Benefits of Neulasta in Chemotherapy and Radiation

This drug is used to prevent infection during cancer treatment

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Neulasta (pegfilgrastim) is a drug used to reduce the risk of infection in people undergoing treatment for cancer. It stimulates the production of white blood cells known as neutrophils, which are the body's first-line defense against disease-causing microorganisms. Neulasta was approved for use by the Food and Drug Administration (FDA) for people at risk of infection while undergoing chemotherapy or radiation therapy.

Female doctor injecting vaccine to a patient.
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How It Works

One of the challenges of chemotherapy is that the conventional drugs work by targeting and killing fast-replicating cells. These not only include cancer cells but also hair follicles, cells of the digestive tract, and both red and white blood cells. This is why people undergoing chemotherapy will often experience things like hair loss, nausea, vomiting, fatigue, and anemia.

Neulasta works by stimulating the production of neutrophils, which account for up to 60% of your white blood cells and are central to your innate immune response.

Pegfilgrastim is the pegylated form of the drug filgrastim, a granulocyte colony-stimulating factor (G-CSF) analog. This means that a substance called polyethylene glycol (PEG) is attached to filgrastim so that it remains in the body longer before being broken down. In this time, bone marrow is stimulated to produce not only granulocytes such as neutrophils, but other white blood cells such as basophils and eosinophils.

When used on its own, filgrastim is marketed under the brand name Neupogen.

Who Can Take It

Neulasta is used to decrease the risk of neutropenia (a low neutrophil count) in adults or children undergoing myelosuppressive (bone-marrow-suppressing) chemotherapy. It is not given to everyone on chemotherapy but mainly those whose drug regimens are associated with a 17% or greater risk of febrile neutropenia (characterized by fever and other signs of infection).

A 2015 study from Japan reported Neulasta used in women with stage 4 breast cancer reduced the risk of febrile neutropenia during chemotherapy by 98% compared to a placebo.

Other factors may motivate the use of Neulasta, including:

  • Being over the age of 65
  • Having other medical conditions, such as diabetes or liver, heart, or lung disease
  • Having had previous chemotherapy or radiation
  • Having stage 4 metastatic cancer
  • Having a weakened immune system

Neulasta can also be used in people experiencing severe bone marrow suppression while undergoing radiation therapy (a condition referred to as acute radiation syndrome, or ARS).

Neulasta is not appropriate for people undergoing treatment for non-myeloid cancers. These are the types that do not involve the blood marrow. Examples include sarcoma, melanoma, lymphoma, lymphocytic leukemias, and multiple myeloma.


Neulasta is delivered by injection in a 0.6-milliliter (mL) pre-filled syringe. Each syringe contains 6 milligrams (mg) of Neulasta. The shot is given just beneath the skin in the upper arm, abdomen, thigh, or buttock.

The recommended adult dose can vary by the treatment type as follows:

  • For adults on chemotherapy, a single 6-mg injection would be given no later than 24 hours after the completion of the infusion. Neulasta is given once per chemotherapy cycle.
  • For adults undergoing radiation, two 6-mg injections, each given a week apart, would be started as soon as the first signs of ARS are recognized.

Children are given an adjusted dose based on their weight:

  • Less than 10 kilograms: 0.1 milligrams per kilogram of weight (mg/kg)
  • 10 to 20 kilograms: 1.5 mg
  • 21 to 30 kilograms: 2.5 mg
  • 31 to 44 kilograms: 4 mg
  • 45 kilograms or more: 6 mg

The dose may also vary based on your current health, medical conditions, and the type of cancer you have.

Side Effects

As with any drug, there are possible side effects with Neulasta use. Those who experience them will generally have low-grade symptoms that resolve on their own without treatment. The most common side effects experienced in up to 26% of people are:

  • Bone pain
  • Pain in the arms or legs
  • Injection site pain

These symptoms may be alleviated with over-the-counter pain relievers like Tylenol (acetaminophen), Advil (ibuprofen), or Aleve (naproxen). The antihistamine Claritin (loratadine) has also proven effective in reducing treatment-induced bone pain.

The on-body injector for Neulasta uses acrylic adhesive. For patients who have reactions to acrylic adhesives, this may result in a significant reaction. Serious allergic reactions, including anaphylaxis, are uncommon but can occur.

The vast majority of these occur after the initial exposure. Even if successfully treated with antihistamines and other drugs, treatment-induced allergies have been known to recur within days of stopping anti-allergy treatment.

Call 911 or seek emergency care if you develop rash or hives, high fever, dizziness, rapid or irregular heartbeats, shortness of breath, wheezing, or swelling of the face, tongue, or throat after receiving Neulasta.

If left untreated, anaphylaxis can lead to shock, coma, heart or respiratory failure, asphyxiation, and death.


It is not known if Neulasta can cause drug interactions. To date, none have been formally identified. With that being said, Neulasta should not be used with any other filgrastim-containing drugs due to the additive effect. These include:

  • Neupogen
  • Fulphila (pegfilgrastim-jmdb)
  • Granix (tbo-filgrastim)
  • Nivestym (filgrastim-aafi)
  • Udenysa (pegfilgrastim-cbqv)
  • Zarxio (filgrastim-sndz)


The only absolute contraindication to Neulasta use is a prior history of allergy to G-CSF analogs like Neulasta and Neupogen.

Filgrastim is derived from the fermentation of the bacterium E. coli. As such, you may also need any avoid Neulasta if you are allergic to E. coli-derived asparaginase used to treat leukemia.

Although Neulasta is not contraindicated in pregnancy, it should be used with extreme caution and only if the benefits of treatment outweigh the possible risks. Animal studies have demonstrated potential harm to a fetus but no well-controlled studies are available to assess the risk in humans.

Of the animal studies conducted, fetal harm was reported at doses four to 10 times that given to humans (based on body surface area). Low birth weight was the most common complication. Skeletal or organ defects were not reported.

It is not known whether Neulasta is excreted in breast milk. Other G-CSF drugs are known to be poorly excreted and poorly absorbed when ingested. Speak with your oncologist if you are pregnant or planning to get pregnant to fully understand the risks and benefits of treatment.

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Additional Reading

By Pam Stephan
Pam Stephan is a breast cancer survivor.