I know that Avonex and Plegridy are exactly the same drug and so they both have same side effects, but I am wondering if those effects last 1 day only as Avonex or do they last more? Thank you
Plegridy is a re-engineered form of interferon beta 1a, the same molecule in both Avonex and Rebif, with a polyethylene glycol residue attached. This increases the effective mass or size of the molecule and decreases the clearance of the drug from your body. This has positive and negative effects; on the positive side you can take the drug less often and with more consistent and prolonged biological effects. There also seems to be less neutralizing antibody formation; on the negative side, side effects tend to be more prolonged and sometimes delayed in onset. I have had patients report flu like side effects lasting up to 4 days after injection, which can be managed by prolonging the use of ibuprofen or acetaminophen. This problem decreases over time, much like the flu like side effects decrease over time with Avonex. Titration of the dose over the first 4 weeks is also helpful. In my experience the injection site reactions are a little more problematic. These are often delayed in onset, beginning a day after injection, and then can worsen over several days. This requires icing and steroid creams until this improves over time.
Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Professor of Clinical Neurosciences
University of California San Diego