Yes, Pegasys Is a Weekly Subcutaneous Injection
Pegasys (peginterferon alfa-2a) is administered as a single subcutaneous injection once a week. The standard adult dose for chronic hepatitis C is 180 mcg, given under the skin in the abdomen or thigh, typically for 48 weeks depending on genotype and treatment regimen.[1][2]
How Is Pegasys Dosed for Hepatitis B?
For chronic hepatitis B in adults, the dose is also 180 mcg subcutaneously once weekly, usually for 48 weeks. In children, dosing is weight-based (e.g., 180 mcg/1.73 m² of body surface area) but follows the same weekly schedule.[1][2]
What If a Dose Is Missed?
Administer the missed dose as soon as possible if it's within 2-3 days, then resume the weekly schedule. Skipping more than one dose may reduce effectiveness; consult a doctor rather than doubling up.[2]
Why Weekly Instead of Daily Like Other Interferons?
Peginterferon alfa-2a has a polyethylene glycol (PEG) molecule attached, extending its half-life to about 80 hours. This allows sustained antiviral activity with once-weekly dosing, unlike unmodified interferons requiring daily shots.[1][3]
Common Side Effects Patients Report
Flu-like symptoms (fever, fatigue, chills), injection-site reactions, depression, and blood count changes occur frequently. Weekly dosing helps tolerability compared to daily options, but monitoring is required.[1][2]
Alternatives to Pegasys
Pegasys is largely replaced by direct-acting antivirals (e.g., sofosbuvir-based regimens) for hepatitis C, which are oral and shorter-course (8-12 weeks). For hepatitis B, tenofovir or entecavir are daily pills with fewer side effects.[3]
Sources
[1]: Pegasys Prescribing Information (FDA)
[2]: Drugs.com - Pegasys Dosing
[3]: Medscape - Peginterferon Alfa-2a Overview