Plegridy - National Multiple Sclerosis Society

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About this Medication
  • Brand Name: Plegridy™
  • Chemical Name: peginterferon beta-1a
  • Usage in MS: Disease-Modifying Agent
  • Generic Available: No

This is an injectable medication used with a a pre-filled pen (autoinjector) or pre-filled syringe.

The information in this medication sheet has been adapted from the FDA-approved prescribing information for Plegridy™ (peginterferon beta-1a).


Pegylated interferon beta-1a is a “pegylated" form of interferon, meaning that polyethylene glycol is attached to the interferon molecules to allow them to maintain their biologic effects in the body for longer periods of time. Because the biologic effects in the body last longer, dosing can occur at less frequent intervals.

This medication is manufactured by a biotechnological process from one of the naturally-occurring interferons (a type of protein). It is made up of exactly the same amino acids (major components of proteins) as the interferon beta found in the human body.

Plegridy was shown after one year of a two-year, phase III clinical trial with 1500 people with relapsing MS to reduce the relapse rate significantly more than placebo. In addition, new lesions on MRI scans and the risk of disability progression were reduced significantly more than in the placebo group. Plegridy was not compared in this study to other interferon medications or other MS therapies.

Approval by the U.S. Food and Drug Administration (FDA):

Plegridy is approved by the FDA for the treatment of patients with relapsing forms of MS.

Proper Usage

  • The recommended 125 microgram dose of Plegridy is given every 14 days by subcutaneous (under the skin) injection, using a pre-filled pen (autoinjector) or pre-filled syringe. You will be instructed in the correct technique for administering these injections, most often in the abdomen, back of the upper arm, and thigh.
  • A starter pack is available to help you begin the medication gradually – with 63 micrograms on Day 1, 94 micrograms on Day 15, and 125 micrograms on Day 29, followed by 125 micrograms every 14 days thereafter.
  • Pens and syringes should be stored in the original carton in the refrigerator until you are almost ready to inject. Allow the medication to come to room temperature (about 30 minutes) before you inject. If refrigeration is not available, the medication can be stored for up to 30 days at room temperature, away from direct sunlight.
  • Rotate areas of injection with each dose in order to minimize the likelihood of injection site reactions.
  • Do not inject into an area of the body where the skin is irritated, bruised, infected or scarred.
  • Check the injection site after two hours for redness, swelling and tenderness, and contact your healthcare professional if you have a skin reaction that does not clear up in a few days.
  • Taking an over-the-counter pain reliever or fever reducer may help to manage the flu-like symptoms (headache, muscle and joint aches, fever, chills, tiredness) that are common with this medication.

Warnings and Precautions

Plegridy can cause liver problems or worsening of liver problems, as well as depression or suicidal thoughts. Plegridy can also cause serious allergic reactions, injection site reactions, heart problems, autoimmune diseases (for example, problems with easy bleeding or bruising, thyroid problems, autoimmune hepatitis), seizures. So before starting Plegridy, be sure to tell your physician if you have ever had any of the following medical problems:

  • Depression, anxiety, or trouble sleeping
  • Problems with your thyroid gland
  • Blood problems such as bleeding or bruising easily, anemia, low white cell count
  • Seizures
  • Heart problems
  • Liver disease (you will receive periodic blood tests during treatment to check for liver function changes

Before taking Plegridy, tell your healthcare provider if you are pregnant or planning to become pregnant. It is not known whether this medication will harm your unborn baby. In addition, tell your healthcare provider if your are breastfeeding or planning to breastfeed since it is not known whether Plegridy passes into your breast milk. If you become pregnant while taking Plegridy, contact your healthcare provider right away.

Possible Side Effects

Common side effects include flu-like symptoms (fatigue, chills, fever, muscle aches, and sweating)


Plegridy support services:
MS ActiveSource®: 

Financial Assistance Program

MS Active Source, or call 1-800-456-2255