Non-addictive pain killers / drug addiction

[Solitude]

I came across this article posted on fark, and it triggered some memory from irc the other day. People were asking about why there are no good non-addictive pain killers. There are a lot of companies looking to develop just that type of drug.

Anyhoo, the conversation in irc reminded me of something that I couldn't totally recall at the time. That word.. is.. dopamine.
Um.. Ok. This still doesn't explain anything or further the conversation, but check out this article. I think it's a very interesting, quick read.

Epilepsy drug 'combats addiction'

Can any of you remember the chemical connection between pain-killers and addiction? Also, why is this connection so hard to break?