Pain Processing:

How Melatonin Impacts Pain Processing

For most people, melatonin is a compound used for insomnia. It is in fact, much more than that. It offers as many mechanisms for improvement of pain, particularly related to the processing of pain in the nervous system.

 

See:

     How Nutraceuticals Impact Pain Processing

  1. How Acetyl-L-Carnitine (ALC) Impacts Pain Processing
  2. How Alpha-Lipoic Acid (ALA) impacts pain processing
  3. How Boswellia Impacts Pain Processing
  4. How CoQ10 Impacts Pain Processing
  5. How Curcumin Impacts Pain Processing
  6. How Magnesium Impacts Pain Processing
  7. How Melatonin Impacts Pain Processing
  8. How Omega-3 fatty acids (EPA and DHA) Impact Pain Processing
  9. How N-Acetyl Cysteine (NAC) Impacts Pain Processing
  10. How Nicotinamide Riboside (NR) Impacts Pain Processing
  11. How PEA (Palmitoylethanolamide) Impacts Pain Processing
  12. How Quercetin Impacts Pain Processing
  13. How Resveratrol Impacts Pain Processing
  14. How Sulforaphane (SFN): Impacts Pain Processing
  15. How Taurine Impacts Pain Processing

 

 

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Definitions and Terms Related to Pain

 

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Melatonin: Pain Processing Effects vs. Direct Tissue-Modifying Effects

How Melatonin Impacts Pain Processing

Overview

Melatonin is a compound primarily synthesized by the pineal gland that has emerged as a multifaceted modulator of pain processing. Beyond its well-known diurnal rhythm functions, melatonin exerts analgesic effects through specialized, melatonin receptors, MT1 and MT2, G-protein coupled receptors distributed throughout the brain and spinal cord, with MT2 receptors playing a particularly prominent role in analgesia.[1][2]

Uniquely among nutraceuticals, melatonin is also synthesized within mitochondria themselves, positioning it as an endogenous mitochondrial protectant with direct access to this organelle.[3]

This pathway-level analysis examines how melatonin therapeutically impacts pain processing at each level while also addressing the four pathological processes central to the Pain Processing treatment paradigm: Systemic Inflammation, Neuroinflammation, Oxidative Stress and Mitochondrial Dysfunction.

The Levels of Pain Processing can be organized as follows:

  • Level 1: Peripheral Nociception (Pain Receptor Transduction):Activation and Sensitization
  • Level 2: Primary Afferent Transmission to Spinal Cord
  • Level 3: Spinal Cord Dorsal Horn Processing (First Synapse)
  • •Level 4: Ascending Spinal Pathways and Supraspinal Processing
  • Level 5: Thalamic and Cortical Processing and Pain Perception
  • Level 6: Descending Pain Modulation

—

Level 1. Peripheral Nociception (Primary Afferent Neurons and DRG)

Mechanisms:

  1. At the peripheral level, melatonin modulates nociceptor function through several mechanisms. In dorsal root ganglion (DRG) neurons, melatonin upregulates SIRT1 expression, which drives downstream mitochondrial protection and anti-inflammatory effects.[4] Specifically, melatonin treatment restores injury-dependent decreases in mitochondrial membrane potential and PGC-1α (the master regulator of mitochondrial biogenesis) while reducing hydrogen peroxide and 8-hydroxy-2-deoxyguanosine (8-OHdG, a marker of oxidative DNA damage) in DRG neurons following nerve injury.[4]
  2. Melatonin also modulates the nitroxidergic system at the peripheral level. Single administration of melatonin (5-10 mg/kg) in neuropathic rats modulates neuronal and inducible nitric oxide synthase (nNOS and iNOS) expression in both DRG and skin, reducing thermal nociceptive hypersensitivity within 30 minutes of administration.[5]
  3. In radiculopathy models, melatonin promotes Parkin-mediated mitophagy in DRG cells, which inhibits NLRP3 inflammasome activation and reduces apoptosis. This mitophagy-dependent mechanism alleviates radicular pain by clearing damaged mitochondria and preventing inflammasome-driven neuroinflammation.[6]

Relevance to Pathological Targets:

  • Mitochondrial dysfunction: Restores mitochondrial membrane potential and PGC-1α via SIRT1 activation
  • Oxidative stress: Reduces H₂O₂ and 8-OHdG in DRG neurons
  • Neuroinflammation: Inhibits NLRP3 inflammasome via Parkin-mediated mitophagy

—

Level 2. Spinal Cord Dorsal Horn Processing

Melatonin exerts potent effects on spinal cord pain processing through multiple mechanisms. MT2 receptors are expressed in the dorsal horn of the spinal cord and are upregulated following nerve injury, co-localizing with both neurons and microglia.[7]

  1. 1Central sensitization inhibition: In lumbar disc herniation models, melatonin decreases C-fiber evoked field potentials (a direct measure of spinal synaptic transmission), reduces spinal NR2B (NMDA receptor subunit) protein levels, and decreases expression of CGRP and IB4 (markers of peptidergic and non-peptidergic nociceptive afferents, respectively).[7] These effects are mediated through MT2 receptors, as both broad-spectrum MT antagonists and MT2-specific antagonists abolish melatonin’s effects.
  2. Epigenetic modulation: Melatonin relieves neuropathic allodynia through a novel MT2-dependent epigenetic mechanism involving PP2Ac (protein phosphatase 2A catalytic subunit) and HDAC4 (histone deacetylase 4). Specifically, melatonin increases PP2Ac expression, promotes HDAC4 dephosphorylation and nuclear accumulation, which then suppresses HMGB1 (high-mobility group box 1) gene transcription in dorsal horn neurons.[8] HMGB1 is a damage-associated molecular pattern (DAMP) that drives neuroinflammation. Additionally, melatonin impedes Tet1-dependent demethylation of the mGluR5 promoter, reducing mGluR5 expression in dorsal horn neurons.[9] Since mGluR5 contributes to central sensitization, this epigenetic suppression represents a novel mechanism for melatonin’s anti-hyperalgesic effects.
  3. Glial modulation: In demyelination neuropathy models, melatonin reduces glial activation (both astrocytes and microglia) in the cuneate nucleus through MT2 receptor-dependent inhibition of MAPK pathways (ERK, JNK, p38), decreasing pro-inflammatory cytokine release.[10]
  4. Sex-dependent mechanisms: Recent evidence demonstrates that spinal melatonin’s antiallodynic effects are sex–dependent. While MT2 receptor activation mediates effects in both sexes, the magnitude is significantly greater in females. In males, spinal opioid receptor activation plays a more prominent role, whereas in females, the effects depend on estrogen receptor-α activation.[11]

Relevance to Pathological Targets:

  • Neuroinflammation: Suppresses HMGB1 via epigenetic mechanisms; inhibits glial MAPK activation
  • Oxidative stress: Reduces ROS through Nrf2 pathway activation
  • Systemic inflammation: Decreases spinal pro-inflammatory cytokines (TNF-α, IL-1β, IL-18)

Level 3. Ascending Pathways and Thalamic Processing

Mechanisms:

  1. MT2 receptors are localized in specific brain areas critical for ascending nociceptive transmission, including the reticular and ventromedial nuclei of the thalamus.[1] These thalamic nuclei are integral components of the spinothalamic tract and medial pain system, which convey nociceptive information to cortical areas for pain perception.
  2. Melatonin receptor activation in these regions leads to reduced cyclic AMP formation through Gi-protein coupling, which decreases neuronal excitability and nociceptive transmission.[2] The presence of MT receptors in the thalamus, hypothalamus, and trigeminal nucleus aligns with melatonin’s documented efficacy in conditions involving these structures, such as migraine and cluster headache.[2]

Relevance to Pathological Targets:

  • Neuroinflammation: Thalamic neuroinflammation modulation through receptor-mediated signaling

Level 4. Supraspinal Processing and Descending Modulation

Mechanisms:

1. Perhaps the most distinctive aspect of melatonin’s analgesic profile is its robust modulation of descending antinociceptive pathways—a mechanism not prominently featured among other nutraceuticals.

Periaqueductal gray (PAG) mechanisms: MT2 receptors are expressed by glutamatergic neurons in the rostral ventrolateral periaqueductal gray (vlPAG), a critical structure in descending pain modulation.[12] Microinjection of selective MT2 agonists (UCM924) into the vlPAG produces several effects:

    1. Decreased tail flick responses (indicating analgesia)
    2. Depressed firing activity of pronociceptive ON cells in the rostral ventromedial medulla (RVM)
    3. Activated firing of antinociceptive OFF cells in the RVM[12]

All these effects are MT2 receptor-dependent, as they are blocked by selective MT2 antagonists.

2. Opioid system recruitment: The MT2-mediated analgesic circuit requires mu opioid receptors (MOR) to exert its full antiallodynic effects. Pharmacological blockade or genetic inactivation of MOR (but not delta opioid receptors) nullifies the antiallodynic effects of MT2 agonists.[13] Importantly, MT2 agonist treatment increases enkephalin precursor gene (PENK) expression in the PAG, suggesting that melatonin enhances endogenous opioid tone.[13] Only ~0.20% of vlPAG neurons co-express both MOR and MT2 receptors, indicating that the interaction occurs through an interneuronal circuit rather than direct receptor co-localization.

3. Morphine Synergy: Melatonin co-administration with morphine attenuates morphine tolerance and enhances morphine analgesia while reducing pro-inflammatory cytokines and suppressing astrocyte activation.[14] This has significant clinical implications for opioid-sparing strategies.

Relevance to Pathological Targets:

    1. Neuroinflammation: Reduces PAG neuroinflammation; suppresses astrocyte activation during opioid tolerance
    1. Systemic inflammation: Decreases pro-inflammatory cytokines in supraspinal structures

Level 5. Cortical Processing and Pain Perception

Mechanisms:

Melatonin’s effects on cortical pain processing are mediated through both direct receptor actions and indirect effects on sleep, anxiety, and circadian regulation. MT receptors are present in cortical regions, and melatonin’s anxiolytic and sleep-promoting effects may indirectly reduce pain perception by modulating the affective-motivational dimension of pain.[15]

The time of day-related effects of melatonin are particularly relevant given that pain intensity in many chronic pain conditions (including neuropathic pain) is often worse at night, coinciding with disrupted circadian rhythms and reduced endogenous melatonin secretion.[16] By restoring circadian alignment, melatonin may normalize pain processing rhythms.

Relevance to Pathological Targets:

  • Neuroinflammation: Cortical microglial modulation through circadian regulation

 

Systemic Inflammation, Neuroinlammation, Oxidative Stress and Mitochondrial Dysfunction

Systemic Inflammation, Neuroinflammation, Oxidative Stress and Mitochondrial Dysfunction are 4 pathological processes/conditions that contribute to chronic pain by creating a cycle of tissue damage, immune cell activation, and pain amplification. By disrupting normal cellular physiology, these conditions also contribute to the development and progression of chronic diseases, including diabetes, heart disease, stroke, chronic kidney and liver disease, rheumatoid arthritis, cancer and Alzheimer’s.

  1. Systemic inflammation (SI) is a widespread inflammatory response throughout the body, triggered by infection, injury, stress and other conditions. It involves activation of the immune system with the release of pro-inflammatory compounds that contribute to chronic pain and lead to other health issues. Symptoms of SI include increased pain, fatigue, cognitive problems, depression, decreased motivation for physical activity and, in severe cases, organ dysfunction. While inflammation is a natural part of the healing process, chronic or excessive SI contributes to the development of heart disease, diabetes, and autoimmune disorders like rheumatoid arthritis.
  2. Neuroinflammation (NI), a component of systemic inflammation, is inflammation within the central nervous system (brain and spinal cord). SI releases inflammatory compounds that cross into the brain and spinal cord that activate immune cells causing NI and contributes to the progression of acute to chronic pain. NI is characterized by activation of immune cells (glial cells and astrocytes) in the nervous system that release inflammatory chemicals like cytokines, proteases, and free radicals such as reactive oxygen (ROS), and nitrogen species (RNS). When these immune cells remain activated, neuroinflammation persists and drives chronic pain.
  3. Oxidative stress (OS) is an imbalance of excessive “oxidants” (“oxidizing” or chemically active agents (including ROS and NOS) obtained from the diet or produced by the body coupled with insufficient “antioxidants,” the compounds that neutralize oxidants. Excessive oxidants damage nerve cells and other tissues causing and maintaining pain. Antioxidants are manufactured by the body, but sufficient dietary intake of antioxidants is critical for good health. OS and chronic SI co-exist and feed each other, damaging tissues in a vicious cycle that further worsens pain.
  4. Mitochondrial Dysfunction (MD). Mitochondria are organelles found in cells that function as the “power stations” of cells in that they process food into energy. In addition to providing energy, they play a major role in maintaining antioxidants to combat OS and SI. Because mitochondria impact the metabolism of all cells, they play a huge role in general health. Impairment of mitochondrial function (dysfunction) contributes to many conditions including chronic pain, obesity, migraines, fibromyalgia, diabetes, heart disease and neurodegenerative diseases like Alzheimers.

In MD, energy production goes down and fatigue develops along with impaired physical functioning, even if more calories are ingested. MD is the hallmark of conditions such as obesity and fibromyalgia. Mitochondrial dysfunction leads to the metabolic impairment that is found in many chronic diseases including depression, bipolar disorders and premature aging.

Integration of Pain Processing with the 4 Pathological Processes

1. Systemic Inflammation

Melatonin inhibits the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-18) through multiple mechanisms including NF-κB inhibition and NLRP3 inflammasome suppression.[17] In spinal nerve ligation models, intraperitoneal melatonin significantly attenuates SNL-induced upregulation of TNF-α, IL-18, IL-1β, NLRP3, ASC, and cleaved caspase-1 in the lumbar spinal cord.[17] Melatonin also inhibits expression of 5-lipoxygenase and cyclooxygenase-2, reducing eicosanoid-mediated inflammation.[2]

2. Neuroinflammation

Melatonin’s effects on neuroinflammation are particularly well-characterized. In activated microglia, melatonin:

  • Inhibits NF-κB activity and reduces pro-inflammatory mediators
  • Promotes M2 (anti-inflammatory) microglial polarization at the expense of M1 (pro-inflammatory) phenotype[18][19]
  • Enhances phospho-AhR (aryl hydrocarbon receptor) activation and increases Nrf2 expression through the AhR/Nrf2/ARE pathway[20]
  • Increases BDNF expression in microglia, supporting neurotrophic functions[21]
  • Regulates microglial activation through the ER stress-dependent PPARδ/SIRT1 signaling cascade[19]

These effects are mediated through both MT receptor-dependent and receptor-independent mechanisms, with SIRT1 serving as a key downstream mediator.[21]

3. Oxidative Stress

Melatonin is a potent direct free radical scavenger with the ability to detoxify reactive oxygen and nitrogen species.[3] Beyond direct scavenging, melatonin:

  • Activates the Nrf2/ARE pathway, inducing phase II antioxidant enzymes[20]
  • Reduces hydrogen peroxide and 8-OHdG (oxidative DNA damage marker) in DRG neurons[4]
  • Decreases LPS-induced ROS generation in microglia[20]
  • Modulates the nitroxidergic system, reducing NO-mediated oxidative/nitrosative stress[5]

Importantly, melatonin is synthesized within mitochondria and accumulates at higher concentrations in mitochondria than in other subcellular compartments, positioning it optimally to protect against mitochondrial oxidative stress.[3]

4. Mitochondrial Dysfunction

Melatonin’s mitochondrial effects are central to its analgesic mechanism:

  • SIRT1/PGC-1α axis: Melatonin upregulates SIRT1 in DRG neurons, which activates PGC-1α (the master regulator of mitochondrial biogenesis), restoring mitochondrial membrane potential after nerve injury. SIRT1 inhibition (with EX527) blocks melatonin’s analgesic effects, confirming the centrality of this pathway.[4]
  • SIRT1/Drp1 pathway: In spinal cord injury, melatonin modulates the SIRT1/Drp1 (dynamin-related protein 1) pathway, reducing mitochondrial fission and dysfunction.[22]
  • Parkin-mediated mitophagy: Melatonin promotes clearance of damaged mitochondria through Parkin-mediated mitophagy, preventing accumulation of dysfunctional mitochondria that would otherwise trigger NLRP3 inflammasome activation.[6]
  • SIRT3 regulation: Melatonin also modulates mitochondrial SIRT3, a major NAD-dependent deacetylase that regulates mitochondrial metabolism and oxidative stress responses.[3][23]

—

References

  1. Melatonin Improves Mitochondrial Dysfunction and Attenuates Neuropathic Pain by Regulating SIRT1 in Dorsal Root Ganglions. Zeng Y, Fang Q, Chen J, et al. Neuroscience. 2023;534:29-40. doi:10.1016/j.neuroscience.2023.10.005.
  2. The Anti-Inflammatory and Analgesic Effects of Intraperitoneal Melatonin After Spinal Nerve Ligation Are Mediated by Inhibition of the NF-κB/NLRP3 Inflammasome Signaling Pathway. Wang YH, Tang YR, Gao X, et al. Brain Research Bulletin. 2021;169:156-166. doi:10.1016/j.brainresbull.2021.01.015.
  3. Targeting Melatonin MT2 Receptors: A Novel Pharmacological Avenue for Inflammatory and Neuropathic Pain. Posa L, De Gregorio D, Gobbi G, Comai S. Current Medicinal Chemistry. 2018;25(32):3866-3882. doi:10.2174/0929867324666170209104926.
  4. Analgesic Efficacy of Melatonin: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials. Oh SN, Myung SK, Jho HJ. Journal of Clinical Medicine. 2020;9(5):E1553. doi:10.3390/jcm9051553.
  5. Melatonin for Neuropathic Pain: A Double-Blind, Placebo-Controlled, Randomized, Crossover Trial. Gilron I, Elkerdawy H, Tu D, et al. Pain. 2025;:00006396-990000000-00905. doi:10.1097/j.pain.0000000000003651.
  6. The Potential Benefits of Quercetin for Brain Health: A Review of Anti-Inflammatory and Neuroprotective Mechanisms. Chiang MC, Tsai TY, Wang CJ. International Journal of Molecular Sciences. 2023;24(7):6328. doi:10.3390/ijms24076328.
  7. Neuropharmacological Interventions of Quercetin and Its Derivatives in Neurological and Psychological Disorders. Agrawal K, Chakraborty P, Dewanjee S, et al. Neuroscience and Biobehavioral Reviews. 2023;144:104955. doi:10.1016/j.neubiorev.2022.104955.
  8. The Emerging Role of Quercetin in the Treatment of Chronic Pain. Liu C, Liu DQ, Tian YK, et al. Current Neuropharmacology. 2022;20(12):2346-2353. doi:10.2174/1570159X20666220812122437.
  9. Computational Analysis and in Vitro Verification Insights Into Quercetin’s Suppression of Neuroinflammation in BV-2 Microglia Through NF-κB Pathway Inhibition. Hsieh CY, Chuang CH, Gomez MC, et al. Current Medicinal Chemistry. 2025;:CMC-EPUB-151006. doi:10.2174/0109298673395813250901012530.
  10. Sulforaphane and Brain Health: From Pathways of Action to Effects on Specific Disorders. Fahey JW, Liu H, Batt H, Panjwani AA, Tsuji P. Nutrients. 2025;17(8):1353. doi:10.3390/nu17081353.
  11. Emerging Promise of Sulforaphane-Mediated Nrf2 Signaling Cascade Against Neurological Disorders. Uddin MS, Mamun AA, Jakaria M, et al. The Science of the Total Environment. 2020;707:135624. doi:10.1016/j.scitotenv.2019.135624.
  12. Sulforaphane: An Emerging Star in Neuroprotection and Neurological Disease Prevention. Wu N, Luo Z, Deng R, et al. Biochemical Pharmacology. 2025;233:116797. doi:10.1016/j.bcp.2025.116797.
  13. Sulforaphane-Enriched Broccoli Sprouts Pretreated by Pulsed Electric Fields Reduces Neuroinflammation and Ameliorates Scopolamine-Induced Amnesia in Mouse Brain Through Its Antioxidant Ability via Nrf2-Ho-1 Activation. Subedi L, Cho K, Park YU, Choi HJ, Kim SY. Oxidative Medicine and Cellular Longevity. 2019;2019:3549274. doi:10.1155/2019/3549274.
  14. Taurine and Its Analogs in Neurological Disorders: Focus on Therapeutic Potential and Molecular Mechanisms. Jakaria M, Azam S, Haque ME, et al. Redox Biology. 2019;24:101223. doi:10.1016/j.redox.2019.101223.
  15. Taurine Protects Against Myelin Damage of Sciatic Nerve in Diabetic Peripheral Neuropathy Rats by Controlling Apoptosis of Schwann Cells via NGF/Akt/GSK3β Pathway. Li K, Shi X, Luo M, et al. Experimental Cell Research. 2019;383(2):111557. doi:10.1016/j.yexcr.2019.111557.
  16. Antinociceptive Effect of Intrathecal Administration of Taurine in Rat Models of Neuropathic Pain. Terada T, Hara K, Haranishi Y, Sata T. Canadian Journal of Anaesthesia = Journal Canadien d’Anesthesie. 2011;58(7):630-637. doi:10.1007/s12630-011-9504-8.
  17. Taurine Replacement Attenuates Hyperalgesia and Abnormal Calcium Signaling in Sensory Neurons of STZ-D Rats. Li F, Obrosova IG, Abatan O, et al. American Journal of Physiology. Endocrinology and Metabolism. 2005;288(1):E29-36. doi:10.1152/ajpendo.00168.2004.
  18. Taurine Inhibits KDM3a Production and Microglia Activation in Lipopolysaccharide-Treated Mice and BV-2 Cells. Liu K, Zhu R, Jiang H, et al. Molecular and Cellular Neurosciences. 2022;122:103759. doi:10.1016/j.mcn.2022.103759.
  19. Taurine Ameliorates Neuropathy via Regulating NF-κB and Nrf2/Ho-1 Signaling Cascades in Diabetic Rats. Agca CA, Tuzcu M, Hayirli A, Sahin K. Food and Chemical Toxicology : An International Journal Published for the British Industrial Biological Research Association. 2014;71:116-21. doi:10.1016/j.fct.2014.05.023.
  20. Prophylaxis Against Complex Regional Pain Syndrome Recurrence With Vitamin C in Total Knee Arthroplasty: A Propensity Score-Matched Analysis of 960 Cases. Hernigou J, Chahidi E, Everaert J, et al. The Journal of Bone and Joint Surgery. American Volume. 2025;:00004623-990000000-01567. doi:10.2106/JBJS.24.01584.
  21. Complex Regional Pain Syndrome. Goebel A. The New England Journal of Medicine. 2025;393(23):2338-2348. doi:10.1056/NEJMcp2415752.
  22. The Role of Vitamin C in the Treatment of Pain: New Insights. Carr AC, McCall C. Journal of Translational Medicine. 2017;15(1):77. doi:10.1186/s12967-017-1179-7.
  23. Effect of Perioperative Vitamin C on the Incidence of Complex Regional Pain Syndrome: A Systematic Review and Meta-Analysis. Seth I, Bulloch G, Seth N, et al. The Journal of Foot and Ankle Surgery : Official Publication of the American College of Foot and Ankle Surgeons. 2022 Jul-Aug;61(4):748-754. doi:10.1053/j.jfas.2021.11.008.
  24. B12 as a Treatment for Peripheral Neuropathic Pain: A Systematic Review. Julian T, Syeed R, Glascow N, Angelopoulou E, Zis P. Nutrients. 2020;12(8):E2221. doi:10.3390/nu12082221.
  25. Mechanisms of Action of Vitamin B1 (Thiamine), B6 (Pyridoxine), and B12 (Cobalamin) in Pain: A Narrative Review. Paez-Hurtado AM, Calderon-Ospina CA, Nava-Mesa MO. Nutritional Neuroscience. 2023;26(3):235-253. doi:10.1080/1028415X.2022.2034242.
  26. Association Between Neuropathy and B-Vitamins: A Systematic Review and Meta-Analysis. Stein J, Geisel J, Obeid R. European Journal of Neurology. 2021;28(6):2054-2064. doi:10.1111/ene.14786.
  27. Clinical Trials on Pain Lowering Effect of Ginger: A Narrative Review. Rondanelli M, Fossari F, Vecchio V, et al. Phytotherapy Research : PTR. 2020;34(11):2843-2856. doi:10.1002/ptr.6730.
  28. Orally Consumed Ginger and Human Health: An Umbrella Review. Crichton M, Davidson AR, Innerarity C, et al. The American Journal of Clinical Nutrition. 2022;115(6):1511-1527. doi:10.1093/ajcn/nqac035.

Clinical Evidence Supporting Pain Pathway Effects

Meta-analyses and Systematic Reviews:

  • A meta-analysis of 30 randomized, double-blind, placebo-controlled trials (n=1,967) found that melatonin significantly reduced chronic pain (SMD -0.65, 95% CI -0.96 to -0.34) in all trials and in high-quality trials (SMD -0.62, 95% CI -1.01 to -0.23).[24] For acute postoperative pain, melatonin showed significant reduction (SMD -0.82, 95% CI -1.40 to -0.25), though high-quality subgroup analysis was not significant.[24]
  • Another meta-analysis of 19 studies confirmed that melatonin significantly decreased pain intensity, reduced the proportion of patients requiring analgesics, and lowered BDNF levels (a marker associated with central sensitization).[25]

Condition-Specific Evidence:

Fibromyalgia:

A randomized, double-blind study of 101 fibromyalgia patients found that melatonin (5 mg alone or 3-5 mg combined with fluoxetine 20 mg) significantly reduced Fibromyalgia Impact Questionnaire (FIQ) scores compared to fluoxetine alone.[1] The combination of melatonin plus fluoxetine was particularly effective.

A more recent pilot study of PEA (1200 mg) combined with melatonin (0.2 mg) in 50 fibromyalgia patients showed significant improvements in VAS pain scores, insomnia severity, health assessment questionnaire scores, and tender point counts at 1 and 3 months, with effects maintained at 4 months (1 month after discontinuation).[2]

Preclinical studies demonstrate that melatonin reduces fibromyalgia-related skeletal muscle alterations, inflammatory markers, and oxidative stress in reserpine-induced myalgia models.[3]

Migraine Prevention:

A network meta-analysis of 25 RCTs (n=4,499) found that oral melatonin 3 mg/day (immediate-release) at bedtime was associated with the greatest improvement in migraine frequency (mean difference -1.71 days, 95% CI -3.27 to -0.14 compared to placebo) and the second highest response rate (OR 4.19, 95% CI 1.46-12.00).[4]

Furthermore, melatonin 3 mg was the most preferred intervention when improvements in migraine frequency, response rate, dropout rate, and adverse events were all considered.[4] A head-to-head RCT comparing melatonin 3 mg, amitriptyline 25 mg, and placebo in 178 migraine patients found melatonin reduced headache frequency by 2.7 days/month (vs. 2.2 for amitriptyline and 1.1 for placebo), with melatonin superior to amitriptyline in the percentage of patients achieving >50% reduction in migraine frequency and better tolerated (including weight loss vs. weight gain with amitriptyline).[5]

Cluster Headache:

Melatonin 10 mg has demonstrated superiority to placebo for cluster headache prophylaxis in controlled trials, representing one of the strongest evidence bases for melatonin in primary headache disorders.[6]

Osteoarthritis:

A UK cohort study comparing melatonin initiators (n=813) to hypnotic benzodiazepine initiators (n=8,135) found that the melatonin cohort had significantly fewer subsequent oral analgesic prescriptions and experienced a 47% lower risk of knee/hip replacement (HR 0.47, 95% CI 0.30-0.73).[7] Mechanistically, melatonin increased serum glycine levels, which was inversely associated with incident symptomatic knee OA in a separate cohort.[7] Recent mechanistic studies demonstrate that melatonin alleviates OA by regulating NOX4-induced ferroptosis and mitigating mitochondrial dysfunction, as well as preventing cartilage degradation through activation of the miR-146a/NRF2/HO-1 axis.[8][9]

Neuropathic Pain:

A recent 2025 double-blind, placebo-controlled, crossover RCT (n=31) found no significant benefit of melatonin over placebo for neuropathic pain (mean daily pain 4.1 vs 4.2, p=0.8) at a mean maximal tolerated dose of 11.9 mg/day.[10] This contrasts with positive preclinical evidence and suggests that neuropathic pain may require higher doses, different formulations, or combination approaches. The negative result may also reflect the heterogeneity of neuropathic pain conditions.

Postoperative Pain:

Meta-analysis evidence is mixed. One meta-analysis found melatonin significantly reduced acute postoperative pain (11 studies, SMD -0.82, 95% CI -1.40 to -0.25), but subgroup analysis of high-quality trials showed no significant effect.[11] Another meta-analysis found melatonin was associated with decreased VAS scores at 24 hours postoperatively (MD -0.86, 95% CI -1.38 to -0.34) with trial sequential analysis confirming this finding, and reduced postoperative opioid consumption (MD -3.33 mg, 95% CI -5.28 to -1.38), though the latter finding was inconclusive on trial sequential analysis.[12] Melatonin also significantly increased time to first analgesic requirement.[12]

                                                                                                                                              References

  1. Melatonin Improves Mitochondrial Dysfunction and Attenuates Neuropathic Pain by Regulating SIRT1 in Dorsal Root Ganglions. Zeng Y, Fang Q, Chen J, et al. Neuroscience. 2023;534:29-40. doi:10.1016/j.neuroscience.2023.10.005.
  2. The Anti-Inflammatory and Analgesic Effects of Intraperitoneal Melatonin After Spinal Nerve Ligation Are Mediated by Inhibition of the NF-κB/NLRP3 Inflammasome Signaling Pathway. Wang YH, Tang YR, Gao X, et al. Brain Research Bulletin. 2021;169:156-166. doi:10.1016/j.brainresbull.2021.01.015.
  3. Targeting Melatonin MT2 Receptors: A Novel Pharmacological Avenue for Inflammatory and Neuropathic Pain. Posa L, De Gregorio D, Gobbi G, Comai S. Current Medicinal Chemistry. 2018;25(32):3866-3882. doi:10.2174/0929867324666170209104926.
  4. Analgesic Efficacy of Melatonin: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials. Oh SN, Myung SK, Jho HJ. Journal of Clinical Medicine. 2020;9(5):E1553. doi:10.3390/jcm9051553.
  5. Melatonin for Neuropathic Pain: A Double-Blind, Placebo-Controlled, Randomized, Crossover Trial. Gilron I, Elkerdawy H, Tu D, et al. Pain. 2025;:00006396-990000000-00905. doi:10.1097/j.pain.0000000000003651.
  6. The Potential Benefits of Quercetin for Brain Health: A Review of Anti-Inflammatory and Neuroprotective Mechanisms. Chiang MC, Tsai TY, Wang CJ. International Journal of Molecular Sciences. 2023;24(7):6328. doi:10.3390/ijms24076328.
  7. Neuropharmacological Interventions of Quercetin and Its Derivatives in Neurological and Psychological Disorders. Agrawal K, Chakraborty P, Dewanjee S, et al. Neuroscience and Biobehavioral Reviews. 2023;144:104955. doi:10.1016/j.neubiorev.2022.104955.
  8. The Emerging Role of Quercetin in the Treatment of Chronic Pain. Liu C, Liu DQ, Tian YK, et al. Current Neuropharmacology. 2022;20(12):2346-2353. doi:10.2174/1570159X20666220812122437.
  9. Computational Analysis and in Vitro Verification Insights Into Quercetin’s Suppression of Neuroinflammation in BV-2 Microglia Through NF-κB Pathway Inhibition. Hsieh CY, Chuang CH, Gomez MC, et al. Current Medicinal Chemistry. 2025;:CMC-EPUB-151006. doi:10.2174/0109298673395813250901012530.
  10. Sulforaphane and Brain Health: From Pathways of Action to Effects on Specific Disorders. Fahey JW, Liu H, Batt H, Panjwani AA, Tsuji P. Nutrients. 2025;17(8):1353. doi:10.3390/nu17081353.
  11. Emerging Promise of Sulforaphane-Mediated Nrf2 Signaling Cascade Against Neurological Disorders. Uddin MS, Mamun AA, Jakaria M, et al. The Science of the Total Environment. 2020;707:135624. doi:10.1016/j.scitotenv.2019.135624.
  12. Sulforaphane: An Emerging Star in Neuroprotection and Neurological Disease Prevention. Wu N, Luo Z, Deng R, et al. Biochemical Pharmacology. 2025;233:116797. doi:10.1016/j.bcp.2025.116797.
  13. Sulforaphane-Enriched Broccoli Sprouts Pretreated by Pulsed Electric Fields Reduces Neuroinflammation and Ameliorates Scopolamine-Induced Amnesia in Mouse Brain Through Its Antioxidant Ability via Nrf2-Ho-1 Activation. Subedi L, Cho K, Park YU, Choi HJ, Kim SY. Oxidative Medicine and Cellular Longevity. 2019;2019:3549274. doi:10.1155/2019/3549274.
  14. Taurine and Its Analogs in Neurological Disorders: Focus on Therapeutic Potential and Molecular Mechanisms. Jakaria M, Azam S, Haque ME, et al. Redox Biology. 2019;24:101223. doi:10.1016/j.redox.2019.101223.
  15. Taurine Protects Against Myelin Damage of Sciatic Nerve in Diabetic Peripheral Neuropathy Rats by Controlling Apoptosis of Schwann Cells via NGF/Akt/GSK3β Pathway. Li K, Shi X, Luo M, et al. Experimental Cell Research. 2019;383(2):111557. doi:10.1016/j.yexcr.2019.111557.
  16. Antinociceptive Effect of Intrathecal Administration of Taurine in Rat Models of Neuropathic Pain. Terada T, Hara K, Haranishi Y, Sata T. Canadian Journal of Anaesthesia = Journal Canadien d’Anesthesie. 2011;58(7):630-637. doi:10.1007/s12630-011-9504-8.
  17. Taurine Replacement Attenuates Hyperalgesia and Abnormal Calcium Signaling in Sensory Neurons of STZ-D Rats. Li F, Obrosova IG, Abatan O, et al. American Journal of Physiology. Endocrinology and Metabolism. 2005;288(1):E29-36. doi:10.1152/ajpendo.00168.2004.
  18. Taurine Inhibits KDM3a Production and Microglia Activation in Lipopolysaccharide-Treated Mice and BV-2 Cells. Liu K, Zhu R, Jiang H, et al. Molecular and Cellular Neurosciences. 2022;122:103759. doi:10.1016/j.mcn.2022.103759.
  19. Taurine Ameliorates Neuropathy via Regulating NF-κB and Nrf2/Ho-1 Signaling Cascades in Diabetic Rats. Agca CA, Tuzcu M, Hayirli A, Sahin K. Food and Chemical Toxicology : An International Journal Published for the British Industrial Biological Research Association. 2014;71:116-21. doi:10.1016/j.fct.2014.05.023.
  20. Prophylaxis Against Complex Regional Pain Syndrome Recurrence With Vitamin C in Total Knee Arthroplasty: A Propensity Score-Matched Analysis of 960 Cases. Hernigou J, Chahidi E, Everaert J, et al. The Journal of Bone and Joint Surgery. American Volume. 2025;:00004623-990000000-01567. doi:10.2106/JBJS.24.01584.
  21. Complex Regional Pain Syndrome. Goebel A. The New England Journal of Medicine. 2025;393(23):2338-2348. doi:10.1056/NEJMcp2415752.
  22. The Role of Vitamin C in the Treatment of Pain: New Insights. Carr AC, McCall C. Journal of Translational Medicine. 2017;15(1):77. doi:10.1186/s12967-017-1179-7.
  23. Effect of Perioperative Vitamin C on the Incidence of Complex Regional Pain Syndrome: A Systematic Review and Meta-Analysis. Seth I, Bulloch G, Seth N, et al. The Journal of Foot and Ankle Surgery : Official Publication of the American College of Foot and Ankle Surgeons. 2022 Jul-Aug;61(4):748-754. doi:10.1053/j.jfas.2021.11.008.
  24. B12 as a Treatment for Peripheral Neuropathic Pain: A Systematic Review. Julian T, Syeed R, Glascow N, Angelopoulou E, Zis P. Nutrients. 2020;12(8):E2221. doi:10.3390/nu12082221.
  25. Mechanisms of Action of Vitamin B1 (Thiamine), B6 (Pyridoxine), and B12 (Cobalamin) in Pain: A Narrative Review. Paez-Hurtado AM, Calderon-Ospina CA, Nava-Mesa MO. Nutritional Neuroscience. 2023;26(3):235-253. doi:10.1080/1028415X.2022.2034242.
  26. Association Between Neuropathy and B-Vitamins: A Systematic Review and Meta-Analysis. Stein J, Geisel J, Obeid R. European Journal of Neurology. 2021;28(6):2054-2064. doi:10.1111/ene.14786.
  27. Clinical Trials on Pain Lowering Effect of Ginger: A Narrative Review. Rondanelli M, Fossari F, Vecchio V, et al. Phytotherapy Research : PTR. 2020;34(11):2843-2856. doi:10.1002/ptr.6730.
  28. Orally Consumed Ginger and Human Health: An Umbrella Review. Crichton M, Davidson AR, Innerarity C, et al. The American Journal of Clinical Nutrition. 2022;115(6):1511-1527. doi:10.1093/ajcn/nqac035.—

Dose-Response Evidence

A phase II dose-response trial in healthy subjects demonstrated that sublingual melatonin exerts well-defined dose-dependent antinociceptive activity.[13] Serum plasma melatonin levels were directly proportional to doses given, with significant differences between placebo and intermediate (0.15 mg/kg) and highest (0.25 mg/kg) doses for all pain threshold and sedation tests. Linear regression showed significant associations between serum melatonin concentrations and changes in heat pain threshold (R² = 0.492), pressure pain threshold (R² = 0.538), heat pain tolerance (R² = 0.558), and pressure pain tolerance (R² = 0.584).[13]

Clinical dosing across studies has varied considerably:

  • Migraine prophylaxis: 3 mg immediate-release at bedtime appears optimal[4][5]
  • Fibromyalgia: 3-5 mg alone or in combination with antidepressants[1]
  • Cluster headache: 10 mg[6]
  • Postoperative/acute pain: Variable (3-10 mg preoperatively)[11][12]
  • Neuropathic pain: Up to 12 mg showed no benefit in recent RCT[10]

Safety Profile

Melatonin demonstrates an excellent safety profile across multiple systematic reviews and meta-analyses. A systematic review of 37 RCTs found the most frequently reported adverse events were daytime sleepiness (1.66%), headache (0.74%), other sleep-related AEs (0.74%), dizziness (0.74%), and hypothermia (0.62%).[14] Very few serious or clinically significant adverse events were reported, and most resolved spontaneously within days or immediately upon withdrawal.[14]

A pharmacovigilance study using WHO-VigiBase (35,479 adverse event reports) found that melatonin showed safety profiles comparable to other sleep medications.[15] Potential signals identified included accidents/injuries, falls, nightmares, and abnormal dreams when compared to all other drugs, but these signals were not detected when compared specifically to other sleep medications, suggesting they are class effects of sleep-promoting agents rather than melatonin-specific.[15]

A systematic review of higher-dose melatonin (≥10 mg) found limited adverse event reporting but concluded that melatonin appears to have a good safety profile, with increased risk of minor AEs such as drowsiness, headache, and dizziness (Rate Ratio 1.40, 95% CI 1.15-1.69) but no increase in serious adverse events or withdrawals.[16]

Specific considerations:

  • Drug interactions: Caution advised with warfarin (case reports of interaction) and in patients with epilepsy[17]
  • Glucose metabolism: Some evidence of impaired glucose tolerance with acute administration in healthy women[17]
  • Pregnancy/lactation: Should be avoided due to lack of safety data[18]
  • Children/adolescents: Long-term safety requires further investigation[17][18]
  • Quality concerns: As a dietary supplement, melatonin is not subject to FDA scrutiny; United States Pharmacopeial Convention Verified formulations are most reliable[17]

Synergistic Potential with Other Nutraceuticals

Melatonin offers several synergistic opportunities within the paradigm:

1. NAD+/Sirtuin Axis Synergy (with NR and Resveratrol)

Melatonin’s SIRT1 activation in DRG neurons provides mechanistic synergy with nicotinamide riboside (NAD+ precursor) and resveratrol (SIRT1 activator). This convergent activation of the SIRT1/PGC-1α axis may enhance mitochondrial biogenesis and protection beyond what any single agent achieves.[11] The combination addresses mitochondrial dysfunction through complementary mechanisms: NR provides the NAD+ substrate, resveratrol directly activates SIRT1, and melatonin upregulates SIRT1 expression.

2. Antioxidant Network Enhancement (with ALA, NAC, CoQ10)

Melatonin’s Nrf2/ARE pathway activation complements the antioxidant mechanisms of alpha-lipoic acid, NAC, and CoQ10. While ALA and NAC serve as glutathione precursors and direct antioxidants, and CoQ10 protects the mitochondrial electron transport chain, melatonin provides unique mitochondrial-localized antioxidant protection and enhances phase II enzyme induction.[19][9]

3. Neuroinflammation Targeting (with PEA and Curcumin)

The clinical evidence for PEA + melatonin combination in fibromyalgia suggests synergistic neuroinflammatory modulation.[2] PEA’s PPAR-α activation and mast cell stabilization complement melatonin’s microglial M2 polarization and NLRP3 inflammasome inhibition. Curcumin’s NF-κB inhibition provides additional convergent anti-neuroinflammatory effects.

4. Descending Pathway Modulation (Unique Contribution)

Melatonin’s MT2 receptor-mediated activation of descending antinociceptive pathways from the vlPAG represents a unique mechanism not prominently featured in other nutraceuticals. This provides a distinct therapeutic target that complements peripheral and spinal mechanisms addressed by other agents.

5. Omega-3 Fatty Acid Synergy

Both melatonin and omega-3 fatty acids (EPA/DHA) modulate inflammatory pathways and have demonstrated benefits in migraine prevention. Their combination may provide enhanced anti-inflammatory and membrane-stabilizing effects.

—

Summary

Melatonin represents a valuable addition to the nutraceutical paradigm for pain management, offering:

1. Mechanism Diversity:

Assessment  of Benefit: Excellent

MT1/MT2 receptor-mediated effects, SIRT1 activation, Nrf2/ARE pathway, NLRP3 inhibition, descending pathway modulation

2. Pathological Target Coverage

All four targets addressed (systemic inflammation, neuroinflammation, oxidative stress, mitochondrial dysfunction)

3. Unique Contribution

Descending pain modulation via vlPAG MT2 receptors; circadian regulation; endogenous opioid enhancement

4. Clinical Evidence Level

Assessment  of Benefit:

    • Moderate-High for migraine/cluster headache;
    • Moderate for fibromyalgia and chronic pain;
    • Low-Negative for neuropathic pain specifically

5. Safety Profile

Assessment: Excellent

Mild, transient adverse effects; favorable compared to conventional analgesics

Synergistic Potential

Assessment: High

    1. Complements NAD+/sirtuin axis (NR, Resveratrol)
    2. Antioxidant network (ALA, NAC, CoQ10)
    3. Neuroinflammation targeting (PEA, Curcumin)

Key clinical considerations:

    1. Condition-specific efficacy: Strongest evidence for migraine prophylaxis (3 mg immediate-release) and cluster headache (10 mg); recent negative RCT for neuropathic pain suggests this may not be an optimal indication
    1. Formulation matters: Immediate-release 3 mg appears superior to sustained-release formulations for migraine
    1. Timing: Bedtime administration aligns with circadian physiology and sleep-pain interactions
    1. Combination potential: Evidence supports combination with PEA for fibromyalgia; theoretical synergy with NR/resveratrol for mitochondrial protection

—

References

  1. Adjuvant Use of Melatonin for Treatment of Fibromyalgia. Hussain SA, Al-Khalifa II, Jasim NA, Gorial FI. Journal of Pineal Research. 2011;50(3):267-71. doi:10.1111/j.1600-079X.2010.00836.x.
  2. A Fixed Combination of Palmitoylethanolamide and Melatonin (PEATONIDE) for the Management of Pain, Sleep, and Disability in Patients With Fibromyalgia: A Pilot Study. Terribili R, Vallifuoco G, Bardelli M, Frediani B, Gentileschi S. Nutrients. 2024;16(16):2785. doi:10.3390/nu16162785.
  3. Oral Supplementation of Melatonin Protects Against Fibromyalgia-Related Skeletal Muscle Alterations in Reserpine-Induced Myalgia Rats. Favero G, Trapletti V, Bonomini F, et al. International Journal of Molecular Sciences. 2017;18(7):E1389. doi:10.3390/ijms18071389.
  4. The Association Between Melatonin and Episodic Migraine: A Pilot Network Meta-Analysis of Randomized Controlled Trials to Compare the Prophylactic Effects With Exogenous Melatonin Supplementation and Pharmacotherapy. Tseng PT, Yang CP, Su KP, et al. Journal of Pineal Research. 2020;69(2):e12663. doi:10.1111/jpi.12663.
  5. Randomised Clinical Trial Comparing Melatonin 3 mg, Amitriptyline 25 mg and Placebo for Migraine Prevention. Gonçalves AL, Martini Ferreira A, Ribeiro RT, et al. Journal of Neurology, Neurosurgery, and Psychiatry. 2016;87(10):1127-32. doi:10.1136/jnnp-2016-313458.
  6. The Role of Melatonin in the Treatment of Primary Headache Disorders. Gelfand AA, Goadsby PJ. Headache. 2016;56(8):1257-66. doi:10.1111/head.12862.
  7. Melatonin Is a Potential Novel Analgesic Agent for Osteoarthritis: Evidence From Cohort Studies in Humans and Preclinical Research in Rats. Li H, Zhou B, Wu J, et al. Journal of Pineal Research. 2024;76(2):e12945. doi:10.1111/jpi.12945.
  8. Melatonin Alleviates Osteoarthritis by Regulating NADPH Oxidase 4-Induced Ferroptosis and Mitigating Mitochondrial Dysfunction. Wang Q, Qi B, Shi S, et al. Journal of Pineal Research. 2024;76(6):e12992. doi:10.1111/jpi.12992.
  9. Melatonin Prevents Cartilage Degradation in Early-Stage Osteoarthritis Through Activation of miR-146a/NRF2/HO-1 Axis. Zhou X, Zhang Y, Hou M, et al. Journal of Bone and Mineral Research : The Official Journal of the American Society for Bone and Mineral Research. 2022;37(5):1056-1072. doi:10.1002/jbmr.4527.
  10. Melatonin for Neuropathic Pain: A Double-Blind, Placebo-Controlled, Randomized, Crossover Trial. Gilron I, Elkerdawy H, Tu D, et al. Pain. 2025;:00006396-990000000-00905. doi:10.1097/j.pain.0000000000003651.
  11. Analgesic Efficacy of Melatonin: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials. Oh SN, Myung SK, Jho HJ. Journal of Clinical Medicine. 2020;9(5):E1553. doi:10.3390/jcm9051553.
  12. Effect of Melatonin on Postoperative Pain and Perioperative Opioid Use: A Meta-Analysis and Trial Sequential Analysis. Wang Z, Li Y, Lin D, Ma J. Pain Practice : The Official Journal of World Institute of Pain. 2021;21(2):190-203. doi:10.1111/papr.12948.
  13. A Phase II, Randomized, Double-Blind, Placebo Controlled, Dose-Response Trial of the Melatonin Effect on the Pain Threshold of Healthy Subjects. Stefani LC, Muller S, Torres IL, et al. PloS One. 2013;8(10):e74107. doi:10.1371/journal.pone.0074107.
  14. Adverse Events Associated With Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review. Besag FMC, Vasey MJ, Lao KSJ, Wong ICK. CNS Drugs. 2019;33(12):1167-1186. doi:10.1007/s40263-019-00680-w.
  15. Investigating the Safety Profiles of Exogenous Melatonin and Associated Adverse Events: A Pharmacovigilance Study Using WHO-VigiBase. Ha M, Yoon D, Lee CY, et al. Journal of Pineal Research. 2024;76(2):e12949. doi:10.1111/jpi.12949.
  16. Safety of Higher Doses of Melatonin in Adults: A Systematic Review and Meta-Analysis. Menczel Schrire Z, Phillips CL, Chapman JL, et al. Journal of Pineal Research. 2022;72(2):e12782. doi:10.1111/jpi.12782.
  17. Clinical Practice Guideline for the Treatment of Intrinsic Circadian Rhythm Sleep-Wake Disorders: Advanced Sleep-Wake Phase Disorder (ASWPD), Delayed Sleep-Wake Phase Disorder (DSWPD), Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD), and Irregular Sleep-Wake Rhythm Disorder (ISWRD). An Update for 2015: An American Academy of Sleep Medicine Clinical Practice Guideline. Auger RR, Burgess HJ, Emens JS, et al. Journal of Clinical Sleep Medicine : JCSM : Official Publication of the American Academy of Sleep Medicine. 2015;11(10):1199-236. doi:10.5664/jcsm.5100.
  18. The Safety of Melatonin in Humans. Andersen LP, Gögenur I, Rosenberg J, Reiter RJ. Clinical Drug Investigation. 2016;36(3):169-75. doi:10.1007/s40261-015-0368-5. 
  19. Prophylaxis Against Complex Regional Pain Syndrome Recurrence With Vitamin C in Total Knee Arthroplasty: A Propensity Score-Matched Analysis of 960 Cases. Hernigou J, Chahidi E, Everaert J, et al. The Journal of Bone and Joint Surgery. American Volume. 2025;:00004623-990000000-01567. doi:10.2106/JBJS.24.01584.

 

Melatonin: Pain Processing Effects vs. Direct Tissue-Modifying Effects

   Pain Processing Effects:

Melatonin exerts analgesic effects through multiple receptor-mediated and receptor-independent mechanisms. The MT2 receptor appears particularly important for analgesia—MT2 receptors are localized in specific brain areas including the reticular and ventromedial nuclei of the thalamus (ascending nociceptive pathway) and the ventrolateral periaqueductal grey matter (vlPAG, descending antinociceptive pathway). Selective MT2 receptor partial agonists produce analgesic effects with higher potency than melatonin itself, without inducing sedation or motor impairments.[1]

A key discovery is that melatonin’s analgesic effects require mu-opioid receptor (MOR) recruitment. In neuropathic pain models, the antiallodynic effects of the MT2 agonist UCM924 were nullified by pharmacological blockade or genetic inactivation of MOR, but not delta opioid receptors. Electrophysiological recordings revealed that MT2 agonism in the vlPAG reduces firing of pronociceptive ON-cells and enhances firing of antinociceptive OFF-cells in the rostral ventromedial medulla—effects blocked by MOR antagonism. MT2 receptor agonism also increases enkephalin precursor gene (PENK) expression in the PAG.[2]

Melatonin also modulates GABA-A receptor function and benzodiazepine-GABAergic pathways. The antiallodynic effect of melatonin is abolished by both flumazenil (benzodiazepine antagonist) and picrotoxin (GABA-A antagonist), indicating involvement of GABAergic mechanisms in mechanical allodynia relief.[3] Additionally, melatonin opens several K⁺ channels, inhibits 5-lipoxygenase and COX-2 expression, and reduces pro-inflammatory cytokine production.[2]

In neuropathic pain models, melatonin alleviates mechanical allodynia and hyperalgesia via SIRT1 activation in dorsal root ganglia. Melatonin treatment restored injury-dependent decreases in mitochondrial membrane potential and PGC-1α, reduced hydrogen peroxide and 8-OHdG (oxidative stress markers), and inhibited TNF-α and IL-1β expression—effects blocked by the SIRT1 inhibitor EX527.[4]

   Clinical Evidence for Pain Processing:

A 2020 meta-analysis of 30 double-blind, placebo-controlled RCTs (1,967 participants) found melatonin significantly reduced chronic pain (SMD -0.65, 95% CI -0.96 to -0.34) in all trials and high-quality trials (SMD -0.62, 95% CI -1.01 to -0.23). Melatonin also reduced acute postoperative pain in pooled analysis, though high-quality subgroup analysis showed no significant effect.[5]

However, a 2025 double-blind, placebo-controlled, crossover RCT specifically for neuropathic pain (n=31) found no evidence of efficacy. At maximally tolerated doses (mean 11.9 mg/day), mean daily pain was 4.1 for melatonin vs 4.2 for placebo (p=0.8), with no significant differences in any secondary outcomes including sleep, mood, or quality of life.[6]

A UK primary care cohort study comparing melatonin initiators to hypnotic benzodiazepine initiators in OA patients found the melatonin cohort had significantly fewer subsequent oral analgesic prescriptions (50th percentile: 5 vs 7; 75th percentile: 19 vs 29) and experienced a lower risk of knee/hip replacement (HR 0.47, 95% CI 0.30-0.73). In rats, oral melatonin alleviated pain behaviors and increased serum glycine levels, which inversely correlated with incident symptomatic knee OA in humans.[7]

For fibromyalgia, a pilot study of PEA 1,200 mg + melatonin 0.2 mg daily showed significant improvements in VAS pain, insomnia severity, and health assessment scores at 1 and 3 months, maintained at 4 months after discontinuation.[8]

   Direct Tissue-Modifying Effects:

Melatonin demonstrates robust chondroprotective effects in preclinical OA models through SIRT1-mediated pathways. In ACLT-induced OA rats, melatonin (30 mg/kg for 12 weeks) resulted in relatively smooth cartilage surface, modest chondrocyte loss, mild synovial hyperplasia, and increased subchondral bone thickness. Melatonin upregulated type II collagen and aggrecan while inhibiting MMP-3, MMP-13, and ADAMTS-4 expression.[9][10]

Mechanistically, melatonin prevents cartilage degradation through the miR-146a/NRF2/HO-1 axis. In early-stage OA, melatonin significantly increased cartilage matrix synthesis, upregulated antioxidant enzymes (particularly HO-1), decreased matrix degradation enzymes, and reduced intracellular ROS. Inhibition of melatonin membrane receptors by luzindole or 4-P-PDOT reversed these beneficial effects, confirming receptor-mediated chondroprotection.[11]

Melatonin also recharges chondrocyte mitochondria—OA chondrocytes show compromised matrix synthesis associated with mitochondrial dysfunction. Melatonin promoted ECM component expression, improved ATP production, and attenuated mitochondrial oxidative stress through SIRT1 and SOD2 pathways. A melatonin-laden drug delivery system successfully improved cartilage matrix degeneration in a post-traumatic rat OA model.[12]

 

Mechanism

Pain Processing

Tissue Modification

References

MT2 receptor → vlPAG → RVM modulation

Activates OFF-cells, inhibits ON-cells in descending pathway

None

[1], [2]

MOR recruitment (via PENK upregulation)

Required for antiallodynic effects; blocked by naloxone/CTOP

None

[2], [3]

GABA-A/benzodiazepine pathway modulation

Abolishes mechanical allodynia (blocked by flumazenil/picrotoxin)

None

[3]

SIRT1 activation in DRG

Restores mitochondrial function; ↓oxidative stress; ↓TNF-α/IL-1β

Reduces chondrocyte senescence; ↑ECM synthesis

[4], [5]

miR-146a/NRF2/HO-1 axis activation

Indirect (antioxidant)

Prevents cartilage degradation; ↑matrix synthesis; ↓ROS

[6]

NF-κB inhibition via SIRT1

Reduces neuroinflammation

↓MMP-3/13, ADAMTS-4; ↑collagen II, aggrecan

[7], [8]

Circadian clock gene modulation

Indirect (sleep improvement → pain reduction)

Regulates cartilage regeneration/degradation

[9]

References

  1. Targeting Melatonin MT2 Receptors: A Novel Pharmacological Avenue for Inflammatory and Neuropathic Pain. Posa L, De Gregorio D, Gobbi G, Comai S. Current Medicinal Chemistry. 2018;25(32):3866-3882. doi:10.2174/0929867324666170209104926.
  2. Melatonin: A Hormone That Modulates Pain. Ambriz-Tututi M, Rocha-González HI, Cruz SL, Granados-Soto V. Life Sciences. 2009;84(15-16):489-98. doi:10.1016/j.lfs.2009.01.024.
  3. Supraspinal Melatonin MT Receptor Agonism Alleviates Pain via a Neural Circuit That Recruits Mu Opioid Receptors. Posa L, De Gregorio D, Lopez-Canul M, et al. Journal of Pineal Research. 2022;73(4):e12825. doi:10.1111/jpi.12825.
  4. Melatonin Improves Mitochondrial Dysfunction and Attenuates Neuropathic Pain by Regulating SIRT1 in Dorsal Root Ganglions. Zeng Y, Fang Q, Chen J, et al. Neuroscience. 2023;534:29-40. doi:10.1016/j.neuroscience.2023.10.005.
  5. Analgesic Efficacy of Melatonin: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials. Oh SN, Myung SK, Jho HJ. Journal of Clinical Medicine. 2020;9(5):E1553. doi:10.3390/jcm9051553.
  6. Melatonin for Neuropathic Pain: A Double-Blind, Placebo-Controlled, Randomized, Crossover Trial. Gilron I, Elkerdawy H, Tu D, et al. Pain. 2025;:00006396-990000000-00905. doi:10.1097/j.pain.0000000000003651.
  7. Melatonin Is a Potential Novel Analgesic Agent for Osteoarthritis: Evidence From Cohort Studies in Humans and Preclinical Research in Rats. Li H, Zhou B, Wu J, et al. Journal of Pineal Research. 2024;76(2):e12945. doi:10.1111/jpi.12945.
  8. A Fixed Combination of Palmitoylethanolamide and Melatonin (PEATONIDE) for the Management of Pain, Sleep, and Disability in Patients With Fibromyalgia: A Pilot Study. Terribili R, Vallifuoco G, Bardelli M, Frediani B, Gentileschi S. Nutrients. 2024;16(16):2785. doi:10.3390/nu16162785.
  9. Melatonin Delays Arthritis Inflammation and Reduces Cartilage Matrix Degradation Through the SIRT1-Mediated NF-κB/Nrf2/TGF-β/BMPs Pathway. Zhao M, Qiu D, Miao X, et al. International Journal of Molecular Sciences. 2024;25(11):6202. doi:10.3390/ijms25116202.
  10. Melatonin Prevents Chondrocyte Matrix Degradation in Rats With Experimentally Induced Osteoarthritis by Inhibiting Nuclear Factor-κB via SIRT1. Zhao M, Song X, Chen H, et al. Nutrients. 2022;14(19):3966. doi:10.3390/nu14193966.
  11. Melatonin Prevents Cartilage Degradation in Early-Stage Osteoarthritis Through Activation of miR-146a/NRF2/HO-1 Axis. Zhou X, Zhang Y, Hou M, et al. Journal of Bone and Mineral Research : The Official Journal of the American Society for Bone and Mineral Research. 2022;37(5):1056-1072. doi:10.1002/jbmr.4527.
  12. Recharge of Chondrocyte Mitochondria by Sustained Release of Melatonin Protects Cartilage Matrix Homeostasis in Osteoarthritis. Zhang Y, Hou M, Liu Y, et al. Journal of Pineal Research. 2022;73(2):e12815. doi:10.1111/jpi.12815.
  13. The Potential Remedy of Melatonin on Osteoarthritis. Lu KH, Lu PW, Lu EW, et al. Journal of Pineal Research. 2021;71(3):e12762. doi:10.1111/jpi.12762.

Emphasis on Education

 

Accurate Clinic promotes patient education as the foundation of it’s medical care. In Dr. Ehlenberger’s integrative approach to patient care, including conventional and complementary and alternative medical (CAM) treatments, he may encourage or provide advice about the use of supplements. However, the specifics of choice of supplement, dosing and duration of treatment should be individualized through discussion with Dr. Ehlenberger. The following information and reference articles are presented to provide the reader with some of the latest research to facilitate evidence-based, informed decisions regarding the use of conventional as well as CAM treatments.

 

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