Well, hello, this looks promising. Must remember to ask doctor about it this week! Searched PubMed though, no journal articles or studies done on it and CFS, hmm...
Site with more information low-dose naltrexone: http://www.ldninfo.org/
So supposedly it's been used to fight addiction in the past. Interacts with opioid receptors. But also boosts the immune system?? What the what? I'm a bit excited.
Edit: OK, in further reading people's responses about this, it seems that your symptoms reappear if you stop taking it. That makes me a bit skeptical. I usually don't like any sort of drugs (chemicals = bad, in my mind). Granted, that makes it hard to treat this so I've had to bite the bullet and ignore that instinct. In an ideal world, I'd take drugs that aren't supposed to be taken forever but rather that work -with- my body to help itself, versus pushing it along so that when I stop taking it, I regress. But that's in an ideal world not the one I actually live in, so I might just have to deal with it and take whatever works.