How much is too much assistance?

My son has had problems since HS years probably but was finally diagnosed rapid cycling BP at 28 almost 2 years ago. He responds well to medication but can't afford it so I pay for it - no gripe there (when he bothers to get his meds).. The gripe shows up when I look at how much other financial support I wind up giving him just about every month for his routine expenses.
For years, I felt he needed financial help but now am wondering if I am really helping him; in fact, am I being a detriment to him? That is my first question.

Second: I am considering giving him a lump sum of money and telling him to use it as a cushion, or blow it,
whatever, but when it's gone, not to ask for assistance for routine daily expenses any more. I would still pay his meds and Dr bills (which I have to pay directly to pharmacy and Dr offices; I used to give him the money to pay bills but he started spending it and not getting his meds!). So my second question is: Is there any hope of this arrangement working?
I am open to suggestions; I just don't know what to do; I'm not always going to be here for him......