FLUDARABINE PHOSPHATE
Clinical safety rating: avoid
Contraindicated (not allowed)
Fludarabine phosphate is a purine analog that inhibits DNA synthesis by interfering with ribonucleotide reductase and DNA polymerase, leading to apoptosis in lymphocytes.
| Metabolism | Fludarabine phosphate is dephosphorylated in serum to 2-fluoro-ara-A, which is then phosphorylated intracellularly to the active triphosphate. Metabolism is primarily hepatic via deamination by adenosine deaminase to 2-fluoro-ara-hypoxanthine. |
| Excretion | Renal excretion of the active metabolite 2-fluoro-ara-A accounts for approximately 60% of drug elimination. Biliary/fecal elimination is minimal (<5%). |
| Half-life | Terminal half-life of 2-fluoro-ara-A is approximately 20 hours (range 10–30 hours). Clinical context: accumulation occurs with repeated dosing, requiring dose adjustment in renal impairment (CrCl <30 mL/min). |
| Protein binding | Fludarabine phosphate is approximately 19–29% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Vd is approximately 2.2 L/kg (range 1.5–3.0 L/kg), indicating extensive tissue distribution, including accumulation in lymphocytes and bone marrow. |
| Bioavailability | Oral bioavailability is approximately 55–75% (mean 65%) compared to IV administration. Bioavailability is highly variable and increased when taken with food. |
| Onset of Action | IV administration: Onset of antineoplastic effect is typically observed within 1–2 weeks, with maximal response after several cycles. Oral bioavailability: Onset similar to IV but delayed due to absorption time. |
| Duration of Action | Myelosuppression persists for 2–4 weeks. Lymphocyte depletion may last for 6–12 months post-treatment. |
| Molecular Weight | 365.19 |
25 mg/m2 intravenously over 30 minutes daily for 5 consecutive days every 28 days.
| Dosage form | INJECTABLE |
| Renal impairment | For CrCl 30-70 mL/min: reduce dose by 20% and monitor closely. For CrCl <30 mL/min: contraindicated. |
| Liver impairment | No specific dose adjustment for Child-Pugh class A or B; use caution in severe hepatic impairment (Child-Pugh class C) with dose reduction based on bilirubin and transaminases. |
| Pediatric use | Not established; safety and efficacy have not been determined in pediatric patients. |
| Geriatric use | Increased risk of severe toxicity (myelosuppression, neurotoxicity); consider dose reduction based on renal function (CrCl) and overall status. No specific adjustment by age alone. |
| 1st trimester | Fludarabine phosphate is contraindicated in the first trimester due to teratogenic effects observed in animal studies and potential for fetal harm. |
| 2nd trimester | Use only if clearly needed and benefit outweighs risk. May cause fetal harm; limited human data. |
| 3rd trimester | Use only if clearly needed. May cause neonatal myelosuppression and other adverse effects. |
Clinical note
Other bone marrow suppressants may have additive effects Can cause severe myelosuppression and neurotoxicity.
| Placental transfer | Fludarabine crosses the placenta. In animal studies, it was transferable and associated with embryotoxicity and teratogenicity. |
| Breastfeeding | Fludarabine is excreted in human milk. Because of the potential for serious adverse reactions from fludarabine in breastfed infants, breastfeeding should be discontinued during therapy and for at least 3 months after the last dose. |
■ FDA Black Box Warning
Fludarabine phosphate can cause severe neurologic effects including blindness, coma, and death, especially at higher doses. Dose-dependent severe bone marrow suppression (anemia, thrombocytopenia, neutropenia) and autoimmune hemolytic anemia have been reported.
| Common Effects | Myelosuppression |
| Serious Effects |
Hypersensitivity to fludarabine or any component of the formulationSevere hepatic impairment (Child-Pugh class C)Severe renal impairment (creatinine clearance <30 mL/min) unless benefit outweighs risk
| Precautions | Severe bone marrow suppression, particularly neutropenia, thrombocytopenia, and anemia; autoimmune hemolytic anemia; neurotoxicity including delayed blindness, coma, and death; tumor lysis syndrome; pulmonary toxicity; and increased risk of opportunistic infections. |
| Food/Dietary |
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| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: Known to cause fetal harm, including congenital malformations (e.g., skeletal, cardiac) and embryolethality based on animal studies and case reports. Second and third trimesters: Risk of myelosuppression, intrauterine growth restriction, and potential neurodevelopmental effects. Avoid use during pregnancy unless no safer alternative. |
| Fetal Monitoring | Monitor complete blood count (CBC) with differential weekly during therapy for maternal myelosuppression. Assess for fetal growth restriction and congenital anomalies via serial ultrasound if exposure occurs. Monitor for maternal infections and consider fetal echocardiography if first-trimester exposure. Perform newborn hematologic assessment at delivery. |
| Fertility Effects | May impair fertility in both sexes. In males, reversible or permanent oligospermia or azoospermia. In females, possible ovarian failure (amenorrhea, elevated gonadotropins), with reduced fertility and earlier menopause. Effects may persist after discontinuation. |
| No clinically significant food interactions. Maintain adequate hydration to reduce risk of tumor lysis syndrome. |
| Clinical Pearls | Fludarabine is a purine analog used in CLL and low-grade NHL. Requires dose adjustment for CrCl <30 mL/min. Premedicate with antiemetics. Infusion reactions may occur; monitor for fever, chills. Myelosuppression is dose-limiting, especially thrombocytopenia and lymphopenia. Prolonged immunosuppression can lead to opportunistic infections, including PCP and HSV. Tumor lysis syndrome risk is high in patients with high tumor burden. Pneumocystis jirovecii and herpes virus prophylaxis recommended during and after treatment. Avoid use in patients with severe renal impairment (CrCl <30 mL/min). |
| Patient Advice | This medication may lower your ability to fight infections. Report any signs of infection such as fever, sore throat, or cough. · You will have frequent blood tests to monitor your blood cell counts. · Use effective contraception during treatment and for at least 6 months after. · Avoid live vaccines during treatment. · Do not take aspirin or NSAIDs without consulting your doctor due to bleeding risk. · Report any unusual bleeding, bruising, or tiredness. · This drug can cause nausea and vomiting; take antiemetics as prescribed. |