What Is Filgrastim?

Filgrastim is supportive treatment used to prevent or treat neutropenic fever , an important and potentially life-threatening side effect of chemotherapy.

It is given as a subcutaneous injection under the skin. Filgrastim is the active ingredient in a prefilled syringe and is available under names including Zarzio, Tevagrastim, Fraven, and Leucostim.

Medicine Profile

Active Ingredient: Filgrastim
Class: Granulocyte colony-stimulating factor (G-CSF)
Brand Names: Zarzio, Tevagrastim, Fraven, Leucostim
Administration: Subcutaneous injection

Formulation and Dosage

Available Presentations: 300 mcg (30) / 480 mcg (48)
Standard Chemotherapy Dose: 5 mcg/kg / day
BMT / Transplant Dose: 10 mcg/kg / day
Storage: Refrigerate at 2°C - 8°C

Key Indications Urgent

Prevention and treatment of chemotherapy-related neutropenia
Managing neutropenic fever risk of 20% or higher
Stem cell mobilization and improved engraftment

How Does Filgrastim Work?

Filgrastim is designed to reduce infection risk after chemotherapy. It belongs to a group called granulocyte colony-stimulating factors (G-CSFs), also known as growth factors.
Filgrastim binds to stem cells in the bone marrow and accelerates production of white blood cells called neutrophils, an important part of the immune system.
Chemotherapy kills rapidly growing cells, such as cancer cells, but may also destroy healthy cells such as neutrophils.
This is called neutropenia and indicates weakened immunity.
Neutrophils are the first line of defense against infection. Normally, they cause inflammation at an infection site, including redness, swelling, pain, and itching.
After chemotherapy destroys neutrophils, however, infection signs may not appear in the same way. Fever may be the only sign of infection.

A Critical Medical Emergency A very low neutrophil count together with fever is called “neutropenic fever” and is a medical emergency. Fever after chemotherapy must be reported to a doctor immediately, or the patient should attend an emergency department.

Treatment Goals

Filgrastim prevents dangerously low neutrophil counts after certain chemotherapy regimens.
It particularly helps reduce risk with treatments likely to cause neutropenic fever, although it may not prevent it entirely.
When used for prevention, this is called “prophylaxis” or “prophylactic treatment.”
It may also be given preventively in some cases of low neutrophil counts caused by conditions other than chemotherapy.

Fever and Hospital Admission If neutropenic fever develops, the patient is hospitalized and filgrastim is also used to treat neutropenia. Intensive antibiotics and fluids are given in hospital.

Filgrastim is also used in patients undergoing stem cell transplantation, commonly called bone marrow transplantation.
It promotes production of extra stem cells needed for collection before transplantation.
Administering it at least 24 hours after some types of transplantation may help improve engraftment.

How Is Filgrastim Given?

Filgrastim is usually injected under the skin at home or in a clinic.
It is supplied in prefilled syringes containing 300 mcg (30) or 480 mcg (48).

Safe Storage and Preparation at Home

Store filgrastim in a refrigerator between 2° and 8° C.
Do not freeze, and protect it from direct light.
You may remove it from the refrigerator 30 minutes before injection to allow it to reach room temperature.
Do not leave filgrastim at room temperature for more than 24 hours.

Suitable injection sites:

The outer upper arms
The abdomen, up to 5 cm (2 inches) away from the navel
The upper and outer thighs
The upper outer buttocks

Timing Filgrastim is generally given approximately 24 hours after chemotherapy ends to help prevent neutropenic fever. Because it is short-acting, daily injections may be needed for the period specified by the doctor. If you miss a dose, ask your healthcare professional when to take it.

Who Receives Filgrastim?

It is generally given to patients with potentially curable cancers whose chemotherapy carries more than a 20% risk of neutropenic fever.
It may also be used with lower-risk chemotherapy in people with weakened immunity, poor organ function, or previous low neutrophil counts or neutropenic fever.
Filgrastim is generally repeated after each chemotherapy cycle.

Clinical Situation / Indication	Standard Starting Dose and Timing
Standard Protection / Prophylaxis After Chemotherapy	5 mcg/kg injected subcutaneously once daily, generally starting 24 hours after chemotherapy.
After Blood and Bone Marrow Transplantation (BMT)	10 mcg/kg injected subcutaneously once daily, generally starting at least 24 hours after stem cell infusion.
Mobilization Before Autologous Stem Cell Transplantation	Higher-dose regimens are started at least 4 days before the first planned stem cell collection.

Side Effects

Possible side effects include:

Bone pain, the most common side effect
Muscle pain
Fatigue and weakness
Injection-site redness, swelling, or pain
Headache
Nausea or vomiting
Low blood pressure (hypotension) or high blood pressure (hypertension)
Low platelets (thrombocytopenia), which may increase bleeding risk
Enlarged spleen (splenomegaly) and, rarely, splenic rupture

Rare but Serious Side Effects

Allergic reactions, including rash, breathlessness, and swelling of the face or lips
Severe breathing problems (acute respiratory distress syndrome, ARDS)
Glomerulonephritis (kidney inflammation)

Contact your healthcare professional immediately if you have severe bone pain, breathlessness, fever, or severe abdominal pain.

How Often Is Monitoring Needed?

Blood tests are generally performed on the day of chemotherapy.
If fever develops, the doctor may repeat tests to check whether the absolute neutrophil count (ANC) is low.
If ANC is low, blood cultures or other tests may assess for infection.
Blood counts may be checked daily until neutrophils reach a safe level.
Testing generally includes a complete blood count (CBC), but additional tests may be requested.

How Blood Results and Monitoring Affect Treatment

Depending on results, the doctor may recommend:

Continuing filgrastim as planned,
Reducing future treatment doses,
Delaying the next filgrastim dose until side effects resolve,
Switching to another treatment.

Laboratory Note: Temporary Increase in White Blood Cells After filgrastim, white blood cell (WBC) counts may temporarily exceed 100,000/mm³ in some patients. This generally causes no serious clinical problem and is associated only with bone pain. WBC levels return to normal shortly after treatment ends.

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What Is Filgrastim (Zarzio, Tevagrastim, Fraven, Leucostim)? Use and Side Effects