Low-Dose Naltrexone in Chronic Pain Management: Mechanisms, Evidence, and Clinical Implications

Chronic pain imposes a substantial burden on global health and remains challenging to manage, despite ongoing advances in pharmacologic and interventional therapies. Recognition of chronic pain as a condition driven by central sensitization and neuroimmune dysregulation has prompted interest in therapies that target these mechanisms rather than peripheral nociception alone. Low-dose naltrexone (LDN), administered at doses substantially lower than those used for opioid or alcohol use disorders, has emerged as a repurposed treatment with potential analgesic and anti-inflammatory properties. This review summarizes the pharmacologic characteristics of LDN, with emphasis on its proposed mechanisms involving transient opioid receptor blockade, modulation of microglial activation, Toll-like receptor signaling, and central neuroimmune pathways. Available clinical evidence evaluating LDN across a range of chronic pain conditions, such as fibromyalgia, neuropathic pain syndromes, inflammatory and autoimmune disorders, headache disorders, and other centralized pain states, is critically reviewed. Although early trials, observational studies, and case series suggest potential benefit in selected populations, the overall evidence base remains limited, heterogeneous, and characterized by variability in dosing strategies and outcome measures. Safety, tolerability, and practical considerations relevant to contemporary pain practice are discussed, including interactions with opioid therapy and challenges related to off-label use. Finally, key gaps in the current evidence and priorities for future research are highlighted, underscoring the need for larger, well-designed randomized trials and mechanism-informed studies to better define LDN's role in multimodal chronic pain management.