Avonex (interferon beta-1a) is a prescription drug used in adults to treat certain types of multiple sclerosis (MS) and clinically isolated syndrome. The drug comes as a liquid solution that’s given as an injection, usually once weekly.

This section describes the usual dosages of Avonex. Keep reading to learn more.

What are Avonex’s forms?

Avonex is available as a liquid solution inside single-dose prefilled syringes and autoinjector pens. The drug is given as an injection into a muscle.

What strength does Avonex come in?

Avonex comes in one strength of 30 micrograms (mcg) in 0.5 milliliters (mL) of solution.

What are the usual dosages of Avonex?

Your doctor may start you on a low dosage and adjust it over time to reach the right amount for you.

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

Dosage for multiple sclerosis

The typical Avonex dosage for adults with relapsing forms of MS is 30 mcg taken once weekly. You’ll inject Avonex into the muscle of your upper outer thigh.

Your doctor may prescribe a lower dose when you first start Avonex treatment. This is to reduce the risk of developing flu-like symptoms (such as such as chills, fever, or muscle pain) on the day you take your dose.

For example, your doctor may prescribe a starting dose of 7.5 mcg for week 1. Then, the weekly dose will be gradually increased by increments of 7.5 mcg until you reach 30 mcg. So on week 2, you’ll inject 15 mcg. On week 3, you‘ll inject 22.5 mcg.

On week 4, you’ll inject your first dose of 30 mcg. A once-weekly injection of 30 mcg is the recommended maintenance (long-term) dosage of Avonex.

Is Avonex used long term?

Yes, Avonex is typically used as a long-term treatment. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely use it long term.

The dosage of Avonex you’re prescribed may depend on several factors. These include:

  • the type and severity of the condition you’re using the drug to treat
  • your age
  • the form of Avonex you’re using
  • other conditions you may have, such as problems with your heart, thyroid, or blood count

Avonex is given as an injection into the muscle of your upper outer thigh. You’ll receive your first dose at your doctor’s office. After that, your doctor may teach you or a caregiver how to give the injections at home.

You should store Avonex in the refrigerator. If a refrigerator isn’t available (such as when traveling), Avonex may be stored at room temperature (up to 77°F or 25°C) for up to 7 days. You should not freeze Avonex.

Keep Avonex in its original packaging to protect it from light. Be sure to use a new device for each injection.

When you’re ready to inject your dose, take Avonex out of the refrigerator. Place it on the counter for 30 minutes to bring it to room temperature. You should not use other methods to warm Avonex, such as hot water.

For each dose, you should rotate the area of skin where you’re giving the injection. Don’t inject into an area that looks irritated or injured. Wipe the area you‘ll inject into with an alcohol wipe. And be sure to wash your hands before you start the injection process.

The manufacturer of Avonex provides step-by-step instructions on how to use the autoinjector pen and the syringe.

After using either the autoinjector or syringe, it should be placed in a dedicated sharps container for disposal.

If you experience flu-like symptoms on the day you inject your dose, your doctor may recommend you take over-the-counter medications for pain or fever. These medications may include acetaminophen (Tylenol) and diphenhydramine (Benadryl). You may be more likely to experience flu-like symptoms when you first start Avonex treatment. Over time, these symptoms may lessen or go away completely.

For information on the expiration, storage, and disposal of Avonex, 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 Avonex, take it as soon as you remember. But if it’s almost time for your next dose, you should skip the missed dose and take your next dose at its usual time. If you’re not sure whether you should take a missed dose, talk with your doctor or pharmacist.

If you need help remembering to take your dose of Avonex on time, try using a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.

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

What to do in case you take too much Avonex

Call your doctor right away if you think you’ve taken too much Avonex. 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 Avonex’s dosage.

Is Avonex’s dosage similar to that of Rebif?

Avonex and Rebif come in the same forms and share an active ingredient,* but they have some differences in dosage and administration.

Avonex and Rebif both contain interferon beta-1a as their active ingredient. They’re both available as single-dose prefilled syringes and autoinjector pens. But Avonex is injected into the muscle of your outer upper thigh, while Rebif is injected under the skin of your thigh, hip, abdomen, or upper arm.

Avonex is usually injected once weekly. Rebif is usually injected three times per week.

Your doctor may choose to start your Avonex or Rebif treatment at a low dose and slowly increase it over time. The dose in mcg for each drug differs. Your doctor will prescribe the drug and the dosage that’s right for you.

To learn more about how these drugs compare, talk with your doctor. You can also see this article for more details on Rebif’s dosage.

* An active ingredient is what makes a drug work.

How long does it take for Avonex to start working?

Avonex starts to work after your first dose. Because of how the drug works, you likely won’t feel it working in your body. But your doctor will monitor you during treatment to check whether the drug is working to treat your condition.

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

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

Remember, you should not change your dosage of Avonex without your doctor’s recommendation. Only take Avonex 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:

  • Could my dose be lowered if I experience bothersome side effects from Avonex?
  • Should my dosage of Avonex change if my current dosage isn’t completely managing my symptoms?
  • Can I simply stop taking Avonex, or do I have to slowly decrease my dosage before ending my treatment?

To learn more about Avonex, see this article.

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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.