FYLNETRA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FYLNETRA (FYLNETRA).
FYLNETRA (filgrastim-ayow) is a granulocyte colony-stimulating factor (G-CSF) analog that binds to the G-CSF receptor on neutrophils and their precursors, stimulating proliferation, differentiation, and functional activation of neutrophils.
| Metabolism | Filgrastim is primarily cleared by neutrophil-mediated endocytosis and degradation; renal and hepatic metabolism play minor roles. No specific cytochrome P450 enzymes are involved. |
| Excretion | Renal (primarily, as unchanged drug and metabolites, minor biliary/fecal) |
| Half-life | Terminal elimination half-life approximately 3.5 hours (range 2–5 hours); supports daily dosing in most patients for myelosuppressive chemotherapy. |
| Protein binding | Approximately 60% bound to serum proteins (primarily albumin). |
| Volume of Distribution | Approximately 0.5 L/kg; distributes into extracellular fluid, not extensively into tissues. |
| Bioavailability | Subcutaneous: 100% (absolute bioavailability). |
| Onset of Action | Subcutaneous: Onset within 12–24 hours based on neutrophil count increase. |
| Duration of Action | Duration of effect approximately 7–10 days; clinical monitoring of absolute neutrophil count (ANC) recommended. |
3.6 mg/kg subcutaneously once daily for up to 14 days. Dose based on absolute neutrophil count.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for GFR ≥15 mL/min. Insufficient data for GFR <15 mL/min. |
| Liver impairment | No dose adjustment recommended for Child-Pugh A, B, or C. Monitor neutrophil counts. |
| Pediatric use | Same 3.6 mg/kg subcutaneously once daily for patients ≥1 year and ≤43 kg. For >43 kg, fixed 300 mg subcutaneously once daily. |
| Geriatric use | No specific dose adjustment. Use same dosing as adults; monitor for adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FYLNETRA (FYLNETRA).
| Breastfeeding | It is unknown whether pegfilgrastim is excreted in human milk. As many drugs are excreted in human milk, caution should be exercised when FYLNETRA is administered to a nursing woman. The M/P ratio is not established. The manufacturer recommends discontinuing breastfeeding during treatment due to potential serious adverse reactions in the infant. However, clinical considerations may allow breastfeeding if the drug is used for a short duration and the infant is monitored for adverse effects such as neutropenia. |
| Teratogenic Risk | FYLNETRA (pegfilgrastim) is a recombinant granulocyte colony-stimulating factor. Animal studies in pregnant rats and rabbits administered pegfilgrastim at doses up to 2-10 times the human dose (based on body surface area) showed no evidence of fetal harm. However, there are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, FYLNETRA should be used during pregnancy only if clearly needed. First trimester: no known risk based on animal data; Second trimester: no known risk; Third trimester: no known risk. However, fetal granulocytopenia has been reported with filgrastim use in pregnant women in rare cases. |
■ FDA Black Box Warning
FYLNETRA is not recommended for doses exceeding 5 mcg/kg/day in patients with severe chronic neutropenia due to the risk of splenic rupture. Patients with severe chronic neutropenia who have received filgrastim have developed acute myeloid leukemia or myelodysplastic syndrome; monitor for signs of hematologic abnormalities.
| Serious Effects |
["History of serious allergic reactions to filgrastim products (e.g., anaphylaxis, angioedema)","Hypersensitivity to the active substance or any excipients in FYLNETRA"]
| Precautions | ["Splenic rupture: Evaluate patients with left upper abdominal pain or shoulder tip pain","Acute respiratory distress syndrome (ARDS): Monitor for pulmonary infiltrates and respiratory distress","Severe allergic reactions: Discontinue permanently if anaphylactic reaction occurs","Sickle cell crisis: Use caution in patients with sickle cell trait or disease","Glomerulonephritis: Monitor for hematuria, proteinuria, and renal function","Capillary leak syndrome: Discontinue and manage symptomatically","Myelodysplastic syndrome and acute myeloid leukemia: Increased risk in patients with severe chronic neutropenia; monitor blood counts","Thrombocytopenia: Monitor platelet counts","Leukocytosis: Monitor white blood cell counts and discontinue if >100,000/mcL"] |
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| Fetal Monitoring | Monitor maternal complete blood count (CBC) with differential, particularly absolute neutrophil count (ANC), to assess response and risk of leukocytosis. Monitor for signs of splenic rupture (e.g., left upper quadrant pain, shoulder tip pain) and acute respiratory distress syndrome (ARDS). Fetal monitoring: standard obstetric ultrasound if used in pregnancy; consider monitoring for fetal growth and well-being due to potential myelosuppressive effects. No specific fetal monitoring required beyond routine prenatal care. |
| Fertility Effects | Pegfilgrastim has been associated with reduced fertility in animal studies. In female rats administered pegfilgrastim at doses approximately 2 times the human dose (based on body surface area), there was a decrease in fertility and implantation rates. In male rats, no significant effects on fertility were observed at doses up to 2 times the human dose. In humans, there are no adequate studies on fertility. However, as a growth factor, it may affect ovarian function and fertility, especially in patients undergoing chemotherapy. Use with caution in patients attempting conception. |