Purine analogue Pregnancy: Based on its mechanism of action, fludarabine phosphate can cause fetal harm when administered to a pregnant woman. There are no adequate and well-controlled studies in pregnant women. Fludarabine phosphate was embryolethal and teratogenic in rats and rabbits. If used during pregnancy, or if the patient becomes pregnant while taking the drug, she should be apprised of the potential hazard to the fetus. Women of childbearing potential should be advised to avoid becoming pregnant.

Fludarabine phosphate (Specialist drug)

Brand names: Fludara

Fludarabine phosphate is a purine analogue antimetabolite cytotoxic used principally in chronic lymphocytic leukaemia and some lymphomas.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 25 mg/m2

Route: Intravenous infusion over a period of approximately 30 minutes. Fludarabine phosphate injection contains no antimicrobial preservative and should be used within 8 hours of opening; it should not be mixed with other drugs.

Frequency: Daily for five consecutive days; each 5-day course of treatment should commence every 28 days

Max: 25 mg/m2/day for 5 days is the recommended adult dose; the label explicitly warns against higher dose levels because of severe dose-dependent neurotoxicity

DURATION: the optimal duration of treatment has not been clearly established. It is recommended that three additional cycles be administered following the achievement of a maximal response, and then the drug discontinued. DOSE MODIFICATION: the dose may be decreased or delayed based on evidence of haematologic or non-haematologic toxicity; physicians should consider delaying or discontinuing the drug if neurotoxicity occurs. PREDISPOSING FACTORS: advanced age, renal impairment and bone marrow impairment may predispose to increased toxicity — such patients should be monitored closely for excessive toxicity and the dose modified accordingly. DOSE-DEPENDENT NEUROTOXICITY (boxed-warning territory): dose levels approximately 4 times greater than the CLL dose (96 mg/m2/day for 5 to 7 days versus 25 mg/m2/day for 5 days) were associated with delayed blindness, coma and death, appearing 21 to 60 days after the last dose, in 13 of 36 patients (36%) who received the high dose. TRANSFUSION: use only irradiated blood products for transfusions, because of transfusion-associated graft-versus-host disease. PAEDIATRIC: data submitted to the FDA were insufficient to establish efficacy in any childhood malignancy. The label describes only investigational regimens in 62 paediatric patients (median age 10, range 1 to 21) — for paediatric lymphocytic leukaemia a loading bolus of 10.5 mg/m2/day followed by a continuous infusion of 30.5 mg/m2/day for 5 days; in 12 paediatric patients with solid tumours, dose-limiting myelosuppression occurred with a loading dose of 8 mg/m2/day followed by a continuous infusion of 23.5 mg/m2/day for 5 days, and the maximum tolerated dose was a loading dose of 7 mg/m2/day followed by a continuous infusion of 20 mg/m2/day for 5 days. These are body-surface-area regimens, not per-kg doses, and are not an approved paediatric recommendation — a children's formulary and specialist protocol must be used. SOURCE: no UK SPC was fetched in this bundle; this draft is distilled from the US fludarabine phosphate injection prescribing information and must be verified against the UK SPC. Fetched sections were truncated at the source-fetch limit.

Dose adjustments

Renal

Starting dose adjustment by creatinine clearance (Cockcroft-Gault): 80 ml/min or more — 25 mg/m2 (full dose); 50 to 79 ml/min — 20 mg/m2; 30 to 49 ml/min — 15 mg/m2; less than 30 ml/min — do not administer. Renally impaired patients should be monitored closely for excessive toxicity and the dose modified accordingly.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

None stated — the US label section 4 Contraindications reads 'None'

Side effects

Myelosuppression — neutropenia, thrombocytopenia and anaemia (incidence over 30%); severe bone marrow suppression requires blood count monitoring before and during treatment
Fever, chills and infection, including serious opportunistic infections, and pneumonia
Nausea, vomiting and diarrhoea; also mucositis and anorexia
Fatigue, weakness and malaise; cough
Dose-dependent neurologic toxicity — delayed blindness, coma, seizures, agitation and confusion at high doses; also tumour lysis syndrome and transfusion-associated graft-versus-host disease

Interactions

Pentostatin — the combination is not recommended because of the risk of severe and fatal pulmonary toxicity

Clinical monograph

How it works

Its active metabolite is incorporated into DNA and inhibits DNA polymerase, ribonucleotide reductase and DNA primase, halting DNA synthesis and inducing apoptosis in lymphoid cells.

Prescribing in practice

It causes profound and prolonged lymphopenia with a high risk of opportunistic infection, so infection prophylaxis and use of irradiated blood products to prevent transfusion-associated graft-versus-host disease are required.
Administer only under specialist haematology supervision, with dose reduction in renal impairment where it is contraindicated when severe.
Severe, sometimes fatal autoimmune haemolytic anaemia and neurotoxicity can occur, requiring close vigilance.

Monitoring

Monitor full blood count, renal function and for signs of infection, haemolysis and neurological toxicity throughout treatment.

Counselling the patient

Report fever or any sign of infection urgently as your immune system is suppressed for a prolonged period.
Always inform staff that you need irradiated blood if a transfusion is required.
Effective contraception is essential during and after treatment.

Evidence & guidelines

Fludarabine-based regimens are supported by landmark chronic lymphocytic leukaemia trials and NICE guidance, demonstrating improved response rates over earlier alkylator therapy.

Reference: SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways