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Plegridy (peginterferon beta-1a)

Reviewed by: HU Medical Review Board | Last reviewed: April 2023

Plegridy® (peginterferon beta-1a) is approved to treat relapsing forms of multiple sclerosis (MS) in adults, including:1

  • Clinically isolated syndrome (CIS)
  • Relapsing-remitting MS
  • Active secondary progressive MS

Plegridy is a disease-modifying drug (DMD). It is a form of peginterferon beta-1a that is given by injection under the skin (subcutaneous) or into the muscle (intramuscular). Plegridy is intended to slow the build-up of disabilities and reduce the incidence of relapses in people with MS.1

What are the ingredients in Plegridy?

The active ingredient in Plegridy is peginterferon beta-1a.1

How does Plegridy work?

The way Plegridy works is not well understood. It is an interferon, which helps to control immune system activity. It is thought to act by reducing inflammation and the immune response that attacks myelin.1

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What are the possible side effects of Plegridy?

Many clinical trials evaluated the safety and efficacy of Plegridy. The most common side effects of Plegridy include:1

  • Injection site reactions
  • Flu-like symptoms, such as fever and chills
  • Headache
  • Muscle and joint aches
  • Chills
  • Muscle weakness
  • Joint pain

Plegridy may also cause serious side effects, including:1

  • Liver problems or worsening of liver problems, such as liver failure and death
  • Depression, thoughts of self-harm, irritability, and anxiety
  • Allergic reactions, such as itching, trouble breathing, feeling faint, hives, and swelling of the face, eyes, lips, tongue, or throat
  • Injection site reactions, such as redness, pain, itching, and swelling at the injection site
  • Heart problems, such as heart failure, chest pain, heart attack, and abnormal heartbeat
  • Blood problems and changes in blood tests, such as decreased white blood cell and platelet counts
  • Thrombotic microangiopathy (TMA), a condition that involves injury to the smallest blood vessels in your body
  • Autoimmune diseases, such as thyroid gland problems, autoimmune hepatitis, and problems with easy bleeding or bruising
  • Seizures, including those in people who have never had seizures before

Contact your doctor right away if you have any symptoms of serious side effects.1

These are not all the possible side effects of Plegridy. Talk to your doctor about what to expect when taking Plegridy. You also should call your doctor if you have any changes that concern you when taking Plegridy.

Things to know about Plegridy

Before starting Plegridy, tell your doctor if you:1

  • Are being treated for mental illness or have a history of mental illness, including depression and thoughts of self-harm
  • Have a history of liver problems
  • Have a history of low blood cell counts
  • Have a history of bleeding problems
  • Have a history of seizures
  • Have a history of thyroid problems
  • Have a history of autoimmune disease
  • Have an allergy to rubber or latex

There is not enough data to know if Plegridy is safe to take while pregnant or breastfeeding. Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding before starting Plegridy.1

Before beginning treatment for MS, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Plegridy.