Considerations for extrapolating evidence of acute and chronic pain analgesic efficacy

What a pain in the … back: a review of current treatment options with a focus on naproxen sodium

Non-specific low back pain (LBP) represents a challenging and prevalent condition that is one of the most common symptoms leading to primary care physician visits. While established guidelines recommend prioritizing non-pharmacological approaches as the primary course of action, pharmacological treatments are advised when non-pharmacological approaches are ineffective or based on patient preference. These guidelines recommend non-steroidal anti-inflammatory drugs (NSAIDs) or skeletal muscle relaxers (SMRs) as the first-line pharmacological options for acute or subacute LBP, while NSAIDs are the exclusive first-line pharmacological option for chronic LBP. Although SMRs are generally effective for acute LBP, the available evidence does not support the view that they improve functional recovery, and their comparative efficacy to NSAIDs and other analgesics remains unknown, while studies have shown them to introduce adverse events without significantly reducing LBP. Moreover, opioids continue to be widely prescribed for LBP, despite limited evidence for effectiveness and known risks of addiction and overdose. Broader use of non-opioid pharmacotherapy, including the appropriate use of OTC options, is critical to addressing the opioid crisis. The balance of evidence indicates that NSAIDs have a favorable benefit-risk profile when compared to other available pharmacological treatment options for non-specific LBP, a condition that is primarily acute in nature and well-suited for self-treatment with OTC analgesics. While clinical guidelines do not differentiate between NSAIDs, evidence indicates that OTC naproxen sodium effectively relieves pain across multiple types of pain models, and furthermore, the 14-h half-life of naproxen sodium allows sustained, all day pain relief with reduced patient pill burden as compared to shorter acting options. Choosing the most appropriate approach for managing LBP, including non-pharmacological options, should be based on the patient's condition, severity of pain, potential risks, and individual patient preference and needs.

Peripheral Neuroinflammation and Pain: How Acute Pain Becomes Chronic

The number of individuals suffering from severe chronic pain and its social and financial impact is staggering. Without significant advances in our understanding of how acute pain becomes chronic, effective treatments will remain out of reach. This mini review will briefly summarize how critical signaling pathways initiated during the early phases of peripheral nervous system inflammation/ neuroinflammation establish long-term modifications of sensory neuronal function. Together with the recruitment of non-neuronal cellular elements, nociceptive transduction is transformed into a pathophysiologic state sustaining chronic peripheral sensitization and pain. Inflammatory mediators, such as nerve growth factor (NGF), can lower activation thresholds of sensory neurons through posttranslational modification of the pain-transducing ion channels transient-receptor potential TRPV1 and TRPA1. Performing a dual role, NGF also drives increased expression of TRPV1 in sensory neurons through the recruitment of transcription factor Sp4. More broadly, Sp4 appears to modulate a nociceptive transcriptome including TRPA1 and other genes encoding components of pain transduction. Together, these findings suggest a model where acute pain evoked by peripheral injury-induced inflammation becomes persistent through repeated cycles of TRP channel modification, Sp4-dependent overexpression of TRP channels and ongoing production of inflammatory mediators.

Effect of Pain Coping Skills Training on Pain and Pain Medication Use for Women With Breast Cancer

CONTEXT

Pain is distressing for women with breast cancer. Pain medication may not provide full relief and can have negative side-effects. Cognitive-behavioral pain intervention protocols reduce pain severity and improve self-efficacy for pain management. These interventions' impact on pain medication use is less clear. Intervention length and coping skills use might play a role in pain outcomes.

OBJECTIVES

Secondary analysis to examine differences in pain severity, pain medication use, pain self-efficacy, and coping skill use after five- and one-session cognitive-behavioral pain intervention protocols. Pain self-efficacy and coping skills use were assessed as mediators of intervention effects on pain and pain medication use.

METHODS

Women (N = 327) with stage I-III breast cancer were enrolled in a randomized trial comparing individually-delivered, five- and one-session pain coping skills training (PCST). Pain severity, pain medication use, pain self-efficacy, and coping skills use were assessed preintervention and five to eight weeks later (postintervention).

RESULTS

Pain and pain medication use significantly decreased, while pain self-efficacy increased pre-post for women randomized to both conditions (P's <.05). Five-session PCST participants demonstrated less pain (P =.03) and pain medication use (P =.04), and more pain self-efficacy (P =.02) and coping skills use (P =.04) at postintervention compared to one-session PCST participants. Pain self-efficacy mediated the relationship of intervention condition with pain and pain medication use.

CONCLUSION

Both conditions led to improvements in pain, pain medication use, pain self-efficacy, and coping skills use, and 5-session PCST showed the greatest benefits. Brief cognitive-behavioral pain intervention improve pain outcomes, and pain self-efficacy may play a role in these effects.

Strategies to manage auxiliary pain medications in chronic pain trials: a topical review

Chronic pain trials commonly allow auxiliary pain medications such as rescue and concomitant analgesics in addition to the randomized treatment. Changes in auxiliary pain medications after randomization represent intercurrent events that may affect either the interpretation or the existence of the measurements associated with the clinical question of interest, complicating the assessment of treatment efficacy. In chronic pain trials, pain intensity typically varies and patients may take the auxiliary medications 1 day but not the next or increase and decrease the dosages temporarily while continuing their randomized study medication. This distinctive feature of auxiliary pain medications as an intercurrent event has received little attention in the literature. Further clarifications on how to manage these issues are therefore pressing. Here we provide perspectives on issues related to auxiliary pain medication-related intercurrent events in randomized controlled chronic pain trials considering the strategies suggested in the E9(R1) addendum to the ICH guideline on statistical principles for clinical trials.

Hormonal treatments for endometriosis: The endocrine background

Endometriosis is a benign uterine disorder characterized by menstrual pain and infertility, deeply affecting women's health. It is a chronic disease and requires a long term management. Hormonal drugs are currently the most used for the medical treatment and are based on the endocrine pathogenetic aspects. Estrogen-dependency and progesterone-resistance are the key events which cause the ectopic implantation of endometrial cells, decreasing apoptosis and increasing oxidative stress, inflammation and neuroangiogenesis. Endometriotic cells express AMH, TGF-related growth factors (inhibin, activin, follistatin) CRH and stress related peptides. Endocrine and inflammatory changes explain pain and infertility, and the systemic comorbidities described in these patients, such as autoimmune (thyroiditis, arthritis, allergies), inflammatory (gastrointestinal/urinary diseases) and mental health disorders.The hormonal treatment of endometriosis aims to block of menstruation through an inhibition of hypothalamus-pituitary-ovary axis or by causing a pseudodecidualization with consequent amenorrhea, impairing the progression of endometriotic implants. GnRH agonists and antagonists are effective on endometriosis by acting on pituitary-ovarian function. Progestins are mostly used for long term treatments (dienogest, NETA, MPA) and act on multiple sites of action. Combined oral contraceptives are also used for reducing endometriosis symptoms by inhibiting ovarian function. Clinical trials are currently going on selective progesterone receptor modulators, selective estrogen receptor modulators and aromatase inhibitors. Nowadays, all these hormonal drugs are considered the first-line treatment for women with endometriosis to improve their symptoms, to postpone surgery or to prevent post-surgical disease recurrence. This review aims to provide a comprehensive state-of-the-art on the current and future hormonal treatments for endometriosis, exploring the endocrine background of the disease.

AAAPT Diagnostic Criteria for Acute Thoracic Surgery Pain

Patients undergoing thoracic surgery experience particular challenges for acute pain management. Availability of standardized diagnostic criteria for identification of acute pain after thoracotomy and video assisted thoracic surgery (VATS) would provide a foundation for evidence-based management and facilitate future research. The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership with the United States Food and Drug Administration, the American Pain Society (APS), and the American Academy of Pain Medicine (AAPM) formed the ACTTION-APS-AAPM Pain Taxonomy (AAAPT) initiative to address absence of acute pain diagnostic criteria. A multidisciplinary working group of pain experts was invited to develop diagnostic criteria for acute thoracotomy and VATS pain. The working group used available studies and expert opinion to characterize acute pain after thoracotomy and VATS using the 5-dimension taxonomical structure proposed by AAAPT (i.e., core diagnostic criteria, common features, modulating factors, impact/functional consequences, and putative mechanisms). The resulting diagnostic criteria will serve as the starting point for subsequent empirically validated criteria. PERSPECTIVE ITEM: This article characterizes acute pain after thoracotomy and VATS using the 5-dimension taxonomical structure proposed by AAAPT (ie, core diagnostic criteria, common features, modulating factors, impact and/or functional consequences, and putative mechanisms).

AAAPT Diagnostic Criteria for Acute Neuropathic Pain

OBJECTIVE

Acute neuropathic pain is a significant diagnostic challenge, and it is closely related to our understanding of both acute pain and neuropathic pain. Diagnostic criteria for acute neuropathic pain should reflect our mechanistic understanding and provide a framework for research on and treatment of these complex pain conditions.

METHODS

The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership with the U.S. Food and Drug Administration (FDA), the American Pain Society (APS), and the American Academy of Pain Medicine (AAPM) collaborated to develop the ACTTION-APS-AAPM Pain Taxonomy (AAAPT) for acute pain. A working group of experts in research and clinical management of neuropathic pain was convened. Group members used literature review and expert opinion to develop diagnostic criteria for acute neuropathic pain, as well as three specific examples of acute neuropathic pain conditions, using the five dimensions of the AAAPT classification of acute pain.

RESULTS

AAAPT diagnostic criteria for acute neuropathic pain are presented. Application of these criteria to three specific conditions (pain related to herpes zoster, chemotherapy, and limb amputation) illustrates the spectrum of acute neuropathic pain and highlights unique features of each condition.

CONCLUSIONS

The proposed AAAPT diagnostic criteria for acute neuropathic pain can be applied to various acute neuropathic pain conditions. Both the general and condition-specific criteria may guide future research, assessment, and management of acute neuropathic pain.

Research design considerations for chronic pain prevention clinical trials: IMMPACT recommendations

Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.

Development and pilot testing of an mHealth behavioral cancer pain protocol for medically underserved communities

The purpose of this study was to refine and test a mobile-health behavioral cancer pain coping skills training protocol for women with breast cancer and pain from medically underserved areas. Three focus groups (Phase 1) were used to refine the initial protocol. A single-arm pilot trial (Phase 2) was conducted to assess feasibility, acceptability, and changes in outcomes. The intervention was delivered at a community-based clinic via videoconferencing technology. Participants were women (N = 19 for Phase 1 and N = 20 for Phase 2) with breast cancer and pain in medically underserved areas. Major themes from focus groups were used to refine the intervention. The refined intervention demonstrated feasibility and acceptability. Participants reported significant improvement in pain severity, pain interference, and self-efficacy for pain management. Our intervention is feasible, acceptable, and likely to lead to improvement in pain-related outcomes for breast cancer patients in medically underserved areas. Implications for Psychosocial Oncology Practice Breast cancer patients being treated in medically underserved areas have a dearth of exposure to behavioral interventions that may improve their ability to manage pain. Evidence from this single-arm pilot trial suggests that our mobile-health behavioral cancer pain coping skills training protocol is acceptable and feasible in this vulnerable population. Appropriately adapted mobile-health technologies may provide an avenue to reach underserved patients and implement behavioral interventions to improve pain management.

The ACTTION-APS-AAPM Pain Taxonomy (AAAPT) Multidimensional Approach to Classifying Acute Pain Conditions

Objective

With the increasing societal awareness of the prevalence and impact of acute pain, there is a need to develop an acute pain classification system that both reflects contemporary mechanistic insights and helps guide future research and treatment. Existing classifications of acute pain conditions are limiting, with a predominant focus on the sensory experience (e.g., pain intensity) and pharmacologic consumption. Consequently, there is a need to more broadly characterize and classify the multidimensional experience of acute pain.

Setting

Consensus report following expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM).

Methods

As a complement to a taxonomy recently developed for chronic pain, the ACTTION public-private partnership with the US Food and Drug Administration, the APS, and the AAPM convened a consensus meeting of experts to develop an acute pain taxonomy using prevailing evidence. Key issues pertaining to the distinct nature of acute pain are presented followed by the agreed-upon taxonomy. The ACTTION-APS-AAPM Acute Pain Taxonomy will include the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms. Future efforts will consist of working groups utilizing this taxonomy to develop diagnostic criteria for a comprehensive set of acute pain conditions.

Perspective

The ACTTION-APS-AAPM Acute Pain Taxonomy (AAAPT) is a multidimensional acute pain classification system designed to classify acute pain along the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms.

Conclusions

Significant numbers of patients still suffer from significant acute pain, despite the advent of modern multimodal analgesic strategies. Mismanaged acute pain has a broad societal impact as significant numbers of patients may progress to suffer from chronic pain. An acute pain taxonomy provides a much-needed standardization of clinical diagnostic criteria, which benefits clinical care, research, education, and public policy. For the purposes of the present taxonomy, acute pain is considered to last up to seven days, with prolongation to 30 days being common. The current understanding of acute pain mechanisms poorly differentiates between acute and chronic pain and is often insufficient to distinguish among many types of acute pain conditions. Given the usefulness of the AAPT multidimensional framework, the AAAPT undertook a similar approach to organizing various acute pain conditions.

The ACTTION-APS-AAPM Pain Taxonomy (AAAPT) Multidimensional Approach to Classifying Acute Pain Conditions

OBJECTIVE

With the increasing societal awareness of the prevalence and impact of acute pain, there is a need to develop an acute pain classification system that both reflects contemporary mechanistic insights and helps guide future research and treatment. Existing classifications of acute pain conditions are limiting, with a predominant focus on the sensory experience (eg, pain intensity) and pharmacologic consumption. Consequently, there is a need to more broadly characterize and classify the multidimensional experience of acute pain.

SETTING

Consensus report following expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM).

METHODS

As a complement to a taxonomy recently developed for chronic pain, the ACTTION public-private partnership with the US Food and Drug Administration, the APS, and the AAPM convened a consensus meeting of experts to develop an acute pain taxonomy using prevailing evidence. Key issues pertaining to the distinct nature of acute pain are presented followed by the agreed-upon taxonomy. The ACTTION-APS-AAPM Acute Pain Taxonomy will include the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms. Future efforts will consist of working groups utilizing this taxonomy to develop diagnostic criteria for a comprehensive set of acute pain conditions.

PERSPECTIVE

The ACTTION-APS-AAPM Acute Pain Taxonomy (AAAPT) is a multidimensional acute pain classification system designed to classify acute pain along the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms.

CONCLUSIONS

Significant numbers of patients still suffer from significant acute pain, despite the advent of modern multimodal analgesic strategies. Mismanaged acute pain has a broad societal impact as significant numbers of patients may progress to suffer from chronic pain. An acute pain taxonomy provides a much-needed standardization of clinical diagnostic criteria, which benefits clinical care, research, education, and public policy. For the purposes of the present taxonomy, acute pain is considered to last up to seven days, with prolongation to 30 days being common. The current understanding of acute pain mechanisms poorly differentiates between acute and chronic pain and is often insufficient to distinguish among many types of acute pain conditions. Given the usefulness of the AAPT multidimensional framework, the AAAPT undertook a similar approach to organizing various acute pain conditions.

Optimizing delivery of a behavioral pain intervention in cancer patients using a sequential multiple assignment randomized trial SMART

BACKGROUND/AIMS

Pain is common in cancer patients and results in lower quality of life, depression, poor physical functioning, financial difficulty, and decreased survival time. Behavioral pain interventions are effective and nonpharmacologic. Traditional randomized controlled trials (RCT) test interventions of fixed time and dose, which poorly represent successive treatment decisions in clinical practice. We utilize a novel approach to conduct a RCT, the sequential multiple assignment randomized trial (SMART) design, to provide comparative evidence of: 1) response to differing initial doses of a pain coping skills training (PCST) intervention and 2) intervention dose sequences adjusted based on patient response. We also examine: 3) participant characteristics moderating intervention responses and 4) cost-effectiveness and practicality.

METHODS/DESIGN

Breast cancer patients (N=327) having pain (ratings≥5) are recruited and randomly assigned to: 1) PCST-Full or 2) PCST-Brief. PCST-Full consists of 5 PCST sessions. PCST-Brief consists of one 60-min PCST session. Five weeks post-randomization, participants re-rate their pain and are re-randomized, based on intervention response, to receive additional PCST sessions, maintenance calls, or no further intervention. Participants complete measures of pain intensity, interference and catastrophizing.

CONCLUSIONS

Novel RCT designs may provide information that can be used to optimize behavioral pain interventions to be adaptive, better meet patients' needs, reduce barriers, and match with clinical practice. This is one of the first trials to use a novel design to evaluate symptom management in cancer patients and in chronic illness; if successful, it could serve as a model for future work with a wide range of chronic illnesses.

Pregabalin for Neuropathic Pain: Why Benefits Could Be Expected for Multiple Pain Conditions

BACKGROUND AND OBJECTIVE

Limited research exists to support the extrapolation of the analgesic efficacy of pregabalin from one neuropathic pain condition to another. This retrospective analysis evaluated similarities in the efficacy of pregabalin for treating neuropathic pain associated with post-herpetic neuralgia (PHN), diabetic peripheral neuropathy (DPN), and spinal cord injury (SCI) in a Japanese population, as a basis for considering the extrapolation of these data to other neuropathic pain conditions.

METHODS

Data were analysed across pregabalin doses within each pain condition, from three comparable 13- to 16-week, randomized, double-blind, placebo-controlled trials (RCTs) and the corresponding 52-week, open-label extension trials of pregabalin in Japanese patients with PHN, DPN or SCI. Efficacy outcomes in the RCTs included endpoint and weekly mean pain and sleep interference scores; endpoint proportions of responders in pain; Patient Global Impression of Change scores; and 36-Item Short Form Health Survey (SF-36) scores or Hospital Anxiety and Depression Scale (HADS) assessments. Study discontinuation rates were compared between treatment groups. The extension trials assessed pain intensity, using the Short-Form McGill Pain Questionnaire.

RESULTS

In the RCTs for all pain conditions, significant improvements in comparison with placebo in mean pain and sleep interference scores were evident after 1 week with pregabalin and were sustained throughout the treatment periods (p < 0.05). At the study endpoint, in comparison with placebo, a significantly greater percentage of pregabalin-treated patients experienced a ≥30 % reduction in pain across the RCTs (p < 0.05), and pregabalin significantly improved six of 16 SF-36 subscale scores in the PHN and DPN trials (p < 0.05). In the SCI trial, pregabalin-treated patients had numerically better outcomes of HADS scores. In the extension trials, improvements in pain intensity were maintained over a 52-week period.

CONCLUSION

Similarities in the pregabalin efficacy profiles, including time to onset and magnitude of response, were confirmed regardless of the neuropathic pain condition. These data support the potential for extrapolating analgesic efficacy to other neuropathic pain conditions. CLINICALTRIALS.

GOV IDENTIFIERS

NCT00394901, NCT00553475, NCT00407745, NCT00424372, NCT00553280, NCT01202227.

Research design considerations for chronic pain prevention clinical trials: IMMPACT recommendations

Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.

A Pilot Study of a Mobile Health Pain Coping Skills Training Protocol for Patients With Persistent Cancer Pain

CONTEXT

Pain coping skills training (PCST) interventions have shown efficacy for reducing pain and providing other benefits in patients with cancer. However, their reach is often limited because of a variety of barriers (e.g., travel, physical burden, cost, time).

OBJECTIVES

This study examined the feasibility and acceptability of a brief PCST intervention delivered to patients in their homes using mobile health (mHealth) technology. Pre-to-post intervention changes in pain, physical functioning, physical symptoms, psychological distress, self-efficacy for pain management, and pain catastrophizing also were examined.

METHODS

Patients with a diagnosis of breast, lung, prostate, or colorectal cancer who reported persistent pain (N = 25) participated in a four-session intervention delivered using mHealth technology (videoconferencing on a tablet computer). Participants completed measures of pain, physical functioning, physical symptoms, psychological distress, self-efficacy for pain management, and pain catastrophizing. We also assessed patient satisfaction.

RESULTS

Participants completed an average of 3.36 (SD = 1.11) of the four intervention sessions for an overall session completion rate of 84%. Participants reported that the program was of excellent quality and met their needs. Significant preintervention to postintervention differences were found in pain, physical symptoms, psychological distress, and pain catastrophizing.

CONCLUSION

The use of mHealth technology is a feasible and acceptable option for delivery of PCST for patients with cancer. This delivery mode is likely to dramatically increase intervention access for cancer patients with pain compared to traditional in-person delivery. Preliminary data also suggest that the program is likely to produce pretreatment to post-treatment decreases in pain and other important outcomes.

Neuropathic pain: principles of diagnosis and treatment

Neuropathic pain is caused by disease or injury of the nervous system and includes various chronic conditions that, together, affect up to 8% of the population. A substantial body of neuropathic pain research points to several important contributory mechanisms including aberrant ectopic activity in nociceptive nerves, peripheral and central sensitization, impaired inhibitory modulation, and pathological activation of microglia. Clinical evaluation of neuropathic pain requires a thorough history and physical examination to identify characteristic signs and symptoms. In many cases, other laboratory investigations and clinical neurophysiological testing may help identify the underlying etiology and guide treatment selection. Available treatments essentially provide only symptomatic relief and may include nonpharmacological, pharmacological, and interventional therapies. Most extensive evidence is available for pharmacological treatment, and currently recommended first-line treatments include antidepressants (tricyclic agents and serotonin-norepinephrine reuptake inhibitors) and anticonvulsants (gabapentin and pregabalin). Individualized multidisciplinary patient care is facilitated by careful consideration of pain-related disability (eg, depression and occupational dysfunction) as well as patient education; repeat follow-up and strategic referral to appropriate medical/surgical subspecialties; and physical and psychological therapies. In the near future, continued preclinical and clinical research and development are expected to lead to further advancements in the diagnosis and treatment of neuropathic pain.

Screening for neuropathic characteristics in failed back surgery syndromes: challenges for guiding treatment

OBJECTIVE

Neuropathic pain screening tools have shown promise in identifying common neuropathic pain characteristics that derive from diverse etiologies (e.g., diabetic peripheral neuropathy, postherpetic neuralgia). However, no prior studies have specifically assessed whether these tools are capable of discerning the underlying pain mechanisms in the vast, heterogeneous group of patients diagnosed with failed back surgery syndrome (FBSS).

DESIGN

In this clinical observational study, two tests for neuropathic pain characteristics, the Douleur Neuropathique en 4 (DN4) and Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) questionnaires, were performed on 43 subjects with FBSS. Subjects underwent physical or neurosensory exam components of the DN4 and LANSS in the region of most severe pain (e.g., axial low back or lower extremities). DN4 and LANSS scores were correlated with clinical history and neurologic exam, pain-related quality of life questionnaires, and compared to an independent assessment of pain distribution.

RESULTS

The presence of neuropathic characteristics, determined by the DN4 (62% sensitivity, 44% specificity), LANSS (38% sensitivity, 75% specificity; cut-offs of 4 and 12, respectively), or their combination (20% sensitivity, 58% specificity) was associated with higher pain intensity as measured by the visual analog scale (DN4 > 4, P = 0.001; LANSS ≥ 12, P = 0.042), modified Brief Pain Inventory-Short Form (DN4 > 4, P = 0.001; LANSS ≥ 12, P = 0.082), and Neuropathic Pain Symptom Inventory (DN4 > 4, P = 0.001; LANSS ≥ 12, P = 0.001), and greater pain-related functional impairment as measured by the Roland-Morris Disability Questionnaire (DN4 > 4, P = 0.006; LANSS ≥ 12, P = 0.018). The percentage of subjects characterized as neuropathic by the DN4 and LANSS lacked concordance (67.4 vs. 25.6), and the distribution of most severe symptoms (i.e., axial vs radicular) did not correlate with subjects determined to have neuropathic pain.

CONCLUSIONS

Unlike other neuropathic syndromes, the neuropathic component of FBSS is less reliably identified by the LANSS and DN4.

Pharmacological management of chronic neuropathic pain: revised consensus statement from the Canadian Pain Society

BACKGROUND

Neuropathic pain (NeP), redefined as pain caused by a lesion or a disease of the somatosensory system, is a disabling condition that affects approximately two million Canadians.

OBJECTIVE

To review the randomized controlled trials (RCTs) and systematic reviews related to the pharmacological management of NeP to develop a revised evidence-based consensus statement on its management.

METHODS

RCTs, systematic reviews and existing guidelines on the pharmacological management of NeP were evaluated at a consensus meeting in May 2012 and updated until September 2013. Medications were recommended in the consensus statement if their analgesic efficacy was supported by at least one methodologically sound RCT (class I or class II) showing significant benefit relative to placebo or another relevant control group. Recommendations for treatment were based on the degree of evidence of analgesic efficacy, safety and ease of use.

RESULTS

Analgesic agents recommended for first-line treatments are gabapentinoids (gabapentin and pregabalin), tricyclic antidepressants and serotonin noradrenaline reuptake inhibitors. Tramadol and controlled-release opioid analgesics are recommended as second-line treatments for moderate to severe pain. Cannabinoids are now recommended as third-line treatments. Recommended fourth-line treatments include methadone, anticonvulsants with lesser evidence of efficacy (eg, lamotrigine, lacosamide), tapentadol and botulinum toxin. There is support for some analgesic combinations in selected NeP conditions.

CONCLUSIONS

These guidelines provide an updated, stepwise approach to the pharmacological management of NeP. Treatment should be individualized for each patient based on efficacy, side-effect profile and drug accessibility, including cost. Additional studies are required to examine head-to-head comparisons among analgesics, combinations of analgesics, long-term outcomes and treatment of pediatric, geriatric and central NeP.

Design, study quality and evidence of analgesic efficacy in studies of drugs in models of OA pain: a systematic review and a meta-analysis

OBJECTIVE

Studies using animal models are important in drug development, but often poorly predict treatment results in man. We investigated factors that may impact on the magnitude of the analgesic treatment effect in animal models of osteoarthritis (OA) pain.

DESIGN

Systematic review of studies that measured behavioural pain outcomes in small animal models of OA, and tested drugs which reduce OA pain in man. Standardised mean difference (SMD) and 95% confidence intervals (CIs) were calculated using random effects meta-analysis for selected models and drugs.

RESULTS

Most studies used rat models (42/50) and chemical methods of OA induction (39/50). Analgesic treatment effect (SMD) was most commonly measured between drug- and vehicle treated rats with knee OA. Meta-analysis was carried out for 102 such comparisons from 26 studies. The pooled SMD was 1.36 (95% CI = 1.15-1.57). Non-steroidal anti-inflammatory drugs (NSAIDs) were associated with smaller SMDs than opioids (z = -3.25, P = 0.001). Grip strength gave larger SMDs than assessment of static weight bearing (z = -4.60, P < 0.001), mechanically-evoked pain (z = -3.83, P = 0.001) and movement-evoked pain (z = -5.23, P < 0.001), and SMDs for mechanically-evoked pain were larger than for movement-evoked pain (z = -2.78, P = 0.006). Studies that reported structural evaluation of OA phenotype were associated with smaller SMDs (z = -2.45, P = 0.014). Publication was significantly biased towards positive findings.

CONCLUSION

Attention to study-level moderators and publication bias may improve the ability of research using animal models to predict whether analgesic agents will reduce arthritis pain in man.

Management options for established chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating condition associated with a variety of chemotherapeutic agents. Clinicians are cognizant of the negative impact of CIPN on cancer treatment outcomes and patients' psychosocial functioning and quality of life. In an attempt to alleviate this problem, clinicians and patients try various therapeutic interventions, despite limited evidence to support efficacy of these treatments. The rationale for such use is mostly based on the evidence for the treatment options in non-CIPN peripheral neuropathy syndromes, as this area is more robustly studied than is CIPN treatment. In this manuscript, we examine the existing evidence for both CIPN and non-CIPN treatments and develop a summary of the best available evidence with the aim of developing a practical approach to the treatment of CIPN, based on available literature and clinical practice experience.

Timing interventions in relation to temporomandibular joint closed lock duration: a systematic review of 'locking duration'

Temporomandibular joint (TMJ) 'closed lock' (CL) is a clinical condition causing TMJ pain and limited mouth opening (painful locking) that is mostly attributed to disc displacement without reduction (DDwoR), or less commonly to anchored disc phenomenon (ADP). Both conditions are described clinically as CL that can be 'acute' or 'chronic' depending on the duration of locking. There is, however, no consensus about the duration of locking that defines the acute state and its effect on the success of interventions. This review paper, therefore, aims to provide: (i) a narrative review of the pathophysiological need for early intervention in DDwoR and the clinical implications of acute/chronic CL stages on the management pathway; (ii) a systematic review investigating the effects of locking duration on the success of interventions for CL management. Electronic and manual searches until mid-August 2013 were conducted for English-language studies of any design investigating the effects of non-surgical and surgical interventions for acute or chronic CL (DDwoR or ADP). A total of 626 records were identified, and 113 studies were included. Data extraction and quality assessment were completed for all included studies. Included studies were, however, heterogeneous and mostly of poor-quality leading to contradictory and inconsistent evidence on the effect of the duration of locking on treatment outcomes. Future high-quality trials investigating the effect of CL duration on treatment outcome are needed. At present, early intervention by 'unlock' mandibular manipulation seems to be the most practical and realistic approach that can be attempted first in every CL patient as an initial diagnostic/therapeutic approach.

Neuropathic pain in cancer

Cancer-related neuropathic pain is common; it can be disease related or related to the acute or chronic effects of cancer treatment. For example, chemotherapy-induced peripheral neuropathy occurs in 90% of patients receiving neurotoxic chemotherapy. Cancer treatments have become more effective; patients are living longer with cancer and there are more cancer survivors. However, side-effects (particularly neuropathy) have become more problematic. The key to management of cancer-related neuropathy is a considered assessment, remembering not to miss the opportunity of reversing the cause of the pain with appropriate oncological management. An increasing range of oncological therapies are available, including radiotherapy, chemotherapy, hormonal therapy, or one of the evolving approaches (e.g. immune therapies). Patients are often elderly and with comorbidities; therefore, all treatment decisions have to be made carefully and reviewed appropriately. Cancer pain is often of mixed aetiology or, if purely neuropathic, may be one of several pains experienced by a patient. For these reasons, opioids are used more frequently in patients with cancer-related neuropathic pain. Standard guidelines for the use of anticonvulsants (e.g. pregabalin and gabapentin), antidepressants (e.g. duloxetine and tricyclics), and topical treatments (e.g. capsaicin and lidocaine) may be applicable, but there is a lack of good-quality clinical trials in cancer-related neuropathic pain. Choice is dictated not just by age, drug interactions, and comorbidities, but also by the coexistence of many symptoms in patients with cancer. Treating more than one symptom with a particular neuropathic pain agent can avoid polypharmacy.

Current challenges in translational pain research

The current gap between basic science research and the development of new analgesics presents a serious challenge for the future of pain medicine. This challenge is particularly difficult in the search for better treatment for comorbid chronic pain conditions because: (i) animal 'pain' models do not simulate multidimensional clinical pain conditions; (ii) animal behavioral testing does not assess subjective pain experience; (iii) preclinical data provide little assurance regarding the direction of new analgesic development; and (iv) clinical trials routinely use over-sanitized study populations and fail to capture the multidisciplinary consequences of comorbid chronic pain. Therefore, a paradigm shift in translational pain research is necessary to transform the current strategy from focusing on molecular switches of nociception to studying pain as a system-based integral response that includes psychosocial comorbidities. Several key issues of translational pain research are discussed in this review.

Considerations for improving assay sensitivity in chronic pain clinical trials: IMMPACT recommendations

A number of pharmacologic treatments examined in recent randomized clinical trials (RCTs) have failed to show statistically significant superiority to placebo in conditions in which their efficacy had previously been demonstrated. Assuming the validity of previous evidence of efficacy and the comparability of the patients and outcome measures in these studies, such results may be a consequence of limitations in the ability of these RCTs to demonstrate the benefits of efficacious analgesic treatments vs placebo ("assay sensitivity"). Efforts to improve the assay sensitivity of analgesic trials could reduce the rate of falsely negative trials of efficacious medications and improve the efficiency of analgesic drug development. Therefore, an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials consensus meeting was convened in which the assay sensitivity of chronic pain trials was reviewed and discussed. On the basis of this meeting and subsequent discussions, the authors recommend consideration of a number of patient, study design, study site, and outcome measurement factors that have the potential to affect the assay sensitivity of RCTs of chronic pain treatments. Increased attention to and research on methodological aspects of clinical trials and their relationships with assay sensitivity have the potential to provide the foundation for an evidence-based approach to the design of analgesic clinical trials and expedite the identification of analgesic treatments with improved efficacy and safety.