I would tell the boss of the dangers, but, I would continue to talk to him and tell him that you are only doing this because you genuinely like him. I teach with a woman who had ADD and 2 of her sons have ADD. She is one of the best teachers in the school. She has said that she has learned to deal with it and takes meds. I have another adult "friend" who makes me nuts because he is incredibly stupid about his ADD and he's a jerk. There are 2 extremes. How about finding out about some meds that work for adults with ADD or ADHD and tell him about them and ask him to try them for 1 month and see if he can tell a difference and if he says ok then ask him about how he feels in a month and if he says the meds aren't working, then drop it and he'll have to deal with the consequenses.