Peginterferon alfa-2a is used alone or in combination with other medications to treat chronic hepatitis B and chronic hepatitis C, viral infections of the liver. It works by decreasing the amount of hepatitis virus in the body and helps your body's natural defense (immune system) fight the infection. Chronic hepatitis infection can lead to serious liver damage (cirrhosis) and liver cancer.

It is not known if peginterferon can cure hepatitis B or hepatitis C infections or can prevent you from passing the virus to others. Practice "safer sex" (such as the use of latex condoms) to lower the risk of passing the virus to others.

Read the Medication Guide and Instructions for Use provided by your pharmacist before you start using peginterferon alfa-2a and each time you get a refill. Ask your health care professional how to prepare and use this medication. If you have any questions, ask your doctor or pharmacist.

Inject this medication under the skin as directed by your doctor, usually once every week. The injection is given in the abdomen or thigh. Do not inject near the belly button or at the waistline. The dosage is based on your medical condition, lab tests, and response to treatment. Children's dosage is also based on body size.

For a more comfortable injection, take the medication out of the refrigerator and let it warm to room temperature as directed in the Instructions for Use. Do not warm up this medication any other way (for example, do not heat it in the microwave or place it in hot water). Do not shake this medication. Before using, check this product for particles or discoloration. If either is present, do not use the liquid. Before injecting each dose, clean the skin you are going to inject into (the injection site) with rubbing alcohol. Change the injection site each time to lessen injury under the skin. To lessen bruising, do not rub the injection site after a shot. Learn how to store and discard medical supplies safely.

Use this medication regularly to get the most benefit from it. To help you remember, use it at about the same time on the same day each week.

Drink plenty of fluids while using this medication unless your doctor directs you otherwise.

See also Warning section.

Most people have flu-like symptoms such as headache, tiredness, fever, chills, and muscle aches, but these usually decrease after the first few weeks of treatment. You can lessen these side effects by injecting this medicine at bedtime and using fever reducers/pain relievers such as acetaminophen before each dose. Ask your doctor or pharmacist for more information. Nausea, vomiting, diarrhea, dry mouth, loss of appetite, dizziness, trouble sleeping, or redness/swelling at the injection site may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Tooth and gum problems may sometimes occur during treatment. Having a dry mouth can worsen this side effect. Prevent dry mouth by drinking plenty of water or using a saliva substitute. Brush your teeth well at least twice a day and have regular dental exams. If you vomit, rinse your mouth afterward to lessen the chance of tooth and gum problems.

Temporary hair loss may occur. Normal hair growth should return after treatment has ended.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• easy bleeding/bruising
• feeling too hot or cold (more than others around you)
• gradual change in weight (without a change in diet or exercise)
• unusually slow/fast/pounding heartbeat
• increased thirst/urination
• black/tarry stools
• signs of liver problems (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine)
• numbness/tingling of arms/legs

Get medical help right away if you have any very serious side effects, including:

• chest pain
• seizures
• symptoms of a stroke (such as weakness on one side of the body, trouble speaking, confusion)
• vision changes (such as blurred vision, partial loss of vision)

This drug may cause serious mental/mood changes that may get worse during treatment or after your last dose. Tell your doctor right away if you have symptoms such as confusion, depression, thoughts of suicide or hurting others, unusual irritability, or aggressive behavior.

This medication may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Tell your doctor right away if you have any signs of infection (such as sore throat that doesn't go away, fever, chills, cough).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

See also Warning section.

Before using peginterferon alfa-2a, tell your doctor or pharmacist if you are allergic to it; or to polyethylene glycol (PEG); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• other liver problems (such as autoimmune hepatitis)
• mental/mood disorders (such as depression, psychosis, suicidal thoughts)
• autoimmune disorders (such as rheumatoid arthritis, lupus, psoriasis)
• bleeding/blood problems
• diabetes
• heart problems
• high blood pressure
• intestinal problems (such as colitis)
• kidney disease
• lung problems (such as chronic obstructive pulmonary disease-COPD)
• pancreatitis
• high triglyceride levels
• thyroid problems
• drug or alcohol use/abuse

This medication can make you more likely to get infections or may make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to your doctor if you have been exposed to an infection or for more details.

Tell your health care professional that you are using peginterferon alfa-2a before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports.

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Children may be more sensitive to the side effects of this drug, especially mental/mood changes (such as severe depression, thoughts/attempts of suicide). Peginterferon alfa-2a may also slow down a child's growth and the final adult height may be lower than expected. See the doctor regularly so your child's height and weight can be checked.

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using peginterferon alfa-2a. Peginterferon alfa-2a may harm an unborn baby. Ask about reliable forms of birth control while using this medication. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as blood counts, thyroid tests, virus levels, kidney/liver function, triglyceride levels, eye exams) should be done before you start using this medication and while you are using it. Keep all medical and lab appointments.

Do not change brands of interferon without asking your doctor or pharmacist. Other interferons may not have the same effects on your disease.

If you miss a dose, use it as soon as you remember if it is within 2 days after your scheduled dose. Use your next dose on the day you usually use it. If more than 2 days have passed since your missed dose, ask your doctor or pharmacist right away for a new dosing schedule.

Store in the refrigerator away from light and moisture. Do not freeze. Do not leave out of the refrigerator for more than 24 hours. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.