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Drugs Used for Treating Multiple Sclerosis (cont.)

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Rebif (interferon beta-1a)

Rebif is the second formulation of interferon beta-1a which was approved by the FDA for relapsing-remitting MS in March 2002. Rebif was approved after the EVIDENCE study showed that Rebif was more effective than Avonex. Study findings show that approximately 75% of patients treated with Rebif did not relapse at 24 weeks of treatment versus 63% for Avonex. Additionally, at the end of 48 weeks, 62% of Rebif treated patients were relapse free compared to 52% for Avonex.

Rebif is administered by subcutaneous injection three times weekly. Common side effects associated with Rebif are injection site reactions, flu-like symptoms, abdominal pain, depression, abnormal liver tests and abnormalities of the cells in the blood. Less common and transient side effects include thyroid dysfunction, shortness of breath, tachycardia, and neutralizing antibodies. Due to the risk of miscarriage or harm to fetus, Rebif should only be used during pregnancy if the potential benefit justifies the potential harm to the fetus. Rebif is classified FDA pregnancy risk category C.

Betaseron and Extavia (interferon beta-1b)

Interferon beta-1b, the active chemical in Betaseron, is a naturally occurring protein found in the body. Betaseron is synthesized using recombinant DNA technology and is identical to the natural protein. Although the exact mechanism of action of interferon beta in MS is unknown, it is thought that interferon beta-1b inhibits the expression of chemicals such as interleukin-1 beta, tumor necrosis factor, interleukin 6, and others which cause the inflammation and neurodegeneration associated with MS. Betaseron is used for the treatment of patients with relapsing forms of MS to decrease the frequency of acute flare ups. Betaseron was approved by the FDA on July 23th 1993 for the treatment of relapsing-remitting MS. Betaseron is injected subcutaneously every other day. In clinical trials patients treated with Betaseron experienced fewer flare ups. Side effects associated with Betaseron include flu-like symptoms, depression, abnormal liver tests, skin reactions, thyroid dysfunction, and a drop in red and white blood cells and platelets. Allergic reactions and necrosis (cell death) of the skin have also been associated with Betaseron. Betaseron is classified FDA pregnancy risk category C and should only be used during pregnancy if clearly needed. Four women participating in the Betaseron RRMS clinical trial experienced spontaneous abortions. Although it is not clear if the abortions were related to Betaseron therapy, the manufacturer recommended limiting its use to patients who clearly need it. Patients exposed to Betaseron during pregnancy are encouraged to enroll in the Betaseron Pregnancy Registry by either calling 1-800-478-7049 or visiting the Betaseron Pregnancy Registry website.

Extavia (interferon beta-1b)

Extavia, a second formulation of interferon beta-1b, was approved by the FDA for the treatment of relapsing-remitting MS in August 2009. Importantly, Extavia is identical to Betaseron and therefore shares the same pharmacological benefits and risks for side effects. As with Betaseron, Extavia is administered via subcutaneous injection every other day.

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