80 mg oxycontin, how many would it take to kill a person?

I'm not a murderer nor am I planning on committing suicide, but my friend takes 80 mg oxycontin and last week he passed out but he didn't die. - How can I get him to stop? How many pills does it take to die on it? I don't want my friend to die I already lost one friend this way. I've been watching him and he doesn't crush it.

Also, what are the side effects or whatever or symptoms he would experience if he's about to die from it? would it be painful?

: http://alcoholdrugstreatment.info/80-mg-oxycontin-how-many-would-it-take-to-kill-a-person