Interferon Beta Drugs
Interferons (so-called because they “interfere” with viral replication) suppress inflammatory factors in the immune system that are associated with the attack on myelin. Interferon drugs are now the treatments of choice for relapsing-remitting MS. Doctors recommend that these medications be used early in the course of the disease and continued indefinitely, unless they produce no benefits or have severe side effects. When the drug is discontinued, disease activity may increase.
Brands. Interferon drugs used for MS are interferon beta-1b (Betaseron, Extavia) and interferon beta-1a (Avonex, Rebif). Avonex and Rebif are the same chemical, but Avonex is given as weekly intramuscular injection and Rebif is taken as subcutaneous injections three times a week.
Side Effects. Side effects include:
- Flu-like symptoms. Flu-like symptoms (fever, chills, sweating, muscle aches, fatigue) following injection are a common complaint. These symptoms usually lesson over time. Taking acetaminophen (Tylenol) before the injection can help.
- Injection site reactions. Pain, redness, and swelling can occur at the injection site. Applying ice or a cool compress to the skin a few minutes before injection can help prevent pain.
- Less common side effects include allergic reactions, depression, mild anemia, low white blood cell counts, and liver abnormalities. Patients who take interferon drugs should have a baseline liver function test at the start of treatment and receive periodic testing afterwards. Patients should avoid alcohol.
Neutralizing Antibodies That Reduce Effectiveness. Over time, people taking interferons develop antibodies to the drugs, some of which can neutralize their effects. The risk for neutralizing antibodies (NAbs) increases with higher doses and greater frequency of use. Interferons injected under the skin (Betaseron, Rebif) are more likely to produce neutralizing antibodies than Avonex, which is injected into a muscle. Patients who have this reaction may be treated with an alternative interferon or with glatiramer, which has an extremely low risk, for NAbs. Often after switching drugs, NAb levels decline, and the patient may be able to return to the original interferon.
Review Date: 06/17/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.