Results of a small pilot study from the Stanford University School of Medicine investigating the effects of a drug called naltrexone show positive signs for those with fibromyalgia. During the study, naltrexone, a drug used clinically to treat opioid addiction for more than 30 years, reduced symptoms of pain and fatigue an average of 30% over placebo.

“Patients’ reactions were really quite profound,” says senior author Sean Mackey, MD, PhD, chief of the pain management division at Stanford University Medical Center. “Some people decided to come off other medications. Some people went back to work, really improving their quality of life.”

Interestingly, at normal doses naltrexone blocks the body’s pain relief systems, which seems counterintuitive for the treatment of fibromyalgia; the drug appears to have the opposite effect when administered at a lower dose, however.

Researchers recruited 10 women with fibromyalgia for the 14-week study. Throughout the study, the women used a handheld electronic device to capture symptoms on a daily basis. The women took a placebo during a portion of the study and naltrexone for another portion, but were not aware of which they were taking at any time.

The low cost of the drug ($40 per month) and its limited side effects make it particularly promising as a fibromyalgia treatment, according to study authors, although Mackey remains cautious about recommending the drug this early in the research process.

“People need to understand that while we’re excited about preliminary results, they are still preliminary, and we need to do longer studies with more patients. There is still a significant amount of work to be done,” he says.

According to the study’s lead author, Jarred Younger, PhD, some of the women in the study continued to take the drug after the completion of the study because the results were so positive. The researchers are moving forward with a second, longer-term trial of 30 patients.

Study results appear in the journal Pain Medicine.

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