Health Guide

Peginterferon Alfa-2a (Subcutaneous route)


peg-in-ter-FEER-on AL-fa-2a

Brand Names:

  • Pegasys
  • Pegasys Proclick

Dosage Forms:

  • Solution


Subcutaneous route(Solution)

Alpha interferons may cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders. Clinical and laboratory monitoring is recommended. If severe or worsening signs or symptoms of these conditions occur, treatment should be discontinued .



Immunological Agent


Interferon, Alfa (class)

Uses of This Medicine:

Peginterferon alfa-2a injection is used alone or together with other medicines, such as ribavirin (Copegus®, Rebetol®), boceprevir (Victrelis®), and telaprevir (Incivek®), to treat chronic hepatitis C infection. It is also used to treat adult patients with chronic hepatitis B infection. Peginterferon alfa-2a is a synthetic (man-made) version of a substance that is normally produced in the body. It helps your immune system fight hepatitis infections.

This medicine is available only with your doctor's prescription.

Before Using This Medicine:

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Appropriate studies have not been performed on the relationship of age to the effects of peginterferon alfa-2a injection in children younger than 5 years of age. Safety and efficacy have not been established.

Older adults—

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of peginterferon alfa-2a injection in the elderly. However, elderly patients are more likely to have age-related kidney problems, which may require caution and an adjustment in the dose for patients receiving peginterferon alfa-2a.


Pregnancy CategoryExplanation
All TrimestersCAnimal studies have shown an adverse effect and there are no adequate studies in pregnant women OR no animal studies have been conducted and there are no adequate studies in pregnant women.


There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Other medicines—

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Telbivudine

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Theophylline

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Methadone

Other interactions—

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other medical problems—

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Anemia or
  • Bleeding problems, history of or
  • Chest pain or
  • Colitis (inflammation of intestines) or
  • Depression, history of or
  • Diabetes or
  • Diabetic retinopathy (eye problem caused by diabetes) or
  • Eye or vision problems (eg, optic neuritis, retinopathy) or
  • Heart or blood vessel disease or
  • Heart rhythm problems (eg, arrhythmia), history of or
  • Hyperglycemia (high blood sugar) or
  • Hypertension (high blood pressure) or
  • Hypoglycemia (low blood sugar) or
  • Kidney disease, severe or
  • Lung disease (eg, pneumonia, sarcoidosis) or
  • Manic episodes (bipolar depression), history of or
  • Neutropenia (low white blood cells) or
  • Psoriasis (skin disease) or
  • Psychiatric problems, history of or
  • Rheumatoid arthritis or
  • Stroke, history of or
  • Systemic lupus erythematosus (immune system disorder) or
  • Thrombocytopenia (low blood platelet count) or
  • Thyroid disease—Use with caution. May make these conditions worse.
  • Autoimmune hepatitis (serious liver disease) or
  • Liver disease (eg, cirrhosis), severe—Should not be used in patients with these conditions.
  • Infection (eg, bacteria, virus, or fungus)—May decrease your body's ability to fight an infection.
  • Organ transplant (eg, liver)—Use of peginterferon alfa-2a alone or in combination with ribavirin have not been studied in patients with this condition.

Proper Use of This Medicine:

A nurse or other trained health professional may give you this medicine. This medicine is given as a shot under your skin, usually in the stomach or thighs. You may be taught how to give this medicine at home. Make sure you understand all of the instructions before giving yourself an injection. Do not use more medicine or use it more often than your doctor tells you to.

Each package of peginterferon alfa-2a contains a Medication Guide. Read the instructions carefully and make sure you understand:

  • How to prepare the injection.
  • Proper use of disposable syringes.
  • How to give the injection.
  • How long the injection is stable.

If you have any questions about any of this, check with your doctor.

This medicine is available in 3 dosage forms: a vial (glass container), a prefilled syringe, or a disposable autoinjector. If you switch from using the vial to using the prefilled syringe or autoinjector, double-check that you are giving yourself the correct amount of medicine.

Use each vial, syringe, or autoinjector only one time. You might not use all of the medicine. Do not save an open vial, syringe, or autoinjector. If the medicine in the vial or syringe has changed color, or if you see particles in it, do not use it.

Drink extra fluids while you are using this medicine. This will keep you well hydrated, especially during the early part of your treatment.


The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For injection dosage form:
    • For hepatitis B and hepatitis C:
      • Adults—Dose is based on body weight and must be determined by your doctor. It is usually 180 micrograms (mcg) injected under the skin once a week for 48 weeks. The medicine should be used on the same day each week and at approximately the same time.
      • Children—Use and dose must be determined by your doctor.
    • For hepatitis C infection, in combination with ribavirin:
      • Adults—Dose is based on body weight and must be determined by your doctor. It is usually 180 micrograms (mcg) injected under the skin once a week (same time and day each week) together with oral ribavirin twice daily for 24 to 48 weeks. The length of time will be determined by your doctor.
      • Children 5 years of age and older—Dose is based on body weight or body size and must be determined by your doctor. It is usually 180 mcg injected under the skin once a week (same time and day each week) together with oral ribavirin twice daily for 24 to 48 weeks. The length of time will be determined by your doctor.
      • Children younger than 5 years of age—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

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.


Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Store in the refrigerator. Do not freeze.

Do not leave this medicine out of the refrigerator for more than 24 hours. Do not freeze or shake. 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.

Precautions While Using This Medicine:

It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Using this medicine together with ribavirin while you are pregnant can harm your unborn baby. These medicines may also cause birth defects if the father is using it when his sexual partner becomes pregnant. If a pregnancy occurs while you are using these medicines, tell your doctor right away.

A negative pregnancy test is needed for women who are of childbearing age before starting treatment with this medicine and ribavirin. Effective birth control must be used by male and female patients during treatment and for 6 months after the last dose. Female patients will need to have pregnancy tests every month during treatment and for 6 months after the last dose.

You should not use peginterferon alfa-2a together with ribavirin if you are also taking didanosine (Videx®, Videx® EC). Using these medicines together may cause serious problems.

This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. If you, your child, or your caregiver notice any of these side effects, tell your doctor right away.

This medicine may cause serious allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Call your doctor right away if you have itching, hives, hoarseness, trouble with breathing, trouble with swallowing, or any swelling of the hands, face, or mouth while you are using this medicine.

Serious skin reactions can occur with this medicine. Check with your doctor right away if you have blistering, peeling, or loosening of the skin, fever or chills, hives or welts, red skin lesions, a severe skin rash or acne, or sores or ulcers on the skin while you are using this medicine.

This medicine will not keep you from giving hepatitis B or hepatitis C to other people.

This medicine combined with ribavirin can temporarily lower the number of white blood cells in your blood, which will increase the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

  • If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
  • Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin.
  • Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
  • Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
  • Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
  • Avoid contact sports or other situations where bruising or injury could occur.

Check with your doctor right away if you or your child have back, leg, or stomach pains, bleeding gums, chills, dark urine, difficulty breathing, fever, general body swelling, headache, loss of appetite, nausea or vomiting, nosebleeds, pale skin, sore throat, unusual tiredness or weakness, or yellowing of the eyes or skin. These could be symptoms of a blood disorder called hemolytic anemia.

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.

Check with your doctor immediately if you have vision changes, such as blurred vision, difficulty reading, or eye pain during or after treatment. This could be a symptom of a serious eye problem. Your doctor may want an eye doctor to check your eyes.

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.

This medicine may cause some people to become drowsy, dizzy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy and not alert.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Side Effects of This Medicine:

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common
Black, tarry stools
feeling sad or empty
lack of appetite
loss of interest or pleasure
lower back or side pain
painful or difficult urination
pale skin
shortness of breath
sore throat
trouble sleeping
trouble with concentrating
ulcers, sores, or white spots in the mouth
unusual bleeding or bruising
unusual tiredness or weakness
Less common
Bone pain
chest pain or discomfort
depressed mood
dry skin and hair
fast heartbeat
feeling cold
hair loss
heart murmur
hoarseness or husky voice
muscle cramps and stiffness
pale skin
rapid, shallow breathing
slowed heartbeat
stomach pain
tightness in the chest
troubled breathing with exertion
weight gain

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
Back pain
blistering, crusting, irritation, itching, or reddening of the skin
cracked, dry, scaly skin
dry mouth
feeling unusually cold, shivering
hair loss or thinning of the hair
muscle or joint pain
stomach pain
Less common
Acid or sour stomach
blurred vision
memory problems
stomach discomfort or upset
Incidence not known
Change of hearing
loss of hearing

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

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

Last Updated: 9/4/2017
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