowers the blood counts, so these are monitored. A particular issue with tioguanine is that long-term use can damage the small blood vessels of the liver, which is why it is usually reserved for shorter courses and the liver is watched closely.
Company & origin
Originated / developed by: Generic (long-established).
A thiopurine used in the UK mainly to treat certain leukaemias, and occasionally in inflammatory bowel disease.
Practical use
How to take Tioguanine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it exactly as prescribed by your specialist, keeping to the schedule you are given.
- If a TPMT enzyme check has been arranged, make sure it is done, as it helps guide the dose.
- Attend all blood tests, which check your blood counts and liver and are needed throughout treatment.
- Report fever, sore throat, unusual bruising or bleeding, or yellowing of the skin or eyes promptly.
- Avoid live vaccines unless your specialist confirms they are safe, and never stop the medicine suddenly without advice.
- Tell every prescriber and pharmacist that you take tioguanine before starting any new medicine.
Weighing it up
Advantages & disadvantages of Tioguanine
Advantages
- An effective treatment for certain leukaemias, often as part of combination therapy.
- Taken simply as tablets by mouth.
- Dosing can be tailored using the TPMT test and regular blood counts.
Disadvantages
- Lowers the blood counts and needs regular blood tests throughout treatment.
- Can damage the small blood vessels of the liver, especially with long-term use, so courses are usually shorter.
- Increases the risk of infections and a small increased risk of certain cancers with long-term use.
Practical use
Good to know
Tioguanine is most often used for leukaemia, and the main safety concerns are low blood counts, infection risk and a liver problem affecting its small blood vessels, which is why it is usually given for shorter periods rather than long term. Regular blood tests to check the full blood count and the liver are essential, and the TPMT enzyme is often checked before starting, as people who break thiopurines down slowly are more prone to side effects. It increases the risk of infections, so report fevers, sore throats, unusual bruising or bleeding promptly. Live vaccines are generally avoided, it should not be stopped suddenly without advice, and you should tell every prescriber that you take it before any new medicine is started.
Who should not take it / use with caution
- People with very low TPMT enzyme activity may be unable to take it or need a much lower dose.
- It is generally avoided in active serious infections and significant liver problems.
- Those who cannot attend regular monitoring blood tests are not suitable without arrangements in place.
Monitoring
- Regular full blood count tests to watch for low blood counts during treatment.
- Liver blood tests, with particular attention to the liver because of the blood-vessel concern.
- TPMT enzyme testing where arranged, and ongoing watch for infections and other side effects.
Side effects
- Lowered blood counts, increased infection risk, nausea and changes in liver blood tests are common.
- Tiredness, loss of appetite and mouth ulcers.
- Less commonly, a liver problem affecting its small blood vessels, and a higher risk of certain cancers with long-term use.
Key interactions
- Other medicines that lower the blood counts or affect the immune system can add to its effects.
- Some vaccines (live vaccines) are generally avoided while taking it, so check before any vaccination.
- As with other thiopurines, care is needed with medicines that can affect the liver.
Available as: Tablets taken by mouth.
Answers
Tioguanine: frequently asked questions
Is tioguanine the same as thioguanine?
Yes, they are two spellings of the same medicine, a thiopurine used mainly for certain leukaemias.
Why is it usually given for shorter periods?
Long-term use can damage the small blood vessels of the liver, so it is generally reserved for shorter courses with close liver monitoring.
Why do I need regular blood tests?
Blood tests check your blood counts and liver, as tioguanine lowers the blood counts and can affect the liver.
Does it raise my risk of infections?
Yes, because it lowers the immune system and blood counts, so report fevers, sore throats or unusual bruising and bleeding promptly.
Can I have my usual vaccinations?
Live vaccines are generally avoided while taking it; check with your specialist before any vaccination.
The wider class
About Thiopurines
Tioguanine belongs to the thiopurines class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
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