Skip to Content

Peginterferon alfa-2a

Generic Name: peginterferon alfa-2a (peg in ter FEER on AL fa 2 a)
Brand Name: Pegasys, Pegasys ProClick Autoinjector, Pegasys Prefilled Syringe

Medically reviewed by on Nov 28, 2018 – Written by Cerner Multum

What is peginterferon alfa-2a?

Peginterferon alfa-2a is used to treat chronic hepatitis B or C. peginterferon alfa-2a is also used to treat chronic hepatitis B when the virus begins to damage the liver.

Peginterferon alfa-2a is used to treat hepatitis B in adults and children who are at least 3 years old. Peginterferon alfa-2a is used to treat hepatitis C in adults and children who are at least 5 years old.

Peginterferon alfa-2a is often used in combination with another medicine called ribavirin, or with other medicines to treat hepatitis C.

Peginterferon alfa-2a may also be used for purposes not listed in this medication guide.

Important Information

You should not use this medicine if you have liver failure or autoimmune hepatitis, or if you are allergic to any type of interferon alfa.

Do not use peginterferon alfa-2a together with ribavirin if you are pregnant, or if you are a man and your sexual partner is pregnant. Prevent pregnancy while using this medicine, and for at least 6 months after you stop using it.

Peginterferon alfa-2a may cause serious or fatal side effects, and can worsen a medical condition you already have. Call your doctor if you have symptoms such as mood or behavior changes, chest pain, fast heartbeats, trouble breathing, numbness or weakness, loss of coordination, fever, chills, a cough with mucus, burning when you urinate, or bloody diarrhea.

Before taking this medicine

Peginterferon alfa-2a is often used together with other medicines. To make sure these medicines are safe for you, tell your doctor about all your medical conditions, and if you are pregnant or breast-feeding.

You should not use peginterferon alfa-2a if:

  • you are allergic to any type of interferon alfa; or

  • you have autoimmune hepatitis, or liver problems from causes other than hepatitis C.

Peginterferon alfa-2a may contain an ingredient that can cause serious side effects or death in very young or premature babies. Do not give peginterferon alfa-2a to a child without medical advice.

Tell your doctor if you have ever had:

Both men and women using peginterferon alfa-2a with ribavirin should use effective birth control to prevent pregnancy. Ribavirin is known to cause birth defects or death in an unborn baby if the mother or father is using this medicine.

If you are a woman, do not use peginterferon alfa-2a and ribavirin if you are pregnant. You may need to have a negative pregnancy test before taking these two medicines together and every month during your treatment.

Use at least 2 effective forms of birth control while either sexual partner is using peginterferon alfa-2a with ribavirin. Keep using 2 forms of birth control for at least 6 months after treatment ends.

Tell your doctor right away if a pregnancy occurs while either the mother or the father is using peginterferon alfa-2a with ribavirin.

You should not breast-feed while using peginterferon alfa-2a. Women with HIV or AIDS should not breast feed a baby. Even if your baby is born without HIV, the virus may be passed to the baby in your breast milk.

How should I use peginterferon alfa-2a?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Your dose needs may change if you switch to a different brand, strength, or form of this medicine. Avoid medication errors by using only the form and strength your doctor prescribes.

Peginterferon alfa-2a is injected under the skin, usually once per week. A healthcare provider may teach you how to properly use the medication by yourself.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you don't understand all instructions.

Peginterferon alfa-2a doses are based on body surface area (height and weight) in children. Your dose needs may change if the child is still growing.

Prepare an injection only when you are ready to give it. Do not use if the medicine looks cloudy, has changed colors, or has particles in it. Call your pharmacist for new medicine.

You will need frequent medical tests. Your blood pressure, vision, and lung function may also need to be checked.

Store in the refrigerator, protected from light. Do not shake or freeze this medicine.

Each single-use vial (bottle), prefilled syringe, or auto-injector device is for one use only. Throw it away after one use, even if there is still medicine left inside.

Use a needle and syringe only once and then place them in a puncture-proof "sharps" container. Follow state or local laws about how to dispose of this container. Keep it out of the reach of children and pets.

What happens if I miss a dose?

Use the medicine as soon as you remember, and then go back to your regular injection schedule. Do not use two doses at one time.

If you are more than 2 days late in using your injection, call your doctor for instructions.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using peginterferon alfa-2a?

Avoid drinking alcohol. It may increase your risk of liver damage.

Using peginterferon alfa-2a will not prevent your disease from spreading. Follow your doctor's instructions about how to prevent passing the disease to another person.

Peginterferon alfa-2a side effects

Get emergency medical help if you have signs of an allergic reaction: hives, or a rash that spreads and causes blistering and peeling; chest pain, anxiety, difficult breathing; swelling of your face, lips, tongue, or throat.

Peginterferon alfa-2a can cause life-threatening infections, autoimmune disorders, serious mood or behavior problems, or a stroke.

Stop using this medicine and call your doctor at once if you have unusual changes in mood or behavior, such as: depression, irritability, aggression, hallucinations, thoughts about hurting yourself, or falling back into a previous pattern of drug addiction. Once you have had this type of reaction to peginterferon alfa-2a, you may not be able to use it again.

Call your doctor at once if you have:

  • worsening liver symptoms--swelling around your midsection, nausea, diarrhea, loss of appetite, confusion, drowsiness, yellowing of the skin or eyes, loss of consciousness;

  • sudden numbness or weakness, slurred speech, problems with balance;

  • vision changes;

  • severe stomach pain with bloody diarrhea;

  • cough with yellow or pink mucus, trouble breathing;

  • pain or burning when you urinate;

  • numbness, tingling, or burning in your arms or legs;

  • low blood cell counts--fever, chills, tiredness, mouth sores, easy bruising, unusual bleeding, pale skin;

  • high or low blood sugar--headache, hunger, sweating, thirst, increased urination, dizziness, weakness, fruity breath odor, and feeling anxious or shaky;

  • new or worsened autoimmune disorders--skin problems, joint pain or swelling, cold feeling or pale appearance in your fingers or toes;

  • pancreas problems--severe pain in your upper stomach spreading to your back, vomiting;

  • thyroid problems--weight changes, skin changes, trouble concentrating, feeling hot or cold all the time; or

  • heart problems--chest pain or pressure, fast heartbeats, sweating, feeling light-headed.

Peginterferon alfa-2a can affect growth in children. Tell your doctor if your child is not growing at a normal rate while using this medicine.

Common side effects may include:

  • fever, chills;

  • muscle or joint pain;

  • headache; or

  • feeling weak or tired.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect peginterferon alfa-2a?

Tell your doctor about all your other medicines, especially:

This list is not complete. Other drugs may affect peginterferon alfa-2a, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.