Cytarabine
Antimetabolites
AntimetabolitesHigh 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.
Also called: cytosine arabinoside, ara-C
Quick facts
- Group
- 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.
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) →
- Acute lymphoblastic leukaemia and meningeal leukaemia (intrathecal). Acute leukaemia (AML and ALL) →
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
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).
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.
Connections
← Back to the class: 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 (DailyMed (U.S. National Library of Medicine), 2026); Cytarabine Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.