[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Antimetabolites](https://durgical.com/en/pharmacology/classes/antimetabolites/) › Tioguanine

# Tioguanine

## Antimetabolites?

Antimetabolites

## High alert?

An error with this medicine can cause serious harm: double checks and protocols are used.

Oral thiopurine for acute myeloid leukaemia. Like mercaptopurine it forms thioguanine nucleotides; inherited enzyme deficiencies and liver damage are the risks.

Updated Nov 1, 2026

Also called: thioguanine, 6-thioguanine, 6-TG

## Quick facts

**Group**
[Antimetabolites](https://durgical.com/en/pharmacology/classes/antimetabolites/)

**Target**
DNA/RNA and purine synthesis, through thioguanine nucleotides

**Used for**
Acute myeloid leukaemia

**Key effects**
Nausea · Mouth and throat sores · Myelosuppression

**Monitor**
Complete blood count regularly

**ATC**
L01BB03

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

Tioguanine is a sulfur analogue of guanine. The salvage enzyme HGPRT converts it directly into thioguanosine monophosphate, which is turned into thioguanine nucleotides. These are built into DNA and RNA and also inhibit purine synthesis and interconversion, so dividing cells stop and die. Thiopurine S-methyltransferase (TPMT) inactivates part of it, and people with inherited low enzyme activity accumulate toxic nucleotides.

- HGPRT converts tioguanine into thioguanosine monophosphate
- Thioguanine nucleotides form
- They are built into DNA and RNA and block purine synthesis
- Inherited low TPMT activity leads to toxic build-up

## Indications

- Acute myeloid leukaemia, in combination regimens. [Acute leukaemia (AML and ALL) →](https://durgical.com/en/conditions/acute-leukaemia/)

## Adverse effects

### Common

- Nausea, vomiting, loss of appetite
- Mouth and throat sores
- Myelosuppression
- Headache

### Serious (rare, important)

- Liver damage: jaundice, abdominal swelling, right upper abdominal pain, fluid retention
- Severe myelosuppression, especially with inherited low thiopurine enzyme activity
- Serious infections and bleeding (bloody vomit, black stools)

## Contraindications

- Hypersensitivity to tioguanine or its ingredients

## Key interactions

**Other myelosuppressive drugs**
Additive bone marrow suppression.

## What is monitored

- Complete blood count regularly
- Liver tests and signs of liver injury (weight gain, abdominal swelling, jaundice)
- Genetic testing for a thiopurine risk factor before or during treatment, where available

## Administration and safety

- Hazardous drug: tablets are handled with gloves.
- Generous fluid intake during treatment.
- Taken at about the same time every day, exactly on the prescribed schedule.

## Pregnancy and breastfeeding

Can cause fetal harm; pregnancy and breastfeeding are avoided during treatment.

## Nursing care

- Check counts and liver tests before each cycle.
- Weigh the patient and ask about abdominal swelling or right-sided pain.
- Teaching: report yellow skin or eyes, swelling, bleeding or fever at once.

## Pharmacokinetics

**Absorption**
Oral tablets.

**Metabolism**
Activated by HGPRT; inactivated partly by TPMT methylation.

## Memory aid

«6-TG: Thiopurine that Grabs the liver»: AML drug; HGPRT activates it, TPMT inactivates it, and the liver is the organ to watch.

## Test yourself

Think of the answer, then tap the question to see it.

## Which enzyme activates tioguanine?

HGPRT (hypoxanthine-guanine phosphoribosyltransferase).

## Which leukaemia is tioguanine used for?

Acute myeloid leukaemia.

## Which organ should be watched closely during tioguanine treatment?

The liver: jaundice, abdominal swelling and fluid retention signal damage.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/tioguanine/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

**High alert**
An error with this medicine can cause serious harm: double checks and protocols are used.

## Connections

## Related drugs 2

- [Mercaptopurine](https://durgical.com/en/pharmacology/mercaptopurine/)
- [Cytarabine](https://durgical.com/en/pharmacology/cytarabine/)

## Related conditions 1

- [Acute leukaemia (AML and ALL)](https://durgical.com/en/conditions/acute-leukaemia/)

[← Back to the class: Antimetabolites](https://durgical.com/en/pharmacology/classes/antimetabolites/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Thioguanine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682099.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01BB03) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/tioguanine/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/tioguanine/