The Facts About Treating Multiple Sclerosis with Avonex

Nurse swabbing patient's leg after administering a shot
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Making an informed choice about your multiple sclerosis (MS) drug treatment starts with knowing the facts. In some cases, choices may be limited due to the stage of your disease, the severity of symptoms, or any previous drug therapies you may have been exposed to.

Avonex (interferon beta-1a) is one option typically prescribed in early disease. As with all MS medications, it has both its benefits and shortcomings.


Avonex (interferon beta-1a) is an injectable drug that delivers the lowest dose of interferon compared to other treatment options. It was approved by the U.S. Food and Drug Administration in 1996 for use in persons with an early-stage disease, known as relapsing-remitting MS (RRMS), or for those who have experienced one MS attack but do not meet the diagnostic criteria for MS.


From a statistical perspective, all of the so-called CRAB drugs (Copaxone, Rebif, Avonex, Betaseron) are pretty much equally effective, reducing the risk of relapses in people with RRMS by about a third.

Pre-market clinical research has shown that Avonex may decrease the risk of MS relapses by 32 percent in persons with mild to moderate RRMS. Other post-market studies have pegged drug efficacy at between 19 percent and 38 percent, (the variation of which may be explained by the different duration of the trials and/or the study population). Avonex does not seem to become less effective over time.

There is some evidence, however, that that higher-dose interferons like Rebif may be more effective in some. As such, Rebif is often prescribed as second-line treatment if a person has experienced multiple relapses on Avonex.


Many doctors and patients choose Avonex as the first-line therapy because it only requires one injection per week as opposed to three to seven required for other drugs. The once-a-week dose also reduces many of the flu-like side effects, allowing people to take a shot on Friday and recover over the weekend.

This makes Avonex a convenient choice for people who are working full-time, are caring for small children, or have issues that limit their available downtime. The dosing schedule also appeals to people who are uncomfortable with injecting themselves. Instead, regular office visits can be scheduled (which may ensure better treatment adherence, as well).

As opposed to some of the drugs that are delivered subcutaneously (under the skin), Avonex must be given intramuscularly (usually into a thigh muscle). On the plus side, there tends to be less redness or swelling at the injection site.

Ideally, the injection should be given on the same day every week, although they can be as close as five days or as long as 10 days apart if needed.

Side Effects

The side effects of Avonex are similar to other interferon-based therapies and can often manifest with flu-like symptoms, including:

  • Fever
  • Chills
  • Sweating
  • Muscle Aches
  • Fatigue

As many as 61 percent of people taking Avonex will experience these symptoms which can last anywhere from 24 to 36 hours on average. Many of these will subside over time, although they may last for six months or more to varying degrees.

Depression has also been noted in some, usually after long-term treatment.

Considerations and Contraindications

Avonex is not appropriate for everyone. It may have to be used with caution in some people or avoided entirely in others. Considerations include:

  • Persons on Avonex should be regularly monitored to check their liver enzymes. Avonex may cause an elevation of these enzymes which can lead to liver damage or failure. Persons with pre-existing liver disease or cirrhosis may not be appropriate candidates for Avonex and should be assessed on a case-by-case basis.
  • Avonex should also not be used by women who are pregnant or who are actively planning to conceive. While there is no human clinical research available to assess the potential danger to fetuses, birth defects have been noted in a number of animal studies. Breastfeeding is also not advised in you are on (or have recently been on) Avonex.
  • Avonex should be used with caution in persons with clinical depression. While it is not contraindicated for use (particularly since the risk of depression runs high in people with MS), it does warrant special care to ensure that the person's quality of life is not excessively impacted by treatment.
  • Similarly, Avonex should be used with caution in people with seizure disorders or cardiac problems as it may exacerbate or worsen these symptoms. In rare cases, Avonex has been known to cause seizures and heart irregularities in persons with no prior history or predisposing risk factors for either condition.

    Cost of Treatment

    Avonex's average retail price range in 2017 is just over $6,500 per month or approximately $81,000 per year. Insurance commonly covers the part of the cost of treatment, although copay and out-of-pocket costs can sometimes be exorbitant. Patient assistance programs (PAPs) are available to assist with drug reimbursement or copay assistance for this and other types of costly chronic medications.

    For more information, contact the Support Coordinators at Bionex (the drug manufacturer) at 800-456-2255 or visit for more information.

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    Article Sources
    • U.S. Food and Drug Administration. "HIGHLIGHTS OF PRESCRIBING INFORMATION: Avonex (interferon beta-1a)." Silver Spring, Maryland; updated December 2015.