Peginterferon Alfa-2a (Injection)


Peginterferon Alfa-2a (peg-in-ter-FEER-on AL-fa-2a)

Treats hepatitis B and C. May be used alone or in combination with another medicine (such as ribavirin, Copegus®, Rebetol®).

Brand Name(s)

Pegasys, Pegasys Proclick

There may be other brand names for this medicine.

When This Medicine Should Not Be Used

You should not use this medicine if you have had an allergic reaction to peginterferon alfa-2a or other alpha interferons. You should not use this medicine if you have certain other liver problems that are getting worse (such as autoimmune hepatitis or cirrhosis). Do not use this medicine together with ribavirin if you are pregnant, if your female sexual partner is pregnant, or if you have a blood disorder (such as sickle-cell anemia or thalassemia major). You should not use this medicine if you are also taking didanosine (Videx®, Videx® EC). Do not give this medicine to a baby younger than 1 year.

How to Use This Medicine


  • Your doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot under your skin. This medicine is usually given in the abdomen or thighs.
  • A nurse or other trained health professional will give you this medicine.
  • You may be taught how to give your medicine at home. Make sure you understand all instructions before giving yourself an injection. Do not use more medicine or use it more often than your doctor tells you to.
  • This medicine should come with a Medication Guide. Read and follow these instructions carefully. Ask your doctor or pharmacist if you have any questions. Ask your pharmacist for the Medication Guide if you do not have one.
  • Use this medicine on the same day each week and at about the same time of the day.
  • Double-check that you are giving yourself the correct amount of medicine if you switch from using the vials to using the prefilled syringes or disposable autoinjectors,
  • You might not use all of the medicine in each vial (glass container), prefilled syringe, or disposable autoinjector. Use each vial, syringe, or autoinjector only 1 time. Do not save an open vial, syringe, or autoinjector. Do not use medicine that has changed color or has particles in it.
  • You will be shown the body areas where this shot can be given. Use a different body area each time you give yourself a shot. Keep track of where you give each shot to make sure you rotate body areas.
  • Use a new needle and syringe each time you inject your medicine.
  • Drink extra fluids while you are using this medicine to stay hydrated, especially during the first part of your treatment.
  • Use only the brand of this medicine that your doctor prescribed. Different brands may not work the same way.

If a dose is missed:

  • If you miss a dose or forget to use your medicine and you are 1 or 2 days late, use it as soon as you can. If it has been more than 2 days since you were supposed to use the medicine, call your doctor for instructions.
  • Do not use extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine

  • If you store this medicine at home, keep it in the refrigerator. Do not freeze. Do not leave this medicine out of the refrigerator for more than 24 hours. Protect it from light.
  • Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any leftover medicine, containers, and other supplies. You will also need to throw away old medicine after the expiration date has passed.
  • Keep all medicine away from children and never share your medicine with anyone.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you use medicine to treat HIV or AIDS such as abacavir, lamivudine, stavudine, zidovudine, Combivir®, Epivir®, Trizivir®, Zerit®, or Ziagen®. Tell your doctor if you also use azathioprine (Imuran®), methadone (Dolophine®), or theophylline (Slo-Bid®, Theo-Dur®).
  • Do not drink alcohol while you are using this medicine.

Warnings While Using This Medicine

  • You can harm your unborn baby if you use this medicine together with ribavirin while you are pregnant. These medicines may also cause birth defects if the father is using it when his sexual partner becomes pregnant. Tell your doctor right away if a pregnancy occurs while you are using these medicines, .
  • Your doctor will ask you to have a pregnancy test before you start using this medicine to make sure you are not pregnant. You must have a negative pregnancy test before you will be allowed to use this medicine with ribavirin. You must use 2 forms of birth control during treatment and for 6 months after treatment ends. You should have a pregnancy test every month while you are using this medicine and after your treatment ends.
  • Make sure your doctor knows if you are breastfeeding, or if you have kidney disease, liver disease, bleeding problems, bone marrow disease (such as aplastic anemia), breathing problems, lung disease, heart or blood vessel disease, chest pain, a history of a heart attack, stroke, or heart rhythm problems, or high blood pressure. Tell your doctor if you have thyroid problems, cancer, colitis, diabetes, hypoglycemia (low blood sugar), diabetic retinopathy, eye or vision problems, nerve problems, pancreatitis, stomach or bowel problems, immune system problems, or an autoimmune disorder (such as psoriasis, lupus, or arthritis).
  • Make sure your doctor knows if you have a history of depression, bipolar disorder, HIV or AIDS, or an addiction to drugs or alcohol. Also, tell your doctor if you are on dialysis or have ever had an organ transplant.
  • You might have mood or behavior changes with this medicine, such as feeling sad, hopeless, anxious, or easily upset. You could feel nervous or hostile. Some people become violent and want to hurt themselves or others. You may see or hear unusual things. Call your doctor right away if you have any strange feelings, thoughts, or behaviors.
  • Serious skin reactions can occur with this medicine. Stop using this medicine and check with your doctor right away if you have blistering, peeling, or loosening of the skin; a fever or chills; hives or welts; red skin lesions; a severe skin rash or acne; or sores or ulcers on the skin.
  • You can still give hepatitis B or hepatitis C to other people while you are taking this medicine.
  • This medicine lowers the number of some types of blood cells in your body. Because of this, you may bleed or get infections more easily. To help with these problems, avoid being near people who are sick or have infections. Wash your hands often. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Brush and floss your teeth gently. Be careful when using sharp objects, including razors and fingernail clippers.
  • Check with your doctor right away if you have back, leg, or stomach pains; bleeding gums or nosebleeds; chills; dark urine; difficulty breathing; fever; general body swelling; headache; loss of appetite; nausea or vomiting; pale skin; sore throat; unusual tiredness or weakness; or yellowing of the eyes or skin. These could be symptoms of a blood disorder called anemia.
  • Check with your doctor right away if blurred vision, difficulty with reading, eye pain, or any other change in vision occurs during or after treatment. Your doctor may want you to have your eyes checked by an eye doctor.
  • If you have severe diarrhea, ask your doctor before taking any medicine to stop the diarrhea.
  • Stop using this medicine and check with your doctor right away if you have sudden and severe stomach pain, chills, constipation, nausea, vomiting, fever, or lightheadedness. These could be symptoms of pancreatitis.
  • Peginterferon alfa-2a used together with ribavirin may affect your child's growth. Your doctor may need to check your child's height and weight during and after treatment with these medicines.
  • Peripheral neuropathy may occur if you use this medicine together with telbivudine (Tyzeka®). Check with your doctor right away if you are having burning, numbness, tingling, or painful sensations in the arms, hands, legs, or feet.
  • Your doctor will need to check your blood at regular visits while you are using this medicine. Be sure to keep all appointments.
  • This medicine may make you dizzy or drowsy. Do not drive, use machines, or do anything else that could be dangerous if you are not alert.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, or red skin rash
  • Bloody or black, tarry stools
  • Change in how much or how often you urinate, burning or painful urination
  • Chest pain or uneven heartbeat
  • Coughing up yellow or pink mucus (phlegm)
  • Fever that does not go away or gets higher
  • Fever, chills, cough, sore throat, and body aches
  • Increased thirst
  • Joint pain or stiffness
  • Numbness, tingling, or burning pain in your hands, arms, legs, or feet
  • Stomach pain or bloody diarrhea
  • Sudden and severe stomach pain, nausea, vomiting, and lightheadedness
  • Trouble seeing or change in your vision
  • Trouble with breathing
  • Unexplained weight loss or gain
  • Unusual bleeding, bruising, or weakness
  • Unusual thoughts or behaviors, depression, irritability, nervousness, or thoughts of hurting yourself or others
  • Yellowing of your skin or the whites of your eyes

If you notice these less serious side effects, talk with your doctor:

  • Hair loss
  • Headache
  • Loss of appetite
  • Mild flu-like symptoms, such as muscle aches, low fever, or tiredness
  • Muscle pain
  • Redness, pain, itching, or bruising where the shot was given
  • Trouble sleeping
  • Weakness

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last Reviewed on 06/12/2013

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This page was last updated: September 18, 2013

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