Health Guide

Peginterferon Beta-1a (By injection)

Peginterferon Beta-1a (peg-in-ter-FEER-on BAY-ta-1-a)

Treats multiple sclerosis.

Brand Name(s):

Plegridy, Plegridy Pen, Plegridy Pen Starter Pack, Plegridy Starter Pack

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to peginterferon beta-1a or interferon.

How to Use This Medicine:


  • Your doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot under your skin.
  • This medicine should come with a Medication Guide. Ask your pharmacist for a copy if you do not have one.
  • A nurse or other health provider will give you this medicine.
  • You may be taught how to give your medicine at home. Make sure you understand all instructions before giving yourself an injection. Do not use more medicine or use it more often than your doctor tells you to.
  • You will be shown the body areas where this shot can be given. Use a different body area each time you give yourself a shot. Keep track of where you give each shot to make sure you rotate body areas. Do not inject into an area of the body where the skin is irritated, red, bruised, infected, or scarred. Most people will inject the medicine into the abdomen, back of the upper arm, or thigh.
  • Check the injection site after 2 hours for redness, swelling, and tenderness.
  • You may also receive medicine to help prevent flu-like symptoms.
  • Missed dose: You must use this medicine on a fixed schedule. Call your doctor or pharmacist if you miss a dose.
  • Keep this medicine in the refrigerator if you store it at home. Do not freeze. If you do not have refrigeration, you may keep it for up to 30 days at room temperature, away from heat and direct light. Allow the prefilled pen or syringe to warm to room temperature for 30 minutes before injection. Do not heat in a microwave oven or in hot water.
  • Each prefilled pen or syringe should be used only one time. Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, bleeding problems, heart disease, heart failure, thyroid problems, or any kind of autoimmune disease. Tell your doctor if you have a history of depression, thoughts of suicide, or seizures.
  • This medicine may cause the following problems:
    • Liver problems
    • Depression or suicidal thoughts
    • Congestive heart failure
    • Injection site reactions
  • This medicine may make you bleed, bruise, or get infections more easily. Take precautions to prevent illness and injury. Wash your hands often.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes
  • Depression, thoughts of hurting yourself or others
  • Fever, chills, cough, sore throat, and body aches that does not go away
  • Seizures
  • Severe or ongoing skin problem where the shot was given
  • Swelling in your hands, ankles, or feet
  • Unusual bleeding, bruising, or weakness

If you notice these less serious side effects, talk with your doctor:

  • Headache
  • Joint or muscle pain
  • Pain, burning, redness, swelling, or blue or black skin where the shot was given
  • Tiredness

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites.

All rights reserved