My 78 year old mother recently started takeing Avonex. The first shot, no side effects. Since then, she has had pretty severe flu-like symptoms even though she takes her tylenol and anti-nausea meds. The worst side effect is muscle weakness to the point of not being able to prop herself up in bed, stand or walk. This last through the night the injection is given and is somewhat better in the morning, but takes 2-3 days to completely come out of it. Does anyone else have similar episodes? She called the Avonex reps, but they were no help.