Generic Name: pegylated interferon alfa-2a

Pronunciation: peg-a-sis

Abbreviation: N/A

Other Market Name: N/A

Drug Class: Recombinant Human Interferon Alfa

Company: Genentech, a division of Roche

Approval Status: Approved

Generic Version Available: No

Experimental Code: N/A

Drug Indication

FDA-approved for the treatment of adults with evidence of hepatitis B viral replication and active liver inflammation or damage. (Pegasys is also approved to treat hepatitis C infection.)

General Info

  • Pegasys was approved by the U.S. Food and Drug Administration to treat chronic hepatitis B infection in 2005. Pegasys is an injectable medication and requires refrigeration.
  • In clinical studies, 41 to 48 percent of participants with compensated liver disease who had no prior treatment showed improved liver biopsy results after 48 weeks of therapy.


Adult Dose: 180 mcg injected once weekly

Pediatric Dose: Technically, Pegasys is not approved for pediatric use, but doctors may prescribe it at their own discretion, a practice known as off-label. The total daily dose is usually determined by body surface.

Dosing Info: Treatment length is indefinite and depends on clinical outcomes. Do not change your dose or stop taking Pegasys without talking to your medical provider.

Side Effects

  • Many side effects ranging from mild to severe in intensity. The most common side effects are fatigue, weakness, fever, muscle aches and headache. Other side effects are cough, runny nose, sore throat, depression, irritability, moodiness, anxiety, dizziness, dry mouth/skin/eyes, flulike symptoms (chills, fever, joint and muscle aches), gastrointestinal disorders (abdominal pain, decreased appetite, diarrhea, nausea), hair loss, injection site reaction, insomnia, neutropenia (low white cells), pain (back, joint, muscle) and thrombocytopenia (low platelets).
  • Pegasys may cause or aggravate life-threatening neuropsychiatric, cardiovascular, autoimmune or infectious disorders. It may also cause eye problems, stroke, pulmonary problems, colitis, pancreatitis and serious skin reactions. Pegasys may cause bone marrow suppression, endocrine disorders and worsening of liver disease.

Drug Interactions

  • For a review of drug interactions, including prescription and over-the-counter medications and supplements that should not be taken with Pegasys or may require dose adjustments, consult the Pegasys package insert.

Other Info

  • There are no adequate, well-controlled studies in pregnant women who have taken Pegasys. Pegasys should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
  • The safety of breast feeding while taking Pegasys has not been established, and it is recommended that Pegasys be discontinued if breast-feeding.

For More Info:

Co-Pay Program Info:

Patient Assistance Program Info:

Last Reviewed: December 22, 2021