The effect of naltrexone in this context occurs because it blocks the heroin etc from attaching to the opioid receptors in the brain and elsewhere; it attaches to these receptors itself, but does not have the same effect as the opiate.

Over 20 years ago, Dr Bernard Bihari, a physician in New York, found that a very low dose of naltrexone had a dramatic effect on the immune system, which could be useful in HIV/AIDS; he went on to apply it to auto-immune disease such as MS. What seems to happen is that when the naltrexone blocks the opioid receptors, the body responds by producing large amounts of chemicals known as endorphins.

Endorphins are known to produce feelings of well-being, even exhilaration, and to relieve or block pain. They are produced when you experience pain, are under severe stress, or feel the proximity of death. The obvious effect is to enable you to keep going when you would otherwise have to give up.

LDN is taken last thing at night, and is only around to block the opioid receptors for a few hours, but it appears to cause an increase in endorphins that lasts much longer. From there on things are less clear, and we would have to say that we don’t know how it works. There are lots of hints, though, starting with the fact that immune cells have receptors for endorphins.