Is Avonex Right for You?

Nurse swabbing patient's leg after administering a shot
PhotoAlto/Michele Constantini/Getty

I am not going to tell you why you should be on disease-modifying therapy for MS. Instead, I want to provide some information to help you decide if Avonex is the right choice for you as you consider the various existing disease-modifying therapies (DMT).

I know that the decision-making process around MS treatment can be confusing and stressful, with the drug companies presenting information on colorful websites with testimonials from smiling patients who “swear by” their drug of choice.

My goal is to give you the practical information that I was interested in when I was trying to make a decision about which MS treatment to start.

Avonex: The Bottom Line

Avonex (Interferon beta-1a) provides the lowest dose of all the interferons (30mcg/week, while Rebif is 44mcg 3 times/week). There is some evidence that higher-dose interferons may be more effective in some patients, and many doctors switch their patients to Rebif if they have several relapses on Avonex.

That said, it is still true that all of the CRAB drugs (Copaxone, Rebif, Avonex, Betaseron) are pretty much equally effective overall, offering about one-third reduction in relapses when compared to a placebo over two years in people with relapsing-remitting MS (RRMS).

People with RRMS usually make their treatment decisions based on their doctor’s advice and experience with similar patients, as well as concerns about convenience, side effects and cost.

Avonex is also FDA-approved for use in people who have had one attack, which is suspected to be MS, but does not meet all diagnostic criteria.

Many people choose Avonex as their first disease-modifying therapy because they will only need one injection per week, as opposed to 3 to 7 injections per week that are required for some of the other drugs.

The once-a-week dosing schedule also reduces flu-like side effects commonly associated with these drugs (many people take their injections on Friday night, giving them the weekend to recover).

These factors make Avonex a convenient choice for people who are working full-time, caring for small children, or have other concerns that make limiting "down time" due to side effects a necessity.

The dosing schedule also appeals to many people who are uncomfortable with injecting themselves, although Avonex injections are intramuscular (usually injected into the muscle of the thigh), whereas all of the other CRAB drugs are given subcutaneously (injected into the fat right under the skin).

If people are very nervous about injecting themselves -- and don’t have family members or friends willing to do it -- arrangements can usually be made for a technician at a doctor's office to give the injections. However, most people eventually become “comfortable” enough with the process to do it themselves.

More Details on Avonex

Type of MS and Severity
Avonex is for people with RRMS. It is also approved for use in people who have experienced one “MS event,” but do not yet meet all criteria for MS.

Similar to all the CRAB drugs, Avonex was found to decrease relapses by 32% in an initial trial of patients with mild to moderate RRMS over 2 years (18 to 38% decrease in subsequent studies, depending on type of patient and length of treatment time).

Avonex does not seem to become less effective over time.

Necessary Monitoring
Blood tests need to be done every 3 months for the first year to check white blood cell count and liver function. After a year, these checks can be reduced to once every four months.

Injection Considerations
Avonex is given once a week as an intramuscular injection into the thigh, which is usually done by the patient or a nurse. The needle is 1.25 inches long, and is 23-gauge (however, a 25-gauge (thinner), 1-inch (shorter) needle can be substituted if a doctor gives the okay). Red spots at the injection sites, as seen with the other interferon treatments, do not usually occur since Avonex is injected into the muscle.

Avonex should be given on the same day every week, but injections can be as close as 5 days or as long as 10 days apart.

Side Effects
The side effects of Avonex are similar to those of other interferon-based therapies, however Avonex does not cause as many injection-site reactions as the others.

  • Flu-like Symptoms
    The most important side effect is flu-like symptoms, which are experienced by about 61% of patients. These include: fever, chills, sweating, muscle aches and fatigue (but not nausea or stomach upset), and they last for 24 to 36 hours. This side effect is usually the worst after the first dose and progressively lessens with each injection. Most people still experience these symptoms after 6 months, though they're usually more tolerable. This reaction can be reduced by starting with a low dose and increasing to a full dose gradually over several weeks. Taking ibuprofen or acetaminophen a couple hours before and after an injection can help with some of these side effects, too.
  • Liver Damage
    Hepatitis and elevated levels of liver enzymes, which can cause liver damage, have been reported. Regular monitoring is required to prevent liver damage from occurring or progressing (see "Necessary Monitoring" above).
  • Blood Counts
    Avonex can cause a decrease in the numbers of red and white blood cells, as well as a reduction in the number of platelets in the blood.
  • Depression
    Avonex should be used with caution in patients with depression.

Avonex has been available since 1995. It is made by Biogen Idec.

Avonex comes in new, prefilled syringes (called luer lock), which can be left unrefrigerated for up to 7 days. However, Avonex also comes in a powder that must be mixed; it can be kept at room temperature for up to 30 days.

If prefilled syringes are stored in the refrigerator, they should be brought to room temperature before injecting (take them out of refrigerator 30 to 60 minutes before use.) Because it is an intramuscular injection, it does not come with an injecting device.

Avonex costs between 24,000 and 30,000 dollars a year. (Check exact prices at It is covered by most insurance plans. For assistance in figuring out reimbursement, patients can call reimbursement specialists at Avonex Services at 1-800-456-2255.

According to the company website: “Our specialists can help you with any questions about your health insurance plan and your percentage of coverage, as well as assist in ‘prior-authorization.’ They can also assist with claims denials and find other sources of support for which you may qualify, including the Avonex Access Program, which provides support to qualified uninsured patients.”

Your doctor’s office or local chapter of the MS Society should also be able to assist you in determining financial options for affording treatment.

Avonex can be used indefinitely. It has a comparable safety record to other interferon-based drugs, which are considered safe for long-term use as long as appropriate monitoring for liver function and blood cell count are maintained.

Pregnancy and Breastfeeding
Avonex is considered to be in "pregnancy category C," meaning that it caused some harm to fetuses in animal studies but the effect in humans is unknown. Avonex should not be used by women who are pregnant and should be stopped for some time before trying to conceive (usually one to three months; discuss this with your doctor).

Avonex should not be used by women who are breastfeeding.

Avonex can be used in conjunction with other drugs. However, it should be used with caution in people with seizure disorders and cardiac problems, as there have been reports of people developing these problems while on Avonex who had no prior history or predisposing risk factors. Some also experienced exacerbations of existing seizure or cardiac problems. People with a history of depression should be monitored closely while on Avonex.

More Information: Avonex is made by Biogen Idec. For more information, visit the Avonex website, or call Avonex Services at 1-800-456-2255.


Benatar M. Interferon beta-1a and beta-1b for treatment of multiple sclerosis. Lancet 2002;360:1428; author reply 1428-1429.

Durelli L, Verdun E, Barbero P, et al. Every-other-day interferon beta-1b versus once-weekly interferon beta-1a for multiple sclerosis: results of a 2-year prospective randomised multicentre study (INCOMIN). Lancet 2002;359:1453-1460.

Jacobs LD, Cookfair DL, Rudick RA, et al. Intramuscular interferon beta-1a for disease progression in relapsing multiple sclerosis. Ann Neurol 1996;39:285-294.

PRISMS Study Group. Randomised double-blind placebo-controlled study of interferon beta-1a in relapsing/remitting multiple sclerosis.

Lancet 1998;352:1498-1504.

Panitch H, Goodin DS, Francis G, et al. Randomized, comparative study of interferon beta-1a treatment regimens in MS: the EVIDENCE Trial. Neurology 2002;59:1496-1506.

Rudick RA, Goodkin DE, Jacobs LD, et al. Impact of interferon beta-1a on neurologic disability in relapsing multiple sclerosis. The Multiple Sclerosis Collaborative Research Group (MSCRG). Neurology 1997;49:358-363.

Continue Reading