Hi and sorry to hear about your medication situation.
Usually bschool is NOT a physically strenuous experience. In fact, many wish it would be so that it would force them to workout more and spend less time with books and couped up in team meetings. There are however, a few events that do require some physical abilities - usually during the orientation week there are some group activities, which you can just watch from sidelines - I think that should not be an issue as they will find you a job one way or another.
Otherwise, the only other things you may have to do is show up for classes and attend networking events (some travel). That's about as strenous as it gets.
I would email the school and ask for their advice. Granted that we don't know which program you are headed to, they may have a better perspective/view of the situation and will be able to advise you better but it should not preclude you from starting this year, I would guess.