Last updated on RxList: 3/4/2021
Plegridy Side Effects Center

What Is Plegridy?

Plegridy (peginterferon beta-1a) Autoinjector is an interferon beta-1a used to treat patients with relapsing forms of multiple sclerosis.

What Are Side Effects of Plegridy?

Common side effects of Plegridy Autoinjector include:

  • injection site reactions (redness, itching, pain, swelling, warmth, rash, bruising),
  • flu-like illness,
  • fever,
  • headache,
  • muscle or joint pain,
  • chills,
  • weakness,
  • nausea, and
  • vomiting

Dosage for Plegridy

The recommended dosage of Plegridy is 125 micrograms injected subcutaneously every 14 days.

What Drugs, Substances, or Supplements Interact with Plegridy?

Plegridy may interact with other drugs. Tell your doctor all medications and supplements you use.

Plegridy During Pregnancy and Breastfeeding

During pregnancy, Plegridy should be used only if prescribed. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Plegridy (peginterferon beta-1a) Autoinjector Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


What Is Multiple Sclerosis? MS Symptoms, Causes, Diagnosis See Slideshow
Plegridy Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives, itching, bumps on your skin; feeling anxious or light-headed; difficult breathing; swelling of your face, lips, tongue, or throat.

Peginterferon beta-1a can cause life-threatening blood clots in the small blood vessels inside your organs, such as your brain or kidneys. Seek medical help right away if you have symptoms of this condition, such as a fever, tiredness, decreased urination, bruising, or nosebleeds.

Call your doctor at once if you have:

  • ongoing pain, swelling, or skin changes where the injection was given;
  • a light-headed feeling, like you might pass out;
  • unusual changes in mood or behavior (feeling hopeless, anxious, nervous, irritable, or depressed);
  • thoughts about suicide or hurting yourself;
  • a seizure;
  • heart problems--swelling, rapid weight gain, feeling short of breath, rapid heartbeats, chest pain spreading to your jaw or shoulder, nausea, sweating;
  • low blood cell counts--fever, chills, tiredness, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath;
  • liver problems--nausea, loss of appetite, tiredness, confusion, easy bruising or bleeding, dark urine, clay-colored stools, or jaundice (yellowing of your skin or eyes); or
  • thyroid problems--mood swings, trouble sleeping, tiredness, hunger, diarrhea, pounding heartbeats, muscle weakness, sweating, dry skin, thinning hair, menstrual changes, weight changes, puffiness in your face, feeling more sensitive to hot or cold temperatures.

Common side effects may include:

  • pain, redness, itching, or swelling where the injection was given; or
  • flu symptoms--headache, fever, chills, tiredness, body aches.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Plegridy (Peginterferon Beta-1a Injection for Subcutaneous Use)


What kind of disease is multiple sclerosis? See Answer
Plegridy Professional Information


The following serious adverse reactions are discussed in more detail in other sections of labeling:

  • Hepatic Injury [see WARNINGS AND PRECAUTIONS]
  • Depression and Suicide [see WARNINGS AND PRECAUTIONS]
  • Anaphylaxis and Other Allergic Reactions [see WARNINGS AND PRECAUTIONS]
  • Injection Site Reactions [see WARNINGS AND PRECAUTIONS]
  • Congestive Heart Failure [see WARNINGS AND PRECAUTIONS]
  • Decreased Peripheral Blood Counts [see WARNINGS AND PRECAUTIONS]
  • Thrombotic Microangiopathy [see WARNINGS AND PRECAUTIONS]
  • Autoimmune Disorders [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of PLEGRIDY cannot be directly compared to rates in clinical trials of other drugs and may not reflect the rates observed in practice.

PLEGRIDY Via Subcutaneous Administration

In clinical studies (Study 1 and Study 2), a total of 1468 patients with relapsing multiple sclerosis received PLEGRIDY by subcutaneous injection for up to 177 weeks (41 months), with an overall exposure equivalent to 1932 person-years. A total of 1093 patients received at least 1 year, and 415 patients at least 2 years of treatment with PLEGRIDY. A total of 512 and 500 patients, respectively, received PLEGRIDY 125 micrograms every 14 days or every 28 days during the placebo-controlled phase of Study 1 (year 1). The experience in year 2 of Study 1 and in the 2-year safety extension study (Study 2) was consistent with the experience in the 1-year placebo-controlled phase of Study 1.

In the placebo-controlled phase of Study 1, the most common adverse drug reactions for PLEGRIDY 125 micrograms subcutaneously every 14 days were injection site erythema, influenza-like illness, pyrexia, headache, myalgia, chills, injection site pain, asthenia, injection site pruritus, and arthralgia (all had incidence more than 10% and at least 2% more than placebo). The most commonly reported adverse event leading to discontinuation in patients treated with PLEGRIDY 125 micrograms subcutaneously every 14 days was influenza-like illness (in less than 1% of patients).

Table 3 summarizes adverse reactions reported over 48 weeks from patients treated in the placebo-controlled phase of Study 1 who received subcutaneous PLEGRIDY 125 micrograms (n=512), or placebo (n=500), every 14 days.

Table 3: Adverse Reactions in the 48-Week Placebo-Controlled Phase of Study 1 with an Incidence 2% Higher for PLEGRIDY Than for Placebo

(N=512) %
(N=500) %
Nervous System Disorders
Gastrointestinal Disorders
Musculoskeletal and Connective Tissue Disorders
General Disorders and Administration Site Conditions
Injection site erythema627
Influenza like illness4713
Injection site pain153
Injection site pruritus131
Injection site edema30
Injection site warmth30
Injection site hematoma31
Injection site rash20
Body temperature increased63
Alanine aminotransferase increased63
Aspartate aminotransferase increased42
Gamma-glutamyl -transferase increased31
Skin and Subcutaneous Tissue Disorder

Flu-Like Symptoms

Influenza-like illness was experienced by 47% of patients receiving PLEGRIDY 125 micrograms every 14 days and 13% of patients receiving placebo. Fewer than 1% of PLEGRIDY-treated patients in Study 1 discontinued treatment due to flu-like symptoms.

Comparison Between Subcutaneous And Intramuscular Administration

An open-label, crossover study analyzed findings from 130 healthy volunteers to assess the bioequivalence of single doses of 125 micrograms of PLEGRIDY administered as a subcutaneous and intramuscular injection (Study 3).

The most commonly reported adverse reactions (with >10% incidence in either arm) across both treatment periods were chills (36% in IM vs 27% in SC), pain (22% in IM vs 14% in SC), headache (36% in IM vs 41% in SC), injection site pain (11% in IM vs 15% in SC), and injection site erythema (2% in IM vs 25% in SC). Overall, injection site reactions were reported in 14% via IM route as compared to 32% via SC route.


As with all therapeutic proteins, there is a potential for immunogenicity.

The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies in the studies described below with the incidence of antibodies in other studies or to other interferon beta-1a products may be misleading.

In Study 1, fewer than 1% of patients treated with PLEGRIDY SC every 14 days for 1 year developed neutralizing antibodies. Approximately 7% of PLEGRIDY SC-treated patients developed antibodies to the polyethylene glycol moiety.

No formal studies have been conducted with regards to immunogenicity of the intramuscular route of administration of PLEGRIDY.

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of PLEGRIDY. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Anaphylactic Reactions

In post marketing experience, serious hypersensitivity reactions, including cases of anaphylaxis, have been reported following PLEGRIDY administration [see WARNINGS AND PRECAUTIONS].

Read the entire FDA prescribing information for Plegridy (Peginterferon Beta-1a Injection for Subcutaneous Use)

© Plegridy Patient Information is supplied by Cerner Multum, Inc. and Plegridy Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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