you've just got to tell him, without scolding , that he has to be careful with what hes doing. i mean i dont know about you, but hard drugs fucked up my life for a good two years and just let him know how much you care about him and that you don't want shit like that to happen to him. ending up in hospitals aint fun. tell him that its okay to experiment or whatever cause it would be hypocrisy to tell him not to but LET HIM KNOW that theres a thin line between experimentation and abuse.