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Low-dose naltrexone (LDN) significantly reduces pain and improves functional outcomes among patients with fibromyalgia while maintaining a favorable safety profile, according to study results presented at the American College of Rheumatology (ACR) Convergence 2025, held from October 24 to 29, in Chicago, IL.
Fibromyalgia is a chronic pain syndrome characterized by musculoskeletal pain and fatigue, significantly impacting daily function and quality of life. Current treatment options often provide limited relief, prompting interest in alternative therapies such as LDN — which may act through neuroimmune modulation and enhancement of endogenous opioid activity. Given the lack of robust randomized evidence, researchers performed a systematic review and meta-analysis to better define the therapeutic role and safety of LDN for fibromyalgia.
The analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and included randomized controlled trials (RCTs) published through December 2024. A random-effects model was used to pool standardized mean differences (SMDs) and odds ratios (ORs) across studies assessing pain severity, functional status, and adverse events.
Five RCTs met inclusion criteria. Compared with placebo, LDN significantly lowered pain scores (pooled SMD, -0.851; 95% CI, -1.290 to -0.412) and improved functional outcomes measured by the Fibromyalgia Impact Questionnaire Revised (SMD, -0.978; 95% CI, -1.926 to -0.030). The pressure pain threshold also improved modestly, but significantly (SMD, 0.136; 95% CI, 0.071-0.202).
Results of safety analyses indicated that vivid dreams occurred more often with LDN (OR, 2.17; 95% CI, 1.17-4.02), whereas the risks for headache (OR, 1.41; 95% CI, 0.76-2.60) and nausea (OR, 1.40; 95% CI, 0.81-2.43) did not differ significantly from placebo. No major safety signals were identified, and heterogeneity across outcomes was low to moderate.
“[Low-dose naltrexone’s] unique dual mechanism—enhancing endogenous opioids while reducing neuroinflammation—addresses key pathophysiologic processes in fibromyalgia that are largely unaddressed by current therapies,” the study authors concluded.
