In both Avonex and Rebif, interferon beta-1a is the active ingredient. However, there are some key differences, including: Injection method
Avonex is injected intramuscularly, meaning it is injected into the muscle, whereas Rebif is injected subcutaneously, meaning under the skin. Patients often report Rebif injections as being less painful than Avonex injections. Dosage schedule
Avonex injections are required once per month, whereas Rebif injections are required three times per week with at least 48 hours between each injection. It is recommended that Rebif injections are taken at the same time and on the same days each week (e.g. Monday, Wednesday, and Friday evenings). Strength
Avonex contains 30 mcg of the active ingredient, interferon beta-1a, within a 0.5 mL solution. Rebif is available in a strength of 8.8 mcg in a 0.2 mL solution, 22 mcg in a 0.5 mL solution, and 44 mcg in a 0.5 mL solution. The 8.8 mcg strength Rebif is used during the titration period (at the beginning of treatment, when the dosage is increased over a number of weeks before reaching the full dosage), whereas the 22 mcg and 44 mcg can both be prescribed as full dosage strengths. The decision about whether Avonex or Rebif is the right treatment for you should be made in consultation with your doctor and will be based on aspects such as personal preferences and lifestyle, the severity of your symptoms, and your health history.