How it is administered

Filgrastim is administered 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 and 480 mcg. The medication can be given by a healthcare provider or, after proper training, by patients or caregivers at home. The injection sites include the outer area of the upper arms, abdomen, thighs, or upper outer areas of the buttocks. The dose and duration depend on the specific condition being treated and patient response. For some uses, such as after chemotherapy, it is started at least 24 hours after the last chemotherapy dose.

How it works

Filgrastim is a man-made form of a protein called granulocyte colony-stimulating factor (G-CSF), which the body naturally produces. G-CSF stimulates the bone marrow to make more neutrophils, a type of white blood cell that helps the body fight infections. In people with blood cancers or those receiving treatments that lower white blood cell counts, filgrastim helps increase neutrophil production, reducing the risk and duration of infections.

Filgrastim works by binding to specific receptors on blood-forming cells in the bone marrow, encouraging them to grow, mature, and be released into the bloodstream. This action is especially important for patients undergoing chemotherapy or bone marrow transplantation, as these treatments can severely reduce neutrophil counts, making infections more likely and potentially dangerous. By boosting neutrophil levels, filgrastim helps protect against infections and supports recovery after intensive cancer treatments.

Who Should take it

Filgrastim is used to reduce the risk and duration of infections in people with non-myeloid blood cancers (such as lymphoma or leukemia) who are receiving chemotherapy that lowers white blood cell counts. It is also used to speed up recovery of white blood cells after bone marrow or stem cell transplantation, and to help collect stem cells for transplantation. Additionally, it is prescribed for people with certain chronic low white blood cell conditions (severe chronic neutropenia) and for those exposed to high doses of radiation.

In the context of blood cancers like myelofibrosis, filgrastim may be used if treatment or the disease itself leads to very low neutrophil counts, increasing infection risk. It is important to follow your doctor’s instructions about when and how to use filgrastim, as timing and dosing are tailored to your specific situation.

Who should not take it

Filgrastim should not be used by people who have had serious allergic reactions to filgrastim, pegfilgrastim, or similar medications. Signs of a serious allergic reaction include rash, swelling, difficulty breathing, or low blood pressure. If you have a history of these reactions, you should not take filgrastim.

Caution is also needed in people with sickle cell disease, as filgrastim can trigger sickle cell crises, which can be life-threatening. Patients with certain kidney problems, glomerulonephritis, or those who have experienced a splenic rupture should discuss risks with their doctor. Filgrastim is not recommended for use at the same time as chemotherapy or radiation therapy, and should not be given within 24 hours before or after chemotherapy.

Commonly used with

Filgrastim is often used alongside chemotherapy medications in patients with blood cancers to help prevent infections. It may also be used with other supportive care drugs, such as antibiotics, antifungals, and medications to manage side effects of cancer treatment. In stem cell or bone marrow transplantation, filgrastim is used with conditioning regimens and sometimes with other growth factors to support blood cell recovery.

Commonly tested with

Filgrastim has been tested in combination with various chemotherapy regimens for blood cancers, such as those used for lymphoma, leukemia, and multiple myeloma. It is also tested with different stem cell mobilization protocols for autologous transplantation. In clinical trials, filgrastim is often compared to placebo or to other growth factors to assess its effectiveness in reducing infection rates and improving recovery after chemotherapy or transplantation.