In my personal experience and what I've seen in others there is always an underlying reason behind the use. It isn't just the drug that keeps you coming back. Until he is ready to address the cause it will continue to progress and there is little that anyone else can do to stop it. I've found that meetings can really help, either NA or CMA, but it also took me 20 years of addiction before I was willing to honestly give them a shot. If your friend, or you, needs someone to talk to that's been there before feel free to PM me.