Plegridy (peginterferon beta-1a) is a brand-name drug that’s prescribed for multiple sclerosis (MS) in adults. It comes in a single-use prefilled pen and prefilled syringe. Plegridy is typically given once every 2 weeks.

Plegridy is approved by the Food and Drug Administration (FDA) to treat the following types of MS:

Plegridy is a biologic and belongs to a drug class called interferon betas. Plegridy isn’t available in a biosimilar version.

Keep reading for specific information about the dosage of Plegridy, including its strengths and how to use the medication. For a comprehensive look at Plegridy, see this article.

Note: This article describes typical dosages for Plegridy provided by the drug’s manufacturer. When taking Plegridy, always follow the dosage prescribed by your doctor.

Read below for recommended dosages of Plegridy and other details about the drug.

Plegridy forms

Plegridy comes in a single-use prefilled pen and prefilled syringe. Plegridy can be given as a subcutaneous injection or an intramuscular injection. Your doctor or another healthcare professional may give your first Plegridy injection in their office. Then, they can show you or a caregiver how to administer Plegridy injections at home.

Plegridy strengths

Plegridy can be injected under your skin (subcutaneously) or into your muscle (intramuscularly). The drug is available in different forms based on how it’s injected. It comes in a prefilled pen and prefilled syringe for subcutaneous injection. For intramuscular injection, it’s only available in a prefilled syringe.

All forms of Plegridy come prefilled with 0.5 milliliters (mL) of solution containing the active drug. They are single-use, meaning you should dispose of each pen or syringe after one use.

Plegridy’s prefilled pen and prefilled syringe for subcutaneous injection come in three strengths:

  • 63 micrograms (mcg)
  • 94 mcg
  • 125 mcg

Plegridy’s prefilled syringe for intramuscular injection comes in one strength of 125 mcg.

Typical dosages

Typically, your doctor will start by prescribing you a low dosage. Then, they’ll adjust it over time to reach the amount that’s right for you.

The following information describes dosages that are commonly used in adults. However, be sure touse the dosage your doctor prescribes for you.

Dosage for multiple sclerosis

Doctors may prescribe Plegridy to treat certain types of MS.

If your doctor prescribes Plegridy for your MS, they’ll increase your dose every 14 days until you can receive the full dose of Plegridy.

Your first dose will likely be 63 mcg. Then, 14 days later, you’ll give yourself a dose of 94 mcg. Lastly, 14 days after your second dose, you’ll give yourself 125 mcg of Plegridy. This is the typical recommended dosage of Plegridy. If this drug is effective for your condition, you’ll continue to give yourself 125 mcg of Plegridy every 14 days.

Dosing for Plegridy is the same whether you’re using it subcutaneously or intramuscularly.

The table below shows the typical dosage schedule, including the starting dosage and maintenance dosage. Your doctor will choose a maintenance dose that suits your needs.

1163 mcg
21594 mcg
329 (and then every 14 days)125 mcg

For more information about your specific dosage, talk with your doctor.

Long-term treatment

Plegridy is meant to be used as a long-term treatment. If you and your doctor determine that Plegridy is safe and effective for you, you’ll likely use it long term.

Before you start taking Plegridy, your doctor will discuss your treatment plan with you.

The subcutaneous form of Plegridy comes in a single-use prefilled pen or prefilled syringe. With a subcutaneous injection, you’ll inject the medication under your skin.

Your doctor will give you your first dose of Plegridy. Then, they’ll show you (or your caregiver) how to do it. Make sure to inject Plegridy according to your prescribed instructions.

For subcutaneous injections, you can inject Plegridy into your abdomen, thigh, or the back of your upper arm. If you use your abdomen, do not inject Plegridy within 2 inches of your belly button.

Plegridy is also available as an intramuscular injection. In this case, the drug comes in a single-use prefilled syringe. With this type of injection, you’ll inject the medication into your muscle. Your doctor will likely give your first dose. Then, they can show you or a caregiver how to administer the medication.

You can inject the intramuscular form of Plegridy into your thigh. You should rotate between your left and right thighs to decrease the risk of injection-related side effects.

Be sure to choose a different injection site each time you inject Plegridy. And avoid areas where your skin is tender, hard, or irritated. This will reduce the risk of injection-related side effects, such as bleeding or pain at the injection site.

You’ll store Plegridy pens or syringes in the refrigerator. Plegridy pens and syringes are single use. This means they’re meant for one-time use only and cannot be reused. Be sure to discard your Plegridy pen or syringe after using it.

If you have questions about how to use Plegridy, talk with your doctor or pharmacist. There’s also a helpful video and step-by-step instructions on the manufacturer’s website.


Some pharmacies offer labels with large print, braille, or a code you scan with a smartphone to convert text to speech. If your local pharmacy doesn’t have these options, your doctor or pharmacist might be able to recommend a pharmacy that does.

If you miss a dose of Plegridy, inject the dose as soon as you remember. Then, you can take your next dose 14 days later like usual.

Do not inject two doses to make up for the missed one. If you’re not sure whether you should use a missed dose or skip it, talk with your doctor or pharmacist.

To help make sure that you don’t miss a dose, try using a medication reminder. This can include setting an alarm or putting a note where you’ll see it, such as on your bathroom mirror or bedside table. You could also download a reminder app on your phone.

It’s important that you don’t use more Plegridy than your doctor prescribes. For some medications, using more than the recommended amount may lead to harmful effects or overdose.

If you take more than the recommended amount of Plegridy

Call your doctor right away if you believe you’ve used too much Plegridy. Another option is to call America’s Poison Centers at 800-222-1222 or use its online tool. If you have severe symptoms, immediately call 911 or your local emergency number or go to the nearest emergency room.

Below are some frequently asked questions about Plegridy.

How long does it take for Plegridy to start working?

Plegridy starts to work after your first dose. But because of how the drug works, you may not feel the drug working in your body.

In addition, you won’t receive the full dose of Plegridy right away. Your doctor will start you on the lowest dose of Plegridy. Then, your dose will increase every 2 weeks until day 29 of treatment, when you’ll receive the full 125-mcg dose.

Because of this, it may take a few weeks before you notice any changes in your MS symptoms. Your doctor will monitor your condition during treatment to check whether the drug is working as expected.

Talk with your doctor if you have questions about what to expect with Plegridy treatment.

What is the recommended maximum dosage of Plegridy?

The recommended maximum dosage of Plegridy is 125 mcg every 14 days. This is the highest available dose of Plegridy. For details about Plegridy’s dosages, see the “Plegridy dosage” section above.

If you have questions or concerns about your dosage of Plegridy, talk with your doctor or pharmacist. Never adjust your dosage unless your doctor recommends doing so.

The dosages in this article are typical dosages provided by the drug’s manufacturer. If your doctor recommends Plegridy for you, they’ll prescribe the dosage that’s right for you. Always follow the dosage that your doctor prescribes.

As with any drug, never change your dosage of Plegridy without your doctor’s recommendation. If you have questions about the dosage of Plegridy that’s best for you, talk with your doctor.

Besides learning about dosage, you may want other information about Plegridy. These additional articles might be helpful:

  • More about Plegridy: For information about other aspects of Plegridy, refer to this article.
  • Drug comparison: To find out about other drugs for MS, see this page.
  • Details about MS: For details about MS, see our multiple sclerosis hub.

Disclaimer: Medical News Today 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.