Medicines used to prevent attacks of MS are effective. They reduce the frequency of attacks by 50% or more. There are times when MS medicines do not work.
These are examples of when your MS medicine may not be working:
1) a moderate or severe attack / relapse of MS symptoms in the past 12 months
2) 2 or more mild attacks over a time of two years
3) 1 – 2 new enhancing lesions on MRI
4) 2 or more T2 / FLAIR lesions over 2 years
5) significant disability with walking, moving the arms or with thinking or memory