What injection is used to treat low White Blood Cell (WBC) count?

Treatment of Low White Blood Cell Count

For low white blood cell (WBC) counts, filgrastim (G-CSF) or pegfilgrastim are the standard injectable treatments, administered subcutaneously at 5-10 mcg/kg/day for filgrastim or 6 mg once per cycle for pegfilgrastim. 1

Specific Dosing by Clinical Context

Cancer Patients Receiving Chemotherapy

• Filgrastim: Start at 5 mcg/kg/day subcutaneously, administered as either daily injections or short IV infusion (15-30 minutes) 1
• Pegfilgrastim: 6 mg administered once, 1-3 days after chemotherapy completion 2
• Continue filgrastim until absolute neutrophil count recovery, typically for at least 4 days 1
• Do not administer doses less than 0.3 mL (180 mcg) due to dosing error risk 1

Acute Myeloid Leukemia (AML) Patients

• Administer G-CSF at 5 mcg/kg subcutaneously starting 7 days after chemotherapy completion until WBC count >500/μL 3
• In FLAG-IDA salvage regimen: G-CSF 5 mg/kg subcutaneously on days 1-5, with additional G-CSF 7 days post-chemotherapy until WBC >500/μL 3
• Critical caveat: Growth factors should NOT be used during induction therapy for acute promyelocytic leukemia (APL) 3

Severe Chronic Neutropenia

• Congenital neutropenia: 6 mcg/kg subcutaneously twice daily 1
• Cyclic or idiopathic neutropenia: 5 mcg/kg subcutaneously once daily 1

Bone Marrow Transplant Recipients

• 10 mcg/kg/day as IV infusion (no longer than 24 hours) 1

Administration Technique

Subcutaneous injection is the preferred route 4

• Rotate injection sites with multiple doses to prevent local tissue irritation 4
• IV administration is technically possible but not standard practice 4

Monitoring and Dose Adjustments

When to Initiate Treatment

• Start when WBC count drops below 3,000/mm³ with decline from baseline 5
• In chemotherapy patients, typical initiation occurs at WBC around 918 ± 452/μL 6
• Expected response: WBC increases to 13,800-15,500/μL within 3.7-4.6 days 6, 7

Dose Modifications for Specific Populations

Older patients (>60-65 years): Consider dose reductions in salvage regimens 3

• Fludarabine: 20 mg/m² (vs 30 mg/m²)
• Cytarabine: 500-1000 mg/m² (vs 1500-2000 mg/m²)
• Idarubicin: 8 mg/m² (vs 10 mg/m²)

Renal impairment: No specific G-CSF dose adjustment required, but monitor closely 5, 7

Critical Safety Considerations

Contraindications

• Absolute: History of serious allergic reactions to G-CSF products 1

Serious Warnings

• Splenic rupture: Evaluate any left upper abdominal or shoulder pain immediately 1
• ARDS: Discontinue if fever with lung infiltrates or respiratory distress develops 1
• Sickle cell crisis: Discontinue immediately if occurs 1
• Leukocytosis: Expected effect with WBC potentially exceeding 15,000/μL; this is therapeutic, not pathologic 2, 8

Common Adverse Effects

• Bone pain (most common, manageable) 1, 6
• Fever, rash, headache 1
• Urticaria (rare) 6

Special Clinical Scenarios

Transplant Recipients with Leukopenia

• G-CSF is safe and effective in solid organ transplant recipients 5, 7
• Does NOT precipitate or aggravate allograft rejection 7
• Particularly useful when leukopenia is secondary to ganciclovir/CMV, allowing continuation of optimal antiviral therapy in 81.6% of cases 5
• Average treatment duration: 10 days at 3.9 mcg/kg/day 5

Timing Relative to Chemotherapy

• Never give G-CSF within 24 hours before or during chemotherapy 1
• Start 24-72 hours after chemotherapy completion 1
• For pegfilgrastim specifically: administer 1-3 days post-chemotherapy 2

Laboratory Monitoring Considerations

• G-CSF administration causes marked WBC fluctuations (5-11 times baseline) and increases immature leukocytes up to 133-fold 8
• Inform laboratory staff of G-CSF use to avoid misinterpretation of abnormal morphology 8
• Withhold G-CSF for minimum 7 days before bone marrow assessment to avoid confounding interpretation 3