Chronic pain and addiction: challenging co-occurring disorders

Prevalence and perceptions of pain in people with haemophilia: A UK study

INTRODUCTION

Joint bleeds in haemophilia cause destruction of articular structures, impaired function and pain. Up to 70% of people with haemophilia (PWH) report chronic pain. Little is known about the pain experiences in PWH in the UK.

AIM

To identify prevalence and perceptions of pain among PWH living in the UK.

METHODS

A cross-sectional, non-interventional survey study conducted among PWH (all severities). The survey incorporated elements from validated tools (EQ-5D; EQ-VAS) and was distributed via participating treatment centres.

RESULTS

Five hundred and ninety-nine PWH responded, 91% aged > 18. 81% used factor prophylactically or on demand. More pain was reported by those treated on demand versus prophylaxis particularly in those who reported daily pain. 65% reported 'problem joints' based on individual impact rather than medically defined 'target joints', 2/3 reported multiple joint issues. The ankle was most commonly affected. 59% reported frequent pain, with 56% aware of pain constantly or most of the time and were more likely to report less favourable EQ-5D or EQ-VAS scores (p < .001). Pain frequency/awareness was consistent across all severities. Most discussed pain with care teams, 31% only when asked; 25% did not discuss it. Pain discussions resulted in physiotherapy referral (63%) analgesia prescription (48%), and a minority specialist pain referral (9%). Most felt well supported with regard to their pain, but 70% reported learning to live with it.

CONCLUSION

Pain affects PWH of all ages and severities even in a well-resourced country significantly impacting quality of life. Clinicians must be more aware of chronic pain in PWH. Biopsychosocial approaches to pain assessment and management are recommended.

A pain-induced tonic hypodopaminergic state augments phasic dopamine release in the nucleus accumbens

Diseases and disorders such as Parkinson disease, schizophrenia, and chronic pain are characterized by altered mesolimbic dopaminergic neurotransmission. Dopamine release in the nucleus accumbens influences behavior through both tonic and phasic signaling. Tonic dopamine levels are hypothesized to inversely regulate phasic signals through dopamine D2 receptor feedback inhibition. We tested this hypothesis directly in the context of ongoing pain. Tonic and phasic dopamine signals were measured using fast-scan controlled-adsorption voltammetry and fast-scan cyclic voltammetry, respectively, in the nucleus accumbens shell of male rats with standardized levels of anesthesia. Application of capsaicin to the cornea produced a transient decrease in tonic dopamine levels. During the pain-induced hypodopaminergic state, electrically evoked phasic dopamine release was significantly increased when compared to baseline, evoked phasic release. A second application of capsaicin to the same eye had a lessened effect on tonic dopamine suggesting desensitization of TRPV1 channels in that eye. Capsaicin treatment in the alternate cornea, however, again produced coincident decreased dopaminergic tone and increased phasic dopamine release. These findings occurred independently of stimulus lateralization relative to the hemisphere of dopamine measurement. Our data show that (1) the mesolimbic dopamine circuit reliably encodes acute noxious stimuli; (2) ongoing pain produces decreases in dopaminergic tone; and (3) pain-induced decreases in tonic dopamine correspond to augmented evoked phasic dopamine release. Enhanced phasic dopamine neurotransmission resulting from salient stimuli may contribute to increased impulsivity and cognitive deficits often observed in conditions associated with decreased dopaminergic tone, including Parkinson disease and chronic pain.

The α2,3-selective potentiators of GABAA receptors, KRM-II-81 and MP-III-80, produce anxiolytic-like effects and block chemotherapy-induced hyperalgesia in mice without tolerance development

Opiate analgesics are one of the treatment options for severe chronic pain, including late-stage cancer, chronic back pain and other disorders. The recent resurgence in opioid overdose has highlighted the serious need for alternative medicines for pain management. While a role for potentiators of α2/3-containing GABA_A receptors in the modulation of pain has been known for several years, advancements in this area required data from selective compounds. KRM-II-81(5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepin-3- yl)oxazole) and analogs selectively potentiate GABA_A receptors containing α2/3 subunits and have recently been shown to attenuate pain behaviors in several acute and chronic pain models in rodents. The present study was designed to ascertain whether KRM-II-81 and the structural analog MP-III-80 (3-ethyl-5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepin-3-yl)-1,2,4-oxadiazole) would block chemotherapeutic agent paclitaxel-induced pain in male, C57BL/6 mice. Both compounds significantly inhibited pain behaviors evoked by cold and tactile stimulation in paclitaxel-treated mice as did the neuropathic pain drug gabapentin. Subchronic dosing for 22 days with KRM-II-81 and MP-III-80 demonstrated enduring analgesic efficacy without tolerance development, while the effects of gabapentin showed evidence of tolerance development. KRM-II-81 and MP-III-80 also decreased marble-burying behavior in this mouse strain as did the anxiolytic drug chlordiazepoxide. In contrast to KRM-II-81 and MP-III-80, chlordiazepoxide had motor-impairing effects at anxiolytic-like doses. The data add to the literature documenting that these selective potentiators of α2/3-containing GABA_A receptors are effective in a host of animal models used to detect novel analgesic drugs. The anxiolytic-like efficacy of these compounds fits well with the comorbidity of anxiety in patients with chronic pain and cancer.

Nanotechnology in Chronic Pain Relief

Increasing awareness of chronic pain due to both injury and disease have encouraged drug companies and pharmaceutical researchers alike to design and fabricate better, more specific drugs for pain relief. However, overuse of clinically available pain medication has caused a multitude of negative repercussions, including drug tolerance, addiction, and other severe side effects, which can prolong suffering and reduce pain mediation. Applications of nanotechnology to the field of drug delivery has sought to enhance the treatment efficiency, lower side effects, and mitigate the formation of tolerance. The use of nanomaterials has several advantages for chronic pain relief, such as controlled release, prolonged circulation time, and limited side effects. With the development of nanotechnology, strategies for chronic pain relief have also bourgeoned utilizing a variety of nanomaterials and targeting surface modifications. In addition to using these materials as carriers for drug delivery, nanomaterials can also be designed to have inherent properties that relieve chronic pain. This minireview covers the current status of designed nanomaterials for pain relief and provides a discussion of future considerations for nanotechnology designed for relieving chronic pain.

The Mesolimbic Dopamine System in Chronic Pain and Associated Affective Comorbidities

Chronic pain is a complex neuropsychiatric disorder characterized by sensory, cognitive, and affective symptoms. Over the past 2 decades, researchers have made significant progress toward understanding the impact of mesolimbic dopamine circuitry in acute and chronic pain. These efforts have provided insights into the circuits and intracellular pathways in the brain reward center that are implicated in sensory and affective manifestations of chronic pain. Studies have also identified novel therapeutic targets as well as factors that affect treatment responsiveness. Dysregulation of dopamine function in the brain reward center may further promote comorbid mood disorders and vulnerability to addiction. This review discusses recent clinical and preclinical findings on the neuroanatomical and neurochemical adaptations triggered by prolonged pain states in the brain reward pathway. Furthermore, this discussion highlights evidence of mechanisms underlying comorbidities among pain, depression, and addiction.

Optimizing the Management and Outcomes of Failed Back Surgery Syndrome: A Proposal of a Standardized Multidisciplinary Team Care Pathway

Failed back surgery syndrome (FBSS) is a major, worldwide health problem that generates considerable expense for healthcare systems. A number of controversial issues concerning the management of FBSS are regularly debated, but no clear consensus has been reached. This pitfall is the result of lack of a standardized care pathway due to insufficient characterization of underlying pathophysiological mechanisms, which are essential to identify in order to offer appropriate treatment, and the paucity of evidence of treatment outcomes. In an attempt to address the challenges and barriers in the clinical management of FBSS, an international panel of physicians with a special interest in FBSS established the Chronic Back and Leg Pain (CBLP) Network with the primary intention to provide recommendations through consensus on how to optimize outcomes. In the first of a series of two papers, a definition of FBSS was delineated with specification of criteria for patient assessment and identification of appropriate evaluation tools in order to choose the right treatment options. In this second paper, we present a proposal of a standardized care pathway aiming to guide clinicians in their decision-making on how to optimize their management of FBSS patients. The utilization of a multidisciplinary approach is emphasized to ensure that care is provided in a uniform manner to reduce variation in practice and improve patient outcomes.

Evaluation and comparison of tools for diagnosing problematic prescription opioid use among chronic pain patients

Prescription opioid medications are commonly used for the treatment of chronic pain. Assessments of problematic opioid use among pain patients are inconsistent across studies, partially due to differences between various measures. Therefore, the most appropriate measure to use is often unclear. In this study we assessed problematic opioid use in a sample of 551 individuals receiving treatment for chronic pain, using three questionnaires: the Alcohol Use Disorder and Associated Disabilities Interview Schedule - Fourth Edition (AUDADIS-IV), the Current Opioid Misuse Measure (COMM) questionnaire and Portenoy's criteria (PC). These questionnaires yielded discordant positive rates of problematic use: 52.6%, 28.7%, and 17.1%, respectively, which did not change substantially when excluding AUDADIS-IV criteria of physical symptoms of tolerance and withdrawal. Although these three questionnaires share some statistically correlated content-based congruent questions, positive response rates to them were significantly different based on construction features, including questionnaires' referred time-frame, wording of questions and response alternatives. The findings of the present study illustrate strengths and limitations of the AUDADIS-IV, COMM and PC in diagnosing problematic opioid use in a population of adults suffering from chronic pain, and highlight the importance of recognizing and addressing specific questionnaire and question-related differences when identifying problematic opioid use in this population.

Peripherally Selective Cannabinoid 1 Receptor (CB1R) Agonists for the Treatment of Neuropathic Pain

Alleviation of neuropathic pain by cannabinoids is limited by their central nervous system (CNS) side effects. Indole and indene compounds were engineered for high hCB1R affinity, peripheral selectivity, metabolic stability, and in vivo efficacy. An epithelial cell line assay identified candidates with <1% blood-brain barrier penetration for testing in a rat neuropathy induced by unilateral sciatic nerve entrapment (SNE). The SNE-induced mechanical allodynia was reversibly suppressed, partially or completely, after intraperitoneal or oral administration of several indenes. At doses that relieve neuropathy symptoms, the indenes completely lacked, while the brain-permeant CB1R agonist HU-210 (1) exhibited strong CNS side effects, in catalepsy, hypothermia, and motor incoordination assays. Pharmacokinetic findings of ∼0.001 cerebrospinal fluid:plasma ratio further supported limited CNS penetration. Pretreatment with selective CB1R or CB2R blockers suggested mainly CB1R contribution to an indene's antiallodynic effects. Therefore, this class of CB1R agonists holds promise as a viable treatment for neuropathic pain.

Treating co-occurring chronic low back pain & generalized anxiety disorder

The complex, bidirectional correlation between chronic low back pain (CLBP) and generalized anxiety disorder (GAD), common ailments in primary care, can increase the risk of inadequate treatment. This article will review the relationship between CLBP and GAD and provide optimal management strategies for NPs caring for individuals with this dyad.

Impact of Chronic Pain on Treatment Prognosis for Patients with Opioid Use Disorder: A Systematic Review and Meta-analysis

BACKGROUND

While a number of pharmacological interventions exist for the treatment of opioid use disorder, evidence evaluating the effect of pain on substance use behavior, attrition rate, and physical or mental health among these therapies has not been well established. We aim to evaluate these effects using evidence gathered from a systematic review of studies evaluating chronic non-cancer pain (CNCP) in patients with opioid use disorder.

METHODS

We searched the Medline, EMBASE, PubMed, PsycINFO, Web of Science, Cochrane Database of Systematic Reviews, ProQuest Dissertations and theses Database, Cochrane Central Register of Controlled Trials, World Health Organization International Clinical Trials Registry Platform Search Portal, and National Institutes for Health Clinical Trials Registry databases to identify articles evaluating the impact of pain on addiction treatment outcomes for patients maintained on opioid agonist therapy.

RESULTS

Upon screening 3,540 articles, 14 studies with a combined sample of 3,128 patients fulfilled the review inclusion criteria. Results from the meta-analysis suggest that pain has no effect on illicit opioid consumption [pooled odds ratio (pOR): 0.70, 95%CI 0.41–1.17; I² = 0.0] but a protective effect for reducing illicit non-opioid substance use (pOR: 0.57, 95%CI 0.41–0.79; I² = 0.0). Studies evaluating illicit opioid consumption using other measures demonstrate pain to increase the risk for opioid abuse. Pain is significantly associated with the presence of psychiatric disorders (pOR: 2.18; 95%CI 1.6, 2.9; I² = 0.0%).

CONCLUSION

CNCP may increase risk for continued opioid abuse and poor psychiatric functioning. Qualitative synthesis of the findings suggests that major methodological differences in the design and measurement of pain and treatment response outcomes are likely impacting the effect estimates.

Prevalence and experience of chronic pain in suburban drug injectors

AIMS

To explore the relationship between chronic pain and characteristics, behaviors, and psychological status of suburban Connecticut injection drug users.

METHODS

Cross-sectional study with quantitative interview and serological testing for HIV and hepatitis B and C in 456 individuals who injected drugs in the past month. Participants were dichotomized into those reporting current chronic pain of at least six months duration and all others. The interview covered (i) sociodemographics, (ii) injection drug use, (iii) interactions with drug treatment, criminal justice, and harm reduction, (iv) screening for alcohol use, chronic pain, anxiety, and depression, and (v) knowledge regarding HIV, hepatitis B (HBV) and C (HCV), and opioid overdose. Serological testing for HIV, HBV, and HCV was conducted.

RESULTS

One-third (n = 143) reported chronic pain. These individuals differed significantly from those not reporting chronic pain on characteristics that included older age, lower educational achievement, and injection of pharmaceutical opioids. They also reported experiencing more psychological and family problems on the ASI and higher levels of depression and anxiety. Four of five individuals with chronic pain (n = 117) reported non-medical opioid use prior to the onset of chronic pain.

CONCLUSIONS

Chronic pain is common among drug injectors in our study population although it was unusual for chronic pain to have preceded non-medical opioid use. Psychological problems in injectors with co-occurring chronic pain are likely pose significant complications to successful treatment for substance abuse, pain, or infectious disease treatment.

A Pilot Study To Define Chemical Coping in Cancer Patients Using the Delphi Method

BACKGROUND

"Chemical coping" is a commonly used term in the pain and palliative care literature, but is heterogeneously defined. We conducted a Delphi survey among palliative care and pain specialists internationally to identify a consensus definition for "chemical coping with opioids" and warning signs for chemical coping.

METHODS

This Delphi survey consisted of two rounds on the following: (1) concepts and definition related to chemical coping, (2) warning signs for chemical coping, and (3) demographics. Consensus in this study was defined as agreement by a minimum of 70% of the experts.

RESULTS

Participating in the first round were 14/19 (74%) physicians; 12/14 (86%) participated in the second round. The international experts reached the following consensus definition for chemical coping with opioids (92% agreement): "The use of opioids to cope with emotional distress, characterized by inappropriate and/or excessive opioid use." They also identified depression (consensus 93%); psychiatric disease (86%); a history of substance abuse (86%); a positive score for the Cut-down, Annoyed, Guilty, and Eye-opener (CAGE) alcoholism screening test (79%); a history of alcoholism (79%); and a history of smoking (71%) as important warning signs for chemical coping.

CONCLUSION

Our expert panel reached a consensus definition for chemical coping and related warning signs, which may help clinicians and researchers to identify patients at risk of opioid misuse.

The impact of chronic pain on opioid addiction treatment: a systematic review protocol

BACKGROUND

The consequences of opioid relapse among patients being treated with opioid substitution treatment (OST) are serious and can result in abnormal cardiovascular function, overdose, and mortality. Chronic pain is a major risk factor for opioid relapse within the addiction treatment setting. There exist a number of opioid maintenance therapies including methadone, buprenorphine, naltrexone, and levomethadyl acetate (LAAM), of which the mediating effects of pain on treatment attrition, substance use behavior, and social functioning may differ across therapies. We aim to 1) evaluate the impact of pain on the treatment outcomes of addiction patients being managed with OST and 2) identify the most recently published opioid maintenance treatment guidelines from the United States, Canada, and the UK to determine how the evidence is being translated into clinical practice.

METHODS/DESIGN

The authors will search Medline, EMBASE, PubMed, PsycINFO, Web of Science, Cochrane Database of Systematic Reviews, ProQuest Dissertations and theses Database, Cochrane Central Register of Controlled Trials (CENTRAL), World Health Organization International Clinical Trials Registry Platform Search Portal, and the National Institutes for Health Clinical Trials Registry. We will search www.

GUIDELINES

gov and the National Institute for Care and Excellence (NICE) databases to identify the most recently published OST guidelines. All screening and data extraction will be completed in duplicate. Provided the data are suitable, we will perform a multiple treatment comparison using Bayesian meta-analytic methods to produce summary statistics estimating the effect of chronic pain on all OSTs. Our primary outcome is substance use behavior, which includes opioid and non-opioid substance use. We will also evaluate secondary endpoints such as treatment retention, general physical health, intervention adherence, personal and social functioning, as well as psychiatric symptoms.

DISCUSSION

This review will capture the experience of treatment outcomes for a sub-population of opioid addiction patients and provide an opportunity to distinguish the best quality guidelines for OST. If chronic pain truly does result in negative consequences for opioid addiction patients, it is important we identify which OSTs are most appropriate for chronic pain patients as well as ensure the treatment guidelines incorporate this information.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014014015 http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42014014015#.VS1Qw1wkKGM.

Agreement between definitions of pharmaceutical opioid use disorders and dependence in people taking opioids for chronic non-cancer pain (POINT): a cohort study

BACKGROUND

Classification of patients with pharmaceutical opioid use disorder and dependence varies depending on which definition is used. We compared how WHO's ICD-10 and proposed ICD-11 and the American Psychiatric Association's DSM-IV and DSM-5 classified individuals in a community-based sample of Australians with chronic non-cancer pain for which opioids have been prescribed.

METHODS

We studied participants in the Pain and Opioid IN Treatment (POINT) cohort, a 2 year prospective cohort study of 1514 people prescribed pharmaceutical opioids for their chronic pain who were recruited in 2012-13 from community-based pharmacies across Australia. After giving patients the Composite International Diagnostic Interview about their opioid use, we assessed which patients would be categorised as having disorders of pharmaceutical opioid use by ICD-10, the draft ICD-11, DSM-IV, and DSM-5. We examined agreement between classification systems, and tested the unidimensionality of the syndrome with confirmatory factor analysis.

FINDINGS

We included 1422 participants (median time of pain disorder 10 years [IQR 5-20]; median length of strong opioid prescription 4 years [IQR 1·5-10·0]; mean age 58 years). Similar proportions of individuals met lifetime criteria for dependence with DSM-IV (127; 8·9%), ICD-10 (121; 8·5%), and ICD-11 (141; 9·9%). Criteria in DSM-5 classified 127 (8·9%) participants with moderate or severe use disorder. There was excellent agreement between ICD-10, ICD-11 and DSM-IV dependence (κ>0·90). However, there was only fair to moderate agreement between ICD-10 and DSM-IV dependence diagnoses, and DSM-5 use disorder (mild, moderate, or severe). There was only good agreement between moderate to severe use disorder in DSM-5 and the other definitions. Criteria for all definitions loaded well on a single factor; the best model fit was for the definition for dependence in the draft ICD-11, the worst was in DSM-5.

INTERPRETATION

Classification of problematic pharmaceutical opioid use varies across editions of ICD and DSM. The much lower levels of agreement between DSM-5 and other definitions than between other definitions might be attributed to DSM-5 containing an increased number of criteria and treating dependence and problematic use as a continuum. The more parsimonious ICD-11 dependence definition showed excellent model fit and excellent agreement with previous classificatory systems.

FUNDING

Australian National Health and Medical Research Council.

Defining opioid tolerance and dependency

This report is adapted from paineurope 2013; Issue 2, ©Haymarket Medical Publications Ltd., and is presented with permission. paineurope is provided as a service to pain management by Mundipharma International, LTD. and is distributed free of charge to healthcare professionals in Europe. Archival issues can be accessed via the website: http://www.paineurope.com at which European health professionals can register online to receive copies of the quarterly publication.

Persistent pain facilitates response to morphine reward by downregulation of central amygdala GABAergic function

Opioid-based analgesics are widely used for treating chronic pain, but opioids are highly addictive when repeatedly used because of their strong rewarding effects. In recent years, abuse of prescription opioids has dramatically increased, including incidences of misuse of opioid drugs prescribed for pain control. Despite this issue in current clinical pain management, it remains unknown how pain influences the abuse liability of prescription opioids. Pain as aversive experience may affect opioid reward of positive emotion through common brain sites involved in emotion processing. In this study, on a rat model of chronic pain, we determined how persistent pain altered behavioral responses to morphine reward measured by the paradigm of unbiased conditioned place preference (CPP), focusing on GABAergic synaptic activity in neurons of the central nucleus of the amygdala (CeA), an important brain region for emotional processing of both pain and reward. We found that pain reduced the minimum number of morphine-conditioning sessions required for inducing CPP behavior. Both pain and morphine conditioning that elicited CPP inhibited GABA synaptic transmission in CeA neurons. Pharmacological activation of CeA GABAA receptors reduced the pain and inhibited CPP induced both by an effective dose of morphine and by a sub-threshold dose of morphine under pain condition. Furthermore, inhibition of CeA GABAA receptors mimicked the pain effect, rendering the sub-threshold dose of morphine effective in CPP induction. These findings suggest that pain facilitates behavioral responses to morphine reward by predisposing the inhibitory GABA function in the CeA circuitry involved in the behavior of opioid reward.

The downward spiral of chronic pain, prescription opioid misuse, and addiction: cognitive, affective, and neuropsychopharmacologic pathways

Prescription opioid misuse and addiction among chronic pain patients are emerging public health concerns of considerable significance. Estimates suggest that more than 10% of chronic pain patients misuse opioid analgesics, and the number of fatalities related to nonmedical or inappropriate use of prescription opioids is climbing. Because the prevalence and adverse consequences of this threat are increasing, there is a pressing need for research that identifies the biobehavioral risk chain linking chronic pain, opioid analgesia, and addictive behaviors. To that end, the current manuscript draws upon current neuropsychopharmacologic research to provide a conceptual framework of the downward spiral leading to prescription opioid misuse and addiction among chronic pain patients receiving opioid analgesic pharmacotherapy. Addictive use of opioids is described as the outcome of a cycle initiated by chronic pain and negative affect and reinforced by opioidergic-dopamingeric interactions, leading to attentional hypervigilance for pain and drug cues, dysfunctional connectivity between self-referential and cognitive control networks in the brain, and allostatic dysregulation of stress and reward circuitry. Implications for clinical practice are discussed; multimodal, mindfulness-oriented treatment is introduced as a potentially effective approach to disrupting the downward spiral and facilitating recovery from chronic pain and opioid addiction.

Long-term opioid treatment of chronic nonmalignant pain: unproven efficacy and neglected safety?

BACKGROUND

For the past 30 years, opioids have been used to treat chronic nonmalignant pain. This study tests the following hypotheses: (1) there is no strong evidence-based foundation for the conclusion that long-term opioid treatment of chronic nonmalignant pain is effective; and (2) the main problem associated with the safety of such treatment - assessment of the risk of addiction - has been neglected.

METHODS

Scientometric analysis of the articles representing clinical research in this area was performed to assess (1) the quality of presented evidence (type of study); and (2) the duration of the treatment phase. The sufficiency of representation of addiction was assessed by counting the number of articles that represent (1) editorials; (2) articles in the top specialty journals; and (3) articles with titles clearly indicating that the addiction-related safety is involved (topic-in-title articles).

RESULTS

Not a single randomized controlled trial with opioid treatment lasting >3 months was found. All studies with a duration of opioid treatment ≥6 months (n = 16) were conducted without a proper control group. Such studies cannot provide the consistent good-quality evidence necessary for a strong clinical recommendation. There were profound differences in the number of addiction articles related specifically to chronic nonmalignant pain patients and to opioid addiction in general. An inadequate number of chronic pain-related publications were observed with all three types of counted articles: editorials, articles in the top specialty journals, and topic-in-title articles.

CONCLUSION

There is no strong evidence-based foundation for the conclusion that long-term opioid treatment of chronic nonmalignant pain is effective. The above identified signs indicating neglect of addiction associated with the opioid treatment of chronic nonmalignant pain were present.