The risk for problematic opioid use in chronic pain: What can we learn from studies of pain and reward?

Sleep Disruption Moderates the Daily Dynamics of Affect and Pain in Sickle Cell Disease

Persons with sickle cell disease (SCD) often experience pain that can interfere with quality of life and daily activities. Pain can modulated by affect and sleep continuity; however, few studies have explored how these factors complementarily influence pain in adults with SCD. The study aims were to investigate 1) whether pain levels were heightened on days characterized by low positive affect and high negative affect, and 2) whether the relationship between affect and pain was intensified following nights of disrupted sleep. Adults with SCD (N = 25) completed ecological momentary assessments and daily sleep diaries. Mixed models were used to analyze the main and interactive effects of daily affect (positive affect and negative affect) and sleep disruption (wake after sleep onset and frequency of awakenings) on both daily average pain and daily maximum pain. Results suggested that daily average pain and maximum pain tended to be higher on days of low positive affect and high negative affect. Furthermore, the frequency of nocturnal awakenings moderated the relationship between positive affect and pain. On days where there were higher frequencies of nocturnal awakenings, low positive affect was associated with both average and maximum pain; however, this association was not observed with lower frequencies of nocturnal awakenings. The association between negative affect and maximum pain was also stronger at higher levels of awakenings. Results highlight the relevance of adjunctive interventions that target affect among populations with SCD and further suggest that sleep continuity may further facilitate these interventions, highlighting the importance of multimodal treatments. PERSPECTIVE: This study examined the effects of affect and sleep on pain among adults with sickle cell disease (SCD). Higher pain occurred on days of low positive affect and high negative affect, particularly following nights of more frequent awakenings. These findings emphasize the importance of addressing affect and sleep in SCD treatment.

A Conceptual Analysis of Opioid Use Disorder in Chronic Noncancer Pain Using Rodger's Evolutionary Approach

OBJECTIVE

This study aims to examine the complex nature of opioid use disorder (OUD) in chronic noncancer pain (CNCP) by exploring its antecedents, attributes, consequences, and interrelated concepts.

DESIGN

A systematic literature review was conducted to gather relevant studies published between 2015 and 2022, utilizing the CINAHL, MEDLINE, PsycINFO, and PubMed databases.

DATA SOURCES

The selected databases provided a comprehensive range of articles related to OUD in CNCP, ensuring a comprehensive topic analysis.

METHODS

Twenty-two articles meeting the inclusion criteria were included in the analysis. These articles were critically reviewed and analyzed to identify key themes and concepts related to OUD in CNCP.

RESULTS

The findings of this study shed light on the multifaceted aspects of OUD in CNCP, including its antecedents, such as goals of physical function improvement, prescription of opioids for CNCP, social influences, and mental health dynamics. The attributes of OUD in CNCP were identified as chronic pain, noncancer pain, opioid use, misuse, and abuse. OUD's consequences in CNCP include impaired functioning, increased health risks, psychological distress, social challenges, and economic burden.

CONCLUSION

Understanding the complexity of OUD in CNCP is crucial for improving patient outcomes. Collaborative efforts among healthcare systems, regulatory bodies, and professional organizations are needed to develop policies promoting safe and effective pain management while mitigating risks associated with opioid use in CNCP.

IMPLICATIONS FOR PRACTICE

Implementing policy recommendations derived from this study enhances care and outcomes for individuals with CNCP. By addressing complex issues of OUD in CNCP and adopting evidence-based practices, healthcare providers can optimize pain management and promote well-being in CNCP patients.

Altered Reward Processing and Sex Differences in Chronic Pain

Chronic pain and reward processing are understood to be reciprocally related to one another. Previous studies of reward processing in chronic pain patients have reported incongruent findings. While several factors likely contribute to these disparate findings, these previous studies did not stratify their analyses by sex-a factor previously shown to robustly impact reward-related responses. Thus, we examined sex as a factor of interest in level of striatal activation during anticipation of monetary incentives among patients with chronic non-specific back pain and healthy controls (HC). This study utilized functional magnetic resonance imaging during a monetary incentive delay task to evaluate reward and loss responsivity in the striatum among males and females with and without chronic pain (N = 90). Group, sex, and group-by-sex interactions were analyzed via repeated measures analysis of variance. Among HC, males exhibited significantly greater blood oxygen level dependent (BOLD) signal in the striatum during reward anticipation, particularly during large reward trials. By contrast, no significant sex differences were observed among patients. A significant group-by-sex interaction was also observed, revealing diminished BOLD responses among males with chronic pain relative to control males. These results provide novel evidence of sex-specific reductions in anticipatory responses to reward in patients with chronic pain. Altered striatal reward responsivity among males, but not females, suggests that the reward systems of males and females are uniquely disrupted by chronic pain, and highlights the value of including sex as a factor of interest in future studies of reward responsivity in the context of persistent pain.

Buprenorphine Microdosing for the Pain and Palliative Care Clinician

Buprenorphine (BUP) can be a safe and effective alternative to traditional opioids for many patients with chronic pain. For patients on higher doses of opioids, rotation to BUP is complicated by the requirement of an opioid-free interval or withdrawal during the transition. Microdosing inductions, in which BUP is gradually titrated, while full agonist opioids are continued, are a viable alternative to traditional inductions. The objective of this article is to review the current literature on BUP microdosing induction, with a focus on patients using opioids for pain. A literature review of the PubMed database was performed in the United States on articles published from inception to May 2021. A total of 34 publications were included. The most commonly utilized microdosing strategy involved administering divided doses of sublingual (SL) products marketed for opioid use disorder treatment, with 25 (73.5%) articles reporting use of partial SL tablets or films (ranging from 1/8 to 1/2 of a 2 mg product) at some point during the induction. Transdermal patches, low-dose SL BUP available in Europe, intravenous BUP, and buccal BUP have also been used. Beyond the products used, the speed of the microinduction, setting, final BUP dosing, and management of concomitant full agonists vary widely in the literature. Microdosing regimens should be individualized based on local guidelines and patient-specific factors. Further studies comparing the safety and efficacy of different protocols are warranted.

Rotigotine-loaded microspheres exerts the antinociceptive effect via central dopaminergic system

Rotigotine-loaded microspheres (RoMS), a sustained-release formulation with a continuous release of rotigotine for more than 7 days in vivo, have been conducted a clinical trial for the treatment of Parkinson's disease (PD). Previous work from our laboratory showed that RoMS exerted an antinociceptive effect in rat models of inflammatory pain. The purpose of this study was to investigate the mechanisms of action underlying the antinociceptive effect of RoMS. A rat model of inflammatory pain was prepared by an intraplantar injection of carrageenan. The hot plate test and the Randall-Selitto test were used to evaluate the effect of domperidone (selective D2 receptor antagonist), D2D3 shRNA, and naloxone (nonselective opioid receptor antagonist) on RoMS-mediated antinociceptive efficacy. The expressions of D2 and D3 receptors in the striatum and periaqueductal gray were measured by Western blotting. Intracerebroventricular injection of domperidone abated the antinociceptive effect of RoMS. However, intraperitoneal injection of domperidone had no significant effect on the antinociceptive action of RoMS. Intracerebroventricular injection with D2D3 shRNA significantly attenuated the expressions of D2 and D3 receptors in the striatum and the periaqueductal gray. D2 and D3 receptors silence significantly weakened RoMS-mediated antinociceptive effect. Intracerebroventricular injection of naloxone also alleviated the antinociceptive effect of RoMS. The results suggest that RoMS-mediated antinociceptive efficacy is associated with activating central dopamine D2 and D3 receptors. Opioid receptors play a role in the antinociceptive effect of RoMS.

Factors Associated with Knee Arthroplasty in a Knee Osteoarthritis Patient Cohort Treated with Intra-articular Injections of Hylan G-F 20

Hylan G-F 20 viscosupplementation can be used to treat knee osteoarthritis pain. This study evaluated time to knee arthroplasty (KA), KA risk factors, and health care resource utilization in patients aged ≥18 years with claims in the Optum Clinformatics Data Mart database (2006-2016) for knee osteoarthritis treated with at least one course of hylan G-F 20. Kaplan-Meier analysis estimated KA risk from osteoarthritis diagnosis and first hylan G-F 20 treatment. KA risk factors were determined using multivariate Cox regression. Among 62,033 patients treated with hylan G-F 20 and/or hylan G-F 20 single intra-articular injection, 60 to 64% did not undergo KA 8 years following first injection. KA risk factors from time of osteoarthritis diagnosis and first hylan G-F 20 treatment were similar: increased age, fewer comorbidities, fewer hylan G-F 20 treatments, female sex, and no ultrasound/fluoroscopy for injection guidance. Patients who underwent KA versus those who did not had more office visits and claims for opioids, nonsteroidal anti-inflammatory drugs, and physical therapy. Patients less likely to undergo KA were younger (<40 years), had more comorbidities, received more courses of hylan G-F 20, were males, or received ultrasound/fluoroscopic injection guidance. Patients who did not receive KA versus those who did used fewer health care resources.

Perception of repeated pain relief with controllable and uncontrollable pain

BACKGROUND

The ultimate goal of pain research is to provide effective routes for pain relief. Nevertheless, the perception pain relief as a change in pain intensity and un-/pleasantness has only been rarely investigated. It has been demonstrated that pain relief has rewarding and reinforcing properties, but it remains unknown whether the perception of pain relief changes when pain reductions occur repeatedly. Further, it remains an open question whether the perception of pain relief depends on the controllability of the preceding pain.

METHODS

In this study, healthy volunteers (N = 38) received five cycles of painful heat stimulation and reduction of this stimulation to a non-painful warm stimulation once in a condition with control of the stimulation and once without control. Participants rated perceived intensity and un-/pleasantness on visual analogue scales during the heat stimulation and immediately after its reduction.

RESULTS

Results showed that perceived pain relief, estimated by the difference in ratings during ongoing heat stimulation and after its reduction, increased with repetitions. However, this increase levelled off after two to four repetitions. Further, perceived pain relief was larger in the condition without control compared to the condition with control.

CONCLUSION

The perception of pain relief can be modulated similar to the perception of pain by stimulus characteristics and psychological factors. Mechanistic knowledge about such modulating factors is important, because they can determine, e.g., the amount of requested pain killers in clinical settings and the efficacy of pain relief as a reinforcing stimulus.

SIGNIFICANCE

When in pain, pain relief can become an all-dominate goal. The perception of such pain relief can vary depending on external and internal characteristics and thus modulate, e.g., requests for pain killers in clinical settings. Here, we show that perceived intensity and pleasantness of pain relief changes with repetitions and whether the preceding pain is perceived as uncontrollable. Such mechanistic knowledge needs to be considered to maximize the effects of pain relief as a rewarding and reinforcing stimulus.

Reward processing as a common diathesis for chronic pain and depression

Pain disorders and psychiatric illness are strongly comorbid, particularly in the context of Major Depressive Disorder (MDD). While these disorders account for a significant amount of global disability, the mechanisms of their overlap remain unclear. Understanding these mechanisms is of vital importance to developing prevention strategies and interventions that target both disorders. Of note, brain reward processing may be relevant to explaining how the comorbidity arises, given pain disorders and MDD can result in maladaptive reward responsivity that limits reward learning, appetitive approach behaviours and consummatory response. In this review, we discuss this research and explore the possibility of reward processing deficits as a common diathesis to explain the manifestation of pain disorders and MDD. Specifically, we hypothesize that contextual physical or psychological events (e.g. surgery, divorce) in the presence of a reward impairment diathesis worsens symptoms and results in a negative feedback loop that increases the chronicity and probability of developing the other disorder. We also highlight the implications for treatment and provide a framework for future research.

Peripheral nerve injury promotes morphine-seeking behavior in rats during extinction

Chronic neuropathic pain and prescription opioid abuse represent highly interconnected societal problems. We used a rat model of spared nerve injury (SNI) and an intravenous drug self-administration paradigm to investigate the impact of a neuropathic pain state on morphine-seeking behavior in extinction (i.e. when morphine is withheld). SNI, sham-operated and naive groups exhibited similar levels of active lever presses for morphine infusions on a fixed ratio 1 (FR1) schedule. Self-administration of morphine, but not vehicle, attenuated nerve injury-induced mechanical allodynia in SNI rats. Under these same conditions, mechanical paw withdrawal thresholds in sham-operated and naive groups were largely unaltered. However, SNI rats showed higher levels of morphine-seeking behavior compared to sham-operated or naïve groups in extinction (i.e. when vehicle was substituted for morphine). Interestingly, the perseveration of morphine-seeking behavior observed during extinction was only present in the SNI group despite the fact that all groups had a similar history of morphine self-administration intake. Our results suggest that different motivational states associated with neuropathic pain promote morphine-seeking behavior in extinction. Drug self-administration paradigms may be useful for evaluating analgesic efficacy and motivational properties associated with opioid reinforcers in pathological pain states.

Ambulatory Assessment Methods to Examine Momentary State-Based Predictors of Opioid Use Behaviors

Purpose of Review

Addiction scientists have begun using ambulatory assessment methods—including ecological momentary assessment (EMA), experience sampling, and daily diaries—to collect real-time or near-real-time reports of participants’ internal states in their natural environments. The goal of this short review is to synthesize EMA findings from our research group, which has studied several hundred outpatients during treatment for opioid-use disorder (OUD). (We cite pertinent findings from other groups, but have not tried to be comprehensive.) One of our main goals in using EMA is to examine momentary changes in internal states that proximally predict, or concurrently mark, events such as lapses to opioid use.

Recent Findings

We summarize findings evaluating several classes of momentary markers or predictors (craving, stress, negative and positive moods, and physical pain/discomfort) of lapses and other states/behaviors. Craving and some negatively valenced mood states are concurrently and prospectively associated with lapses to opioid use during treatment. Craving is also concurrently and prospectively associated with momentary changes in stress and mood. Convincing evidence has not yet emerged for stress as a robust redictor of lapse to opioid use; it appears to be contributory, but neither necessary nor sufficient.

Summary

Ambulatory assessment can capture changes in internal states and drug-related behaviors in situ and at high temporal resolution. We recommend research strategies that may increase the clinical and prognostic utility of ambulatory assessment, including denser sampling (i.e., more assessments per day) and more attention to heterogeneity across people and across populations.

Mental Pain as a Transdiagnostic Patient-Reported Outcome Measure

Patient-reported outcomes (PROs) refer to any report coming directly from patients about how they function or feel in relation to a health condition or its therapy. PROs have been applied in medicine for the assessment of the impact of clinical phenomena. Self-report scales and procedures for assessing physical pain in adults have been developed and used in clinical trials. However, insufficient attention has been dedicated to the assessment of mental pain. The aim of this paper is to outline the implications that assessment of mental pain may entail in psychiatry and medicine, with particular reference to a clinimetric index. A simple 10-item self-rating questionnaire, the Mental Pain Questionnaire (MPQ), encompasses the specific clinical features of mental pain and shows good clinimetric properties (i.e., sensitivity, discriminant and incremental validity). The preliminary data suggest that the MPQ may qualify as a PRO measure to be included in clinical trials. Assessment of mental pain may have important clinical implications in intervention research, both in psychopharmacology and psychotherapy. The transdiagnostic features of mental pain are supported by its association with a number of psychiatric disorders, such as depression, anxiety, eating disorders, as well as borderline personality disorder. Further, addressing mental pain may be an important pathway to prevent and diminish the opioid epidemic. The data summarized here indicate that mental pain can be incorporated into current psychiatric assessment and included as a PRO measure in treatment outcome studies.

A Biopsychosocial Overview of the Opioid Crisis: Considering Nutrition and Gastrointestinal Health

The opioid crisis has reached epidemic proportions in the United States with rising overdose death rates. Identifying the underlying factors that contribute to addiction vulnerability may lead to more effective prevention strategies. Supply side environmental factors are a major contributing component. Psychosocial factors such as stress, trauma, and adverse childhood experiences have been linked to emotional pain leading to self-medication. Genetic and epigenetic factors associated with brain reward pathways and impulsivity are known predictors of addiction vulnerability. This review attempts to present a biopsychosocial approach that connects various social and biological theories related to the addiction crisis. The emerging role of nutrition therapy with an emphasis on gastrointestinal health in the treatment of opioid use disorder is presented. The biopsychosocial model integrates concepts from several disciplines, emphasizing multicausality rather than a reductionist approach. Potential solutions at multiple levels are presented, considering individual as well as population health. This single cohesive framework is based on the interdependency of the entire system, identifying risk and protective factors that may influence substance-seeking behavior. Nutrition should be included as one facet of a multidisciplinary approach toward improved recovery outcomes. Cross-disciplinary collaborative efforts, new ideas, and fiscal resources will be critical to address the epidemic.

D2-like receptor agonist synergizes the μ-opioid agonist spinal antinociception in nociceptive, inflammatory and neuropathic models of pain in the rat

Opioids are potent analgesic drugs, but their use has been limited due to their side effects. Antinociceptive effects of D2-like receptor agonists such as quinpirole have been shown at the spinal cord level; however, their efficacy is not as high as that of opioids. Dopaminergic agonists are long-prescribed and well-tolerated drugs that have been useful to treat clinically and experimentally painful conditions. Because current pain treatments are not completely effective, the aim of this work was to determine if a D2-like receptor agonist improves the antinociceptive effects of a μ-opioid receptor agonist. Drugs were intrathecally administered in adult rats; mechanonociceptive and thermonociceptive tests were carried out. Intraplantar injection of complete Freund's adjuvant (CFA) and sciatic loose ligation (SLL) were used for inflammatory and neuropathic models of pain, respectively. In intact animals, D-Ala2, N-MePhe4, Gly-ol-enkephalin (DAMGO; a µ-opioid receptor agonist) increased the paw withdrawal latencies (PWL) in thermal and mechanical nociceptive tests in a dose-dependent manner. Quinpirole (D2-like receptor agonist) increased PWL only in mechanonociception. In the presence of quinpirole (1 nmol), the ED₅₀ of the mechanical antinociceptive effect of DAMGO was significantly decreased (8-fold). Coadministration of 1 nmol quinpirole and 30 pmol DAMGO completely reversed hyperalgesia in the CFA model, whereas 100 pmol DAMGO plus 1 nmol quinpirole reversed the allodynia in the SLL model. This work offers evidence about a synergistic antinociceptive effect between opioidergic and dopaminergic drugs. This combination may relieve painful conditions resistant to conventional treatments, and it may reduce the adverse effects of chronic opioid administration.

Associations Between Adolescent Chronic Pain and Prescription Opioid Misuse in Adulthood

Prescription opioid misuse is a serious public health concern, yet antecedent factors are poorly described. Using data from the National Longitudinal Study of Adolescent to Adult Health (N = 14,784), we examined the longitudinal relationship between a history of adolescent chronic pain and the odds of misusing prescription opioids in adulthood. The primary predictor variable was chronic pain status during adolescence. The primary outcome variables were prescription opioid misuse during early adulthood and adulthood. Multivariate models controlled for known risk factors of opioid misuse, including sociodemographics (sex, race, and ethnicity), adolescent mental health symptoms (anxiety, depression), adolescent self-reported physical health status, adolescent substance use/abuse, childhood trauma, and adult legitimate opioid use. We found that adults with a history of adolescent chronic pain were more likely to misuse opioids than those without history of chronic pain, even after controlling for other known risk factors. Further, we found that among individuals with history of adolescent chronic pain that race (white), other substance use, and exposure to trauma were risk factors for later opioid misuse. Longitudinal associations between adolescent chronic pain and subsequent adult prescription opioid misuse highlight the need for early targeted screening and prevention efforts that may reduce later opioid misuse. Perspective: Using a large, nationally representative sample, we found that chronic pain during adolescence was an independent risk factor for opioid misuse in adulthood, over and above other known risk factors. Furthermore, among those individuals with adolescent chronic pain, substance use, exposure to trauma, and race were associated with opioid misuse.

Pain Therapy Guided by Purpose and Perspective in Light of the Opioid Epidemic

Prescription opioid misuse is an ongoing and escalating epidemic. Although these pharmacological agents are highly effective analgesics prescribed for different types of pain, opioids also induce euphoria, leading to increasing diversion and misuse. Opioid use and related mortalities have developed in spite of initial claims that OxyContin, one of the first opioids prescribed in the USA, was not addictive in the presence of pain. These claims allayed the fears of clinicians and contributed to an increase in the number of prescriptions, quantity of drugs manufactured, and the unforeseen diversion of these drugs for non-medical uses. Understanding the history of opioid drug development, the widespread marketing campaign for opioids, the immense financial incentive behind the treatment of pain, and vulnerable socioeconomic and physical demographics for opioid misuse give perspective on the current epidemic as an American-born problem that has expanded to global significance. In light of the current worldwide opioid epidemic, it is imperative that novel opioids are developed to treat pain without inducing the euphoria that fosters physical dependence and addiction. We describe insights from preclinical findings on the properties of opioid drugs that offer insights into improving abuse-deterrent formulations. One finding is that the ability of some agonists to activate one pathway over another, or agonist bias, can predict whether several novel opioid compounds bear promise in treating pain without causing reward among other off-target effects. In addition, we outline how the pharmacokinetic profile of each opioid contributes to their potential for misuse and discuss the emergence of mixed agonists as a promising pipeline of opioid-based analgesics. These insights from preclinical findings can be used to more effectively identify opioids that treat pain without causing physical dependence and subsequent opioid abuse.