Key takeaways

  • Avonex is typically prescribed as a long-term treatment for relapsing forms of multiple sclerosis (MS). The standard dosage is 30 micrograms (mcg) injected into the upper outer thigh muscle once per week.
  • To minimize flu-like symptoms when starting Avonex, doctors may initiate treatment with a lower dose, gradually increasing it weekly until the 30 mcg maintenance dose is reached.
  • If you miss a dose of Avonex, inject it as soon as you remember, unless it is almost time for your next scheduled dose. It’s important to not exceed the prescribed dosage of this drug.

Avonex (interferon beta-1a) is a prescription drug used in adults to treat certain types of multiple sclerosis (MS) and clinically isolated syndrome (CIS).

This section describes the usual dosages of Avonex.

What are Avonex’s forms?

Avonex comes 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 following information 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 once per week. You’ll inject the medication 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 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 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 (prefilled syringe or autoinjector pen)
  • 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. Your doctor may teach you or a caregiver how to give future injections at home.

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

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

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.

You should rotate your Avonex injection site each time you inject a dose. Do not 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 how to use the syringe.

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

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. If you experience flu-like symptoms on the day you inject your dose, your doctor may recommend taking over-the-counter drugs such as acetaminophen (Tylenol) and ibuprofen (Motrin) for pain or fever.

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

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 inject your next dose at its usual time. If you’re not sure whether you should inject 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.

Call your doctor right away if you think you’ve injected 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.

The following are answers to some commonly asked questions about Avonex’s dosage.

Is Avonex’s dosing similar to that of Rebif?

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 Rebif dosage article for more information about the dosage of this medication.

How long does it take for Avonex to start working?

Avonex starts to work after your first dose, but because of how it works, you likely won’t feel it working in your body. 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.

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.