The dynamic interaction between pain and opioid misuse

The relationship of pain intensity and opioid craving with delayed methadone dose: A preliminary study of individuals with opioid use disorder

AIMS

Despite a strong theoretical link between opioid craving and pain, little is known about the temporal relationship between pain and craving and the acute experience of pain in the context of methadone treatment. Using a cross-over design, the current study evaluated the time course of pain and craving and objective experience of pain as a function of the last methadone dose.

METHODS

Participants (n = 20) presented for the study in the morning and either received methadone dose as scheduled or delayed dose until the afternoon. During the 4-h study visit, participants completed a series of tasks, including repeated assessment of pain and craving at 0, +40, +70, +130, +160 and +240 min and a cold pressor test (CPT) at +15 and +220 min.

RESULTS

Separate mixed model results demonstrated no effect of dosing condition on craving; however, there was a significant dosing condition by time interaction (F(5,209) = 3.38, P = .006) such that pain increased over time in the delayed methadone condition but decreased in time in the scheduled methadone condition. A mixed model predicting self-reported pain revealed a three-way interaction between dosing condition, craving and time (F(5,197) = 2.39, P = .039) explained by a positive association between craving and pain at each time point (except 240 min) in delayed condition (P-range = .004-.0001). A separate mixed model on CPT data indicated a significant condition by time interaction such that pain threshold decreased in the delayed, but not scheduled, condition (F(1,57) = 4.01, P = .050).

CONCLUSIONS

These preliminary findings highlight the potential for increased risks after even a short delay in receiving a methadone dose.

Selective neural inhibition via photobiomodulation alleviates behavioral hypersensitivity associated with small sensory fiber activation

OBJECTIVE

Photobiomodulation at higher irradiances has great potential as a pain-alleviating method that selectively inhibits small diameter nerve fibers and corresponding sensory experiences, such as nociception and heat sensation. The longevity and magnitude of these effects as a function of laser irradiation parameters at the nerve was explored.

METHODS

In a rodent chronic pain model (spared nerve injury-SNI), light was applied directly at the sural nerve with four delivery schemes: two irradiance levels (7.64 and 2.55 W/cm2 ) for two durations each, corresponding to either 4.8 or 14.4 J total energy, and the effect on sensory hypersensitivities was evaluated.

RESULTS

At emitter irradiances of 7.64 W/cm2 (for 240 s), 2.55 W/cm2 (for 720 s), and 7.64 W/cm2 (for 80 s) the heat hypersensitivity was relieved the day following photobiomodulation (PBM) treatment by 37 ± 8.1% (statistically significant, p < 0.001), 26% ± 6% (p = 0.072), and 28 ± 6.1% (statistically significant, p = 0.032), respectively, and all three treatments reduced the hypersensitivity over the course of the experiment (13 days) at a statistically significant level (mixed-design analysis of variance, p < 0.05). The increases in tissue temperature (5.3 ± 1.0 and 1.3 ± 0.4°C from 33.3°C for the higher and lower power densities, respectively) at the neural target were well below those typically associated with permanent action potential disruption.

CONCLUSIONS

The data from this study support the use of direct PBM on nerves of interest to reduce sensitivities associated with small-diameter fiber activity.

A Randomized Comparison Between Interscalene and Combined Interscalene-Suprascapular Blocks for Arthroscopic Shoulder Surgery: A Prospective Clinical Study

Background

To compare the analgesic effect of ISB with a combination of ISB-SSNB and patients who were given opioids with PCA without block in adult patients undergoing shoulder surgery, as measured by opioid consumption and pain intensity in the first 24 hours postoperatively.

Methods

Ninety patients who underwent shoulder surgery were randomly divided into three groups. Group I in which ISB was performed and patient-controlled analgesia (PCA) was inserted, Group II with; ISB and SSNB combined, and PCA was inserted, and Group III where; only PCA was used. Visual analog scale (VAS) pain scores at the second, fourth, sixth, 12th, and 24th hours, morphine consumption, additional analgesic requirement, and patient satisfaction were evaluated.

Results

Compared with Group III, the VAS pain score was significantly lower in Group I and Group II at 2, 4, 6, 12, and 24 hours postoperatively. In Group I, the VAS score at rest at the 6th hour was found to be higher than in Group II. The 24-hour total morphine consumption was higher in the control group than in Group I and Group II. The satisfaction score of the control group was lower than Group I and Group II.

Conclusion

The combined application of ISB and SSNB block is beneficial in shoulder surgery to provide both intraoperative and postoperative analgesia and opioid consumption.

Level of Evidence

Level I; Randomized Controlled Trial; Treatment Study.

Toward a Psychological Model of Chemical Coping with Opioids in Cancer Care

LEARNING OBJECTIVES AFTER PARTICIPATING IN THIS CME ACTIVITY, THE PSYCHIATRIST SHOULD BE BETTER ABLE TO

• Outline the risk factors involved with opioid accessibility in patients receiving treatment for cancer.• Identify factors to address in order to mitigate risk for opioid misuse during cancer care.

ABSTRACT

Most patients with advanced cancer receive treatment for related pain. Opioid accessibility, however, is a risk factor for misuse, which can present care challenges and quality-of-life concerns. There is a lack of consistent universal screening prior to initiation of opioid prescribing. One crucial issue in treating this population is adequately identifying and mitigating risk factors driving opioid misuse. Drawing on theory and research from addiction science, psychology, palliative care, and oncology, the presented conceptual framework suggests that risk factors for opioid misuse during cancer care can be stratified into historical, current, malleable, and unmalleable factors. The framework identifies necessary factors to address in order to mitigate risk for opioid misuse during cancer care, and offers key directions for future research.

Substance use disorders, physical health and recovery capital: Examining the experiences of clients and the alcohol and other drug workforce

INTRODUCTION

Challenges associated with the integration of physical health within alcohol and other drug (AOD) treatment services persist. The construct of recovery capital has gained currency within the sector, however, its potential in understanding the integration of physical health within AOD treatment has not been examined. This study explores the role of physical health in the process of recovery, examining the potential of 'recovery capital' frameworks to enhance integrated care.

METHODS

Interviews were conducted with residential and outpatient AOD services across New South Wales, Australia. Qualitative data was collected from clients (n = 20) and staff (n = 13) and transcribed. Data were systematically coded and analysed using the iterative categorisation method.

RESULTS

Unmanaged physical health issues compromised recovery, particularly when associated with hopelessness and pain. Improved physical health ameliorated sources of negative recovery capital such as boredom, social isolation and mental health symptoms. When addressed during treatment, physical health facilitated recovery capital resources through knowledge and skill acquisition, increased autonomy, enjoyment and immersive experience. Benefits extended to domains of 'social capital' (social connection) and 'cultural capital' (physical appearance).

DISCUSSION AND CONCLUSIONS

Physical health offers variegated pathways for building recovery capital. Findings support calls for a more assertive approach to addressing physical health when AOD treatment occurs outside of primary care settings. Future research should examine the potential of recovery capital as a heuristic for optimising care of physical health issues and health-related behaviour within AOD treatment services.

The inhibition of enkephalin catabolism by dual enkephalinase inhibitor: A novel possible therapeutic approach for opioid use disorders

Despite the increasing impact of opioid use disorders on society, there is a disturbing lack of effective medications for their clinical management. An interesting innovative strategy to treat these disorders consists in the protection of endogenous opioid peptides to activate opioid receptors, avoiding the classical opioid-like side effects. Dual enkephalinase inhibitors (DENKIs) physiologically activate the endogenous opioid system by inhibiting the enzymes responsible for the breakdown of enkephalins, protecting endogenous enkephalins and increasing their half-lives and physiological actions. The activation of opioid receptors by the increased enkephalin levels, and their well-demonstrated safety, suggests that DENKIs could represent a novel analgesic therapy and a possible effective treatment for acute opioid withdrawal, as well as a promising alternative to opioid substitution therapy minimizing side effects. This new pharmacological class of compounds could bring effective and safe medications avoiding the major limitations of exogenous opioids, representing a novel approach to overcome the problem of opioid use disorders. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

High-CBD Cannabis Vapor Attenuates Opioid Reward and Partially Modulates Nociception in Female Rats

Chronic pain patients report analgesic effects when using cannabidiol (CBD), a phytocannabinoid found in whole-plant cannabis extract (WPE). Several studies suggest that cannabis-derived products may serve as an analgesic adjunct or alternative to opioids, and importantly, CBD may also attenuate the abuse potential of opioids. Vaping is a popular route of administration among people who use cannabis, however both the therapeutic and hazardous effects of vaping are poorly characterized. Despite the fact that chronic pain is more prevalent in women, the ability of inhaled high-CBD WPE to relieve pain and reduce opioid reward has not been studied in females. Here, we present a comprehensive analysis of high-CBD WPE vapor inhalation in female rats. We found that WPE was modestly efficacious in reversing neuropathy-induced cold allodynia in rats with spared nerve injury (SNI). Chronic exposure to WPE did not affect lung cytoarchitecture or estrous cycle, and it did not induce cognitive impairment, social withdrawal or anxiolytic effects. WPE inhalation prevented morphine-induced conditioned place preference and reinstatement. Similarly, WPE exposure reduced fentanyl self-administration in rats with and without neuropathic pain. We also found that WPE vapor lacks of reinforcing effects compared to the standard excipient used in most vapor administration research. Combined, these results suggest that although high-CBD vapor has modest analgesic effects, it has a robust safety profile, no abuse potential, and it significantly reduces opioid reward in females. Clinical studies examining high-CBD WPE as an adjunct treatment during opioid use disorder are highly warranted.

Kyphoplasty for Elderly Patients With Vertebral Compression Fractures-Do We Save Lives? Mortality Rates Analysis Comparison in a Long-Term Follow-Up Cohort

STUDY DESIGN

Retrospective cohort.

OBJECTIVES

We aimed to compare a large cohort of patients with vertebral compression fractures (VCF) treated in 2 centers using different protocols (conservative vs BKP) and compare mortality rates on a long-term follow-up.

METHODS

Retrospective cohort held in 2 medical centers (W and AH). All patients admitted with VCF from November 2008 to January 2015 were enrolled in the study. Exclusion criteria were patients admitted with non-osteoporotic pathological fractures (such as metastatic or MM).

RESULTS

Our study included 208 patients treated for VCF, 127 were treated with BKP (88 females, 69.3%) and 81 were treated conservatively (59 females, 72.8%). Patients from Centre W were older and frailer compared to the patients from AH center (Average age 75.12 ± 11.16 vs 69.13 ± 9.61 years and Frailty score of 0.16 ± 0.1 vs 0.12 ± 0.1 respectively, T-test, p < 0.01 for both). Hazard ratios (HR) for age, female gender and frailty were significant for increased mortality, frailty had the highest HR of 182.42 (CI 29.05-1145.33, p < 0.01). Multivariate Cox model was fitted and after accounting for Gender, Age and Frailty, no significant difference was found between the 2 medical centers mortality rates (p = 0.59), thus no difference in mortality rates between BKP and conservative treatment in our study.

CONCLUSION

long-term follow-up following BKP treatment for VCF did not show a reduced mortality rate compared to conservative treatment after accounting for frailty, age and gender. Frailty was the most important factor in predicting mortality. Further RCTs are needed to compare the quality of life differences between the 2 treatment strategies.

The Covid 19 Pandemic Effect on the Epidemiology of Thoracolumbar Fractures Presenting to the Emergency Department in Patients Above 65 years Old

Introduction

Studies investigating the Covid-19 Pandemic’s orthopedic aspects are accumulating, including reports on a 10-33% decrease in hip fracture incidence alongside shorter times to surgery. Osteoporotic vertebral compression fractures (VCF) have not yet been discussed. This study evaluated the effect of the Covid-19 pandemic’s first wave on VCF in the elderly.

Method

A retrospective cohort of elderly patients diagnosed with VCF between 2018-19 (Pre-Covid-19 pandemic) to 2020.

Results

The cohort included 172 patients above 65 years with VCF during 2018-2020. Patients’ age and gender were similar between the two study groups. We found a higher proportion of high-energy VCF during 2020 (10.5% vs 6.7%). Incidence of recurrent fractures was 7.5 times higher during 2020 (5.3% vs .7%, P =.06), and significantly higher rates of Ankylosing Spondylitis or Diffuse Idiopathic Skeletal Hyperostosis in 2020 (7.9% vs 1.5%, P=.04). VCF ED admission rates were similar, with 60% treated conservatively. Admitted patients underwent more surgeries in 2020 (66.7% vs 60%, P =.71) and a tendency towards Precoutaneus Balloon Kyphoplasty (BKP) + fixation compared with BKP alone (15.8% in 2020 vs 7.5% in 2018-19, P =.29). RR for BKP + fixation vs BKP alone was 1.95, suggesting higher odds for a more complex surgery during the Covid-19 pandemic. The complication rate was significantly higher during 2020 (18.4% vs 3.7%, P <.001). Admission length was slightly longer during 2020 (12.2 days vs 9.9 days, P = .27), and time to surgery was marginally longer, 6.25 vs 5.3 days (P = .55). Many patients chose home over institutional rehabilitation during the Covid-19 pandemic (72.2% vs 58.8%).

Conclusion

The Covid-19 pandemic did not alter VCF incidence, but patients’ characteristics changed, affecting admissions, institutional rehabilitation, and a tendency towards complex surgery rather than BKP alone. It is still unclear if Covid-19 will remain an issue in the upcoming years, but its impact and lessons are still worthwhile.

Operant Self-medication for Assessment of Spontaneous Pain Relief and Drug Abuse Liability in Mouse Models of Chronic Pain

The search for safe and efficient chronic pain treatments is dampened by the lack of reliable models that faithfully reproduce current pharmacological treatments for chronic spontaneous pain in humans. Preclinical models often assess the antinociceptive efficacy of non-contingent pharmacological treatments evaluated in the short-term. Here, we provide a protocol of contingent operant self-medication in mice, which allows the estimation of spontaneous pain relief and drug abuse liability in models of persistent pain. This paradigm requires preliminary habituation and animal handling, followed by training of mice in operant conditioning boxes, to allow subsequent analgesic drug self-administration. After the initial acquisition of food-maintained operant behavior, a chronic pain sensitization is induced. Posterior intravenous jugular catheterization and coupling of operant conditioning boxes to perfusion pumps allow quantification of operant responding for intravenous drug self-administration. All mice show an initial operant drug self-administration behavior associated with the previous food-maintained operant training. This initial operant responding is extinguished after administration of ineffective treatments, but continues when the compounds have analgesic efficacy or intrinsic reinforcing properties. The identification of a significant drug self-administration selectively expressed in mice exposed to the chronic pain condition is indicative of analgesic drug effects, whereas persistent self-administration in control mice is indicative of abuse liability. The present protocol provides the behavioral and surgical procedures needed to assess spontaneous pain relief and potential for abuse of pharmacological treatments, through contingent analgesic self-medication in mice. Graphic abstract: Experimental design. Animals are subjected to a 5-day food self-administration protocol with a fixed ratio of reinforcement of 1 (FR1, 1 interaction with the active nose-poke causes the release of 1 reinforcer/infusion), to acquire the operant behavior. After this training, mice are subjected to the chronic pain or sham procedure, and four days later an intravenous (i.v.) catheterization is performed, to allow self-administration with the selected compound or its vehicle. Three days after the catheterization, animals start the drug/vehicle self-administration protocol at FR1. The patency of the catheter is evaluated with the thiopental test after the last self-administration session. Adapted from Bura et al. (2018).

Synthesis, biological, and structural explorations of a series of μ-opioid receptor (MOR) agonists with high G protein signaling bias

Biased agonism refers to the ability of compounds to drive preferred signaling pathways and avoid adverse signaling pathways in a ligand-dependent manner for some G-protein-coupled receptors. It is thought that the separation of therapeutic efficacy (e.g., analgesia) from adverse effects (e.g., respiration depression) can be achieved through the design of biased MOR agonists and one example is the recently approved MOR biased agonist oliceridine (TRV130). However, oliceridine only demonstrates modest beneficial effects as compared to other opioids in terms of therapeutic/adverse effect balance. One possibility attributable to the modest success of oliceridine is its limited bias, and as such developing MOR ligands with a more biased agonism profile could in theory further improve the beneficial effects of the ligands. Here, we rationally designed and synthesized a series of derivatives as potent highly biased MOR agonists (19a-v) through the modification and structure-activity relationship study of TRV130. This novel synthetic molecule, LPM3480392 (19m), demonstrated improved in vitro biased agonism (EC₅₀ = 0.35 nM, Emax = 91.4%) with no measured β-arrestin recruitment (EC₅₀ > 30000 nM, Emax = 1.6%), good brain penetration (B/P ratio = 4.61, 0.25 h post-IV dosing 2.0 mg/kg), a favorable pharmacokinetic profile (distribution volume = 10766 mL/kg, t_1/2 = 1.9 h) and produced potent antinociceptive effect with reduced respiratory suppression (sO₂(%) = 92.17, 0.32 mg/kg, SC) as compared to TRV130. LPM3480392 has completed preclinical studies and is currently under clinical development (CTR20210370) as an analgesic for the treatment of moderate to severe pain.

Mice with high FGF21 serum levels had a reduced preference for morphine and an attenuated development of acute antinociceptive tolerance and physical dependence

Because of increased opioid misuse, there is a need to identify new targets for minimizing opioid tolerance, and physical and psychological dependence. Previous studies showed that fibroblast growth factor 21 (FGF21) decreased alcohol and sweet preference in mice. In this study, FGF21-transgenic (FGF21-Tg) mice, expressing high FGF21 serum levels, and wildtype (WT) C57BL/6J littermates were treated with morphine and saline to determine if differences exist in their physiological and behavioral responses to opioids. FGF21-Tg mice displayed reduced preference for morphine in the conditioned place preference assay compared to WT littermates. Similarly, FGF21-Tg mice had an attenuation of the magnitude and rate of acute morphine antinociceptive tolerance development, and acute and chronic morphine physical dependence, but exhibited no change in chronic morphine antinociceptive tolerance. The ED50 values for morphine-induced antinociception in the 55 °C hot plate and the 55 °C warm-water tail withdrawal assays were similar in both strains of mice. Likewise, FGF21-Tg and WT littermates had comparable responses to morphine-induced respiratory depression. Overall, FGF21-Tg mice had a decrease in the development of acute analgesic tolerance, and the development of physical dependence, and morphine preference. FGF21 and its receptor have therapeutic potential for reducing opioid withdrawal symptoms and craving, and augmenting opioid therapeutics for acute pain patients to minimize tolerance development.

Telemedicine and current clinical practice trends in the COVID-19 pandemic

Telemedicine is the medical practice of caring for and treating patients remotely. With the spread of the coronavirus disease-2019 (COVID-19) pandemic, telemedicine has become increasingly prevalent. Although telemedicine was already in practice before the 2020 pandemic, the internet, smartphones, computers, and video-conferencing tools have made telemedicine easily accessible and available to almost everyone. However, there are also new challenges that health care providers may not be prepared for, including treating and diagnosing patients without physical contact. Physician adoption also depends upon reimbursement and education to improve the telemedicine visits. We review current trends involving telemedicine, how pandemics such as COVID-19 affect the remote treatment of patients, and key concepts important to healthcare providers who practice telemedicine.

Is Buprenorphine Effective for Chronic Pain? A Systematic Review and Meta-analysis

OBJECTIVE

The objective was to perform a systematic review and meta-analysis of the literature on the effects of buprenorphine on chronic pain outcomes (i.e., patient-reported pain intensity) in patients with and without opioid use disorder (OUD).

DESIGN

Ovid/Medline, PubMed, Embase, and the Cochrane Library were searched for studies that explored the effectiveness (in reducing pain) of buprenorphine treatment for chronic pain patients with and without a history of OUD. Randomized controlled trials and observational studies were included in the review.

METHODS

Two separate searches were conducted to identify buprenorphine trials that included chronic pain patients either with or without OUD. Five studies used validated pain report measures and included a chronic pain population with OUD. Nine studies used validated report measures and included chronic pain patients without OUD. Meta-analysis was performed using the R, version 3.2.2, Metafor package, version 1.9-7.

RESULTS

The meta-analysis revealed that buprenorphine has a beneficial effect on pain intensity overall, with a small mean effect size in patients with comorbid chronic pain and OUD and a moderate- to large-sized effect in chronic pain patients without OUD.

CONCLUSIONS

Our results indicate that buprenorphine is modestly beneficial in reducing pain intensity in patients without OUD. Although informative, these findings should be carefully interpreted due to the small amount of data available and the variation in study designs.

Expanding access to nurse-managed medication for opioid use disorder

BACKGROUND

Advanced practice registered nurses (APRNs) are increasingly caring for individuals with opioid use disorder. Advances have been made to increase APRN education, outreach, and prescribing privileges, but as demand for medication for opioid use disorder (MOUD) grows, evidence suggests that policy and care barriers inhibit the ability of APRNs to support MOUD.

PURPOSE

This paper highlights the significant challenges of expanding access to buprenorphine prescribing by APRNs.

RESULTS

Barriers and recommendations were derived from the culmination of literature review, expert consensus discussions among a diverse stakeholder panel including patient representatives, and feedback from community webinars with care providers.

DISCUSSION

We provide an overview of existing care barriers, promising practices, and proposed recommendations to enhance the care of individuals and communities with opioid use disorder.

Pain Anxiety as a Mechanism Linking Pain Severity and Opioid Misuse and Disability Among Individuals With Chronic Pain

OBJECTIVE

Chronic pain affects a significant number of individuals in the United States and is associated with several negative health-related outcomes, including possibility of opioid misuse and disability. The identification of factors associated with both opioid misuse and disability is of critical public health importance, and significant research suggests that pain severity has been shown to be associated with both. Pain-related anxiety has been uniquely associated with both opioid misuse and disability, yet little research has examined pain-related anxiety as a potential mechanism linking pain severity with opioid misuse and disability.

METHOD

Therefore, the current study examined whether pain-related anxiety explains, in part, the relationship between pain severity, opioid misuse, and disability among 396 adults with chronic pain (55.8% female, Mage 36.61, SD 11.40).

RESULTS

Cross-sectional analyses indicated that pain-related anxiety significantly mediated the relationship between pain severity, opioid misuse outcomes, and psychosocial disability, but not physical disability.

CONCLUSIONS

These results build upon the literature indicating the importance of pain-related anxiety in those with chronic pain by suggesting this construct may account, in part, for the relation of pain intensity to opioid misuse and psychosocial disability. Future research should longitudinally examine these associations.

Identifying individuals with opioid use disorder: Validity of International Classification of Diseases diagnostic codes for opioid use, dependence and abuse

BACKGROUND

Policy evaluations and health system interventions often utilize International Classification of Diseases (ICD) codes of opioid use, dependence, and abuse to identify individuals with opioid use disorder (OUD) and assess receipt of evidence-based treatments. However, ICD codes may not map directly onto the Diagnostic and Statistical Manual of Mental Disorder (DSM-5) OUD criteria. This study investigates the positive predictive value of ICD codes in identifying patients with OUD.

METHODS

We conducted a clinical chart review on a national sample of 520 Veterans assigned ICD-9 or ICD-10 codes for opioid use, dependence, or abuse from 2012 to 2017. We extracted evidence of DSM-5 OUD criteria and opioid misuse from clinical documentation in the month preceding and three months following initial ICD code listing, and categorized patients into: 1) high likelihood of OUD, 2) limited aberrant opioid use, 3) prescribed opioid use without evidence of aberrant use, and 4) insufficient information. Positive predictive value was calculated as the percentage of individuals with these ICD codes meeting high likelihood of OUD criteria upon chart review.

RESULTS

Only 57.7 % of patients were categorized as high likelihood of OUD; 16.5 % were categorized as limited aberrant opioid use, 18.9 % prescribed opioid use without evidence of aberrant use, and 6.9 % insufficient information.

CONCLUSIONS

Patients assigned ICD codes for opioid use, dependence, or abuse often lack documentation of meeting OUD criteria. Many receive long-term opioid therapy for chronic pain without evidence of misuse. Robust methods of identifying individuals with OUD are crucial to improving access to clinically appropriate treatment.

Analgesic Opioid Misuse and Opioid Use Disorder among Patients with Chronic Non-Cancer Pain and Prescribed Opioids in a Pain Centre in France

(1) Background: Chronic non-cancer pain (CNCP) remains a public health challenge around the world. Opioids (PO) have been increasingly used in the treatment of CNCP in the last 20 years. This study aimed to assess the prevalence of opioid misuse and prescribed-opioid use disorder (p-OUD) among patients with CNCP in a pain centre in France, and to analyse risk factors for moderate or severe p-OUD. (2) Method: A cross-sectional study was conducted, including patients consulting for pain management in the pain centre of Brest University Hospital. A self-questionnaire was administered (sociodemographic data, medical data, PO misuse, and p-OUD according the Diagnostic and Statistical Manual of Mental Disorders 5 (DSM 5) criteria). Descriptive, univariate, and multivariate analyses were conducted, together with a principal component analysis, in order to identify factors associated with p-OUD. (3) Results: In total, 115 patients were included, the majority of whom were women, with a mean age of 52 years old [18–82]; 64.3% (n = 74) had a current prescription for opioid analgesics (weak or strong). In this group, 56.7% (n = 42) had no or only mild p-OUD and 43.3% (n = 32) had current moderate or severe p-OUD. Patients with moderate or severe p-OUD were more likely to have a current antidepressant prescription, to have had psychotherapy, to currently use strong opioids and oxycodone, and to report taking more frequent doses than prescribed and feeling dependent. (4) Conclusions: We showed that the prevalence of current moderate/severe p-OUD concerned 43.3% of the patients with a CNCP seeking treatment in a pain centre. According to these results, several measures are relevant in managing p-OUD among patients with CNCP.

Synthetic Studies of Neoclerodane Diterpenes from Salvia divinorum: Design, Synthesis, and Evaluation of Analogues with Improved Potency and G-protein Activation Bias at the μ-Opioid Receptor

Previous structure-activity relationship (SAR) studies identified the first centrally acting, non-nitrogenous μ-opioid receptor (MOR) agonist, kurkinorin (1), derived from salvinorin A. In an effort to further probe the physiological effects induced upon activation of MORs with this nonmorphine scaffold, a variety of analogues were synthesized and evaluated in vitro for their ability to activate G-proteins and recruit β-arrestin-2 upon MOR activation. Through these studies, compounds that are potent agonists at MORs and either biased toward β-arrestin-2 recruitment or biased toward G-protein activation have been identified. One such compound, 25, has potent activity and selectivity at the MOR over KOR with bias for G-protein activation. Impressively, 25 is over 100× more potent than morphine and over 5× more potent than fentanyl in vitro and elicits antinociception with limited tolerance development in vivo. This is especially significant given that 25 lacks a basic nitrogen and other ionizable groups present in other opioid ligand classes.

CE: Opioid Use Disorder: Pathophysiology, Assessment, and Effective Interventions

Opioid use disorder (OUD) is a chronic, relapsing disease. Genetic variability, dysregulated stress system response, and history of opioid experimentation or escalating exposure all contribute to the likelihood of developing OUD, which produces complex brain changes that make it difficult to stop opioid use. Understanding the neurobiology of OUD helps nurses anticipate the behaviors of patients with OUD and approach them with empathy. Here, the authors discuss the pathophysiology of OUD, available screening tools, medical treatments, and behavioral interventions that have demonstrated efficacy in reducing substance use.

Does Rebound Pain after Peripheral Nerve Block for Orthopedic Surgery Impact Postoperative Analgesia and Opioid Consumption? A Narrative Review

Regional anesthesia has been considered a great tool for maximizing post-operative pain control while minimizing opioid consumption. Post-operative rebound pain, characterized by hyperalgesia after the peripheral nerve block, can however diminish or negate the overall benefit of this modality due to a counter-productive increase in opioid consumption once the block wears off. We reviewed published literature describing pathophysiology and occurrence of rebound pain after peripheral nerve blocks in patients undergoing orthopedic procedures. A search of relevant keywords was performed using PubMed, EMBASE, and Web of Science. Twenty-eight articles (n = 28) were included in our review. Perioperative considerations for peripheral nerve blocks and other alternatives used for postoperative pain management in patients undergoing orthopedic surgeries were discussed. Multimodal strategies including preemptive analgesia before the block wears off, intra-articular or intravenous anti-inflammatory medications, and use of adjuvants in nerve block solutions may reduce the burden of rebound pain. Additionally, patient education regarding the possibility of rebound pain is paramount to ensure appropriate use of prescribed pre-emptive analgesics and establish appropriate expectations of minimized opioid requirements. Understanding the impact of rebound pain and strategies to prevent it is integral to effective utilization of regional anesthesia to reduce negative consequences associated with long-term opioid consumption.

Screening tools for detecting problematic opioid use and potential application to community pharmacy practice: a review

Problematic opioid use, constituted by a myriad of conditions ranging from misuse to use disorders, has continued to receive an increasing amount of attention in recent years resulting from the high use of opioids in the United States coinciding with morbidity and mortality. Deaths from drug overdoses increased by over 11% between 2014 and 2015, which supports the need for identification of problematic opioid use in additional health care settings. One of these settings is community pharmacy. The community pharmacy is a unique health service setting to identify and potentially intervene with patients at risk of or exhibit problematic opioid use. Problematic opioid use can be identified using one of the various screening tools in conjunction with evaluating prescription drug monitoring systems. A total of 12 tools were identified that could be employed in community pharmacy settings for identifying problematic opioid use. This review highlights these tools and strategies for use that can be utilized in the community pharmacy, which should be adapted to individual pharmacy settings and local needs. Future research should assess pharmacy personnel's knowledge and perceptions of problematic opioid use and associated screening tools and interventions, which tools can be most effectively used in a community pharmacy, workflow needs to implement problematic opioid use screenings, and the impact of pharmacist engagement in problematic opioid use screening on patient clinical outcomes.

Interactions between pain states and opioid reward assessed with intracranial self-stimulation in rats

Opioids are an essential component of current clinical treatments for pain, but they also produce side effects that include abuse liability. Recent media attention surrounding the use of opioids in the United States has elevated the discussion of their benefits and drawbacks to one of national concern, leading to increased scrutiny of prescribing practices. Regulatory agencies have responded by recommending stricter limits on the amount and duration of opioid prescriptions for pain treatment; however, the relationship between pain states and the abuse-related effects of opioids is still not completely understood. Intracranial self-stimulation (ICSS) is one preclinical procedure that can be used to study the abuse-related effects of opioids in naïve subjects over the course of initial opioid exposure and in the context of inferred pain states. The goal of this review is to provide a summary of evidence from our laboratory using ICSS to study the modulation of opioid reward by pain states and examine these results in the context of related studies from other groups. This article is part of the Special Issue entitled 'New Vistas in Opioid Pharmacology'.

Determinants of opioid abuse potential: Insights using intracranial self-stimulation

Intracranial self-stimulation (ICSS) is one procedure that can be used for preclinical abuse potential assessment. In ICSS procedures, subjects with microelectrodes implanted into a brain-reward region are trained to press an operant response lever for pulses of electrical brain stimulation, and drugs are evaluated for their effectiveness to increase or "facilitate" ICSS responding (an abuse-related effect) or to depress ICSS responding (an abuse-limiting effect). ICSS has been used for decades to evaluate determinants of opioid abuse potential, and this article reviews pharmacological and biological determinants of opioid abuse potential as revealed by ICSS studies in rodents. One of the most important observations from ICSS studies is that abused mu opioid receptor (MOR) agonists like morphine often fail to produce abuse-related ICSS facilitation in opioid-naïve subjects, but several days of repeated opioid exposure is sufficient for opioid-induced facilitation to emerge. Future studies with ICSS could help (a) to clarify mechanisms that increase MOR agonist abuse potential during early opioid exposure or during chronic exposure leading to dependence, (b) to evaluate novel opioids either developed as candidate analgesics with reduced abuse potential or identified as designer opioids being synthesized and distributed for illicit use, and (c) to test candidate pharmacotherapies for treatment of opioid abuse in non-dependent and dependent subjects.

Management of Challenging Pharmacologic Issues in Chronic Pain and Substance Abuse Disorders

Drug abuse and addiction are persistent problems in the United States and around the world. This is an ongoing issue for health care providers, as substance abuse is seen in 25% to 40% of patients admitted to hospitals for general treatment. Many patients with substance use disorders have a higher risk for adverse events; however, only a small percentage will volunteer information regarding prior substance use. This article discusses the present opioid crisis, mechanisms behind chronic pain and substance abuse, current clinical findings, treatment therapies, and abuse deterrents.

Emerging areas of opioid pharmacology

This themed section of the British Journal of Pharmacology stems from an International Narcotics Research Conference (INRC) meeting held in July 2016 at The Assembly Rooms in Bath, UK.

LINKED ARTICLES

This article is part of a themed section on Emerging Areas of Opioid Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.14/issuetoc.

A Review of the Opioid Epidemic: What Do We Do About It?

The opioid epidemic, with its noticeable increase in opioid prescriptions and related misuse, abuse and resultant deaths in the previous 12 years, is a particularly North American phenomenon. Europe, and particularly low- and middle-income countries, appear to be less influenced by this problem. There is undisputable value in using opioids not only in the treatment of acute pain, but in cancer pain as well. However, opioids are progressively being prescribed more and more for chronic non-cancer pain, despite inadequate data on their efficacy. In this paper, we describe the current prevalence of opioid misuse in a number of countries and the rationale for the commencement of opioid therapy. The safe initiation and monitoring of opioid therapy as well as the need for concurrent use of interdisciplinary multimodal therapy is discussed. The possible consequences of long-term use and predictors of high opioid use and overdose are presented. In particular, the management of opioid use disorders and the prevention of opioid abuse and dependence in the young, the old and the pregnant are discussed. Measures to prevent overprescribing and to alleviate risk are described, including the tapering of opioids and the use of opioid deterrents. Finally, the paper looks at the future development of pioneering medications and technologies to potentially treat abuse. In those parts of the world with an opioid epidemic, coroners and medical examiners, private and public health agencies, and agencies that enforce the law need to cooperate in an effort to slow down and reverse the indiscriminate use of prescribing opioids in the long-term for chronic non-cancer pain. Ongoing research is needed to create ways to minimise risks of opioid use, and to provide evidence for effective strategies for treating chronic pain.

Patients With Major Depressive Disorder Experience Increased Perception of Pain and Opioid Consumption Following Total Joint Arthroplasty

BACKGROUND

Pain in the immediate postoperative period following total joint arthroplasty is influenced by various patient factors, including major depressive disorder (MDD). Therefore, this study aimed to compare the patient perception of pain and opioid consumption between patients with and without MDD who received either a total knee arthroplasty (TKA) or total hip arthroplasty (THA). Specifically, we compared (1) pain intensity, (2) lengths of stay, (3) opioid consumption, and (4) patient perception of pain control.

METHODS

We reviewed our institutional Press Ganey database to identify patients with a diagnosis of MDD who received a THA (n = 48) and TKA (n = 68) between 2012 and 2016. An independent samples t-test and chi-square analyses were conducted to assess continuous and categorical variables, respectively. Analysis of covariance assessed the effects of depression on postoperative pain intensity. Mixed-design analysis of variance assessed the difference in opioid consumption between groups.

RESULTS

Patients with MDD who received THA or TKA demonstrated a higher mean pain intensity score when compared to those without MDD; however, this was not statistically different (235.6 vs 207.7; P = .264 and 214.8 vs 185.1; P = .055, respectively). Patients with MDD who received THA or TKA consumed more opioids when compared to those without MDD (P = .048 and P = .038, respectively).

CONCLUSION

Patients with MDD undergoing total joint arthroplasty consume more opioids compared to their matched cohort during the immediate postoperative period. Identifying patient-specific factors, such as MDD, could help arthroplasty surgeons modulate patients' course of recovery. These findings warrant more cooperation between arthroplasty surgeons and primary care providers to optimize outcome.

Were VCF patients at higher risk of mortality following the 2009 publication of the vertebroplasty "sham" trials?

The 5-year period following 2009 saw a steep reduction in vertebral augmentation volume and was associated with elevated mortality risk in vertebral compression fracture (VCF) patients. The risk of mortality following a VCF diagnosis was 85.1% at 10 years and was found to be lower for balloon kyphoplasty (BKP) and vertebroplasty (VP) patients.

INTRODUCTION

BKP and VP are associated with lower mortality risks than non-surgical management (NSM) of VCF. VP versus sham trials published in 2009 sparked controversy over its effectiveness, leading to diminished referral volumes. We hypothesized that lower BKP/VP utilization would lead to a greater mortality risk for VCF patients.

METHODS

BKP/VP utilization was evaluated for VCF patients in the 100% US Medicare data set (2005-2014). Survival and morbidity were analyzed by the Kaplan-Meier method and compared between NSM, BKP, and VP using Cox regression with adjustment by propensity score and various factors.

RESULTS

The cohort included 261,756 BKP (12.6%) and 117,232 VP (5.6%) patients, comprising 20% of the VCF patient population in 2005, peaking at 24% in 2007-2008, and declining to 14% in 2014. The propensity-adjusted mortality risk for VCF patients was 4% (95% CI, 3-4%; p < 0.001) greater in 2010-2014 versus 2005-2009. The 10-year risk of mortality for the overall cohort was 85.1%. BKP and VP cohorts had a 19% (95% CI, 19-19%; p < 0.001) and 7% (95% CI, 7-8%; p < 0.001) lower propensity-adjusted 10-year mortality risk than the NSM cohort, respectively. The BKP cohort had a 13% (95% CI, 12-13%; p < 0.001) lower propensity-adjusted 10-year mortality risk than the VP cohort.

CONCLUSIONS

Changes in treatment patterns following the 2009 VP publications led to fewer augmentation procedures. In turn, the 5-year period following 2009 was associated with elevated mortality risk in VCF patients. This provides insight into the implications of treatment pattern changes and associated mortality risks.

Repeated Morphine Produces Sensitization to Reward and Tolerance to Antiallodynia in Male and Female Rats with Chemotherapy-Induced Neuropathy

Paclitaxel is a cancer chemotherapy drug with adverse effects that include chemotherapy-induced neuropathic pain (CINP) as well as depression of behavior and mood. In the clinical setting, opioids are often used concurrently with or after chemotherapy to treat pain related to the cancer or CINP, but repeated opioid exposure can also increase the risk of opioid abuse. In this study, male and female Sprague-Dawley rats were used to test the hypothesis that repeated 3.2-mg/kg doses of morphine would induce tolerance to its antinociceptive effects in a mechanical sensitivity assay and increased expression of its abuse-related rewarding effects in an assay of intracranial self-stimulation (ICSS). Three weeks after four injections of vehicle or 2.0 mg/kg of paclitaxel, the initial morphine dose-effect curves were determined in both assays. Subsequently, rats were treated with 3.2 mg/kg per day morphine for 6 days. On the final day of testing, morphine dose-effect curves were redetermined in both assays. On initial exposure, morphine produced dose-dependent antiallodynia in the assay of mechanical sensitivity, but it produced little or no rewarding effects in the assay of ICSS. After 6 days of repeated treatment, morphine antiallodynia decreased, and morphine reward increased. Females exhibited greater morphine reward on initial exposure than males, but repeated morphine eliminated this sex difference. These results suggest that repeated morphine may produce tolerance to therapeutically beneficial analgesic effects of morphine but increased sensitivity to abuse-related rewarding effects of morphine in subjects treated with paclitaxel.