Opioids, pain, the brain, and hyperkatifeia: a framework for the rational use of opioids for pain

PT-IN-MIND: study protocol for a multisite randomised feasibility trial investigating physical therapy with integrated mindfulness (PT-IN-MIND) for patients with chronic musculoskeletal pain and long-term opioid treatment who attend outpatient physical therapy

INTRODUCTION

Many individuals receiving outpatient physical therapy have musculoskeletal pain and up to one-third use prescription opioids. The impact of physical therapist-led mindfulness-based interventions integrated with evidence-based physical therapy (I-EPT) to manage patients with chronic musculoskeletal pain and long-term opioid treatment has not been elucidated. This project evaluates the feasibility of conducting a cluster randomised trial to test the effectiveness of I-EPT.

METHODS AND ANALYSIS

Study 1 aim: Refine and manualise the I-EPT treatment protocol. Our approach will use semistructured interviews of patients and physical therapists to refine an I-EPT training manual. Study 2 aim: Evaluate different intensities of physical therapist training programmes for the refined I-EPT treatment protocol. Physical therapists will be randomised 1:1:1 to high-intensity training (HighIT), low-IT (LowIT) training and no training arms. Following training, competency in the provision of I-EPT (LowIT and HighIT groups) will be assessed using standardised patient simulations. Study 3 aim: Evaluate the feasibility of the I-EPT intervention across domains of the Reach, Effectiveness, Adoption, Implementation, Maintenance implementation framework. The refined I-EPT treatment protocol will be tested in two different health systems with 90 patients managed by the randomised physical therapists. The coprimary endpoints for study 3 are the proportions of the Pain, Enjoyment of Life and General Activity Scale and the Timeline Followback for opioid use/dose collected at 12 weeks.

ETHICS AND DISSEMINATION

Ethics approval for the study was obtained from the University of Utah, University of Florida and Florida State University Institutional Review Boards. Informed consent is required for participant enrolment in all phases of this project. On completion, study data will be made available in compliance with NIH data sharing policies.

TRIAL REGISTRATION NUMBER

NCT05875207.

Commentary With Study Protocol: Implementation and Effectiveness of Mindfulness-Oriented Recovery Enhancement (MORE) as an Adjunct to Methadone Treatment for Opioid Use Disorder (IMPOWR-MORE)

Traditional methadone treatment (MT) for opioid use disorder (OUD) fails to systematically address the physical pain, emotion dysregulation, and reward processing deficits that co-occur with OUD, and novel interventions that address these issues are needed to improve MT outcomes. Mindfulness-Oriented Recovery Enhancement (MORE) remediates the hedonic dysregulation in brain reward systems that is associated with OUD. Our pilot and phase 2 randomized controlled trials of MORE were the first to demonstrate MORE's feasibility, acceptability, and efficacy as delivered in MT clinics; MORE significantly reduced drug use (eg, benzodiazepines, barbiturates, cocaine, marijuana, opioids, and other drugs), craving, depression, anxiety, and pain among people with OUD. However, uptake of novel, efficacious interventions like MORE may be slow in MT because time and resources are often limited. Therefore, to best address potential implementation issues and to optimize future MORE implementation and dissemination, in this study, we will utilize a Type 2, Hybrid Implementation-Effectiveness study design. We will not only evaluate MORE's effectiveness but also assess barriers and facilitators to integrating MORE into MT. MT clinicians will receive training in (1) a higher intensity MORE implementation strategy consisting of training in the full MORE treatment manual or (2) a minimal intensity implementation strategy consisting of a simple, scripted mindfulness practice (SMP) extracted from the MORE treatment manual with minimal training. We aim to: (1) using a Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework, examine barriers and facilitators to implementation of MORE and SMP in MT, and evaluate strategies for optimizing training, fidelity, and engagement, (2) optimize existing MORE and SMP training and implementation toolkits, including adaptable resources that can accelerate the translation of evidence into practice, and (3) compared to usual MT, evaluate the relative effectiveness of MORE plus MT or SMP plus MT (N = 450).

Withdrawal interference scale: a novel measure of withdrawal-related life disruption in opioid use disorder and alcohol use disorder

Background: Hyperkatifeia describes amplified emotional and motivational withdrawal due to addiction-related sensitization of brain-stress-systems. Hyperkatifeia has been proposed as a target for addiction treatment development. However, translation of basic research in this area will require new tools designed to measure hyperkatifeia and related phenomena outside of laboratory settings.Objectives: We define a novel concept, withdrawal interference, and introduce a new tool - the Withdrawal Interference Scale (WIS) - which measures the impact of withdrawal on daily life among individuals with OUD or AUD.Methods: Described are the combined results of three separate cross-sectional studies. The structural validity, convergent validity, construct validity, trans-diagnostic (AUD/OUD) configural, metric, and scalar invariance, internal consistency, and composite reliability of WIS was tested among three independent samples of 1) treatment-seeking adults with OUD (n = 132), 2) treatment-seeking adults with AUD (n = 123), and 3) non-treatment-seeking adults with OUD (n = 140). Males numbered 218 and females were 163.Results: WIS exhibited structural validity (1 factor), convergent validity (average variance extracted .670-.676), construct validity, trans-diagnostic configural (χ2/df = 2.10), metric (Δχ2 = 5.70, p = .681), and scalar invariance (Δχ2 = 12.34, p = .338), internal consistency (α .882-928), and composite reliability (.924-.925).Conclusion: These results suggest WIS is a valid and reliable instrument for measuring withdrawal-related life disruption in AUD and OUD. Further, given our findings of transdiagnostic measurement invariance, WIS scores of individuals with AUD and OUD can be meaningfully compared in future statistical analyses.

Impact of Opioid Dose Reductions on Patient-Reported Mental Health and Suicide-Related Behavior and Relationship to Patient Choice in Tapering Decisions

Mental health and suicide-related harms resulting from prescription opioid tapering are poorly documented and understood. Six health systems contributed opioid prescribing data from January 2016 to April 2020. Patients 18 to 70 years old with evidence of opioid tapering participated in semi-structured interviews. Individuals who experienced suicide attempts were oversampled. Family members of suicide decedents who had experienced opioid tapering were also interviewed. Interviews were analyzed using thematic analysis. The study participants included 176 patients and 16 family members. Patients were 68% female, 80% White, and 15% Hispanic, mean age 58. All family members were female spouses of White, non-Hispanic male decedents. Among the subgroup (n = 60) who experienced a documented suicide attempt, reported experiencing suicidal ideation during tapering, or were family members of suicide decedents, 40% reported that opioid tapering exacerbated previously recognized mental health issues, and 25% reported that tapering triggered new-onset mental health concerns. Among participants with suicide behavior, 47% directly attributed it to opioid tapering. Common precipitants included increased pain, reduced life engagement, sleep problems, withdrawal, relationship dissolution, and negative consequences of opioid substitution with other substances for pain relief. Most respondents reporting suicide behavior felt that the decision to taper was made by the health care system or a clinician (67%) whereas patients not reporting suicide behavior were more likely to report it was their own decision (42%). This study describes patient-reported mental health deterioration or suicide behavior while tapering prescription opioids. Clinicians should screen for, monitor, and treat suicide behavior while assisting patients in tapering opioids. PERSPECTIVE: This work describes changes in patient-reported mental health and suicide behavior while tapering prescription opioids. Recommendations for improving care include mental health and suicide risk screening during and following opioid tapering.

Pain and its Perceived Relatedness to the Onset, Maintenance, and Relapse of Opioid use Disorder: A Descriptive Study of Non-Treatment-Seeking Individuals

Background

Previous research has found chronic pain to be prevalent among individuals with opioid use disorder (OUD). The perception that pain is related to OUD onset, maintenance, relapse, and treatment delay has been noted in this population. However, prior works primarily involved treatment-engaged populations. Scant research describes such perceptions among non-treatment-seeking individuals.

Aims

This study describes pain burden and perceptions regarding the role of pain in OUD onset, maintenance, relapse, and addiction treatment delay in a sample of individuals with untreated OUD.

Methods

This cross-sectional study surveyed syringe exchange participants (n = 141). Participants responded to a survey including Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition OUD criteria, pain survey scales, demographic characteristics, and questions regarding pain and its perceived relatedness to aspects of OUD.

Results

Most participants reported pain within the past 4 weeks (127, 91.4%). Data displayed a skew toward more intense pain ratings, with 120 reporting their pain as greater than mild (86.3%). A majority of participants agreed that pain was responsible for their OUD onset (79, 56.4%), maintenance (76, 54.3%), past relapse experience (82, 57.9%), and treatment delay (81, 57.9%). Correlative analyses revealed that pain severity and interference measures displayed moderate and statistically significant associations with extent of perceived relatedness of pain to these aspects of OUD.

Conclusions

Among this sample of individuals with untreated OUD, pain and pain interference were prevalent. Pain was perceived to be related to OUD onset, maintenance, relapse, and treatment delay by a majority of the sample. These findings are in accordance with and expand upon prior works.

Abbreviations

OUD: opioid use disorder; DSM-5: Diagnostic and Statistical Manual 5; BPI: Brief Pain Inventory; NIDA: National Institute on Drug Abuse; IASP: International Association for the Study of Pain; MOUD: Medications for Opioid Use Disorder; IQR: Interquartile Range.

Withdrawal catastrophizing scale: initial psychometric properties and implications for the study of opioid use disorder and hyperkatifeia

Background: Discovery of modifiable factors influencing subjective withdrawal experience might advance opioid use disorder (OUD) research and precision treatment. This study explores one factor - withdrawal catastrophizing - a negative cognitive and emotional orientation toward withdrawal characterized by excessive fear, worry or inability to divert attention from withdrawal symptoms.Objectives: We define a novel concept - withdrawal catastrophizing - and present an initial evaluation of the Withdrawal Catastrophizing Scale (WCS).Methods: Prospective observational study (n = 122, 48.7% women). Factor structure (exploratory factor analysis) and internal consistency (Cronbach's α) were assessed. Predictive validity was tested via correlation between WCS and next-day subjective opiate withdrawal scale (SOWS) severity. The clinical salience of WCS was evaluated by correlation between WCS and withdrawal-motivated behaviors including risk taking, OUD maintenance, OUD treatment delay, history of leaving the hospital against medical advice and buprenorphine-precipitated withdrawal.Results: WCS was found to have a two-factor structure (distortion and despair), strong internal consistency (α = .901), and predictive validity - Greater withdrawal catastrophizing was associated with next-day SOWS (rs (99) = 0.237, p = .017). Withdrawal catastrophizing was also correlated with risk-taking behavior to relieve withdrawal (rs (119) = 0.357, p < .001); withdrawal-motivated OUD treatment avoidance (rs (119) = 0.421, p < .001), history of leaving the hospital against medical advice (rs (119) = 0.373, p < .001) and buprenorphine-precipitated withdrawal (rs (119) = 0.369, p < .001).Conclusion: This study provides first evidence of withdrawal catastrophizing as a clinically important phenomenon with implications for the future study and treatment of OUD.

Opioid-induced hypogonadism in opioid use disorder, its role in negative reinforcement, and implications for treatment and retention

Hypogonadism is a highly prevalent complication of chronic opioid use associated with a constellation of affective, algesic, and cognitive symptoms as well as decreased quality of life. Given that the mainstays of pharmacologic opioid use disorder (OUD) treatment - methadone and buprenorphine - are themselves agonists or partial agonists at the mu opioid receptor, opioid-induced hypogonadism (OIH) remains an underappreciated clinical concern throughout the course of OUD treatment. Prominent theoretical frameworks for OUD emphasize the importance of negative reinforcement and hyperkatifeia, defined as the heightened salience of negative emotional and motivational states brought on by chronic opioid use. In this perspective article, we highlight the striking parallels between the symptom domains of hyperfakifeia and hypogonadism in males, who comprise the vast majority of existing clinical research on OIH. By extension we propose that future research and ultimately clinical care should focus on the identification and treatment of OIH in OUD patients to help address the longstanding paradox of poor treatment retention despite efficacious therapies, particularly in the setting of the current opioid overdose epidemic driven by high potency synthetic opioids such as fentanyl. We then review evidence from chronic pain patients that testosterone replacement provides clinically significant benefits to men with OIH. Finally, using this framework, we compare extant OUD therapeutics and discuss critical gaps in the clinical literature-including the relative dearth of data regarding hypothalamic-pituitary-gonadal function in females who use opioids-where future study should be focused.

Alcohol Use Disorder Treatment: Problems and Solutions

Alcohol use disorder (AUD) afflicts over 29 million individuals and causes more than 140,000 deaths annually in the United States. A heuristic framework for AUD includes a three-stage cycle-binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation-that provides a starting point for exploring the heterogeneity of AUD with regard to treatment. Effective behavioral health treatments and US Food and Drug Administration-approved medications are available but greatly underutilized, creating a major treatment gap. This review outlines challenges that face the alcohol field in closing this treatment gap and offers solutions, including broadening end points for the approval of medications for the treatment of AUD; increasing the uptake of screening, brief intervention, and referral to treatment; addressing stigma; implementing a heuristic definition of recovery; engaging early treatment; and educating health-care professionals and the public about challenges that are associated with alcohol misuse. Additionally, this review focuses on broadening potential targets for the development of medications for AUD by utilizing the three-stage heuristic model of addiction that outlines domains of dysfunction in AUD and the mediating neurobiology of AUD.

Neuroplasticity of the extended amygdala in opioid withdrawal and prolonged opioid abstinence

Opioid use disorder is characterized by excessive use of opioids, inability to control its use, a withdrawal syndrome upon discontinuation of opioids, and long-term likelihood of relapse. The behavioral stages of opioid addiction correspond with affective experiences that characterize the opponent process view of motivation. In this framework, active involvement is accompanied by positive affective experiences which gives rise to "reward craving," whereas the opponent process, abstinence, is associated with the negative affective experiences that produce "relief craving." Relief craving develops along with a hypersensitization to the negatively reinforcing aspects of withdrawal during abstinence from opioids. These negative affective experiences are hypothesized to stem from neuroadaptations to a network of affective processing called the "extended amygdala." This negative valence network includes the three core structures of the central nucleus of the amygdala (CeA), the bed nucleus of the stria terminalis (BNST), and the nucleus accumbens shell (NAc shell), in addition to major inputs from the basolateral amygdala (BLA). To better understand the major components of this system, we have reviewed their functions, inputs and outputs, along with the associated neural plasticity in animal models of opioid withdrawal. These models demonstrate the somatic, motivational, affective, and learning related models of opioid withdrawal and abstinence. Neuroadaptations in these stress and motivational systems are accompanied by negative affective and aversive experiences that commonly give rise to relapse. CeA neuroplasticity accounts for many of the aversive and fear-related effects of opioid withdrawal via glutamatergic plasticity and changes to corticotrophin-releasing factor (CRF)-containing neurons. Neuroadaptations in BNST pre-and post-synaptic GABA-containing neurons, as well as their noradrenergic modulation, may be responsible for a variety of aversive affective experiences and maladaptive behaviors. Opioid withdrawal yields a hypodopaminergic and amotivational state and results in neuroadaptive increases in excitability of the NAc shell, both of which are associated with increased vulnerability to relapse. Finally, BLA transmission to hippocampal and cortical regions impacts the perception of conditioned aversive effects of opioid withdrawal by higher executive systems. The prevention or reversal of these varied neuroadaptations in the extended amygdala during opioid withdrawal could lead to promising new interventions for this life-threatening condition.

Divergent emotional and autonomic responses to Cyberball in patients with opioid use disorder on opioid agonist treatment

The perception of social exclusion among patients with opioid use disorder (OUD) could be affected by long-term opioid use. This study explores the emotional and cardiac autonomic responses to an experience of ostracism in a sample of participants with OUD on opioid agonist treatment (OAT). Twenty patients with OUD and twenty healthy controls (HC) performed a ball-tossing game (Cyberball) with two conditions: Inclusion and Ostracism. We measured self-reported ratings of perceived threat towards one's fundamental needs and respiratory sinus arrhythmia (RSA) immediately after the game and 10 min after Ostracism (Reflective stage). Following ostracism, participants with OUD self-reported blunted feelings of threat to the fundamental need to belong. RSA levels were significantly suppressed immediately after ostracism and during the Reflective stage in comparison with HC, indicating an autonomic alteration in response to threatening social situations. Finally, only among HC higher perceived threats towards fundamental needs predicted increases in RSA levels, suggesting an adaptive vagal regulation in response to a perceived threat. Conversely, among patients with OUD the subjective response to ostracism was not associated with the autonomic reaction. OAT may have a protective effect against negative feelings of ostracism. However patients with OUD on OAT present poor autonomic regulation in response to social threats, which could reflect their trait hypersensitivity to social rejection.

Opioids Induce Bidirectional Synaptic Plasticity in a Brainstem Pain Center in the Rat

Opioids are powerful analgesics commonly used in pain management. However, opioids can induce complex neuroadaptations, including synaptic plasticity, that ultimately drive severe side effects, such as pain hypersensitivity and strong aversion during prolonged administration or upon drug withdrawal, even following a single, brief administration. The lateral parabrachial nucleus (LPBN) in the brainstem plays a key role in pain and emotional processing; yet, the effects of opioids on synaptic plasticity in this area remain unexplored. Using patch-clamp recordings in acute brainstem slices from male and female Sprague Dawley rats, we demonstrate a concentration-dependent, bimodal effect of opioids on excitatory synaptic transmission in the LPBN. While a lower concentration of DAMGO (0.5 µM) induced a long-term depression of synaptic strength (low-DAMGO LTD), abrupt termination of a higher concentration (10 µM) induced a long-term potentiation (high-DAMGO LTP) in a subpopulation of cells. LTD involved a metabotropic glutamate receptor (mGluR)-dependent mechanism; in contrast, LTP required astrocytes and N-methyl-D-aspartate receptor (NMDAR) activation. Selective optogenetic activation of spinal and periaqueductal gray matter (PAG) inputs to the LPBN revealed that, while LTD was expressed at all parabrachial synapses tested, LTP was restricted to spino-parabrachial synapses. Thus, we uncovered previously unknown forms of opioid-induced long-term plasticity in the parabrachial nucleus that potentially modulate some adverse effects of opioids. PERSPECTIVE: We found a previously unrecognized site of opioid-induced plasticity in the lateral parabrachial nucleus, a key region for pain and emotional processing. Unraveling opioid-induced adaptations in parabrachial function might facilitate the identification of new therapeutic measures for addressing adverse effects of opioid discontinuation such as hyperalgesia and aversion.

Questioning the Right to Pain Relief and Its Role in the Opioid Epidemic

The new discipline of palliative care helped to establish the right to pain relief at the end of life and the necessity of using opioids to achieve that goal. Professional pain organizations followed the United Nations' model for universal human rights in their declaration of a universal right to pain management. Both palliative care and pain medicine specialties worked to establish pain as a legitimate focus of medical treatment separate from its association with disease. Pain intensity became the metric used to determine the need for treatment and the success of that treatment. Opioids were favored as the most reliable and feasible means to reduced pain intensity. The Harrison Act of 1914 restricted legitimate opioid use to that prescribed by medical professionals as analgesics. This legislation helped establish opioids as specific painkillers that had a distinct capacity to induce addiction. This understanding of opioids as having distinct and separable analgesic and addictive potential was challenged by the 1970s discovery of an endogenous opioid system, which integrates pain and reward functions to support survival. Our modern pain neurophysiology places the patient with pain in a passive position from which it makes sense to assert a right to pain relief. To prevent future opioid epidemics we need to abandon clinical outpatient use of pain intensity scores and redefine the medical necessity of pain treatment as less about the reduction of pain intensity and more about the capacity to pursue personally valued activities.

Theoretical Frameworks and Mechanistic Aspects of Alcohol Addiction: Alcohol Addiction as a Reward Deficit/Stress Surfeit Disorder

Alcohol use disorder (AUD) can be defined by a compulsion to seek and take alcohol, the loss of control in limiting intake, and the emergence of a negative emotional state when access to alcohol is prevented. Alcohol use disorder impacts multiple motivational mechanisms and can be conceptualized as a disorder that includes a progression from impulsivity (positive reinforcement) to compulsivity (negative reinforcement). Compulsive drug seeking that is associated with AUD can be derived from multiple neuroadaptations, but the thesis argued herein is that a key component involves the construct of negative reinforcement. Negative reinforcement is defined as drug taking that alleviates a negative emotional state. The negative emotional state that drives such negative reinforcement is hypothesized to derive from the dysregulation of specific neurochemical elements that are involved in reward and stress within basal forebrain structures that involve the ventral striatum and extended amygdala, respectively. Specific neurochemical elements in these structures include decreases in reward neurotransmission (e.g., decreases in dopamine and opioid peptide function in the ventral striatum) and the recruitment of brain stress systems (e.g., corticotropin-releasing factor [CRF]) in the extended amygdala, which contributes to hyperkatifeia and greater alcohol intake that is associated with dependence. Glucocorticoids and mineralocorticoids may play a role in sensitizing the extended amygdala CRF system. Other components of brain stress systems in the extended amygdala that may contribute to the negative motivational state of withdrawal include norepinephrine in the bed nucleus of the stria terminalis, dynorphin in the nucleus accumbens, hypocretin and vasopressin in the central nucleus of the amygdala, and neuroimmune modulation. Decreases in the activity of neuropeptide Y, nociception, endocannabinoids, and oxytocin in the extended amygdala may also contribute to hyperkatifeia that is associated with alcohol withdrawal. Such dysregulation of emotional processing may also significantly contribute to pain that is associated with alcohol withdrawal and negative urgency (i.e., impulsivity that is associated with hyperkatifeia during hyperkatifeia). Thus, an overactive brain stress response system is hypothesized to be activated by acute excessive drug intake, to be sensitized during repeated withdrawal, to persist into protracted abstinence, and to contribute to the compulsivity of AUD. The combination of the loss of reward function and recruitment of brain stress systems provides a powerful neurochemical basis for a negative emotional state that is responsible for the negative reinforcement that at least partially drives the compulsivity of AUD.

Chronic pain, chronic stress and substance use: overlapping mechanisms and implications

Chronic pain is among the most common reasons adults in the U.S. seek medical care. Despite chronic pain's substantial impact on individuals' physical, emotional, and financial wellness, the biologic underpinnings of chronic pain remain incompletely understood. Such deleterious impact on an individuals' wellness is also manifested in the substantial co-occurrence of chronic stress with chronic pain. However, whether chronic stress and adversity and related alcohol and substance misuse increases risk of developing chronic pain, and, if so, what the overlapping psychobiological processes are, is not well understood. Individuals suffering with chronic pain find alleviation through prescription opioids as well as non-prescribed cannabis, alcohol, and other drugs to control pain, and use of these substances have grown significantly. Substance misuse also increases experience of chronic stress. Thus, given the evidence showing a strong correlation between chronic stress and chronic pain, we aim to review and identify overlapping factors and processes. We first explore the predisposing factors and psychologic features common to both conditions. This is followed by examining the overlapping neural circuitry of pain and stress in order to trace a common pathophysiologic processes for the development of chronic pain and its link to substance use. Based on the previous literature and our own findings, we propose a critical role for ventromedial prefrontal cortex dysfunction, an overlapping brain area associated with the regulation of both pain and stress that is also affected by substance use, as key in the risk of developing chronic pain. Finally, we identify the need for future research in exploring the role of medial prefrontal circuits in chronic pain pathology. Critically, in order to alleviate the enormous burden of chronic pain without exacerbating the co-occurring substance misuse crisis, we emphasize the need to find better approaches to treat and prevent chronic pain.

Extended access to fentanyl vapor self-administration leads to addiction-like behaviors in mice: Blood chemokine/cytokine levels as potential biomarkers

Rodent models are useful for understanding the mechanisms that underlie opioid addiction, but most preclinical studies have focused on rewarding and consummatory aspects of opioids without components of dependence-induced escalation of drug taking or seeking. We characterized several opioid-related behaviors in mice using a model of vaporized fentanyl self-administration. Male and female C57BL/6J mice were assigned to short-access (ShA; 1 h, nondependent) or long-access (LgA; 6 h, dependent) fentanyl vapor self-administration and subsequently tested in a battery of behavioral tests, followed by blood collection during withdrawal. Compared with mice in the ShA group, mice in the LgA group escalated their fentanyl intake, were more motivated to work to obtain the drug, exhibited greater hyperalgesia, and exhibited greater signs of naloxone-precipitated withdrawal. Principal component analysis indicated the emergence of two independent behavioral constructs: "intake/motivation" and "hyperalgesia/punished seeking." In mice in the LgA condition only, "hyperalgesia/punished seeking" was associated with plasma levels of proinflammatory interleukin-17 (IL-17), chemokine (C-C motif) ligand 4 (CCL-4), and tumor necrosis factor α (TNF-α). Overall, the results suggest that extended access to opioids leads to addiction-like behavior, and some constructs that are associated with addiction-like behavior may be associated with levels of the proinflammatory cytokines/chemokines IL-17, TNF-α, and CCL-4 in blood.

Mindfulness-Oriented Recovery Enhancement for Addictive Behavior, Psychiatric Distress, and Chronic Pain: A Multilevel Meta-Analysis of Randomized Controlled Trials

Objectives

Methods

Results

Conclusions

Meta-analysis Pre-registration: PROSPERO #CRD42022319006

Supplementary Information

Differential Experience of Interdose Withdrawal During Long-Term Opioid Therapy and its Association With Patient and Treatment Characteristics: A Latent Class Analysis in Chronic Pain Population

Opioid withdrawal is characterized by a set of physical and psychological symptoms that depend on both opioid and patient specific characteristics. The present study aims to identify different latent classes of chronic pain patients according to the type of opioid withdrawal symptoms experienced, and to analyze the relationships between the classes and demographic, opioid therapy, psychological and substance use variables. This cross-sectional descriptive study included 391 chronic pain patients on long-term opioid therapy. A Latent Class Analysis (LCA) identified 3 classes (BIC = 7051.89, entropy = .87, LRTs P < .01). The mild withdrawal class showed low probabilities of presenting physical and psychological symptoms, the moderate withdrawal class was characterized by experiencing psychological symptoms, and the severe withdrawal class stood out for high probabilities of presenting both types of symptoms. The classes differed from each other, with higher rates of moderate-severe POUD, opioid misuse, anxiety, depression, and greater pain intensity and interference in more severe withdrawal classes (P < .05). The multinomial logistic regression showed that moderate-severe POUD and anxiety were the strongest variables related to moderate (OR_POUD = 3.34, OR_Anxiety = 2.58) and severe withdrawal classes (OR_POUD = 4.26, OR_Anxiety = 5.15). Considering that POUD and anxiety were strongly related to a more severe withdrawal syndrome, the inclusion of psychological interventions in pain management seems critical in this population. PERSPECTIVE: Although interdose opioid withdrawal is common in chronic pain patients, this study shows 3 different patterns in its experience (mild, moderate, and severe withdrawal). A more severe withdrawal may result in reduced effectiveness of opioids in relieving pain and increased negative consequences, such as higher risk of POUD. Findings that could help improve chronic pain management.

The association between pain and central nervous system depressing medication among hospitalised Norwegian older adults

OBJECTIVES

Central nervous system depressant medications (CNSD) including benzodiazepines, z-hypnotics and opioids are regularly prescribed for the older patient. These medications are linked to dependence and associated with severe side effects in some older patients. Consensus recommendations for this group suggest limiting their use. We have recently described a high proportion of long-term CNSD use and dependence among older in-hospital patients. In this study, we aim to investigate factors associated with pain intensity and presentation of pain among older adults with long-term use of CNSDs compared to non-users.

METHODS

Two hundred and forty six elderly hospitalised patients were recruited consecutively in a cross-sectional study. Data was collected from patients and electronic health records (EHR). Independent variables were sex, age, education, emotional symptoms (hospital anxiety and depression scale [HADS]), cognitive function (Mini-mental State Examination test [MMSE]), comorbidity (cumulative illness rating score - geriatrics [CIRS-G]), loneliness (the six-item De Jong Gierveld Loneliness Scale) and prolonged (≥4 weeks) use of any CNSDs or prolonged use of opioids (≥4 weeks). All variables, including pain intensity, were collected at one time point consistent with the cross-sectional study design. Statistical analyses included descriptive statistics and linear regression models using the above mentioned variables and pain intensity (visual analogue scale for pain intensity [VAS] pain 0-100) as outcome. Additional information regarding pain presentation was extracted from the patients' EHR.

RESULTS

Mean pain intensity VAS (SD) was 35.2 (30.4) and 18.1 (24.2) respectively, for patients with vs. without prolonged use of CNSDs. In the multivariable linear regression analysis, prolonged use of CNSDs and opioids were positively associated with pain intensity (VAS) (regression coefficient (95% CI) 20.7 (11.0; 30.3), p<0.001, and 19.8 (5.7; 33.8), p=0.006, respectively), while sex, age, education, MMSE, HADS, CIRS-G and loneliness scores were not. Pain related to back (23.2%) and lower extremities (23.2%) were most common pain sites, and those with one or more pain sites reported overall higher pain intensity compared to those with no reported pain sites (p<0.006).

CONCLUSIONS

Prolonged use of CNSD medications as well as prolonged use of opioids are both positively associated with pain intensity. The results may have implications for treatment and long-term pain management for older patients.

Simulated opioid choice linked to opioid use disorder severity among veterans with chronic pain: initial validation of a novel paradigm

Background: Modeling addictive behavior among individuals with, or at risk for, opioid use disorder (OUD) in a way that is accurate, ethical, and reproducible presents a pressing concern. OUD risk is elevated among people with chronic pain on long-term opioid therapy (LTOT).Objectives: To provide initial validation of a novel opioid preference task as an index of OUD and its symptomatology among veterans prescribed opioids for chronic pain, a population at high risk for poor opioid-related outcomes. The relative ease by which such a paradigm can be implemented and performed in clinical contexts, including enabling investigation of opioid reinforcement and drug-seeking behavior while avoiding ethical pitfalls associated with direct drug administration, could make this task an attractive approach for potentially tracking OUD symptoms.Methods: We studied 87 veterans (74 males, 13 females) on LTOT for chronic pain - 33 of whom had OUD diagnoses. Participants completed a picture-viewing choice task to assess preference for viewing opioid-related images in comparison with standardized pleasant, unpleasant, neutral, and blank images. Opioid-related choice, measured by vigor of button pressing, was tested for association with OUD severity (measured by symptom counts), as well as craving and anhedonia.Results: Choice for opioid-related images was positively correlated with OUD severity (i.e., number of DSM-5 measured OUD symptoms) (r = 0.38, p < .001), particularly among those meeting diagnostic criteria for OUD (r = 0.47, p = .006). Neither craving nor anhedonia correlated with opioid-related choice.Conclusions: Our results provide initial validation for a new opioid picture-choice paradigm in patients with chronic pain.

NEURONAL CORRELATES OF HYPERALGESIA AND SOMATIC SIGNS OF HEROIN WITHDRAWAL IN MALE AND FEMALE MICE

Opioid withdrawal involves the manifestation of motivational and somatic symptoms. However, the brain structures that are involved in the expression of different opioid withdrawal signs remain unclear. We induced opioid dependence by repeatedly injecting escalating heroin doses in male and female C57BL/6J mice. We assessed hyperalgesia during spontaneous heroin withdrawal and somatic signs of withdrawal that was precipitated by the preferential µ-opioid receptor antagonist naloxone. Heroin-treated mice exhibited significantly higher hyperalgesia and somatic signs than saline-treated mice. Following behavioral assessment, we measured regional changes in brain activity by automated the counting of c-Fos expression (a marker of cellular activity). Using Principal Component Analysis, we determined the association between behavior (hyperalgesia and somatic signs of withdrawal) and c-Fos expression in different brain regions. Hyperalgesia was associated with c-Fos expression in the lateral hypothalamus, central nucleus of the amygdala, ventral tegmental area, parabrachial nucleus, dorsal raphe, and locus coeruleus. Somatic withdrawal was associated with c-Fos expression in the paraventricular nucleus of the thalamus, lateral habenula, dorsal raphe, and locus coeruleus. Thus, hyperalgesia and somatic withdrawal signs were each associated with c-Fos expression in unique sets of brain areas. The expression of c-Fos in the dorsal raphe and locus coeruleus was associated with both hyperalgesia and somatic withdrawal. Understanding common neurobiological mechanisms of acute and protracted opioid withdrawal may help identify new targets for treating this salient aspect of opioid use disorder.SIGNIFICANCE STATEMENTThe public impact of the opioid crisis has prompted an effort to understand the neurobiological mechanisms of opioid use disorder (OUD). The need to avoid withdrawal symptoms is hypothesized to drive compulsive drug-taking and -seeking in OUD. Thus, understanding the mechanisms of acute and protracted opioid withdrawal may help identify new targets for treating this salient aspect of OUD. We reported brain structures that are associated with the expression of hyperalgesia and somatic signs of opioid withdrawal in male and female heroin-dependent mice. Hyperalgesia during spontaneous opioid withdrawal and somatic withdrawal resulted in c-Fos expression in autonomic and limbic brain regions. The expression of c-Fos in the dorsal raphe and locus coeruleus were associated with both hyperalgesia and somatic withdrawal.

Complex Persistent Opioid Dependence-an Opioid-induced Chronic Pain Syndrome

OPINION STATEMENT

Long-term opioid therapy (LTOT) for chronic cancer and non-cancer pain is commonly ineffective in providing its stated goal of improving function through good control of pain. Opioid tapering (slow dose reduction and/or discontinuation), the logical solution, also appears to be ineffective among many patients on LTOT as it often leads to even worse pain control and function, leaving the patients and providers managing LTOT in a clinical conundrum with little treatment choices. Complex persistent opioid dependence (CPOD) was recently offered as a heuristic to explain this clinical conundrum exemplified by the ineffectiveness of both LTOT and opioid tapering. This manuscript provides a detailed description of the neurobehavioral underpinnings of CPOD, explaining how long-term opioid use can lead to more pain even while experiencing relief with each opioid dose. CPOD is characterized by the allostatic opponent mechanisms of neuroadaptations related to the progression of opioid dependence and tolerance involving nociceptive/anti-nociceptive brain systems causing opioid-induced hyperalgesia and reward/anti-reward systems causing hyperkatefia or suffering that induces pain experience through the cognitive/emotional component of pain mechanisms. "Opioid Induced Chronic Pain syndrome" (OICP) is offered as an alternate clinical diagnostic term instead of CPOD that has several limitations as a diagnosis term including poor patient acceptance due to stigma towards addiction and clinical confounding with opioid use disorder, a related but separate clinical entity. OICP with LTOT is conceptualized as a recoverable iatrogenic problem that can be managed by pain providers. Broad guidance on management of OICP is also provided.

Depression and Long-Term Prescription Opioid Use and Opioid Use Disorder: Implications for Pain Management in Cancer

OPINION STATEMENT

Preventing depression in cancer patients on long-term opioid therapy should begin with depression screening before opioid initiation and repeated screening during treatment. In weighing the high morbidity of depression and opioid use disorder in patients with chronic cancer pain against a dearth of evidence-based therapies studied in this population, patients and clinicians are left to choose among imperfect but necessary treatment options. When possible, we advise engaging psychiatric and pain/palliative specialists through collaborative care models and recommending mindfulness and psychotherapy to all patients with significant depression alongside cancer pain. Medications for depression should be reserved for moderate to severe symptoms. We recommend escitalopram/citalopram or sertraline among selective serotonin reuptake inhibitors (SSRIs), or the serotonin and norepinephrine reuptake inhibitors (SNRIs) duloxetine, venlafaxine, or desvenlafaxine if patients have a significant component of neuropathic pain or fibromyalgia. Tricyclic antidepressants (TCAs) (consider nortriptyline or desipramine, which have better anticholinergic profiles) should be considered for patients who do not respond to or tolerate SSRI/SNRIs. Existing evidence is inadequate to definitively recommend methylphenidate or novel agents, such as ketamine or psilocybin, as adjunctive treatments for cancer-related depression and pain. Physicians who treat patients with cancer pain should utilize universal precautions to limit the risk of non-medical opioid use (non-medical opioid use). Patients should be screened for non-medical opioid use behaviors at initial consultation and at regular intervals during treatment using a non-judgmental approach that reduces stigma. Co-management with an addiction specialist may be indicated for patients at high risk of non-medical opioid use and opioid use disorder. Buprenorphine and methadone are indicated for the treatment of opioid use disorder, and while they have not been systematically studied for treatment of opioid use disorder in patients with cancer pain, they do provide analgesia for cancer pain. While an interdisciplinary team approach to manage psychological stress may be beneficial, this may not be possible for patients treated outside of comprehensive cancer centers.

Anhedonia, Hyperkatifeia, and Negative Reinforcement in Substance Use Disorders

Drug addiction has been defined as a chronically relapsing disorder that is characterized by a compulsion to seek and take a drug or stimulus, the loss of control in limiting intake, and the emergence of a negative emotional state when access to the drug or stimulus is prevented, a component of which is anhedonia. The present review explores a heuristic framework for understanding the role of anhedonia in addiction, in which anhedonia is a key component of hyperkatifeia (conceptualized as the potentiated intensity of negative emotional/motivational symptoms during drug withdrawal) and negative reinforcement in addiction. The neural substrates that mediate such anhedonia and crosstalk between elements of hyperkatifeia that contribute to anhedonia are then explored, including crosstalk between physical pain and emotional pain systems. The present review explores current knowledge of neurochemical neurocircuitry changes that are associated with conditioned hyperkatifeia/anhedonia. The overall hypothesis is that the shift in motivation toward negative reinforcement in addiction reflects the allostatic misregulation of hedonic tone, such that drug taking makes anhedonia worse during the process of seeking temporary relief by compulsive drug taking, thereby perpetuating the addiction cycle and hedonic comorbidities that are associated with addiction.

Neurocircuitry basis of the opioid use disorder-post-traumatic stress disorder comorbid state: conceptual analyses using a dimensional framework

Understanding the interface between opioid use disorder (OUD) and post-traumatic stress disorder (PTSD) is challenging. By use of a dimensional framework, such as research domain criteria, convergent and targetable neurobiological processes in OUD-PTSD comorbidity can be identified. We hypothesise that, in OUD-PTSD, circuitry that is implicated in two research domain criteria systems (ie, negative valence and cognitive control) underpins dysregulation of incentive salience, negative emotionality, and executive function. We also propose that the OUD-PTSD state might be systematically investigated with approaches outlined within a neuroclinical assessment framework for addictions and PTSD. Our dimensional analysis of the OUD-PTSD state shows how first-line therapeutic approaches (ie, partial μ-type opioid receptor [MOR1] agonism) modulate overlapping neurobiological and clinical features and also provides mechanistic rationale for evaluating polytherapeutic strategies (ie, partial MOR1 agonism, κ-type opioid receptor [KOR1] antagonism, and α-2A adrenergic receptor [ADRA2A] agonism). A combination of these therapeutic mechanisms is projected to facilitate recovery in patients with OUD-PTSD by mitigating negative valence states and enhancing executive control.

Peripherally administered cannabinoid receptor 2 (CB2R) agonists lose anti-allodynic effects in TRPV1 knockout mice, while intrathecal administration leads to anti-allodynia and reduced GFAP, CCL2 and TRPV1 expression in the dorsal spinal cord and DRG

The transient receptor potential (TRP) superfamily of cation channels, of which the TRP vanilloid type 1 (TRPV1) receptor plays a critical role in inflammatory and neuropathic pain, is expressed on nociceptors and spinal cord dorsal horn neurons. TRPV1 is also expressed on spinal astrocytes and dorsal root ganglia (DRG) satellite cells. Agonists of the cannabinoid type 2 receptor (CB2R) suppress allodynia, with some that can bind TRPV1. The neuroimmune C-C class chemokine-2 (CCL2) expressed on injured DRG nociceptor cell bodies, Schwann cells and spinal astrocytes, stimulates immune cell accumulation in DRG and spinal cord, a known critical element in chronic allodynia. The current report examined whether two CB2R agonists, AM1710 and AM1241, previously shown to reverse light touch mechanical allodynia in rodent models of sciatic neuropathy, require TRPV1 activation that leads to receptor insensitivity resulting in reversal of allodynia. Global TRPV1 knockout (KO) mice with sciatic neuropathy given intrathecal or intraperitoneal AM1710 were examined for anti-allodynia followed by immunofluorescent microscopy analysis of lumbar spinal cord and DRG of astrocyte and CCL2 markers. Additionally, immunofluorescent analysis following intrathecal AM1710 and AM1241 in rat was performed. Data reveal that intrathecal AM1710 resulted in mouse anti-allodynia, reduced spinal astrocyte activation and CCL2 expression independent of TRPV1 gene deletion. Conversely, peripheral AM1710 in TRPV1-KO mice failed to reverse allodynia. In rat, intrathecal AM1710 and AM1241 reduced spinal and DRG TRPV1 expression, with CCL2-astrocyte and -microglial co-expression. These data support that CB2R agonists can impact spinal and DRG TRPV1 expression critical for anti-allodynia.

FACTORS CONTRIBUTING TO THE ESCALATION OF ALCOHOL CONSUMPTION

Understanding factors that contribute to the escalation of alcohol consumption is key to understanding how an individual transitions from non/social drinking to AUD and to providing better treatment. In this review, we discuss how the way ethanol is consumed as well as individual and environmental factors contribute to the escalation of ethanol consumption from intermittent low levels to consistently high levels. Moreover, we discuss how these factors are modelled in animals. It is clear a vast array of complex, interacting factors influence changes in alcohol consumption. Some of these factors act early in the acquisition of ethanol consumption and initial escalation, while others contribute to escalation of ethanol consumption at a later stage and are involved in the development of alcohol dependence. There is considerable need for more studies examining escalation associated with the formation of dependence and other hallmark features of AUD, especially studies examining mechanisms, as it is of considerable relevance to understanding and treating AUD.

Beating Pain with Psychedelics: Matter over Mind?

Basic pain research has shed light on key cellular and molecular mechanisms underlying nociceptive and phenomenological aspects of pain. Despite these advances, [[we still yearn for] the discovery of novel therapeutic strategies to address the unmet needs of about 70% of chronic neuropathic pain patients whose pain fails to respond to opioids as well as to other conventional analgesic agents. Importantly, a substantial body of clinical observations over the past decade cumulatively suggests that the psychedelic class of drugs may possess heuristic value for understanding and treating chronic pain conditions. The present review presents a theoretical framework for hitherto insufficiently understood neuroscience-based mechanisms of psychedelics' potential analgesic effects. To that end, searches of PubMed-indexed journals were performed using the following Medical Subject Headings' terms: pain, analgesia, inflammatory, brain connectivity, ketamine, psilocybin, functional imaging, and dendrites. Recursive sets of scientific and clinical evidence extracted from this literature review were summarized within the following key areas: (1) studies employing psychedelics for alleviation of physical and emotional pain; (2) potential neuro-restorative effects of psychedelics to remediate the impaired connectivity underlying the dissociation between pain-related conscious states/cognitions and the subcortical activity/function leading to the eventual chronicity through immediate and long-term effects on dentritic plasticity; (3) anti-neuroinflammatory and pro-immunomodulatory actions of psychedelics as the may pertain to the role of these factors in the pathogenesis of neuropathic pain; (4) safety, legal, and ethical consideration inherent in psychedelics' pharmacotherapy. In addition to direct beneficial effects in terms of reduction of pain and suffering, psychedelics' inclusion in the analgesic armamentarium will contribute to deeper and more sophisticated insights not only into pain syndromes but also into frequently comorbid psychiatric condition associated with emotional pain, e.g., depressive and anxiety disorders. Further inquiry is clearly warranted into the above areas that have potential to evolve into further elucidate the mechanisms of chronic pain and affective disorders, and lead to the development of innovative, safe, and more efficacious neurobiologically-based therapeutic approaches.

Exploratory study of VVZ-149, a novel analgesic molecule, in the affective component of acute postoperative pain after laparoscopic colorectal surgery

STUDY OBJECTIVE

VVZ-149 is a small molecule that inhibits the glycine transporter type 2 and the serotonin receptor 5-hydroxytryptamine 2A. In the present study, we investigated the efficacy and safety of VVZ-149 as a single-use injectable analgesic for treating moderate to severe postoperative pain after colorectal surgery.

DESIGN

Randomized, parallel group, double-blind Phase 2 clinical trial (NCT02489526).

SETTING

3 academic institutions in the United States.

PATIENTS

60 patients undergoing laparoscopic colorectal surgery.

INTERVENTIONS

A continuous 8-h intravenous infusion of VVZ-149 Injections (n = 40) or placebo (n = 20) administered after emergence from anesthesia.

MEASUREMENTS

The outcome measures included pain intensity (PI), opioid consumption via patient-controlled analgesia (PCA), and rescue dosing provided "as needed". Early rescue dosing with opioids postoperatively was associated with preoperative negative affect (anxiety, depression, and pain catastrophizing), enabling it to be used as an indirect measure of the affective component of pain. Efficacy outcomes were compared between treatment groups based on preoperative negative affect and early rescue dosing of opioids.

MAIN RESULTS

Postoperative PI was non-significantly lower in patients receiving VVZ-149 compared to those receiving placebo. The VVZ-149 group had a 34.2% reduction in opioid consumption for 24 h post-dose, along with fewer PCA demands. Somnolence and headache was higher in the intervention group. For patients characterized by high levels of preoperative negative affect, the VVZ-149 group experienced a significant pain reduction and 40% less opioid use compared to the placebo group.

CONCLUSIONS

VVZ-149 resulted in a non-significant reduction of postoperative pain during the first 8 h after surgery. Post hoc analysis indicates that VVZ-149 may benefit patients with negative affect who otherwise have higher postoperative opioid use. REGISTRATION NUMBER: www.clinicaltrials.gov, ID: NCT02489526.

A pilot randomized clinical trial of mindfulness-oriented recovery enhancement as an adjunct to methadone treatment for people with opioid use disorder and chronic pain: Impact on illicit drug use, health, and well-being

BACKGROUND

Chronic pain is highly prevalent among people in methadone maintenance treatment (MMT) for opioid use disorder and is known to be an important contributor to treatment discontinuation and opioid relapse. Mindfulness-Oriented Recovery Enhancement (MORE) is one of the few interventions developed and tested as an integrated treatment to simultaneously address both pain and illicit opioid use; however, this study is the first to evaluate MORE as an adjunct to MMT.

METHODS

Randomized individuals in MMT (N = 30) received MORE plus methadone TAU (n = 15) or methadone TAU, only (n = 15). Participants in the MORE arm received their MMT, as usual, and attended eight, weekly, two-hour MORE groups at their MMT clinics. Participants in the TAU arm received their MMT, as usual, and group or individual counseling, as required by the clinic. TAU counseling consisted of relapse prevention, cognitive-behavioral therapy, and supportive treatment. TAU participants did not receive any mindfulness-based intervention. Participants completed assessments at baseline, post-treatment (i.e., 8-weeks post-baseline), and follow-up (i.e., 16-weeks post-baseline).

RESULTS

Participants in MORE evidenced significantly fewer baseline adjusted days of illicit drug use and significantly lower levels of craving through 16-week follow-up compared to TAU. Also, Participants in MORE reported significantly lower levels of pain, physical and emotional limitations, depression, and anxiety through 16-week follow-up compared to TAU. Conversely, participants in MORE reported significantly higher levels of well-being, vitality, and social functioning through 16-week follow-up compared to TAU.

CONCLUSION

MORE could be an effective adjunct to MMT, and larger trials are warranted.

Valuation system connectivity is correlated with poly-drug use in young adults

Poly-drug consumption contributes to fatal overdose in more than half of all poly-drug users. Analyzing decision-making networks may give insight into the motivations behind poly-drug use. We correlated average functional connectivity of the valuation system (VS), executive control system (ECS) and valuation-control complex (VCC) in a large population sample (n = 992) with drug use behaviour. VS connectivity is correlated with sedative use, ECS connectivity is separately correlated with hallucinogens and opiates. Network connectivity is also correlated with drug use via two-way interactions with other substances including alcohol and tobacco. These preliminary findings can contribute to our understanding of the common combinations of substance co-use and associated neural patterns.

The Effect of Reducing Intravenous Push Opioid Use on Hospital Medicine Patients' Pain Experience during Hospitalization

OBJECTIVE

To determine the efficacy of a program to limit the use of the IV push route for opioids on the experience of pain by inpatients and on associated safety events.

DESIGN

Retrospective cohort study.

SETTING

Two inpatient general medicine floor units at an urban tertiary care academic medical center.

SUBJECTS

4752 inpatient opioid recipients.

METHODS

Patients on one unit were exposed to a multidisciplinary intervention to limit prescription of opioids via the IV push route, with the other unit used as a control unit. The primary study outcome was mean numeric pain score per patient during the hospital stay. Secondary measures included hospital length of stay and post-discharge patient satisfaction. Fidelity measures included percentage of patient population exposed to each opioid administration route and amount of opioid administered per route. Safety measures included patient disposition, transfer to intensive care, and incidence of naloxone administration.

RESULTS

The intervention was successful in decreasing both percentage of patients exposed to IV push opioids and amount of opioid administered via the IV push route, but no associated changes in other study outcomes were identified.

CONCLUSIONS

For treatment of acute pain in medical inpatients, no evidence of benefit or harm was identified in relation to increase or decrease in use of the IV push opioid route.

Intermittent self-administration of fentanyl induces a multifaceted addiction state associated with persistent changes in the orexin system

The orexin (hypocretin) system plays a critical role in motivated drug taking. Cocaine self-administration with the intermittent access (IntA) procedure produces a robust addiction-like state that is orexin-dependent. Here, we sought to determine the role of the orexin system in opioid addiction using IntA self-administration of fentanyl. Different groups of male rats were either given continuous access in 1-h period (short access [ShA]), 6-h period (long access [LgA]), or IntA (5 min of access separated by 25 min of no access for 6 h) to fentanyl for 14 days. IntA produced a greater escalation of fentanyl intake, increased motivation for fentanyl on a behavioral economics task, persistent drug seeking during abstinence, and stronger cue-induced reinstatement compared with rats given ShA or LgA. We found that addiction behaviors induced by IntA to fentanyl were reversed by the orexin-1 receptor antagonist SB-334867. IntA to fentanyl was also associated with a persistent increase in the number of orexin neurons. Together, these results indicate that the IntA model is a useful tool in the study of opioid addiction and that the orexin system is critical for the maintenance of addiction behaviors induced by IntA self-administration of fentanyl.

Characteristics of depressed suicide attempters with remitted substance use disorders

Substance use disorder (SUD) comorbidity in mood disorders increases suicide risk. Suicide attempters with active SUD appear to have distinct characteristics but little is known whether these characteristics persist during remission and if they are related to different aspects of suicidal behavior. In this study, suicide attempters with a DSM mood disorder and remitted SUD (AT+SUD) (N = 135) were compared to those without lifetime SUD (AT-SUD) (N = 219) in terms of demographic, clinical and suicidal behavioral characteristics. Factor analyses were conducted to generate subjective distress and impulsivity/aggression factors - previously identified by our group to predict suicide risk in mood disorders. Associations between these traits and SUD history and suicidal behavior characteristics were then tested. Compared with AT-SUD, AT+SUD were more likely to be male, less educated and to have a Cluster B personality disorder. AT+SUD individuals had greater impulsivity/aggression factor scores, but comparable subjective distress scores. AT+SUD made a greater number of suicide attempts, with higher lethality, despite comparable suicide intent and degree of planning with AT-SUD. Impulsivity/aggression was higher in multiple versus single attempters, but did not correlate with suicide attempt lethality. Among suicide attempters with mood disorders, a history of lifetime SUD was associated with more frequent and more lethal suicide attempts. Among other correlates of lifetime SUD in this sample, impulsive/aggressive traits may explain greater frequency of suicide attempts. The results underscore that persons with mood disorders and lifetime SUD are at particularly high risk of frequent and lethal suicide attempts where more intensive prevention efforts are warranted.

Endocannabinoid signaling in the lateral habenula regulates pain and alcohol consumption

Hyperalgesia, which often occurs in people suffering from alcohol use disorder, may drive excessive drinking and relapse. Emerging evidence suggests that the lateral habenula (LHb) may play a significant role in this condition. Previous research suggests that endocannabinoid signaling (eCBs) is involved in drug addiction and pain, and that the LHb contains core components of the eCBs machinery. We report here our findings in rats subjected to chronic ethanol vapor exposure. We detected a substantial increase in endocannabinoid-related genes, including Mgll and Daglb mRNA levels, as well as monoacylglycerol lipase (MAGL) protein levels, as well as a decrease in Cnr1 mRNA and type-1 cannabinoid receptor (CB1R) protein levels, in the LHb of ethanol-exposed rats. Also, rats withdrawing from ethanol exposure displayed hypersensitivity to mechanical and thermal nociceptive stimuli. Conversely, intra-LHb injection of the MAGL inhibitor JZL184, the fatty acid amide hydrolase inhibitor URB597, or the CB1R agonist WIN55,212-2 produced an analgesic effect, regardless of ethanol or air exposure history, implying that alcohol exposure does not change eCB pain responses. Intra-LHb infusion of the CB1R inverse agonist rimonabant eliminated the analgesic effect of these chemicals. Rimonabant alone elicited hyperalgesia in the air-, but not ethanol-exposed animals. Moreover, intra-LHb JZL184, URB597, or WIN55,212-2 reduced ethanol consumption in both homecages and operant chambers in rats exposed to ethanol vapor but not air. These findings suggest that LHb eCBs play a pivotal role in nociception and facilitating LHb eCBs may attenuate pain in drinkers.

Clinical and psychological factors associated with interdose opioid withdrawal in chronic pain population

BACKGROUND

The DSM-5 diagnostic criteria for Prescription Opioid-Use Disorder (POUD) have undergone some significant changes. One of the most controversial changes has been the elimination of the withdrawal symptoms criterion when opioid use is under appropriate medical supervision. For this reason, the goal of this study was to analyze factors associated with opioid withdrawal in patients with chronic non-cancer pain (CNCP).

METHODS

This cross-sectional descriptive study involved 404 patients who use prescription opioids for long-term treatment (≥90 days) of CNCP. Measures included sociodemographic and clinical characteristics, POUD, withdrawal symptoms, craving, anxiety-depressive symptoms, and pain intensity and interference.

RESULTS

Forty-seven percent (n = 193) of the sample reported moderate-severe withdrawal symptoms, which were associated with lower age, higher daily morphine dose and duration of treatment with opioids, moderate-severe POUD, use of psychotropic drugs, higher anxiety-depressive symptoms, and greater pain intensity and interference (p < .05). Binary logistic regression analysis showed that moderate-severe POUD (OR = 2.82), anxiety (OR = 2.21), depression (OR = 1.81), higher pain interference (OR = 1.05), and longer duration of treatment with opioids were the strongest factors associated with moderate-severe withdrawal symptoms (p < .05).

CONCLUSION

Psychological factors seem to play a key role in the severity of withdrawal symptoms. Since greater intensity of these symptoms increases the risk of developing POUD, knowing the factors associated with withdrawal may be useful in developing preventive psychological interventions.

Pain Sensitivity, Negative Affect, and Alcohol Use Disorder Status: A Moderated Mediation Study of Emotion Dysregulation

Previous work suggests that the association between pain and emotional processes among individuals with alcohol use disorder (AUD) may differ from healthy controls. This study investigates whether pain sensitivity mediates the association between negative affect and emotional dysregulation and whether this association differs across AUD status using moderated mediation. The sample included 165 individuals diagnosed with AUD and 110 healthy controls. Of interest was pain sensitivity, as assessed with the Pain Sensitivity Questionnaire, negative affect, as assessed with the Beck Depression Inventory, and emotional dysregulation, as assessed with the Difficulties in Emotional regulation Scale. Age, biological sex, and current pain severity were included as covariates. The results support a moderated partial mediation model that explained 44% of the variance in emotional dysregulation. The findings indicate that negative affect is related to higher pain sensitivity across groups. Moreover, pain sensitivity partially mediated the association between negative affect and emotional dysregulation, but in opposite directions depending on AUD status. Among healthy controls, greater pain sensitivity was related to better emotional regulation, while greater pain sensitivity led to greater emotional dysregulation among individuals with AUD. The potential parallels in the underlying neurobiological mechanisms of emotionality, pain, and AUD suggest that interventions targeting pain may improve adaptive affect regulation skills, which in turn could reduce negative affect and its effect on pain sensitivity among individuals with AUD.

Factors mediating pain-related risk for opioid use disorder

Pain is a complex experience with far-reaching organismal influences ranging from biological factors to those that are psychological and social. Such influences can serve as pain-related risk factors that represent susceptibilities to opioid use disorder. This review evaluates various pain-related risk factors to form a consensus on those that facilitate opioid abuse. Epidemiological findings represent a high degree of co-occurrence between chronic pain and opioid use disorder that is, in part, driven by an increase in the availability of opioid analgesics and the diversion of their use in a non-medical context. Brain imaging studies in individuals with chronic pain that use/abuse opioids suggest abuse-related mechanisms that are rooted within mesocorticolimbic processing. Preclinical studies suggest that pain states have a limited impact on increasing the rewarding effects of opioids. Indeed, many findings indicate a reduction in the rewarding and reinforcing effects of opioids during pain states. An increase in opioid use may be facilitated by an increase in the availability of opioids and a decrease in access to non-opioid reinforcers that require mobility or social interaction. Moreover, chronic pain and substance abuse conditions are known to impair cognitive function, resulting in deficits in attention and decision making that may promote opioid abuse. A better understanding of pain-related risk factors can improve our knowledge in the development of OUD in persons with pain conditions and can help identify appropriate treatment strategies. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'.

Suicide Risk and Addiction: The Impact of Alcohol and Opioid Use Disorders

Purpose of Review

Suicide is a major public health concern and a leading cause of death in the US. Alcohol and opioid use disorders (AUD/OUD) significantly increase risk for suicidal ideation, attempts, and death, and are the two most frequently implicated substances in suicide risk. We provide a brief overview of shared risk factors and pathways in the pathogenesis of AUD/OUD and suicidal thoughts and behaviors. We also review clinical recommendations on inpatient care, pharmacotherapy, and psychotherapeutic interventions for people with AUD/OUD and co-occurring suicidal ideation and behavior.

Recent Findings

Among people with an underlying vulnerability to risk-taking and impulsive behaviors, chronic alcohol intoxication can increase maladaptive coping behaviors and hinder self-regulation, thereby increasing the risk of suicide. Additionally, chronic opioid use can result in neurobiological changes that lead to increases in negative affective states, jointly contributing to suicide risk and continued opioid use. Despite significantly elevated suicide risk in individuals with AUD/OUD, there is a dearth of research on pharmacological and psychosocial interventions for co-occurring AUD/OUD and suicidal ideation and behavior.

Summary

Further research is needed to understand the effects of alcohol and opioid use on suicide risk, as well as address notable gaps in the literature on psychosocial and pharmacological interventions to lower risk for suicide among individuals with AUD/OUD.

Tolerance to alcohol: A critical yet understudied factor in alcohol addiction

Alcohol tolerance refers to a lower effect of alcohol with repeated exposure. Although alcohol tolerance has been historically included in diagnostic manuals as one of the key criteria for a diagnosis of alcohol use disorder (AUD), understanding its neurobiological mechanisms has been neglected in preclinical studies. In this mini-review, we provide a theoretical framework for alcohol tolerance. We then briefly describe chronic tolerance, followed by a longer discussion of behavioral and neurobiological aspects that underlie rapid tolerance in rodent models. Glutamate/nitric oxide, γ-aminobutyric acid, opioids, serotonin, dopamine, adenosine, cannabinoids, norepinephrine, vasopressin, neuropeptide Y, neurosteroids, and protein kinase C all modulate rapid tolerance. Most studies have evaluated the ability of pharmacological manipulations to block the development of rapid tolerance, but only a few studies have assessed their ability to reverse already established tolerance. Notably, only a few studies analyzed sex differences. Neglected areas of study include the incorporation of a key element of tolerance that involves opponent process-like neuroadaptations. Compared with alcohol drinking models, models of rapid tolerance are relatively shorter in duration and are temporally defined, which make them suitable for combining with a wide range of classic and modern research tools, such as pharmacology, optogenetics, calcium imaging, in vivo electrophysiology, and DREADDs, for in-depth studies of tolerance. We conclude that studies of the neurobiology of alcohol tolerance should be revisited with modern conceptualizations of addiction and modern neurobiological tools. This may contribute to our understanding of AUD and uncover potential targets that can attenuate hazardous alcohol drinking.

Role of VVZ-149, a Novel Analgesic Molecule, in the Affective Component of Pain: Results from an Exploratory Proof-of-Concept Study of Postoperative Pain following Laparoscopic and Robotic-Laparoscopic Gastrectomy

OBJECTIVE

VVZ-149 is a small molecule that both inhibits the glycine transporter type 2 and the serotonin receptor 5 hydroxytryptamine 2 A. In a randomized, parallel-group, and double-blind trial (NCT02844725), we investigated the analgesic efficacy and safety of VVZ-149 Injections, which is under clinical development as a single-use injectable product for treating moderate to severe postoperative pain.

METHODS

Sixty patients undergoing laparoscopic and robotic-laparoscopic gastrectomy were randomly assigned to receive a 10-hour intravenous infusion of VVZ-149 Injections or placebo, initiated approximately 1 hour before completion of surgical suturing. Major outcomes included pain intensity and opioid consumption via patient-controlled analgesia and rescue analgesia provided "as needed." The treatment efficacy of VVZ-149 was further examined in a subpopulation requiring early rescue medication, previously associated with the presence of high levels of preoperative negative affect in a prior Phase 2 study (NCT02489526).

RESULTS

Pain intensity was lower in the VVZ-149 (n = 30) than the placebo group (n = 29), reaching statistical significance at 4 hours post-emergence (P < .05), with a 29.5% reduction in opioid consumption for 24 hours and fewer demands for patient-controlled analgesia. In the rescued subgroup, VVZ-149 further reduced pain intensity (P < .05) with 32.6% less opioid consumption for 24 hours compared to placebo patients.

CONCLUSIONS

VVZ-149 demonstrated effective analgesia with reduced postoperative pain and opioid requirements. Consistent with the results from the previous Phase 2 study, patients with early rescue requirement had greater benefit from VVZ-149, supporting the hypothesis that VVZ-149 may alleviate the affective component of pain and mitigate excessive use of opioids postoperatively.

The temporal dynamics of emotion dysregulation in prescription opioid misuse

BACKGROUND

Opioid misuse is theorized to compromise the capacity to regulate positive and negative emotions. Yet, the temporal dynamics of emotion dysregulation in opioid misuse remain unclear.

METHODS

Patients with chronic pain on long-term opioid therapy (N = 71) participated in an experiment in which they completed an event-related emotion regulation task while heart rate (HR) and galvanic skin responses (GSR) were recorded over a 5 s emotional picture viewing period. Participants were asked to passively view the images or to proactively regulate their emotional responses via reappraisal (i.e., negative emotion regulation) and savoring (i.e., positive emotion regulation) strategies. Using a validated cutpoint on the Current Opioid Misuse Measure, participants were classified as medication-adherent or opioid misusers.

RESULTS

Medication-adherent patients were able to significantly decrease GSR and HR during negative emotion regulation, whereas opioid misusers exhibited contradictory increases in these autonomic parameters during negative emotion regulation. Furthermore, GSR during positive emotion regulation increased for non-misusers, whereas GSR during positive emotion regulation did not increase for misusers. These autonomic differences, which remained significant even after controlling for a range of covariates, were evident within 1 s of emotional stimulus presentation but reached their maxima 3-4 s later.

CONCLUSIONS

Opioid misuse among people with chronic pain is associated with emotion dysregulation that occurs within the first few seconds of an emotional provocation. Treatments for opioid misuse should aim to remediate these deficits in emotion regulation.

A mu-opioid feedback model of human social behavior

Since the discovery of pain relieving and rewarding properties of opiates such as morphine or heroin, the human mu-opioid system has been a target for medical research on pain processing and addiction. Indeed, pain and pleasure act mutually inhibitory on each other and the mu-opioid system has been suggested as an underlying common neurobiological mechanism. Recently, research interest extended the role of the endogenous mu-opioid system beyond the hedonic value of pain and pleasure towards human social-emotional behavior. Here we propose a mu-opioid feedback model of social behavior. This model is based upon recent findings of opioid modulation of human social learning, bonding and empathy in relation to affiliative and protective tendencies. Fundamental to the model is that the mu-opioid system reinforces socially affiliative or protective behavior in response to positive and negative social experiences with long-term consequences for social behavior and health. The functional implications for stress, anxiety, depression and attachment behaviors are discussed.

Complex Persistent Opioid Dependence with Long-term Opioids: a Gray Area That Needs Definition, Better Understanding, Treatment Guidance, and Policy Changes

The multitude of treatments available for tens of millions of US adults with moderate/severe chronic pain have limited efficacy. Long-term opioid therapy (LTOT) is a widely available option for controlling pain among patients with chronic pain refractory to other treatments. The recent recognition of LTOT inefficacy and complications has led to more frequent opioid tapering, which in turn has revealed its own set of complications. The occurrence of the same set of symptoms-worsening pain, declining function, and clinical instability-in contrasting contexts of LTOT ineffectiveness and opioid tapering has led to increasing recognition of the utility of complex persistent opioid dependence (CPOD), a clinically distinct but biologically similar state compared with opioid use disorder as an explanatory diagnosis/heuristic. Recent guidelines for LTOT tapering have incorporated buprenorphine treatment based on CPOD concepts as a recommended treatment for problems due to opioid tapering with limited supportive evidence. The increasing utilization of buprenorphine for both LTOT ineffectiveness and opioid tapering problems raises the urgent need for a review of the clinical definition, mechanisms, and treatment of CPOD and pertinent policies. In this manuscript, we discuss various issues related to CPOD that requires further clarification through research and policy development.

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.