Avonex® (interferon beta 1a)
Drug Identification Number (DIN) 02237770; 02269201 (pre-filled syringe)
Biogen Canada

Avonex (interferon beta 1a) is a type of protein called a beta-interferon that is produced from mammalian cells using recombinant DNA techniques (a series of procedures used to join together DNA segments). Beta interferon occurs naturally in the human body in response to initiating factors such as viruses.

Indications and use

Avonex is approved for the treatment of:

  1. relapsing forms of MS (relapsing-remitting MS and secondary-progressive MS with relapses) to slow the progression of disability, decrease the frequency of MS attacks, and reduce the number and volume of brain lesions seen on magnetic resonance imaging (MRI).
  2. people at risk of developing clinically definite MS (CDMS), so as to delay the onset of clinically definite MS and to decrease the number and volume of active brain lesions on MRI.

    Before Avonex is initiated, people at risk of developing CDMS must have brain lesions on MRI and other possible diagnoses must be ruled out.

    There are no adequate and well-controlled studies of Avonex in pregnant women and it is not known whether Avonex is excreted in human milk.

Administration and dosage

Avonex is self-injected once per week into the muscle (intramuscularly). The medication is available as a pre-filled syringe (Avonex® PS) and pre-filled auto-injector (Avonex® Pen). The recommended dose of Avonex is 30 mcg once per week.

Mechanism of action (MOA)

The main effects of Avonex are to block the activity of certain immune system cells and to reduce the passage of these immune cells into the central nervous system, where they cause inflammation and damage to myelin (the insulating material that protects nerves and helps them work properly).

Side effects*

The most common side effects of Avonex therapy include flu-like symptoms (fever, chills, sweating, muscle aches and tiredness) and injection site reactions.This is not a comprehensive list of all possible side effects of Avonex. Please see the Avonex product monograph for a list of other potentially serious side effects. It is important that those with MS discuss side effects about any medication they are considering with their physician. (*Health Canada, product monograph for Avonex.)

Neutralizing antibodies

Some people taking a beta-interferon therapy develop neutralizing anti-bodies (NAb). It is not known if NAbs completely “neutralize” the clinical benefits of therapy. Some research has found that a higher NAb level may be associated with a lesser treatment effect. The level of NAbs associated with the use of Avonex is lower than that seen during treatment with the other beta-interferons. Studies are continuing in this area, as is the development of a standardized NAb test.

Clinical trials

Clinical Trials in Relapsing-Remitting MS

MSCRG Study: Multiple Sclerosis Collaborative Research Group StudyIn this clinical trial, 301 people with relapsing-remitting MS were treated with either Avonex at a dose of 30 mcg once per week or placebo (a treatment that has no active medication) for over 2 years. Results of the study showed that Avonex delayed the time to sustained progression of disability compared to placebo. The proportion of patients who progressed was reduced 37% (21.9% vs. 34.9%). Avonex reduced the annual attack rate by 18-32% compared to placebo and also reduced the number of brain lesions on MRI.1 [Jacobs et al. Ann Neurology 1996; 39: 285-294]

Clinical Trials: Single Event Suggestive of MS

CHAMPS Study: Controlled High-Risk Subjects Avonex Multiple Sclerosis Prevention Study
This study examined whether Avonex could reduce conversion to clinically definite MS in people who had a single neurological event suggestive of MS (an event involving the optic nerve, brain stem/cerebellum, or spinal cord) but who had not been diagnosed with MS. A total of 383 persons were treated with Avonex or placebo for up to 3 years. Treatment with Avonex resulted in a 44% reduction in the chance of having a second MS attack over the three-year period.2 [Jacobs et al. N Engl J Med 2000; 343: 898-904]

Cost reimbursement

The price of Avonex is approximately $20,000 per year. Much of the cost can be reimbursed through private and group health plans for people who meet the prescribing criteria and through provincial drug programs for individuals who meet the prescribing criteria.

Drug support program

Further information for persons with MS is available from Biogen ONETM program at 1-855-MSONE-00 or 1-855-676-6300.


  1. Jacobs LD, Cookfair DL, Rudick RA, et al. Intramuscular interferon beta-1a for disease progression in relapsing multiple sclerosis. The Multiple Sclerosis Collaborative Research Group (MSCRG). Ann Neurology 1996; 39: 285-294.
  2. Jacobs LD, Beck RW, Simon JH, et al. Intramuscular interferon beta-1a therapy initiated during a first demyelinating event in multiple sclerosis. CHAMPS Study Group. N Engl J Med 2000; 343: 898-904.

Avonex® is a registered trademark of Biogen Canada Inc.