Standard Dosing for Pegasys
Pegasys (peginterferon alfa-2a) dosing varies by condition. For chronic hepatitis C in adults, the dose is 180 mcg subcutaneously once weekly, typically for 48 weeks in combination with ribavirin.[1] In children (ages 5+), it's weight-based: 180 mcg per 1.73 m² of body surface area, capped at 180 mcg, once weekly.[1]
Dosing for Hepatitis B
Adults receive 180 mcg subcutaneously once weekly for 48 weeks. Pediatric dosing (ages 3+) is weight-based: under 20 kg use 5 mcg/kg; 20-25 kg use 10 mcg/kg; over 25 kg use fixed doses up to 180 mcg, all once weekly for 48 weeks.[1]
Adjustments for Kidney or Liver Issues
Reduce dose to 135 mcg weekly if creatinine clearance is 30-59 mL/min. No adjustment needed for mild liver impairment, but monitor closely and reduce if severe.[1] Discontinue if platelets drop below 50,000/mm³ or neutrophils below 1,000/mm³.[1]
How It's Administered
Given as a prefilled syringe injected under the skin in the abdomen or thigh. Rotate sites weekly. Store refrigerated; allow to warm to room temperature before use.[1]
Sources:
[1] Pegasys Prescribing Information (Genentech)