Pegasys
Pegasys (peginterferon alfa-2a) is an interferon alpha. It's used to treat chronic (long-term) hepatitis B and hepatitis C in children and adults, sometimes in combination with other antivirals. Pegasys (peginterferon alfa-2a) is injected under the skin, typically once per week. The most common side effects of this medication include tiredness, headache, and fever.
What is Pegasys (peginterferon alfa-2a)?
What is Pegasys (peginterferon alfa-2a) used for?
Long-term hepatitis C in people ages 5 years and older (in combination with other medications)
Long-term hepatitis B in people ages 3 years and older
How Pegasys (peginterferon alfa-2a) works
Pegasys (peginterferon alfa-2a) is an interferon alpha. It's not completely clear how Pegasys (peginterferon alfa-2a) works, but it's thought to activate proteins of your immune system to attack hepatitis B and hepatitis C viruses and stop them from growing.
Drug Facts
Get your GoodRx coupon
What are the side effects of Pegasys (peginterferon alfa-2a)?
Common Side Effects
- Tiredness/fatigue (56%)
- Headache (54%)
- Muscle pain (37%)
- Fever (37%)
- Chills (35%)
- Joint pain (28%)
- Nausea/vomiting (24%)
- Hair loss (23%)
- Pain, swelling, or redness at injection site (22%)
- Anxious/nervousness (19%)
- Difficulty sleeping (19%)
- Depression (18%)
- Loss of appetite (17%)
- Diarrhea (16%)
- Dizziness (16%)
- Stomach pain (15%)
- Itching (12%)
- Pain (11%)
- Flu-like symptoms (fever, cough, short of breath) (81%)
- Stomach problems (nausea, vomiting, diarrhea, stomach pain) (44%)
- Pain, swelling, or redness at injection site (42%)
- Headache (39%)
- Muscle pain (29%)
- Tiredness/weakness (20%)
- Irritated/angry feeling (14%)
- Itching (12%)
- Difficulty sleeping (12%)
- Rash (10%)
Other Side Effects
- Back pain
- Difficulty concentrating
- Skin irritation
- Sweating
- Impaired memory
- Rash
- Low platelet count
- Dry skin
- Blurry vision
- Weight loss
- Shortness of breath
- Cough
- Lack of energy/strength
- Bloody nose
- Nausea
- Upper respiratory infection
- Hair loss
- Low appetite
- Dizziness
- Common cold
Serious Side Effects
- Serious allergic reactions: hives, itching, swelling of face or tongue, difficulty breathing
- Bleeding that's difficult to stop
- Depression and thoughts of self-harm
- Heart problems: high blood pressure, fast and irregular heart beat, chest pain, heart attacks
- Severe skin reactions: blisters or sores on skin, painful rash, redness over large parts of the body
- Autoimmune disorders
- Stroke or brain bleed: facial drooping on one side, slurred speech, weakness, dizziness, headache, confusion, vision loss
- Severe or fatal infections: fever, difficulty breathing, diarrhea, weakness
- Worsening liver problems or liver failure: swelling of your stomach, yellowing of your skin or the whites of your eyes, confusion
- Lung problems: lung infection, shortness of breath, high blood pressure in the lung, lung failure
- Inflamed intestines and pancreas: stomach or back pain, bloody diarrhea, fever, sweating, loss of appetite, nausea, vomiting
Source:Â DailyMed
The following side effects have also been reported
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
chills
discouragement
feeling sad or empty
irritability
lack of appetite
loss of interest or pleasure
lower back or side pain
painful or difficult urination
pale skin
tiredness
trouble sleeping
trouble 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
confusion
depressed mood
dizziness
dry skin and hair
fainting
fast heartbeat
feeling cold
headache
heart murmur
hoarseness or husky voice
lightheadedness
muscle cramps and stiffness
pale skin
rapid, shallow breathing
slowed heartbeat
stomach pain
tightness in the chest
troubled breathing with exertion
Incidence not known
Accumulation of pus in the arms or legs
blistering, peeling, loosening of the skin
decreased urination
increase in heart rate
joint or muscle pain
red, irritated eyes
red skin lesions, often with a purple center
seizures
sunken eyes
swollen, red, tender area of infection in the arms or legs
thirst
wrinkled skin
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
cracked, dry, scaly skin
crusting, irritation, itching, or reddening of the skin
fear
feeling unusually cold, shivering
hair loss or thinning of the hair
muscle or joint pain
nervousness
numbness
rash
redness
soreness
stinging
swelling
tenderness
tingling
ulceration
vomiting
warmth
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.
Pros and cons of Pegasys (peginterferon alfa-2a)
Pros
Given only once per week
An option for children as young as 5 years old
Available as a prefilled syringe for easier use
Cons
Can cause serious side effects, including mental health conditions and risk of serious infection
No longer recommended for hepatitis C treatment
Might be difficult for some people to administer correctly
Pharmacist tips for Pegasys (peginterferon alfa-2a)
Mark your calendar with your appointments to see your provider and get any blood work done. Pegasys (peginterferon alfa-2a) can potentially cause a lot of side effects, so it's important to receive regular follow-up to see how you're responding to the medication and if you're having side effects.
Pegasys (peginterferon alfa-2a) commonly causes flu-like symptoms, such as tiredness, weakness, fever, chills, muscle aches, joint pain, and headaches. It's best to take Pegasys (peginterferon alfa-2a) in the evening to help lower your risk of getting these symptoms.
If you do develop flu-like symptoms, make sure to stay hydrated and ask your provider what over-the-counter cold and flu medications might be appropriate for you.
Pegasys (peginterferon alfa-2a) can make you dizzy, confused, or tired. Don't do anything that requires concentration until you know how this medication affects you.
Avoid drinking alcohol while taking Pegasys (peginterferon alfa-2a) because it can worsen side effects (e.g., sleepiness, dizziness). In addition, doing so can also worsen liver injury.
Pegasys (peginterferon alfa-2a) is injected weekly. You should inject Pegasys (peginterferon alfa-2a) on the same day and around the same time each week.
If you miss your dose of Pegasys (peginterferon alfa-2a) by less than 2 days, give yourself the medication as soon as you remember. Then, take the next dose on the day you normally take it. But if it has been more than 2 days since your missed dose, contact your provider.
You must avoid Pegasys (peginterferon alfa-2a) if you or your partner is pregnant because it can cause severe harm to an unborn baby. Talk to your provider about family planning before starting Pegasys (peginterferon alfa-2a) with or without ribavirin.
More tips for how to inject Pegasys (peginterferon alfa-2a) under the skin at home:
Make sure you know how to give yourself Pegasys (peginterferon alfa-2a) to avoid accidentally hurting yourself or wasting the medication. Read the instructions for use for either the vial or prefilled syringe and contact your provider or pharmacist if you have any questions on how to use this medication.
Store Pegasys (peginterferon alfa-2a) in the refrigerator and keep in the original container to protect it from light.
When you're ready to give yourself the medication, take it out of the refrigerator. If you're using the vial, warm it up by gently rolling it in your hands for about 1 minute. If you're using the prefilled syringe, lay it on a flat surface and wait a few minutes for it to warm up and for the moisture on the outside of the syringe to disappear. Don't shake the medication or try to warm it up any other way.
Always check the medication solution to make sure it's clear and colorless to slightly yellowish before using it. If it's cloudy or has particles, don't use it. Contact your provider or pharmacist about giving you a replacement.
Use a different place in your thigh or stomach each time you give yourself the medication. This will help with preventing bruising or irritation on your skin.
After giving yourself the medication, throw away the medication and syringe with needle by placing them in a sharps container or something made of heavy-duty plastic (e.g., empty milk carton, laundry detergent bottle). This lowers the risk of needlestick injuries. Don't throw them away in the trash. Visit the FDA's website to learn more about following your state regulations to dispose of your sharps safely.
Frequently asked questions about Pegasys (peginterferon alfa-2a)
How to save using GoodRx
What are the risks and warnings for Pegasys (peginterferon alfa-2a)?
Pegasys (peginterferon alfa-2a) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Potential harm or death to your unborn baby
Risk factors: Currently pregnant | Women of childbearing age | Men taking ribavirin (Rebetol) who have female partners of childbearing age
Animal studies have shown that Pegasys (peginterferon alfa-2a) can cause harm to unborn babies and has potential to cause an abortion or miscarriage. Additionally, ribavirin (Rebetol), a medication commonly used together with Pegasys (peginterferon alfa-2a), must be avoided in pregnant women and in men whose partners are pregnant because it can cause harm to an unborn baby, including death. If using Pegasys (peginterferon alfa-2a) and ribavirin (Rebetol) together, women of childbearing age, including those who are partners of men who take these medications, must have a negative pregnancy test before starting treatment. They must also complete monthly pregnancy tests and use two forms of birth control during treatment and for at least 6 months after stopping ribavirin (Rebetol). If you or your female partner becomes pregnant while taking Pegasys (peginterferon alfa-2a) and ribavirin (Rebetol) or within 6 months after you finish treatment, let your provider know right away. It's also encouraged that you contact the Ribavirin Pregnancy Registry, which will monitor the health of you and your baby, by calling 1-800-593-2214.
Talk to your provider about family planning before starting Pegasys (peginterferon alfa-2a) with or without ribavirin (Rebetol).
Mental health problems
Risk factors: History of depression
Pegasys (peginterferon alfa-2a) can cause serious, life-threatening mental health problems. Symptoms include thoughts of harming yourself or others, depression, aggressive behavior, and seeing things that aren't real. This can happen to anyone taking Pegasys (peginterferon alfa-2a), but the risk is higher if you have a history of depression. Let your provider know if you or your loved ones notice a change in your mood or behavior, or if you have thoughts of hurting yourself while you're taking Pegasys (peginterferon alfa-2a). Depending on how severe your symptoms are, your provider might have you stop taking the medication.
Autoimmune disorders
Risk factors: History of autoimmune conditions
Pegasys (peginterferon alfa-2a) can cause autoimmune conditions, such as myositis (inflamed muscles), hepatitis, psoriasis (inflamed skin), rheumatoid arthritis (inflamed joints), interstitial nephritis (inflamed kidneys), or make them worse. Some of these can be life-threatening. Make sure you have routine tests and office visits so your provider can monitor your health.
Stroke or bleeding in the brain
Strokes and brain bleeds have been reported in people taking Pegasys (peginterferon alfa-2a), including in people who have little to no risk factors for stroke. It's not known how frequently these events have occurred. Call 911 right away if you experience facial drooping on one side, slurred speech, weakness, dizziness, headache, confusion, or vision loss.
Infections
Risk factors: History of low white blood cell count
Severe, life-threatening infections have been reported in people taking Pegasys (peginterferon alfa-2a). Fever is a common side effect of Pegasys (peginterferon alfa-2a), but it can also be a sign of an infection. If you develop a fever or any other signs of an infection (e.g., cough, shortness of breath, weakness, chills, sweating), contact your provider so you can be tested for an infection.
Numbness or pain in your hands or feet (peripheral neuropathy)
Risk factors: Using Pegasys (peginterferon alfa-2a) with telbivudine (Tyzeka)
Using Pegasys (peginterferon alfa-2a) and telbivudine (Tyzeka) together can cause or worsen peripheral neuropathy (damage to the nerves causing numbness and pain in your hands and feet). Let your provider know if you're taking telbivudine (Tyzeka) before starting Pegasys (peginterferon alfa-2a).
Worsening liver problems and liver failure
Risk factors: History of liver problems | Taking certain HIV medications together with Pegasys (peginterferon alfa-2a)
Pegasys (peginterferon alfa-2a) can cause serious liver problems that can lead to liver failure or death. Your risk might be higher if you're also taking certain HIV NRTIs (e.g., abacavir (Ziagen), zidovudine, lamivudine (Epivir), etc.). You might need to get regular blood tests done to make sure your liver is working properly. Seek medical attention right away if you notice swelling of your stomach, yellowing of your skin or the whites of your eyes, stool changes (black, tarry, or bloody stools), coughing or vomiting up blood, confusion, slurred speech, mood swings, or changes in personality.
Heart problems
Risk factors: History of heart disease
High blood pressure, fast and irregular heartbeat, chest pain, and heart attacks have been reported in people taking Pegasys (peginterferon alfa-2a). If you have a history of heart problems, talk to your provider to see if Pegasys (peginterferon alfa-2a) is right for you.
Low blood cell counts
Risk factors: History of low blood cell counts | Taking Pegasys (peginterferon alfa-2a) with ribavirin (Rebetol) and azathioprine (Imuran) | Coinfection with HIV
Pegasys (peginterferon alfa-2a) can affect the way your cells work, which can lead to low blood cell counts. This can raise your risk of serious infections, bleeding, and anemia (low red blood cells). Your risk is higher if you have HIV, or if you're taking Pegasys (peginterferon alfa-2a) with ribavirin (Rebetol) and azathioprine (Imuran). You'll need to have lab tests done before and during treatment with Pegasys (peginterferon alfa-2a) so your provider can make sure your blood cell counts are in the normal range. If your blood counts drop too low, you'll likely need to stop taking Pegasys (peginterferon alfa-2a). If you develop any signs of infection (e.g., fever, tiredness, chills, cough, trouble breathing) or signs of bleeding (pale skin, fast heart rate, lightheadedness, blood in your urine or stool), contact your provider right away.
Hormone problems
Risk factors: History of high blood sugar or thyroid conditions
Pegasys (peginterferon alfa-2a) can cause or worsen diabetes and thyroid problems. Let your provider know if you're taking medications for diabetes or thyroid disease before you start taking Pegasys (peginterferon alfa-2a) because it might not be the best option for you until your conditions are stable.
Eye and vision problems
Pegasys (peginterferon alfa-2a) can cause serious eye and vision problems, including retinal detachment and blindness. You'll need an eye exam before starting Pegasys (peginterferon alfa-2a) and occasional exams during treatment if you have a history of eye problems. Let your provider know if you have any changes in your vision while taking Pegasys (peginterferon alfa-2a).
Lung problems
Pegasys (peginterferon alfa-2a) can cause or worsen breathing and lung problems, such as lung infections (pneumonia) or high blood pressure in the lungs (pulmonary hypertension). In severe cases, lung problems can lead to death. Let your provider know if you have shortness of breath or breathing problems. Your provider can order a chest X-ray to check on your lung health.
Intestine and pancreas problems
Pegasys (peginterferon alfa-2a) can cause inflammation of the intestines or pancreas, and can sometimes be life-threatening. If you experience bloody diarrhea, fever, nausea, vomiting, or abdominal pain, contact your provider right away.
Delayed growth in children
Children can experience a delay in growth (both height and weight) during treatment with Pegasys (peginterferon alfa-2a) with or without ribavirin (Rebetol). Children might be able to catch-up in growth after they stop taking Pegasys (peginterferon alfa-2a), but there isn't enough information available to know what the long-term effects of the medication are on children's growth.
Severe allergic and skin reactions
Pegasys (peginterferon alfa-2a) can cause severe allergic and skin reactions. Get medical help right away if you experience hives, blisters, swelling or redness in any of your body parts, tightening of your chest, or trouble breathing.
Pegasys (peginterferon alfa-2a) dosage forms
Typical dosing for Pegasys (peginterferon alfa-2a)
Hepatitis C
Age 18 years and older: The typical dose is 180 mcg injected under the skin in the thigh or stomach once weekly.
Age 5 to under 18 years: Your child's provider will determine the dose based on your child's body surface area (BSA), which takes into account height and weight. Pegasys (peginterferon alfa-2a) is injected under the skin in the thigh or stomach once weekly. The maximum dose is 180 mcg per week.
The length of treatment with Pegasys (peginterferon alfa-2a) depends on your age, if you have HIV, the type of hepatitis C virus you have, and if you're taking other hepatitis C medications.
Hepatitis B
Age 18 years and older: The typical dose is 180 mcg injected under the skin in the thigh or stomach once weekly for 11 months.
Age 3 to under 18 years: Your child's provider will determine the dose based on your child's BSA. Pegasys (peginterferon alfa-2a) is injected under the skin in the thigh or stomach once weekly for 11 months. The maximum dose is 180 mcg per week.
Your dose might differ if you have kidney problems. Your provider might change your dose based on your lab results or if you develop side effects from Pegasys (peginterferon alfa-2a).
Interactions between Pegasys (peginterferon alfa-2a) and other drugs
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.
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.
How much does Pegasys (peginterferon alfa-2a) cost?
Pegasys (peginterferon alfa-2a) contraindications
Autoimmune hepatitis (liver damage caused by the immune system attacking the liver)
Worsening liver function in patients with liver scarring (cirrhosis) before starting Pegasys (peginterferon alfa-2a)
Age under 1 year old
What is the latest news about Pegasys (peginterferon alfa-2a)?
Pegasys (peginterferon alfa-2a) images
Get savings updates for Pegasys (peginterferon alfa-2a)
Receive price alerts, news, and other messages from GoodRx about Pegasys (peginterferon alfa-2a) and other healthcare topics and relevant savings offers.By providing your email, you consent to receive marketing communications from GoodRx, which may include content and/or data related to men’s health, women's health, reproductive care, or sexual health. You agree to the GoodRx Terms of Use and acknowledge the Privacy Policy. You can unsubscribe at any time.
References
Best studies we foundAmerican Lung Association. (n.d.). Pneumonia.
Bhattacharya, D., et al. (2023). Hepatitis C guidance 2023 update: American Association for the Study of Liver Diseases– Infectious Diseases Society of America recommendations for testing, managing, and treating hepatitis C virus infection. Clinical Infectious Diseases.
Centers for Disease Control and Prevention. (2019). Pulmonary hypertension.
Genentech, Inc. (2021). Pegasys- peginterferon alfa-2a injection, solution [package insert]. DailyMed.
Khanna, N. R., et al. (2023). Interferon. StatPearls.
Palumbo, E. (2011). Pegylated interferon and ribavirin treatment for hepatitis C virus infection. Therapeutic Advances in Chronic Disease.
pharmaand GmbH. (2024). Pegasys- peginterferon alfa-2a injection, solution [package insert]. DailyMed.
U.S. Food and Drug Administration (2021). Safely using sharps (needles and syringes) at home, at work and on travel.
Wong, G. L. H., et al. (2022). How to achieve functional cure of HBV: Stopping NUCs, adding interferon or new drug development? Journal of Hepatology.
Compare other Hepatitis B, Hepatitis C drugs
Browse medications
View AllResearch prescriptions and over-the-counter medications from A to Z, compare drug prices, and start saving.