You are very drunk very fast and your body is unable to metabolize it or get rid of it the way you would alcohol.
You are giddy, suggestible and (in the case I saw) very amorous.
Higher doses put you into a waking coma where you are awake but not able to do much under your own power.
What I saw was one of the worst drug reactions I'd ever seen. Truly scary. And I've seen people on coke, heroin, X, meth and every other damn thing you can name.