Effect of Intravenous Ethanol on Capsaicin-Induced Hyperalgesia in Human Subjects

Alcohol Use Disorder and Chronic Pain: An Overlooked Epidemic

Alcohol use disorder (AUD) and chronic pain disorders are pervasive, multifaceted medical conditions that often co-occur. However, their comorbidity is often overlooked, despite its prevalence and clinical relevance. Individuals with AUD are more likely to experience chronic pain than the general population. Conversely, individuals with chronic pain commonly alleviate their pain with alcohol, which may escalate into AUD. This narrative review discusses the intricate relationship between AUD and chronic pain. Based on the literature available, the authors present a theoretical model explaining the reciprocal relationship between AUD and chronic pain across alcohol intoxication and withdrawal. They propose that the use of alcohol for analgesia rapidly gives way to acute tolerance, triggering the need for higher levels of alcohol consumption. Attempts at abstinence lead to alcohol withdrawal syndrome and hyperalgesia, increasing the risk of relapse. Chronic neurobiological changes lead to preoccupation with pain and cravings for alcohol, further entrenching both conditions. To stimulate research in this area, the authors review methodologies to improve the assessment of pain in AUD studies, including self-report and psychophysical methods. Further, they discuss pharmacotherapies and psychotherapies that may target both conditions, potentially improving both AUD and chronic pain outcomes simultaneously. Finally, the authors emphasize the need to manage both conditions concurrently, and encourage both the scientific community and clinicians to ensure that these intertwined conditions are not overlooked given their clinical significance.

Efficacy and Safety of Inhalation of Nebulized Ethanol in COVID-19 Treatment: A Randomized Clinical Trial

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a pandemic caused by the SARS-CoV-2 virus. Many efforts have been made and are currently being made to prevent and treat this global disease.

OBJECTIVES

This study was designed to evaluate the efficacy and safety of nebulized ethanol (EtOH) in treating COVID-19.

METHODS

A randomized clinical trial (RCT) of 99 symptomatic and real-time polymerase chain reaction (RT-PCR)-positive patients admitted to a hospital receiving remdesivir-dexamethasone was conducted. They were randomly assigned to receive distilled water spray (control group (CG)) or 35% EtOH spray (intervention group (IG)). Both groups inhaled three puffs of spray (nebulizer) every six hours for a week. The primary outcome included Global Symptomatic Score (GSS) between the two groups at the first visit and on days three, seven, and 14. Secondary outcomes included the Clinical Status Scale (CSS; a seven-point ordinal scale ranging from death to complete recovery) and readmission rate.

RESULTS

A total of 44 and 55 patients were enrolled in the IG and CG, respectively. Although there was no difference at admission, the GSS and CSS improved significantly in the IG (p = 0.016 and p = 0.001, respectively). The IG readmission rate was considerably lower (0% vs. 10.9%; p = 0.02).

CONCLUSIONS

Inhaled-nebulized EtOH is effective in rapidly improving the clinical status and reducing further treatment. Due to its low cost, availability, and absent/tolerable adverse events, it could be recommended as an adjunctive treatment for moderate COVID-19. Further research on curative effects in more serious cases and in prevention is advisable.

Therapeutic potential of GHSR-1A antagonism in alcohol dependence, a review

Growth hormone secretagogue receptor type 1A (GHSR-1A) is a functional receptor of orexigenic peptide ghrelin and is highly expressed in mesolimbic dopaminergic systems that regulate incentive value of artificial reward in substance abuse. Interestingly, GHSR-1A has also shown ligand-independent constitutive activity. Alcohol use disorder (AUD) is one of the growing concerns worldwide as it involves complex neuro-psycho-endocrinological interactions. Positive correlation of acylated ghrelin and alcohol-induced human brain response in the right and left ventral striatum are evident. In the last decade, the beneficial effects of ghrelin receptor (GHSR-1A) antagonism to suppress artificial reward circuitries and induce self-control for alcohol consumption have drawn significant attention from researchers. In this updated review, we summarize the available recent preclinical, clinical, and experimental data to discuss functional, molecular actions of central ghrelin-GHSR-1A signaling in different craving levels for alcohol as well as to promote "GHSR-1A antagonism" as one of the potential therapies in early abstinence.

Human surrogate models of central sensitization: A critical review and practical guide

Background

As in other fields of medicine, development of new medications for management of neuropathic pain has been difficult since preclinical rodent models do not necessarily translate to the clinics. Aside from ongoing pain with burning or shock‐like qualities, neuropathic pain is often characterized by pain hypersensitivity (hyperalgesia and allodynia), most often towards mechanical stimuli, reflecting sensitization of neural transmission.

Data treatment

We therefore performed a systematic literature review (PubMed‐Medline, Cochrane, WoS, ClinicalTrials) and semi‐quantitative meta‐analysis of human pain models that aim to induce central sensitization, and generate hyperalgesia surrounding a real or simulated injury.

Results

From an initial set of 1569 reports, we identified and analysed 269 studies using more than a dozen human models of sensitization. Five of these models (intradermal or topical capsaicin, low‐ or high‐frequency electrical stimulation, thermode‐induced heat‐injury) were found to reliably induce secondary hyperalgesia to pinprick and have been implemented in multiple laboratories. The ability of these models to induce dynamic mechanical allodynia was however substantially lower. The proportion of subjects who developed hypersensitivity was rarely provided, giving rise to significant reporting bias. In four of these models pharmacological profiles allowed to verify similarity to some clinical conditions, and therefore may inform basic research for new drug development.

Conclusions

While there is no single “optimal” model of central sensitization, the range of validated and easy‐to‐use procedures in humans should be able to inform preclinical researchers on helpful potential biomarkers, thereby narrowing the translation gap between basic and clinical data.

Significance

Being able to mimic aspects of pathological pain directly in humans has a huge potential to understand pathophysiology and provide animal research with translatable biomarkers for drug development. One group of human surrogate models has proven to have excellent predictive validity: they respond to clinically active medications and do not respond to clinically inactive medications, including some that worked in animals but failed in the clinics. They should therefore inform basic research for new drug development.

The role of alcohol consumption in pathogenesis of gout

Alcohol is recognized a risk factor for increased uric acid and gout flare. The aim of the study was to review the literature in order to find out what is the role of alcohol consumption in pathogenesis of gout. A search in PubMed, Google Scholar, Medline Complete database was performed in January 2021. The databases were searched with the phrases: "uric acid and alcohol," "alcoholic beverages and gout," "hyperuricemia and alcoholic beverages consumption" published between 2000 and 2021. A total of 2642 results were found. The 99 non-duplicate citations were screened. Then 81 articles were excluded after abstract screen. After that 18 articles were retrieved. Eventually 15 articles were included for systematic review. Several authors see the positive correlation between beer or distilled spirits consumption and gout. Some include wine to the list of triggers of gout. Others state that moderate wine consumption protects from gout attacks due to antioxidants and phytoestrogen content. Majority noticed the relationship between episodic alcohol consumption and gout attacks. Episodic alcohol intake triggers gout attacks, regardless of type of alcohol. Thus, individuals with established gout and pre-existing risk factors should limit all types of alcohol intake to prevent gout episodes.

The Sigma-2 receptor / transmembrane protein 97 (σ2R/TMEM97) modulator JVW-1034 reduces heavy alcohol drinking and associated pain states in male mice

Alcohol Use Disorder (AUD) is a chronic relapsing disorder characterized by compulsive alcohol intake, loss of control over alcohol intake, and a negative emotional state when access to alcohol is prevented. AUD is also closely tied to pain, as repeated alcohol drinking leads to increased pain sensitivity during withdrawal. The sigma-2 receptor, recently identified as transmembrane protein 97 (σ2R/TMEM97), is an integral membrane protein involved in cholesterol homeostasis and lipid metabolism. Selective σ2R/Tmem97 modulators have been recently shown to relieve mechanical hypersensitivity in animal models of neuropathic pain as well as to attenuate alcohol withdrawal signs in C. elegans and to reduce alcohol drinking in rats, suggesting a potential key role for this protein in alcohol-related behaviors. In this study, we tested the effects of a potent and selective σ2R/TMEM97 ligand, JVW-1034, on heavy alcohol drinking and alcohol-induced heightened pain states in mice using an intermittent access model. Administration of JVW-1034 decreased both ethanol intake and preference for ethanol, without affecting water intake, total fluid intake, or food intake. Notably, this effect was specific for alcohol, as JVW-1034 had no effect on sucrose intake. Furthermore, JVW-1034 reduced both thermal hyperalgesia and mechanical hypersensitivity in ethanol withdrawn mice. Our data provide important evidence that modulation of σ2R/TMEM97 with small molecules can mediate heavy alcohol drinking as well as chronic alcohol-induced heightened pain sensitivity, thereby identifying a promising novel pharmacological target for AUD and associated pain states.

Neurobiological aspects of pain in the context of alcohol use disorder

Alcohol is an effective and widely utilized analgesic. However, the chronic use of alcohol can actually facilitate nociceptive sensitivity over time, a condition known as hyperalgesia. Excessive and uncontrollable alcohol drinking is also a hallmark feature of alcohol use disorder (AUD). Both AUD and chronic pain are typically accompanied by negative affective states that may underlie reinforcement mechanisms contributing to AUD maintenance or progression. Frequent utilization of alcohol to relieve pain in individuals suffering from AUD or other chronic pain conditions may thus represent a powerful negative reinforcement construct. This chapter will describe ties between alcohol-mediated pain relief and potential exacerbation of AUD. We describe neurobiological systems engaged in alcohol analgesia as well as systems recruited in the development and maintenance of AUD and hyperalgesia. Although few effective therapies exist for either chronic pain or AUD, the common interaction of these conditions will likely lead the way for promising new discoveries of more effective and even simultaneous treatment of AUD and co-morbid hyperalgesia. An abundance of neurobiological findings from multiple laboratories has implicated a potentiation of central amygdala (CeA) signaling in both pain and AUD, and these data also suggest that attenuation of stress-related systems (including corticotropin-releasing factor, vasopressin, and glucocorticoid receptor activity) would be particularly effective and comprehensive therapeutic strategies targeting the critical intersection of somatic and motivational mechanisms driving AUD, including alcohol-induced hyperalgesia.

Effects of oral alcohol administration on heat pain threshold and ratings of supra-threshold stimuli

Background and aims Evidence for analgesic effects of oral alcohol consumption on heat pain has recently been documented in a placebo-controlled, randomized and double-blind design. We aimed at further investigating these effects and now set the focus on pain threshold and the ratings of supra-threshold pain to cover most of the pain range. Moreover, we now firstly evaluated sex differences in these effects. Methods We investigated 41 healthy participants (22 females) in a randomized, double-blind and placebo-controlled design and targeted two different moderate breath-alcohol levels of 0.06% and 0.08%. Before and after an alcoholic or placebo drink, contact heat was applied at the forearm. Subjects evaluated pain threshold (method of adjustment) and rated pain intensity and pain unpleasantness of supra-threshold stimuli (intensity: threshold +3 °C; duration: 5 s). Results Analgesic effects taking the form of increased pain thresholds were found after both alcohol doses, surprisingly with more pronounced effects for the lower dose. While the high alcohol dose exerted small analgesic effects on pain intensity ratings (i.e. decrease), slightly increased ratings of pain intensity and pain unpleasantness after the low alcohol dose rather suggest pain enhancement. Alcohol did not affect intensity vs. unpleasantness ratings differentially. We found no evidence for sex differences in any of these effects. Conclusions Overall, acute alcohol effects on pain were subtle. Our findings suggest that while low alcohol doses already exert analgesic effects on pain threshold, stronger doses are required for pain reduction on supra-threshold pain levels. Furthermore, sex differences could not be detected within our experimental paradigm but should be further explored in future research. Implications Analgesic effects of sub-toxic alcohol doses - as normally occurring during social drinking - might be weak; however, susceptibility to pain relieving effects of alcohol might be a risk factor for the use of alcohol as self-medication in acute pain states.

Acute alcohol effects on conditioned pain modulation, but not temporal summation of pain

Although pain reduction after alcohol administration has repeatedly been demonstrated, alcohol effects on advanced and clinically relevant dynamic pain paradigms are still unknown. As such, temporal summation of pain (TSP) and conditioned pain modulation (CPM) indicate mechanisms of endogenous pain modulation and involve certain neurotransmitter systems crucially influenced by alcohol. Our study is the first to investigate acute alcohol effects on TSP and CPM. We investigated 39 healthy subjects in a placebo-controlled within-subject design and targeted alcohol levels of 0.06% (dose 1) and 0.08% (dose 2). Pain threshold, TSP, and CPM were evaluated before and after an alcoholic or placebo drink. Temporal summation of pain was assessed as enhanced pain response to 5 repetitive contact heat stimuli (threshold +3°C). Conditioned pain modulation was tested as pain inhibition when a conditioning stimulus (46°C hot water) was applied concurrently to a test stimulus (contact heat; threshold + 3°C). Both alcohol doses boosted CPM, with a greater effect size for the higher dose. Conditioning stimulus ratings increased after alcohol intake but were not correlated with CPM, suggesting independence of these effects. Temporal summation of pain was not affected by alcohol, and alcohol effects on pain threshold were small and limited to the higher dose. Our findings suggest that analgesic alcohol effects might be mainly driven by an enhancement of endogenous pain inhibition. The frequent use of alcohol as self-medication in chronic pain might be motivated by alcohol temporarily restoring deficient CPM, thus leading to pain relief in the short run and alcohol-related problems in the long run.

From Pleasure to Pain, and Back Again: The Intricate Relationship Between Alcohol and Nociception

AIMS

A close and bidirectional relationship between alcohol consumption and pain has been previously reported and discussed in influential reviews. The goal of the present narrative review is to provide an update on the developments in this field in order to guide future research objectives.

METHODS

We evaluated both epidemiological and neurobiological literature interrogating the relationship between alcohol use and pain for the presence of significant effects. We outlined studies on interactions between alcohol use and pain using both self-reports and objective experimental measures and discussed potential underlying mechanisms of these interactions.

RESULTS

Epidemiological, preclinical and clinical literature point to three major interactions between alcohol use and pain: (a) alcohol use leading to hyperalgesia, (b) alcohol use moderating pain and hyperalgesia and (c) chronic pain as a risk factor predisposing to alcohol relapse. Neurobiological studies using animal models to assess these interactions have transitioned from mostly involuntary modes of experimenter-controlled alcohol administration to self-administration procedures, and increasingly indicate that neuronal circuits implicated in both withdrawal and anticipation stages of alcohol use disorder also have a role in chronic pain. Mechanistically, alterations in GABA, glutamate, the corticotropin-releasing factor system, endogenous opioids and protein kinase C appear to play crucial roles in this maladaptive overlap.

CONCLUSIONS

Many of the principles explaining the interactions between alcohol and pain remain on a strong foundation, but continuing progress in modeling these interactions and underlying systems will provide a clearer basis for understanding, and ultimately treating, the damaging aspects of this interaction.

Thiopental Does Not Produce Hyperalgesia: A Laboratory Study Using Two Human Experimental Pain Models

Objective

Past investigations assessing the effects of thiopental on pain are conflicting. Although several studies demonstrate hyperalgesia as a result of barbiturate administration, others show analgesia. Our objective was to assess the effects of an infusion of the GABAA agonist thiopental, compared with placebo, in healthy participants on two subjective experimental pain paradigms: noxious electrical stimulation and intradermal capsaicin.

Methods

For electrical stimulation, the milliamps required to achieve pain threshold and tolerance were recorded, and the percent change from baseline was determined for each infusion condition. In the intradermal capsaicin condition, the area of hyperalgesia was determined by von Frey technique pre- and postinfusion, and the percent change in the area of hyperalgesia was calculated.

Results

Though thiopental infusion resulted in an increase in the electrical stimulation current required to elicit pain threshold or reach pain tolerance when compared with baseline, this finding was not statistically significant. In the intradermal capsaicin condition, there was a statistically significant difference in overall pre- and postinfusion pain interpretation, as measured by the McGill Pain Questionnaire (P < 0.05), but there was no significant difference in area of hyperalgesia.

Conclusions

In this human study of thiopental’s effects on two experimental pain models, our results show that thiopental does not induce hyperalgesia.

Alcohol and Pain: A Translational Review of Preclinical and Clinical Findings to Inform Future Treatment Strategies

Alcohol use disorder (AUD) and chronic pain are enduring and devastating conditions that share an intersecting epidemiology and neurobiology. Chronic alcohol use itself can produce a characteristic painful neuropathy, while the regular analgesic use of alcohol in the context of nociceptive sensitization and heightened affective pain sensitivity may promote negative reinforcement mechanisms that underlie AUD maintenance and progression. The goal of this review was to provide a broad translational framework that communicates research findings spanning preclinical and clinical studies, including a review of genetic, molecular, behavioral, and social mechanisms that facilitate interactions between persistent pain and alcohol use. We also consider recent evidence that will shape future investigations into novel treatment mechanisms for pain in individuals suffering from AUD.

A data science approach to the selection of most informative readouts of the human intradermal capsaicin pain model to assess pregabalin effects

Persistent and, in particular, neuropathic pain is a major healthcare problem with still insufficient pharmacological treatment options. This triggered research activities aimed at finding analgesics with a novel mechanism of action. Results of these efforts will need to pass through the phases of drug development, in which experimental human pain models are established components e.g. implemented as chemical hyperalgesia induced by capsaicin. We aimed at ranking the various readouts of a human capsaicin-based pain model with respect to the most relevant information about the effects of a potential reference analgesic. In a placebo-controlled, randomized cross-over study, seven different pain-related readouts were acquired in 16 healthy individuals before and after oral administration of 300 mg pregabalin. The sizes of the effect on pain induced by intradermal injection of capsaicin were quantified by calculating Cohen's d. While in four of the seven pain-related parameters, pregabalin provided a small effect judged by values of Cohen's d exceeding 0.2, an item categorization technique implemented as computed ABC analysis identified the pain intensities in the area of secondary hyperalgesia and of allodynia as the most suitable parameters to quantify the analgesic effects of pregabalin. Results of this study provide further support for the ability of the intradermal capsaicin pain model to show analgesic effects of pregabalin. Results can serve as a basis for the designs of studies where the inclusion of this particular pain model and pregabalin is planned.

Pharmacological mechanisms of alcohol analgesic-like properties in mouse models of acute and chronic pain

Alcohol use and chronic pain are highly comorbid. Acute alcohol use typically produces an analgesic effect. However, chronic use can worsen the progression of chronic pain. In rodent models, acute models of pain have primarily been used to investigate the relationship between alcohol and pain analgesia. Here, we use two models of chronic pain, chronic inflammatory and peripheral neuropathic pain, to investigate acute alcohol's antinociceptive and analgesic properties. We hypothesize that acute ethanol is acting through opioid receptors to create an analgesic-like effect in both reflexive and affective dimensions of pain. Using male and female C57BL/6J mice, oral ethanol administration (0-1.25 g/kg) showed a dose-dependent reversal of mechanical hypersensitivity in both Complete Freund's Adjuvant (CFA) and chronic constriction injury (CCI) models of chronic inflammatory and neuropathic pain. No sex differences were observed. Using the conditioned place preference (CPP) task to assess the subjective responses to ethanol's anti-nociceptive properties, CCI-injured animals showed a preference for the ethanol-paired side, suggesting a reduction in an aversive and pain-like state produced by nerve injury. These effects are likely mediated through the kappa and possibly the mu opioid systems, since ethanol-induced anti-nociception following CCI was fully reversed by pretreatment with the kappa selective antagonist, nor-BNI, or high doses of naltrexone. These data show that ethanol possesses analgesic-like properties in chronic inflammatory and neuropathic pain models in mice and provide new insight into ethanol as it relates to chronic pain.

Capsaicin: Physicochemical properties, cutaneous reactions and potential applications in painful and inflammatory conditions

Capsaicin is a natural protoalkaloid recognized as the main pungent component in hot peppers (Capsicum annuum L.). The capsaicin receptor is highly expressed in the unmyelinated type C nerve fibers originating from small diameter sensory neurons in dorsal root ganglia and cranial nerve ganglia correspondents. Capsaicin and related vanilloids have a variety of effects on primary sensory neurons function, from sensory neuron excitation characterized by local burning sensation and neurogenic inflammation, followed by conduction blockage accompanied by reversible ultrastructural changes of peripheral nociceptive endings (desensitization), going as far as irreversible degenerative changes (neurotoxicity). The main role in capsaicin-induced neurogenic inflammation relies on the capsaicin sensitive, small diameter primary sensory neurons, therefore its evaluation could be used as a diagnostic instrument in functional alterations of cutaneous sensory nerve fibers. Moreover, capsaicin-induced desensitization and neurotoxicity explain the analgesic/anti-nociceptive and anti-inflammatory effects of topical capsaicin and its potential use in the management of painful and inflammatory conditions. In this study, we describe the effects of capsaicin on neurogenic inflammation and nociception, as well as its potential diagnostic value and therapeutic impact in various conditions involving impairment of sensory nerve fibers.

Capsaicin: Effects on the Pathogenesis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent cancers, and to date, there have been very few drugs available that can improve survival, the most well-known being sorafenib. The pathogenesis of HCC is complex, involving multiple processes including abnormal cell and tissue regeneration, angiogenesis, genomic instability, cellular proliferation, and signaling pathway alterations. Capsaicin is a substance that holds increasingly high interest and is studied as a therapeutic option in a wide array of diseases. Several studies have investigated capsaicin roles in various stages of HCC oncogenesis. This paper aims to thoroughly detail the available information on the individual effects of capsaicin on the cellular mechanisms and pathways involved in HCC development, as well as investigate their possible cooperation and interferences. The synergistic antitumor effects of capsaicin and sorafenib are also addressed.

Ethanol-induced symptoms in patients receiving gemcitabine diluted from a concentrate for solution for infusion containing ethanol

Purpose Ethanol as an excipient is used to enhance the solubility of gemcitabine, but, sometimes, the dose of ethanol a patient may be given is much higher than the dose considered to be toxic. We aimed to assess ethanol-related symptoms and signs in patients receiving two formulations of gemcitabine, with and without ethanol. Methods A randomized double blind cross-over study was conducted. All patients being treated with gemcitabine received two consecutive doses of the drug, one diluted from a concentrate for solution for infusion (CSI) containing ethanol and the other from a lyophilized powder, without ethanol, which was used as control group. After each administration, patients were surveyed in order to assess the appearance of any alcohol consumption symptoms (dizziness, difficulty speaking, unsteady walking, impaired balance, mood swings and slower reactions). Widmark formula and the amount of alcohol measured on the breath (breathalyzer) were used to estimate blood alcohol concentration. Results Twenty-four patients received both formulations and were included in the analysis. Mean administered ethanol dose when prepared from CSI was 15.81 ± 2.25 g (mean ± SD). When using CSI gemcitabine, estimated blood ethanol concentration was 0.033 g/dl according to Widmark formula and 0.02 g/dl according to breathalyzer results. Although overall incidence of symptoms was higher in the study group, the difference was not statistically significant (33% vs. 25%; p = 0.53). Conclusions These findings prove there is no difference in the onset of ethanol related symptoms when using CSI instead of lyophilized powder on the reconstitution of gemcitabine.

Analgesic Effects of Alcohol: A Systematic Review and Meta-Analysis of Controlled Experimental Studies in Healthy Participants

Despite the long-standing belief in the analgesic properties of alcohol, experimental studies have produced mixed results. This meta-analysis aimed to clarify whether alcohol produces a decrease in experimentally-induced pain and to determine the magnitude of any such effect. PubMed, PsycINFO, and Embase databases were searched from inception until April 21, 2016 for controlled studies examining the effect of quantified dosages of alcohol on pain response to noxious stimulation. Eighteen studies involving 404 participants were identified providing alcohol versus no-alcohol comparisons for 13 tests of pain threshold (n = 212) and 9 tests of pain intensity ratings (n = 192). Random effects meta-analysis of standardized mean difference (SMD) provided robust support for analgesic effects of alcohol. A mean blood alcohol content (BAC) of approximately .08% (3-4 standard drinks) produced a small elevation of pain threshold (SMD [95% CI] = .35 [.17-.54], P = .002), and a moderate to large reduction in pain intensity ratings (SMD [95% CI] = .64 [.37-.91], P < .0001), or equivalently, a mean reduction of 1.25 points on a 0- to 10-point pain rating scale. Furthermore, increasing BAC resulted in increasing analgesia, with each .02% BAC increment producing an increase of SMD = .11 for pain threshold and SMD = .20 for reduced pain intensity. Some evidence of publication bias emerged, but statistical correction methods suggested minimal impact on effect size. Taken together, findings suggest that alcohol is an effective analgesic that delivers clinically-relevant reductions in ratings of pain intensity, which could explain alcohol misuse in those with persistent pain despite its potential consequences for long-term health. Further research is needed to corroborate these findings for clinical pain states.

PERSPECTIVE

This meta-analysis provides robust evidence for the analgesic properties of alcohol, which could potentially contribute to alcohol misuse in pain patients. Strongest analgesia occurs for alcohol levels exceeding World Health Organization guidelines for low-risk drinking and suggests raising awareness of alternative, less harmful pain interventions to vulnerable patients may be beneficial.