I use it very sparingly - started out with 100 mg - it does give you a little extra - but more then 50 - at the most 100 mg - and my legs can't keep up with the rest of me - so I suppose it comes down to how much fatigue you have with MS and what your individual day consists of - if I was working I'd take it - I'm retired - I don't need to keep going all day - I can take a nap or sit if I'm tired and it is very expensive !! Had an rx filled in November and still have quite a bit left -