Something is wrong here. He was an educated druggie. Educated druggies, pros vs amateurs, know how to pick their sins. Cokeheads, alcoholics and heroin addicts KNOW that mixing drugs is deadly, and it's PHYSICALLY IMPOSSIBLE to be addicted to both coke and oxycontin at the same time. There are only so many neurotransmitters in the brain.
So who fed him the oxycontin? Did he think it was something else?