Recommended Dosage of Inpefa (Interferon Alfa-2b)
The recommended dose of Inpefa (interferon alfa-2b) is 3 million units (MU) administered subcutaneously three times per week for chronic hepatitis C treatment. 1
Dosing Guidelines Based on Treatment Context
Standard Monotherapy Dosing
- For interferon alfa-2b monotherapy: 3 MU three times weekly by subcutaneous injection 1
- Treatment duration: 12 months unless there is evidence of failure to respond 1
Weight-Based Dosing for Combination Therapy
When used in combination with ribavirin:
- Standard dose remains 3 MU three times weekly 1
- Ribavirin dosing should be weight-adjusted:
- 1,000 mg/day for patients ≤75 kg
- 1,200 mg/day for patients >75 kg 1
Special Populations
Pediatric Dosing
- For patients with body surface area >0.5 m²: 50 mcg/m² three times weekly
- For patients with body surface area ≤0.5 m²: 1.5 mcg/kg/dose three times weekly 2
Patients with Renal Impairment
- Normal kidney function: Standard dosing
- Severe kidney disease (GFR 15-59 mL/min): Reduced dose of 1 μg/kg of peginterferon alfa-2b with careful monitoring
- Dialysis patients: Consider dose reduction to avoid toxicity 1
Monitoring and Dose Adjustments
Required Monitoring
- Baseline hematology, blood chemistry, and urinalysis before starting treatment
- Repeat laboratory tests at 3-month intervals during treatment 2
- Monitor for virologic response at weeks 12 and 24 to guide treatment decisions 1
Dose Adjustments for Adverse Events
- If severe reactions occur, reduce dose by 50% or temporarily discontinue therapy until adverse reactions abate 2
- Treatment should be stopped in patients who fail to achieve an early virologic response (EVR) 1
Important Clinical Considerations
Efficacy Predictors
- Genotype is the strongest predictor of response to therapy
- Patients with non-genotype 1 (particularly genotypes 2 and 3) have higher sustained virologic response rates (76-82%) compared to genotype 1 (42-46%) 1
- CD4+ count >500 × 10⁶/L and baseline HCV viral load <10⁷ copies/mL are associated with better response in HIV co-infected patients 3
Treatment Duration
- For genotype 1: Standard duration is 48 weeks 1
- For genotypes 2 and 3: 24 weeks of treatment is generally sufficient 1
Common Pitfalls to Avoid
- Failing to screen patients for contraindications before initiating therapy
- Not adjusting dose in patients with severe adverse reactions
- Continuing treatment in non-responders (those without EVR)
- Not considering weight-based dosing when using combination therapy
Interferon alfa-2b is contraindicated in patients with decompensated liver disease, significant cytopenias, severe renal or cardiac disorders, and autoimmune disease 1. Always assess the risk-benefit ratio before initiating treatment, particularly in patients with advanced liver disease.