Chronic pain and opioid misuse: a review of reviews

Spinal bromodomain-containing protein 4 contributes to neuropathic pain induced by HIV glycoprotein 120 with morphine in rats

The symptoms of HIV-sensory neuropathy are dominated by neuropathic pain. Recent data show that repeated use of opiates enhances the chronic pain states in HIV patients. Limited attention has so far been devoted to exploring the exact pathogenesis of HIV painful disorder and opiate abuse in vivo, for which there is no effective treatment. Bromodomain-containing protein 4 (Brd4) is a member of the bromodomain and extraterminal domain protein (BET) family and functions as a chromatin 'reader' that binds acetylated lysines in histones in brain neurons to mediate the transcriptional regulation underlying learning and memory. Here, we established a neuropathic pain model of interaction of intrathecal HIV envelope glycoprotein 120 (gp120) and chronic morphine in rats. The combination of gp120 and morphine (gp120/M, for 5 days) induced persistent mechanical allodynia compared with either gp120 or morphine alone. Mechanical allodynia reached the lowest values at day 10 from gp120/M application, beginning to recover from day 21. In the model, gp120/M induced overexpression of Brd4 mRNA and protein at day 10 using RT-qPCR and western blots, respectively. Immunohistochemical studies showed that Brd4 at day 10 was expressed in the neurons of spinal cord dorsal horn. BET inhibitor I-BET762 dose-dependently increased the mechanical threshold in the gp120/M pain state. The present study provides preclinical evidence for treating HIV neuropathic pain with opioids using the BET inhibitor.

Withdrawal symptoms predict prescription opioid dependence in chronic pain patients

BACKGROUND

The last version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) includes substantial changes for prescription opioid-use disorder (POUD). After its removal as a criterion, the goal of this study was to estimate the prevalence of withdrawal symptoms in long-term users of prescription opioids and its association with the new DSM-5 POUD classification.

METHODS

Data were collected from 215 long-term consumers of opioid medication who were chronic non-cancer pain patients. Participants completed sociodemographic, Adjective Rating Scale for Withdrawal (ARSW), opioid treatment characteristics, POUD criteria (DSM-5), and pain intensity measurements.

RESULTS

26.6% of the participants were classified with moderate to severe POUD. Higher intensity of withdrawal symptoms was found in patients with moderate/severe POUD, younger age, and higher pain intensity (p < .01). Anxiolytics (p < .01) and antidepressants use (p < .05) and percentage of smokers (p < .05) were significantly higher in patients with severe withdrawal. Logistic regression analyses suggested moderate [odds ratio (OR) = 3.25] and severe (OR = 10.52) withdrawal as the strongest predictor of POUD. Age, anxiolytics use, and smoking were also associated with POUD, but multilevel analysis showed that these variables do not moderate the association between withdrawal intensity and POUD.

CONCLUSION

Escalation of withdrawal intensity during opioid treatment can be used to identify patients with POUD. Further studies are needed to assess the clinical implications of these findings during long-term opioid therapy for chronic pain.

Prevalence and Correlates of Loss of Control Eating among Adults Presenting for Methadone Maintenance Treatment

BACKGROUND

Research suggests that substance use disorders and disordered eating are often comorbid. In light of the ongoing opioid epidemic, the purpose of the current study was to understand the prevalence and health-related correlates of loss of control (LOC) eating in adults seeking methadone maintenance treatment primarily for addiction to heroin and/or painkillers.

METHODS

Participants were 447 adults surveyed at presentation for methadone maintenance treatment who responded to survey items on LOC eating. Descriptive statistics were used to investigate the prevalence of engaging in LOC eating in the past 2 weeks. Chi-square tests, t tests, and analyses of covariance were used to compare individuals with (LOC+; n = 164) and without (LOC-; n = 283) recent LOC eating on psychosocial, pain-related, and weight-related characteristics.

RESULTS

Approximately one third of respondents endorsed LOC eating in the past 2 weeks. These participants reported greater affective symptoms, interpersonal dysfunction, pain intensity, and pain interference than the LOC- group (Cohen's d effect size range = .24-.94). LOC+ was also more likely to have engaged in recent illicit drug use and to report having concurrent overweight/obesity (φ effect size range = .09-.10).

CONCLUSION

The prevalence of LOC eating in adults seeking methadone maintenance treatment was more than triple what has been reported in previous studies using community samples. Given its associations with other health-related variables, the presence of LOC eating may be a marker for more severe psychopathology in individuals seeking methadone maintenance treatment. Future research is needed to understand mechanisms explaining this comorbidity and to develop novel ways to prevent and treat their co-occurrence.

Engaging Integrated Health Teams to Decrease the Risk of Controlled Substance Use for Individuals With Serious Mental Illness

The United States is facing an opioid epidemic that is virulent in its lethality and includes morbidity and mortality related to prescription opioids. Overuse of another class of drugs- benzodiazepines-has received less media attention, but also poses the threat of tolerance, dependence, and death, especially in combination with opioids or alcohol. These negative outcomes are not distributed evenly over the population but are especially prevalent in vulnerable populations. One such vulnerable population comprises individuals with serious mental illness. Professionals who serve this population are challenged by an often-fragmented health care system to collaborate with patients and other professionals to reduce risks and improve outcomes. This article examines strategies for addressing risks associated with the use of benzodiazepines and opioids in this population within the context of an integrated interprofessional team. Recommendations include (a) building consensus on the team, (b) providing education for all stakeholders, and (c) enhancing care coordination and patient access to effective treatments. [Journal of Psychosocial Nursing and Mental Health Services, 56(12), 11-15.].

Addressing Opioid-Related Chemical Coping in Long-Term Opioid Therapy for Chronic Noncancer Pain: A Multicenter, Observational, Cross-Sectional Study

Opioid consumption has increased worldwide, which carries the risk of opioid use disorder (OUD). However, the literature on OUD and opioid-related chemical coping (OrCC) in chronic noncancer pain (CNCP) is heterogeneous, with most studies conducted in the United States. We performed a multicenter, observational, cross-sectional study to address OrCC in long-term opioid therapy (LtOT) for CNCP in South Korea. The objectives were to determine the frequency and predictors of OrCC. We included 258 patients. Among them, fifty-five (21%) patients showed OrCC. The sample had high pain catastrophizing (≥30 points; 66%), moderate-severe insomnia (≥15 points; 63%), low resilience (68 points), and high suicidal ideation (67%). OrCC patients had greater pain interference (85.18% vs. 58.28%, p = 0.017) and lower satisfaction with the LtOT (56.4% vs. 78.3%, p = 0.002). In multivariable analysis, alcohol abuse (OR = 6.84, p = 0.001), prescription drugs abuse (OR = 19.32, p = 0.016), functional pain (OR = 12.96, p < 0.001), head and neck pain (OR = 2.48, p = 0.039), MEDD (morphine equivalent daily dose) ≥ 200 mg/day (OR = 3.48, p = 0.006), and ongoing litigation (OR = 2.33, p = 0.047) were significant predictors of OrCC. In conclusion, the break-out of OrCC in CNCP in South Korea was comparable to those in countries with high opioid consumption, such as the United States, regardless of the country's opioid consumption rate.

Drug Interactions With New Synthetic Opioids

Fentanyl, fentanyl analogs, and other new synthetic opioids (NSO) have burst onto the illegal drug market as new psychoactive substances (NPS). They are often sold as heroin to unsuspecting users and produce euphoria through their agonist action on μ- opioid receptors. Their high consumption, often combined with other substances, has led to multiple intoxications during recent years. In some countries, such as the United States, the consumption of opioids, whether for medical or recreational purposes, has become epidemic and is considered a public health problem. Fentanyl analogs are more potent than fentanyl which in turn is 50 times more potent than morphine. Furthermore, some fentanyl analogs have longer duration of action and therefore interactions with other substances and medicines can be more serious. This review is focused on the potentially most frequent interactions of opioid NPS taking into account the drugs present in the reported cases of poly-intoxication, including other illegal drugs of abuse and medication. Substances involved are mainly antidepressants, antihistamines, antipsychotics, benzodiazepines, analgesics, anesthetics, psychostimulants, other opioids, alcohol, and illegal drugs of abuse. The interactions can be produced due to pharmacokinetic and pharmacodynamic mechanisms. Naloxone can be used as an antidote, although required doses might be higher than for traditional opioid intoxications. It is crucial that doctors who habitually prescribe opioids, which are often misused by patients and NPS users, be aware of designer opioids' potentially life-threatening drug-drug interactions in order to prevent new cases of intoxication.

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 as a risk factor for substance use: a qualitative study of people who use drugs in British Columbia, Canada

Background

People who use drugs have a significantly higher prevalence of chronic non-cancer pain compared to the general population, yet little is known about how various policy, economic, physical, and social environments may serve as risk or protective factors in the context of concurrent pain and substance use. Therefore, this study sought to explore perspectives, risks, and harms associated with pain among people who use drugs.

Methods

Thirteen focus group interviews were held across British Columbia, Canada, from July to September 2015. In total, 83 people who had lived experience with substance use participated in the study. Using an interpretive description approach, themes were conceptualized according to the Rhodes’ Risk Environment and patient-centered care frameworks.

Results

Participants described how their experiences with inadequately managed pain in various policy, economic, physical, and social environments reinforced marginalization, such as restrictive policies, economic vulnerability, lack of access to socio-physical support systems, stigma from health professionals, and denial of pain medication leading to risky self-medication. Principles of patient-centered care were often not upheld, from a lack of recognition of patients as experts in understanding their unique pain needs and experiences, to an absence of shared power and decision-making, which often resulted in distrust of the patient-provider relationship.

Conclusions

Various risk environments and non-patient-centered interactions may contribute to an array of health and social harms in the context of inadequately managed pain among people who use drugs.

A medial prefrontal cortex-nucleus acumens corticotropin-releasing factor circuitry for neuropathic pain-increased susceptibility to opioid reward

Recent studies have shown that persistent pain facilitates the response to morphine reward. However, the circuit mechanism underlying this process remains ambiguous. In this study, using chronic constriction injury (CCI) of the sciatic nerve in mice, we found that persistent neuropathic pain reduced the minimum number of morphine conditioning sessions required to induce conditioned place preference (CPP) behavior. This dose of morphine had no effect on the pain threshold. In the medial prefrontal cortex (mPFC), which is involved in both pain and emotion processing, corticotropin-releasing factor (CRF) expressing neuronal activity was increased in CCI mice. Chemogenetic inhibition of mPFC CRF neurons reversed CCI-induced morphine CPP facilitation. Furthermore, the nucleus acumens (NAc) received mPFC CRF functional projections that exerted excitatory effects on NAc neurons. Optogenetic inhibition of mPCF neuronal terminals or local infusion of the CRF receptor 1 (CRFR1) antagonist in the NAc restored the effects of neuropathic pain on morphine-induced CPP behavior, but not in normal mice. On a molecular level, in CCI mice, CRFR1 protein expression was increased in the NAc by a histone dimethyltransferase G9a-mediated epigenetic mechanism. Local G9a knockdown increased the expression of CRFR1 and mimicked CCI-induced hypersensitivity to acquiring morphine CPP. Taken together, these findings demonstrate a previously unknown and specific mPFC CRF engagement of NAc neuronal circuits, the sensitization of which facilitates behavioral responses to morphine reward in neuropathic pain states via CRFR1s.

Opioids: Clinical Practice, Monitoring, and Medicolegal Considerations

Background

In the past decade, opioid use in the general population of the US has increased dramatically. Concomitantly, opioid-related morbidity and mortality have also risen steeply. The causes of opioid over-prescribing are multifactorial, with pressure from medical agencies, patients, aggressive patient-directed marketing, and use of patient surveys as an evaluation tool to unduly influence medical providers' decision-making. Providers also have significant concerns regarding scrutiny from their medical board and exposure to medicolegal liability.

Content

To provide the basis for best practice recommendations, several aspects of modern opioid prescribing practice require review. The practicing clinician should be aware of: (a) the pervasiveness of current opioid prescribing within the US; (b) the availability and applicability of clinical tools used to assess patient risk; (c) the new guidelines designed to facilitate appropriate and safe medical use of opioids; (d) the incorporation of clinical tools and best documentation practices to reduce medicolegal exposure.

Summary

On completion of this review, the reader should be able to recognize the magnitude of the problem of opioid over-prescribing in the US and identify several patient risk factors for opioid misuse, abuse, and/or diversion. Specifically, better familiarity with the recently published CDC guidelines for opioid prescribing will help ensure the adoption of best-use practices that maximize therapeutic efficacy while attenuating the possibility of harm to patients. A thorough review of the legal principles and risk-mitigation strategies relevant to opioid prescribing will also lessen the clinician's exposure to medicolegal liability.