Pain chronification: what should a non-pain medicine specialist know?

The impact of perceived injustice on pain and psychological outcomes after traumatic injury: a longitudinal analysis

ABSTRACT

Individuals' appraisals regarding the injustice of their pain or physical injury have emerged as a significant risk factor for worse physical and psychological outcomes. Injustice appraisals are defined by perceptions of external blame for pain or injury and viewing pain or injury as a source of irreparable loss. To date, research on the impact of injustice appraisal has been primarily cross sectional, and existing longitudinal studies have examined injustice appraisals at only 2 time points in the context of rehabilitation treatment. This study examined the trajectory of injustice appraisals in 171 patients admitted for traumatic injury at admission, as well as 3, 6, and 12 months after discharge and examined injustice appraisals as a potential moderator of recovery after injury. Findings can be summarized as follows: First, injustice perception was largely stable in the 12 months after hospital discharge. Second, elevated injustice perception was associated with decreased recovery in pain intensity and depressive symptomatology over the study period but did not moderate changes in pain catastrophizing or posttraumatic stress symptomatology over time. This study is the first naturalistic prospective analysis of injustice appraisal following trauma admission within the American healthcare system. Findings indicate that injustice appraisals do not naturally decrease in the aftermath of traumatic injury and may be a risk factor for poorer physical and psychological recovery. Future research should examine additional sociodemographic and psychosocial factors that may contribute to elevated injustice appraisal, as well as ways of addressing the potential deleterious impact of injustice appraisals in treatment settings.

Assessment of the concordance between DN4 scores performed by the patient (self-assessment) or by the physician (hetero-assessment) to detect subacute neuropathic postoperative pain

BACKGROUND

Centres dedicated to chronic postsurgical pain (CPSP) have been developed, but delays for accessing to it are generally long. Teleconsultation might be a means to facilitate access to care by allowing an initial triage. CPSPs are neuropathic pain in around half of the cases and their diagnosis is mainly based on the score obtained from validated questionnaires. Among them, those requiring a neurological examination (i.e. the Douleur Neuropathique en 4 questions [DN4]) have a better sensitivity and specificity, and should be preferred. However, effectiveness of a remote neurological examination remains to be established. The aim of this observational study is to check during a face-to-face consultation if, after a short training, a naïve patient is capable to self-assess the clinical signs of neuropathic sensations.

METHODS

Thirty patients with suspected neuropathic pain were seen in a face-to-face postoperative pain consultation. Before examination, the patient was instructed to fill the DN4 questionnaire, including the neurological examination. Once explanations were given and checked, the patient was left and completed it alone. Then, the pain physician performed the DN4 questionnaire. Inter-rater reliability between patient and pain physician was assessed for each item and for DN4 score with the Kappa coefficient.

RESULTS

For each item of the DN4 questionnaire, Kappa coefficients were between 0.74 and 1, and could be considered as excellent. For DN4 ≥ 4, the Kappa coefficient was 0.86.

CONCLUSIONS

Our results suggest that after a short training, a naïve patient is capable of recognizing and diagnosing symptoms of neuropathic pain.

SIGNIFICANCE

Our results suggest that self-assessment, carried out after brief training and using a simple tool, provides results comparable to those obtained by a specialist physician to diagnose symptoms of neuropathic pain. If the results of the current study are confirmed on a larger scale, self-assessment will help improve access to specialized chronic pain care by better orienting patients and opening up access to teleconsultations.

The relationship between musicianship and pain. Is chronic pain and its management a problem for student musicians only?

Introduction

The neuro-biological side of chronic pain research has presented reliable evidence of distinct cortical and spinal alteration compared to healthy individuals. Furthermore, research suggests that musicians are especially vulnerable to pain, and recent neurological investigations into musicians' brain plasticity support this hypothesis. However, chronic pain is not acute pain plus time, but a separate condition, and little is known about musicians' chronic pain-related emotions and behaviors. This knowledge, however, is a crucial step in understanding how chronic pain is processed by musicians.

Methods

This study investigated pain catastrophizing as a critical pain-related behavior and emotional concept alongside six complementary variables: anxiety, depression, depersonalisation, burnout, coping strategies and professional identity.

Results

103 under- and postgraduate students from various higher education institutions participated in an online survey. Students were allocated into three groups according to their main study subject and type of institution: music college musicians, university musicians and university non-musicians. A tree model confirmed the current chronic pain multifactorial model, suggesting a combination of several variables before catastrophizing pain. Group testing, however, showed that university non-musicians' pain catastrophizing was significantly worse especially when compared to music college musicians. Music college musicians and university musicians were less prone to maladaptive pain processes, despite perceiving pain for significantly longer.

Discussion

This novel finding indicates that chronic pain does not inevitably lead to dysfunctional pain processing for musicians and should be reflected accordingly to optimize pain-control. The biopsychosocio model of chronic pain provides a robust framework for future research in this population.

Pain chronification impacts whole-brain functional connectivity in women with hip osteoarthritis during pain stimulation

OBJECTIVE

Previous neuroimaging studies have shown that patients with chronic pain display altered functional connectivity across distributed brain areas involved in the processing of nociceptive stimuli. The aim of the present study was to investigate how pain chronification modulates whole-brain functional connectivity during evoked clinical and tonic pain.

METHODS

Patients with osteoarthritis of the hip (n = 87) were classified into 3 stages of pain chronification (Grades I-III, Mainz Pain Staging System). Electroencephalograms were recorded during 3 conditions: baseline, evoked clinical hip pain, and tonic cold pain (cold pressor test). The effects of both factors (recording condition and pain chronification stage) on the phase-lag index, as a measure of neuronal connectivity, were examined for different frequency bands.

RESULTS

In women, we found increasing functional connectivity in the low-frequency range (delta, 0.5-4 Hz) across pain chronification stages during evoked clinical hip pain and tonic cold pain stimulation. In men, elevated functional connectivity in the delta frequency range was observed in only the tonic cold pain condition.

CONCLUSIONS

Across pain chronification stages, we found that widespread cortical networks increase their synchronization of delta oscillations in response to clinical and experimental nociceptive stimuli. In view of previous studies relating delta oscillations to salience detection and other basic motivational processes, our results hint at these mechanisms playing an important role in pain chronification, mainly in women.

The combined effects of coping and pain interference on army readiness

Introduction

Chronic pain and associated interference with daily activities are common in the military and impact Force readiness. Chronic pain affects one-third of service members and is a leading cause of medical non-readiness (MNR) in the military. Research suggests that underlying psychological mechanisms related to trait coping styles and pain interference (PI) affect functional outcomes, but little research exists examining this relationship within an Army population. The purpose of this study was to examine the combined effects of PI and coping on U.S. Army soldier readiness by using annual well-being data from the Global Assessment Tool (GAT) and medical non-readiness (MNR) based on duty restriction records.

Methods

The sample comprised 866,379 soldiers who completed the GAT between 2014 and 2017 with no duty restrictions at the time of baseline GAT completion; subjects were observed through 2018 for duty restrictions. Parametric survival regression models with a Weibull distribution predicted demographic-adjusted hazards of MNR by dichotomized PI (no PI/PI) and beneficial/non-beneficial use of GAT coping components (good coping, bad coping, catastrophizing-flexibility, and catastrophizing-hopelessness). Incident MNR was evaluated for all duty restrictions, and stratified by selected body systems (upper extremity, lower extremity, psychiatric).

Results

Among soldiers with PI, hazards were higher in those reporting non-beneficial coping styles (bad coping, hopelessness) and lower in those reporting beneficial coping styles (good coping, flexibility). Across all coping styles, PI/coping interactions were particularly strong for catastrophizing-hopelessness and when examining MNR from psychiatric conditions.

Discussion

These findings suggest some synergistic associations between pain and coping that may impact pain-related occupational disability. Coping skills may be an effective interventional target for chronic pain reduction/prevention within military programs, such as the Master Resilience Training Course offered to soldiers in the Army. Further research should assess whether early coping style interventions can reduce pain-related outcomes.

Relationship between Time Elapsed Since Pain Onset and Efficacy of Pain Relief in Patients Undergoing Lumbar Percutaneous Epidural Adhesiolysis

PURPOSE

The aim of this study was to investigate the relationship between pain duration and pain relief after epidural adhesiolysis.

MATERIALS AND METHODS

Patients with low back pain who underwent lumbar epidural adhesiolysis were enrolled. A clinically significant reduction in pain score was defined as a ≥30% reduction at 6-month follow-up evaluation. Variables were compared based on pain duration categories. Changes in pain scores and pain outcome were also compared. Logistic regression analysis was conducted to identify factors associated with pain relief after adhesiolysis.

RESULTS

A total of 169 patients, including 77 (45.6%) patients with a favorable pain outcome, were included for analysis. Patients with a pain duration ≥3 years reported lower baseline pain scores and showed more frequent severe central stenosis. Pain scores significantly decreased over time after the procedure except in patients with a pain duration ≥3 years. Most patients who experienced pain for ≥3 years showed poor pain relief (80.8%), unlike other pain duration categories (pain duration <3 months=48.1%, 3 months-1 year=51.8%, 1-3 years=48.6%). A pain duration ≥3 years and lower baseline pain score were independent factors associated with an unfavorable pain outcome.

CONCLUSION

Pain lasting ≥3 years prior to lumbar epidural adhesiolysis was associated with worse outcomes in terms of pain relief. Therefore, this intervention should be considered early before pain chronification in patients with low back pain.

Altered social decision making in patients with chronic pain

BACKGROUND

Chronic pain affects up to 20% of the population, impairs quality of life and reduces social participation. Previous research reported that pain-related perceived injustice covaries with these negative consequences. The current study probed whether chronic pain patients responded more strongly to disadvantageous social inequity than healthy individuals.

METHODS

We administered the Ultimatum Game, a neuroeconomic social exchange game, where a sum of money is split between two players to a large sample of patients with chronic pain disorder with somatic and psychological factors (n = 102) and healthy controls (n = 101). Anonymised, and in truth experimentally controlled, co-players proposed a split, and our participants either accepted or rejected these offers.

RESULTS

Chronic pain patients were hypersensitive to disadvantageous inequity and punished their co-players for proposed unequal splits more often than healthy controls. Furthermore, this systematic shift in social decision making was independent of patients' performance on tests of executive functions and risk-sensitive (non-social) decision making .

CONCLUSIONS

Our findings indicate that chronic pain is associated with anomalies in social decision making (compared to healthy controls) and hypersensitivity to social inequity that is likely to negatively impact social partaking and thereby the quality of life.

Factors Associated with Low Inter-Session Reliability of Conditioned Pain Modulation in Older People with or Without Chronic Musculoskeletal Pain

Purpose

Conditioned pain modulation (CPM) is a measurement of the descending pain pathways that inhibit or facilitate afferent noxious stimuli. The reliability of CPM in older individuals with or without chronic musculoskeletal pain has not been sufficiently reported. This study aimed to examine the inter-session reliability of CPM in these cohorts and the factors in CPM reliability.

Patients and Methods

Individuals aged 65 or older were recruited in Narita, Japan. The measurements were performed on separate days 2 weeks apart (sessions 1 and 2). Each participant's hand was immersed in cold water, and we measured pressure pain threshold (PPT) before and after the immersion. The ratio before and after PPT measurements was presented as CPM index. The autonomic activities (heart rate variability, heart rate, and blood pressure) were simultaneously measured. An absolute reliability of CPM index was analyzed by the adjusted two-way analysis of variance (ANOVA) and the Bland Altman plot, and relative reliability was analyzed by intraclass correlation coefficient (ICC). Spearman's rho correlation and the adjusted multivariate regression analysis were utilized for examining the CPM reliability factors.

Results

Thirty-two participants were divided into two groups: chronic pain (n=19) and non-chronic pain (n=13) groups. The mean difference between session 1 and 2 in CPM index showed a systematic error in the chronic pain group at 17.3 (confidence interval, CI: 15.0 to 19.7), but none in the non-chronic pain group at 3.7 (CI: -0.02 to 7.4). The adjusted two-way ANOVA for CPM index did not identify any differences. ICC was not significant at p=-0.247 in the non-chronic and 0.167 in chronic pain. Multivariate regression analysis revealed total power and low/high frequencies as significant factors for CPM index.

Conclusion

This study identified low inter-session reliability in older adults with chronic musculoskeletal pain and autonomic nervous system activities as factors in CPM reliability.

Artificial Neural Networks Coupled with MALDI-TOF MS Serum Fingerprinting To Classify and Diagnose Pathological Pain Subtypes in Preclinical Models

Pathological pain subtypes can be classified as either neuropathic pain, caused by a somatosensory nervous system lesion or disease, or nociplastic pain, which develops without evidence of somatosensory system damage. Since there is no gold standard for the diagnosis of pathological pain subtypes, the proper classification of individual patients is currently an unmet challenge for clinicians. While the determination of specific biomarkers for each condition by current biochemical techniques is a complex task, the use of multimolecular techniques, such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), combined with artificial intelligence allows specific fingerprints for pathological pain-subtypes to be obtained, which may be useful for diagnosis. We analyzed whether the information provided by the mass spectra of serum samples of four experimental models of neuropathic and nociplastic pain combined with their functional pain outcomes could enable pathological pain subtype classification by artificial neural networks. As a result, a simple and innovative clinical decision support method has been developed that combines MALDI-TOF MS serum spectra and pain evaluation with its subsequent data analysis by artificial neural networks and allows the identification and classification of pathological pain subtypes in experimental models with a high level of specificity.

Systematic review and meta-analysis on the association between chronic low back pain and cognitive function

This study aimed to identify and assess the evidence on the association between idiopathic chronic low back pain (LBP) and cognitive function in individuals with LBP. A secondary aim was to explore whether changes in cognitive function are associated with pain characteristics and psychological factors (eg, catastrophizing and fear of movement). Eleven studies were included in this systematic review, and four meta-analyses were conducted. Low to very low-quality evidence suggests impaired cognitive function in individuals with LBP compared to asymptomatic controls for problem solving (k = 5; d = 0.33; CI = 0.16-0.50; z = 3.85 p = 0.0001), speed of information processing (k = 5; d = 0.44; CI = 0.22-0.65; z = 4.02 p < 0.0001), working memory (k = 6; d = 0.50; CI = 0.34-0.66; z = 6.09 p < 0.0001), and delayed memory (k = 3; d = 0.34; CI = 0.07-0.6, z = 2.49 p = 0.02). The association between LBP intensity and psychological factors and cognitive function was inconclusive. More studies are needed to explore these associations and improve evidence in this field. The results of this study suggest that cognitive aspects should be considered during the rehabilitation process of patients with LBP and raise further questions, including whether individuals with LBP are at a greater risk of developing dementia or whether targeting cognitive function will increase the probability of success of LBP treatment. These questions should, also, be considered in future studies.

The Impact of P-Glycoprotein on Opioid Analgesics: What's the Real Meaning in Pain Management and Palliative Care?

Opioids are widely used in cancer and non-cancer pain management. However, many transporters at the blood-brain barrier (BBB), such as P-glycoprotein (P-gp, ABCB1/MDR1), may impair their delivery to the brain, thus leading to opioid tolerance. Nonetheless, opioids may regulate P-gp expression, thus altering the transport of other compounds, namely chemotherapeutic agents, resulting in pharmacoresistance. Other kinds of painkillers (e.g., acetaminophen, dexamethasone) and adjuvant drugs used for neuropathic pain may act as P-gp substrates and modulate its expression, thus making pain management challenging. Inflammatory conditions are also believed to upregulate P-gp. The role of P-gp in drug-drug interactions is currently under investigation, since many P-gp substrates may also act as substrates for the cytochrome P450 enzymes, which metabolize a wide range of xenobiotics and endobiotics. Genetic variability of the ABCB1/MDR1 gene may be accountable for inter-individual variation in opioid-induced analgesia. P-gp also plays a role in the management of opioid-induced adverse effects, such as constipation. Peripherally acting mu-opioid receptors antagonists (PAMORAs), such as naloxegol and naldemedine, are substrates of P-gp, which prevent their penetration in the central nervous system. In our review, we explore the interactions between P-gp and opioidergic drugs, with their implications in clinical practice.

Pain "chronification": what is the problem with this model?

OBJECTIVES

There appears to be an unwarranted focus on all chronic pain being a "chronification" of acute pain. Despite a plethora of studies on mechanisms to prevent this "chronification" following surgery, the positive effects have been minimal. An alternate model to explain chronic pain is presented.

METHODS

Research in PUBMED and accessing data from the HUNTpain examination study.

RESULTS

Data from the HUNT pain examination study reveal that less than 25% of individuals with chronic pain in a general population can relate the onset to an acute event. Another theory explaining the origin of chronic pain is that of priming and the accumulation of events that can be predictors along a continuum before chronic pain is apparent. This theory is presented to refocus for better prevention and treatment of chronic pain.

CONCLUSIONS

"Chronification" cannot explain all cases of chronic/persistent pain. The plastic changes in the pain processing system can be seen as a continuum where at some point where an acute pain event is only one of several possible tipping points on this continuum that changes potential pain to perceived pain.

Pain is Not a "thing": How That Error Affects Language and Logic in Pain Medicine

Effectiveness in academic and clinical communication depends upon agreement on what words and concepts denote and on the consequent ability to argue logically and accurately. In the pain medicine literature there are many examples of imprecision and confusion in this respect, including misnomers and fallacies in reasoning. This article firstly critically examines some of these misnomers. Identified themes include pain being conceptualised as a "thing," conflation between nociception and pain, and confusion between stimulus and response and between the perspectives of the experiencer and the observer of "pain." Secondly, fallacies in reasoning are identified that contribute to imprecision and confusion. These include reification of pain, attributing to the brain functions that belong to whole organisms, and the illusory truth effect. Thirdly, these themes are identified also in constructs that are shown to be based more on speculation than on fact. Taken together, these observations reveal a need to review and, where necessary, modify terminology and concepts used in Pain Medicine. PERSPECTIVE: This article examines a number of words and constructs commonly found in the pain literature from the perspective of accuracy in terms of their consistency of usage, concordance with fact, degree of speculation and logical argument. A common major theme is the error of considering pain as a "thing" that has agentive properties. A need to clarify much of the language used in Pain Medicine is identified.

Limited prognostic value of pain duration in non-specific neck pain patients seeking chiropractic care

BACKGROUND

Pain chronicity is considered an important prognostic factor for outcome. Here, it was investigated whether pain duration influences outcome when only chronic patients (pain > three months) are considered. Secondary aims were to determine, in patients of any pain duration, how much variance in outcome is explained by pain duration and whether pain duration truly predicts outcomes, i.e. out-of-sample prediction in independent data.

METHODS

Secondary analysis of a cohort study of neck pain patients. Patients were assessed before start of treatment and at one week, one, three, six- and 12-months follow-up. Outcomes were Patient Global Impression of Change (PGIC) and percent change of patients' perceived pain intensity, rated on a numerical rating scale (NRS). Regression analyses (linear and logistic) and supervised machine learning were used to test the influence of pain duration on PGIC and percent NRS change at one week, one, three, six- and 12-months follow-up within sample and out-of-sample. Separate analyses were performed for the full sample (n=720) and for chronic patients (n=238) only.

RESULTS

No relationship between pain duration and outcome was found for chronic patients only. For the full sample, statistical relationships between pain duration and outcomes were observed at all tested follow-up time points. However, the amount of variance in outcome explained by pain duration was low and no out-of-sample prediction was possible.

CONCLUSIONS

Pain duration did not emerge as an important predictor of outcome in this database of 720 neck pain patients receiving chiropractic treatment.

Paracetamol for multimodal analgesia

Pain and related disability remain a major social and therapeutic problem. Comorbidities and therapies increase drug interactions and side effects making pain management more compounded especially in the elderly who are the fastest-growing pain population. Multimodal analgesia consists of using two or more drugs and/or techniques that target different sites of pain, increasing the level of analgesia and decreasing adverse events from treatment. Paracetamol enhances multimodal analgesia in experimental and clinical pain states. Strong preclinical evidence supports that paracetamol has additive and synergistic interactions with anti-inflammatory, opioid and anti-neuropathic drugs in rodent models of nociceptive and neuropathic pain. Clinical studies in young and adult elderly patients confirm the utility of paracetamol in multimodal, non-opioid or opioid-sparing, therapies for the treatment of acute and chronic pain.

Reimagining How We Treat Acute Pain: A Narrative Review

Acute pain may be influenced by biopsychosocial factors. Conditioned pain modulation, distraction, peripheral nerve stimulation, and cryoneurolysis may be helpful in its treatment. New developments in opioids, such as opioids with bifunctional targets and oliceridine, may be particularly suited for acute pain care. Allosteric modulators can enhance receptor subtype selectivity, offering analgesia with fewer and/or less severe side effects. Neuroinflammation in acute pain is caused by direct insult to the central nervous system and is distinct from neuroinflammation in degenerative disorders. Pharmacologic agents targeting the neuroinflammatory process are limited at this time. Postoperative pain is a prevalent form of acute pain and must be recognized as a global public health challenge. This type of pain may be severe, impede rehabilitation, and is often under-treated. A subset of surgical patients develops chronic postsurgical pain. Acute pain is not just temporally limited pain that often resolves on its own. It is an important subject for further research as acute pain may transition into more damaging and debilitating chronic pain. Reimagining how we treat acute pain will help us better address this urgent unmet medical need. 

Considerations for Better Management of Postoperative Pain in Light of Chronic Postoperative Pain: A Narrative Review

Chronic postoperative pain (CPOP) is prevalent, with particularly high rates in breast surgery, thoracotomy, and amputation. As the world emerges from the coronavirus disease 2019 (COVID-19) lockdowns, it is expected that there will be an increase in surgical procedures, elevating the importance of preventing CPOP in the coming years. Risk factors are emerging to better stratify patients at high risk for CPOP. Perioperative analgesia plays an important role in managing acute postoperative pain and in some cases may limit its transition to CPOP. Acute postoperative pain is adaptive, normal, expected, and has a well-defined trajectory, while CPOP is maladaptive and, as a form of chronic pain, is challenging to treat. Good analgesia, early ambulation, and rehabilitation efforts may be helpful in preventing CPOP following certain surgeries. Enhanced Recovery After Surgery (ERAS) protocols present guidance to help promote recovery and prevent CPOP.

Analgesic efficacy of naproxen sodium versus hydrocodone/acetaminophen in acute postsurgical dental pain: a randomized, double-blind, placebo-controlled trial

OBJECTIVES

Opioid/acetaminophen combinations may be overly prescribed in many post-surgical situations where a non-steroidal anti-inflammatory drug with equal or greater efficacy, fewer central nervous system side effects, and no risk for opioid abuse could be substituted. We compared a single, non-prescription dose of naproxen sodium 440 mg (NapS) against hydrocodone plus acetaminophen 10/650 mg (HYD+APAP) in post-impaction surgery pain.

METHODS

Single-center, randomized, double-blind, placebo-controlled study in moderate-severe pain after surgical removal of impacted third molars (ClinicalTrials.gov: NCT04307940). Patients (n = 212) received NapS, HYD+APAP, or placebo and were assessed over 12 hours. Primary endpoint: summed pain intensity difference from 0 to 12 hours (SPID_0-12). Secondary endpoints: pain intensity, pain relief, time to rescue medication, duration of pain at least half gone. Others: onset of pain relief, global assessment of treatment, adverse events.

RESULTS

All 221 randomized patients formed the safety population and were included in the intention-to-treat sensitivity analysis. Nine patients discontinued treatment or had protocol violations, and 212 patients were included in the per-protocol, primary efficacy population. Both active treatments were significantly more effective than placebo. NapS was significantly more effective than HYD+APAP regarding SPID_0-12 (p = 0.01; primary endpoint), total pain relief (0-6 and 0-12 hours; p < 0.05), time to rescue medication (p < 0.001), and duration of pain at least half gone (p < 0.001). HYD+APAP was not statistically superior to NapS for any endpoint. More adverse events were reported with HYD+APAP (n = 63) than NapS (n = 2) and placebo (n = 20), including nausea, vomiting, and dizziness.

CONCLUSION

In moderate-to-severe postsurgical dental pain, a single dose of NapS was at least as effective as HYD+APAP in the early hours, significantly more effective at reducing pain intensity and providing greater pain relief over 12 hours, and was better tolerated. When not contraindicated, NapS should be considered a preferred alternative to opioid combinations for acute pain. (ClinicalTrials.gov, Identifier: NCT04307940; https://clinicaltrials.gov/ct2/show/NCT04307940).

Chronic pain in the 11th revision of the International Classification of Diseases: users' questions answered

ABSTRACT

The upcoming 11th revision of the International Classification of Diseases (ICD-11) will include a comprehensive classification of chronic pain for the first time, which is based on the biopsychosocial definition of chronic pain. This presents a great opportunity for pain research and clinical practice. The new classification consists of seven main diagnostic categories of chronic pain, which are further divided into increasingly specific levels of diagnoses. Each diagnosis is characterized by clearly defined operationalized criteria. Future users will need to familiarize themselves with the new system and its application. The aim of the present publication is to provide users of the ICD-11 chronic pain classification with answers to frequently asked questions regarding the ICD-11 as a whole, the ICD-11 chronic pain classification, and its application to common pain syndromes. The questions compiled here reached the International Association for the Study of Pain Task Force via different routes (e.g., at conferences, by letter, or during field testing). Furthermore, the authors collected questions posted to the ICD-11 browser and contacted early users of the classification to enquire about their most frequent difficulties when applying the new diagnoses. The authors of the present publication prepared answers to these frequently asked questions. This publication intends to act as a guide for the future users of the new ICD-11 chronic pain classification, hence facilitating its implementation.

Open Issues and Practical Suggestions for Telemedicine in Chronic Pain

Telemedicine represents a major opportunity to facilitate continued assistance for patients with chronic pain and improve their access to care. Preliminary data show that an improvement can be expected of the monitoring, treatment adherence, assessment of treatment effect including the emotional distress associated with pain. Moreover, this approach seems to be convenient and cost-effective, and particularly suitable for personalized treatment. Nevertheless, several open issues must be highlighted such as identification of assessment tools, implementation of monitoring instruments, and ability to evaluate personal needs and expectations. Open questions exist, such as how to evaluate the need for medical intervention and interventional procedures, and how to define when a clinical examination is required for certain conditions. In this context, it is necessary to establish dynamic protocols that provide the right balance between face-to-face visits and telemedicine. Useful tips are provided to start an efficient experience. More data are needed to develop precise operating procedures. In the meantime, the first experiences from such settings can pave the way to initiate effective care pathways in chronic pain.

Association of chronic pain with comorbidities and health care utilization: a retrospective cohort study using health administrative data

ABSTRACT

Health administrative data provide a potentially robust information source regarding the substantial burden chronic pain exerts on individuals and the health care system. This study aimed to use health administrative data to estimate comorbidity prevalence and annual health care utilization associated with chronic pain in Newfoundland and Labrador, Canada. Applying the validated Chronic Pain Algorithm to provincial Fee-for-Service Physician Claims File data (1999-2009) established the Chronic Pain (n = 184,580) and No Chronic Pain (n = 320,113) comparator groups. Applying the Canadian Chronic Disease Surveillance System coding algorithms to Claims File and Provincial Discharge Abstract Data (1999-2009) determined the prevalence of 16 comorbidities. The 2009/2010 risk and person-year rate of physician and diagnostic imaging visits and hospital admissions were calculated and adjusted using the robust Poisson model with log link function (risks) and negative binomial model (rates). Results indicated a significantly higher prevalence of all comorbidities and up to 4 times the odds of multimorbidity in the Chronic Pain Group (P-value < 0.001). Chronic Pain Group members accounted for 58.8% of all physician visits, 57.6% of all diagnostic imaging visits, and 54.2% of all hospital admissions in 2009/2010, but only 12% to 16% of these were for pain-related conditions as per recorded diagnostic codes. The Chronic Pain Group had significantly higher rates of physician visits and high-cost hospital admission/diagnostic imaging visits (P-value < 0.001) when adjusted for demographics and comorbidities. Observations made using this methodology supported that people identified as having chronic pain have higher prevalence of comorbidities and use significantly more publicly funded health services.

Acute effects of proprioceptive neuromuscular facilitation exercises on the postural strategy in patients with chronic low back pain

INTRODUCTION

Active treatments focused on improvement in motor function are postulated in chronic low back patients (CLBP).

OBJECTIVE

to establish the acute effects of PNF exercise on the postural control strategy.

METHODS

The sway of the body was tested before intervention in fifty-three CLBP patients and after that participants were randomly assigned into the intervention PNF group (n = 25). Mean velocity (VEL) and sample entropy (SEn), over the center of pressure in the mediolateral (ML) and anterior-posterior (AP) planes served to estimate the postural strategy and automaticity levels in the neuromuscular controller. Tandem and one-leg standing tests (OLST) with eyes open and eyes closed were used.

RESULTS

Pain intensity decreased after the intervention. The VEL was no longer vision-dependent in both planes. The SEn decreased immediately after the exercise and either returned to or even exceeded the baseline values in the OLST ML plane.

CONCLUSION

A single session of PNF exercise may have a beneficial effect on pain and postural control in CLBP patients. The statistically significant pain relief combined with newly acquired better control of posture may have encouraged the PNF group participants to a subconscious exploration of the stability area. Postural movements were more automatized in OLST in the delayed test.

Left to themselves: Time to target chronic pain in childhood rare diseases

BACKGROUND

Chronic pain is prevalent among patients with rare diseases (RDs). However, little is understood about how biopsychosocial mechanisms may be integrated in the unique set of clinical features and therapeutic challenges inherent in their pain conditions.

METHODS

This review presents examples of major categories of RDs with particular pain conditions. In addition, we provide translational evidence on clinical and scientific rationale for psychosocially- and neurodevelopmentally-informed treatment of pain in RD patients.

RESULTS

Neurobiological and functional overlap between various RD syndromes and pain states suggests amalgamation and mutual modulation of the respective conditions. Emotional sequelae could be construed as an emotional homologue of physical pain mediated via overlapping brain circuitry. Given their clearly defined genetic and molecular etiologies, RDs may serve as heuristic models for unraveling pathophysiological processes inherent in chronic pain.

CONCLUSIONS

Systematic evaluation of chronic pain in patients with RD contributes to sophisticated insight into both pain and their psychosocial correlates, which could transform treatment.

Does Pain Acceptance Buffer the Negative Effects of Catastrophizing on Function in Individuals With Chronic Pain?

OBJECTIVES

Pain catastrophizing and pain acceptance are psychological factors that have been shown to be associated with pain-related outcomes and predict multidisciplinary pain treatment outcomes. However, they are rarely examined in the same study. This study aimed to: (1) assess the independent roles of pain catastrophizingand pain acceptance as predictors of pain intensity, pain interference, and depression; and (2) evaluate the potential moderating role of pain acceptance on the association between pain catastrophizing and both pain and function.

MATERIALS AND METHODS

A sample of 467 adults with chronic pain completed an online survey including measures of pain intensity, pain interference, depression, pain catastrophizing, and pain acceptance.

RESULTS

Pain catastrophizing and pain acceptance were independent predictors of pain interference. Only pain catastrophizing and the activity engagement domain of pain acceptance were independent predictors of pain intensity and depression. Activity engagement moderated the association between pain catastrophizing and depression, indicating a buffering effect on the negative effects of catastrophizing on depression. Pain willingness moderated the association between pain catastrophizing and pain interference, such that endorsing low pain willingness may override any negative effects of pain catastrophizing.

DISCUSSION

The findings suggest that pain catastrophizing and pain acceptance are independently important to adjustment to chronic pain. Research is needed to determine if treatments that target both for change are more effective than treatments that target only one.

Severe chronic low back pain: patient journey from onset of symptoms to strong opioid treatments in Europe

Aim: We report the first patient roadmap in severe chronic low back pain (cLBP) in Europe, assessing the views of cLBP patients and general practitioners (GPs) who treat cLBP with regard to current cLBP management. Methodology: Patient journey mapping was conducted in four European countries to assess the views of cLBP patients (n = 20) and GPs (n = 40). Results: Four broad phases of cLBP, subdivided into eight individual steps, were identified as part of the patient journey, showing a disconnect between patients' and physicians' treatment goals, and expectations regarding pain relief levels for some patients. Conclusion: Improved communication, with greater involvement of patients in multimodal management decisions, might benefit the GP-patient relationship and overall outcomes for cLBP patients.

Antinociceptive Effect of Lodenafil Carbonate in Rodent Models of Inflammatory Pain and Spinal Nerve Ligation-Induced Neuropathic Pain

Introduction

New therapeutic alternatives for pain relief include the use of phosphodiesterase-5 (PDE5) inhibitors, which could prevent the transmission of painful stimuli by neuron hyperpolarization via nitric oxide (NO)/cyclic 3',5'-guanosine monophosphate (cGMP) pathway. The present work investigated the antinociceptive activity of a new PDE5 inhibitor, lodenafil carbonate, in inflammatory and neuropathic pain models.

Methods and Results

Although no effect was detected on neurogenic phase of formalin test in mice, oral administration of lodenafil carbonate dose-dependently reduced reactivity in the inflammatory phase (200.6 ± 39.1 to 81.9 ± 18.8 s at 10 μmol/kg, p= 0.0172) and this effect was totally blocked by NO synthase inhibitor, L-Nω-nitroarginine methyl ester (L-NAME). Lodenafil carbonate (10 μmol/kg p.o.) significantly reduced nociceptive response as demonstrated by increased paw withdrawal latency to thermal stimulus (from 6.8 ± 0.7 to 10.6 ± 1.3 s, p= 0.0006) and paw withdrawal threshold to compressive force (from 188.0 ± 14.0 to 252.5 ± 5.3 g, p<0.0001) in carrageenan-induced paw inflammation model. In a spinal nerve ligation-induced neuropathic pain, oral lodenafil carbonate (10 μmol/kg) also reversed thermal hyperalgesia and mechanical allodynia by increasing paw withdrawal latency from 17.9 ± 1.5 to 22.8 ± 1.9 s (p= 0.0062) and paw withdrawal threshold from 26.0 ± 2.8 to 41.4 ± 2.9 g (p= 0.0196). These effects were reinforced by the reduced GFAP (3.4 ± 0.5 to 1.4 ± 0.3%, p= 0.0253) and TNF-alpha (1.1 ± 0.1 to 0.4 ± 0.1%, p= 0.0111) stained area densities as detected by immunofluorescence in ipsilateral dorsal horns.

Conclusion

Lodenafil carbonate demonstrates important analgesic activity by promoting presynaptic hyperpolarization and preventing neuroplastic changes, which may perpetuate chronic pain, thus representing a potential treatment for neuropathic pain.

Peripheral Mechanisms of Neuropathic Pain-the Role of Neuronal and Non-Neuronal Interactions and Their Implications for Topical Treatment of Neuropathic Pain

Neuropathic pain in humans arises as a consequence of injury or disease of somatosensory nervous system at peripheral or central level. Peripheral neuropathic pain is more common than central neuropathic pain, and is supposed to result from peripheral mechanisms, following nerve injury. The animal models of neuropathic pain show extensive functional and structural changes occurring in neuronal and non-neuronal cells in response to peripheral nerve injury. These pathological changes following damage lead to peripheral sensitization development, and subsequently to central sensitization initiation with spinal and supraspinal mechanism involved. The aim of this narrative review paper is to discuss the mechanisms engaged in peripheral neuropathic pain generation and maintenance, with special focus on the role of glial, immune, and epithelial cells in peripheral nociception. Based on the preclinical and clinical studies, interactions between neuronal and non-neuronal cells have been described, pointing out at the molecular/cellular underlying mechanisms of neuropathic pain, which might be potentially targeted by topical treatments in clinical practice. The modulation of the complex neuro-immuno-cutaneous interactions in the periphery represents a strategy for the development of new topical analgesics and their utilization in clinical settings.

Dual-Acting Peripherally Restricted Delta/Kappa Opioid (CAV1001) Produces Antinociception in Animal Models of Sub-Acute and Chronic Pain

Background

The development of highly efficacious alternatives to mu-opioid analgesics represents an urgent unmet medical and public health need. In the presence of inflammation both delta- and kappa-opioid agonists, acting on peripheral sensory neurons, mediate analgesia. The dual-acting, peripherally restricted kappa/delta-opioid agonist, CAV1001, was tested in four rodent pain models.

Methods

Experiment 1 – Formalin testing in mice. Three doses (1–10 mg/kg) of CAV1001 or ICI204448 at 30 minutes were tested after formalin injection. Spontaneous nocifensive responses were video recorded. Experiment 2 – Complete Freund’s Adjuvant (CFA)-induced arthritis. CFA was injected into the ankle joint of rats. Joint compression thresholds (JCT) were measured. CAV1001 was compared to celecoxib. Experiment 3 – Spinal nerve ligation (SNL) in rats. Paw compression thresholds (PCT) were measured. CAV1001 was compared to gabapentin. Experiment 4 – MMRT-1 bone cancer implantation into the rat tibia. Weight-bearing was assessed. CAV1001 was compared to morphine.

Results

In Phase 2 of the formalin model, CAV1001 (1 mg/kg) significantly reduced pain behaviors to a degree comparable to the peripherally restricted kappa-opioid agonist, ICI204448 (10 mg/kg). CAV1001 (10 mg/kg) effectively eliminated pain behaviors associated with phase 2. In the CFA-induced arthritis model, a significant increase in JCTs, similar to the comparator celecoxib, was observed with CAV1001 at 1 mg/kg at 2 hours; CAV1001 (10 mg/kg) was effective at 1 hour. In the SNL model, both the comparator gabapentin and CAV1001 (5 mg/kg) significantly reduced PCT at 2 hours, but at 4 hours, the CAV1001 thresholds improved to baseline. CAV1001 10 mg/kg significantly improved weight bearing at 4-hour post-dosing compared to baseline following MMRT-1 implantation.

Conclusion

CAV1001 demonstrated efficacy in several different preclinical pain models. Time- and dose-dependent differences in the efficacy of CAV1001 amongst these rodent pain models parallel the degree of underlying inflammation.

Studies on isolation, characterization of fucoidan from brown algae Turbinaria decurrens and evaluation of it's in vivo and in vitro anti-inflammatory activities

In the present study, the anti-nociception and anti-inflammatory activity of fucoidan isolated from T. decurrens on formalin induced paw-edema in mice model were investigated. The extracted fucoidan contain 54.86% of total sugar, 23.51% of sulfate and 3.4% of protein. The monosaccharide composition analysis revealed that fucoidan encompassed of fucose (59.3%), galactose (12.6%), mannose (9.6%), rhamnose (6.4%) and xylose (11.4%). Further, the structural characterization was done by UV-visible spectroscopy, X-ray diffraction, FT-IR and 1HNMR analysis. The fucoidan reduced the licking time thereby suggesting anti-nociceptive effect and decreased the size of paw swelling in the formalin induced inflammatory edema condition. The isolated fucoidan could significantly decreased the MDA and also increase the SOD, CAT, GPx, GST and GSH activity in paw edema tissue of formalin injected mice. Furthermore, fucoidan administration retained p65/NF-κB transcription factor in the cytosol thereby showing down regulation of the gene expression of pro-inflammatory mediators such as IL-1β, COX-2 and MMP-9 in fucoidan treated mice. The anti-inflammatory effect of fucoidan was attributed to its capacity on modulating the levels of enzymatic antioxidants, master regulator NF-κB and pro-inflammatory cytokines. The fucoidan has reduced LPS induced cytotoxicity in IC-21 macrophage at a dose depended on manner.

Developments in combined analgesic regimens for improved safety in postoperative pain management

Introduction: Fixed-dose combination analgesic regimens may be similarly effective to opioid monotherapy but with potentially less risk. A number of individualized combination regimens can be created, including nonopioid agents such as acetaminophen and nonsteroidal anti-inflammatory drugs, opioids, and adjunctive agents such as gabapentin, pregabalin, and muscle relaxants. Areas covered: When such combinations have a synergistic effect, analgesic benefits may be enhanced. Many combination analgesic regimens are opioid sparing, which sometimes but not always results in reduced opioid-associated side effects. Safety concerns for all analgesics must be considered but postoperative analgesia is typically administered for a brief period (days), reducing risks that may occur with prolonged exposure. Expert opinion: Judiciously considered combination analgesic regimens can be effective postoperative analgesics that reduce opioid consumption without compromising pain control, which are important factors for patient recovery and satisfaction. The specific combinations used must be based on the patient, the type and duration of the surgical procedure, and complementary mechanisms of action of the agents used. In opioid-sparing combination analgesic regimens, the short-term use of small doses of opioids in this setting may be helpful for appropriate patients.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an opioid characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action, since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol limits the risk of opioid-related adverse events, such as gastrointestinal disturbances. Moreover, the NA component becomes predominant, at least, in some types of pain, with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of severe uncontrolled chronic pain characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an analgesic molecule characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol has two important consequences: first, it limits the risk of opioid-related adverse events, as well as the risk of dependence; second, the NA component becomes predominant at least in some types of pain with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of chronic pain conditions characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Tapentadol prolonged release for managing moderate to severe chronic neck pain with or without a neuropathic component

Background: Despite the high prevalence of neck pain, few studies have addressed the pharmacological treatment of this condition.Purpose: We evaluated the effectiveness of tapentadol prolonged-release (PR) in patients with or without a neuropathic pain component, with a focus on functional movements, disability and Quality of Life (QoL).Study design/setting: Observational, retrospective study.Patient sample: Ninety-four adult patients with severe neck pain not responsive to opioid step III treatment.Outcome measures: The primary endpoint was a ≥ 30% improvement of pain intensity at 4 weeks (W4). Several secondary outcomes were evaluated, including neck disability index (NDI), range of motion (ROM), and QoL.Methods: Patients received tapentadol PR at the starting dose of 100 mg/day. Dose titration was allowed in 50 mg increments, up to 500 mg daily.Results: At W4, the primary endpoint of ≥30% improvement of pain was reported in 70% (n = 35; 95% confidence interval [CI]: 55-82%) of patients with a neuropathic pain component and in 69% (n = 20; 95% CI: 49-85%) of those without a neuropathic component. The percentage of patients reporting a neuropathic pain component significantly decreased from baseline (64.2%) to W4 (27.8%). NDI significantly improved in both groups at W12. ROM significantly improved in all three planes of motion (p < .01), with no difference between the two groups. Interference of pain with sleep and QoL also improved.Conclusions: The reduction in pain provided by tapentadol is associated with functional recovery, which may in turn be linked to an improvement in QoL.

The Feasibility and Effectiveness of a New Practical Multidisciplinary Treatment for Low-Back Pain: A Randomized Controlled Trial

Low-back pain is a major health problem exacerbated by the fact that most treatments are not suitable for self-management in everyday life. Particularly, interdisciplinary programs consist of intensive therapy lasting several weeks. Additionally, therapy components are rarely coordinated regarding reinforcing effects, which would improve complaints in persons with higher pain. This study assesses the effectiveness of a self-management program, firstly for persons suffering from higher pain and secondly compared to regular routines. Study objectives were treated in a single-blind multicenter controlled trial. A total of n = 439 volunteers (age 18-65 years) were randomly assigned to a twelve-week multidisciplinary sensorimotor training (3-weeks-center- and 9-weeks-homebased) or control group. The primary outcome pain (Chronic-Pain-Grade) as well as mental health were assessed by questionnaires at baseline and follow-up (3/6/12/24 weeks, M2-M5). For statistical analysis, multiple linear regression models were used. N = 291 (age 39.7 ± 12.7 years, female = 61.1%, 77% CPG = 1) completed training (M1/M4/M5), showing a significantly stronger reduction of mental health complaints (anxiety, vital exhaustion) in people with higher than those with lower pain in multidisciplinary treatment. Compared to regular routines, the self-management-multidisciplinary treatment led to a clinically relevant reduction of pain-disability and significant mental health improvements. Low-cost exercise programs may provide enormous relief for therapeutic processes, rehabilitation aftercare, and thus, cost savings for the health system.

Pain Management in Patients with Multiple Myeloma: An Update

Most patients with multiple myeloma (MM) suffer from chronic pain at every stage of the natural disease process. This review focuses on the most common causes of chronic pain in MM patients: (1) pain from myeloma bone disease (MBD); (2) chemotherapy-induced peripheral neuropathy as a possible consequence of proteasome inhibitor therapy (i.e., bortezomib-induced); (3) post-herpetic neuralgia as a possible complication of varicella zoster virus reactivation because of post-transplantation immunodepression; and (4) pain in cancer survivors, with increasing numbers due to the success of antiblastic treatments, which have significantly improved overall survival and quality of life. In this review, non-pain specialists will find an overview including a detailed description of physiopathological mechanisms underlying central sensitization and pain chronification in bone pain, the rationale for the correct use of analgesics and invasive techniques in different pain syndromes, and the most recent recommendations published on these topics. The ultimate target of this review was to underlie that different types of pain can be observed in MM patients, and highlight that only after an accurate pain assessment, clinical examination, and pain classification, can pain be safely and effectively addressed by selecting the right analgesic option for the right patient.

Why Unidimensional Pain Measurement Prevails in the Pediatric Acute Pain Context and What Multidimensional Self-Report Methods Can Offer

Although pain is widely recognized to be a multidimensional experience and defined as such, unidimensional pain measurement focusing on pain intensity prevails in the pediatric acute pain context. Unidimensional assessments fail to provide a comprehensive picture of a child’s pain experience and commonly do little to shape clinical interventions. The current review paper overviews the theoretical and empirical literature supporting the multidimensional nature of pediatric acute pain. Literature reporting concordance data for children’s self-reported sensory, affective and evaluative pain scores in the acute pain context has been reviewed and supports the distinct nature of these dimensions. Multidimensional acute pain measurement holds particular promise for identifying predictive markers of chronicity and may provide the basis for tailoring clinical management. The current paper has described key reasons contributing to the widespread use of unidimensional, rather than multidimensional, acute pediatric pain assessment protocols. Implications for clinical practice, education and future research are considered.

Tapentadol: an effective option for the treatment of back pain

Back pain, including low back pain and neck pain, is the leading cause of disability worldwide. This type of pain is challenging to treat, since it presents both a nociceptive and a neuropathic component. The latter also contributes to the evolution of pain toward chronification. Treatment selection should therefore consider the ability to prevent this event. Tapentadol is characterized by a unique and innovative peculiar mechanism of action that makes it the first representative of a new class of central strong analgesics referred to as MOR-NRI. This molecule acts both on the nociceptive and neuropathic components of pain, and it can therefore be effective in the treatment of a mixed pain condition such as back pain. This narrative review discusses the rationale for the use of tapentadol in both low back pain and neck pain and presents available clinical data. Overall, data show that tapentadol prolonged release is a well-grounded treatment for chronic back pain, sustained by a strong mechanistic rationale and robust evidence. Given also the availability of long-term efficacy and safety data, we believe that this molecule should be considered as an elective therapy for chronic back pain.

Pharmacological rationale for tapentadol therapy: a review of new evidence

Chronic pain could be considered as a neurological disorder. Therefore, appropriate selection of the therapy, which should consider the pathophysiological mechanisms of pain, can result in a successful analgesic outcome. Tapentadol is an analgesic drug which acts both as a μ-opioid receptor (MOR) agonist and as a noradrenaline reuptake inhibitor (NRI), thereby generating a synergistic action in terms of analgesic efficacy, but not for the burden of adverse effects. Therefore, tapentadol can be defined as the first “MOR-NRI” drug. This molecule holds the potential to address at least some of the current limitations of analgesic therapy due to its unique mechanism of action and has shown to be safe and effective in the treatment of chronic pain of cancer and noncancer etiologies including nociceptive, neuropathic and mixed pain. In particular, the MOR component of tapentadol activity predominantly allows for analgesia in nociceptive pain; on the other hand, the NRI component contributes, now in a predominant manner, for analgesic efficacy in cases of neuropathic pain states. This paper will discuss recent pieces of evidence on the pathophysiology of pain, the background on tapentadol and then present some new studies on how the unique mechanism of action of tapentadol provides a key role in its analgesic efficacy in a number of pain states and with a favorable safety profile.

Tapentadol in the treatment of osteoarthritis: pharmacological rationale and clinical evidence

Osteoarthritis (OA) is the most prevalent joint disease in older people worldwide. Pain owing to OA is considered one of the most frequent causes of chronic pain; however, current pharmacological approaches have some limitations in terms of efficacy and safety. Of note, descending inhibitory pain pathways are often disrupted in chronic OA pain, and pharmacotherapies targeting those pathways – eg, those that block norepinephrine reuptake may be more appropriate for managing chronic pain than pure μ-opioid receptor (MOR) agonists. Tapentadol is an analgesic molecule, which combines two synergistic mechanisms of action, MOR, and norepinephrine reuptake inhibition. This narrative review will briefly discuss the mechanisms contributing to the onset and maintenance of pain in OA patients; clinical data on the use of tapentadol in this setting will then be presented and commented.

Assessing and Treating Chronic Pain in Patients with End-Stage Renal Disease

Pain is one of the most common symptoms among patients with end-stage renal disease (ESRD), and is often under recognized and not adequately managed in hemodialysis (HD) patients. Barriers to adequate pain management include poor awareness of the problem, insufficient medical education, fears of possible drug-related side effects, and common misconceptions about the inevitability of pain in elderly and HD patients. Caregivers working in HD should be aware of the possible consequences of inadequate pain assessment and management. Common pain syndromes in HD patients include musculoskeletal diseases and metabolic neuropathies, associated with typical intradialytic pain. Evaluating the etiology, nature, and intensity of pain is crucial for choosing the correct analgesic. A mechanism-based approach to pain management may result in a better outcome. Pharmacokinetic considerations on clearance alterations and possible toxicity in patients with ESRD should drive the right analgesic prescription. Comorbidities and polymedications may increase the risk of drug-drug interactions, therefore drug metabolism should be taken into account when selecting analgesic drugs. Automedication is common among HD patients but should be avoided to reduce the risk of hazardous drug administration. Further research is warranted to define the efficacy and safety of analgesic drugs and techniques in the context of patients with ESRD as generalizing information from studies conducted in the general population could be inappropriate and potentially dangerous. A multidisciplinary approach is recommended for the management of complex pain syndromes in frail patients, such as those suffering from ESRD.