full of that shit

Under the influence. Be it alcohol, heroine, whatever substance comes to mine. Someone who is noticeably and obnoxiously high / drunk. Originated from southern slang, when elderly would talk about being "full of liquor" or flat out drunk.

Person 1: Hey, what'r ya doin in my house?!
Person 2: Dudes, we're outside. You must be full of that shit?