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Peginterferon Beta-1a

Class: Immunomodulatory Agents
Chemical Name: 1-Ether with N-(3-hydroxy-2-methylpropyl)interferon β-1a (human) α-methyl-ω-hydroxy-poly(oxy-1,2-ethanediyl)
Molecular Formula: C913H1417N246O256PS7 [C2H4O]n
CAS Number: 1211327-92-2
Brands: Plegridy

Medically reviewed by on Nov 8, 2021. Written by ASHP.


A covalent conjugate of interferon beta-1a (recombinant DNA origin) and polyethylene glycol (PEG). Interferon beta-1a is an immunomodulatory agent.

Uses for Peginterferon Beta-1a

Multiple Sclerosis (MS)

Management of relapsing forms of MS (e.g., relapsing-remitting MS [RRMS]).

Peginterferon beta-1a is one of several disease-modifying therapies used in the management of RRMS. Although not curative, these therapies have all been shown to modify several measures of disease activity, including relapse rates, new or enhancing magnetic resonance imaging (MRI) lesions, and disability progression.

The American Academy of Neurology (AAN) recommends that disease-modifying therapy be offered to patients with relapsing forms of MS who have had recent relapses and/or MRI activity. Clinicians should consider adverse effects, tolerability, method of administration, safety, efficacy, and cost of the drugs in addition to patient preferences when selecting an appropriate therapy.

Peginterferon Beta-1a Dosage and Administration


  • To minimize risk of flu-like symptoms, may administer prophylactic or concurrent analgesics and/or antipyretics.


Administer by sub-Q injection only.

Sub-Q Administration

Administer by sub-Q injection every 14 days into abdomen, back of upper arm, or thigh. Rotate injection sites. (See Injection Site Reactions under Cautions.)

Commercially available as a single-dose prefilled injection pen or syringe. Instruct patients on proper techniques for self-administration. (See Advice to Patients.)

Prior to administration, allow prefilled injection pens and syringes to reach room temperature (about 30 minutes).

For single-use only; discard after use.



Multiple Sclerosis

Gradually titrate to recommended dosage of 125 mcg every 14 days according to schedule in Table 1.

Table 1. Peginterferon Beta-1a Dosage Titration Schedule1



1 (first day of therapy)

63 mcg

15 (14 days later)

94 mcg

29 and every 14 days thereafter

125 mcg

The Plegridy or Plegridy Pen Starter Pack, which contains a 63 mcg prefilled injection pen or syringe, and a 94 mcg prefilled injection pen or syringe, is designed to be used during dosage titration.

Special Populations

Hepatic Impairment

No specific dosage recommendations.

Renal Impairment

Manufacturer makes no specific dosage recommendations; results of a pharmacokinetic study suggest dosage adjustment not required.

Geriatric Patients

No specific dosage recommendations.

Other Special Populations

Dosage adjustments based on body weight, gender, or age not required.

Cautions for Peginterferon Beta-1a


  • Known hypersensitivity to natural or recombinant interferon beta or peginterferon, or any other ingredient in the formulation.



Possible elevations in hepatic aminotransferase concentrations (ALT and AST) and hepatic injury.

Hepatitis, autoimmune hepatitis, and rare cases of hepatic failure reported with interferon beta therapy.

Monitor patients for hepatic injury. (See Advice to Patients.)

Depression and Suicide

Depression, suicidal ideation, and suicide attempts possible. If depression or other serious psychiatric symptoms occur, consider discontinuing therapy.


Possible seizures; use with caution in patients with preexisting seizure disorders.

Injection Site Reactions

Local injection site reactions (i.e., erythema, pain, pruritus, edema) are common following sub-Q administration; occurred in about 66% of patients in clinical studies. More severe injection site reactions, including necrosis, also reported.

Whether to discontinue therapy following a single site of necrosis depends on extent of necrosis. If therapy is continued, avoid injections near affected site until lesion has fully healed. If multiple lesions occur, discontinue drug until healing occurs.

Cardiovascular Effects

Possible congestive heart failure and cardiomyopathy; monitor patients with substantial cardiac disease for worsening of their condition during therapy.

Hematologic Effects

Decreased peripheral blood cell counts in all cell lines, including rare pancytopenia and thrombocytopenia, reported with interferon beta therapy.

Monitor CBCs, including differential and platelet counts, during therapy. In addition, monitor patients for infections, bleeding, and symptoms of anemia.

Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA), including sometimes fatal thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, reported with interferon beta therapy.

If clinical manifestations and/or laboratory findings consistent with TMA occur, discontinue therapy and manage patient as clinically indicated.

Autoimmune Diseases

Autoimmune diseases, including idiopathic thrombocytopenic purpura (ITP), hyperthyroidism, hypothyroidism, and autoimmune hepatitis, reported with interferon beta therapy.

If a new autoimmune disorder develops, consider discontinuing therapy.


Possible development of neutralizing antibodies to peginterferon beta-1a or PEG. Presence of anti-PEG antibodies does not appear to affect overall exposure or pharmacodynamic response to the drug.

Sensitivity Reactions


Anaphylaxis and other serious allergic reactions (e.g., angioedema, urticaria) reported rarely.

Discontinue therapy if a serious allergic reaction occurs. (See Contraindications under Cautions.)

Specific Populations


Category C.

No adequate and well-controlled studies in pregnant women; use during pregnancy only when potential benefits justify possible risks to fetus.

Animal reproduction studies not conducted to date with peginterferon beta-1a; however, studies using nonconjugated interferon beta in pregnant monkeys demonstrated some abortifacient activity, but no evidence of teratogenic or other adverse fetal effects.

Pregnancy registry has been established to monitor pregnancy outcomes in women exposed to peginterferon beta-1a during pregnancy. Encourage patients to enroll by calling 866-810-1462 or visiting


Not known whether peginterferon beta-1a is distributed into human milk. Use with caution in nursing women.

Pediatric Use

Safety and efficacy not established in pediatric patients.

Geriatric Use

Safety and efficacy not established in geriatric patients.

Renal Impairment

Because of possibility of increased drug exposure, monitor patients with severe renal impairment for adverse effects. (See Absorption: Special Populations, under Pharmacokinetics.)

Systemic exposure not affected in patients with end-stage renal disease undergoing hemodialysis.

Common Adverse Effects

Injection site erythema, flu-like symptoms, pyrexia, headache, myalgia, chills, injection site pain, asthenia, injection site pruritus, arthralgia.

Interactions for Peginterferon Beta-1a

No formal drug interaction studies to date.

Peginterferon Beta-1a Pharmacokinetics



Peak plasma concentrations occur 1–1.5 days following sub-Q administration.

Special Populations

In patients with mild, moderate, or severe renal impairment, AUC increased by 30, 40, or 53%, respectively.

Body weight, gender, or age does not appear to affect pharmacokinetics.



Not known whether peginterferon beta-1a is distributed into milk.



Not extensively metabolized in the liver.

Elimination Route

Principally eliminated by renal excretion.


Approximately 78 hours in patients with MS.

Special Populations

Hemodialysis removes approximately 24% of a dose.





Prefilled injection pens and syringes: 2–8°C in original carton to protect from light; do not freeze.

May be stored at 2–25°C for up to 30 days; do not freeze. May be moved to and from refrigeration if necessary; however, total combined time out of refrigeration within temperature range of 2–25°C should not exceed 30 days.


  • Biosynthetic (recombinant DNA origin) preparation of human interferon beta-1a covalently bound to PEG.

  • Interferon beta-1a portion is identical to commercially available nonconjugated interferon beta-1a (Avonex). As a result of PEG conjugation, clearance is reduced, systemic exposure is increased, and plasma half-life is prolonged, allowing for less frequent dosing compared with nonconjugated interferon.

  • Mechanism of action in the treatment of MS not fully elucidated; however, a variety of immunomodulatory effects have been described with interferon beta-1a.

Advice to Patients

  • Importance of patients reading the manufacturer's patient information (medication guide) and instructions for use before initiating treatment and each time the prescription is refilled.

  • Importance of taking peginterferon beta-1a exactly as prescribed. Advise patients not to change their dosage or administration schedule without consulting their clinician.

  • Importance of instructing patients regarding proper methods of preparation and self injection of peginterferon beta-1a, including the use of aseptic technique. Importance of providing instructions on the appropriate use, storage, and disposal of injection pens and needles.

  • Risk of hepatotoxicity; importance of advising patients to immediately inform their clinician if they experience any symptoms of liver injury (e.g., jaundice, nausea, loss of appetite, fatigue, unusual bleeding, confusion, somnolence, dark-colored urine, pale stools).

  • Risk of developing depression and suicidal ideation. Importance of patients immediately notifying their clinician if symptoms of depression or suicidal ideation occur.

  • Risk of seizures. Importance of patients immediately informing their clinician if a seizure occurs during therapy.

  • Risk of hypersensitivity reactions, including anaphylaxis. Importance of advising patients to seek immediate medical attention if any symptoms of hypersensitivity occur.

  • Risk of injection site reactions, including necrosis. Importance of patients immediately informing their clinician if any blue-black discoloration, swelling, or fluid drainage occurs in conjunction with skin breakage at the injection site.

  • Importance of informing patients that worsening of heart disease has occurred with interferon beta-1a therapy. Importance of informing patients of the symptoms of worsening heart failure and to immediately report any such symptoms to their clinician.

  • Importance of informing patients that flu-like symptoms (e.g., headache, muscle and joint aches, fever, chills, fatigue) are common following initiation of therapy with peginterferon beta-1a, and that concurrent administration of analgesics and/or antipyretics may minimize these symptoms.

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed. Encourage patients to enroll in the Plegridy pregnancy registry if they become pregnant while taking the drug.

  • Importance of patients informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses (e.g., liver disease, psychiatric disorders, seizures).

  • Importance of informing patients of other important precautionary information. (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Peginterferon Beta-1a


Dosage Forms


Brand Names



Injection, for subcutaneous use

125 mcg/0.5 mL

Plegridy (available as single-dose prefilled syringes)


Plegridy Pen (available as single-dose prefilled pens)


Kit, injection, for subcutaneous use

1 syringe, 63 mcg/0.5 mL

1 syringe, 94 mcg/0.5 mL

Plegridy Starter Pack (available as single-dose prefilled syringes)


1 injection pen, 63 mcg/0.5 mL

1 injection pen, 94 mcg/0.5 mL

Plegridy Pen Starter Pack (available as single-dose prefilled pens)


AHFS DI Essentials™. © Copyright 2022, Selected Revisions November 18, 2019. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

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