I'm so sorry that I didn't see your question before now. Comparing the dosage or presumed potency of Avonex vs. Rebif is difficult to do. This is because Avonex is given in the muscle and Rebif is injected under the skin. This difference in method of delivery makes it hard to compare potency. It is possible that less of Rebif is actually absorbed into the body (I'm guessing) and that is why a higher concentration of the drug is used.
Some doctors might consider switching from Avonex/Rebif to Betaseron if they want to stick with an interferon drug. Please know that I'm not an expert on medication and certainly not a medical professional.
Switching drugs is such a personal thing. So many variable and it's too bad that your doctor isn't providing more guidance. Perhaps ask him directly what is recommended for a patient whose disease is suddenly more active. Tell him point blank - "I want and need your expert advice!"
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