What is the recommended dosage of peginterferon (peginterferon alfa-2a) and pegfilgrastim for adult patients with conditions like hepatitis C or those undergoing chemotherapy?

Peginterferon Dosing for Hepatitis C

For peginterferon alfa-2a, administer 180 μg subcutaneously once weekly regardless of body weight; for peginterferon alfa-2b, administer 1.5 μg/kg subcutaneously once weekly. 1

Peginterferon Alfa-2a Dosing

• Standard dose: 180 μg subcutaneously once weekly, fixed dose regardless of patient body weight 1
• This dosing applies to all HCV genotypes when used in combination therapy 1
• The FDA-approved formulation contains 180,135, or 90 μg per injection, with dose reductions available if needed 2

Peginterferon Alfa-2b Dosing

• Weight-based dosing: 1.5 μg/kg subcutaneously once weekly 1
• The formulation contains 50 μg per 0.5 mL 1
• This weight-based approach differs fundamentally from the fixed-dose peginterferon alfa-2a regimen 1

Ribavirin Combination Dosing

When peginterferon is combined with ribavirin (the standard approach for interferon-based regimens):

With Peginterferon Alfa-2a:

• 1,000 mg/day for patients ≤75 kg body weight 1
• 1,200 mg/day for patients >75 kg body weight 1
• Administered as 2 capsules (200 mg each) in the morning and 3 in the evening if <75 kg, or 3 capsules morning and 3 evening if ≥75 kg 1

With Peginterferon Alfa-2b:

• 800 mg/day for patients <65 kg 1
• 1,000 mg/day for patients 65-85 kg 1
• 1,200 mg/day for patients 85-105 kg 1
• 1,400 mg/day for patients >105 kg 1

Treatment Duration by Genotype

Genotype 1 and 4:

• Standard duration: 48 weeks of combination therapy 1
• May shorten to 24 weeks in genotype 4 patients who achieve rapid virologic response (RVR), regardless of baseline viral load 1
• In genotype 1 with RVR and low baseline viral load (<400,000 IU/mL) without negative predictors (advanced fibrosis, cirrhosis, obesity, insulin resistance), consider shortening to 24 weeks 1

Genotype 2 and 3:

• Standard duration: 24 weeks of combination therapy 1
• Peginterferon alfa-2a: 180 μg weekly 1
• Peginterferon alfa-2b: 1.5 μg/kg weekly 1
• Ribavirin: flat dose of 800 mg daily regardless of peginterferon type 1

Critical Context: Modern Treatment Has Evolved

Important caveat: While these peginterferon dosing guidelines remain accurate for the medication itself, direct-acting antiviral (DAA) regimens have replaced peginterferon as first-line therapy for hepatitis C. 3, 4, 5

• Modern first-line treatment is sofosbuvir/velpatasvir 400mg/100mg once daily for 12 weeks, achieving 98% SVR rates across all genotypes 3, 4, 5
• Alternative first-line: glecaprevir/pibrentasvir for 8-12 weeks depending on cirrhosis status 3, 4, 5
• Peginterferon-based regimens are now reserved for specific situations where DAAs are unavailable or contraindicated 1

Dose Modifications

• Dose reductions are recommended for certain laboratory abnormalities, adverse reactions, or renal impairment 2
• The 180 μg peginterferon alfa-2a formulation allows reduction to 135 μg or 90 μg if needed 2
• Treatment should be stopped in patients who fail to achieve early virologic response (EVR) at week 12 1

Administration Technique

• Both peginterferon formulations are administered by subcutaneous injection 1, 2
• Once-weekly dosing is enabled by the pegylation process, which increases half-life and reduces renal clearance 1
• The 40-kD polyethylene glycol moiety attached to interferon alfa-2a shields the molecule from enzymatic degradation 6, 7