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[Pharmacology](https://durgical.com/en/pharmacology/) · [Myeloid colony-stimulating factors](https://durgical.com/en/pharmacology/classes/myeloid-colony-stimulating-factors/)

# Pegfilgrastim

Filgrastim joined to polyethylene glycol so it lasts longer: one injection per chemotherapy cycle to prevent febrile neutropenia.

Updated 2026-11-01

- Class: [Myeloid colony-stimulating factors](https://durgical.com/en/pharmacology/classes/myeloid-colony-stimulating-factors/)
- Receptor: Granulocyte colony-stimulating factor receptor (G-CSFR)
- ATC code: L03AA13
- WHO Model List of Essential Medicines

◎**Granulocyte colony-stimulating factor receptor (G-CSFR)**Pegfilgrastim

ⓘ The figure shows human G-CSF bound to its receptor; pegfilgrastim is the same protein with a polyethylene glycol chain attached, which is not in the crystal.

**Target in 3D:** Granulocyte colony-stimulating factor receptor (G-CSFR). PDB structure 2D9Q (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/2D9Q) · Drag to rotate · pinch to zoom

## Mechanism of action

Pegfilgrastim is filgrastim with a polyethylene glycol chain attached. The larger molecule is cleared less by the kidneys and acts for longer, so one injection covers a whole chemotherapy cycle. Its action on the G-CSF receptor is the same as filgrastim.

- 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

**Elimination**
Less renal clearance than filgrastim

**Half-life**
Prolonged, allowing a single dose per chemotherapy cycle

## Indications

- Prevention of febrile neutropenia in patients receiving myelosuppressive chemotherapy [Febrile neutropenia →](https://durgical.com/en/conditions/febrile-neutropenia/)

## Adverse effects

### Common

- Bone pain
- Pain in the limbs
- Injection-site reactions

### Serious (rare, important)

- Splenic rupture: left upper abdominal or left shoulder-tip pain
- Acute respiratory distress or lung bleeding: fever, breathlessness, coughing blood
- Severe allergic reactions
- Sickle cell crises in people with sickle cell disease
- Kidney inflammation (glomerulonephritis): less urine, dark urine, swelling

## Contraindications

- Serious allergy to pegfilgrastim or filgrastim

## Key interactions

**Myelosuppressive chemotherapy**
Given after the chemotherapy and well before the next cycle, so stimulated cells are not exposed to cytotoxic drugs

## What is monitored

- Complete blood count
- Bone pain and spleen-related symptoms

## Administration and safety

- Single subcutaneous injection per cycle, typically the day after chemotherapy
- Not given in the period shortly before the next chemotherapy dose

## 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.

## Memory aid

PEG = «Put Every Gap between cycles»: one shot after chemo, lasts the whole gap.

## Test yourself

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

## What does the polyethylene glycol chain change?

It prolongs action and reduces renal clearance.

## How often is it given in chemotherapy?

Once per cycle, after the chemotherapy.

## Which receptor does it act on?

The G-CSF receptor, like filgrastim.

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## Related drugs

- [Filgrastim](https://durgical.com/en/pharmacology/filgrastim/)

## Related conditions

- [Febrile neutropenia](https://durgical.com/en/conditions/febrile-neutropenia/)

[← Back to the class: Myeloid colony-stimulating factors](https://durgical.com/en/pharmacology/classes/myeloid-colony-stimulating-factors/)

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

Sources: [Pegfilgrastim Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a607058.html) (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](https://atcddd.fhi.no/atc_ddd_index/?code=L03AA13) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/pegfilgrastim/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/pegfilgrastim/