Likely, your friend will have to internally realize he has a problem, before he'll take steps to change his behaviour.
I might suggest you have him read through a bunch of these posts(steer him here by saying you did a search on OC's, and
found a bunch of info, good and
bad(like a few threads down "effects of percocet and
oxycontin") Avoiding the A word(addiction) is probably a good idea at this point.