text: is there something that you can give your teenager that will make him  sick (throw up) if he smokes pot?   ipecac, but that won't get the pot out of his system (the smoke is inhaled not ingested, duh!) and it won't teach him a lesson; he'll just hate you and probably rebel more.  talk with him and tell him he made a bad decision and keep a closer eye on him.  you can prevent this stuff by being around and being an influence and talking on a regular basis even about things unrelated to drugs.  the closer you are, the better the kid usually behaves.