I used to attend a medical pain conference once a year that lasted a whole day with many topics.

One year they provided a detailed update on the research for fibromyalgia patients. The gist was that it has been discovered that fibro patients make MORE endorphin molecules in response to pain, and that these sit on the receptors, and that is why opiates don't work well on fibro pain, because these endorphins (which are natural opiates) are blocking those receptors.

Naltrexone is known to bump off opiates from receptors so it is that mechanism which could increase pain perception.

The deal is that this theory is difficult to prove and even structuring a study for this is very difficult because it is occuring in the brain. So far researchers rely on clinical observations to understand what is happening.

The fact that you have a ceiling...where when you use a certain higher dose, you experience more pain, suggests that the LDN is working to alter your receptor activity.

The suggested theory is that LDN affects the immune expression in the brains of those taking it...this is an activity that wasn't known when the drug was developed. The usual dose of Naltrexone is 50mg a day or more. Compare that to LDN's dose. You'll see that something is happening at that very low LDN that is different than the high normal dose.

Since everyone is different, and has a different experience with opiates, there will be different responses to LDN. The studies do not yet explain if people who used long term opiates, lose the extra receptors that resulted from that use, we just don't know all the answers to your questions yet. It has been suggested though that those extra receptors may explain why addicts have high rates of failure to kick their opiate habits. Many return to "using" after treatment ends. Much of the research is done on addiction treatment at this time. And while "addicts" are the main avenue of information learned about opioid receptors so far, there are many others who are not addicts, but have used opiates for years, and may show some similarities on the receptor level.

There are many drugs in use today that ALTER receptors that they work on. SSRIs, and benzodiazepines are examples that show a habituation problem and require careful tapers, and have unpleasant withdrawal symptoms when removed. Opiates I think are just another form of this phenomenon.