How It Works
The interferon beta medications resemble the natural interferon the body produces during a response by the immune system to disease. It is not completely clear how interferon beta medications 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 medications also limit the activity of gamma interferon, which is a protein produced by the immune system that worsens MS.
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.
Why It Is Used
Interferon beta medications are used to treat people with MS who have relapses followed by periods of recovery (relapsing-remitting MS).
Betaseron is also approved by the U.S. Food and Drug Administration (FDA) to treat people who have secondary progressive MS that is also relapsing.
Some people have only one episode of a neurological symptom such as optic neuritis, but MRI tests suggest they may 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 interferon beta 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 make your time without disease longer.
The interferon beta medications have been tested only in people age 18 and older, but they are frequently used in children with MS.
How Well It Works
Studies have shown that:
- Interferon beta medicines reduce severity of relapses and decrease their frequency by about one third.1
- People who take interferon beta develop fewer areas of damage (lesions) on the brain as seen on MRI.1
- Treatment with interferon beta may reduce the chance of disability in people with relapsing-remitting MS.2
- Interferon beta medicines may help slow the progression of cognitive impairment.3
Avonex was approved by the FDA to treat a first attack when lesions or other MS changes are seen on an MRI but the diagnosis of MS cannot yet be made.
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. This is more common with Betaseron and Rebif. Taking a nonprescription 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 Avonex, Betaseron, and Rebif, and the FDA 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.
In general, treatment with interferon beta should not be started until the diagnosis of MS is certain. The National Multiple Sclerosis Society recommends that treatment with a drug such as interferon beta or glatiramer acetate be started when it is clear that the person has MS to prevent damage to the nervous system.4 While some people recover from an MS attack or relapse without treatment of any kind, the disease may cause permanent damage to the nervous system early on, even while symptoms seem quite mild. The National MS Society also says that treatment with medicine may be considered after the first attack in some people who are at a high risk for MS (before MS is definitely diagnosed).4
The side effects of therapy with interferon beta can be significant, especially the flu-like illness that sometimes follows an injection. A nonprescription pain reliever (such as ibuprofen, naproxen, or acetaminophen) may help reduce these symptoms and allow you to tolerate a higher dose of medication, which may be more effective in treating the disease. This is an important consideration for people who are on long-term interferon therapy.
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 medication 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 medication.
- Treatment may cost more than $10,000 per year.
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 medications.
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.5 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.
References
Citations
Sadiq SA (2005). Multiple sclerosis. In LP Rowland, ed., Merritt's Neurology, 11th ed., pp. 941–963. Philadelphia: Lippincott Williams and Wilkins.
Nicholas R, Chataway J (2006). Multiple sclerosis, search date January 2006. Online version of BMJ Clinical Evidence. Also available online: http://www.clinicalevidence.com.
Frohman EM (2003). Multiple sclerosis. Medical Clinics of North America, 87(4): 867–897.
National Clinical Advisory Board of the National Multiple Sclerosis Society (2007). Disease Management Consensus Statement. New York: National Multiple Sclerosis Society. Available online: http://www.nationalmssociety.org/site/PageServer?pagename=HOM_PRO_expert_opinion_papers.
Bennett KA (2005). Pregnancy and multiple sclerosis. Clinical Obstetrics and Gynecology, 48(1): 38–47.
Credits
| Author | Monica Rhodes |
| Editor | Kathleen M. Ariss, MS |
| Associate Editor | Denele Ivins |
| Associate Editor | Pat Truman, MATC |
| Primary Medical Reviewer | Anne C. Poinier, MD - Internal Medicine |
| Specialist Medical Reviewer | Colin Chalk, MD, CM, FRCPC - Neurology |
| Last Updated | February 28, 2008 |
