How long after drinking charcoal for stomach pumping can you go home?

I think i would ask. the friendly folks in the ER where you (or whoever) is getting their stomach lavaged about that. Depends on the cause - if someone takes a bunch of stuff in order to hurt themselves, they are going to be kept around long enough to determine they are safe, and may even end up being held involuntarily under a mental health committment. If it was accidental, people are usually observed for short time.