Is treatment of postherpetic neuralgia in the community consistent with evidence-based recommendations?

Genetic Evidence Indicates that Serum Micronutrient Levels Mediate the Causal Relationships Between Immune Cells and Neuropathic Pain: A Mediation Mendelian Randomization Study

A growing body of evidence suggests a correlation among immune cells, serum micronutrient levels, and neuropathic pain. However, previous studies have been limited in scope, hindering the establishment of conclusive findings. Therefore, this study employs mendelian randomization (MR) analysis to investigate the genetic perspectives on the causal relationships among these factors. Initially, the relationship between five serum micronutrient levels (specifically, four vitamin levels and zinc levels) and neuropathic pain was examined using a bidirectional MR design. Subsequently, positive results identified through the inverse variance weighted (IVW) method prompted further analysis, using immune cells as exposures to explore their causal links with neuropathic pain. As a result, a two-step MR analysis demonstrated that serum vitamin levels mediate the relationship between immune cells and neuropathic pain, quantifying both direct impacts and mediation effects. This study revealed that low serum levels of vitamin D and 25-hydroxyvitamin D increased the risk of postherpetic neuralgia and thoracic spine pain. Reverse MR analysis suggested that neuropathic pain does not contribute to a reduction in the serum levels of vitamin D and 25-hydroxyvitamin D. Furthermore, significant associations were observed between 27 immune cells and postherpetic neuralgia, as well as between 22 immune cells and thoracic spine pain. Additionally, the mediation analysis identified causal relationships between immune cells and serum micronutrient levels, confirming the "immune cells-serum micronutrient levels-neuropathic pain" pathway. This study provides valuable insights into the potential mechanisms by which vitamin D and 25-hydroxyvitamin D regulate the interaction between the immune system and neuropathic pain. These findings are crucial for the timely detection, treatment, and management of neuropathic pain, offering new perspectives on how vitamin levels influence immune cell behavior and neuropathic pain susceptibility.

Acupuncture therapies for postherpetic neuralgia: a protocol for a systematic review and Bayesian network meta-analysis

INTRODUCTION

Postherpetic neuralgia (PHN) is the most common sequela of herpes zoster, and it is often refractory to guideline-recommended treatments. Acupuncture therapy, a wildly applied complementary-alternative treatment, may help in the management of PHN. Diverse types of acupuncture therapy for PHN have been proposed, however, their comparative efficacies remain unclear. This study protocol plans to compare the efficacy and safety of different acupuncture therapies for PHN.

METHODS AND ANALYSIS

Databases including MEDLINE, Embase, Cochrane Library, Web of Science, Chinese Biomedical Database, China National Knowledge Infrastructure, VIP Database, Wanfang Database, WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, Chinese Clinical Trial Register and OpenGrey will be searched from their inception to January 2022. Randomised controlled trials (RCTs) assessing the effectiveness of acupuncture therapy on the management of PHN will be selected. The primary outcome is pain intensity. Secondary outcomes include negative emotions, sleep condition, quality of life and adverse events. Reviewers will conduct study selection, data extraction and risk of bias assessment procedures. Then, standard pair-wised meta-analysis and Bayesian network meta-analysis will be performed (if applicable). The Confidence in Network Meta-Analysis application will be used to assess the confidence in the evidence for the primary outcome.

ETHICS AND DISSEMINATION

All data used for this study will be extracted from published RCTs, thus, no ethical approval will be required. The results of this systematic review will be disseminated through peer-reviewed journal and conference presentation.

PROSPERO REGISTRATION NUMBER

CRD42020219576.

Fe3O4@Polydopamine-Labeled MSCs Targeting the Spinal Cord to Treat Neuropathic Pain Under the Guidance of a Magnetic Field

Purpose

Neuropathic pain causes great distress among patients; however, its response to traditional analgesia techniques remains sub-optimal. There has been progress in stem cell research for neuropathic pain treatment; however, effective homing remains problematic. This study aimed to establish Fe₃O₄@polydopamine(PDA)-labeled mesenchymal stem cells (MSCs); moreover, we aimed to guide MSCs using a magnetic field to the spinal cord segments showing pain-related responses to allow MSC homing and gathering, in advance, in order to fully employ their repair function.

Materials and Methods

Fe₃O₄@PDA-labeled MSCs were characterized using transmission electron microscopy. We analyzed the characteristics of MSCs, as well as the nanoparticle effects on MSC activity, differentiation, and proliferation, using the CCK-8 method, flow cytometry, and staining. Using rats, we performed behavioral tests of mechanical and thermal pain hypersensitivity. Serum inflammatory markers were detected using ELISA. Finally, changes in proteins associated with spinal cord pain were detected through quantitative reverse transcription PCR, histology, and immunohistochemistry.

Results

Fe₃O₄@PDA did not affect the characteristics and viability of MSCs. The magnetic field guidance improved the therapeutic effect of Fe₃O₄@PDA-labeled MSCs as indicated by the paw withdrawal threshold. Fe₃O₄@PDA-labeled MSCs decreased spinal nerve demyelination and c-Fos expression (a pain molecule); moreover, they inhibited microglia and astrocyte activation.

Conclusion

Fe₃O₄@PDA-labeled MSCs showed better homing to the spinal cord under magnetic field guidance. Moreover, they inhibited microglial and astrocyte activation, as well as played an early and continuous role in neuropathic pain treatment.

Pregabalin for neuropathic pain in primary care settings: recommendations for dosing and titration

Pregabalin is one of the first-line treatments approved for the management of neuropathic pain (NeP). While many patients benefit from treatment with pregabalin, they are often treated with suboptimal doses, possibly due to unfamiliarity around prescribing the drug and/or side effects that can occur with up-titration. This narrative review discusses key aspects of initiating, titrating, and managing patients prescribed pregabalin therapy, and addresses concerns around driving and the potential for abuse, as well as when to seek specialist opinion. To ensure that patients derive maximum therapeutic benefit from the drug, we suggest a 'low and slow' dosing approach to limit common side effects and optimize tolerability alongside patients' expectations. When requiring titration to higher doses, we recommend initiating 'asymmetric dosing,' with the larger dose in the evening. Fully engaging patients in order for them to understand the expected timeline for efficacy and side effects (including their resolution), can also help determine the optimal titration tempo for each individual patient. The 'low and slow' approach also recognizes that patients with NeP are heterogeneous in terms of their optimal therapeutic dose of pregabalin. Hence, it is recommended that general practitioners closely monitor patients and up-titrate according to pain relief and side effects to limit suboptimal dosing or premature discontinuation.

P2X receptors and trigeminal neuralgia

There is currently no effective cure for trigeminal neuralgia (TN) - a relatively common disease that causes long-term pain in patients. Previous research has shown that ionotropic ATP signaling through excitatory and calcium-permeable P2X receptor channels plays a critical role in pathological pain generation and maintenance. In this paper, we review several hypotheses on the pathogenic mechanisms underlying TN. We further discuss pathways or agents that can target P2X expression in TN, thereby affecting pain induction and maintenance.

Treatment Patterns and Medication Use in Patients with Postherpetic Neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is a chronic, painful condition characterized by persistent pain following resolution of a herpes zoster (HZ) infection. Epidemiologic data demonstrate that the risks for HZ infections and the development of PHN increase with age.

OBJECTIVE

To characterize prescribing patterns, health care utilization, and treatment costs for adults with PHN based on real-world data.

METHODS

This study analyzed medical and pharmacy claims from 2010 to 2014 in the MarketScan Commercial and Medicare Supplemental databases. PHN patients were identified based on criteria from a published algorithm. PHN treatment patterns were analyzed by age and reported descriptively for patients aged < 65 or ≥ 65 years. Excess incremental health care costs were calculated for PHN patients by comparing expenditures for a cohort of PHN patients to expenditures of a propensity score-matched control group of patients with HZ alone.

RESULTS

Approximately 0.4% of patients aged < 65 years were diagnosed with HZ versus 1.3% of patients aged ≥ 65 years; approximately 15.3% of HZ patients aged < 65 years and 26.4% of patients aged ≥ 65 years were diagnosed with PHN. Overall, opioids remained the most frequently prescribed initial treatment. Approximately 21.6% of PHN patients received an opioid as an initial treatment for PHN, 15.1% received gabapentin; 8.9% received a prescription nonsteroidal anti-inflammatory drug (NSAID); 8.3% received a lidocaine patch; 3.3% received pregabalin; 2.5% received a tricyclic antidepressants (TCAs); 0.8% received other topical lidocaine; and < 1% received capsaicin. Observed first-line use of the lidocaine patch and gabapentin was higher in patients aged ≥ 65 years relative to patients aged < 65 years. When separated by age group, only 24.6% of patients aged < 65 years and 38.5% of patients aged ≥ 65 years were prescribed a recommended first-line treatment for initial PHN therapy (gabapentin, lidocaine patch, pregabalin, and TCAs). Comparisons of treatment costs of PHN patients to matched HZ patients without PHN indicated that PHN patients initiated on opioids had the highest mean additional health care expenditure compared with PHN patients initiated on other medications. On average, PHN patients initiated on opioids had $7,601 additional health care expenditure compared with HZ patients with no PHN; additional expenditures were $6,428 for pregabalin, $4,213 for lidocaine patches, $3,478 for gabapentin, $3,304 for NSAIDs, and $2,797 for TCAs, respectively.

CONCLUSIONS

Management of PHN is associated with substantial utilization of opioid-based therapies across all ages. Medications supported by evidence either as first-line therapies or as part of a multimodal regimen for the management of PHN are underused relative to opioid-based PHN therapies. Improving adherence to evidence-based PHN treatment regimens offers the potential to reduce opioid prescribing first line and reduce overall treatment costs. Given the emphasis to reduce opioid prescribing to minimize the risk of dependence, abuse, and diversion, multimodal analgesic treatments that can avoid or reduce opioid use should be considered.

DISCLOSURES

Research funding was provided by SCILEX Pharmaceuticals. The sponsor reviewed and approved the research plan and provided support for manuscript preparation through Patel's role as a coauthor of this manuscript. The sponsor's product (lidocaine patch) was not used in this study. Patel is a paid employee of SCILEX Pharmaceuticals. Goss is an employee and minority owner of Boston Healthcare Associates, which received a research grant from SCILEX Pharmaceuticals to conduct this study. Gudin reports advisory board fees from AcelRx Pharmaceuticals and BioDelivery Sciences International and consulting fees from Averitas, Daiichi, Hisumitsu, Nektar, Purdue, Quest Diagnostics, SCILEX Pharmaceuticals, and US WorldMeds, unrelated to this study. Fudin reports advisory board fees from AcelRx Pharmaceuticals, Human Half-Cell, Quest Diagnostics, GlaxoSmithKline, SCILEX Pharmaceuticals, BioDelivery Sciences, Daiichi Sankyo, and Salix Pharmaceuticals; speaker fees from Daiichi Sankyo, Salix Pharmaceuticals, Abbott Laboratories, Acutis Diagnostics, and AstraZeneca; and consulting fees from Firstox Laboratories, unrelated to this study. The other authors have nothing to disclose. Parts of this research were presented at the AMCP Managed Care & Specialty Pharmacy Annual Meeting; April 22, 2016; San Francisco, CA, and at the 35th Annual Scientific Meeting of the American Pain Society; May 11-14, 2016; Austin, TX.

Differences in the miRNA signatures of chronic musculoskeletal pain patients from neuropathic or nociceptive origins

BACKGROUND

The quality of life for millions of people worldwide is affected by chronic pain. In addition to the effect of chronic pain on well-being, chronic pain has also been associated with poor health conditions and increased mortality. Due to its multifactorial origin, the classification of pain types remains challenging. MicroRNAs (miRNA) are small molecules that regulate gene expression. They are released into the bloodstream in a stable manner under normal and pathological conditions and have been described as potential biomarkers. In the present study, we aimed to investigate whether pain may induce an aberrant, specific dysregulation of miRNA expression, depending on the origin of the pain.

METHODS AND FINDINGS

To do so, we measured the expression changes of 184 circulating miRNAs (c-miRNAs) in the plasma samples of patients with different origins of chronic musculoskeletal pain. After statistical analyses, we identified seven c-miRNA candidates that were differentially expressed depending on the nociceptive or neuropathic origin of the pain. We then developed a two c-miRNA signature (hsa-miR-320a and hsa-miR-98-5p) that was able to correctly classify the pain type of 70% of the patients from the validation set.

CONCLUSIONS

In conclusion, circulating miRNAs are promising biomarkers to identify and characterize the chronic pain type and to further improve its clinical management.

Characteristics of patients with neuropathic pain syndromes screened by the painDETECT questionnaire and diagnosed by physician exam

Background

The aim of this study was to identify the clinical characteristics, treatment usage, and health outcomes of US adults diagnosed with neuropathic pain (NeP) by experienced physicians.

Methods

Adults with scores exceeding the threshold for probable NeP (painDETECT ≥19) and diagnosed with NeP by a qualified physician completed a questionnaire that included comorbid conditions, pain symptoms and experiences, medication use, health status (3-level EuroQol 5 Dimensions (EQ-5D-3L]: health utilities index and visual analog scale), pain severity and interference with functioning (Brief Pain Inventory), and work and activity impairment (Work Productivity and Activity Impairment questionnaire). Descriptive analyses were performed for each NeP subtype.

Results

Participants (n=295) were predominantly female (64.4%), middle-aged (53.9%), and white (51.5%). Chronic low back pain was the most frequently diagnosed major NeP syndrome (n=166), followed by diabetic peripheral neuropathy (n=58), post-trauma neuropathy (n=47), post-surgical neuropathy (n=28), and central NeP (n=23). An additional 45 participants were diagnosed, but did not meet the criteria for the aforementioned subtypes. Participants could be diagnosed with multiple subtypes. Across each NeP subtype, patients reported high rates of comorbid disease, including arthritis (range: 39.1%–64.3%) and high blood pressure (range: 26.1%–69.0%), as well as symptomology that included numbness (range: 68.1%–91.4%) and changes in muscular strength (range: 24.1%–65.2%). The majority of patients reported back pain (range: 77.8%–95.7%) and arthritis/joint pain (range: 68.1%–78.6%). The most commonly reported types of NeP pain medication were non-steroidal anti-inflammatory drugs (range: 43.1%–70.2%), weak opioids (range: 22.2%–39.3%), and strong opioids (range: 8.7%–28.6%). All six NeP groups generally reported similar levels of dysfunction on all self-report measures. The most notable finding was that the EuroQol-5D-3L health utilities index scores for each of the six groups were lower than the US norms by a clinically important amount.

Conclusion

These exploratory findings indicate that patients with NeP across different etiologies are medically complex and experience impaired function across multiple domains.

The utility/futility of medications for neuropathic pain – an observational study

Background and aims

The RELIEF (Real Life) study by AstraZeneca was designed as an observational study to validate a series of Patient Reported Outcome (PRO) questionnaires in a mixed population of subjects with neuropathic pain (NP) coming from diabetes, neurology and primary care clinics. This article is an analysis of a subset of the information to include the medications used and the effects of pharmacological treatment over 6 months. The RELIEF study was performed during 2010–2013.

Methods

Subjects were recruited from various specialty clinics and one general practice clinic across Canada. The subjects were followed for a total of 2 years with repeated documentation of their status using 10 PROs. A total of 210 of the recruited subjects were entered into the data base and analyzed. Of these, 123 had examination-verified painful diabetic neuropathy (PDN) and 87 had examination-verified post-traumatic neuropathy (PTN). To evaluate the responsiveness of the PROs to change, several time points were included and this study focusses primarily on the first 6 months. Subjects also maintained a diary to document all medications, both for pain and other medical conditions, including all doses, start dates and stop dates, that could be correlated to changes in the PRO parameters.

Results

RELIEF was successful in being able to correlate the validity of the PROs and this data was used for further AstraZeneca Phase 1, 2, and 3 clinical trials of NP. To our surprise, there was very little change in pain and low levels of patient satisfaction with treatment during the trial. Approximately 15% of the subjects reported improvement, 8% worsening of pain, the remainder reported pain unchanged despite the use of multiple medications at multiple doses, alone or in combination with frequent changes of medications and doses over the study. Those taking predominantly NSAIDs (COX-inhibitors) did no worse than those taking the standard recommended medications against NP.

Conclusions

Since this is a real-life study, it reflects the clinical utility of a variety of internationally recommended medications for the treatment of NP. In positive clinical trials of these medications in selected “ideal” subjects, the effects are not overwhelming – 30% are 50% improved on average. This study shows that in the real world the results are not nearly as positive and reflects information from non-published negative clinical trials.

Implications

We still do not have very successful medications for NP. Patients probably differ in many respects from those subjects in clinical trials. This is not to negate the use of recommended medications for NP but an indication that success rates of treatment are likely to be worse than the data coming from those trials published by the pharmaceutical industry.

Engineering Gain-of-Function Analogues of the Spider Venom Peptide HNTX-I, A Potent Blocker of the hNaV1.7 Sodium Channel

Pain is a medical condition that interferes with normal human life and work and reduces human well-being worldwide. The voltage-gated sodium channel (VGSC) human Na_V1.7 (hNa_V1.7) is a compelling target that plays a key role in human pain signaling. The 33-residue peptide µ-TRTX-Hhn2b (HNTX-I), a member of Na_V-targeting spider toxin (NaSpTx) family 1, has shown negligible activity on mammalian VGSCs, including the hNa_V1.7 channel. We engineered analogues of HNTX-I based on sequence conservation in NaSpTx family 1. Substitution of Asn for Ser at position 23 or Asp for His at position 26 conferred potent activity against hNa_V1.7. Moreover, multiple site mutations combined together afforded improvements in potency. Ultimately, we generated an analogue E1G⁻N23S⁻D26H⁻L32W with >300-fold improved potency compared with wild-type HNTX-1 on hNa_V1.7 (IC₅₀ 0.036 ± 0.007 µM). Structural simulation suggested that the charged surface and the hydrophobic surface of the modified peptide are responsible for binding affinity to the hNa_V1.7 channel, while variable residues may determine pharmacological specificity. Therefore, this study provides a profile for drug design targeting the hNa_V1.7 channel.

Pharmacological Regulation of Neuropathic Pain Driven by Inflammatory Macrophages

Neuropathic pain can have a major effect on quality of life but current therapies are often inadequate. Growing evidence suggests that neuropathic pain induced by nerve damage is caused by chronic inflammation. Upon nerve injury, damaged cells secrete pro-inflammatory molecules that activate cells in the surrounding tissue and recruit circulating leukocytes to the site of injury. Among these, the most abundant cell type is macrophages, which produce several key molecules involved in pain enhancement, including cytokines and chemokines. Given their central role in the regulation of peripheral sensitization, macrophage-derived cytokines and chemokines could be useful targets for the development of novel therapeutics. Inhibition of key pro-inflammatory cytokines and chemokines prevents neuroinflammation and neuropathic pain; moreover, recent studies have demonstrated the effectiveness of pharmacological inhibition of inflammatory (M1) macrophages. Nicotinic acetylcholine receptor ligands and T helper type 2 cytokines that reduce M1 macrophages are able to relieve neuropathic pain. Future translational studies in non-human primates will be crucial for determining the regulatory mechanisms underlying neuroinflammation-associated neuropathic pain. In turn, this knowledge will assist in the development of novel pharmacotherapies targeting macrophage-driven neuroinflammation for the treatment of intractable neuropathic pain.

Relationships Among Adverse Events, Disease Characteristics, and Demographics in Treatment of Postherpetic Neuralgia With Gastroretentive Gabapentin

Objectives:

To characterize risk factors for occurrence of adverse events (AEs) and treatment discontinuations due to AEs for improving safety and tolerability of treatment of postherpetic neuralgia (PHN).

Methods:

Patients with PHN (n=556) received 1800 mg once-daily gastroretentive gabapentin (G-GR) in 2 phase 3 and 1 phase 4 study. Safety assessments included the incidence and severity of AEs and analysis of discontinuations due to AEs. Multivariable, logistic regression analyses examined predictors of AE reporting and discontinuations due to AEs.

Results:

In total, 53.2% of patients reported any AE, and 12.9% discontinued because of AEs. Both AE incidence and treatment discontinuations decreased rapidly during the 2-week titration to sustained, low levels. The probability to report any AE was 0.6 for females versus 0.4 for males, whereas there were no differences in probabilities for age (less than 75 vs. 75 y and older) and race (nonwhite vs. white). Consistent with this, only female sex was a significant (P=0.0006) predictor of AE reporting. Experiencing moderate (P≤0.0001) or severe (P=0.0006) AEs, but not patient demographics, was predictive of treatment discontinuations. The probability of discontinuation due to moderate AEs was 0.4 and 0.5 for severe AEs.

Discussion:

The tolerability of G-GR was not affected by patient age, but was affected by AE severity. Although being female was predictive of reporting AEs, it did not influence treatment discontinuation. Given that PHN is a disease for which the risk and duration of PHN increases with age and with being female, G-GR appears to be a well-suited treatment option for PHN.

Neuropathic Pain Among Community-Dwelling Older People: A Clinical Study in Finland

BACKGROUND

Neuropathic pain is more common among older people than in the general population, and the efficacy of medical treatment often remains unsatisfactory.

OBJECTIVE

The aim of this study was to assess the presence, diagnostic certainty, etiology and treatment of neuropathic pain in community-dwelling older people with chronic pain.

METHODS

Independently living older people aged 75, 80 and 85 years subject to communal preventive home visits with chronic pain were invited to a clinical pain examination by a geriatrician.

RESULTS

Overall, 106 patients consented to participate in the clinical study. Neuropathic pain was diagnosed in 51 (48%) patients, with 75% of pain states definite and 25% probable neuropathic pain. The most common etiology was degenerative disease of the spinal column causing radiculopathy. At the study visit, 11 patients (22% of neuropathic pain patients) were receiving medication that was demonstrated to be effective against neuropathic pain. The geriatrician recommended a trial of a new medicine for 17 patients, but only six continued the medication going forward.

CONCLUSIONS

Neuropathic pain was surprisingly common in our cohort. Finding effective pain medication is challenging due to comorbidities, possible side effects, and vulnerability in older age. Other pain management methods should be considered.

Antiepileptics for post-herpetic neuralgia in the elderly: current and future prospects

Post-herpetic neuralgia is a painful condition and its prevalence increases with age. It is a burden for older patients and the association of age-related pharmacokinetic and pharmacodynamic changes, high co-morbidity and polypharmacy leads to the risk of adverse drug reactions and interactions. This type of neuropathic pain is particularly difficult to treat and guidelines recommend the use of gabapentinoids and some antidepressants, the utility of which may be hampered by adverse effects such as sedation, dizziness and impaired age-related renal function. Re-formulations of antiepileptics (anticonvulsants) are being developed and/or marketed and suggest interesting innovative profiles with improved bioavailability, low drug-drug interactions and better tolerability that need to be confirmed in future studies. However, there are no new antiepileptics being developed for post-herpetic neuralgia, and prospective studies specifically focused on the older population are still missing, while this age group is particularly at risk of developing shingles and chronic neuropathic pain with a deleterious impact on quality of life.

Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis

BACKGROUND

New drug treatments, clinical trials, and standards of quality for assessment of evidence justify an update of evidence-based recommendations for the pharmacological treatment of neuropathic pain. Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE), we revised the Special Interest Group on Neuropathic Pain (NeuPSIG) recommendations for the pharmacotherapy of neuropathic pain based on the results of a systematic review and meta-analysis.

METHODS

Between April, 2013, and January, 2014, NeuPSIG of the International Association for the Study of Pain did a systematic review and meta-analysis of randomised, double-blind studies of oral and topical pharmacotherapy for neuropathic pain, including studies published in peer-reviewed journals since January, 1966, and unpublished trials retrieved from ClinicalTrials.gov and websites of pharmaceutical companies. We used number needed to treat (NNT) for 50% pain relief as a primary measure and assessed publication bias; NNT was calculated with the fixed-effects Mantel-Haenszel method.

FINDINGS

229 studies were included in the meta-analysis. Analysis of publication bias suggested a 10% overstatement of treatment effects. Studies published in peer-reviewed journals reported greater effects than did unpublished studies (r(2) 9·3%, p=0·009). Trial outcomes were generally modest: in particular, combined NNTs were 6·4 (95% CI 5·2-8·4) for serotonin-noradrenaline reuptake inhibitors, mainly including duloxetine (nine of 14 studies); 7·7 (6·5-9·4) for pregabalin; 7·2 (5·9-9·21) for gabapentin, including gabapentin extended release and enacarbil; and 10·6 (7·4-19·0) for capsaicin high-concentration patches. NNTs were lower for tricyclic antidepressants, strong opioids, tramadol, and botulinum toxin A, and undetermined for lidocaine patches. Based on GRADE, final quality of evidence was moderate or high for all treatments apart from lidocaine patches; tolerability and safety, and values and preferences were higher for topical drugs; and cost was lower for tricyclic antidepressants and tramadol. These findings permitted a strong recommendation for use and proposal as first-line treatment in neuropathic pain for tricyclic antidepressants, serotonin-noradrenaline reuptake inhibitors, pregabalin, and gabapentin; a weak recommendation for use and proposal as second line for lidocaine patches, capsaicin high-concentration patches, and tramadol; and a weak recommendation for use and proposal as third line for strong opioids and botulinum toxin A. Topical agents and botulinum toxin A are recommended for peripheral neuropathic pain only.

INTERPRETATION

Our results support a revision of the NeuPSIG recommendations for the pharmacotherapy of neuropathic pain. Inadequate response to drug treatments constitutes a substantial unmet need in patients with neuropathic pain. Modest efficacy, large placebo responses, heterogeneous diagnostic criteria, and poor phenotypic profiling probably account for moderate trial outcomes and should be taken into account in future studies.

FUNDING

NeuPSIG of the International Association for the Study of Pain.

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.

Assessment and management of neuropathic pain in primary care

SUMMARY Most patients with neuropathic pain present and are managed in primary care. It is generally a long-term condition associated with poor physical, psychological and social health. Assessment and pharmacological treatment algorithms, specifically designed for primary care, are now available. The focus should be on taking a good medical history and clinical examination, and with the knowledge of the patient's current and past medical history, the general practitioner can diagnose possible neuropathic pain and initiate treatment while awaiting specialist assessment (if required). Specific nonpharmaceutical interventions, though popular with patients, have thus far demonstrated limited effectiveness. General practitioners, with their long-term relationship with patients, have a central role in improving the diagnosis and management of neuropathic pain.

Adherence of French GPs to chronic neuropathic pain clinical guidelines: results of a cross-sectional, randomized, "e" case-vignette survey

Background and aims

The French Pain Society published guidelines for neuropathic pain management in 2010. Our aim was to evaluate the compliance of GPs with these guidelines three years later.

Methods

We used “e” case vignette methodology for this non interventional study. A national panel of randomly selected GPs was included. We used eight “e” case-vignettes relating to chronic pain, differing in terms of the type of pain (neuropathic/non neuropathic), etiology (cancer, postoperative pain, low back pain with or without radicular pain, diabetes) and symptoms. GPs received two randomly selected consecutive “e” case vignettes (with/without neuropathic pain). We analyzed their ability to recognize neuropathic pain and to prescribe appropriate first-line treatment.

Results

From the 1265 GPs in the database, we recruited 443 (35.0%), 334 of whom logged onto the web site (26.4%) and 319 (25.2%) of whom completed the survey. Among these GPs, 170 (53.3%) were aware of the guidelines, 136 (42.6%) were able to follow them, and 110 (34.5%) used the DN4 diagnostic tool. Sensitivity for neuropathic pain recognition was 87.8% (CI: 84.2%; 91.4%). However, postoperative neuropathic pain was less well diagnosed (77.9%; CI: 69.6%; 86.2%) than diabetic pain (95.2%; CI: 90.0%; 100.0%), cancer pain (90.6%; CI: 83.5%; 97.8%) and typical radicular pain (90.7%; CI: 84.9%; 96.5%). When neuropathic pain was correctly recognized, the likelihood of appropriate first-line treatment prescription was 90.6% (CI: 87.4%; 93.8%). The treatments proposed were pregabaline (71.8%), gabapentine (43.9%), amiptriptylline (23.2%) and duloxetine (18.2%). However, ibuprofen (11%), acetaminophen-codeine (29.5%) and clonazepam (10%) were still prescribed.

Conclusions

The compliance of GPs with clinical practice guidelines appeared to be satisfactory, but differed between etiologies.

Ask the Experts: Neuropathic pain from a primary care perspective

Blair H Smith, MD, MEd, FRCGP, FRCP, Edin, qualified in medicine at the University of Glasgow (Scotland, UK) in 1987, and as a general practitioner in 1993. He is the Professor of Population Science at the University of Dundee (Scotland, UK), having previously been the Professor of Primary Care Medicine at the University of Aberdeen (Scotland, UK). He is also a general practitioner with the Peterhead Medical Practice (Aberdeenshire, Scotland, UK). His research on the epidemiology and primary care management of chronic (neuropathic) pain has been widely published with more than 100 original research articles in peer-reviewed medical journals, and numerous related book chapters. He leads a program of research, funded by the UK Medical Research Council, on the selfmanagement of chronic pain by older adults, and is also one of the Chief Investigators in Generation Scotland, a major family study for research into the genetics of health and illness, including pain. He is currently the Treasurer of the Neuropathic Pain Special Interest Group of the International Association for the Study of Pain and Director of the Scottish Pain Research Community.

Practical considerations in the pharmacological treatment of postherpetic neuralgia for the primary care provider

An estimated one million individuals in the US are diagnosed with herpes zoster (HZ; shingles) each year. Approximately 20% of these patients will develop postherpetic neuralgia (PHN), a complex HZ complication characterized by neuropathic pain isolated to the dermatome that was affected by the HZ virus. PHN is debilitating, altering physical function and quality of life, and commonly affects vulnerable populations, including the elderly and the immunocompromised. Despite the availability of an immunization for HZ prevention and several approved HZ treatments, the incidence of PHN is increasing. Furthermore, management of the neuropathic pain associated with PHN is often suboptimal, and the use of available therapeutics may be complicated by adverse effects and complex, burdensome treatment regimens, as well as by patients’ comorbidities and polypharmacy, which may lead to drug–drug interactions. Informed and comprehensive assessments of currently available pharmacological treatment options to achieve effective pain control in the primary care setting are needed. In this article, we discuss the situation in clinical practice, review currently recommended prevention and treatment options for PHN, and outline practical considerations for the management of this neuropathic pain syndrome, with a focus on optimal, individual-based treatment plans for use in the primary care setting.

Neuropathic pain in the general population: a systematic review of epidemiological studies

Most patients with neuropathic pain symptoms present and are managed in primary care, with only a minority being referred for specialist clinical assessment and diagnoses. Previous reviews have focused mainly on specific neuropathic pain conditions based in specialist settings. This is the first systematic review of epidemiological studies of neuropathic pain in the general population. Electronic databases were searched from January 1966 to December 2012, and studies were included where the main focus was on neuropathic pain prevalence and/or incidence, either as part of a specific neuropathic pain-related condition or as a global entity in the general population. We excluded studies in which data were extracted from pain or other specialist clinics or focusing on specific population subgroups. Twenty-one articles were identified and underwent quality assessment and data extraction. Included studies differed in 3 main ways: method of data retrieval, case ascertainment tool used, and presentation of prevalence/incidence rates. This heterogeneity precluded any meta-analysis. We categorised comparable incidence and prevalence rates into 2 main subgroups: (1) chronic pain with neuropathic characteristics (range 3-17%), and (2) neuropathic pain associated with a specific condition, including postherpetic neuralgia (3.9-42.0/100,000 person-years [PY]), trigeminal neuralgia (12.6-28.9/100,000 PY), painful diabetic peripheral neuropathy (15.3-72.3/100,000 PY), glossopharyngeal neuralgia (0.2-0.4/100,000 PY). These differences highlight the importance of a standardised approach for identifying neuropathic pain in future epidemiological studies. A best estimate of population prevalence of pain with neuropathic characteristics is likely to lie between 6.9% and 10%.

Antiepileptic drugs for neuropathic pain and fibromyalgia - an overview of Cochrane reviews

BACKGROUND

Antiepileptic drugs have been used for treating different types of neuropathic pain, and sometimes fibromyalgia. Our understanding of quality standards in chronic pain trials has improved to include new sources of potential bias. Individual Cochrane reviews using these new standards have assessed individual antiepileptic drugs. An early review from this group, originally published in 1998, was titled 'Anticonvulsants for acute and chronic pain'. This overview now covers the neuropathic pain aspect of that original review, which was withdrawn in 2009.

OBJECTIVES

To provide an overview of the relative analgesic efficacy of antiepileptic drugs that have been compared with placebo in neuropathic pain and fibromyalgia, and to report on adverse events associated with their use.

METHODS

We included reviews published in theCochrane Database of Systematic Reviews up to August 2013 (Issue 7). We extracted information from each review on measures of efficacy and harm, and methodological details concerning the number of participants, the duration of studies, and the imputation methods used, in order to judge potential biases in available data.We analysed efficacy data for each painful condition in three tiers, according to outcome and freedom from known sources of bias. The first tier met current best standards - at least 50% pain intensity reduction over baseline (or its equivalent), without the use of last observation carried forward (LOCF) for dropouts, an intention-to-treat (ITT) analysis, in parallel group studies with at least 200 participants lasting eight weeks or more. The second tier used data from at least 200 participants where one or more of the above conditions were not met. The third tier of evidence related to data from fewer than 200 participants, or with several important methodological problems that limited interpretation.

MAIN RESULTS

No studies reported top tier results.For gabapentin and pregabalin only we found reasonably good second tier evidence for efficacy in painful diabetic neuropathy and postherpetic neuralgia. In addition, for pregabalin, we found evidence of efficacy in central neuropathic pain and fibromyalgia. Point estimates of numbers needed to treat for an additional beneficial effect (NNTs) were in the range of 4 to 10 for the important outcome of pain intensity reduction over baseline of 50% or more.For other antiepileptic drugs there was no evidence (clonazepam, phenytoin), so little evidence that no sensible judgement could be made about efficacy (valproic acid), low quality evidence likely to be subject to a number of biases overestimating efficacy (carbamazepine), or reasonable quality evidence indicating little or no effect (lamotrigine, oxcarbazepine, topiramate). Lacosamide recorded such a trivial statistical superiority over placebo that it was unreliable to conclude that it had any efficacy where there was possible substantial bias.Any benefits of treatment came with a high risk of adverse events and withdrawal because of adverse events, but serious adverse events were not significantly raised, except with oxcarbazepine.

AUTHORS' CONCLUSIONS

Clinical trial evidence supported the use of only gabapentin and pregabalin in some neuropathic pain conditions (painful diabetic neuropathy, postherpetic neuralgia, and central neuropathic pain) and fibromyalgia. Only a minority of people achieved acceptably good pain relief with either drug, but it is known that quality of life and function improved markedly with the outcome of at least 50% pain intensity reduction. For other antiepileptic drugs there was no evidence, insufficient evidence, or evidence of a lack of effect; this included carbamazepine. Evidence from clinical practice and experience is that some patients can achieve good results with antiepileptics other than gabapentin or pregabalin.There is no firm evidence to answer the important pragmatic questions about which patients should have which drug, and in which order the drugs should be used. There is a clinical effectiveness research agenda to provide evidence about strategies rather than interventions, to produce the overall best results in a population, in the shortest time, and at the lowest cost to healthcare providers.

Neuropathic pain: a pathway for care developed by the British Pain Society

Neuropathic pain is a common chronic pain condition that can be challenging to treat, particularly for non-specialists. The development of the Map of Medicine care pathway for the management of neuropathic pain was led by the British Pain Society. Focusing on treatment by non-specialists, this pathway is based on new evidence, consensus, and the interests of service users. This paper presents the care pathway and accompanying evidence base, highlighting its salient features, and discussing important treatment points. After initial assessment, the pathway progresses through first-, second-, and third-line drug treatment, includes advice on topical treatment and opioids (in specific circumstances), and describes non-pharmacological approaches. Importantly, timely review of patients and referral to specialist secondary or tertiary care must be considered as vital components of the pathway. Although the emphasis was not on specialist treatment, advice is given on existing interventions, including neural stimulation and multi-disciplinary care. These, and other steps on the pathway, will be subject to further review as more evidence becomes available. In the meantime, the pathway represents a straightforward, valuable and accessible approach for healthcare professionals managing the distress and impact of neuropathic pain.

Neuropathic pain in the community: more under-treated than refractory?

Best current estimates of neuropathic pain prevalence come from studies using screening tools detecting pain with probable neuropathic features; the proportion experiencing significant, long-term neuropathic pain, and the proportion not responding to standard treatment are unknown. These “refractory” cases are the most clinically important to detect, being the most severe, requiring specialist treatment. The aim of this study was to estimate the proportion of neuropathic pain in the population that is “refractory,” and to quantify associated clinical and demographic features. We posted self-administered questionnaires to 10,000 adult patients randomly selected from 10 general practitioner practices in 5 UK locations. The questionnaire contained chronic pain identification and severity questions, cause of pain, SF-12, EQ-5D, S-LANSS (Self-administered Leeds Assessment of Neuropathic Signs and Symptoms), PSEQ (Pain Self-Efficacy Questionnaire), use of neuropathic pain medications, and health care utilisation. These data were combined to determine the presence and characteristics of “refractory” neuropathic pain according to the defining features identified by a Delphi survey of international experts. Graded categories of chronic pain with and without neuropathic characteristics were generated, incorporating the refractory criteria. Completed questionnaires were returned by 4451 individuals (response rate 47%); 399 had “chronic pain with neuropathic characteristics” (S-LANSS positive, 8.9% of the study sample); 215 (53.9%) also reported a positive relevant history (“Possible neuropathic pain”); and 98 (4.5% of all Chronic Pain) also reported an “adequate” trial of at least one neuropathic pain drug (“Treated possible neuropathic pain”). The most refractory cases were associated with dramatically poorer physical and mental health, lower pain self-efficacy, higher pain intensity and pain-related disability, and greater health care service use.