I didn't say it!

So, the Ex said that the Boy was having sort of a hard time this afternoon. After some discussion and calming down, this conversation (which, btw, the Ex handled with a good sense of humor) ensued:

The Boy: So, this is why I'm going to start taking some medicine.
The Ex: Yes. How do you feel about that, buddy?
B: Pretty good.
E: Do you understand what the medicine is for?
B: Yes, it's to help my brain get the chemicals it needs, so I can make better choices.
E: That's right.
B: You need some of that medicine, Papa!
E: Buddy, I already take lots of medicine for that sort of thing.
B: Oh. Well, it's not working.