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Fludarabine

  • AntimetabolitesAntimetabolites
  • High alertAn error with this medicine can cause serious harm: double checks and protocols are used.

Purine analogue for chronic lymphocytic leukaemia. It deeply suppresses lymphocytes: infections, autoimmune haemolysis, transfusion graft-versus-host disease.

Updated

Also called: fludarabine phosphate, 2-fluoro-ara-A

Quick facts

Group
Antimetabolites
Target
DNA polymerase α, ribonucleotide reductase and DNA primase (inhibited by fludarabine triphosphate)
Key effects
Myelosuppression · Infections · Nausea
Monitor
Blood counts before and during treatment
ATC
L01BB05

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

Mechanism of action

Fludarabine phosphate is a prodrug. In the blood it loses its phosphate to 2-fluoro-ara-A, which enters cells and is rephosphorylated by deoxycytidine kinase to the active triphosphate. This inhibits DNA polymerase α, ribonucleotide reductase and DNA primase, and is built into DNA and RNA, so DNA synthesis stops and the cell undergoes apoptosis. Lymphocytes are especially sensitive, which explains both its activity in chronic lymphocytic leukaemia and its profound, long-lasting immunosuppression.

  1. Fludarabine phosphate is dephosphorylated to 2-fluoro-ara-A
  2. Deoxycytidine kinase makes the active triphosphate
  3. It blocks DNA polymerase, primase and ribonucleotide reductase
  4. Leukaemic and normal lymphocytes die

Indications

  • B-cell chronic lymphocytic leukaemia that has not responded to an alkylating-agent regimen (licensed use); also used in combination regimens. Chronic lymphocytic leukaemia →

Adverse effects

Common

  • Myelosuppression (anaemia, thrombocytopenia, neutropenia)
  • Infections, including opportunistic infections, from long-lasting lymphopenia
  • Nausea, vomiting, fatigue
  • Fever

Contraindications

  • The label lists no absolute contraindications; it is not given in severe renal impairment or with pentostatin

Key interactions

Pentostatin
Unacceptably high rate of fatal pulmonary toxicity: not combined.
Other myelosuppressive or immunosuppressive treatment
Deeper and longer immunosuppression and infection risk.

What is monitored

  • Blood counts before and during treatment
  • Signs of haemolysis (haemoglobin, bilirubin, reticulocytes, direct antiglobulin test)
  • Creatinine clearance before each course
  • Neurological status; signs of infection

Administration and safety

  • Only irradiated blood products are transfused during and after treatment.
  • The dose depends on kidney function, which is checked before each course.
  • Hazardous drug: chemotherapy handling precautions.

Pregnancy and breastfeeding

Can cause fetal harm; pregnancy is avoided during treatment.

Nursing care

  • Flag the chart and blood bank: irradiated blood products only.
  • Watch for dark urine, jaundice and sudden fatigue (haemolysis).
  • Infection precautions; report fever promptly.
  • Tumour lysis precautions for patients with a high leukaemia burden (fluids, labs).

Pharmacokinetics

Absorption
Intravenous (an oral form exists in some countries).
Metabolism
Dephosphorylated in plasma, then activated inside cells.
Elimination
The kidneys clear the active nucleoside; clearance follows creatinine clearance, so the dose is reduced in renal impairment and it is not given in severe impairment.

Test yourself

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

Why must blood products be irradiated for patients treated with fludarabine?

To prevent transfusion-associated graft-versus-host disease in these severely immunosuppressed patients.

Which autoimmune complication can fludarabine trigger?

Autoimmune haemolytic anaemia, which can be fatal.

Which drug combination with fludarabine is avoided because of fatal lung toxicity?

Pentostatin.

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More Pharmacology questions →

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 - FLUDARABINE PHOSPHATE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Fludarabine 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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