Plegridy (peginterferon beta-1a) is a prescription drug used to treat certain types of multiple sclerosis. It comes as a liquid solution for injection under the skin or into a muscle. The maintenance dose is usually given every 14 days.

Plegridy is used in adults to treat some forms of multiple sclerosis (MS). They include:

Plegridy is also prescribed to treat clinically isolated syndrome, which may be (but isn’t always) the first sign of MS.

The active ingredient in Plegridy is peginterferon beta-1a. (An active ingredient is what makes a drug work.) Plegridy belongs to a group of drugs called interferon betas.

This article describes the dosages of Plegridy, as well as its strengths and how it’s used. To learn more about Plegridy, see this in-depth article.

The table below highlights the basics of Plegridy’s dosage. All doses are listed in micrograms (mcg). The dosage schedule is the same for injection under the skin or injection into a muscle.

Plegridy dosing scheduleDosage
Day 1 (first dose)63 mcg
Day 15 (second dose)94 mcg
Day 29 (third dose), then every 14 days125 mcg

Keep reading for more details about Plegridy’s dosage.

What are Plegridy’s forms?

Plegridy is available as a liquid solution in single-dose prefilled pens and single-dose prefilled syringes. The drug is given as an injection under your skin (via a pen or syringe) or an injection into a muscle (via a syringe).

What strengths does Plegridy come in?

Plegridy’s strengths vary based on whether the drug is given as an injection under the skin or into a muscle.

For injection under the skin

Plegridy is available in three strengths for injection under the skin:

  • 63 mcg/0.5 (milliliter) mL
  • 94 mcg/0.5 mL
  • 125 mcg/0.5 mL

For injection under the skin, Plegridy comes as a starter pack. It contains two prefilled pen or syringe injections:

  • a 63-mcg dose for Day 1
  • a 94-mcg dose for Day 15

For injection into a muscle

For injection into a muscle, Plegridy comes in one strength of 125 mcg/0.5 mL in a single-dose prefilled syringe.

Plegridy is available with a kit that’s used for the first two injections into a muscle. The kit has two clips that attach to the prefilled syringe. These clips limit the amount of the drug you’ll receive in your first two doses. You’ll use the yellow clip for the first dose and the purple clip for the second dose. It’s important to use these clips so that you inject the correct strength of Plegridy for the first two doses.

Your doctor will prescribe the dosage form that’s right for you.

What are the usual dosages of Plegridy?

Your doctor will start you on a low dose of Plegridy and adjust it over time to reach the right amount for you. This is called titration. It allows your doctor to see how you respond to treatment and lowers your risk of side effects from the drug.

The information below describes dosages that are commonly used or recommended. But be sure to use the dosage your doctor prescribes. They’ll determine the best dosage to fit your needs.

Dosage for MS

The typical Plegridy dosage for adults with MS is as follows:

  • Day 1: 63-mcg injection
  • Day 15: 94-mcg injection
  • Day 29: 125-mcg injection (first full dose)

After this, your dose is 125 mcg injected every 14 days.

The dosage schedule is the same for Plegridy given as an injection under the skin or into a muscle. Your doctor will explain both options and show you how to inject your doses.

Your doctor may recommend certain medications, such as fever or pain reducers, to lower your risk of flu-like symptoms from Plegridy. They may suggest taking these drugs just before injecting Plegridy.

Is Plegridy used long term?

Yes, Plegridy is usually a long-term treatment. If you and your doctor determine it’s safe and effective for your condition, you’ll likely use it long term. Talk with them if you have questions about how long you’ll need Plegridy treatment.

Plegridy comes as a liquid solution given as an injection under your skin or into a muscle. The solution comes in single-use prefilled pens and syringes.

Your doctor or another healthcare professional will show you how to give yourself injections at home. You can also find instructions on the manufacturer’s site or view the “Instructions for use” starting on page 23 of Plegridy’s prescribing information.

Plegridy injections that are given under the skin may be given in the abdomen, thigh, and back of the upper arm.

Plegridy injections into a muscle should be alternated between the left and right thigh muscles.

It’s important to rotate the site where you inject Plegridy to help prevent skin irritation or a skin infection.

Your doctor may recommend taking certain medication before each injection to lower the risk of flu-like symptoms from Plegridy. For example, they may suggest a fever reducer such as acetaminophen (Tylenol).

For information on the expiration, storage, and disposal of Plegridy, talk with your doctor or pharmacist.

Accessible drug containers and labels

Some pharmacies provide medication labels that:

  • have large print
  • use braille
  • feature a code you can scan with a smartphone to change the text to audio

Your doctor or pharmacist may be able to recommend pharmacies that offer these accessibility features if your current pharmacy doesn’t.

If you miss a dose of Plegridy, inject it as soon as you remember. You’ll then need to start your 14-day cycle over from that date. If you have questions about injecting a missed dose, talk with your doctor.

If you need help remembering to inject your dose of Plegridy on time, try using a medication reminder. This can include downloading a reminder app on your phone.

Do not inject more Plegridy than your doctor prescribes, as this can lead to harmful effects.

What to do in case you inject too much Plegridy

Call your doctor right away if you think you’ve injected too much Plegridy. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

Below are answers to some commonly asked questions about Plegridy’s dosage.

Is Plegridy’s dosage similar to that of Gilenya?

No, it’s not. Plegridy (peginterferon beta-1a) and Gilenya (fingolimod) are both used to treat types of MS. But the form they come in, how they work, and their dosages are different.

Plegridy comes as a liquid solution in single-dose prefilled pens or syringes. It’s injected under the skin or into a muscle. The maintenance dose is one 125-mcg injection every 14 days. Plegridy belongs to a group of drugs called interferon betas. It’s only approved for use in adults.

Gilenya comes as an oral capsule available in two strengths: 0.25 milligrams (mg) and 0.5 mg. Dosage is based on body weight and the drug is typically taken once per day. Gilenya belongs to a group of drugs called sphingosine 1-phosphate receptor modulators. It’s approved for use in adults and certain children.

Your doctor will prescribe the drug and dosage that’s right for you. Talk with them to learn more about how these drugs compare.

How long does it take for Plegridy to start working?

Plegridy starts to work after your first dose. But it may take several weeks before you notice a decrease in MS symptoms. Your doctor will monitor you during treatment to check whether the drug is working to manage your condition.

If you have other questions about what to expect from Plegridy treatment, talk with your doctor.

The sections above describe the usual dosages provided by Plegridy’s manufacturer. If your doctor recommends this drug, they’ll prescribe the dosage that’s right for you.

You should not change your dosage of Plegridy without your doctor’s recommendation. Only inject this drug exactly as prescribed. Talk with your doctor if you have questions or concerns about your current dosage.

Examples of questions you may want to ask your doctor include:

  • Will my dose of Plegridy need to be lowered if I have side effects?
  • Does it matter what time of day I inject my Plegridy dose?
  • How does the dosage of Plegridy compare with that of Avonex (interferon beta-1a)?

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.