Weed is not physically addictive but it can be a physiologically thing. Personally I don't believe this is much of a problem unless it starts to disrupt his daily life. Alcohol in my opinion is a much worse.
Oc can be a heroin like high and it's very addictive. It can easily evolve into a big problem if he does it often. Chemical addiction is extremely destructive. It will tare away at his life and everyone around him.
He will say he just wants to try it.
He will say he only does it every once in awhile.
He will say he only does is socially.
He will say he can quit anytime.
He will try to hide it.
He will accept it.
Maybe he will settle on oxys or maybe he will settle on a different chemical. You said he does other pills. I can think of at least 20 things off the top of my head. You never know how far down the rabbit hole goes, so to speak. It doesn't really matter where he stops because they all lead to a dead end.
In my opinion what separates a recreational drug user, from a full blow drug user, is an addictive personality; the need to fill a gap (best way I can explain). Go ahead and argue with me, my mind is set.
He’s a recreational drug user if he says he is a social user but really only uses once in awhile.
He’s an addict when he says he only does it once in awhile but abuses it in most social settings.
If you think he may be an addict or is becoming an addict you can try to help him, but if he doesn’t want your help there isn’t much you can do. You could consider talking to someone who specializes in drug addiction but, agen, if he doesn’t accept the help, even from a professional, there is not much you can do.
I might be slightly over dramatizing this but drug abuse evolves quickly. Keep an eye on him because if you think things are starting to get out of control, there generally worse then you know.