[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/) › Cytarabine

# Cytarabine

## Antimetabolites?

Antimetabolites

## High alert?

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

A cytidine look-alike that, once phosphorylated, stops DNA polymerase. It is the backbone of acute myeloid leukaemia treatment.

Updated Nov 1, 2026

Also called: cytosine arabinoside, ara-C

## Quick facts

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

**Target**
DNA polymerase (inhibited by ara-CTP, which is also built into DNA)

**Used for**
Acute myeloid · Acute lymphoblastic leukaemia

**Key effects**
Severe myelosuppression · Nausea · Liver enzyme rises

**Monitor**
Daily blood counts during induction · Eyes

**ATC**
L01BC01

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

Cytarabine is cytidine with an arabinose sugar instead of ribose. Inside the cell deoxycytidine kinase and other kinases convert it to ara-CTP, which inhibits DNA polymerase and is built into new DNA, where it blocks chain elongation. It acts only in the S phase. Cytidine deaminase converts it to inactive ara-U; the balance between the activating kinase and this deaminase helps decide whether a leukaemia is sensitive or resistant.

- Deoxycytidine kinase phosphorylates cytarabine to ara-CTP
- Ara-CTP inhibits DNA polymerase
- It is built into DNA and halts chain growth (S phase)
- Cytidine deaminase inactivates it to ara-U

## Indications

- Acute myeloid (non-lymphocytic) leukaemia: induction and consolidation. [Acute leukaemia (AML and ALL) →](https://durgical.com/en/conditions/acute-leukaemia/)
- Acute lymphoblastic leukaemia and meningeal leukaemia (intrathecal). [Acute leukaemia (AML and ALL) →](https://durgical.com/en/conditions/acute-leukaemia/)

## Adverse effects

### Common

- Severe myelosuppression
- Nausea, vomiting, mouth ulcers, diarrhoea
- «Cytarabine syndrome»: fever, myalgia, bone pain, rash, conjunctivitis and malaise hours after a dose
- Liver enzyme rises

### Serious (rare, important)

- Cerebellar toxicity (ataxia, slurred speech), confusion and somnolence with high-dose regimens
- Haemorrhagic conjunctivitis and corneal toxicity with high doses, prevented with corticosteroid eye drops
- Pancreatitis, especially after asparaginase
- Paralysis and spinal cord toxicity after intrathecal use, more likely when combined with intravenous doses

## Contraindications

- Hypersensitivity to cytarabine

## Key interactions

**Digoxin**
Combination chemotherapy containing cytarabine has lowered digoxin levels; levels are monitored.

**Gentamicin**
Laboratory antagonism against Klebsiella pneumoniae: infection response is watched closely.

**Other myelosuppressive chemotherapy**
Deeper and longer cytopenias.

## What is monitored

- Daily blood counts during induction
- Liver and kidney function
- Cerebellar checks (gait, handwriting, speech) before each high-dose infusion
- Eyes: redness, pain, light sensitivity

## Administration and safety

- Only preservative-free cytarabine is used intrathecally; formulations with benzyl alcohol are not used for high-dose or intrathecal treatment.
- Corticosteroid eye drops are given with high-dose regimens to protect the conjunctiva and cornea.
- Hazardous drug: chemotherapy handling precautions.

## Pregnancy and breastfeeding

Can cause fetal harm and is teratogenic in animals; pregnancy is avoided during treatment.

## Nursing care

- Assess coordination, speech and nystagmus before each high-dose dose; hold and report any cerebellar sign.
- Give the eye drops on schedule and ask about eye pain or blurred vision.
- Neutropenic precautions; act fast on fever.
- Mouth care for mucositis; antiemetics as prescribed.

## Pharmacokinetics

**Absorption**
Not active by mouth: given intravenously, subcutaneously or intrathecally (preservative-free form only).

**Distribution**
Low levels in cerebrospinal fluid after an intravenous dose; intrathecal dosing reaches the meninges directly.

**Metabolism**
Deaminated to inactive ara-U; there is little deaminase in cerebrospinal fluid.

**Elimination**
Urine, mostly as ara-U.

**Half-life**
Biphasic: a fast distribution phase, then elimination over about 1 to 3 hours (label).

## Memory aid

«ARA-C: Ataxia, Red eyes, AML, Cerebellum»: high doses hit the cerebellum and conjunctiva; steroid eye drops protect.

## Test yourself

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

## Which enzyme activates cytarabine and which one inactivates it?

Deoxycytidine kinase activates it (to ara-CTP); cytidine deaminase inactivates it (to ara-U).

## Which leukaemia is cytarabine best known for?

Acute myeloid leukaemia, as the backbone of induction and consolidation.

## Which neurological sign is checked before each high-dose cytarabine infusion?

Cerebellar function: gait, speech, nystagmus, handwriting.

## Why are corticosteroid eye drops given with high-dose cytarabine?

To prevent haemorrhagic conjunctivitis and corneal toxicity.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/cytarabine/)

[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 3

- [Fludarabine](https://durgical.com/en/pharmacology/fludarabine/)
- [Gemcitabine](https://durgical.com/en/pharmacology/gemcitabine/)
- [Mercaptopurine](https://durgical.com/en/pharmacology/mercaptopurine/)

## 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: [DailyMed - CYTARABINE injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e3a8c0e9-19ed-49b7-8464-11e8806f47fd) (DailyMed (U.S. National Library of Medicine), 2026); [Cytarabine Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682222.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01BC01) (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/cytarabine/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/cytarabine/