Pegfilgrastim

Class: Hematopoietic growth factor – PEGylated recombinant human G-CSF (granulocyte colony-stimulating factor).

Mechanism of Action:

• Stimulates proliferation, differentiation, and activation of neutrophil precursors in the bone marrow.
• PEGylation prolongs its half-life → allows once-per-cycle dosing instead of daily filgrastim.

Clinical Uses

• Primary prophylaxis of chemotherapy-induced neutropenia.
• Reduces febrile neutropenia risk in patients receiving myelosuppressive chemotherapy.
• Occasionally used in stem cell mobilization (off-label).

Dosing

• Fixed dose: 6 mg subcutaneously once per chemotherapy cycle, typically 24–72 hours after chemotherapy.
• Adjustments: Not usually weight-based due to PEGylation; contraindicated in hypersensitivity to filgrastim or PEG.

Toxicities

• Bone pain – most common, due to marrow expansion.
• Splenic enlargement / rupture – rare but serious.
• Leukocytosis – usually mild and transient.
• Injection site reactions – erythema, pain, swelling.
• Rare: acute respiratory distress, capillary leak syndrome.

Monitoring

• Baseline CBC before each cycle.
• Monitor for severe bone pain or abdominal pain (spleen-related).
• Not routinely monitored with WBC counts unless clinically indicated.

Summary

Pegfilgrastim is a long-acting G-CSF used to prevent chemotherapy-induced neutropenia. Its once-per-cycle dosing improves convenience over filgrastim. Bone pain is the most common adverse effect, while rare events like splenic rupture warrant immediate attention.