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Filgrastim (Neupogen®, G-CSF)

OncoLink Team
Last Modified: October 29, 2015

Pronounced: fil-GRA-stim
Classification: Colony Stimulating Factor

About Filgrastim

Filgrastim is a type of colony stimulating factor, which is a group of medications that stimulate the production and function of blood cells. Granulocyte colony-stimulating factor (G-CSF) is a protein naturally produced by the body to increase production of white blood cells. Filgrastim is a man-made version of G-CSF that stimulates white blood cell production, and in particular, neutrophil production. A neutrophil is a type of white blood cell that is responsible for fighting infection and is often decreased during cancer therapy. When the number of these cells drops below 1000/mm3, it is called neutropenia, which puts the patient at significant risk of infection. Filgrastim is used to prevent neutropenia related to cancer therapy. It may also be used to increase the number white blood cells prior to a stem cell collection for transplant.

How to Take Filgrastim

Filgrastim is most often given as a subcutaneous injection (SQ, given under the skin), but it can be given directly into a vein (intravenous, IV). It is given once a day, preferably at the same time of day, until the neutrophil count returns to normal. The actual dose is based on your body size and what you are taking it for and will be determined by your healthcare provider.

Storage and Handling

Filgrastim should be stored in the refrigerator and in the original carton to protect it from light. To lessen the sting of the injection, it should be taken out of the refrigerator 30 minutes ahead of time. Filgrastim should be started no sooner than 24 hours after completion of the chemotherapy dose.

Do not reuse single dose vials, syringes or needles. Do not throw the vials, syringes, or needles in the household trash. Dispose of all used needles and syringes in a puncture-proof disposable container with a lid. The FDA provides further information about the disposal of vials, syringes and needles.

Where do I get this medication?

Depending on your insurance coverage, filgrastim is available through specialty, retail, or mail order pharmacies. Your oncology team will work with your prescription drug plan to identify an in-network pharmacy for medication distribution. 

Alternatively, this medication may be given in the doctor’s office, clinic, or infusion suite. Where you receive it is often dependent on your insurance coverage.

Insurance Information

This medication may be covered under your prescription drug plan or your major medical insurance coverage. Patient assistance may be available to qualifying individuals without prescription drug coverage. Co-pay cards, which reduce the patient co-pay responsibility for eligible commercially (non-government sponsored) insured patients, are also available. Your care team can help you find these resources, if they are available.

Possible Side Effects of Filgrastim

There are a number of things you can do to manage the side effects of Filgrastim. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:

Bone Pain

Filgrastim stimulates the bone marrow to produce many white blood cells, which can lead to pain in the bones. This pain is often felt in the bones of the thighs, hips, and upper arms. Your healthcare team may not want you to take acetaminophen (Tylenol™) because it can "mask" a fever, so talk to them about which pain relievers you can safely take.

Irritation or Burning at the Injection Site

Some people experience redness, swelling, or itching at the site of injection. This is usually temporary. The injection is known to sting or burn if given when it is cold. Take the medication out of the refrigerator 30 minutes ahead of time to allow it to come up to room temperature before administration. Rotate the sites that the injection is given, inject slowly, and/or numb the area with ice prior to giving the injection.

Allergic Reactions

In some cases, patients can have an allergic reaction to this medication. Signs of a reaction can include: shortness of breath or difficulty breathing, wheezing, rash, flushing, swelling around the mouth or eyes, fast pulse, or sweating. If you notice any changes in how you feel after the injection, let your nurse know immediately.

Spleen Rupture

Filgrastim can cause your spleen to become enlarged and rupture. If you experience pain in the left upper stomach / abdominal area or left shoulder, contact your healthcare team or go to the emergency room immediately.

Acute Respiratory Distress Syndrome (ARDS)

This medication can cause a series lung program called acute respiratory distress syndrome.  If you experience shortness of breath, fever, breathing trouble or a fast rate of breathing, contact your healthcare team or go to the emergency room.

Decreased Platelet Count (Thrombocytopenia)

Platelets help your blood clot, so when the count is low you are at a higher risk of bleeding. Let your doctor or nurse know if you have any excess bruising or bleeding, including nose bleeds, bleeding gums or blood in your urine or stool. Your care team will monitor your platelet count.

Sickle Cell Crisis

In patients with sickle cell anemia, filgrastim can cause a sickle cell crisis.  Contact your healthcare team immediately if you have symptoms of a sickle cell crisis including pain and trouble breathing.

Capillary Leak Syndrome

Capillary leak syndrome is a potentially serious complication in which fluids from the veins and capillaries leak into the tissue outside the bloodstream. This results in low blood pressure and poor blood flow to the internal organs and can be life-threatening. You should get medical attention right away if you develop overall swelling/puffiness, swelling of the abdomen, decreased urination, trouble breathing, dizziness or feeling faint.

Other Side Effects

Let your care team know if you develop purple spots or redness on your skin as this can be a sign of an inflammation of your blood vessels (cutaneous vasculitis).

Some patients developed kidney problems on this medication, Let your care team know if you develop swelling in your face or ankles, blood in your urine, brown colored urine or a decrease in the amount of urine.



If you have questions or concerns about the medication that you have been prescribed, please contact your healthcare team. OncoLink is designed for educational purposes only and is not engaged in rendering medical advice or professional services. The information provided through OncoLink should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you have or suspect you may have a health problem, you should consult your health care provider.



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