Well, it is supposed to increase your body's endorphins. There was a recent published study that it helps with Crohn's disease, and a lot of anecdotal evidence that it helps with MS, Lupus and other autoimmune diseases.
Naltrexone is an opiod blocker and is used at full strength for those addicted to opiates. The theory is that for AI diseases, your body doesn't produce enough endorphins on its own. This leads to inflammation and AI disease. LDN (Low Dose Naltrexone) works like this: Your body normally produces most of its endorphins between 2-4 AM. If you take a very small dose of Naltrexone before going to bed, it blocks the opioid receptors in your brain. This is turn makes your body think you don't have enough endorphins, so it ramps up production on its own for a few hours. This extra endorphin that is now in your system stops AI reactions.
That's the theory, anyway.
Here's a site that list users experiences taking it:
Not a heck of a lot yet on Lupus, but anecdontal evidence is encouraging. It seems to help a lot of autoimmune diseases, but the only peer reviewed paper so far is for Crohn's. There are a few trials underway right now.
If you read that last article, you can see that at least in mice with lupus-like disease, low endorphins have been found.
It's all experimental right now. However, the drug is available for any doc to prescribe off-label right now, if you find one that is willing to give it a try. That site I gave describes the protocol. It is 3-4.5 mg once a day around 10 PM.
I haven't taken it myself. I'm still in the research phase.