get the concerta put it in a lock box that only your sister can get into ...if he wont give her her meds she need to tell her doctor what is going on she needs her meds and he needs help.
I don't know what concerta is hon. But I wish you and your family well. I would try to get maybe a peer of his(an uncle maybe or something?), to try to get him to go to a doc and be checked out. Cause parents have a hard time listening to they're kids sometimes, ya know?
So if he has a best friend or close relative I'd speak to them about it. Thats just one womans opionion. All my best sweetheart. I know whats it's like to worry about your Dad. Take care, Lotsa Love, Lori
ps-hang tight-someone who knows about that stuff will probably speak up on here soon.