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Peginterferon Alfa-2a  Audio icon

Other Names: PEG-interferon alfa-2a, Pegasys, pegIFN alfa-2a, pegylated-interferon alfa 2a

What is peginterferon alfa-2a?


Peginterferon alfa-2a is an antiviral prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of chronic hepatitis B virus (HBV) infection and chronic hepatitis C virus (HCV) infection. HBV infection and HCV infection are opportunistic infections. An opportunistic infection is an infection that occurs more frequently or is more severe in people with weakened immune systems—such as those infected with HIV—than in people with healthy immune systems.

The Guidelines for Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents, prepared by the U.S. Department of Health and Human Services (HHS) and the Centers for Disease Control and Prevention (CDC), provides recommendations on the use of peginterferon alfa-2a to treat HBV and HCV infections in people also infected with HIV. In addition to recommendations for the medicine's use in treating chronic HBV and HCV infections, the guidelines include recommendations on the “off-label” use of peginterferon alfa-2a to treat acute HCV infection in HIV-infected individuals. “Off-label” use refers to use of an FDA-approved medicine in a manner different from that described on the medicine label. Good medical practice and the best interests of a patient sometimes require that a medicine be used “off-label.”


What should I tell my health care provider before taking peginterferon alfa-2a?


Before taking peginterferon alfa-2a, tell your health care provider:

  • If you are allergic to peginterferon alfa-2a or any other medicines.
  • About any medical conditions you have or have had, for example, diabetes or liver problems.
  • About anything that could affect your ability to take medicines, such as difficulty swallowing or remembering to take pills.
  • If you are pregnant or plan to become pregnant. You may take peginterferon alfa-2a with another medication called ribavirin. Ribavirin may cause birth defects or death of an unborn child. Pregnant women and men whose partners are pregnant should not use ribavirin.
  • If you are breastfeeding or plan to breastfeed. Do not breastfeed if you are infected with HIV.
  • About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Ask your health care provider if there are interactions between peginterferon alfa-2a and the other medicines you take.

Ask your health care provider about possible side effects from peginterferon alfa-2a. Your health care provider will tell you what to do if you have side effects.


How should I take peginterferon alfa-2a?


Take peginterferon alfa-2a according to your health care provider’s instructions. Your health care provider will tell you how much peginterferon alfa-2a to take and when to take it. Before you start peginterferon alfa-2a and each time you get a refill, read any printed information that comes with your medicine.


How should peginterferon alfa-2a be stored?


  • Store peginterferon alfa-2a single use vials, prefilled syringes, and autoinjectors in the refrigerator, between 36°F and 46°F (2°C to 8°C). Do not leave peginterferon alfa-2a out of the refrigerator for more than 24 hours.
  • Do not freeze or shake peginterferon alfa-2a.
  • Protect peginterferon alfa-2a from light.
  • Vials, prefilled syringes, and autoinjectors are for single use only. Discard any unused portion remaining in the vial or prefilled syringe.
  • Safely throw away peginterferon alfa-2a that is no longer needed or expired (out of date).
  • Keep peginterferon alfa-2a and all medicines out of reach of children.


Where can I find more information about peginterferon alfa-2a?


More information about peginterferon alfa-2a is available:


Last Reviewed: October 4, 2012

Last Updated: October 4, 2012