Interferon Beta Drugs for Multiple Sclerosis

Medically Reviewed by Christopher Melinosky, MD on November 19, 2021

Your body makes interferons naturally. Three forms -- alpha, beta, and gamma -- control the activity of your immune system. But doctors also can use a man-made version of these forms to treat MS, especially interferon betas (sometimes called beta interferons, or interferon meds). Scientists think these man-made interferon betas lessen the inflammation from your misfiring immune system. Less inflammation means less damage to the myelin sheaths that cover your nerves, and so reduced MS symptoms.

Interferon beta medications help make your disease get worse less often, and they stabilize the course of the disease. They might also slow down how quickly symptoms get worse and help people have less physical disability over time. There are five types of interferon beta on the market in the U.S. They’re FDA-approved for relapsing forms of MS:

Interferon Beta-1A (Avonex). You take it once a week as a shot into your muscle. People who start taking it in the early stages of multiple sclerosis may be able to go longer before any physical disabilities begin or get worse.

Interferon Beta-1A (albumin)(Rebif). You get this drug three times per week as a shot under your skin.

Interferon Beta-1B (Betaseron, Extavia). This one comes as a shot that goes just under the skin every other day.

Peginterferon Beta-1A (Plegridy). You can take this interferon less often than the other types -- a shot just under the skin every 2 weeks. The way it’s made makes it last longer in your body.

When Doctors Use Interferon Betas

Doctors typically suggest interferon betas when you have “active relapsing MS,” which means two or more relapses in the last 2 years. In addition, some doctors prescribe them if you have one relapse and/or signs of active disease on an MRI scan (new brain or spine lesions).

Other reasons your doctor might suggest beta interferons:

  • You have secondary progressive MS, but with significant relapses.
  • You have a “clinically isolated syndrome” (first instance of possible MS symptoms) and an MRI shows you're likely to have MS.

How Well Do Interferon Betas Work?

Interferon betas seem to lessen the number of relapses by about a third. Doctors consider the medicines “moderately” effective based on how much they lessen relapses and slow MS-based disability. When the medicines work well, you should have:

  • Fewer and less serious relapses
  • Fewer and smaller brain/spinal cord lesions as shown on an MRI
  • Your disability should worsen more slowly

Over the long term, interferon betas seem to have more than just a moderate effect, especially if you start on one soon after your MS diagnosis.

Interferon Beta Side Effects

Interferon beta medicines are part of a larger group known as “disease modifying therapies,” or DMTs. Compared to other DMTs, interferon betas have fewer side effects. Still, you might have side effects such as:

  • Flu-like symptoms, like fatigue, chills, fever, muscle aches, and sweating during the first weeks of treatment. To keep those from slowing you down, it's best to take the shot at bedtime. You can take pain and fever relievers, like acetaminophen or ibuprofen, before each shot and during the 24 hours after one to help relieve these problems.
  • Swelling, redness, and pain at the place where you get the shot. If the spot gets hard, call your doctor. Don’t give yourself another shot into that site.
  • Trouble with your mood. You might feel sadness, anxiety, crankiness, guilt, trouble concentrating, confusion, and have a hard time sleeping or eating. Tell your doctor about these symptoms right away.

Interferon Beta Risks

Women who are pregnant, breastfeeding, or trying to get pregnant shouldn’t use interferon drugs. When you take them, be sure to use birth control.

Since the meds can cause depression or make it worse, people who’ve had the condition before need to keep an eye on their mood. Let a doctor know about any changes in how you feel.

Interferons also can affect your blood cells and how your liver and thyroid gland work. A few people who took Avonex had severe liver injury or liver failure. Your doctor will give you regular blood tests to be sure your body is working as it should.

Show Sources


National Multiple Sclerosis Society: "Interferons."

Overcoming Multiple Sclerosis: "Interferons."

Multiple Sclerosis Society: “Beta interferons,” “Beta interferon factsheet (PDF),” "Beta interferon and glatiramer acetate."

News release, Teva Pharmaceutical Industries Ltd.

Biogen Idec website.

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