Uses of Filgrastim (G-CSF)
Filgrastim is primarily used to decrease the incidence of febrile neutropenia and reduce the duration of neutropenia and fever following myelosuppressive chemotherapy in cancer patients. 1
Primary Indications
- Prevention of chemotherapy-induced febrile neutropenia (FN) in patients receiving myelosuppressive chemotherapy, particularly when the risk of FN is ≥20% 1, 2
- Reduction in the duration of severe neutropenia in patients with non-myeloid malignancies receiving myelosuppressive anticancer drugs 1, 3
- Support for dose-intensity maintenance of chemotherapy regimens to avoid dose reductions or treatment delays 1
- Treatment of established febrile neutropenia when used with antibiotics, accelerating neutrophil recovery 4
Additional Clinical Applications
- Mobilization of peripheral blood progenitor cells (PBPCs) for collection and subsequent autologous transplantation 5
- Treatment of severe chronic neutropenia, including Kostmann's syndrome, idiopathic and cyclic neutropenia 6
- Management of neutropenia in post-transplant patients receiving medications like valganciclovir 7
- Treatment of idiosyncratic drug-induced agranulocytosis 6
Mechanism of Action
- Filgrastim is a recombinant human granulocyte colony-stimulating factor (G-CSF) that stimulates the proliferation, differentiation, and function of neutrophil precursors and mature neutrophils 3, 8
- It is administered subcutaneously and works by binding to specific receptors on neutrophil precursors to promote their growth and maturation 1, 6
Dosing and Administration
- Standard dose: 5 μg/kg/day administered subcutaneously 1, 3
- Should be started 1-3 days after completion of chemotherapy (not on the same day) 1, 2
- Continue until post-nadir absolute neutrophil count recovery to normal or near-normal levels (typically ANC ≥2-3 × 10^9/L) 1, 3
- For PBPC mobilization, higher doses (10 μg/kg/day) may be preferable 1
Available Formulations
- Filgrastim (original non-glycosylated G-CSF) 1
- Pegfilgrastim (long-acting form with PEG molecule attached, allowing once-per-cycle dosing) 1, 9
- Biosimilar versions (filgrastim-sndz, tbo-filgrastim, and others) with comparable efficacy to the reference product 1
Clinical Efficacy
- Reduces the incidence of febrile neutropenia by approximately 50% compared to placebo in patients receiving chemotherapy 1
- Decreases infection-related mortality from 3.3% to 1.7% in patients receiving chemotherapy 1
- Shortens the duration of severe neutropenia by approximately 1-2 days compared to placebo 4
- Reduces the risk of prolonged hospitalization by approximately 50% when used with antibiotics for established febrile neutropenia 4
Common Side Effects and Precautions
- Bone pain (most common adverse effect, occurring in approximately 20% of patients) 6
- Potential for splenic rupture (rare but serious complication) 3
- Risk of acute respiratory distress syndrome 3
- Possible allergic reactions 3
Clinical Decision Making
- For primary prophylaxis, use filgrastim in chemotherapy regimens with ≥20% risk of febrile neutropenia 1, 2
- Consider patient risk factors that increase FN risk: prior chemotherapy, abnormal hepatic/renal function, low baseline white blood cell count, and planned delivery of ≥85% of chemotherapy dose 1
- For patients receiving weekly chemotherapy regimens, daily G-CSFs like filgrastim may be more appropriate than long-acting formulations 2
- When treating established neutropenia, filgrastim is preferred over pegfilgrastim due to its shorter half-life and ability to titrate the dose 7