[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Other antineoplastics (differentiating agents, asparaginases, proteasome inhibitors)](https://durgical.com/en/pharmacology/classes/other-antineoplastics/) › Arsenic trioxide

# Arsenic trioxide

## Other antineoplastics (differentiating agents, asparaginases, proteasome inhibitors)?

Other antineoplastics (differentiating agents, asparaginases, proteasome inhibitors)

## High alert?

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

An intravenous arsenic compound that cures most acute promyelocytic leukaemia with tretinoin. Key risks: QT prolongation and differentiation syndrome.

Updated Nov 1, 2026

Also called: ATO

## Quick facts

**Group**
[Other antineoplastics (differentiating agents, asparaginases, proteasome inhibitors)](https://durgical.com/en/pharmacology/classes/other-antineoplastics/)

**Target**
PML-RARα fusion protein (and other thiol-containing proteins)

**Used for**
Acute promyelocytic leukaemia

**Key effects**
Nausea · Fatigue · Low potassium and magnesium

**Monitor**
ECG with QTc before starting · Potassium · Weight

**ATC**
L01XX27

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

In solution arsenic trioxide forms arsenious acid, the active trivalent arsenic. It damages and degrades the PML-RARα fusion protein, so APL cells resume maturation, and it triggers apoptosis: APL cells already have high levels of reactive oxygen species, and arsenic adds to them by inhibiting thioredoxin reductase and binding glutathione and other thiols. Combined with tretinoin, which attacks the same fusion protein from the RARα side, it clears the leukaemic clone in most patients.

- Forms active trivalent arsenic in solution
- Degrades the PML-RARα fusion protein
- Raises oxidative stress by binding thiols
- APL cells mature and die by apoptosis

## Indications

- Acute promyelocytic leukaemia with t(15;17) or PML-RARα: with tretinoin in newly diagnosed low-risk disease, and for relapsed or refractory disease. [Acute leukaemia (AML and ALL) →](https://durgical.com/en/conditions/acute-leukaemia/)

## Adverse effects

### Common

- Nausea, vomiting, diarrhoea, abdominal pain
- Fatigue, fever, headache
- Tachycardia and QT prolongation on the ECG
- Low potassium and magnesium, high glucose
- Rising white cell count
- Tingling of the skin, rash, itching

### Serious (rare, important)

- Differentiation syndrome (boxed warning)
- QT prolongation, complete heart block and torsade de pointes (boxed warning)
- Encephalopathy, including Wernicke encephalopathy (boxed warning)
- Hepatotoxicity
- Second cancers (arsenic is a human carcinogen)

## Contraindications

- Allergy to arsenic
- Ventricular arrhythmia or a prolonged QT interval before starting (it is not given until corrected)

## Key interactions

**Other QT-prolonging drugs**
Add to QT prolongation and torsade risk; they are stopped or replaced, or the ECG is checked more often.

**Drugs that cause electrolyte disturbances (e.g. potassium-wasting diuretics)**
Low potassium or magnesium raises the arrhythmia risk; avoided or electrolytes checked more often.

**Other hepatotoxic drugs**
Add to liver injury; liver tests are checked more often.

## What is monitored

- ECG with QTc before starting and regularly during treatment
- Potassium, magnesium and calcium, kept in the normal range
- Liver tests frequently during induction
- Weight, breathing and temperature (differentiation syndrome)
- Neurological status; thiamine if Wernicke encephalopathy is suspected
- Blood counts and glucose

## Administration and safety

- Intravenous infusion over a set time, never as a push; it is diluted before use following the product instructions.
- Electrolytes are corrected and the ECG reviewed before each dose.
- Hazardous drug: prepared and disposed of following cytotoxic handling procedures.
- Name check: arsenic trioxide for leukaemia is a prescription injection, unrelated to homeopathic products that mention arsenic.

## Pregnancy and breastfeeding

Can harm the fetus; effective contraception is used during treatment, and breastfeeding is not advised.

## Nursing care

- Check that the latest ECG and potassium and magnesium results are acceptable before hanging the infusion.
- Watch for palpitations, fainting or a fast irregular pulse.
- Daily weight; report fever, breathlessness or swelling at once.
- Ask about confusion, unsteady gait or eye-movement problems (Wernicke encephalopathy).
- Teaching: avoid pregnancy, report vomiting or diarrhoea that could lower potassium.

## Pharmacokinetics

**Absorption**
Given as an intravenous infusion.

**Distribution**
Widely distributed into tissues.

**Metabolism**
Methylated in the liver by methyltransferases (not CYP enzymes) to less toxic metabolites.

**Elimination**
Mainly in the urine; patients with severe kidney impairment are watched for toxicity.

**Half-life**
About 10 to 14 hours for the active arsenic; its methylated metabolites last longer.

## Memory aid

Arsenic for APL: «A for APL, Arrhythmia, ATRA partner». Check the QT and the K⁺ and Mg²⁺ before every dose.

## Test yourself

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

## Which ECG finding is the main safety concern with arsenic trioxide?

QTc prolongation, which can lead to torsade de pointes.

## Which two electrolytes are corrected before giving arsenic trioxide?

Potassium and magnesium (calcium is also checked).

## Which vitamin is given if confusion and ataxia appear on arsenic trioxide?

Parenteral thiamine, for suspected Wernicke encephalopathy.

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

[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 1

- [Tretinoin](https://durgical.com/en/pharmacology/tretinoin/)

## Related conditions 1

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

[← Back to the class: Other antineoplastics (differentiating agents, asparaginases, proteasome inhibitors)](https://durgical.com/en/pharmacology/classes/other-antineoplastics/)

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

Sources: [DailyMed - ARSENIC TRIOXIDE injection](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c99b01b4-67ff-4793-8375-fe3a21c6c9be) (DailyMed (U.S. National Library of Medicine), 2026); [Arsenic Trioxide Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a608017.html) (MedlinePlus (U.S. National Library of Medicine), 2024); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01XX27) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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