Non-BP people like to abuse codeine to get high. They mix it with other ingredients to create "purple drank," I think it's called. Lil Wayne is one person who drinks/drank it, and that was all over the news years back because he was hospitalized for it. I forget what it did to him, but I think that's irrelevant.

ANYWAY, I wouldn't be surprised if codeine made you manic if it can make the average person get high under certain circumstances.

Hope you get better soon!