Low-Dose Naltrexone, an Opioid-Receptor Antagonist, is a Broad-Spectrum Analgesic: A Retrospective Cohort Study

Abstract

Aim: To evaluate the use of low-dose naltrexone (LDN) as a broad-spectrum analgesic. Methods: Retrospective cohort study from a single pain management practice using data from 2014 to 2020. Thirty-six patients using LDN for ≥2 months were matched to 42 controls. Pain scores were assessed at initial visit and at most recent/final documented visit using a 10-point scale. Results: Cases reported significantly greater pain reduction (-37.8%) than controls (-4.3%; p < 0.001). Whole sample multivariate modeling predicts 33% pain reduction with LDN, with number needed to treat (for 50% pain reduction) of 3.2. Patients with neuropathic pain appeared to benefit even more than those with ‘nociceptive’/inflammatory pain. Conclusion: LDN is effective in a variety of chronic pain states, likely mediated by TLR-4 antagonism.

Plain language summary

Naltrexone has historically been used to treat various substance use disorders, but recent discoveries have sparked interest in using low-dose naltrexone (LDN) to manage chronic pain. This study compared pain levels reported by patients before and after at least 2 months of LDN treatment to those reported by patients with the same painful diseases, who did not take LDN. Overall, patients who took LDN reported significantly more pain relief than patients who did not take LDN. How LDN alleviates pain seems complex, but apparently involves an anti-inflammatory effect on cells in the brain and spinal cord. LDN is extraordinarily safe, with no known risks (unlike most standard pain medications), and should be studied more in the treatment of chronic pain.

Keywords::

• central sensitization
• chronic pain
• low-dose naltrexone
• opioid-induced hyperalgesia
• TLR-4

Acknowledgments

The authors would like to thank M Hutchinson for his review and expert critique of the manuscript.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.