A long-acting white-cell growth factor (G-CSF)
Pegfilgrastim
A long-acting injection that boosts white blood cells after chemotherapy to lower the risk of infection.
What is Pegfilgrastim?
Pegfilgrastim is a long-acting white-cell growth factor (G-CSF) given as a single injection once per chemotherapy cycle to help the body make more neutrophils, a type of white blood cell, and so reduce the risk of serious infection when counts are low. The most common side effect is bone pain. Rarely, it can cause the spleen to enlarge or, very rarely, rupture, and it can rarely cause lung injury, so certain symptoms must be reported. It is given under the skin.
Education and reference only. This is a plain-language guide to Pegfilgrastim — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Pegfilgrastim is a man-made copy of a natural growth factor called G-CSF, which tells the bone marrow to make more neutrophils, a type of white blood cell that fights infection. It is used after chemotherapy, which often lowers these cells and leaves people prone to serious infection. Being long-acting, it is given as just one injection per chemotherapy cycle, rather than daily, to help white-cell numbers recover. It is given as an injection under the skin and is part of specialist cancer care.
How it works
Chemotherapy damages fast-growing cells, including those in the bone marrow that produce neutrophils, so neutrophil numbers can fall and the risk of infection rises. Pegfilgrastim stimulates the bone marrow to produce more neutrophils and release them into the blood, helping counts recover faster and reducing the chance of a serious infection while counts are low. The 'peg' part makes it stay in the body longer, so a single injection works across the gap until the next chemotherapy cycle, instead of needing daily injections.
Company & origin
Originated / developed by: Various manufacturers.
A long-acting growth factor used in the UK after chemotherapy to boost white blood cells and reduce infection risk.
Practical use
How to take Pegfilgrastim
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as a single injection under the skin once per chemotherapy cycle, usually a day or so after chemotherapy.
- If you inject it yourself or a carer does, follow the training you are given carefully.
- Expect bone pain a day or two afterwards; simple painkillers such as paracetamol usually help.
- Report pain in the upper-left tummy or the tip of the left shoulder urgently, as this can signal a spleen problem.
- Report new breathlessness, fever or feeling generally unwell, so the team can check you.
Weighing it up
Advantages & disadvantages of Pegfilgrastim
Advantages
- Reduces the risk of serious infection after chemotherapy by boosting white blood cells.
- Given as a single injection per cycle rather than daily injections.
- Can often be given at home by the patient or a carer after training.
Disadvantages
- Bone pain is common after the injection.
- Rarely can cause the spleen to enlarge or, very rarely, rupture.
- Can rarely cause lung injury, so some symptoms must be reported.
Practical use
Good to know
The most common thing to expect with pegfilgrastim is bone pain, often felt in the back, hips or long bones a day or two after the injection, as the marrow gears up to make cells; simple painkillers such as paracetamol usually help and it tends to settle. Although uncommon, there are two more serious things to be aware of: it can occasionally cause the spleen to enlarge, and very rarely to rupture, so any pain in the upper-left tummy or the tip of the left shoulder must be reported urgently; and it can rarely cause a lung problem, so new breathlessness or fever should be reported. It is given as a single injection after each chemotherapy cycle, sometimes by the patient or a carer after training. It is used as part of specialist cancer care, with blood counts checked.
Who should not take it / use with caution
- People who have had a serious allergic reaction to pegfilgrastim or similar G-CSF medicines should not use it.
- It is used with caution in people with sickle cell disease, as it can trigger a crisis.
- It is used with care in people with certain blood or bone-marrow conditions, under specialist guidance.
- It should only be used under a specialist cancer team.
Monitoring
- Checking blood counts to see how white-cell numbers recover.
- Watching for bone pain and managing it with painkillers.
- Watching for signs of spleen or lung problems, such as upper-left tummy pain or breathlessness.
Side effects
- Bone or muscle pain, often in the back, hips or limbs.
- Headache or a general feeling of being unwell.
- Rarely, enlargement of the spleen, with very rare rupture.
- Rarely but seriously, lung injury or a serious allergic reaction, which need urgent attention.
Key interactions
- Tell your team about all medicines you take, including other cancer treatments.
- Its timing around chemotherapy is planned by the team to avoid overlap with the treatment itself.
- Some medicines that affect the bone marrow may interact, so the team reviews your treatment.
Available as: A solution for injection under the skin, often in a pre-filled device.
Answers
Pegfilgrastim: frequently asked questions
What is pegfilgrastim used for?
It is given after chemotherapy to boost white blood cells called neutrophils, lowering the risk of serious infection while counts are low.
How often is it given?
Because it is long-acting, it is given as a single injection once per chemotherapy cycle, rather than as daily injections.
Why do my bones ache after it?
Bone pain is the most common side effect, caused by the marrow making new cells; it usually settles, and simple painkillers such as paracetamol often help.
What is the spleen warning about?
Rarely it can make the spleen enlarge or, very rarely, rupture, so report pain in the upper-left tummy or the tip of the left shoulder urgently.
Can I inject it myself?
In some cases yes, the patient or a carer can give it under the skin after being trained by the specialist team.
The wider class
About Long-acting white-cell growth factor (G-CSF)
Pegfilgrastim belongs to the long-acting white-cell growth factor (g-csf) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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