The Effects of Low Dose Naltrexone on Opioid Induced Hyperalgesia and Fibromyalgia

Pharmacological Treatment of Fibromyalgia Syndrome: A Practice-Based Review

PURPOSE OF REVIEW

Fibromyalgia Syndrome (FMS) is a complex chronic pain condition characterized by widespread musculoskeletal pain and numerous other debilitating symptoms. The purpose of this review is to provide a comprehensive overview, based on everyday clinical practice, of the drugs presently employed in the treatment of FMS.

RECENT FINDINGS

The treatment of FMS is based on a multimodal approach, with pharmacologic treatment being an essential pillar. The drugs used include tricyclic antidepressants, serotonin and noradrenaline reuptake inhibitors, other antidepressants, anticonvulsants, myorelaxants, and analgesics. The effectiveness of these medications varies, and the choice of drug often depends on the specific symptoms presented by the patient. Many drugs tend to either address only some domains of the complex FMS symptomatology or have a limited effect on pain. Each treatment option comes with potential side effects and risks that necessitate careful consideration. It may be beneficial to divide patients into clinical subpopulations, such as FMS with comorbid depression, for more effective treatment. Despite the complexities and challenges, the pharmacological treatment remains a crucial part for the management of FMS. This review aims to guide clinicians in prescribing pharmacological treatment to individuals with FMS.

Recovery from opioid use on a neuropsychoanalytic service

Background

Little is known about recovery from opioid use disorder (OUD) or outcomes of detoxification and drug-free treatment of chronic opioid therapy (COT). Harm reduction with medications for opioid use disorder (MOUD) is regarded as the only legitimate treatment.

Methods

The Institutional Review Board (IRB) approved reporting deidentified outcomes. Patients seen over a 10-year period whose records suggested recovery were called and interviewed.

Results

Overall, 69/86 (80%) confirmed that they had been sober for at least a year, including 41 patients with OUD (75%) and 28 COT patients (90%). 91% were drug-free, and 9% were on MOUD. 79% preferred a psychotherapy approach. 21% preferred MOUD. Coming for more treatment and abstinence from tobacco were significantly correlated with recovery.

Conclusion

This is the first report that we are aware of regarding the frequency of recovery from OUD and COT. We have complicated the discussion about what is the best treatment for patients with OUD and patients on COT. Advising that maintenance is the only legitimate treatment for patients who suffer from OUD or who are on COT seems both premature and jeopardizes the ability of treaters to individualize treatment recommendations.

A Utilization Review of Patients That Respond to Low-Dose Naltrexone (LDN) for Chronic Pain at a Single Institution

Studies have demonstrated the benefits of LDN for various pain indications. This review describes the utilization of and response to LDN in patients with chronic pain within the William S. Middleton Memorial Veterans Hospital (Madison VA). This was a retrospective, single center, chart review of patients that were prescribed LDN for chronic pain. The primary outcome, change in subjective pain report via numeric rating scale (NRS), was analyzed through Wilcoxon Signed Rank Test and descriptive statistics. A total of 136 participants were included. Patients had an average pain score of 7.1 per NRS at baseline. At the initial follow up visit, participants had an average pain of 6.4 (p < 0.001). Additionally, 17.1% of patients had a greater than or equal to 30% pain reduction from baseline. At subsequent follow up, patients reported an average pain of 5.5 (p < 0.0001) per NRS. At the end of the study, 31.6% of patients were maintained on LDN at an average dose of 3.8 mg. This retrospective review demonstrated that LDN may be an effective modality for some chronic pain indications. Reported pain scores were significantly lower at initial follow up compared to baseline for the total population, and for patients with fibromyalgia (FM) specifically.

Pharmacotherapeutic advances in fibromyalgia: what's new on the horizon?

INTRODUCTION

This review delves into Fibromyalgia Syndrome (FMS), a chronic pain condition demanding thorough understanding for precise diagnosis and treatment. Yet, a definitive pharmacological solution for FMS remains elusive.

AREAS COVERED

In this article, we systematically analyze various pharmacotherapeutic prospects for FMS treatment, organized into sections based on the stage of drug development and approval. We begin with an overview of FDA-approved drugs, discussing their efficacy in FMS treatment. Next, we delve into other medications currently used for FMS but still undergoing further study, including opioids and muscle relaxants. Further, we evaluate the evidence behind medications that are currently under study, such as cannabinoids and naltrexone. Lastly, we explore new drugs that are in phase II trials. Our research involved a thorough search on PUBMED, Google Scholar, and clinicaltrials.gov. We also discuss the action mechanisms of these drugs and their potential use in specific patient groups.

EXPERT OPINION

A focus on symptom-driven, combination therapy is crucial in managing FMS. There is also a need for ongoing research into drugs that target neuroinflammation, immunomodulation, and the endocannabinoid system. Bridging the gap between benchside research and clinical application is challenging, but it holds potential for more targeted and effective treatment strategies.

Pilot RCT comparing low-dose naltrexone, gabapentin and placebo to reduce pain among people with HIV with alcohol problems

BACKGROUND

To estimate the effects on pain of two medications (low-dose naltrexone and gabapentin) compared to placebo among people with HIV (PWH) with heavy alcohol use and chronic pain.

METHODS

We conducted a pilot, randomized, double-blinded, 3-arm study of PWH with chronic pain and past-year heavy alcohol use in 2021. Participants were recruited in St. Petersburg, Russia, and randomized to receive daily low-dose naltrexone (4.5mg), gabapentin (up to 1800mg), or placebo. The two primary outcomes were change in self-reported pain severity and pain interference measured with the Brief Pain Inventory from baseline to 8 weeks.

RESULTS

Participants (N = 45, 15 in each arm) had the following baseline characteristics: 64% male; age 41 years (SD±7); mean 2 (SD±4) heavy drinking days in the past month and mean pain severity and interference were 3.2 (SD±1) and 3.0 (SD±2), respectively. Pain severity decreased for all three arms. Mean differences in change in pain severity for gabapentin vs. placebo, and naltrexone vs. placebo were -0.27 (95% confidence interval [CI] -1.76, 1.23; p = 0.73) and 0.88 (95% CI -0.7, 2.46; p = 0.55), respectively. Pain interference decreased for all three arms. Mean differences in change in pain interference for gabapentin vs. placebo, and naltrexone vs. placebo was 0.16 (95% CI -1.38, 1.71; p = 0.83) and 0.40 (95% CI -1.18, 1.99; p = 0.83), respectively.

CONCLUSION

Neither gabapentin nor low-dose naltrexone appeared to improve pain more than placebo among PWH with chronic pain and past-year heavy alcohol use.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NCT4052139).

Low-dose naltrexone's utility for non-cancer centralized pain conditions: a scoping review

BACKGROUND

At low doses, naltrexone (LDN) has been shown to modulate inflammation through the interruption of microglial cell activation within the central nervous system. One of the most likely contributors to centralized pain is changes in microglial cell processing. Therefore, it has been postulated that LDN can be used to manage patients with pain resulting from central sensitization due to this relationship. This scoping review aims to synthesize the relevant study data for LDN as a novel treatment strategy for various centralized pain conditions.

METHODS

A comprehensive literature search was conducted in PubMed, Embase, and Google Scholar, guided by the Scale for Assessment of Narrative Review Articles (SANRA) criteria.

RESULTS

Forty-seven studies related to centralized pain conditions were identified. Many of the studies were case reports/series and narrative reviews, but a few randomized control trials have been conducted. Overall, the body of evidence revealed improvement in patient-reported pain severity and in outcomes related to hyperalgesia, physical function, quality of life, and sleep. Variability in dosing paradigms and the time to patient response was present in the reviewed studies.

CONCLUSIONS

Evidence synthesized for this scoping review supports the ongoing use of LDN for the treatment of refractory pain in various centralized chronic pain conditions. Upon review of the currently available published studies, it is apparent that further high-quality, well-powered randomized control trials need to be conducted to establish efficacy, standardization for dosing, and response times. In summary, LDN continues to offer promising results in the management of pain and other distressing symptoms in patients with chronic centralized pain conditions.

Daily cannabis use may cause cannabis-induced hyperalgesia

BACKGROUND AND OBJECTIVES

Public opinion about cannabis as a medical treatment is generally favorable. As many as 35% of primary care patients report medical use of cannabis, most commonly for pain treatment. We designed a way to test whether cannabis helps chronic pain.

METHODS

A retrospective cohort study was conducted to explore whether daily long-term cannabis use was associated with increased pain sensitivity using the cold pressor test (CPT) to measure pain tolerance. Patients who used cannabis every day were compared to patients who inhaled tobacco and control patients who never used tobacco or cannabis. The effect of cannabis use on CPT was assessed using a generalized linear model.

RESULTS

Patients using cannabis daily had a median CPT of 46 s, similar to those who did not use cannabis but who inhaled tobacco (median CPT 45 s). Patients who used both cannabis and tobacco had the lowest CPT (median 26 s). The control group had a median CPT of 105 s. Cannabis use was associated with a significantly decreased pain tolerance (χ²(1)  = 8.0, p = .004). The effect of tobacco on CPT was only marginally significant (χ²(1)  = 3.8, p = .052).

CONCLUSION AND SCIENTIFIC SIGNIFICANCE

This suggests a phenomenon similar to opioid-induced hyperalgesia; a drug that reduces pain short term, induces pain long term-opponent process. Daily cannabis use may make chronic pain worse over time by reducing pain tolerance. In terms of risk/benefit, daily cannabis users risk addiction without any long-term benefit for chronic pain.

[Fibromyalgia as a Rheumatic Pain Syndrome]

Epidemiology and pathophysiology: Fibromyalgia is significantly more common in people with rheumatic diseases than in the general population. Nevertheless, it can occur independent of other diseases. Physical and psychosocial factors are responsible for the genesis for fibromyalgia making it a multifactorial disease. Most importantly, central pain processing seems to be abnormal. The relevance of a small fibre neuropathy is yet to be determined. For the very first time, a study was able to demonstrate that fibromyalgia might be passively transferred from one organism to another in an experimental setting.Diagnosis: Fibromyalgia is a clinical diagnose. Besides generalized pain, sleep disturbances and fatigue are common features. Furthermore, there can be an association with depressive disorders. Determining the Widespread Pain Index (WPI) and the Symptom Severity Score (SSS) can help in diagnosing Fibromyalgia and to determine severity of the disease.Therapy: Cornerstones of the treatment are patient education, physical exercise, physical therapy, and cognitive behavioural therapy. In therapy-resistant cases, a multimodal approach might be considered. Analgesic drugs, particularly opioids, should basically be avoided or only be used for a short period of time. Naltrexone, an opioid antagonist, is a promising treatment candidate. Another possible approach might be the use of TENS. While there are positive observational studies on the therapeutic use of cannabinoids, evidence from controlled trials is still missing.

Low-dose naltrexone for treatment of pain in patients with fibromyalgia: a randomized, double-blind, placebo-controlled, crossover study

Introduction

Fibromyalgia (FM) is a chronic fluctuating, nociplastic pain condition. Naltrexone is a µ-opioid-receptor antagonist; preliminary studies have indicated a pain-relieving effect of low-dose naltrexone (LDN) in patients with FM. The impetus for studying LDN is the assumption of analgesic efficacy and thus reduction of adverse effects seen from conventional pharmacotherapy.

Objectives

First, to examine if LDN is associated with analgesic efficacy compared with control in the treatment of patients with FM. Second, to ascertain the analgesic efficacy of LDN in an experimental pain model in patients with FM evaluating the competence of the descending inhibitory pathways compared with controls. Third, to examine the pharmacokinetics of LDN.

Methods

The study used a randomized, double-blind, placebo-controlled, crossover design and had a 3-phase setup. The first phase included baseline assessment and a treatment period (days -3 to 21), the second phase a washout period (days 22-32), and the third phase a baseline assessment followed by a treatment period (days 33-56). Treatment was with either LDN 4.5 mg or an inactive placebo given orally once daily. The primary outcomes were Fibromyalgia Impact Questionnaire revised (FIQR) scores and summed pain intensity ratings (SPIR).

Results

Fifty-eight patients with FM were randomized. The median difference (IQR) for FIQR scores between LDN and placebo treatment was -1.65 (18.55; effect size = 0.15; P = 0.3). The median difference for SPIR scores was -0.33 (6.33; effect size = 0.13; P = 0.4).

Conclusion

Outcome data did not indicate any clinically relevant analgesic efficacy of the LDN treatment in patients with FM.

Opiate Antagonists for Chronic Pain: A Review on the Benefits of Low-Dose Naltrexone in Arthritis versus Non-Arthritic Diseases

Chronic pain conditions create major financial and emotional burdens that can be devastating for individuals and society. One primary source of pain is arthritis, a common inflammatory disease of the joints that causes persistent pain in affected people. The main objective of pharmacological treatments for either rheumatoid arthritis (RA) or osteoarthritis (OA) is to reduce pain. Non-steroidal anti-inflammatory drugs, opioids, and opioid antagonists have each been considered in the management of chronic pain in arthritis patients. Naltrexone is an oral-activated opioid antagonist with biphasic dose-dependent pharmacodynamic effects. The molecule acts as a competitive inhibitor of opioid receptors at high doses. However, naltrexone at low doses has been shown to have hormetic effects and provides relief for chronic pain conditions such as fibromyalgia, multiple sclerosis (MS), and inflammatory bowel disorders. Current knowledge of naltrexone suggests that low-dose treatments may be effective in the treatment of pain perception in chronic inflammatory conditions observed in patients with either RA or OA. In this review, we evaluated the therapeutic benefits of low-dose naltrexone (LDN) on arthritis-related pain conditions.

Endogenous opiates and behavior: 2021

This paper is the forty-fourth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2021 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonizts and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Low-Dose Naltrexone in Rheumatological Diseases

Background

Naltrexone has been approved for alcohol and opioid abuse by the FDA. At low-dose naltrexone (LDN) has been used in several diseases including chronic pain and autoimmune conditions, including rheumatic disorders.

Aim

To review the use of LDN in rheumatic diseases: systemic sclerosis (SSc), dermatomyositis (DM), Sjögren's syndrome (SS), rheumatoid arthritis (RA), and fibromyalgia (FM).

Methods

PubMed and Embase databases were searched for articles on LDN and rheumatic diseases between 1966 and August 2022.

Results

Seven studies in FM have been identified: in this disease LDN has showed beneficial effects on pain and well-being. In SS, two articles with 3 cases description showed that LDN may be of help in the pain treatment. LDN relieved pruritus in scleroderma (a case description with a series of 3 patients) and dermatomyositis (description of 3 patients in two articles). In RA a study using Norwegian Prescription Database showed that LDN was associated to reduction in the use of analgesic and DMARDs. No serious side effects were detected.

Conclusion

This review shows that LDN is a promising and safe therapy to be used in some rheumatic disease. However, the data is limited and needs to be reproduced in larger studies.

Contemporary management of pain in cirrhosis: Toward precision therapy for pain

Chronic pain is highly prevalent in patients with cirrhosis and is associated with poor health-related quality of life and poor functional status. However, there is limited guidance on appropriate pain management in this population, and pharmacologic treatment can be harmful, leading to adverse outcomes, such as gastrointestinal bleeding, renal injury, falls, and hepatic encephalopathy. Chronic pain can be categorized mechanistically into three pain types: nociceptive, neuropathic, and nociplastic, each responsive to different therapies. By discussing the identification, etiology, and treatment of these three mechanistic pain descriptors with a focus on specific challenges in patients with cirrhosis, we provide a framework for better tailoring treatments, including nonpharmacologic therapies, to patients' needs.

The Safety and Efficacy of Low-Dose Naltrexone in Patients with Fibromyalgia: A Systematic Review

Fibromyalgia (FM) is a chronic pain sensitivity syndrome characterized by diffuse musculoskeletal pain and many other systemic manifestations. Low-dose naltrexone (LDN) has been increasingly used as an off-label treatment option in FM. However, current evidence on the safety and efficacy of LDN in patients with FM is not well known. To systematically assess the current evidence on the safety and efficacy of LDN use in the treatment of FM. A comprehensive bibliographic search was conducted on EBM Reviews - Cochrane Central Register of Controlled Trials, EBM Reviews - Cochrane Database of Systematic, Embase, Ovid MEDLINE(R) and Epub Ahead of Print, In-Process, In-Data-Review & Other Non-Indexed Citations, Daily and Versions and Scopus databases in September 2022. Inclusion criteria were articles that were published in English, focusing on clinical trials involving LDN for the treatment of FM. Two reviewers independently screened and extracted the data. A qualitative analysis was used due to the high methodological heterogeneity between studies. The electronic search produced 805 articles. After applying the inclusion criteria, 9 articles (one RCT, two case reports, two case series, and four pilot trials) were selected for evaluation. LDN intervention protocols, study designs, and follow-up periods were different among the included studies. Overall, LDN was found to be effective in the symptomatic management of FM, and of the 78% of included studies that evaluated for safety, no severe adverse events were reported. Proving the efficacy and safety of low-dose naltrexone is a future possibility based on current study data, but the level of scientific evidence is limited. Future well-designed trials with large sample sizes are required.

Knowing the Enemy Is Halfway towards Victory: A Scoping Review on Opioid-Induced Hyperalgesia

Opioid-induced hyperalgesia (OIH) is a paradoxical effect of opioids that is not consensually recognized in clinical settings. We conducted a revision of clinical and preclinical studies and discuss them side by side to provide an updated and renewed view on OIH. We critically analyze data on the human manifestations of OIH in the context of chronic and post-operative pain. We also discuss how, in the context of cancer pain, though there are no direct evidence of OIH, several inherent conditions to the tumor and chemotherapy provide a substrate for the development of OIH. The review of the clinical data, namely in what concerns the strategies to counter OIH, emphasizes how much OIH rely mechanistically on the existence of µ-opioid receptor (MOR) signaling through opposite, inhibitory/antinociceptive and excitatory/pronociceptive, pathways. The rationale for the maladaptive excitatory signaling of opioids is provided by the emerging growing information on the functional role of alternative splicing and heteromerization of MOR. The crossroads between opioids and neuroinflammation also play a major role in OIH. The latest pre-clinical data in this field brings new insights to new and promising therapeutic targets to address OIH. In conclusion, although OIH remains insufficiently recognized in clinical practice, the appropriate diagnosis can turn it into a treatable pain disorder. Therefore, in times of scarce alternatives to opioids to treat pain, mainly unmanageable chronic pain, increased knowledge and recognition of OIH, likely represent the first steps towards safer and efficient use of opioids as analgesics.

Evaluation by Survival Analysis of Cold Pain Tolerance in Patients with Fibromyalgia and Opioid Use

Purpose

The cold pressor test (CPT) is a clinical pain research method used to measure cold pain tolerance. During this test, participants immerse an extremity (ie, hand or foot) into cold water for as long as tolerable. The duration of the test (traditionally up to an experimentally imposed cut-off at 2 minutes) indicates the amount of cold pain tolerance by the participant. Prior research studies have investigated cold pain tolerance in patients with chronic pain. However, few of these studies have used survival analysis, which allows for proper handling of data censoring and is therefore, an optimal statistical method for CPT data analysis. The goal of the present study was to use survival analysis to evaluate cold pain tolerance in patients with fibromyalgia. Furthermore, we aimed to model relationships between psychological and clinical variables as well as opioid medication use and cold pain tolerance.

Patients and Methods

A total of 85 patients with fibromyalgia (42 who were taking opioids) and 47 healthy pain-free controls provided CPT and questionnaire data (collected across 2 study sites) for a case-control study. We used survival analysis using Cox regression to evaluate group differences (patients vs controls) in cold pain tolerance and to evaluate cold pain tolerance relationships with psychological, clinical, and medication use.

Results

As compared to healthy controls, patients with fibromyalgia exhibited significantly lower CPT survival (HR = 2.17, 95% CI: [1.42, 3.31], p = 0.00035). As indicated by Cox regression models, the significant group difference in CPT survival did not relate to our selected psychological and clinical measures (p > 0.05). The groups of non-opioid-taking patients and healthy controls showed consistent CPT survival across study sites. However, patients taking opioid pain medications showed differences in CPT survival across study sites.

Conclusion

By using survival analysis, an optimal method for time-to-event pain measures such as the CPT, we confirmed previously identified reductions in cold pain tolerance in patients with fibromyalgia. While our selected psychological and clinical measures were not significantly associated with cold pain tolerance, our data suggest that opioid medication use may impart greater cold pain tolerance in some patients.

Neuropathic ocular surface pain: Emerging drug targets and therapeutic implications

INTRODUCTION

Dysfunction at various levels of the somatosensory system can lead to ocular surface pain with a neuropathic component. Compared to nociceptive pain (due to noxious stimuli at the ocular surface), neuropathic pain tends to be chronic and refractory to therapies, making it an important source of morbidity in the population. An understanding of the options available for neuropathic ocular surface pain, including new and emerging therapies, is thus an important topic.

AREAS COVERED

This review will examine studies focusing on ocular surface pain, emphasizing those examining patients with a neuropathic component. Attention will be placed toward recent (after 2017) studies that have examined new and emerging therapies for neuropathic ocular surface pain.

EXPERT OPINION

Several therapies have been studied thus far, and continued research is needed to identify which individuals would benefit from specific therapies. Gaps in our understanding exist, especially with availability of in-clinic diagnostics for neuropathic pain. A focus on improving diagnostic capabilities and researching gene-modulating therapies could help us to provide more specific mechanism-based therapies for patients. In the meantime, continuing to uncover new modalities and examining which are likely to work depending on pain phenotype remains an important short-term goal.

Depression in Fibromyalgia Patients May Require Low-Dose Naltrexone to Respond: A Case Report

Fibromyalgia and depression are frequently comorbid. We propose a hormonal system model in understanding the underlying endogenous opioid system dysregulation in fibromyalgia with the utilization of the cold pressor test (CPT) in clinical practice to monitor treatment response to low-dose naltrexone (LDN) and the subsequent remission of major depressive disorder by restoring opioid tone.

A 60-year-old professional on permanent disability presented with refractory depression and chronic widespread pain after years of multiple failed medication trials. Rating scales confirmed severe depression, Hamilton Rating Scale for Depression (HAM-D) of 20, a short cold pressor test (CPT) time of 21 seconds, and a face pain scale (FPS) of 8/10. Physical examination assessing for fibromyalgia was diagnostic, with 18/18 positive tender points.

LDN, a minor increase in trazodone, and transference-focused psychotherapy were employed. The patient’s CPT time increased modestly. The patient achieved remission of both conditions in 10 weeks when both disorders were treated at once (FPS and HAM-D of zero), restoring the quality of life, relatedness, and motivation.

Some fibromyalgia patients may achieve remission of comorbid depression with concomitant low-dose naltrexone (LDN) treatment that is widely used “off label” to treat pain. LDN is a promising alternative for the treatment of chronic pain in fibromyalgia with its safety profile, high tolerability, and absence of abuse potential. Our unique finding is that without successful LDN treatment of fibromyalgia, remission of depression may be unlikely.

Study protocol for a randomised, double-blinded, placebo-controlled phase III trial examining the add-on efficacy, cost-utility and neurobiological effects of low-dose naltrexone (LDN) in patients with fibromyalgia (INNOVA study)

INTRODUCTION

There is evidence that low-dose naltrexone (LDN; <5.0 mg/day) reduces pain and improves the quality of life of people with fibromyalgia syndrome (FMS). However, no randomised controlled trials with long-term follow-ups have been carried out. The INNOVA study will evaluate the add-on efficacy, safety, cost-utility and neurobiological effects of LDN for reducing pain in patients with FMS, with a 1-year follow-up.

METHODS AND ANALYSIS

A single-site, prospective, randomised, double-blinded, placebo-controlled, parallel design phase III trial will be performed. Eligibility criteria include being adult, having a diagnosis of FMS and experiencing pain of 4 or higher on a 10-point numerical rating scale. Participants will be randomised to a LDN intervention group (4.5 mg/day) or to a placebo control group. Clinical assessments will be performed at baseline (T0), 3 months (T1), 6 months (T2) and 12 months (T3). The primary endpoint will be pain intensity. A sample size of 60 patients per study arm (120 in total), as calculated prior to recruitment for sufficient power, will be monitored between January 2022 and August 2024. Assessment will also include daily ecological momentary evaluations of FMS-related symptoms (eg, pain intensity, fatigue and sleep disturbance), and side effects via ecological momentary assessment through the Pain Monitor app during the first 3 months. Costs and quality-adjusted life years will be also calculated. Half of the participants in each arm will be scanned with MRI at T0 and T1 for changes in brain metabolites related to neuroinflammation and central sensitisation. Inflammatory biomarkers in serum will also be measured.

ETHICS AND DISSEMINATION

This study has been approved by the Ethics Committee of the Fundació Sant Joan de Déu. The results will be actively disseminated through peer-reviewed journals, conference presentations, social media and community engagement activities.

TRIAL REGISTRATION NUMBER

NCT04739995.

Differential Effects of Treatment Strategies in Individuals With Chronic Ocular Surface Pain With a Neuropathic Component

Background: Dysfunction at the ocular system via nociceptive or neuropathic mechanisms can lead to chronic ocular pain. While many studies have reported on responses to treatment for nociceptive pain, fewer have focused on neuropathic ocular pain. This retrospective study assessed clinical responses to pain treatment modalities in individuals with neuropathic component ocular surface pain. Methods: 101 individuals seen at the University of Miami Oculofacial Pain Clinic from January 2015 to August 2021 with ≥3 months of clinically diagnosed neuropathic pain were included. Patients were subcategorized (postsurgical, post-traumatic, migraine-like, and laterality) and self-reported treatment outcomes were assessed (no change, mild, moderate, or marked improvement). One-way ANOVA (analysis of variance) was used to examine relationships between follow up time and number of treatments attempted with pain improvement, and multivariable logistic regression was used to assess which modalities led to pain improvement. Results: The mean age was 55 years, and most patients were female (64.4%) and non-Hispanic (68.3%). Migraine-like pain (40.6%) was most common, followed by postsurgical (26.7%), post-traumatic (16.8%) and unilateral pain (15.8%). The most common oral therapies were α2δ ligands (48.5%), the m common topical therapies were autologous serum tears (20.8%) and topical corticosteroids (19.8%), and the most common adjuvant was periocular nerve block (24.8%). Oral therapies reduced pain in post-traumatic (81.2%), migraine-like (73%), and unilateral (72.7%) patients, but only in a minority of postsurgical (38.5%) patients. Similarly, topicals improved pain in post-traumatic (66.7%), migraine-like (78.6%), and unilateral (70%) compared to postsurgical (43.7%) patients. Non-oral/topical adjuvants reduced pain in postsurgical (54.5%), post-traumatic (71.4%), and migraine-like patients (73.3%) only. Multivariable analyses indicated migraine-like pain improved with concomitant oral α2δ ligands and adjuvant therapies, while postsurgical pain improved with topical anti-inflammatories. Those with no improvement in pain had a shorter mean follow-up (266.25 ± 262.56 days) than those with mild (396.65 ± 283.44), moderate (652 ± 413.92), or marked improvement (837.93 ± 709.35) (p < 0.005). Identical patterns were noted for number of attempted medications. Conclusion: Patients with migraine-like pain frequently experienced pain improvement, while postsurgical patients had the lowest response rates. Patients with a longer follow-up and who tried more therapies experienced more significant relief, suggesting multiple trials were necessary for pain reduction.

Low-Dose Naltrexone Co-Treatment in the Prevention of Opioid-Induced Hyperalgesia

Opioid-induced hyperalgesia (OIH) is characterized by a heightened sensitivity to pain that occurs in patients following opioid use. Prescription of opioids is currently the standard form of pain management for both neuropathic and nociceptive pain, due to the relief that patients typically report following their use. Opioids, which aim to provide analgesic effects, can paradoxically cause increasing degrees of pain among the users. The increased nociception can be either due to the underlying pain for which the opioid was initially prescribed, or other unrelated pain. As a result, those who are initially prescribed opioids for chronic pain relief may instead be left with no overall relief, and experience additional algesia. While OIH can be treated through the reduction of opioid use, antagonistic treatment can also be utilized. In an attempt to reduce OIH in patients, low doses of the opioid antagonist naltrexone can be given concurrently. This review will analyze the current role and effectiveness of the use of naltrexone in managing OIH in opioid users as described in clinical and non-clinical studies. Additionally, it seeks to characterize the underlying mechanisms that enable opioid antagonist naltrexone to reduce OIH while still allowing opioids to act as an analgesic. The authors find that OIH is a prevalent condition, and in order to effectively combat it, clinicians and patients can benefit from an extended study on how naltrexone can be utilized as a treatment alongside opioids prescribed for pain management.