smokey - I'd like to know if that GP still thinks that hard drugs increase someone's tollerance if they've been clean for 12-24 months. Don't get me wrong, I've seen an ice user go to hospital and get given an injection that should have knocked them clean out and they just sat there wondering if they'd given the dose yet. The nurses were shocked and she needed a 2nd one to do the trick. However this was a regular user who was probably still high.
If people abuse pain meds like vicodin or oxycontin, or even seriously abuse codeine then sure, other pain killers will need a higher dose. I also understand an ex-junkie refusing anything other than panadol as they recognise that they have an addictive personality, but I don't see what that has to do with tolerance.
However, for someone like Ben Cousins who was addicted to recreational drugs, but not to any degree that affected his performance as an elite sportsman, I struggle to see how it would make a massive difference to his pain killer tolerance after he's been clean for going on 2 years now. I know when he got arrested that last time in Perth he did have various prescription meds on him, can't remember what though. As an elite sportsman in his 30s he's probably been administered plenty of pain medication over his career as well.