Pegfilgrastim

What pegfilgrastim is and how it works

Pegfilgrastim is a long-acting, laboratory-made version of a protein your body naturally produces (granulocyte colony-stimulating factor, or G-CSF) that stimulates the bone marrow to produce more white blood cells (neutrophils). It is given as a single injection under the skin, once per chemotherapy cycle, to help reduce the risk of infection from low white blood cell counts (neutropenia) after certain cancer chemotherapy. (1) (2)

Pegfilgrastim does not carry a formal boxed warning -- confirmed directly from the current US label, not assumed -- but it does carry several real, serious risks that your care team will discuss with you and watch for: a rare but serious risk of spleen rupture, a rare lung condition called acute respiratory distress syndrome (ARDS), serious allergic reactions, and other less common but serious effects. Because of this, you will be told what warning signs to watch for (such as pain in your upper left abdomen or shoulder, or new breathing difficulty) and to contact your care team promptly if they occur.

Mechanism of action: how pegfilgrastim works

Pegfilgrastim is filgrastim (recombinant human G-CSF) conjugated to a polyethylene glycol (PEG) molecule, which reduces renal clearance and extends its half-life, allowing a single injection to cover an entire chemotherapy cycle rather than requiring daily injections (as with unmodified filgrastim). It binds G-CSF receptors on neutrophil precursors, stimulating their proliferation and differentiation. (1) (2)

What pegfilgrastim is used for

Before taking pegfilgrastim

Do not take / not appropriate for

• Do not receive pegfilgrastim if you have a history of a serious allergic reaction (including anaphylaxis) to pegfilgrastim or to filgrastim. (all countries) (1) (2)

Tell your clinician about

• Any history of sickle cell disorder -- severe and sometimes fatal sickle cell crises have occurred with this medicine.
• Any history of spleen problems or an enlarged spleen.
• Any history of kidney problems.
• Any lung problems, including a history of pneumonia or ARDS.
• Whether you are pregnant, plan to become pregnant, or are breastfeeding.
• Any known allergy to latex, since some delivery devices contain latex-derived components (check your specific product's information).

How to take pegfilgrastim

• Given as a single injection under the skin (subcutaneously), usually into the abdomen, thigh, or upper arm, once per chemotherapy cycle.
• Must be given at least 24 hours after your chemotherapy dose, and not in the 14 days before your next chemotherapy dose -- your care team will time this precisely.
• May be given by a healthcare professional, or, in some markets and situations, self-administered or given by a caregiver at home using a pre-filled syringe or on-body injector device -- always exactly as your care team trains and directs.
• Do not change the timing or skip this injection on your own without checking with your care team, since correct timing relative to chemotherapy affects both safety and effectiveness.

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Because pegfilgrastim is timed precisely relative to your chemotherapy cycle, contact your care team promptly if a dose is missed or its timing is in question -- do not decide on your own whether or when to give a missed dose.

Overdose

Seek prompt advice from your care team if you think an incorrect dose was given or self-administered. Report any new or worsening symptoms, particularly bone pain, to your care team. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Serious warnings

Interactions

• Cytotoxic chemotherapy: pegfilgrastim must be given at least 24 hours after chemotherapy and not within 14 days before the next chemotherapy dose, since giving it too close to chemotherapy can worsen its effects on rapidly dividing bone marrow cells. (1) (2)
• Certain antimetabolite chemotherapy agents: concomitant use may potentiate myelosuppression, per the UK source reviewed. (2)

Pregnancy, breastfeeding, kidney/liver function, age

Monitoring

Before starting

• Assessment for sickle cell disorder
• Baseline spleen size assessment if clinically indicated
• Baseline kidney function where relevant

During treatment

• Monitoring for symptoms of splenic enlargement/rupture (upper left abdominal or shoulder pain).
• Monitoring for respiratory symptoms suggestive of ARDS (fever, cough, breathing difficulty).
• Monitoring for signs of allergic reaction, especially around the time of dosing.
• White blood cell count monitoring, since leukocytosis (very high white cell counts) has been observed.
• Monitoring for signs of capillary leak syndrome, kidney inflammation, or vasculitis if symptoms suggest them.

Storage

Store in the refrigerator (typically 2-8degC), protected from light, in the original carton; allow to reach room temperature before injection per your product's specific instructions; do not freeze, and discard if accidentally frozen. Follow your dispensed product's own storage leaflet exactly.

Frequently asked questions

References

1. NEULASTA (pegfilgrastim) injection, for subcutaneous use -- full prescribing informationDailyMed (U.S. National Library of Medicine) -- FDA-approved drug labeling · United States · accessed 2026-07-30 · source 1
2. Neulasta Pre-Filled Syringe -- Summary of Product Characteristics (SmPC)electronic medicines compendium (emc), United Kingdom -- Amgen Limited · United Kingdom · accessed 2026-07-30 · source 2
3. Neulasta (pegfilgrastim) -- EPAR, centrally authorised medicineEuropean Medicines Agency (EMA) -- European Public Assessment Report (EPAR) · European Union · accessed 2026-07-30 · source 3
4. NEULASTA (pegfilgrastim) Product Monograph (Amgen Canada); Fulphila (pegfilgrastim) Product Monograph (biosimilar, BGP Pharma ULC)Health Canada -- Product Monograph · Canada · accessed 2026-07-30 · source 4
5. NEULASTA (Amgen Australia, ARTG 82873) -- sponsor cancellation effective 28 June 2024; Ziextenzo, Pelgraz, and Filpegla -- TGA biosimilar assessmentsTherapeutic Goods Administration (TGA), Australia -- ARTG cancellation notice and AusPAR/AusPMD biosimilar assessments · Australia · accessed 2026-07-30 · source 5
6. Pelgraz and Ziextenzo (pegfilgrastim biosimilars) -- New Zealand Data SheetsMedsafe (New Zealand regulator) -- New Zealand Data Sheets · New Zealand · accessed 2026-07-30 · source 6

Brand names by country

Single-ingredient pegfilgrastim names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries