I regularly take Concerta for my ADHD and I get that too. I don't eat, I don't want to do anything except watch television shows by myself, I don't want to talk to anyone, and I don't even want to listen to music. I feel an unsettling level of uncertainty, apathy, and self loathing all at once. I'm depressed as it is but I know it's worse when I take it.

I mainly wanted to let you know that your brother is not alone in these feelings. As for the dealing with it, I haven't found any way to properly deal with it.