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Avonex (interferon beta-1a)

Reviewed by: HU Medical Review Board | Last reviewed: April 2023

Avonex is a form of interferon beta given by intramuscular (IM) injection. It is approved for the treatment of patients with clinically isolated syndrome (CIS), relapsing-remitting multiple sclerosis (RRMS), or active secondary progressive MS (SPMS).1

Use of Avonex is intended to slow the progression of physical disability and decrease the number and severity of MS flare-ups. Avonex is prescribed for people with MRI results that contain features consistent with multiple sclerosis lesions.1

What are the ingredients in Avonex?

The active ingredient in Avonex is interferon beta-1a, a 166 amino acid glycoprotein.1

How does Avonex work?

Avonex is an interferon, a group of glycoproteins produced by the body to fight viral infections and other foreign matter. Avonex contains all of the same basic components as the interferon beta that occurs naturally in the human body.1

Interferons help control immune system activities. Avonex helps to inhibit inflammation that can cause MS flare-ups.1

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What are the possible side effects?

Many clinical trials evaluated the safety and efficacy of Avonex. The most common side effects experienced by those taking Avonex include:1

  • Headache
  • Chills
  • Fever
  • Pain
  • Depression
  • Injection site reactions
  • Nausea
  • Fatigue
  • Backache
  • Muscle aches

These are not all the possible side effects of Avonex. Talk to your doctor about what to expect when taking Avonex. You also should call your doctor if you have any changes that concern you when taking Avonex.

Other things to know about Avonex

In addition to routine MS lab tests, complete blood and differential white blood cell counts, platelet counts, and blood chemistries, as well as liver function tests, are recommended during Avonex therapy.1

Before starting Avonex, talk to your doctor if you:1

  • Have a history of hypersensitivity or allergic reaction to natural or recombinant interferon beta, albumin, or any other component of the formulation
  • Have a history of anaphylaxis
  • Are pregnant or planning to get pregnant. Based on data from animal studies, Avonex may cause harm to an unborn baby. Avonex should be used only if the potential benefit of Avonex therapy exceeds the risk to the fetus.
  • Have a history of depression, suicide, and/or psychotic disorders. Any new symptoms of depression, suicidal ideation, and/or psychosis should be reported to your doctor. Consider discontinuation of Avonex if depression occurs.
  • Have hepatic (liver) injury
  • Are a congestive heart failure patient, who should be monitored for worsening symptoms
  • Have thrombotic microangiopathy (damage to small blood vessels in vital organs)
  • Experience development of new autoimmune disorders
  • Experience seizures

People with the above conditions should be monitored closely while taking Avonex. Before beginning treatment for MS, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.1

For more information, read the full prescribing information of Avonex.