How it is administered

Filgrastim is given as an injection, either under the skin (subcutaneous) or into a vein (intravenous). It is available in single-dose vials and prefilled syringes, with common strengths being 300 mcg or 480 mcg per dose. The injection is typically administered once daily, and the exact dose and duration depend on your weight and the specific reason for use. Your healthcare provider will determine the best way for you to receive this medication, and in some cases, you or a caregiver may be trained to give the injections at home.

How it works

Filgrastim is a man-made form of a naturally occurring protein called granulocyte colony-stimulating factor (G-CSF). This protein is produced in your body and helps stimulate the bone marrow to make more white blood cells, specifically neutrophils. Neutrophils are a type of white blood cell that are essential for fighting infections.

When you receive chemotherapy for large B cell lymphoma or other blood cancers, your bone marrow can be suppressed, leading to a low white blood cell count (neutropenia). Filgrastim helps your body recover faster by boosting the production of neutrophils, reducing the risk and duration of infections. It acts by binding to specific receptors on blood-forming cells in the bone marrow, encouraging them to multiply and mature into functional neutrophils. This effect helps protect you from serious infections during periods when your immune system is weakened by cancer treatment.

Who Should take it

Filgrastim is recommended for patients with non-myeloid cancers, such as large B cell lymphoma, who are receiving chemotherapy that can significantly lower white blood cell counts and increase the risk of infection. It is also used in patients undergoing bone marrow transplantation, those collecting stem cells for transplant, and people with certain types of chronic neutropenia (low white blood cell count not related to cancer treatment).

For large B cell lymphoma, filgrastim is often used to decrease the incidence of infection, as shown by fever and low neutrophil counts, after chemotherapy. It can also be used to speed up recovery of white blood cells after stem cell or bone marrow transplantation, and to mobilize stem cells into the bloodstream for collection before a transplant.

Who should not take it

You should not take filgrastim if you have had a serious allergic reaction to filgrastim, pegfilgrastim, or any other granulocyte colony-stimulating factor products. Signs of a serious allergic reaction include rash, swelling, difficulty breathing, or low blood pressure after receiving the medication.

Caution is needed in people with sickle cell disease, as filgrastim can trigger sickle cell crises. It is also not recommended for use at the same time as chemotherapy or radiation therapy, as this can increase the risk of side effects. If you have a history of certain blood disorders (like myelodysplastic syndrome or chronic myeloid leukemia), filgrastim should be used only under close medical supervision.

Commonly used with

Filgrastim is commonly used alongside chemotherapy regimens for large B cell lymphoma and other blood cancers. It may also be used with antibiotics if an infection develops, and with other supportive care medications such as anti-nausea drugs or pain relievers. In the setting of stem cell transplantation, it may be used with medications to prepare the bone marrow or to prevent rejection.

Commonly tested with

Filgrastim is often studied and used in combination with various chemotherapy drugs (such as cyclophosphamide, doxorubicin, etoposide, and rituximab) in patients with large B cell lymphoma and other blood cancers. It has also been tested with other growth factors and supportive care agents in clinical trials to evaluate its effectiveness in reducing infection risk and improving recovery after intensive cancer treatments.