Open Access 11-04-2025 | Fibromyalgia | Original Research Article

Effect of Naltrexone on Spinal and Supraspinal Pain Mechanisms and Functional Capacity in Women with Fibromyalgia: Exploratory Outcomes from the Randomized Placebo-Controlled FINAL Trial

Authors: Karin Due Bruun, Robin Christensen, Kirstine Amris, Morten Rune Blichfeldt-Eckhardt, Lars Bye-Møller, Marius Henriksen, Tine Alkjaer, Palle Toft, Anders Holsgaard-Larsen, Henrik Bjarke Vaegter

Published in: CNS Drugs

Abstract

Background

The widespread pain and muscular fatigue characteristics of fibromyalgia are believed to be mediated by central mechanisms. Low-dose naltrexone (LDN) has emerged as a new treatment option for fibromyalgia, possibly modulating central mechanisms via glial or opioid receptors.

Methods

In the randomized, placebo-controlled FINAL trial, 99 women with fibromyalgia were treated with LDN or placebo for 12 weeks. In this secondary analysis, we examined the potential effects of LDN versus placebo on changes from baseline in pain tolerance, temporal summation of pain, and conditioned pain modulation (CPM) in the complete case population (45 versus 47 participants). Measures of muscular fatigue were evaluated using the 30-s chair stand test and a shoulder abduction test.

Results

Of the five examined outcomes, only change in CPM showed a significant between-group difference with greater enhancement following LDN treatment (2.0 kPa; 95% confidence interval (CI) 0.4–3.7 kPa) compared with placebo. Within-group changes in CPM showed an increase of 1.2 kPa (95% CI 0.05–2.4 kPa) in the LDN group and a possible decrease of 0.8 kPa (95% CI − 1.9 to 0.4 kPa) in the placebo group.

Conclusions

We found a significant between-group difference in CPM change in favor of LDN. However, this difference was partly explained by a decrease in CPM in the placebo group. Sensitivity analyses showed no association between changes in CPM and clinical pain improvement, suggesting that the group-difference in CPM is a random finding.

Study Registration

ClinicalTrials.gov (NCT0427877; registered on 30 January 2020).

Available only for authorised users

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Title: Effect of Naltrexone on Spinal and Supraspinal Pain Mechanisms and Functional Capacity in Women with Fibromyalgia: Exploratory Outcomes from the Randomized Placebo-Controlled FINAL Trial
Authors: Karin Due Bruun
Robin Christensen
Kirstine Amris
Morten Rune Blichfeldt-Eckhardt
Lars Bye-Møller
Marius Henriksen
Tine Alkjaer
Palle Toft
Anders Holsgaard-Larsen
Henrik Bjarke Vaegter
Publication date: 11-04-2025
Publisher: Springer International Publishing
Keywords: Fibromyalgia
Fibromyalgia
Naltrexone
Published in: CNS Drugs
Print ISSN: 1172-7047
Electronic ISSN: 1179-1934
DOI: https://doi.org/10.1007/s40263-025-01183-7

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