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Letters to the Editor
March 2000

Interferons in the Treatment of Multiple Sclerosis: Errors and Misrepresentations

Arch Neurol. 2000;57(3):426-427. doi:

Rice and Ebers1 question the evidence for the efficacy of interferons in preventing disease progression in multiple sclerosis (MS), particularly that of interferon beta-1a (IFN-β-1a) (Avonex; Biogen Inc, Cambridge, Mass). They make a number of valid points; however, their article also contains significant factual errors and misrepresentations.

First, their dose comparison is factually wrong. They state that the dose of IFN-β-1a was 21.4% of the dose of interferon beta-1b (IFN-β-1b) (Betaseron; Berlex Laboratories Inc, Wayne, NJ), which is like comparing apples and oranges. The 2 interferons are measured against different standards. While comparison of doses will vary depending on the test system, when measured against the natural interferon standard used for IFN-β-1a, the IFN-β-1b dose is closer to 5.0 MIU than 8.3 MIU.2 Thus, it is about 34% of the weekly dose, not 21.4% as stated in their article. When absorption differences3 and effects of antibodies are factored in, the effective doses may be comparable. Whether the much higher blood levels and bolus effect achieved with IFN-β-1a leads to a better or worse dose response than the nearly constant level achieved with IFN-β-1b remains to be established. There are no adequate dose comparisons at this time.

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