Addictions in pain clinics and pain treatment

Day-to-day hedonic and calming effects of opioids, opioid craving, and opioid misuse among patients with chronic pain prescribed long-term opioid therapy

ABSTRACT

Concerns have been raised regarding the misuse of opioids among patients with chronic pain. Although a number of factors may contribute to opioid misuse, research has yet to examine if the hedonic and calming effects that can potentially accompany the use of opioids contribute to opioid misuse. The first objective of this study was to examine the degree to which the hedonic and calming effects of opioids contribute to opioid misuse in patients with chronic pain. We also examined whether the hedonic and calming effects of opioids contribute to patients' daily levels of opioid craving, and whether these associations were moderated by patients' daily levels of pain intensity, catastrophizing, negative affect, or positive affect. In this longitudinal diary study, patients (n = 103) prescribed opioid therapy completed daily diaries for 14 consecutive days. Diaries assessed a host of pain, psychological, and opioid-related variables. The hedonic and calming effects of opioids were not significantly associated with any type of opioid misuse behavior. However, greater hedonic and calming effects were associated with heightened reports of opioid craving (both P's < 0.005). Analyses revealed that these associations were moderated by patients' daily levels of pain intensity, catastrophizing, and negative affect (all P's < 0.001). Results from this study provide valuable new insights into our understanding of factors that may contribute to opioid craving among patients with chronic pain who are prescribed long-term opioid therapy. The implications of our findings for the management of patients with chronic pain are discussed.

Day-to-day opioid withdrawal symptoms, psychological distress, and opioid craving in patients with chronic pain prescribed opioid therapy

BACKGROUND

Research has shown that opioid craving is one of the strongest determinants of opioid misuse in patients with chronic pain. To date, however, little is known on the factors that contribute to opioid craving in these patients. It is possible that patients' physical dependence to opioids, manifested by opioid withdrawal symptoms in between daily opioid doses, contribute to opioid craving. Physical dependence symptoms might also lead to psychological distress, which in turn might contribute to opioid craving. The first objective of this study was to examine the day-to-day association between opioid withdrawal symptoms and opioid craving among patients with chronic pain. We also examined whether negative affect and catastrophic thinking mediated this association.

METHODS

In this longitudinal study, chronic pain patients (n = 79) prescribed short-acting opioids completed daily diaries for 14 consecutive days. Diaries assessed a host of pain, psychological, and opioid-related variables.

RESULTS

Day-to-day elevations in opioid withdrawal symptoms were associated with heightened opioid craving (p < .001). Results of a multilevel mediation analysis revealed that this association was mediated by patients' daily levels of negative affect and catastrophizing (p < .001).

CONCLUSIONS

Our study provides valuable new insights into our understanding of factors that may contribute to prescription opioid craving among patients with chronic pain.

GluA1 in Central Amygdala Promotes Opioid Use and Reverses Inhibitory Effect of Pain

Increasing evidence suggests that long-term opioids and pain induce similar adaptive changes in the brain's reward circuits, however, how pain alters the addictive properties of opioids remains poorly understood. In this study using a rat model of morphine self-administration (MSA), we found that short-term pain, induced by an intraplantar injection of complete Freund's adjuvant (CFA), acutely decreased voluntary morphine intake, but not food intake, only at a morphine dose that did not affect pain itself. Pre-treatment with indomethacin, a non-opioid inhibitor of pain, before the pain induction blocked the decrease in morphine intake. In rats with steady MSA, the protein level of GluA1 subunits of glutamate AMPA receptors (AMPARs) was significantly increased, but that of GluA2 was decreased, resulting in an increased GluA1/GluA2 ratio in central nucleus of the amygdala (CeA). In contrast, pain decreased the GluA1/GluA2 ratio in the CeA of rats with MSA. Microinjection of NASPM, a selective inhibitor of homomeric GluA1-AMPARs, into CeA inhibited morphine intake. Furthermore, viral overexpression of GluA1 protein in CeA maintained morphine intake at a higher level than controls and reversed the pain-induced reduction in morphine intake. These findings suggest that CeA GluA1 promotes opioid use and its upregulation is sufficient to increase opioid consumption, which counteracts the acute inhibitory effect of pain on opioid intake. These results demonstrate that the CeA GluA1 is a shared target of opioid and pain in regulation of opioid use, which may aid in future development of therapeutic applications in opioid abuse.

Substance-related disorders: A review of prevalence and correlates among patients with chronic pain

Over the past few decades, research has revealed high rates of substance-related disorders among patients with chronic pain. In addition to their potentially deleterious health consequences, substance-related disorders have consistently been associated with negative pain-related outcomes among patients with chronic pain. The goal of this narrative review was to provide an overview of studies that have examined the prevalence and correlates of substance-related disorders among patients with chronic pain. A particular focus was placed on opioids, sedatives/hypnotics, cannabis, tobacco, and alcohol given that these substances have received the bulk of research attention among patients with pain. Research conducted to date suggests that a host of biological and psychological factors are likely to contribute to the elevated rates of substance-related disorders among patients with chronic pain. In this review, in addition to reviewing the prevalence and correlates of substance-related disorders among patients with pain, we briefly discussed the changes that were recently made from the DSM-4 to the DSM-5 in the diagnostic criteria for substance-related disorders, and the implications of these changes for the assessment of patients with chronic pain. We also provided a brief overview of instruments that can be used for the assessment of these disorders in clinical and research settings.

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.

OPRM1 influence on and effectiveness of an individualized treatment plan for prescription opioid use disorder patients

Screening for opioid use disorder should be considered in chronic non-cancer pain (CNCP) patients with long-term use of opioids. The aim of our study was to assess the effectiveness of an individualized treatment plan (ITP) for prescription opioid dependence that included screening of pharmacogenetic markers. An observational prospective study was performed using prescription opioid-dependent CNCP outpatients (n = 88). Patients were divided into nonresponders, responders, or high responders according to their response to the ITP. Genotyping of OPRM1 (A118G), OPRD1 (T921C), COMT (G472A), ABCB1 (C3435T), and ARRB2 (C8622T) was performed by real-time PCR. Our ITP achieved a significant reduction of the morphine equivalent daily dose (MEDD) in 64% of responders, including 33% of high responders. Nonopioid medication or buprenorphine use was significantly higher at final versus basal visit. 118-AA OPRM1 patients required significantly lower MEDD at basal and final visits. Our ITP showed effectiveness and security in reducing MEDD in opioid-dependent patients, with good conversion to buprenorphine that was more pronounced in 118-AA OPRM1 patients.

Opioid analgesic administration in patients with suspected drug use

ABSTRACT Objective: To identify the prevalence of patients suspected of drug use according to the nursing professionals' judgement, and compare the behavior of these professionals in opioid administration when there is or there is no suspicion that patient is a drug user. Method: A cross-sectional study with 507 patients and 199 nursing professionals responsible for administering drugs to these patients. The Chi-Square test, Fisher's Exact and a significance level of 5% were used for the analyzes. Results: The prevalence of suspected patients was 6.7%. The prevalence ratio of administration of opioid analgesics 'if necessary' is twice higher among patients suspected of drug use compared to patients not suspected of drug use (p = 0.037). Conclusion: The prevalence of patients suspected of drug use was similar to that of studies performed in emergency departments. Patients suspected of drug use receive more opioids than patients not suspected of drug use.

Effects of repeated morphine on intracranial self-stimulation in male rats in the absence or presence of a noxious pain stimulus

Research on opioid analgesics such as morphine suggests that expression of abuse-related effects increases with repeated exposure. Repeated exposure to opioids often occurs clinically in the context of pain management, and a major concern for clinicians is the risk of iatrogenic addiction and dependence in patients receiving opioids for treatment of pain. This study compared abuse-related morphine effects in male rats in an intracranial self-stimulation (ICSS) procedure after repeated treatment either with morphine alone or with morphine in combination with a repeated noxious stimulus (intraperitoneal administration of dilute acid). The study also permitted comparison of morphine potency and effectiveness to block acid-induced depression of ICSS (antinociception) and to produce enhanced facilitation of ICSS (abuse-related effect). There were 3 main findings. First, initial morphine exposure to drug naïve rats did not produce abuse-related ICSS facilitation. Second, repeated daily treatment with 3.2 mg/kg/day morphine for 6 days increased expression of ICSS facilitation. This occurred whether morphine was administered in the absence or presence of the noxious stimulus. Finally, a lower dose of 1.0 mg/kg/day morphine was sufficient to produce antinociception during repeated acid treatment, but this lower dose did not reliably increase abuse-related morphine effects. Taken together, these results suggest that prior morphine exposure can increase abuse liability of subsequent morphine treatments even when that morphine exposure occurs in the context of a pain state. However, it may be possible to relieve pain with relatively low morphine doses that do not produce increases in abuse-related morphine effects.

Persistent pain maintains morphine-seeking behavior after morphine withdrawal through reduced MeCP2 repression of GluA1 in rat central amygdala

As long-term opioids are increasingly used for control of chronic pain, how pain affects the rewarding effect of opioids and hence risk of prescription opioid misuse and abuse remains a healthcare concern and a challenging issue in current pain management. In this study, using a rat model of morphine self-administration, we investigated the molecular mechanisms underlying the impact of pain on operant behavior of morphine intake and morphine seeking before and after morphine withdrawal. We found that rats with persistent pain consumed a similar amount of daily morphine to that in control rats without pain, but maintained their level-pressing behavior of morphine seeking after abstinence of morphine at 0.2 mg/kg, whereas this behavior was gradually diminished in control rats. In the central nucleus of amygdala (CeA), a limbic structure critically involved in the affective dimension of pain, proteins of GluA1 subunits of glutamate AMPA receptors were upregulated during morphine withdrawal, and viral knockdown of CeA GluA1 eliminated the morphine-seeking behavior in withdrawn rats of the pain group. Chromatin immunoprecipitation analysis revealed that the methyl CpG-binding protein 2 (MeCP2) was enriched in the promoter region of Gria1 encoding GluA1 and this enrichment was significantly attenuated in withdrawn rats of the pain group. Furthermore, viral overexpression of CeA MeCP2 repressed the GluA1 level and eliminated the maintenance of morphine-seeking behavior after morphine withdrawal. These results suggest direct MeCp2 repression of GluA1 function as a likely mechanism for morphine-seeking behavior maintained by long-lasting affective pain after morphine withdrawal.

Validation of a brief Opioid Compliance Checklist for patients with chronic pain

There has been a need for a brief assessment tool to determine compliance with use of prescribed opioids for pain. The purpose of this study was to develop and begin the validation of a brief and simple compliance checklist (Opioid Compliance Checklist [OCC]) for chronic pain patients prescribed long-term opioid therapy. A review of the literature of opioid therapy agreements led to a 12-item OCC that was repeatedly administered to 157 patients who were taking opioids for chronic pain and followed for 6 months. Validation of the OCC was conducted by identifying those patients exhibiting aberrant drug-related behavior as determined by any of the following: positive urine toxicology screen, a positive score on the Prescription Drug Use Questionnaire interview or Current Opioid Misuse Measure, and/or ratings by staff on the Addiction Behavior Checklist. Of the original 12 items, 5 OCC items appeared to best predict subsequent aberrant behaviors based on multivariate logistic regression analyses (cross-validated area under the receiver operating characteristic curve = .67). Although further testing is needed, these results suggest that the OCC is an easy-to-use, promising measure in monitoring opioid adherence among persons with chronic pain.

PERSPECTIVE

This study presents validation of a brief 5-item compliance checklist for use with chronic pain patients prescribed long-term opioid therapy. This measure asks patients about aberrant drug-related behavior over the past month, and any positive response indicates problems with adherence with opioids. Further cross-validation testing is needed.

MeCP2 repression of G9a in regulation of pain and morphine reward

Opioids are commonly used for pain relief, but their strong rewarding effects drive opioid misuse and abuse. How pain affects the liability of opioid abuse is unknown at present. In this study, we identified an epigenetic regulating cascade activated by both pain and the opioid morphine. Both persistent pain and repeated morphine upregulated the transcriptional regulator MeCP2 in mouse central nucleus of the amygdala (CeA). Chromatin immunoprecipitation analysis revealed that MeCP2 bound to and repressed the transcriptional repressor histone dimethyltransferase G9a, reducing G9a-catalyzed repressive mark H3K9me2 in CeA. Repression of G9a activity increased expression of brain-derived neurotrophic factor (BDNF). Behaviorally, persistent inflammatory pain increased the sensitivity to acquiring morphine-induced, reward-related behavior of conditioned place preference in mice. Local viral vector-mediated MeCP2 overexpression, Cre-induced G9a knockdown, and CeA application of BDNF mimicked, whereas MeCP2 knockdown inhibited, the pain effect. These results suggest that MeCP2 directly represses G9a as a shared mechanism in central amygdala for regulation of emotional responses to pain and opioid reward, and for their behavioral interaction.

Ask the Experts: What do we know (and not know) about prescription opioid misuse in the context of chronic pain management?

James Zacny received his PhD in Psychology at West Virginia University (WV, USA) in 1984. From 1984 to 1986 he did a postdoctoral fellowship at The Johns Hopkins University School of Medicine (MD, USA) in the Behavioral Pharmacology Research Unit of the Department of Psychiatry and Behavioral Sciences. He then became Research Associate in the Department of Psychiatry at the University of Chicago (IL, USA) and conducted both preclinical and human psychopharmacology studies. In 1992 he joined the faculty in the Department of Anesthesia & Critical Care at the University where he is currently Professor. His two primary research interests have been in studying the psychopharmacological effects of drugs used in anesthesiology, chiefly inhaled and intravenous general anesthetics at subanesthestic doses, and opioid analgesics, in healthy nondrug-abusing volunteers. The unique research environment he is in fostered a large body of research that systematically characterized the subjective, psychomotor and reinforcing (rewarding) effects of a number of different anesthetic and analgesic agents. Dr Zacny's primary source of funding is through the National Institute on Drug Abuse and in 1999 was presented with a MERIT award for his research on opioids. In 2001 he focused his efforts on prescription opioids at about the same time that warning signs started to emerge indicating that prescription opioid abuse was on the rise. He has characterized the psychopharmacological effects of a number of prescription opioids, as well as investigated possible factors that might modulate their positive (as well as negative) subjective effects including gender, sensation seeking and alcohol. He has also written guest editorials on the psychomotor effects of opioids in relation to the ability of chronic pain patients on long-term opioid therapy to drive. He is an elected member of the College on Problems of Drug Dependence and of the Association of University Anesthesiologists, and served as President of the Division of Psychopharmacology and Substance Abuse of the American Psychological Association, and the International Study Group Investigating Drugs as Reinforcers.

Tamper-resistant opioid formulations in the treatment of acute pain

INTRODUCTION

Pain-including acute or persistent acute pain-is a common condition that is increasingly being treated with opioids in the United States. The acute pain treatment setting may represent a key target for addressing the growing epidemic of prescription drug abuse occurring hand in hand with the rise in opioid prescribing. Balancing the needs of pain treatment with abuse prevention can be challenging for clinicians.

METHODS

This article identified efforts to balance opioid abuse risks with opioid availability through the extensive experience of the author in this field. In addition, PubMed literature searches using terms such as "prescription opioid abuse", "abuse-deterrent opioids", and "tamper-resistant opioids"; and inspection of the bibliographies of relevant articles were used to identify relevant sources.

RESULTS

These multifaceted efforts have included: improving assessment of patient risk for drug misuse, abuse, or diversion; funding of and encouraging referral to addiction treatment programs; access to and widespread use of prescription monitoring programs (PMPs); public knowledge of prescription opioid abuse; proper storage of opioid medications; and development of new formulations designed to resist tampering and deter abuse. This review discusses the problem of prescription opioid abuse and strategies to minimize risk within the context of acute pain treatment, and explores the potential role of tamper-resistant opioid formulations and other abuse deterrence strategies in the area of acute or persistent acute pain management.

CONCLUSION

In order to stem the tide of prescription opioid abuse and preserve the availability of opioids as a much needed analgesic option, a multifaceted approach that includes tamper-resistant opioid formulations-for chronic or acute pain-along with strategies such as improved patient risk assessment, funding for and referral to addiction treatment programs, greater use of PMPs, and raised awareness of prescription opioid abuse is needed.

The association between negative affect and prescription opioid misuse in patients with chronic pain: the mediating role of opioid craving

Over the past decade, considerable research has accumulated showing that chronic pain patients experiencing high levels of negative affect (NA) are at increased risk for prescription opioid misuse. The primary objective of the present study was to examine the factors that underlie the association between NA and prescription opioid misuse among patients with chronic pain. In this study, 82 patients with chronic musculoskeletal pain being prescribed opioid medication completed the Current Opioid Misuse Measure, a well-validated self-report questionnaire designed to assess prescription opioid misuse. Patients were also asked to complete self-report measures of pain intensity, NA, and opioid craving. A bootstrapped multiple mediation analysis was used to examine the mediating role of patients' pain intensity and opioid craving in the association between NA and prescription opioid misuse. Consistent with previous research, we found a significant association between NA and prescription opioid misuse. Interestingly, results revealed that opioid craving, but not pain intensity, mediated the association between NA and opioid misuse. The Discussion addresses the potential psychological and neurobiological factors that might contribute to the interrelationships among NA, opioid craving, and prescription opioid misuse in patients with pain. The clinical implications of our findings are also discussed.

PERSPECTIVE

Our study provides new insights into the factors that underlie the association between negative affect and prescription opioid misuse in patients with chronic pain. Our findings could have important clinical implications, particularly for patients being prescribed opioid medication, and for reducing rates of opioid misuse in patients with pain.

Characteristics of medical inpatients with acute pain and suspected non-medical use of opioids

OBJECTIVE

The purpose of this study was to characterize medical inpatients with acute pain suspected of non-medical opioid use.

METHOD

Medical inpatients treated with opioids for acute pain referred for psychiatric consultation were administered questionnaires including the Screener and Opioid Assessment for Pain Patients (SOAPP) and the Hospital Misuse Checklist (HMC), developed for this study.

RESULTS

The nine subjects referred for evaluation of possible non-medical opioid use, compared to the 23 subjects referred for other reasons, were younger (37.7 vs. 51.3, t = 2.81, p = .012), more likely to score positive on the SOAPP (100% vs. 47.8%, Fisher's p < .05) and report lifetime histories of any substance use disorder (SUD) (88.9% vs. 30.4%, χ²  = 9.7, p = .002). No differences were found on items on the HMC.

CONCLUSIONS

The results of this preliminary study indicate that medical inpatients with suspected non-medical use of opioids resemble chronic pain outpatients misusing opioids. Further research is needed to better characterize this patient population and to validate the HMC measure.