Naltrexone, a drug used to treat opioid addiction, is being used off-label to treat pain in Fibromyalgia and other chronic conditions. There are few studies on this, because naltrexone is a generic drug, so no pharma company can make money from it.
A small Stanford study on Low-Dose Naltrexone (LDN) found that 6 out of 10 fibromyalgia patients experienced significant reduction in their symptoms on LDN compared to placebo.
This finding is confirmed at CureTogether, where 26 out of 44 fibromyalgia patients report a major improvement in their symptoms after taking LDN. In fact, LDN is ranked as the #1 most effective treatment for fibromyalgia at CureTogether (see the screenshot below.)
Larger studies still need to be done, but it is remarkable that the CureTogether ratio of improvement on LDN is 59% (26/44), and the Stanford ratio of improvement on LDN is 60% (6/10). The same result!