Classification: Colony Stimulating Factor
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 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 or treat neutropenia related to cancer therapy.
Filgrastim is most often given as a subcutaneous injection (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. Filgrastim should be refrigerated. 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 chemotherapy.
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:
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 take.
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.
Even though you are receiving filgrastim, you may still experience neutropenia, or a low white blood cell count (WBC). WBCs are important for fighting infection. While receiving treatment, your WBC count can drop, putting you at a higher risk of getting an infection. You should let your doctor or nurse know right away if you have a fever (temperature greater than 100.4 F), sore throat or cold, shortness of breath, cough, burning with urination, or a sore that doesn't heal.
Tips to preventing infection:
For more suggestions, read the Neutropenia Tip Sheet.
The following less common side effects was also reported in clinical trials: elevation of liver enzymes (found by a blood test) that resolves when the drug is stopped, enlarged spleen, and rupture of the spleen, which can present as severe pain in the upper left side of the abdomen or the left shoulder.
Call your doctor right away if you experience this pain while on filgrastim.