What is Avonex?

Avonex is a medication prescribed for the treatment of relapsing forms of multiple sclerosis (MS). It contains interferon beta-1a, a protein that helps regulate the immune system and reduce inflammation in the central nervous system. Avonex is administered via intramuscular injections, typically once a week. By targeting the underlying immune system dysfunction in MS, Avonex aims to reduce the frequency and severity of relapses, delay disability progression, and improve overall quality of life for patients. However, Avonex may have potential side effects, including flu-like symptoms, injection-site reactions, and liver problems. It is important to closely follow the prescribed dosage, administration instructions, and regularly consult with a healthcare professional to monitor your response to treatment and manage any potential risks.

Avonex Pen
Interferon Beta-1A
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Interferon Beta-1A
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Avonex Prefilled Syringe
Interferon Beta-1A
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Prescription Required.

Product of Canada.

Shipped from Canada.

Prescription Required.Product of Canada.Shipped from Canada.

What is Avonex?

Avonex is a medication prescribed to help treat relapsing forms of multiple sclerosis (MS), including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease in adults. It is not known if it is safe and effective in children.

This medication belongs to a class of drugs called immunomodulators. These medications are a form of protein that is naturally made by the body’s cells to fight infections and tumors and reduce inflammation.

Avonex is not recommended:

  • If you are allergic to or have had an allergic reaction to it or any of its ingredients.
  • For children under the age of 18 years.

What are the Indications for Avonex?

Avonex is approved for the treatment of patients with relapsing forms of MS.

Avonex will not cure the disease but may decrease the frequency of flare-ups, such as balance problems, numbness, or weakness, or reduce the onset of MS. Avonex may be used alone or with other medications.

How is Avonex used?


Avonex vials, prefilled syringes, and pens should be stored in their original packaging in a refrigerator at 36-46°F (2-8°C). If no refrigerator is available, vials can be stored at 77°F (25°C) for up to 30 days, and prefilled pens and syringes for up to 7 days.

Do not expose to high temperatures and keep away from light. Do not freeze. Frozen vials or pens must be discarded.

Keep out of reach of children and pets.


Use Avonex as prescribed and follow the instructions given by your doctor. Your doctor will determine the appropriate dose and schedule based on your individual needs and medical history.

Do not change your dosage and take more than what is prescribed, or stop using it without consulting with your doctor. If you miss a dose, take it as soon as you remember, but do not inject two days in a row. Do not catch up by taking two doses at once. If you took more than prescribed, contact your doctor immediately or seek emergency medical care.

Avonex is given as a once-weekly injection at bedtime, usually into the muscle and on the same day each week.

Your healthcare provider will teach you how to use Avonex properly and where to inject yourself. Ask your healthcare provider if you don’t understand the instructions. Do not inject yourself in the same place twice in a row.

Before use, remove it from the refrigerator to warm naturally to room temperature for about 30 minutes. Do not warm with external heat sources, like hot water.

The powder form of Avonex must be mixed with a liquid before using it. It can be stored in a refrigerator, but it must be used within 6 hours.

Only prepare an injection only when you are ready to give it. Do not use it if the medicine has changed color or contains particles.

The vial, prefilled syringe, and pen should only be used once and must be thrown away after use even if there’s still medicine left inside. Place it in a puncture-proof ‘sharps’ container and dispose of it responsibly.


Avonex is available in 3 forms: a single-use prefilled syringe, a powder vial, or an autoinjector pen. All three forms contain 30 mcg of Avonex in a 0.5 mL solution.

The recommended starting dose is 30 mcg, injected into the upper, outer thigh muscle. The buttock is not a suitable injection site.

About 2 hours after your injection, check your skin around the injection site for redness, swelling, or pain. Call your doctor if you have a skin reaction that does not go away within a few days.

Side Effects

It’s important to understand that although Avonex is FDA-approved, it comes with side effects that may or may not affect you.

Before starting, you should discuss possible side effects with your doctor or pharmacist.

Common Side Effects

Not all side effects require medical attention. As your body adjusts to Avonex, side effects may go away. Tell your doctor if you experience the following symptoms, and they become severe or do not go away on their own.

  • Flu-like symptoms, like muscle aches, fever, chills, and tiredness, especially when you first start using it. Your doctor may give you other medications to help prevent these symptoms.
  • Skin irritation around the injection site
  • Stomach pain
  • Headache

Serious Side Effects

Severe adverse reactions while taking Avonex may occur. Seek emergency medical care or call 911 if you experience any of the following symptoms:

  • Blood clots: fever, tiredness, decreased urination, bruising, nosebleeds.
  • Heart problems: swelling, sudden weight gain, shortness of breath, rapid heartbeat, chest pain, nausea, sweating.
  • Liver problems:nausea, loss of appetite, tiredness, confusion, bruising, clay-colored stools, jaundice
  • Signs of infection:fever, chills, cough with mucus, bloody diarrhea, painful or burning urination
  • Thyroid problems– mood swings, trouble sleeping, tiredness, hunger, diarrhea, pounding heartbeats, muscle weakness, sweating, dry skin thinning hair, menstrual changes, weight changes, puffiness in your face, increased sensitivity to hot or cold temperatures.
  • Depression: suicidal thoughts
  • Severe allergic reaction: rash, itching, swelling, especially the face, tongue, and throat, severe dizziness, trouble breathing.
  • Other: seizure, feeling like passing out, pain, swelling, bruising, redness, oozing, or skin changes at the injection site.

The information above does not list all possible side effects. Contact your doctor or pharmacist if you experience any side effects not listed. You or your doctor may report side effects to the FDA by calling 1-800-FDA-1088.

Warnings & Precautions

Before using Avonex, tell your doctor or pharmacist:

  • If you are allergic to it or any its ingredients
  • If you are pregnant or plan to become pregnant
  • If you are breastfeeding or plan to breastfeed
  • If you suffer from any of these conditions:
    • Depression, mental illness, or suicidal thoughts
    • Liver disease
    • Bleeding problems or a blood clot
    • Low blood cell counts
    • Heart disease
    • Thyroid disorder
    • Latex allergy
    • Autoimmune disorders
    • Seizures
  • If you drink alcohol

Psychological issues

Avonex may cause mental health problems such as depression, psychosis, irritability, hallucinations, and suicidal thoughts. Contact your doctor if you experience any of these symptoms.

Liver problems

Avonex may cause liver damage and your liver health should be monitored while on Avonex.

You must also tell your doctor if you drink alcohol before you start taking Avonex.

Low blood cell counts

Avonex may cause a low blood cell count and you should go for routine blood and platelet counts tests to monitor this.

Blood vessel damage

Avonex may cause thrombotic microangiopathy, a condition in which blood clots cause damage to the body’s small blood vessels. Treatment should be stopped if you show signs of the disease like fatigue, light-headedness, and shortness of breath.

Autoimmune diseases

Avonex can cause a number of autoimmune conditions that could affect multiple organs, such as idiopathic thrombocytopenia, thyroid diseases, and autoimmune hepatitis.

Pregnant or Planning to Become Pregnant

It is not known if Avonex will harm an unborn baby. Only use if clearly needed. If you become pregnant, speak to your doctor who will determine if the benefit of using Avonex, outweighs the risk.

Breastfeeding or Planning to Breastfeed

Avonex may pass into breast milk in small amounts. Speak to your doctor about whether you should continue breastfeeding.

Interactions & Contraindications

Before using, tell your doctor or pharmacist if you take any medications, herbal supplements, vitamins, or drink alcohol.

Avonex may also interact with medications that can affect the immune system, theophylline (used to prevent wheezing and shortness of breath), vaccines, and zidovudine (used to treat HIV).


Drinking alcohol while using Avonex can cause serious liver problems, and you should avoid or limit the use of alcohol while being treated with this medicine.

Frequently Asked Questions

Avonex contains the active ingredient interferon beta-1a.

Inactive ingredients: Sodium acetate, trihydrate, glacial acetic acid, arginine hydrochloride, polysorbate 20, and water for injections.

Avonex is a medication prescribed to help treat relapsing forms of multiple sclerosis (MS), including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease in adults.

Avonex is available as a single-use powder vial, a prefilled syringe, or prefilled autoinjector pen.

Avonex is approved for use in adults only.

Avonex should not be used if you are allergic to Avonex or any ingredients in Avonex, or in children younger than 18 years.

Serious allergic reactions include a severe rash, itching, swelling, especially the face, tongue, and throat, severe dizziness, and trouble breathing.

Limit your alcohol intake while using Avonex as it can cause serious liver problems.

Avoid injecting Avonex into red, bruised, irritated, scarred, or infected skin.

Inject Avonex into the upper thigh once a week at bedtime and as instructed by your healthcare provider.

If you miss a dose, take it as soon as you remember, but do not inject Avonex two days in a row. Do not catch up by taking two doses at once.

Yes, with a prescription, you can purchase Avonex online. Buying medications online is convenient and often less expensive than purchasing them at your local pharmacy.