What Is The Difference Between Avonex And Plegridy?

9/20/2014

Q: What differences are there between Avonex and Plegridy? I have read that they are similar but what does that mean?

A: Usually when someone says two, or more, drugs are similar, they mean that they treat the same symptom(s), or have the same mechanism of action (i.e. they do the something in a similar fashion).

Both Avonex and Plegridy are FDA approved disease-modifying therapies used to prevent and treat relapses in MS. Both belong to the same class of drugs called interferons. Avonex is an interferon beta-1a, and Plegridy is a pegylated interferon beta-1a, or peginterferon beta-1a. Pegylated means that a compound called polyethylene glycol (PEG) is added to interferon beta-1a to make it last longer in the body. That means that a person can essentially take the Plegridy less often than the Avonex, but still potentially experience the same effects. Both drugs are injected, but Avonex is injected into the muscle, or intramuscularly, whereas Plegridy is injected under the skin, or subcutaneously.

Avonex and Plegridy have not been compared in terms of their effectiveness. In a 2-year study evaluating the effectiveness of Avonex, people who were taking Avonex decreased the relapse rate by 32% compared with people who weren’t treating their MS. In another trial, those who took Avonex had a 61% decrease in relapse rate compared to those who took a placebo (a pill that does not have pharmacological effects). Seventy-eight percent of those taking Avonex had no increase in disability.

Similarly, during the trial conducted for approval of Plegridy, relapse rates during the first year were reduced by 35.6% compared to those on placebo. For those who took Plegridy, the risk of disability progression was reduced by 38%.

Both Avonex and Plegridy have been shown to have similar adverse reactions, such as injection site reactions and flu-like symptoms.

Avonex is already available by prescription, and Plegridy will be available for prescription in November 2014.

Bear in mind that choosing the right medication can only be determined by you and your doctor. Information like this can simply help you ask the right questions to help you figure out what is best for you.

Deborah Backus, PT, PhD
Director of Multiple Sclerosis Research
Shepherd Center
Atlanta, GA

1 Comment

John Weiss

12/20/2014 05:20:05 am

I was diagnosed with relapsing/remitting MS in 1984. For the next 10 years, it went untreated, as no FDA treatments were available. The was no change in my symptoms after the initial remittance. This meant I lived with compromised balance (no more x-country sking) falling significantly more often, and more concentration to speak clearly. About a year after its FDA approval, I started injecting (under the care of a neurologist) Avonex. This made no obvious change in symptoms, but as I also was stable, I continue treatment. In August, of 2014 Plegridy got FDA approval, and I asked my neurologist if she would prescribe it for me. She did, and today is my first, full day after the titration period. I am writing this because I think you description is lacking in one respect. I think it is important to point out that both drugs are products of the same company, even if you are reluctant to name it. I think it would improve the description, if you pointed out, that Plegridy only needed to be injected by-weekly, and that that is viewed as an advance.

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