Filgrastim
**Filgrastim** is a recombinant human granulocyte colony-stimulating factor (G-CSF) utilized in veterinary medicine to stimulate the bone marrow to produce neutrophils. Key clinical points: * **Primary Indication:** Used for severe, life-threatening neutropenia (e.g., secondary to parvovirus, chemotherapy-induced myelosuppression, or feline leukemia virus-associated cyclic neutropenia) when intrinsic response is inadequate. * **Immunogenicity Risk:** Because filgrastim is derived from human DNA, it is not species-specific but **can be highly immunogenic** in dogs and cats. Patients may develop neutralizing antibodies against both the exogenous drug and their own endogenous G-CSF, leading to profound, prolonged, and potentially fatal neutropenia. * **Clinical Strategy:** To minimize antibody formation, it is typically administered as a short **"pulse" therapy** (3 to 5 days) only during the critical nadir of neutropenia. * **Cost:** Treatment is highly expensive, which often limits its use in routine veterinary practice.
Mecanismo: Filgrastim acts as a hematopoietic growth factor. * It binds specifically to **G-CSF receptors** located on the surface of myeloid progenitor cells in the bone marrow. * Receptor activation triggers intracellular signaling pathways (such as the **JAK/STAT pathway**) → stimulates the proliferation, differentiation, and activation of progenitor cells exclusively within the **neutrophil-granulocyte lineage**. * **Clinical Pearl:** In addition to increasing the absolute number of circulating mature neutrophils, filgrastim also enhances the functional capacity of these cells, including their phagocytic and bactericidal activities, thereby improving the patient's ability to fight off bacterial infections during periods of severe immunosuppression.
Dosificación por especie
- Adjunctive therapy of neutropenia (secondary to drug induced aplastic pancytopenia) · 5 micrograms/kg SC daily · SC · daily · Pulse therapy of no more than 5 days · To avoid autoantibody formation, pulse therapy is recommended.
- Neutropenia · 1-5 micrograms/kg SC daily · SC · daily · Pulse therapy of no more than 5 days · To avoid autoantibody formation, pulse therapy is recommended.
- Neutropenia · 100,000-500,000 IU (1-5 micrograms)/kg · SC · q24h · 3-5 days · Neutrophil counts typically rise within 24 hours.
- Neutropenia secondary to drug toxicity, infectious diseases, FeLV associated cyclic neutropenia or idiopathic causes · 5 micrograms/kg SC twice daily · SC · twice daily · Pulse therapy of no more than 5 days · Cost and/or development of antibodies usually limit usefulness to a few weeks, but often it is effective for acute or lifethreatening neutropenia.
- Neutropenia · 1-5 micrograms/kg SC daily · SC · daily · Pulse therapy of no more than 5 days · To avoid autoantibody formation, pulse therapy is recommended.
- Adjunctive therapy of neutropenia · 5 micrograms/kg SC daily until neutrophil count exceeds 3,000/mcl for 2 days · SC · daily · Until neutrophil count exceeds 3,000/mcl for 2 days (ideally ≤ 5 days) · To avoid autoantibody formation, pulse therapy is recommended.
- Neutropenia · 100,000-500,000 IU (1-5 micrograms)/kg · SC · q24h · 3-5 days · Neutrophil counts typically rise within 24 hours.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Hypersensitivity to filgrastim
- Patients that have previously developed antibodies to filgrastim with resultant neutropenia
Efectos adversos
- Severe neutropenia (due to autoantibody formation against G-CSF)
- Myelofibrosis (theoretical/reported concern)
- Medullary histiocytosis (theoretical/reported concern)
- Injection site irritation
- Bone pain
- Splenomegaly
- Hypotension
Interacciones farmacológicas
- Antineoplastics · Avoid using filgrastim within 24 hours of administering antineoplastic agents that target rapidly proliferating cells, as it may exacerbate toxicity to the newly stimulated myeloid cells.
- Corticosteroids · May potentiate the release of neutrophils during G-CSF therapy. · moderate
- Lithium · May potentiate the release of neutrophils during G-CSF therapy. · moderate
- Cytotoxic Chemotherapy · Concurrent administration may increase the incidence of adverse effects. The stimulatory effects of G-CSF on haemopoietic precursors render them more susceptible to the effects of chemotherapy. · major
Monitorización
- CBC with platelets, routinely (to monitor neutrophil response and detect potential antibody-induced neutropenia)
Sobredosis
Limited information is available regarding acute toxicity. Because of the high expense of the drug and its apparent limited acute toxic potential, clinically significant overdoses are considered unlikely. If an overdose occurs, monitor CBC closely and provide supportive care.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.