filgrastim (granulocyte colony-stimulating factor, G-CSF)
Neupogen

Available forms
Available by prescription only
Injection: 300 mcg/ml in 1-ml and 1.6-ml single-dose vials

Indications and dosages
 To decrease occurrence of infection after chemotherapy for nonmyeloid malignancies, chronic severe neutropenia, and after bone marrow transplantation in cancer patients; to treat agranulocytosis, pancytopenia with colchicine overdose, acute leukemia myelodysplastic syndrome, and hematologic toxicity with zidovudine antiviral therapy. Adults: Initially, 5 mcg/kg S.C. or I.V. as a single daily dose. May increase dose incrementally by 5 mcg/kg for each course of chemotherapy according to duration and severity of absolute neutrophil count (ANC) nadir.
 Don’t administer earlier than 24 hours after or within 24 hours before chemotherapy.
 Give filgrastim daily for up to 2 weeks until ANC nadir reaches 10,000/mm³ after the anticipated chemoinduced ANC nadir. Duration of treatment depends on the myelosuppressive potential of the chemotherapy used. Discontinue if ANC nadir surpasses 10,000/mm³.
 AIDS. ◇ Adults: 0.3 to 3.6 mcg/kg S.C. or I.V. daily.
 Aplastic anemia. ◇ Adults: 800 to 1,200 mcg/m² S.C. or I.V. daily.
 Hairy cell leukemia, myelodysplasia. ◇ Adults: 15 to 500 mcg/m² S.C. or I.V. daily.

Pharmacodynamics
Immunostimulant action: Filgrastim is a naturally occurring cytokine glycoprotein that stimulates proliferation, differentiation, and functional activity of neutrophils, causing a rapid increase in WBC counts within 2 to 3 days in patients with normal bone marrow function or 7 to 14 days in patients with bone marrow suppression. Blood counts return to pretreatment levels, usually within 1 week after therapy ends.

Pharmacokinetics
Absorption: After S.C. bolus dose, blood levels suggest rapid absorption.
Distribution: Unknown.
Metabolism: Unknown.
Excretion: Elimination half-life is about 3 1/2 hours.

Contraindications and precautions
Contraindicated in patients hypersensitive to proteins derived from Escherichia coli or to drug or its components.

Interactions
Drug-drug. Chemotherapy drugs: May cause rapidly dividing myeloid cells to be sensitive to cytotoxic drugs. Don’t give filgrastim within 24 hours before or after a chemotherapy drug.
Lithium: May potentiate myeloproliferative effects of filgrastim. Use cautiously in patients taking lithium.

Adverse reactions
CNS: headache, weakness, fatigue, fever.
CV: MI, arrhythmias, chest pain, transient hypotension.
GI: nausea, vomiting, diarrhea, mucositis, stomatitis, constipation.
Hematologic: thrombocytopenia, leukocytosis.
Musculoskeletal: skeletal pain.
Respiratory: dyspnea, cough.
Skin: alopecia, rash, cutaneous vasculitis.
Other: hypersensitivity reactions.

Effects on lab test results
• May increase creatinine, uric acid, alkaline phosphatase, and LDH levels.
• May increase WBC count. May decrease platelet and neutrophil counts.

Overdose and treatment
Maximum tolerated dose hasn’t been determined. Overdose hasn’t been reported.

Special considerations
• Drug may interfere with antigen skin-testing procedures. Discontinue drug 24 to 48 hours before test.
• Store drug in refrigerator but don’t freeze it.
• Filgrastim isn’t compatible with normal saline solution.
• Obtain CBC and platelet counts before and twice weekly during therapy.
• Adult respiratory distress syndrome may occur in septic patients because of the influx of neutrophils at the site of inflammation.
• MI and arrhythmias have occurred; if patient has a cardiac condition, watch closely.
• Bone pain is the most frequent adverse reaction and if mild to moderate, may be controlled with nonnarcotic analgesics or if severe, may require narcotic analgesics.
Breast-feeding patients
• It isn’t known whether drug appears in breast milk. Consider the potential benefits and risks of using drug.
Pediatric patients
• Efficacy hasn’t been established, but there’s no evidence of greater toxicity in children than in adults.
Geriatric patients
• No age-related problems have been reported.

Patient education
• Review package insert information with patient. Thorough instruction is essential if home use is prescribed.
• Explain the importance of having blood tested regularly and keeping all scheduled appointments for follow-up care.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use