Melatonin: A New-Generation Therapy for Reducing Chronic Pain and Improving Sleep Disorder-Related Pain

Melatonin treatment has consistent but transient beneficial effects on sleep measures and pain in patients with severe chronic pain: the DREAM-CP randomised controlled trial

BACKGROUND

Sleep disturbance is a major issue for patients with chronic pain. Melatonin has been shown to improve symptoms of fibromyalgia, but its efficacy in other chronic non-malignant pain conditions is not fully known. Hence, we determined the effect of melatonin in patients with severe noncancer chronic pain.

METHODS

This was a randomised double-blinded crossover trial of modified-release melatonin as Circadin™ compared with placebo. Sixty male and female subjects with chronic severe pain were randomised to receive either 2 mg of Circadin™ or placebo before sleep for 6 weeks, followed by a >4 week washout, then crossing over to the other treatment. Sleep disturbance, quality, and latency were measured using three different validated sleep assessment tools. The primary outcome measure was self-reported sleep disturbance after 6 weeks of treatment. Adverse events were also recorded.

RESULTS

Sleep disturbance after 6 weeks was not significantly altered by melatonin treatment, but differences between melatonin and placebo treatment periods after 3 weeks were seen: sleep disturbance (P=0.014), latency (P=0.04), overall sleep quality (P=0.004), and effect of pain on sleep (P=0.032). Pain intensity scores improved during both treatment periods (both P<0.001). There were no differences in adverse events between treatment periods.

CONCLUSIONS

Circadin™ treatment did not improve sleep disturbance in patients with severe chronic pain compared with placebo at 6 weeks, but there were consistent improvements in aspects of sleep in the shorter term. Given its favourable safety profile, it could be beneficial for some patients with chronic pain.

CLINICAL TRIAL REGISTRATION

ISRCTN12861060.

Impact of Melatonin as a Premedication Agent in Caesarean Section on Blood Loss and Postoperative Pain Level

Background

Postpartum hemorrhage (PPH) is a serious postdelivery condition with a high incidence of morbidity and mortality for women who undergo childbirth with or without a caesarean section. Melatonin has been suggested to increase the contractility of myometrium and reduce the pain score postoperatively, therefore it is believed that the use of melatonin before surgery may decrease blood loss, reduce pain score, and decrease the need for postoperative opioids.

Objectives

The main objectives of this study are focused on the investigation of melatonin as a premedication agent to reduce blood loss and decrease pain score postoperatively in patients undergoing cesarean section under spinal anesthesia.

Methods

80 patients were scheduled for spinal anesthesia-based cesarean sections and randomly assigned to two groups, melatonin group (M) 40 patients and placebo group (P) 40 patients to receive either 10 mg of sublingual melatonin or a placebo of 90 minutes preoperatively. Hemoglobin levels were been measured preoperative and 12 hrs. Postoperatively, blood loss volume was calculated by measuring both the weight of used materials before and after the surgery and the volume sucked in the suction bottle after placental delivery. Postoperative visual pain score and analgesic requirements were used to evaluate pain levels.

Results

Analyzed collected data showed a significant decrease in blood loss in the melatonin group in comparison with the placebo group as measured by the hemoglobin level. On the other hand, there is a significant decrease in pain score and analgesia requirement with the melatonin group compared to the placebo group.

Conclusion

Melatonin is a promising premedication drug that has a significant impact on postpartum hemorrhage by reducing blood loss and pain levels of mothers who have undergone C-sections.

Single-nucleus transcriptome analysis reveals transcriptional profiles of circadian clock and pain related genes in human and mouse trigeminal ganglion

Introduction

Clinical studies have revealed the existence of circadian rhythms in pain intensity and treatment response for chronic pain, including orofacial pain. The circadian clock genes in the peripheral ganglia are involved in pain information transmission by modulating the synthesis of pain mediators. However, the expression and distribution of clock genes and pain-related genes in different cell types within the trigeminal ganglion, the primary station of orofacial sensory transmission, are not yet fully understood.

Methods

In this study, data from the normal trigeminal ganglion in the Gene Expression Omnibus (GEO) database were used to identify cell types and neuron subtypes within the human and mouse trigeminal ganglion by single nucleus RNA sequencing analysis. In the subsequent analyses, the distribution of the core clock genes, pain-related genes, and melatonin and opioid-related genes was assessed in various cell clusters and neuron subtypes within the human and mouse trigeminal ganglion. Furthermore, the statistical analysis was used to compare the differences in the expression of pain-related genes in the neuron subtypes of trigeminal ganglion.

Results

The present study provides comprehensive transcriptional profiles of core clock genes, pain-related genes, melatonin-related genes, and opioid-related genes in different cell types and neuron subtypes within the mouse and human trigeminal ganglion. A comparative analysis of the distribution and expression of the aforementioned genes was conducted between human and mouse trigeminal ganglion to investigate species differences.

Discussion

Overall, the results of this study serve as a primary and valuable resource for exploring the molecular mechanisms underlying oral facial pain and pain rhythms.

The Influence of Sleep Disturbance on Chronic Pain

PURPOSE OF REVIEW

The purpose of this review is to present an overview of common sleep disturbance pathologies and their impact on chronic pain, while examining various factors that are implicit in the relationship between sleep disturbance and chronic pain, including neurobiochemistry, anatomy, and systemic mediators, and reviewing recent and landmark literature.

RECENT FINDINGS

Earlier literature reviews and studies have introduced the bidirectional relationship between sleep disturbance and chronic pain; that is, impaired sleep may worsen chronic pain, and chronic pain causes sleep disturbance. However, more recent reviews and studies seem to show a more associative, rather than causative relationship. There have been recent studies that attempt to determine mechanisms that link sleep disturbance and chronic pain; the results of these studies were more varied, ultimately concluding that there may be a separate, yet-to-be discovered mechanism that shows the causative relationship between sleep disturbance and pain. There are several neurotransmitters that are involved in the mediation of chronic pain and sleep disturbance as separate entities, and some studies have shown that there may be mechanisms that govern both chronic pain and sleep disturbance as a single unit. Other neuroendocrine substances also serve to mediate chronic pain and sleep disturbance. All these substances are found to be associated with various sleep disorders and are also associated with chronic pain symptoms as well. Inflammation plays a role in chronic pain and sleep disturbance, with an increase in inflammatory substances and mediators associated with an increase or worsening in chronic pain symptoms and sleep disorders. The HPA axis plays a role in chronic pain and sleep disorders, influencing pain and sleep pathways through stress response, inflammation, and maintenance of homeostasis. There are several variables that influence both chronic pain and sleep disturbance, and more research into these variables may further our understanding into the complex pathways governing the influence of sleep disturbance on pain, and ultimately to improve treatment for this issue.

Relevance of Sleep Disturbances to Orthopaedic Surgery: A Current Concepts Narrative and Practical Review

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Sleep disturbances can increase the risk of falls and motor vehicle accidents and may reduce bone density.

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Poor sleep can lead to worse outcomes after fracture, such as chronic pain and delayed recovery.

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Orthopaedic surgeons can play an important role in the screening of sleep disorders among their patients.

Why It Is Important to Consider the Effects of Analgesics on Sleep: A Critical Review

We review the known physiological mechanisms underpinning all of pain processing, sleep regulation, and pharmacology of analgesics prescribed for chronic pain. In particular, we describe how commonly prescribed analgesics act in sleep-wake neural pathways, with potential unintended impact on sleep and/or wake function. Sleep disruption, whether pain- or drug-induced, negatively impacts quality of life, mental and physical health. In the context of chronic pain, poor sleep quality heightens pain sensitivity and may affect analgesic function, potentially resulting in further analgesic need. Clinicians already have to consider factors including efficacy, abuse potential, and likely side effects when making analgesic prescribing choices. We propose that analgesic-related sleep disruption should also be considered. The neurochemical mechanisms underlying the reciprocal relationship between pain and sleep are poorly understood, and studies investigating sleep in those with specific chronic pain conditions (including those with comorbidities) are lacking. We emphasize the importance of further work to clarify the effects (intended and unintended) of each analgesic class to inform personalized treatment decisions in patients with chronic pain. © 2021 American Physiological Society. Compr Physiol 11:1-31, 2021.

At the intersection of sleep deficiency and opioid use: mechanisms and therapeutic opportunities

Due to the ongoing opioid epidemic, innovative scientific perspectives and approaches are urgently needed to reduce the unprecedented personal and societal burdens of nonmedical and recreational opioid use. One promising opportunity is to focus on the relationship between sleep deficiency and opioid use. In this review, we examine empirical evidence: (1) at the interface of sleep deficiency and opioid use, including hypothesized bidirectional associations between sleep efficiency and opioid abstinence; (2) as to whether normalization of sleep deficiency might directly or indirectly improve opioid abstinence (and vice versa); and (3) regarding mechanisms that could link improvements in sleep to opioid abstinence. Based on available data, we identify candidate sleep-restorative therapeutic approaches that should be examined in rigorous clinical trials.

Associations of frequent pain symptoms with excessive daytime sleepiness in adolescents: a longitudinal study

STUDY OBJECTIVES

Pain symptoms, sleep disturbance, and daytime sleepiness are common in adolescents. This study examined the cross-sectional and prospective associations between pain symptoms and excessive daytime sleepiness (EDS) in a large sample of adolescents.

METHODS

Participants were 7,072 adolescents (mean age = 14.6 years) in a follow-up study of behavior and health in Shandong, China. A self-administered structured questionnaire was used to assess pain symptoms (headache, stomachache, and other general pain), body weight and height, sleep, anxiety/depression, substance use, and family environment in November-December in 2015 and one year later. The Chinese adolescent daytime sleepiness scale (CADSS) was used to measure daytime sleepiness.

RESULTS

Of the sample, 19.8% and 23.2% had moderate or severe EDS at baseline and at 1-year follow-up, respectively. The prevalence and 1-year incidence rates of EDS significantly increased with the frequencies of pain symptoms. Frequent pain was significantly associated with increased risk of EDS at baseline (OR=2.01, 95% CI=1.56-2.59), incident EDS (OR=1.41, 95% CI=1.03-1.93), and persistent EDS (OR=2.17, 95% CI=1.52-3.09) while adjusting for adolescent and family covariates, including anxiety/depression, nocturnal sleep duration, insomnia symptoms, frequent snoring, body mass index, and hypnotic use. Similar associations were observed across headache, stomachache, and other pain.

CONCLUSIONS

Frequent pain is significantly and independently associated with increased risk of EDS. Our findings suggest that assessing and treating pain symptoms is important to improve healthy sleep and reduce risk of EDS in adolescents. Further research is needed to understand the underlying psychological and neurobiological mechanisms between pain and daytime sleepiness in adolescents.

Phase II double-blind randomised controlled trial of exogenous administration of melatonin in chronic pain (DREAM-CP): a study protocol

INTRODUCTION

Chronic pain is prevalent, and approximately half of patients with chronic pain experience sleep disturbance. Exogenous melatonin is licensed to treat primary insomnia and there is some evidence for analgesic effects of melatonin.The aim of this study is to investigate the effects of oral melatonin (as Circadin) 2 mg at night in adults with severe non-malignant pain of at least 3 months' duration.

METHODS AND ANALYSIS

We will conduct a randomised double-blind placebo-controlled cross-over study. The primary outcome is sleep disturbance. Secondary outcomes are pain intensity, actigraphy, fatigue, reaction time testing, serum melatonin and endogenous opioid peptide levels along with patient views about study participation.We aim to recruit 60 patients with severe chronic pain (average pain intensity ≥7 on the Brief Pain Inventory (BPI)) from a tertiary referral pain clinic in Northeast Scotland. Participants will be randomised to receive melatonin (as modified release Circadin) 2 mg daily for 6 weeks or placebo, followed by a 4-week washout period, then 6 weeks treatment with the treatment they did not receive. Participants will complete the Verran Snyder-Halpern Sleep Scale, Pittsburgh Sleep Quality Index, Pain and Sleep Questionnaire 3-item index, BPI and psychomotor vigilance reaction time testing at 6 points over 20 weeks. Actigraphy watches will be used to provide objective measures of sleep duration and latency and other sleep measures and will prompt patients to report contemporaneous pain and fatigue scores daily.Cross-over analyses will include tests for effects of treatment, period, treatment-period interaction (carryover effect) and sequence. Within-patient effects and longitudinal data will be analysed using mixed linear models, accounting for potential confounders.

ETHICS AND DISSEMINATION

Approved by Office for Research Ethics Committees Northern Ireland, reference 19/NI/0007. Results will be published in peer-reviewed journals and will be presented at national and international conferences.

TRIAL REGISTRATION NUMBER

ISRCTN12861060.