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Treatments > Medications Used In MS


Brand Name Chemical Name

(U.S. and Canada)

Interferon (in-ter-feer-on) beta-1a

Primary Usage in MS

Generic Available
Disease-modifying agent No
This medication is taken by injection.

Avonex is a medication manufactured by a biotechnological process from one of the naturally-occurring interferons (a type of protein). It is made up of exactly the same amino acids (major components of proteins) as the interferon beta found in the human body. In controlled clinical trials in relapsing MS, those taking the medication had a reduced risk of disability progression, experienced fewer exacerbations, and showed a reduction in number and size of active lesions in the brain (as shown on MRI) when compared with the group taking a placebo. In a subsequent study of patients who had experienced a single demyelinating event in the optic nerve, spinal cord, or brainstem, and had lesions typical of MS on brain MRI, Avonex significantly delayed the time to a second exacerbation, and thus to a clinically definite diagnosis of MS.

Approval by the U.S. Food and Drug Administration (FDA)
Avonex is approved by the U.S. Food and Drug Administration (FDA) for the treatment of patients with relapsing forms of MS to slow the accumulation of physical disability and decrease the frequency of clinical exacerbations. Patients with MS in whom efficacy has been demonstrated include those who have experienced a first clinical episode and have MRI features consistent with MS.

Proper Usage
Avonex is given as a once-a-week intramuscular (IM) injection, usually in the large muscles of the thigh, upper arm, or hip.

You and your care partner will be instructed in safe and proper IM injection procedures. If you are unable to self-inject, and have no family member or friend available to do the injections, your physician or nurse will administer the injections. Do not attempt inject yourself until you are sure that you understand the procedures.

Avonex is available in two forms:

  • A powder form that comes in a single-use vial and requires reconstitution (mixing) prior to injection. The vials should be stored in the refrigerator, although storage at room temperature is permissible for up to 30 days. Once the medication has been mixed for use, it is recommended that you administer the injection as soon as possible—or within six hours if stored in the refrigerator.
  • A liquid form in a pre-filled syringe. Pre-filled syringes should be stored in the refrigerator, and allowed to come to room temperature (about 20 minutes) prior to injecting. Once removed from the refrigerator, the pre-filled syringe should be used within 12 hours.

Do not expose the medication to high temperatures (in a glove compartment or on a window sill, for example) and do not allow it to freeze.

Do not reuse the pre-filled syringes. Dispose of the syringes as directed by your physician and keep them out of the reach of children.

Since flu-like symptoms are a fairly common side effect during the initial weeks of treatment, it is recommended that the injection be given at bedtime. Taking acetaminophen (TylenolŪ) or ibuprofen (AdvilŪ) immediately prior to each injection and during the 24 hours following the injection will also help to relieve the flu-like symptoms.

Prior to taking Avonex, be sure to tell your physician if you have ever had any of the following medical problems:

  • Depression, anxiety, or trouble sleeping
  • Problems with your thyroid gland
  • Blood problems such as bleeding or bruising easily, anemia, low white cell count
  • Seizures
  • Heart problems
  • Liver disease

Avonex should not be used during pregnancy or by any woman who is trying to become pregnant. Women taking Avonex should use birth control measures at all times. If you want to become pregnant while being treated with Avonex, discuss the matter with your physician. If you become pregnant while using Avonex, stop the treatment and contact your physician.

There was no increase in depression reported by people receiving Avonex in the clinical trial. However, since depression and suicidal thoughts are known to occur with some frequency in MS, and depression and suicidal thoughts have been reported with high doses of various interferon products, it is recommended that individuals with a history of severe depressive disorder be closely monitored while taking Avonex. Additionally, there have been post-marketing reports of depression, suicidal ideation and/or development of new or worsening of pre-existing other psychiatric disorders, including psychosis. Some of these patients improve upon cessation of Avonex dosing.

Avonex is to be used with caution in individuals with a seizure disorder. A few individuals with no prior history of seizures have experienced seizures while on Avonex. Since seizures are known to occur somewhat more frequently in people with MS than in the general population, it is not known whether these seizures were related to the MS, to the medication, or to some combination of the two.

Patients with cardiac disease should be closely monitored for a worsening of their condition. While Avonex is not known to cause cardiac problems, there have been infrequent post-marketing reports of congestive heart failure and other cardiac problems in people with no prior history and no other factors predisposing them to heart problems.

Because of the potential of Avonex to affect the functioning of the liver and thyroid gland, and to cause a drop in the levels of white blood cells, red blood cells, and platelets in a person's system, periodic blood tests are recommended.

Possible Side Effects
Common side effects include flu-like symptoms (fatigue, chills, fever, muscle aches, and sweating). Most of these symptoms will tend to disappear after the initial few weeks of treatment. If they continue, become more severe, or cause you significant discomfort, be sure to talk them over with your physician.

Symptoms of depression, including ongoing sadness, anxiety, loss of interest in daily activities, irritability, low self-esteem, guilt, poor concentration, indecisiveness, confusion, and eating and sleep disturbances, should be reported promptly to your doctor.

Avonex ActiveSourceSM

Medication Index

Other Medications Used as Disease-Modifying Agents

The Disease-Modifying Drugs
Information on the disease-modifying drugs (Betaseron, Avonex, Copaxone, Novantrone, Rebif, and Tysabri). Includes how each is taken, side effects, benefits, and available help.

Is an Oral Disease-Modifying Drug on the Horizon?
February 2006

Neutralizing Antibodies
August 2005

National MS Society Disease Management Consensus Statement
Early intervention recommendations by the Medical Advisory Board of the National MS Society regarding use of the current MS disease-modifying agents

Pregnancy Registries for the Interferon Beta Products Prescribed for Women with MS
The FDA issued guidelines requiring the manufacturers of Avonex, Betaseron, and Rebif to develop pregnancy registries to monitor women who have taken one of these drugs within a week of becoming pregnant or while they were pregnant.

Managing Injection Site Reactions
For professional help with injection anxiety, please discuss the following training program with your nurse or counselor.
Self-Injection Anxiety Counseling (SIAC)

About Interferons

Reprinted with permission from Rosalind C. Kalb (ed.), Multiple Sclerosis: The Questions You Have—The Answers You Need, 3rd Edition. New York: Demos Medical Publishing, Inc., 2004


Last updated September 21, 2006