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Peginterferon Alfa-2a - Uses, Mechanism of Action, Contraindications, and Precautions

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Peginterferon alfa-2a is a drug that is used to treat chronic hepatitis C and B. The article explains the drug further in detail.

Medically reviewed by

Dr. Muhammad Zohaib Siddiq

Published At May 23, 2023
Reviewed AtMay 23, 2023


Peginterferon alfa-2a is a modified form of the human interferon and is used to treat hepatitis C and B viruses by stimulating the innate antiviral response of the body.

How Does Peginterferon Alfa-2a Work?

Peginterferon alfa-2a is obtained from recombinant human interferon's alfa-2a component. It binds to the human type 1 interferon receptors and activates them, causing their dimerization. This activates the Janus kinases-signal transducer and activator of the transcription proteins (JAK-STAT) pathway. This activation of the JAK-STAT pathway increases the expression of multiple genes in different tissues related to the innate antiviral response.

Uses of Peginterferon Alfa-2a:

Peginterferon alfa-2a is indicated in treating the following conditions:

  1. Chronic Hepatitis C - Peginterferon alfa-2a, alone or in combination with other drugs, is indicated for treating chronic hepatitis C in five years of age and older who have liver disease and have not been previously treated with interferon-alpha.

  2. Chronic Hepatitis B - Peginterferon alfa-2a is also indicated for treating people with HBeAg positive and HBeAg harmful chronic hepatitis B infection and has compensated liver disease, viral replication, and liver inflammation.

Limitations - Peginterferon alfa-2a should not be used in individuals sensitive to the drug or its components.

Dosage Restrictions:

1. Route of Administration - Subcutaneous route.

2. Dosage Strengths:

  • 180 mcg/mL.

  • 180 mcg/0.5 mL.

  • 135 mcg/0.5 mL.

3. Dosage Forms

  • Vials and prefilled syringes for single use.

  • Autoinjector for single use.

  • It is sterile, free of preservatives, and colorless to a yellowish injectable solution.

Special Considerations:

  • Gender and Age - Peginterferon alfa-2a showed similar effects in both males and females, but the drug exposure seems to be more in those above 62 years of age.

  • Pediatric Usage - The efficacy of Peginterferon alfa-2a in kids below five has not been established. The benzyl alcohol in Peginterferon-alfa-2a has been found to cause neurological and other complications in kids.

  • Elderly - The side-effects of Peginterferon alfa-2a, such as cardiac, central nervous system, and systemic effects, can affect the elderly more, so precaution should be taken in administering the drug.

  • Hepatic Impairment - Individuals with chronic hepatitis C with liver cirrhosis may be at an increased risk of hepatic decompensation and death when treated with Peginterferon alfa-2a.

  • Renal Impairment - Individuals with renal impairment should be monitored for abnormalities, such as decreased hemoglobin levels and side effects, and undergo proper creatinine clearance. Peginterferon alfa-2a therapy should be stopped in individuals with significant severe abnormalities.

Warnings and Contraindications

Peginterferon alfa-2a is contraindicated in the following conditions:

  • Hypersensitivity to Peginterferon alfa-2a or any of its components.

  • Hepatic decompensation in people with liver cirrhosis before treatment.

  • Hepatic decompensation in people with liver cirrhosis coinfected with HIV (human immunodeficiency virus) before treatment.

  • In neonates and children up to three years of age because it contains benzyl alcohol which is associated with fatal neurologic and other complications.

  • In combination with Ribavirin in pregnant females.

Warnings and Precautions:

  • Psychiatric and Central Nervous System (CNS): Central nervous system effects like depression, suicidal tendencies, and suicide have been found in some individuals undergoing Peginterferon alfa-2a therapy, even after the treatment discontinuation within the six-month follow-up period. In addition, other effects, such as aggressive behavior, bipolar disorders, mania, confusion, and changes in mental status, have been observed.

  • Individuals With Substance Use and Abuse: Individuals infected with the hepatitis C virus (HCV) and a substance use disorder like alcohol, cannabis, etc., can develop psychiatric disorders or aggravation of the already existing disorders when treated with Peginterferon alfa-2a. Therefore, if treatment with Peginterferon alfa-2a is necessary for such people, psychiatric comorbidities should be evaluated and adequately managed before beginning the therapy.

  • Pediatric: Children from three to 17 years undergoing Peginterferon alfa-2a therapy suffered from weight loss and growth inhibition.

  • Endocrine System: Deterioration of the thyroid function or worsening of the pre-existing thyroid disorders has been found during the Peginterferon alfa-2a therapy. Therefore, the TSH and T4 levels should be evaluated before therapy begins. In addition, hypoglycemia, hyperglycemia, and diabetes mellitus have been found to be associated with Peginterferon alfa-2a therapy.

  • Cardiovascular System: The use of Peginterferon alfa-2a therapy has been found to cause supraventricular arrhythmias, hypertension, congestive heart failure, chest pain, and myocardial infarction. Therefore, individuals with pre-existing cardiac abnormalities should have an electrocardiogram (ECG) before starting with the drug.

  • Liver Function: For individuals who develop hepatic decompensation during treatment, Peginterferon alfa-2a should be stopped. Increases in alanine transaminase (ALT) levels have been found in people treated with Peginterferon alfa-2a, including those with a viral response. When the increase in levels of alanine transaminase is clinically significant, the drug therapy should be discontinued.

  • Hypersensitivity Reaction: Severe hypersensitivity reactions such as urticaria, angioedema, bronchoconstriction, and anaphylaxis have been found to occur rarely during Peginterferon alfa-2a therapy.

  • Autoimmune Disease: Auto-antibodies and disorders have been found to occur during treatment with Peginterferon alfa-2a. People with a tendency to develop autoimmune disorders may be at increased risk. Vogt-Koyanagi-Harada (VKH) syndrome cases have been reported in people treated with the drug. This syndrome is an inflammatory disorder affecting the auditory system, eyes, meninges, and skin.

  • Fever or Infections: Fever is usually associated with flu-like symptoms during Peginterferon therapy. Other causes of persistent fever include bacterial, viral, and fungal infections. Severe infections like viral, bacterial, fungal, and sepsis have been found to occur during treatment with Peginterferon alfa-2a.

  • Eye Disorders: Retinopathy, including retinal hemorrhages, optic neuropathy, cotton wool spots, papilloedema, and retinal artery or vein obstruction resulting in loss of vision, has been rarely reported with Peginterferon therapy.

  • Pulmonary Changes: Pulmonary symptoms, such as dyspnoea, pulmonary infiltrates, and pneumonia, have been found to occur during treatment with Peginterferon alfa-2a.

  • Skin Disorders: Peginterferon alfa-2a has been found to cause or aggravate psoriasis and sarcoidosis.

  • HIV-HCV Co-infection: Individuals coinfected with HIV and receiving highly active antiretroviral therapy (HAART) are at an increased risk of developing lactic acidosis. Hence, precaution should be exercised while adding Peginterferon alfa-2a to HAART therapy.

For Patients:

What Is Chronic Hepatitis C Infection?

Hepatitis C is a viral infection that causes liver inflammation, leading to liver damage. The hepatitis C virus (HCV) spreads the infection through contaminated blood. As a result, the virus invades the normal body cells. Long-term infection with HCV is known as chronic hepatitis C infection. The symptoms include easy bleeding, bruising, fatigue, poor appetite, itchy skin, dark urine, etc. The treatment of hepatitis C requires weekly injections and oral medications.

Why Is Peginterferon Alfa-2a Prescribed for Chronic Hepatitis C Infection?

  1. Chronic Hepatitis C Infection - Peginterferon alfa-2a is prescribed to treat chronic hepatitis C infection (liver inflammation caused by the hepatitis c virus) in people with liver damage.

  2. ChronicHepatitis B Infection - Peginterferon alfa-2a is used in the treatment of chronic hepatitis B virus infection in people with liver damage. Peginterferon alfa-2a belongs to a group of medications known as interferons. Peginterferon works by reducing the amount of hepatitis C or B virus in the body.

Facts One Should Know About Peginterferon Alfa-2a:

How Should One Take Peginterferon Alfa-2a?

  • Peginterferon alfa-2a is available as a clear solution in a vial, a prefilled syringe, and a disposable autoinjector to be injected subcutaneously (within the fatty layer beneath the skin).

  • It should be injected on the same day once every week and around the same time.

  • Peginterferon alfa-2a should be used as directed by the physician. Do not increase or decrease the dose of the medication.

  • The doctor might start with an average dose of Peginterferon alfa-2a, which can be decreased if one develops serious side effects.

  • Stick to the brand and type of drug as prescribed by the doctor.

  • One can inject Peginterferon alfa-2a on their own or take the help of a friend or relative. Before using Peginterferon alfa-2a for the first time, one should read the manufacturer's information for the patient that comes along with it. The doctor should train one on how to take the injections.

  • Peginterferon alfa-2a can be taken anywhere on the stomach or thighs except the navel and waistline. Use a different spot for each prick. Do not prick the same spot two times in a row. Do not inject the drug where the skin is sore, red, bruised, scarred, infected, or abnormal.

  • The syringes, needles, or vials should not be reused. Please dispose of the used needles and syringes properly in a puncture-resistant container, and dispose of them after consulting with the doctor.

  • Check for any impurities by not shaking the vials, syringes, or autoinjectors containing Peginterferon alfa-2a. The solution should be sterile, clear, and free of floating particles.

  • Do not use the drug if it has expired, is discolored, is cloudy, and contains particles.

What Should One Discuss With The Doctor Before Beginning Peginterferon Alfa-2a?

Before beginning treatment with Peginterferon alfa-2a, one should inform the doctor about the following:

  • If one is allergic to Peginterferon alfa-2a, other alpha interferons, any other medications, benzyl alcohol, or polyethylene glycol (PEG).

  • If one has previously taken interferon alfa injection to treat hepatitis C infection.

  • Suppose one is taking prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products. Inform the doctor if one is taking specific medications for HIV or AIDS such as Abacavir, Didanosine, Emtricitabine, Lamivudine, Stavudine, Tenofovir, Zalcitabine, Zidovudine, Methadone, Mexiletine, Naproxen, Riluzole, Tacrine, Telbivudine, and Theophylline.

  • If one has ever had an organ transplant surgery (surgery to replace an organ in the body).

  • If one has anemia (reduced oxygen supply to different body parts) or problems with the eyes or pancreas.

  • Suppose one is pregnant or planning to conceive or breastfeeding. Peginterferon alfa-2a might harm the fetus or cause miscarriage.

  • Inform the doctor if one is having surgery, including dental surgery, about the usage of the drug.

Is Peginterferon Alfa-2a Safe?

Peginterferon alfa-2a is safe if used as prescribed and used within 48 weeks.

Is Peginterferon Alfa-2a Effective?

Peginterferon alfa-2a does not cure hepatitis C or B or prevent one from developing complications such as liver cirrhosis, liver failure, or liver cancer. The drug also does not prevent the spread of hepatitis C or B to other people.

What Side Effects Can One Expect With Peginterferon Alfa-2a?

The side effects of Peginterferon alfa-2a include the following:

  • Easy bruising, pain, redness, swelling, or irritation at the site of injection.

  • Stomach upset.

  • Insomnia.

  • Fatigue.

  • Vomiting.

  • Heartburn.

  • Dry mouth.

  • Loss of appetite.

  • Weight loss.

  • Diarrhea.

  • Dry or itchy skin.

  • Hair loss.

  • Weakness.

  • Difficulty concentrating or remembering.

  • Sweating.

  • Dizziness.

Certain side effects are serious and require immediate attention, including:

  • Blurred vision, changes in vision changes, or vision loss.

  • Lower back pain.

  • Rash.

  • Hives.

  • Swelling of the face, tongue, throat, lips, eyes, hands, feet, ankles, or legs.

  • Difficulty in swallowing.

  • Hoarseness of voice.

Can One Stop Taking Peginterferon Alfa-2a Without Your Doctor's Approval?

The medication should only be discontinued without the doctor's consent.

Are There Any Dietary Restrictions to Consider When Taking Peginterferon Alfa-2a?

One should drink plenty of fluids while on Peginterferon alfa-2a therapy.

How Should One Store Peginterferon Alfa-2a?

The medication should be kept in the container, tightly closed, and out of reach of kids. It can be stored in the refrigerator but not frozen. However, Peginterferon alfa-2a should not be left outside the refrigerator for more than a day. In addition, Peginterferon alfa-2a should be kept away from light.

How Should One Dispose of Peginterferon Alfa-2a?

Unused or expired medicines should be disposed of in specific ways so that pets, kids, and others cannot consume them. However, it should not be flushed down the toilet. Instead, the medication should be disposed of through a medication take-back program in the community.

What To Do in Case of Overdose?

In case of an overdose, the poison control team should be informed as soon as possible. In case the victim has collapsed, had a seizure, has trouble breathing, or is unconscious, emergency services should be contacted immediately.

For Doctors:

Indications - Peginterferon alfa-2a is indicated to treat the following:

  1. Chronic Hepatitis C - Peginterferon alfa-2a is used in the treatment of chronic hepatitis C along with other antiviral drugs in individuals over five years of age with compensated liver disease. It can also be used as a monotherapy in people with intolerance to other antiviral therapies.

  2. Chronic Hepatitis B - Peginterferon alfa-2a is also used for adult patients with HBeAg positive and negative chronic hepatitis B infection who have compensated liver disease.

What Is the Pharmacology of Peginterferon Alfa-2a?


Peginterferon alfa-2a is a covalent combination of recombinant alpha-2a interferon with a single-branched bis-monomethoxy polyethylene glycol (PEG) chain. The PEG component is linked at a single place of the interferon alfa through a stable amide bond to lysine. Peginterferon alfa-2a has a molecular weight of 60,000 daltons. Recombinant DNA technology gives rise to Interferon alfa-2a.


1. Active Ingredients- Peginterferon alfa-2a.

2. Inactive Ingredients:

  • Acetic acid.

  • Benzyl alcohol.

  • Polysorbate.

  • Sodium acetate trihydrate.

  • Sodium chloride.

Clinical Pharmacology:

Mechanism of Action:

The mechanism of action of Peginterferon alfa-2a is derived from its recombinant human interferon α-2a component. Peginterferon α-2a binds to the human type one interferon receptor, leading to dimerization. This dimerization activates various intracellular signal transduction pathways that were mediated by the Janus kinases-signal transducer and activator of the transcription proteins (JAK-STAT) pathway. Peginterferon α-2a has multiple biological effects on the body.


Peginterferon alfa-2a leads to the production of proteins like serum neopterin and 2', 5’-oligoadenylate synthetase.


  • Mean Cmax- 14.2 µg/L.

  • Median Tmax- 72 to 96 hours after a dose.

[Cmax- Maximum concentration achieved by a drug in the blood, cerebrospinal fluid, or target organ after administration of a dose]

[Tmax- Time taken for a drug to reach maximum concentration after administration of a dose]

Pharmacokinetic Changes

The higher serum concentrations and area under the curve increased in a non-linear dose-related manner after administering 90 to 270 mcg of Peginterferon alfa-2a.

A. Distribution: Peginterferon alfa -2a shows a restricted distribution in people with chronic hepatitis C, with the maximum concentrations found in the liver, where the drug is most effective. The amount of radioactive Peginterferon alfa -2a are highest in the liver and kidney 14 days after the single intravenous dose.

B. Metabolism: Peginterferon alfa-2a primarily undergoes hepatic metabolism and inhibits CYP1A2.

C. Excretion: The total radioactive dose of Peginterferon alfa-2a excreted in the urine and feces is 51 percent and 9.6 percent, respectively.

D. Elimination: Both the liver and kidney eliminate Peginterferon-alfa-2a. Due to its large size and branched nature, the renal clearance of Peginterferon alfa-2a is reduced compared to that of a standard interferon-alfa, thus prolonging liver exposure to the pegylated interferon. The metabolic products of Peginterferon alfa-2a are eliminated through the kidneys.

Special Considerations:

  • Pregnancy - Peginterferon alfa-2a should be used during pregnancy only if the benefit accounts for the potential risk to the fetus.

  • Breast Feeding - It is unknown whether Peginterferon alfa-2a is excreted in human milk. Due to the side effects of Peginterferon alfa-2a in infants, a decision must be made whether one should discontinue breastfeeding or use Peginterferon alfa-2a.

  • Pediatric Usage - The efficacy of Peginterferon alfa-2a in kids below five has not been established. The benzyl alcohol in Peginterferon alfa-2a has been found to cause neurological and other complications in kids.

  • Elderly - The side-effects of Peginterferon alfa-2a, such as cardiac, central nervous system, and systemic effects, can affect the elderly more, so precaution should be taken in administering the drug.

  • Hepatic Impairment - Individuals with chronic hepatitis C with liver cirrhosis may be at an increased risk of hepatic decompensation and death when treated with Peginterferon alfa-2a.

  • Renal Impairment - Individuals with renal impairment should be monitored for abnormalities such as decreased hemoglobin levels and side effects and should undergo proper creatinine clearance. Peginterferon alfa-2a therapy should be stopped in Individuals with significant severe abnormalities.

  • Organ Transplant - The safety of Peginterferon alfa-2a treatment has not been established in people with transplantations. Liver and renal transplantation rejections have been reported with Peginterferon alfa-2a therapy.

Drug Interactions:

  • Acyclovir - The metabolism of Acyclovir can be reduced when combined with Peginterferon alfa-2a.

  • Acetaminophen - The metabolism of Acetaminophen can be reduced when combined with Peginterferon alfa-2a.

  • Baricitinib - The severity of side effects can increase when Peginterferon alfa-2a is combined with Baricitinib.

  • Carvedilol - The metabolism of Carvedilol can be decreased if combined with Peginterferon alfa-2a.

What Have Clinical Trials Shown Concerning Peginterferon Alfa-2a?

Chronic Hepatitis C Studies 1, 2, and 3: Peginterferon Alfa-2a Monotherapy:

The safety and effectiveness of Peginterferon alfa-2a for treating chronic hepatitis C virus infection were evaluated in three randomized, open-label, active-controlled clinical trials. The participants were adults, had compensated liver disease, hepatitis C virus (HCV), liver biopsy diagnosis of chronic hepatitis, and had not been treated with interferon. The participants got subcutaneous injections for 48 weeks and were followed for an additional 24 weeks to ascertain the durability of the response.


The result showed a reduction in inflammation in the participants in all the treatment groups.

The response rates to studies 1, 2, and 3 to Peginterferon alfa-2a were 23 percent among the participants with viral genotype 1 and 48 percent among participants with other viral genotypes. The treatment response rates were similar in both men and women.

Patient Counseling Information:

Administration Instructions:

  • The individuals should be advised to take the prescribed dose of Peginterferon alfa-2a at the same time and day each week.

  • If a dose is missed, then take the dose as soon as possible on remembering. In case the person remembers after two days, they should be advised to consult their physician.

  • Individuals should consult their doctor if the entire dose is not received due to leakage etc.

  • Individuals should be appropriately trained for self-injection, including a proper review of the Peginterferon alfa-2a medication guide and instructions for the use of autoinjector.

  • Individuals should be advised to bring the vial, prefilled syringe, or autoinjector to room temperature and for condensation of water on the prefilled syringe or autoinjector to disappear before use.

  • Categorically, the following instructions should be given:

  1. Vial - The refrigerated vial should be warmed by slowly rolling in the palms of the hands for one minute.

  2. Prefilled Syringe - The syringes should be made to lay on a flat, clean surface and wait for a few minutes until it reaches room temperature. If condensed water appears on the outside of the syringe, wait until it disappears.

  3. Disposable Autoinjector - Place the autoinjector on a clean flat surface without removing the cap. The autoinjector should come to room temperature. It should not be warmed in any other way. The vial, prefilled syringe, or autoinjector should not be shaken, as foaming may occur. A different place on the thigh or abdomen should be chosen each time for the injection.

Complications or Side Effects:

The following side-effects observed with Peginterferon alfa-2a:

  • Delay in the growth of the kids.

  • Depression.

  • Difficulty in breathing.

  • Fever with chills.

  • Hoarseness of voice.

  • Irritability.

  • Anxiety.

  • Black and tarry stools.

  • Blood in the urine or stools.

  • Dysentery.

  • Cloudy urine.

  • Cough.

  • Lower back or side pain.

  • Mood swings.

  • Nausea.

  • Painful urination.

  • Pale skin.

  • Reddish spots on the skin.

  • Stomach pain.

  • Feeling of tightness in the chest.

  • Insomnia.

  • Easy bleeding or bruising.

  • Unusual fatigue.

  • Vomiting.

Less common side effects include the following:

  • Changes in the menstrual cycle.

  • Constipation.

  • Dizziness.

  • Dry hair and skin.

  • Sensitivity to cold.

  • Weight gain.

Source Article IclonSourcesSource Article Arrow
Dr. Muhammad Zohaib Siddiq
Dr. Muhammad Zohaib Siddiq



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