Pharmacology · Myeloid colony-stimulating factors

Filgrastim !

Recombinant G-CSF that raises neutrophils and shortens neutropenia after chemotherapy, in transplants and in severe chronic neutropenia.

Updated 2026-11-01

Class: Myeloid colony-stimulating factors
Receptor: Granulocyte colony-stimulating factor receptor (G-CSFR)
ATC code: L03AA02
WHO Model List of Essential Medicines

Also called: recombinant granulocyte colony-stimulating factor (G-CSF)

Granulocyte colony-stimulating factor receptor (G-CSFR)Filgrastim

The figure shows human G-CSF (the same protein as filgrastim, which is made in bacteria) bound to its receptor.

Target in 3D: Granulocyte colony-stimulating factor receptor (G-CSFR). PDB structure 2D9Q (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Filgrastim is human granulocyte colony-stimulating factor produced in Escherichia coli. It binds the G-CSF receptor on neutrophil progenitors, increasing their production, maturation and release from the marrow, and enhances the function of mature neutrophils.

The drug binds the G-CSF receptor on myeloid progenitors
JAK–STAT signalling drives neutrophil production and maturation
Neutrophils are released sooner from the marrow
Neutropenia is shorter, so fewer infections

Pharmacokinetics

Absorption: Subcutaneous or intravenous
Elimination: Shorter-acting than pegfilgrastim, so it is given daily

Indications

Prevention of febrile neutropenia after myelosuppressive chemotherapy Febrile neutropenia →
Severe chronic neutropenia Neutropenia and drug-induced agranulocytosis →
After bone marrow transplantation, and to mobilise stem cells for collection

Adverse effects

Common

Bone, back and limb pain
Injection-site redness or swelling
Headache, rash

Contraindications

Serious allergy to filgrastim or to proteins made in E. coli

Key interactions

Myelosuppressive chemotherapy given the same day: Stimulated, dividing myeloid cells are more sensitive to cytotoxic drugs, so it is started after chemotherapy

What is monitored

Complete blood count with neutrophils
Spleen-related pain and breathing
Urine and kidney function if swelling or dark urine appear

Administration and safety

Subcutaneous injection (or intravenous infusion), started after chemotherapy, not during it
Biosimilars and pegylated forms differ in schedule; check the exact product

Nursing care

Check the complete blood count as ordered
Expect bone pain; report left upper abdominal or shoulder-tip pain at once
Teach that infections can still occur: report fever or chills
Teach subcutaneous injection and safe disposal if given at home

Pregnancy and breastfeeding

Human data are limited; it is used in pregnancy when the benefit justifies it.

Test yourself

Think of the answer, then tap the question to see it.

Which receptor does filgrastim act on?

The G-CSF receptor on neutrophil progenitors.

Which pain must be reported at once?

Left upper abdominal or left shoulder-tip pain (splenic rupture).

In which inherited blood disease can it trigger crises?

Sickle cell disease.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Filgrastim Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 45 (McGraw Hill, 2023); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 33 (McGraw Hill, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.