Interferon beta for multiple sclerosis

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Interferon beta for multiple sclerosis


Generic NameBrand Name
interferon betaAvonex, Betaseron, Rebif

Avonex is injected into the muscle of the thigh, upper arm, or hip once a week. Rebif is injected beneath the skin 3 times a week. Betaseron is injected beneath the skin every other day.

How It Works

The interferon beta medicines resemble the natural interferon the body produces during a response by the immune system to disease. It is not completely clear how interferon beta medicines work in people with multiple sclerosis (MS). But it is known that they affect the immune system and also help fight viral infections. They also work by preventing inflammation and demyelination in the central nervous system.

The interferon beta medicines also limit the activity of gamma interferon, which is a protein produced by the immune system that makes MS worse.

Why It Is Used

Interferon beta medicines are used to treat people with MS who have relapses followed by periods of recovery (relapsing-remitting MS).

Some people have only one episode of a neurological symptom such as optic neuritis. Yet MRI tests suggest these people have MS. This is known as a clinically isolated syndrome. Many of these people go on to develop MS over time. In some cases, doctors will prescribe medicine (either interferon beta or glatiramer) for people who have had a clinically isolated syndrome. These medicines, when taken early or even before you have been diagnosed with MS, may keep the disease from getting worse or extend your time without disease.1

The interferon beta medicines have been tested only in people age 18 and older. But they are frequently used in children who have MS.

How Well It Works

Studies have shown that:

  • Interferon beta medicines reduce severity of relapses and decrease their frequency by about one-third.3
  • People who take interferon beta develop fewer areas of damage (lesions) on the brain as seen on MRI.3
  • Treatment with interferon beta may reduce the chance of disability in people who have relapsing-remitting MS.4

Side Effects

Side effects of interferon beta may include:

  • Flu-like symptoms—such as fatigue, chills, fever, and muscle aches—for 1 to 2 days after an injection. These symptoms, which may be temporarily debilitating for some people, usually do not continue after 2 to 3 months of treatment. Taking a pain reliever such as ibuprofen or acetaminophen just before and after each injection may help reduce these symptoms.
  • Headaches.
  • Redness, swelling, or tenderness at the injection site. Taking a non-prescription pain reliever just before or after an injection can reduce this side effect.
  • Depression, which some doctors have thought may increase with interferon beta use. The makers of these medicines and Health Canada have added a warning to the labels suggesting that these medicines should be used with caution in people with existing depression or other severe psychiatric disorders. Talk to your doctor before trying any of these medicines if you have depression or other mood disorders, including thoughts of suicide.
  • Anxiety, confusion, and eating and sleeping disturbances. These are not very common and may be related as much to MS as to the treatment. Talk to your doctor if these symptoms last more than a day or two.

People who are taking interferon beta need to have regular blood tests (usually every 3 months in the beginning) to monitor white blood cell counts and liver function, which can be affected by interferon therapy.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Some people treated with interferon have become depressed (feeling sad, feeling low, or feeling bad about oneself). Depression is common in people with MS. If you are noticeably sadder or feeling more hopeless, you should tell a family member or friend right away and call your doctor as soon as possible. You should tell the doctor if you have ever had any mental illness, including depression, and if you take any medicines for depression.

The National Multiple Sclerosis Society recommends that people with a definite diagnosis of MS and active relapsing disease start treatment with interferon or glatiramer. The group adds that medicine may also be considered after the first attack in some people at high risk for MS but before it is diagnosed.5 The Canadian MS Clinics Network and the Multiple Sclerosis Society of Canada (MSSC) stress the importance of early treatment for MS.2

In addition to side effects, there are some drawbacks to treatment with interferon beta:

  • Treatment is not effective for some people. And it is hard to predict whether the medicine will help a particular person.
  • The long-term risks of treatment are unknown.
  • Some experts worry that in some people interferon may become less effective after long-term use because the body may produce neutralizing antibodies that may reduce the effect of the medicine
  • Treatment is costly. Your provincial health plan may cover most or all of the cost of your medicine. Ask your doctor or contact your provincial health plan for more information.

Talk with your doctor if your MS relapses have not become less severe or less frequent after 6 months of interferon therapy. It may be time to consider other medicines.

As you consider your treatment, talk with your doctor about the possible benefits of the medicine compared with side effects, cost, and the possibility that the medicine could become less effective over time.

Many doctors suggest you not take interferon beta during pregnancy. Some studies in animals have shown an increased risk of miscarriage. Women taking interferon should use a reliable form of birth control if there is any chance they could become pregnant. If you become pregnant while you are taking interferon beta or are thinking about trying to become pregnant, talk to your doctor.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. Faggiano CM, et al. (2008). Recombinant interferon beta or glatiramer acetate for delaying conversion of the first demyelinating event to multiple sclerosis. Cochrane Database of Systematic Reviews (2).
  2. Multiple Sclerosis Society of Canada (1999). Consensus statement urges early treatment and wider access for MS drugs. Multiple Sclerosis Society of Canada. Available online:
  3. Sadiq SA (2005). Multiple sclerosis. In LP Rowland, ed., Merritt's Neurology, 11th ed., pp. 941–963. Philadelphia: Lippincott Williams and Wilkins.
  4. Nicholas R, Chataway J (2009). Multiple sclerosis, search date June 2008. Online version of BMJ Clinical Evidence:
  5. National Clinical Advisory Board of the National Multiple Sclerosis Society (2007). Disease Management Consensus Statement. New York: National Multiple Sclerosis Society. Available online:


By Healthwise Staff
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Primary Medical Reviewer Adam Husney, MD, MD - Family Medicine
Specialist Medical Reviewer Colin Chalk, MD, CM, FRCPC - Neurology
Last Revised April 15, 2010

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