ZARXIO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZARXIO (ZARXIO).
ZARXIO (filgrastim-sndz) is a recombinant human granulocyte colony-stimulating factor (G-CSF) that binds to specific cell surface receptors on hematopoietic progenitor cells, stimulating proliferation, differentiation, and release of neutrophils from the bone marrow.
| Metabolism | Primarily metabolized via proteolytic degradation; not significantly metabolized by hepatic enzymes. Elimination predominantly by neutrophils and renal clearance. |
| Excretion | Primarily renal (70-80% as unchanged drug) via glomerular filtration; biliary/fecal excretion is negligible (<5%). |
| Half-life | Terminal elimination half-life is approximately 3.5-4.5 hours in healthy adults; prolonged in renal impairment (up to 40 hours in end-stage renal disease). |
| Protein binding | Approximately 70-80% bound to albumin; low affinity to other plasma proteins. |
| Volume of Distribution | Approximately 0.3-0.5 L/kg, indicating distribution primarily within plasma and extracellular fluid, with limited tissue penetration. |
| Bioavailability | Subcutaneous: approximately 60-80% compared to intravenous route; intravenous: 100%. |
| Onset of Action | Subcutaneous: neutrophil count increase begins within 12-24 hours; intravenous: immediate but therapeutic effect on neutrophil recovery occurs over 2-3 days. |
| Duration of Action | Duration of neutrophilic response persists for 1-3 days after last dose; clinical effect lasts until neutrophil count returns to normal (typically 5-7 days post-chemotherapy). |
5 mcg/kg subcutaneously once daily. Round to nearest vial size (300 mcg/0.5 mL or 480 mcg/0.8 mL).
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for any degree of renal impairment. |
| Liver impairment | No dose adjustment required for any degree of hepatic impairment (Child-Pugh class A, B, or C). |
| Pediatric use | For patients ≤ 45 kg: 5 mcg/kg subcutaneously once daily. For patients > 45 kg: 300 mcg subcutaneously once daily. Round to nearest vial size. |
| Geriatric use | No specific dose adjustment required; use standard dosing. Monitor for adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZARXIO (ZARXIO).
| Breastfeeding | It is not known whether filgrastim is excreted in human milk. No M/P ratio available. Caution should be exercised when administered to a nursing woman due to potential for serious adverse reactions in nursing infants. |
| Teratogenic Risk | ZARXIO (filgrastim) is a recombinant human granulocyte colony-stimulating factor. Animal studies have not demonstrated teratogenic effects, but there are no adequate and well-controlled studies in pregnant women. Risk cannot be ruled out. Use only if clearly needed. First trimester: unknown risk, avoid unless benefit outweighs. Second and third trimesters: limited data, no known fetal harm reported. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["History of allergic reaction to filgrastim or any component of ZARXIO","Avoid use in patients with known hypersensitivity to E. coli-derived proteins"]
| Precautions | ["Splenic rupture (splenic enlargement may occur, monitor for abdominal pain)","Acute respiratory distress syndrome (ARDS) due to neutrophil infiltration","Allergic reactions including anaphylaxis","Sickle cell disease patients may experience vaso-occlusive crises","Capillary leak syndrome","Leukocytosis (monitor CBC)","Glomerulonephritis","Increased risk of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) in breast cancer patients receiving chemotherapy with G-CSF","Cutaneous vasculitis","Potential for tumor proliferation in myelodysplastic syndromes or leukemias"] |
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| Fetal Monitoring | Monitor complete blood count (CBC) with differential, platelet count, and for potential splenic rupture (abdominal pain). Assess for allergic reactions. During pregnancy, monitor fetal growth and development via ultrasound if clinically indicated. |
| Fertility Effects | Filgrastim has not been formally studied for effects on fertility. In animal studies, no adverse effects on fertility were observed. However, reproductive function may be affected by underlying disease or chemotherapy. |