TOPLINE:
Women with fibromyalgia who received low-dose naltrexone showed no significant improvement in pain at 12 weeks, compared with those who received placebo in a randomized trial.
METHODOLOGY:
- The researchers randomly assigned 99 women with fibromyalgia at a single center in Denmark to a daily dose of 6 mg of naltrexone or a placebo for 12 weeks.
- The primary outcome was within-group change in pain intensity from baseline to 12 weeks, measured using an 11-point numeric rating scale (NRS) and the Fibromyalgia Impact Questionnaire-Revised (FIQR); outcomes were measured at 4, 8, and 12 weeks.
- Secondary outcomes included the global impact of FIQR total scores, as well as FIQR scores for tenderness, fatigue, sleep disturbance, depression, anxiety, memory, stiffness, and physical function.
TAKEAWAY:
- The patients ranged in age from 18 to 64 years, with a mean age of 50.6 years, and all but one was White.
- At 12 weeks, the mean change in pain intensity was greater in the naltrexone group compared with the placebo group (−1.3 points vs −0.9 points, respectively), but the difference was not statistically significant.
- Of the secondary outcomes, only memory problems related to fibromyalgia showed significant improvement with naltrexone compared with placebo (−0.93 vs −0.30; P = .004), although the significance was lost after adjusting for multiplicity.
- Adverse events were infrequent and similar between the groups; four of 49 patients in the naltrexone group and three of 50 in the placebo group discontinued their assigned treatments because of side effects, and no safety concerns appeared related to the 6-mg dose.
IN PRACTICE:
"At this time we recommend that off-label treatment of patients who have responded to low-dose naltrexone should not be terminated, but we recommend against initiating low-dose naltrexone for low-dose naltrexone-naive patients with fibromyalgia pending the results of additional adequately powered studies with distinctive inflammatory and autoantibody patient profiles," Winfried Häuser, MD, of the Center for Pain Medicine and Mental Health, Saarbrücken, Germany, and Mary-Ann Fitzcharles, MD, of McGill University Health Centre, Montreal, Canada, wrote in an accompanying editorial.
SOURCE:
The lead author of the study was Karin Due Bruun, MD, of Odense University Hospital, Denmark. The full study and accompanying editorial were published online in The Lancet Rheumatology on December 5.
LIMITATIONS:
The study was only powered to detect a difference of 1.0 NRS points for pain intensity; other limitations include the homogenous population that prevents generalizability to other groups and the relatively short follow-up period.
DISCLOSURES:
The study was supported by the Danish Rheumatism Association, Odense University Hospital, Danielsen's Foundation, and the Oak Foundation. The researchers had no financial conflicts to disclose.
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