Low-Dose Naltrexone Improved Memory but Not Pain in Women With Fibromyalgia

Low-Dose Naltrexone Improved Memory but Not Pain in Women With Fibromyalgia
Lisa Kuhns, PhD | January 18, 2024
Clinical Pain Advisor
https://www.clinicalpainadvisor.com/interventional-pain-management/low-dose-naltrexone-improved-memory-but-not-pain-in-women-with-fibromyalgia/

Low-dose naltrexone may improve memory problems associated with fibromyalgia but the drug was not effective in relieving pain, according to study results published in Lancet Rheumatology.

Two previous studies with crossover designs indicated that naltrexone might be more effective than a placebo in reducing pain intensity in women with fibromyalgia, but they were small and potentially biased. However, in June 2023, a new crossover trial did not show any analgesic effect of low-dose naltrexone vs a placebo.

In an effort to resolve uncertainty regarding analgesic effects of naloxone in fibromyalgia, researchers at a tertiary pain rehabilitation center in Denmark conducted the Fibromyalgia and Naltrexone (FINAL) study, a single-center, randomized, double-blind, placebo-controlled superiority trial. Their primary objective was to determine whether a 12-week treatment with naltrexone 6 mg was superior to placebo in reducing average pain intensity during the past 7 days in women with fibromyalgia (as measured by the Numeric Rating Scale [NRS] score from the level of pain question in the Fibromyalgia Impact Questionnaire-Revised questionnaire). Secondary objectives included evaluation of core fibromyalgia domains such as nonpain symptoms, daily functioning, health-related quality of life, global impression of change, and responder indices.

Eligible for inclusion in FINAL were women aged 18 to 64 years with fibromyalgia and no history of neurologic disease, inflammatory rheumatic disease, or active cancer. Study participants were recruited from January 6, 2021 to December 27, 2022. Included were 99 patients, 49 of whom were assigned to treatment with low-dose naltrexone and 50 of whom were assigned to placebo. Nearly all (99%) were White and mean patient age was 50.6 years. All patient-reported outcomes were assessed using a repeated measures design at baseline and after 4, 8, and 12 weeks of treatment.

Average reduction in pain intensity was -1.3 points on the NRS (95% CI, -1.7 to -0.8) in the low-dose naltrexone group and -0.9 points in the placebo group (95% CI, -1.4 to -0.5). This difference was insignificant, with a between-group difference of -0.34 NRS points (95% CI, -0.95 to 0.27; P =.27), corresponding to a Cohen’s d of 0.23. Nor was a significant difference observed between the groups for most secondary outcomes. However, a significant difference in memory problems that favored low-dose naltrexone was found between the 2 groups (-0.93; 95% CI, -1.57 to -0.30; P =.004) across all the secondary continuous outcomes.

Editors note: Had they used a reasonable dosing schedule, rather than putting all subjects on 6 mg LDN, they may have had a different conclusion. Dose protocols for Fibromyalgia, and many other conditions, vary for each individual.  For more information on the use of LDN for fibromyalgia see this Q&A by LDN Specialist Michelle Moser here.