In April 2009 I told you about a pilot study in which low-dose naltrexone (LDN) showed great promise as a fibromyalgia treatment. Then in March 2012, I reported on a slightly larger low-dose naltrexone study that had even better results for patients with fibromyalgia. Today I have news of yet another positive study using low-dose naltrexone for the treatment of fibromyalgia, published in the February 2013 issue of Arthritis and Rheumatism.
Naltrexone is an opioid receptor antagonist and is FDA approved for the management of alcohol and opioid addiction. When used for addiction, naltrexone works by latching onto the body's opioid receptors and blocking their ability to induce a feeling of being high. However, its effectiveness at low doses with fibromyalgia is not due to its opioid antagonistic effects but is thought to be related to its ability to stifle an immune response which causes inflammatory cytokines to be released.
Study Design and Results
Thirty-one women with fibromyalgia participated in this latest randomized, double-blind, placebo-controlled, counterbalanced, crossover study. During the active drug phase of the trial, participants received 4.5 mg of oral naltrexone daily.
Researchers found that:
When patients took the low-dose naltrexone, they experienced a 29% reduction in their baseline pain.
Overall, low-dose naltrexone was associated with improved general satisfaction with life and improved mood but not with improvement in fatigue or sleep.
However, 32% of participants met the criteria for response (defined as a significant reduction in pain plus a significant reduction in either fatigue or sleep problems).
Low-dose naltrexone was rated equally tolerable as the placebo, and no serious side effects were reported.
The study authors concluded, “The preliminary evidence continues to show that low-dose naltrexone has a specific and clinically beneficial impact on fibromyalgia pain. The medication is widely available, inexpensive, safe, and well-tolerated. Parallel-group randomized controlled trials are needed to fully determine the efficacy of the medication.”
Although all three studies are relatively small, the repeated positive results are encouraging. As with most medications tested for fibromyalgia, low-dose naltrexone seems to help around 30-40% of FM patients.
While I would like to see much larger clinical trials on low-dose naltrexone and even its eventual approval by the FDA for the treatment of FM, it's unlikely that either will happen. Large clinical trials are extremely expensive and are usually conducted by pharmaceutical companies, who expect to be able to recoup their costs by charging high prices for a number of years once a drug receives FDA approval. The problem with naltrexone is that it's already available as an inexpensive generic drug so there is zero incentive for pharmaceutical companies to invest in extensive (and expensive) clinical trials.