Pain medicine position paper

P2X3 and P2X2/3 receptors inhibition produces a consistent analgesic efficacy: A systematic review and meta-analysis of preclinical studies

BACKGROUND

P2X3 and P2X2/3 receptors are promising therapeutic targets for pain treatment and selective inhibitors are under evaluation in ongoing clinical trials. Here we aim to consolidate and quantitatively evaluate the preclinical evidence on P2X3 and P2X2/3 receptors inhibitors for pain treatment.

METHODS

A literature search was conducted in PubMed, Scopus and Web-of-Science on August 5, 2023. Data was extracted and meta-analyzed using a random-effects model to estimate the analgesic efficacy of the intervention; then several subgroup analyses were performed.

RESULTS

67 articles were included. The intervention induced a consistent pain reduction (66.5 [CI95% = 58.5, 74.5]; p < 0.0001), which was highest for visceral pain (114.3), followed by muscle (79.8) and neuropathic pain (71.1), but lower for cancer (64.1), joint (57.5) and inflammatory pain (49.0). Further analysis showed a greater effect for mechanical hypersensitivity (70.4) compared to heat hypersensitivity (64.5) and pain-related behavior (54.1). Sex (male or female) or interspecies (mice or rats) differences were not appreciated (p > 0.05). The most used molecule was A-317491, but other such as gefapixant or eliapixant were also effective (p < 0.0001 for all). The analgesic effect was higher for systemic or peripheral administration than for intrathecal administration. Conversely, intracerebroventricular administration was not analgesic, but potentiated pain.

CONCLUSION

P2X3 and P2X2/3 receptor inhibitors showed a good analgesic efficacy in preclinical studies, which was dependent on the pain etiology, pain outcome measured, the drug used and its route of administration. Further research is needed to assess the clinical utility of these preclinical findings.

PROTOCOL REGISTRATION

PROSPERO ID CRD42023450685.

Clinical Efficacy of Auricular Vagus Nerve Stimulation in the Treatment of Chronic and Acute Pain: A Systematic Review and Meta-analysis

INTRODUCTION

Current guidelines for pain treatment recommend a personalized, multimodal and interdisciplinary approach as well as the use of a combination of drug and non-drug therapies. Risk factors for chronification should already be reduced in patients with acute pain, e.g., after surgery or trauma. Auricular vagus nerve stimulation (aVNS) could be an effective non-drug therapy in the multimodal treatment of chronic and acute pain. The aim of this systematic review and meta-analysis is to evaluate the clinical efficacy and safety of aVNS in treating chronic and acute pain conditions.

METHODS

A systematic literature search was performed regarding the application of auricular electrical stimulation in chronic and acute pain. Studies were classified according to their level of evidence (Jadad scale), scientific validity and risk of bias (RoB 2 tool) and analyzed regarding indication, method, stimulation parameters, duration of treatment and efficacy and safety. A meta-analysis on (randomized) controlled trials (using different comparators) was performed for chronic and acute pain conditions, respectively, including subgroup analysis for percutaneous (pVNS-needle electrodes) and transcutaneous (tVNS-surface electrodes) aVNS. The visual analog pain scale (VAS) was defined as primary efficacy endpoint.

RESULTS

A total of n = 1496 patients were treated with aVNS in 23 identified and analyzed studies in chronic pain, 12 studies in acute postoperative pain and 7 studies in experimental acute pain. Of these, seven studies for chronic pain and six studies for acute postoperative pain were included in the meta-analysis. In chronic pain conditions, including back pain, migraine and abdominal pain, a statistically significant reduction in VAS pain intensity for active compared to sham aVNS or control treatment with an effect size Hedges' g/mean difference of - 1.95 (95% confidence interval [CI]: - 3.94 to 0.04, p = 0.008) could be shown and a more favorable effect in pVNS compared to tVNS (- 5.40 [- 8.94; - 1.85] vs. - 1.00 [- 1.55; - 0.44]; p = 0.015). In acute pain conditions, single studies showed significant improvements with aVNS, e.g., in kidney donor surgery or tonsillectomy but, overall, a non-statistically significant reduction in VAS pain intensity for active compared to sham aVNS or control with - 0.70 [- 2.34; 0.93] (p = 0.15) could be observed in the meta-analysis. In acute pain results vary greatly between studies depending especially on co-medication and timepoints of assessment after surgery. A significant reduction in analgesics or opiate intake was documented in most studies evaluating this effect in chronic and acute pain. In 3 of the 12 randomized controlled trials in patients with chronic pain, a sustainable pain reduction over a period of up to 12 months was shown. Overall, aVNS was very well tolerated.

CONCLUSION

This systematic review and meta-analysis indicate that aVNS can be an effective and safe non-drug treatment in patients with specific chronic and acute postoperative pain conditions. Further research is needed to identify the influence of simulation parameters and find optimal and standardized treatment protocols while considering quality-of-life outcome parameters and prolonged follow-up periods. A more standardized approach and harmonization in study designs would improve comparability and robustness of outcomes.

Randomized, double-blind, phase 1a single-ascending dose and food effect studies assessing safety and pharmacokinetics of EC5026 in healthy volunteers

Chronic pain represents a significant unmet medical need, affecting one-fifth of the U.S. population. EC5026 is a small molecule inhibitor of the enzyme soluble epoxide hydrolase (sEH) which is being developed as a novel non-opioid, non-NSAID analgesic. EC5026 prolongs the action of epoxy fatty acids, endogenous analgesic lipid mediators that are rapidly metabolized by sEH. We evaluated the safety and pharmacokinetic profile of EC5026 in two phase I trials, a single-ascending dose (SAD) study and a fed-fasted study. The SAD study evaluated EC5026 doses ranging from 0.5 to 24 mg in healthy volunteers. EC5026 was well tolerated. No treatment-emergent adverse events were considered related to EC5026. No apparent treatment- or dose-related trends in laboratory results, vital signs, physical examinations, or electrocardiograms were observed. A linear, near-dose-proportional increase in exposure was observed with progressive doses in the SAD study; plasma exposure was below or near the lower limit of quantification after 0.5-2 mg doses. Mean half-lives ranged from 41.8 to 59.1 h. for doses of 8-24 mg, supporting a once-daily dosing regimen. In the fed-fasted study using 8 mg EC5026 tablets, higher peak concentrations (66%) and total exposures (53%) were observed under the fed condition. Plasma concentrations declined in a monoexponential manner with mean half-lives of 59.5 h. in the fed state and 66.9 h. in the fasted state. Future clinical trials using EC5026 for the treatment of pain are justified based on the favorable outcomes from both clinical trials along with preclinical evidence of analgesic activity.

Mechanism of human α3β GlyR modulation in inflammatory pain and 2, 6-DTBP interaction

α3β glycine receptor (GlyR) is a subtype of the GlyRs that belongs to the Cys-loop receptor superfamily. It is a target for non-psychoactive pain control drug development due to its high expression in the spinal dorsal horn and indispensable roles in pain sensation. α3β GlyR activity is inhibited by a phosphorylation in the large internal M3/M4 loop of α3 through the prostaglandin E2 (PGE2) pathway, which can be reverted by a small molecule analgesic, 2, 6-DTBP. However, the mechanism of regulation by phosphorylation or 2, 6-DTBP is unknown. Here we show M3/M4 loop compaction through phosphorylation and 2, 6-DTBP binding, which in turn changes the local environment and rearranges ion conduction pore conformation to modulate α3β GlyR activity. We resolved glycine-bound structures of α3β GlyR with and without phosphorylation, as well as in the presence of 2, 6-DTBP and found no change in functional states upon phosphorylation, but transition to an asymmetric super open pore by 2, 6-DTBP binding. Single-molecule Forster resonance energy transfer (smFRET) experiment shows compaction of M3/M4 loop towards the pore upon phosphorylation, and further compaction by 2, 6-DTBP. Our results reveal a localized interaction model where M3/M4 loop modulate GlyR function through physical proximation. This regulation mechanism should inform on pain medication development targeting GlyRs. Our strategy allowed investigation of how post-translational modification of an unstructured loop modulate channel conduction, which we anticipate will be applicable to intrinsically disordered loops ubiquitously found in ion channels.

REKOVER study protocol: a pRospective patient treatment rEgistry of tramadol and dexKetoprofen trometamol oral fixed-dose combination (SKUDEXA) in mOderate to seVere acutE pain in Real-world setting in Asia

INTRODUCTION

Satisfactory management of acute pain remains a major medical challenge despite the availability of multiple therapeutic options including the fixed-dose combination (FDC) drugs. Tramadol and dexketoprofen trometamol (TRAM/DKP) 75/25 mg FDC was launched in 2018 in Asia and is widely used in the management of moderate to severe acute pain. There are limited data on its effectiveness and safety in Asian patients, and therefore, a need to better understand its usage patterns in clinical practice. We aim to understand the usage pattern of TRAM/DKP FDC, its effectiveness and tolerability in patients with moderate to severe acute pain in Asia.

METHODS AND ANALYSIS

REKOVER is a phase-IV, multicountry, multicentre, prospective, real-world observational study. A total of 750 postsurgical and non-surgical patients (male and female, aged 18-80 years) will be recruited from 13 tertiary-care hospitals (15 sites) in Singapore, Thailand, the Philippines and Malaysia. All patients prescribed with TRAM/DKP FDC and willing to participate in the study will be enrolled. The recruitment duration for each site will be 6 months. The severity of pain will be collected using Numeric Pain Rating Scale through the treatment period from day 1 to day 5, while satisfaction with the treatment will be evaluated using Patient Global Evaluation Scale at the end of treatment. Any adverse event reported during the study duration will be recorded for safety analysis (up to day 6). The study data will be entered into the ClaimIt portal and mobile application (app) (ObvioHealth, USA). All the inpatient data will be entered into the portal by the study site and for outpatient it will be done by patients through an app.

ETHICS AND DISSEMINATION

The study has been approved by the local ethics committee from each study sites in Singapore, Thailand, the Philippines and Malaysia. Findings will be disseminated through local and global conference presentations, publications in peer-reviewed scientific journals and continuing medical education.

Outcomes of Pain Management Training for the Fourth- and Fifth-Year Medical Students

Pain management is a major medical issue. However, current medical education in Japan is inadequate with regard to training students to properly assess patients with acute and chronic pain and plan their treatment. Therefore, starting in 2019, Hyogo Medical University established a multidisciplinary educational system to better train medical students to provide pain care. The course, called clinical pain study, is offered to fourth- and fifth-year medical students. Fourth-year students learn the scientific aspects of pain through clinical practice. In this study, we assessed students' understanding of pain management based on the results of pretests and posttests performed before and after their practicum. These tests were administered from November 2019 to April 2022 to 263 fourth- and fifth-year medical students who took the clinical pain study class. The test results were compared in terms of the percentage of correct answers and the total score for each question using McNemar's chi-square test and paired t-tests, respectively. The results showed a significant improvement in the mean of the total score, confirming the improvement in medical students' knowledge (6.43 vs. 7.35 points; p < 0.001). Based on the results, overall, pain education at the university has had positive outcomes and will therefore be continued in the future.

Assessment of the Management of Patients with Chronic Pain Referred to a Specialized Pain Unit: A Cross-Sectional Multicenter Study (the DUO Project)

A multicenter cross-sectional study was designed to assess the quality of treatment of 1190 patients with chronic pain at the time of referral to a specialized pain unit. A total of 119 physicians from 77 pain units throughout Spain collected 23 indicators of the quality of care from 10 consecutive clinical records of chronic pain patients (5 men, 5 women). Degenerative spinal diseases (38.6%) and lumbosciatic pain (29.8%) were the most common etiologies. At the time of referral to the pain unit, 9.8% of patients were not receiving any analgesic treatment. Treatment was modified in 88.1% of the patients by adding adjuvant drugs, adding opioids or increasing the doses of analgesic medications, and using analgesic techniques. Women had higher percentages of osteoarthritis, headache and fibromyalgia as the cause of pain, longer duration of pain and severe pain intensity, and a higher proportion of changes in the diagnosis of the underlying condition with which they had been referred to the pain unit. Improvements should be made in the patient management and referral protocols not only in the clinics prior to patient referral to the pain unit, but also in the pain units themselves.

Epidemiology of Trauma History and Body Pain: A Retrospective Study of Community-Based Australian Women

OBJECTIVE

To assess whether body pain was associated with different trauma histories (physical injury vs. interpersonal injury [IPI]) within Australian women, along with body pain and trauma history associations with biological and psychological (biopsycho) confounders.

METHODS

A retrospective cross-sectional analysis was conducted on the Australian Longitudinal Study on Women's Health (ALSWH) 1973-1978 birth cohort wave 6 data. Relevant life events were categorized into two types of traumatic experience and included as exposure variables in a multinomial regression model for body pain subgroups. Also, subgroup analyses considered trauma and pain effects and interactions on biopsycho burden.

RESULTS

The unadjusted multinomial regression model revealed that a history of physical injury was found to be significantly associated with body pain severity, as was a history of IPI trauma. After the model was adjusted to include biopsycho confounders, the association between IPI and body pain was no longer significant, and post hoc analysis revealed the relationship was instead mediated by biopsycho confounders. Women with a history of IPI and body pain were also found to have the greatest biopsycho (physical functioning, stress, anxiety, and depression) burden.

DISCUSSION

The relationship between IPI and body pain was found to be mediated by biopsycho burden, whereas the relationship between physical injury and body pain was not. Also, a history of IPI was associated with a greater biopsycho burden than was a history of physical injury. These results suggest there is clinical value in considering the comprehensive trauma history of patients with pain when developing their biopsychosocial model of care.

The Predictive Value of Transcutaneous Electrical Nerve Stimulation for Patient Selection in Peripheral Nerve Field Stimulation for Chronic Low Back Pain: A Prospective Study

OBJECTIVE

Peripheral nerve field stimulation (PNFS) is an effective alternative treatment for patients with chronic low back pain. Transcutaneous electrical nerve stimulation (TENS) is frequently used in pain therapy. Aim of this prospective study was to examine the predictive value of TENS for later PNFS treatment.

MATERIALS AND METHODS

Between 2014 and 2019, a prospective cohort study of 41 patients with chronic lumbar pain was conducted. Pain intensity (NRS) was assessed before and after TENS use, preoperatively/postoperatively and in the follow-up after three and six months, SF12v2 questionnaires with physical (PCS) and mental component summary (MCS) scores, and Oswestry disability index (ODI) questionnaire at baseline as well as three and six months after PNFS implantation. Implantation of the PNFS-system with two percutaneous leads was performed after four to seven days of positive testing. Statistical analysis was performed using depending t-test, ANOVA, and Spearman correlation.

RESULTS

The cohort consisted of 41 patients (19 females, 22 males) with a median age of 60.5 years (IQR^25-75 52-67). Two patients were lost to follow-up. After positive PNFS testing a pulse generator (IPG) was implanted in 15 patients with positive TENS effect and 15 patients without TENS effect. Leads were explanted in nine patients after negative PNFS trial phase. TENS positive patients showed significant correlation to a positive effect in the PNFS trial phase in NRS reduction (p = 0.042) indicating that TENS responders will also respond to PNFS (94% patients). After three and six months follow-up median NRS and SF12v2 (PCS) improved significantly in both cohorts, SF12v2 (MCS) and ODI only in the TENS positive cohort, respectively.

CONCLUSION

TENS can be predictive for patient selection in PNFS, as TENS positive patients showed significant correlation with a positive PNFS trial period. Therefore, TENS positive patients might be justifiable to be directly implanted with leads and IPG. TENS positive patients further tend to show a better improvement in the follow-up.

A narrative review of data collection and analysis guidelines for comparative effectiveness research in chronic pain using patient-reported outcomes and electronic health records

Chronic pain is a widespread and complex set of conditions that are often difficult and expensive to treat. Comparative effectiveness research (CER) is an evolving research method that is useful in determining which treatments are most effective for medical conditions such as chronic pain. An underutilized mechanism for conducting CER in pain medicine involves combining patient-reported outcomes (PROs) with electronic health records (EHRs). Patient-reported pain and mental and physical health outcomes are increasingly collected during clinic visits, and these data can be linked to EHR data that are relevant to the treatment of a patient's pain, such as diagnoses, medications ordered, and medical comorbidities. When aggregated, this information forms a data repository that can be used for high-quality CER. This review provides a blueprint for conducting CER using PROs combined with EHRs. As an example, the University of Pittsburgh's patient outcomes repository for treatment is described. This system includes PROs collected via the Collaborative Health Outcomes Information Registry software and cross-linked data from the University of Pittsburgh Medical Center EHR. The requirements, best practice guidelines, statistical considerations, and caveats for performing CER with this type of data repository are also discussed.

The Socioeconomic Burden of Pain From War

War's burden on the health and well-being of combatants, civilians, and societies is well documented. Although the examination of soldiers' injuries in modern combat is both detailed and comprehensive, less is known about war-related injuries to civilians and refugees, including victims of torture. The societal burden of war-related disabilities persists for decades in war's aftermath. The complex injuries of combat survivors, including multiple pain conditions and neuropsychiatric comorbidities, challenge health care systems to reorganize care to meet these survivors' special needs.We use the case study method to illustrate the change in pain management strategies for injured combat survivors in one national health system, the US Department of Veterans Affairs (VA). The care of veterans' disabling injuries suffered in Vietnam contrasts with the care resulting from the VA's congressional mandate to design and implement a pain management policy that provides effective pain management to veterans injured in the recent Middle East conflicts.The outcomes-driven, patient-centric Stepped Care Model of biopsychosocial pain management requires system-wide patient education, clinician training, social networking, and administrative monitoring. Societies are encouraged to develop their health care system's capacity to effectively respond to the victims of warfare, including combatants and refugees.

Pain management in hospitals: patients' satisfaction and related barriers

Background:

Suboptimal pain control has been frequently reported in healthcare settings and documented to negatively impact patients’ health. Patients’ perception regarding pain management may influence their satisfaction regarding treatment.

Objectives:

This study focuses on the assessment of patients’ satisfaction regarding pain therapy and defining patient-related barriers for its implication.

Methods:

A cross-sectional study was conducted in two tertiary care hospitals from April till July 2017. A face-to face interview questionnaire was filled regarding pain scores and patients’ attitudes regarding pain management. Both medical and post-surgical adult patients with all types of pain were eligible to participate. A descriptive analysis of patient satisfaction and perceptions regarding pain management was done.

Results:

Results from 183 participants with a mean age of 49 (SD=17.33) revealed that pain was their main reason for hospitalization (71.6% of the cases). Numeric pain scores were recorded only in 14.2% of the patient medical files. Pain intensity documentation by healthcare professionals was found in 41.5% of the cases, and 7.7% of the patients had to wait for more than 30 minutes before getting the pain medication. Around 85% of the patients were satisfied with their pain management. Patients’ barriers to effective pain therapy were mainly fear of adverse effects, addiction, and additional costs (p<0.05).

Conclusions:

Pain remains a prevalent problem that requires more efforts for improvement. Our study can effectively serve as a start for larger studies where barriers to pain management can be assessed as an independent variable affecting pain management practice.

Spinal Cord Stimulation (SCS) with Anatomically Guided (3D) Neural Targeting Shows Superior Chronic Axial Low Back Pain Relief Compared to Traditional SCS-LUMINA Study

Background

The aim of this study was to determine whether spinal cord stimulation (SCS) using 3D neural targeting provided sustained overall and low back pain relief in a broad routine clinical practice population.

Study Design and Methods

This was a multicenter, open-label observational study with an observational arm and retrospective analysis of a matched cohort. After IPG implantation, programming was done using a patient-specific, model-based algorithm to adjust for lead position (3D neural targeting) or previous generation software (traditional). Demographics, medical histories, SCS parameters, pain locations, pain intensities, disabilities, and safety data were collected for all patients.

Results

A total of 213 patients using 3D neural targeting were included, with a trial-to-implant ratio of 86%. Patients used seven different lead configurations, with 62% receiving 24 to 32 contacts, and a broad range of stimulation parameters utilizing a mean of 14.3 (±6.1) contacts. At 24 months postimplant, pain intensity decreased significantly from baseline (ΔNRS = 4.2, N = 169, P  < 0.0001) and even more in in the severe pain subgroup (ΔNRS = 5.3, N = 91, P  < 0.0001). Axial low back pain also decreased significantly from baseline to 24 months (ΔNRS = 4.1, N = 70, P  < 0.0001, on the overall cohort and ΔNRS = 5.6, N = 38, on the severe subgroup). Matched cohort comparison with 213 patients treated with traditional SCS at the same centers showed overall pain responder rates of 51% (traditional SCS) and 74% (neural targeting SCS) and axial low back pain responder rates of 41% and 71% in the traditional SCS and neural targeting SCS cohorts, respectively. Lastly, complications occurred in a total of 33 of the 213 patients, with a 1.6% lead replacement rate and a 1.6% explant rate.

Conclusions

Our results suggest that 3D neural targeting SCS and its associated hardware flexibility provide effective treatment for both chronic leg and chronic axial low back pain that is significantly superior to traditional SCS.

A Randomized Controlled Trial of Subcutaneous Nerve Stimulation for Back Pain Due to Failed Back Surgery Syndrome: The SubQStim Study

Objectives

To compare the effectiveness of peripheral nerve stimulation utilizing a subcutaneous lead implant technique—subcutaneous nerve stimulation (SQS) plus optimized medical management (SQS + OMM arm) vs. optimized medical management alone (OMM arm) in patients with back pain due to failed back surgery syndrome.

Patients and Methods

Patients were recruited from 21 centers, in Europe, Israel, and Australia. Eligible patients were randomized (1:1) to SQS + OMM or OMM arms. Those in the SQS arm were implanted with a neurostimulator and up to two subcutaneous percutaneous cylindrical leads in the area of pain. Patients were evaluated pre‐randomization and at one, three, six, and nine months post‐randomization. The primary endpoint was the proportion of subjects with a ≥50% reduction in back pain intensity (“responder”) from baseline to nine months. Secondary outcomes included proportion of responders with a ≥50% reduction in back pain intensity at six months and ≥30% reduction at nine months, and the mean change from baseline in back pain intensity at six and nine months between the two arms.

Results

Due to the slow rate of recruitment, the study was terminated early with 116 subjects randomized. A total of 33.9% (19/56, missing: n = 20 [36%]) of subjects in the SQS + OMM arm and 1.7% (1/60, missing: n = 24 [40%]) in the OMM arm were responders at Month 9 (p < 0.0001). Secondary objectives showed a significant difference in favor of SQS + OMM arm.

Conclusion

The results indicate that the addition of SQS to OMM is more effective than OMM alone in relieving low back pain at up to nine months.

Osteoarthritis pain: What are we learning from animal models?

All experimental models of osteoarthritis (OA)-like joint damage are accompanied by behaviors indicative of pain. In experimental knee OA, evoked pain responses to exogenously applied stimuli suggest that animals become sensitized to mechanical stimuli. Neurobiological techniques including electrophysiology and in vivo calcium imaging confirm that joint damage is associated with mechanical stimuli through peripheral sensitization. Several mediators present in the OA joint can cause peripheral sensitization, most notably the neurotrophin nerve growth factor (NGF). Furthermore, experimental OA is associated with neuroinflammation in the peripheral nervous system and central nervous system (CNS), including macrophage infiltration of the dorsal root ganglia and microglial activation in the spinal cord. Increasingly, researchers are employing models that are slowly progressive, and this approach has revealed that distinct pain mechanisms operate in a time-dependent manner, which may have important translational significance. While the study of pain in experimental OA is rapidly evolving, with the application of increasingly sophisticated techniques to assess pain and unravel the neurobiology of its genesis, important gaps and limitations in our current approaches exist, which our research community needs to address.

Pain as a disease: an overview

The acknowledgment of pain as a pathologic entity in its own right remains debated. Notwithstanding the data showing the burden of pain as a disease, an ultimate recognition of the pathologic nature of this condition is lacking. In this study, we analyze the notion of pain as a disease through an historical overview of its several conceptualizations and report the main evidence supporting this notion. We believe that a clear definition of pain as a disease is necessary, especially considering the enormous global burden of this condition. Indeed, the recognition of pain as a definite pathologic state is crucial to raise awareness about this neglected global health problem and to promote the exploration of new specific therapeutic approaches.

Breaking barriers to novel analgesic drug development

Acute and chronic pain complaints, although common, are generally poorly served by existing therapies. This unmet clinical need reflects a failure to develop novel classes of analgesics with superior efficacy, diminished adverse effects and a lower abuse liability than those currently available. Reasons for this include the heterogeneity of clinical pain conditions, the complexity and diversity of underlying pathophysiological mechanisms, and the unreliability of some preclinical pain models. However, recent advances in our understanding of the neurobiology of pain are beginning to offer opportunities for developing novel therapeutic strategies and revisiting existing targets, including modulating ion channels, enzymes and G-protein-coupled receptors.

Patient Perception of Acute Pain Management: Data from Three Tertiary Care Hospitals

Introduction. The primary objectives of this study were to assess patients' description of their acute pain intensity; patients' attitude towards their pain management during hospitalization; and their overall satisfaction with pain treatment. Methodology. A cross-sectional questionnaire-based study was conducted between October 2014 and March 2015 in three medical centers in Lebanon. All participants' responses were reported using descriptive statistics. The association between categorical variables was evaluated using Pearson χ² test or Fisher's exact test where the expected cell count was < 5. Results. A total of 119 women on the maternity services and 177 patients on the orthopedic services were surveyed. Around 50% of obstetric and 37% of orthopedic patients reported pain to be severe at its highest intensity. In maternity and orthopedic patients, respectively, unfavorable practices included pain not being assessed prior to pain medication administration (19.3% and 30.5%), having to wait for ≥30 minutes before getting the pain medication (14.2% and 11.3%), and pain score not being documented on medical chart (95% and 93.2%). Surprisingly, 94.1% of the maternity and 89.2% of orthopedic patients were satisfied to strongly satisfied with their pain management. Conclusion. Pre- and postoperative pain remain a prevalent problem that requires a consensus and joint efforts for improvement.

Specialized Pain Clinics in Primary Care: Common Diagnoses, Referral Patterns and Clinical Outcomes - Novel Pain Management Model

An estimated 19% of the adult population in western countries lives with chronic pain. Pain management lies mainly within the primary care and community setting. We evaluated the outcome of a new model of secondary care clinics, conducted by primary care physicians with specialized training in pain medicine. Data on referral patterns, prevalence of pain diagnosis, and medication consumption were recorded at five secondary pain management clinics in the community setting. In total, 997 patients with pain attended 2,652 visits (average 2.7 visits per patient) during 12 mo. Patients' age ranged from 18 to 92 yr (mean 59 ± 19). Mean pain intensity on the first visit, evaluated by the visual analogue scale was 7.7/10. Myofascial pain syndrome was the most common diagnosis (82%). Treatment included dry needling or trigger point injection (82%), manual myofascial release (23%), and pharmacotherapy (38%). Significant short-term improvement after treatment was reported by 75% of patients, and 72% reported long-term improvement. Four percent were referred to tertiary care pain clinics, 5% were referred to other specialists, and 5% to imaging. Secondary, community-based pain clinics, run by specially-trained primary physicians, demonstrated feasibility. The vast majority of patients referred to the clinics were treated using simple, inexpensive modalities, while sparing referrals to unnecessary consultation visits, imaging tests, and medications.

Advancing the Pain Agenda in the Veteran Population

The Veterans Health Administration (VHA) provides medical care for Veterans after leaving the military. The combination of multiple deployments and battlefield exposures to physical and psychological trauma results in a higher prevalence and complexity of chronic pain in Veterans than in the general public. The VHA and the Department of Defense work together to develop a single standard of stepped pain management appropriate for all settings from moment of injury or disease onset. This article describes the education, academic detailing, and clinical programs and policies that are transforming pain care in the VHA.

Pain paper 2b: classification of orofacial pain and an update on assessment and diagnosis

The classification of chronic orofacial pain remains a contentious area. However, more recently, with the clarification of pain mechanisms and improved understanding of the underlying neurophysiology and modulation factors, there is more clarity of the possible division of pain conditions. Interestingly, the pathophysiology provides a basis for classification that has more clinical relevance. The principles of assessing and managing patients with pain have modified significantly, in line with recent improved understanding of the affective and emotional components in pain behaviour and suffering. Clinical Relevance: This paper aims to provide the dental and medical teams with a review of the classification of trigeminal pain with an overview of how to assess and diagnose patients with trigeminal pain.

Acute Pain Medicine in the United States: A Status Report

BACKGROUND

Consensus indicates that a comprehensive,multimodal, holistic approach is foundational to the practice of acute pain medicine (APM),but lack of uniform, evidence-based clinical pathways leads to undesirable variability throughout U. S. healthcare systems. Acute pain studies are inconsistently synthesized to guide educational programs. Advanced practice techniques involving regional anesthesia assume the presence of a physician-led, multidisciplinary acute pain service,which is often unavailable or inconsistently applied.This heterogeneity of educational and organizational standards may result in unnecessary patient pain and escalation of healthcare costs.

METHODS

A multidisciplinary panel was nominated through the APM Shared Interest Group of the American Academy of Pain Medicine. The panel met in Chicago, IL, in July 2014, to identify gaps and set priorities in APM research and education.

RESULTS

The panel identified three areas of critical need: 1) an open-source acute pain data registry and clinical support tool to inform clinical decision making and resource allocation and to enhance research efforts; 2) a strong professional APM identity as an accredited subspecialty; and 3) educational goals targeted toward third-party payers,hospital administrators, and other key stake holders to convey the importance of APM.

CONCLUSION

This report is the first step in a 3-year initiative aimed at creating conditions and incentives for the optimal provision of APM services to facilitate and enhance the quality of patient recovery after surgery, illness, or trauma. The ultimate goal is to reduce the conversion of acute pain to the debilitating disease of chronic pain.

The relationship between nonsurgical pain and interference with activity in patients undergoing a total knee arthroplasty

BACKGROUND

Patients with nonsurgical pain (NSP) after a total knee arthroplasty (TKA) report different patterns of pain interference than those without NSP.

PURPOSE

This study explores the severity and ways in which NSP interferes with activities 48 hours and 6-7 weeks post surgery.

ANALYSIS

Univariate and multivariate analyses were used. The mean score for intensity at 48 hours was 1.78, and at 6-7 weeks it was 1.15. The mean score for interference with activities at 48 hours was 1.62 and at 6-7 weeks it was 0.91. Highest NSP pain interference at 48 hours was for "activity," "sleep," and "enjoyment of life." At 6-7 weeks, the highest scores were for "activity," "sleep," and "walking." No significant differences were noted for age, race, education, or gender.

IMPLICATIONS

Although rated "mild," this pain should be addressed. The NSP indicates a baseline of chronic and persistent pain, which is an opportunity to work with our patients to mitigate this pain. Total knee arthroplasty, a common and effective treatment for painful knee conditions attributed to various forms of arthritis, is known to be a painful surgical procedure. Two of the major concerns voiced by patients awaiting TKA are about postoperative pain management and rehabilitation efforts after the procedure (). Healthcare providers offer a range of methods and strategies to deal with postoperative TKA pain, yet to date no single method offers complete satisfaction (; ; ; ).

Assessment of the safety and efficacy of extended-release oxycodone/acetaminophen, for 14 days postsurgery

OBJECTIVE

To investigate the safety and satisfaction of patients treated ≤ 14 days after unilateral bunionectomy with extended-release oxycodone/acetaminophen (ER OC/APAP), a biphasic (ER and immediate release) fixed-dose combination analgesic being developed for moderate to severe acute pain.

RESEARCH DESIGN AND METHODS

This was an open-label extension (OLE) of a randomized, double-blind, placebo-controlled trial (DBRCT) of patients undergoing bunionectomy. Patients who consented to the OLE before entering the 48 hour DBRCT entered the OLE upon completing the DBRCT and during the OLE received two tablets of ER OC/APAP (15/650 mg total dose) every 12 hours for ≤ 14 days. ClinicalTrials identifier: NCT01484652.

MAIN OUTCOME MEASURES

Treatment-emergent adverse events, physical examinations, vital sign measurements, and clinical laboratory testing were assessed throughout the study. Global assessments of treatment satisfaction were made at the end of the DBRCT and at each clinic visit during the OLE.

RESULTS

A total of 146 patients consented to the OLE before entering the DBRCT and 129 completed the OLE. Tolerability of ER OC/APAP during the OLE was consistent with that of an opioid product. Adverse events occurred during the OLE in 64 patients (43.8%); the most common were gastrointestinal events including nausea (17.8%), vomiting (7.5%), and constipation (6.2%). No changes in vital signs or clinical laboratory tests were considered by the investigator to be clinically significant. At all visits during the OLE, the majority of patients were satisfied or very satisfied with their medication. Limitations include a 14 day postprocedure study duration that may be confounded with natural healing time, and lack of a placebo arm.

CONCLUSIONS

These results show that ER OC/APAP demonstrated an expected safety and tolerability profile and good patient satisfaction in a postsurgical model of acute pain.

Opioid prescribing patterns for non-malignant chronic pain for rural versus non-rural US adults: a population-based study using 2010 NAMCS data

Background

Non-malignant chronic pain (NMCP) is one of the most common reasons for primary care visits. Pain management health care disparities have been documented in relation to patient gender, race, and socioeconomic status. Although not studied in relation to chronic pain management, studies have found that living in a rural community in the US is associated with health care disparities. Rurality as a social determinant of health may influence opioid prescribing. We examined rural and non-rural differences in opioid prescribing patterns for NMCP management, hypothesizing that distinct from education, income, racial or gender differences, rural residency is a significant and independent factor in opioid prescribing patterns.

Methods

2010 National Ambulatory Medical Care Survey (NAMCS) data were examined using bivariate and multivariate techniques. NAMCS data were collected using a multi-stage sampling strategy. For the multivariate analysis performed the SPSS complex samples algorithm for logistic regression was used.

Results

In 2010 an estimated 9,325,603 US adults (weighted from a sample of 2745) seen in primary care clinics had a diagnosis of NMCP; 36.4% were prescribed an opioid. For US adults with a NMCP diagnosis bivariate analysis revealed rural residents had higher odds of having an opioid prescription than similar non-rural adults (OR = 1.515, 95% CI 1.513-1.518). Complex samples logistic regression analysis confirmed the importance of rurality and yielded that US adults with NMCP who were prescribed an opioid had higher odds of: being non-Caucasian (AOR =2.459, 95% CI 1.194-5.066), and living in a rural area (AOR =2.935, 95% CI 1.416-6.083).

Conclusions

Our results clearly indicated that rurality is an important factor in opioid prescribing patterns that cannot be ignored and bears further investigation. Further research on the growing concern about the over-prescribing of opioids in the US should now include rurality as a variable in data generation and analysis. Future research should also attempt to document the ecological, sociological and political factors impacting opioid prescribing and care in rural communities. Prescribers and health care policy makers need to critically evaluate the implications of our findings and their relationship to patient needs, best practices in a rural setting, and the overall consequences of increased opioid prescribing on rural communities.

Is experimentally induced pain associated with socioeconomic status? Do poor people hurt more?

Background

The association of pain and socioeconomic status is widely reported, yet much less clearly understood. The aim of this study was to investigate the association of experimentally induced pain threshold and tolerance with socioeconomic status.

Material/Methods

The study sample consisted of 319 adult subjects from the population of the island of Vis, Croatia, which was previously shown to have a high level of social homogeneity. A manual dolorimeter was used to measure mechanical pressure pain threshold (least stimulus intensity) and pain tolerance (maximum tolerance stimulus intensity) on both hands. Pain tolerance interval was defined as the difference between pain tolerance and threshold. Years of schooling and material status were used as socioeconomic estimates.

Results

Both of the socioeconomic estimates were significantly correlated with pain threshold, tolerance, and tolerance interval (P<0.001). The mixed modeling analysis, controlled for the effects of age, gender, and 4 psychological variables, indicated that education was not a significant predictor in any of the 3 models. However, lower material status was significantly associated with lower pain tolerance (P=0.038) and narrower pain tolerance interval (P=0.032), but not with pain threshold (P=0.506). The overall percentages of explained variance were lower in the tolerance interval model (20.2%) than in pain tolerance (23.1%) and threshold (33.1%), suggesting the increasing share of other confounding variables in pain tolerance and even more so in tolerance interval model.

Conclusions

These results suggest a significant association between experimentally induced pain tolerance and tolerance interval with material status, suggesting that poor people indeed do hurt more.

Rules and values: a coordinated regulatory and educational approach to the public health crises of chronic pain and addiction

Chronic pain and opioid addiction are 2 pressing public health problems, and prescribing clinicians often lack the skills necessary to manage these conditions. Our study sought to address the benefits of a coalition of an academic medical center pain faculty and government agencies in addressing the high unintentional overdose death rates in New Mexico. New Mexico's 2012-2013 mandated chronic pain and addiction education programs studied more than 1000 clinicians. Positive changes were noted in precourse and postcourse surveys of knowledge, self-efficacy, and attitudes. Controlled substance dispensing data from the New Mexico Board of Pharmacy also demonstrated safer prescribing. The total morphine and Valium milligram equivalents dispensed have decreased continually since 2011. There was also a concomitant decline in total drug overdose deaths.

Pain medicine: The case for an independent medical specialty and training programs

Over the last 30 years, pain has become one of the most dynamic areas of medicine and a public health issue. According to a recent Institute of Medicine report, pain affects approximately 100 million Americans at an estimated annual economic cost of $560 to $635 billion and is poorly treated overall. The American Board of Medical Specialties (ABMS) recognizes a pain subspecialty, but pain care delivery has struggled with increasing demand and developed in an inconsistent and uncoordinated fashion. Pain education is insufficient and highly variable. Multiple pain professional organizations have led to fragmentation of the field and lack of interdisciplinary agreement, resulting in confusion regarding who speaks for pain medicine. In this Perspective, the authors argue that ABMS recognition of pain medicine as an independent medical specialty would provide much needed structure and oversight for the field and would generate credibility for the specialty and its providers among medical peers, payers, regulatory and legislative agencies, and the public at large. The existing system, managed by three ABMS boards, largely excludes other specialties that contribute to pain care, fails to provide leadership from a single professional organization, provides suboptimal training exposure to pain medicine, and lengthens training, which results in inefficient use of time and educational resources. The creation of a primary ABMS conjoint board in pain medicine with its own residency programs and departments would provide better coordinated training, ensure the highest degree of competence of pain medicine specialists, and improve the quality of pain care and patient safety.

A randomized, double-blind, placebo-controlled study of the efficacy and safety of MNK-795, a dual-layer, biphasic, immediate-release and extended-release combination analgesic for acute pain

OBJECTIVE

To investigate the efficacy and safety of a bilayer combination oxycodone (OC) and acetaminophen (APAP) analgesic with both immediate-release and extended-release (ER) components (OC/APAP ER) in patients with moderate to severe pain using an established acute pain model.

RESEARCH DESIGN AND METHODS

This was a randomized, double-blind, placebo-controlled trial. Adult patients were included in the study if they had a pain intensity score≥4 on a 0-10 numerical rating scale after bunionectomy surgery, and were randomized (1:1) to receive four doses (two tablets q12h) of OC/APAP ER or placebo.

CLINICAL TRIAL REGISTRATION

NCT01484652.

MAIN OUTCOME MEASURES

The primary efficacy endpoint was the summed pain intensity difference over the first 48 hours (SPID48). Secondary endpoints included SPIDs and total pain relief (TOTPAR) over the dosing intervals; time to perceptible, meaningful, and confirmed pain relief; and the proportion of patients with ≥30% reduction in pain intensity scores.

RESULTS

A total of 329 patients were enrolled, of whom 266 (OC/APAP ER, n=135; placebo, n=131) completed the study. The mean (SE) SPID48 was 114.9 (7.6) in the OC/APAP ER group and 66.9 (7.6) in the placebo group (P<0.0001). SPID and TOTPAR values were significantly greater with OC/APAP ER than with placebo over all time periods analyzed, and the median times to perceptible, meaningful, and confirmed pain relief were significantly shorter. More patients showed ≥30% reduction in pain intensity scores with OC/APAP ER than with placebo at all times after 0.5 hours. OC/APAP ER was generally well tolerated. A limitation of this study was the lack of an active comparator.

CONCLUSIONS

OC/APAP ER was efficacious and generally well tolerated in an established model of moderate to severe acute pain, providing an onset of analgesia in approximately 30 minutes and sustained pain relief over the 12 hour dosing period.

Patients' experiences of pain in the 48 hours following total knee arthroplasty

BACKGROUND

Previous research indicates that both pain severity and interference caused by pain should be addressed in the recovery period following total knee arthroplasty.

PURPOSE

This research describes the range of pain severity of patients in the first 48 hours postoperation, ways in which pain interferes with activities, and the observed differences in pain experience by patients' age, level of education, race, and gender, using the Brief Pain Inventory.

ANALYSIS

Descriptive statistics and multivariate analysis were used to assess the data.

FINDINGS

Of the participants, 12% reported severe pain and 35% reported severe interference with general activities. Pain interfered most with walking, activities, and physical therapy. There were no differences by race, gender, or education. Older participants reported less pain and less interference. Participants reporting nonsurgical pain reported more interference with mood, walking, relationships with other people, and sleep.

RECOMMENDATIONS

Pain evaluation should include an assessment of pain unrelated to the surgical procedure. Additional research exploring the impact of nonpostoperative surgical pain during the postoperative period is needed.

Clinically employed opioid analgesics produce antinociception via μ-δ opioid receptor heteromers in Rhesus monkeys

Morphine and related drugs are widely employed as analgesics despite the side effects associated with their use. Although morphine is thought to mediate analgesia through mu opioid receptors, delta opioid receptors have been implicated in mediating some side effects such as tolerance and dependence. Here we present evidence in rhesus monkeys that morphine, fentanyl, and possibly methadone selectively activate mu-delta heteromers to produce antinociception that is potently antagonized by the delta opioid receptor antagonist, naltrindole (NTI). Studies with HEK293 cells expressing mu-delta heteromeric opioid receptors exhibit a similar antagonism profile of receptor activation in the presence of NTI. In mice, morphine was potently inhibited by naltrindole when administered intrathecally, but not intracerebroventricularly, suggesting the possible involvement of mu-delta heteromers in the spinal cord of rodents. Taken together, these results strongly suggest that, in primates, mu-delta heteromers are allosterically coupled and mediate the antinociceptive effects of three clinically employed opioid analgesics that have been traditionally viewed as mu-selective. Given the known involvement of delta receptors in morphine tolerance and dependence, our results implicate mu-delta heteromers in mediating both antinociception and these side effects in primates. These results open the door for further investigation in humans.

Pharmacology of nonsteroidal antiinflammatory drugs and opioids

Chronic pain affects up to 50 million Americans every day. Traditional treatment has included acetaminophen, nonsteroidal antiinflammatory drugs (NSAIDs), or opioids. The combination of NSAIDs and opioids can provide effective treatment for up to 90% of patients with chronic pain, but the NSAIDs have the potential for significant, even life-threatening side effects. Additionally, the nonselective cyclooxygenase inhibitors with 16,000 deaths per year in the United States might not be any safer. The opioids are great for short-term pain, but may need to be adjusted or changed frequently due to the development of tolerance. Understanding of the mechanism of opioids and NSAIDs has improved greatly over the past decade, but is still incomplete.