hi elcamino,
You are a hundred percent right--naltrexone has been used in 50-300 mg. dosages to help people trying to kick heroin and other opiate drug addictions, and the drug has been on the market for about thirty years. (It's now generic.)
The dose used to treat autoimmune and other disorders is much smaller; only 3-4.5 mg., thus the moniker "low-dose naltrexone", or LDN.
When the drug was in clinical trials, it wasn't known that it could help people with autoimmune disorders (as well as some other health conditions, including some cancers), so any prescription for those conditions is considered "off-label", which is perfectly legal. However, many doctors don't know about this use, so finding one who will prescribe it can be a challenge.
In addition, because the smallest strength the pill is produced in is 50 mg., once you find a physician willing to write a prescription, that prescription will need to be sent to a compounding pharmacy to have them make up capsules with the smaller dosage. I have a list (and can provide a link to it) of compounding pharmacies in the U.S.--there are several. They will just mail you the capsules after they make them up.
I already get my current medications by mail, so that's no big deal. I see a new doctor in about ten days, so I'm going to take her some info about LDN, then make a follow-up appointment to see what she thinks. I've ordered a book about LDN from Amazon.com (there are at least three books on the subject), so I'm going to let my new doc read the book after I finish it, if she's interested.
I've read that there are now some clinical trials going on, so maybe this drug will soon be more well-known by doctors, and will then be produced in the lower 3-4.5 mg. strengths.
I'm trying not to get too excited about this, but it's hard...a cheap ($35/mo.) drug that's worst side effect is vivid dreams? Comparing that to Enbrel and methotrexate's "lymphoma, fatal blood diseases", etc...if this works, how much of a Godsend would it be to the millions of people who suffer from autoimmune diseases?!
I'll post after I have my doctor appointment to share what happens, in case anyone's interested.
Blessings!