Combination of morphine with nortriptyline for neuropathic pain

Efficacy and safety of antidepressants for pain in older adults: A systematic review and meta-analysis

AIMS

In many countries, pain is the most common indication for use of antidepressants in older adults. We reviewed the evidence from randomized controlled trials on the efficacy and safety of antidepressants, compared to all alternatives for pain in older adults (aged ≥65 years).

METHODS

Trials published from inception to 1 February 2024, were retrieved from 13 databases. Two independent reviewers extracted data on study and participant characteristics, primary efficacy (pain scores, converted to 0-100 scale) and harms. Estimates for efficacy were pooled using a random effects model and reported as difference in means and 95% CI. Quality of included trials was assessed using the Cochrane risk of bias tool.

RESULTS

Fifteen studies (n = 1369 participants) met the inclusion criteria. The most frequently studied antidepressants were duloxetine and amitriptyline (6/15 studies each). Pain related to knee osteoarthritis was the most studied (6/15 studies). For knee osteoarthritis, antidepressants did not provide a statistically significant effect for the immediate term (0-2 weeks), (-5.6, 95% confidence interval [CI]: -11.5 to 0.3), but duloxetine provided a statistically significant, albeit a very small effect in the intermediate term, (≥6 weeks and <12 months), (-9.1, 95% CI: -11.8 to -6.4). Almost half (7/15) of the studies reported increased withdrawal of participants in the antidepressant treatment group vs. the comparator group due to adverse events.

CONCLUSIONS

For most chronic painful conditions, the benefits and harms of antidepressant medicines are unclear. This evidence is predominantly from trials with sample sizes of <100, have disclosed industry ties and classified as having unclear or high risk of bias.

Potentially harmful drug-drug interactions in the therapeutic regimens of persons with spinal cord injury

OBJECTIVES

Individuals with spinal cord injury deal with multiple health complications that require them to use many medications. The purpose of this paper was to find the most common potentially harmful drug-drug interactions (DDIs) in therapeutic regimens of persons with spinal cord injury, and the risk factors associated with it. We further highlight the relevance of each of the DDIs specific to spinal cord injury population.

DESIGN

Observational design and cross-sectional analysis.

SETTING

Community; Canada.

PARTICIPANTS

Individuals with spinal cord injury (n = 108).

MAIN OUTCOME MEASURES/ANALYSIS

The main outcome was the presence of one or more potential DDIs that can lead to an adverse outcome. All the reported drugs were classified as per the World Health Organization's Anatomical Therapeutic Chemical Classification system. Twenty potential DDIs were selected for the analysis based on the most common medications prescribed to people with spinal cord injury and severity of clinical consequences. The medication lists of study participants were analyzed for selected DDIs.

RESULTS

Among the 20 potential DDIs analyzed in our sample, the top 3 prevalent DDIs were Opioids + Skeletal Muscle Relaxants, Opioids + Gabapentinoids, and Benzodiazepines + ≥ 2 other central nervous system (CNS)-active drugs. Of the total sample of 108 respondents, 31 participants (29%) were identified with having at least one potential DDI. The risk of having a potential DDI was highly associated with polypharmacy, though no associations were found between the presence of a drug interaction and age, sex, level of injury, time since injury, or cause of injury among the study sample.

CONCLUSION

Almost three out of ten individuals with spinal cord injury were at risk of having a potentially harmful drug interaction. Clinical and communication tools are needed that facilitate identification and elimination of harmful drug combinations in the therapeutic regimens of patients with spinal cord injury.

Potential analgesic effect of a novel cannabidiol nanocrystals powder for the treatment of neuropathic pain

BACKGROUND

The current analgesics often prevent patients from getting effective treatment due to their adverse effects. Cannabidiol (CBD) is well tolerated, has few side effects and has been extensively investigated in analgesia. However, its oral bioavailability is extremely low. In order to solve this problem, we developed the cannabidiol nanocrystals (CBD-NC) in the earlier stage.

METHODS

In this study, we evaluated the nociceptive behaviours associated with neuropathic pain (NP) induced by the spared nerve injury (SNI) model. Assessment of pain threshold was evaluated by paw withdraw threshold (PWT) and paw withdrawal latency (PWL). The improving effect on the motor dysfunction was determined by rota-rod testing. To assess the neuroprotective effect, nerve demyelination and expression of peripheral myelin protein PMP22 were measured with myelin sheath staining and western blotting. Protein expressions in microglia of spinal cord were tested by western blot to explore the underlying mechanism.

RESULTS

Compared with the CBD oil solution, CBD-NC significantly reduced mechanical allodynia and thermal hyperalgesia in rats. CBD-NC could improve motor dysfunction induced by SNI in rats, significantly reverse the demyelination and increase the expression of the marker protein of peripheral myelin. Underlying spinal analgesic mechanism of microglia and related factors were preliminarily confirmed.

CONCLUSIONS

CBD-NC administration is an effective treatment for NP associated with SNI, and the analgesic effect of CBD-NC was significantly better than that of CBD oil sol. By contrast, CBD-NC has a fast-acting and long-term effect in the treatment of NP. Our study further supports the potential therapeutic effect of CBD-NC on NP.

SIGNIFICANCE

The absolute bioavailability of the CBD-NC intramuscular injection formulation can reach 203.31%, which can solve the problem of low oral bioavailability. This research evaluated the therapeutic effect of CBD-NC on NP associated with the SNI model for the first time. All available date showed that whatever the analgesic or neuroprotective effect of CBD-NC, it was significantly better than that of CBD oil sol., which was consistent with the results of the pharmacokinetic. This research supports the initiation of more trials testing the efficacy of CBD-NC for treating NP.

PRECISE trial (Pain RElief Combination Intervention StratEgies): protocol for the clinical trial of a pregabalin-melatonin combination for fibromyalgia

INTRODUCTION

Fibromyalgia is associated with chronic widespread pain and disturbed sleep. Multidisciplinary, multimodal management often includes pharmacotherapy; however, current drugs used to treat fibromyalgia provide meaningful benefit to only 30-60% of treated individuals. Combining two or more different drugs is common in clinical practice with the expectation of better efficacy, tolerability or both; however, further research is needed to identify which combinations actually provide added benefit. Thus, we are planning a clinical trial to evaluate melatonin (MLT)-pregabalin (PGB) combination in participants with fibromyalgia.

METHODS AND ANALYSIS

This will be a single-centre, double-blind, randomised, double-dummy, three-period, crossover trial comparing a MLT-PGB combination to each monotherapy in 54 adult participants satisfying the 2016 American College of Rheumatology criteria for fibromyalgia. Participants will receive maximally tolerated doses of MLT, PGB and MLT-PGB combination for 6 weeks. The primary outcome will be daily pain intensity (0-10); secondary outcomes will include the Fibromyalgia Impact Questionnaire, SF-36 survey, Medical Outcomes Study Sleep Scale, Beck Depression Inventory (BDI-II), adverse events and other measures. Analysis of the primary and secondary outcomes will involve a linear mixed model with sequence, period, treatment, the first-order carryover and baseline pain score as fixed effects and participant as a random effect to test whether there are any treatment differences among three treatments and to estimate the least square mean of the mean daily pain intensity for each treatment, adjusting for carryover as well as period effects (ie, stability of pain levels).

ETHICS AND DISSEMINATION

This trial has been registered with the International Standard Randomised Controlled Trial Number Registry, ISRCTN #18278231, has been granted ethical approval by the Queen's University Health Sciences Research Ethics Board (Queen's HSREB Protocol #6040998) and is currently under review for a Clinical Trial Application to Health Canada Natural and Non-prescription Health Products Directorate. All participants will provide written informed consent prior to trial participation. Following trial completion, results will be disseminated in one or more biomedical journal publications and presented at one or more scientific meetings.

TRIAL REGISTRATION NUMBER

This trial has been registered with the International Standard Randomised Controlled Trial Number Registry, ISRCTN18278231.

A systematic review and meta-analysis of randomized controlled head-to-head trials of recommended drugs for neuropathic pain

Neuropathic pain is a challenging chronic pain condition. Limited knowledge exists regarding the relative effectiveness of pharmacological treatments, and differences in trial design and impact of the placebo response preclude indirect comparisons of efficacy between drug classes. The purpose of this systematic review and meta-analysis of head-to-head trials was to compare the efficacy and tolerability of drugs recommended for neuropathic pain. We conducted a systematic review and meta-analysis of direct-comparison double-blind randomized trials. Primary outcomes were mean change in pain intensity and number of responders with a 50% reduction in pain intensity. Secondary outcomes encompassed quality of life, sleep, emotional functioning, and number of dropouts because of adverse events. We included 30 trials (4087 patients), comprising 16 crossover and 14 parallel-group design studies. All studies were conducted in adults, and the majority were investigator-initiated trials. We found moderate-quality evidence for equivalence (no clinically relevant difference) between tricyclic antidepressants (TCA) and gabapentin/pregabalin with a combined mean difference in pain score of 0.10 (95% CI -0.13 to 0.32). We could not document differences between TCA and serotonin-noradrenaline reuptake inhibitors (SNRI), between SNRI and gabapentin/pregabalin, or between opioids and TCA (low quality of evidence). We found more dropouts because of adverse events with SNRI and opioids compared with TCA (low quality of evidence). We did not identify any studies that included topical treatments. This systematic review of direct-comparison studies found evidence for equivalence between TCA and gabapentin/pregabalin and fewer dropouts with TCA than SNRI and opioids.

New Horizons in Diabetic Neuropathies: An Updated Review on their Pathology, Diagnosis, Mechanism, Screening Techniques, Pharmacological, and Future Approaches

BACKGROUND

One of the largest problems for global public health is diabetes mellitus (DM) and its micro and macrovascular consequences. Although prevention, diagnosis, and treatment have generally improved, its incidence is predicted to keep rising over the coming years. Due to the intricacy of the molecular mechanisms, which include inflammation, oxidative stress, and angiogenesis, among others, discovering treatments to stop or slow the course of diabetic complications is still a current unmet need.

METHODS

The pathogenesis and development of diabetic neuropathies may be explained by a wide variety of molecular pathways, hexosamine pathways, such as MAPK pathway, PARP pathway, oxidative stress pathway polyol (sorbitol) pathway, cyclooxygenase pathway, and lipoxygenase pathway. Although diabetic neuropathies can be treated symptomatically, there are limited options for treating the underlying cause.

RESULT

Various pathways and screening models involved in diabetic neuropathies are discussed, along with their possible outcomes. Moreover, both medicinal and non-medical approaches to therapy are also explored.

CONCLUSION

This study highlights the probable involvement of several processes and pathways in the establishment of diabetic neuropathies and presents in-depth knowledge of new therapeutic approaches intended to stop, delay, or reverse different types of diabetic complications.

Antidepressants for pain management in adults with chronic pain: a network meta-analysis

BACKGROUND

Chronic pain is common in adults, and often has a detrimental impact upon physical ability, well-being, and quality of life. Previous reviews have shown that certain antidepressants may be effective in reducing pain with some benefit in improving patients' global impression of change for certain chronic pain conditions. However, there has not been a network meta-analysis (NMA) examining all antidepressants across all chronic pain conditions.

OBJECTIVES

To assess the comparative efficacy and safety of antidepressants for adults with chronic pain (except headache).

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, AMED and PsycINFO databases, and clinical trials registries, for randomised controlled trials (RCTs) of antidepressants for chronic pain conditions in January 2022.

SELECTION CRITERIA

We included RCTs that examined antidepressants for chronic pain against any comparator. If the comparator was placebo, another medication, another antidepressant, or the same antidepressant at different doses, then we required the study to be double-blind. We included RCTs with active comparators that were unable to be double-blinded (e.g. psychotherapy) but rated them as high risk of bias. We excluded RCTs where the follow-up was less than two weeks and those with fewer than 10 participants in each arm.  DATA COLLECTION AND ANALYSIS: Two review authors separately screened, data extracted, and judged risk of bias. We synthesised the data using Bayesian NMA and pairwise meta-analyses for each outcome and ranked the antidepressants in terms of their effectiveness using the surface under the cumulative ranking curve (SUCRA). We primarily used Confidence in Meta-Analysis (CINeMA) and Risk of Bias due to Missing Evidence in Network meta-analysis (ROB-MEN) to assess the certainty of the evidence. Where it was not possible to use CINeMA and ROB-MEN due to the complexity of the networks, we used GRADE to assess the certainty of the evidence. Our primary outcomes were substantial (50%) pain relief, pain intensity, mood, and adverse events. Our secondary outcomes were moderate pain relief (30%), physical function, sleep, quality of life, Patient Global Impression of Change (PGIC), serious adverse events, and withdrawal.

MAIN RESULTS

This review and NMA included 176 studies with a total of 28,664 participants. The majority of studies were placebo-controlled (83), and parallel-armed (141). The most common pain conditions examined were fibromyalgia (59 studies); neuropathic pain (49 studies) and musculoskeletal pain (40 studies). The average length of RCTs was 10 weeks. Seven studies provided no useable data and were omitted from the NMA. The majority of studies measured short-term outcomes only and excluded people with low mood and other mental health conditions. Across efficacy outcomes, duloxetine was consistently the highest-ranked antidepressant with moderate- to high-certainty evidence. In duloxetine studies, standard dose was equally efficacious as high dose for the majority of outcomes. Milnacipran was often ranked as the next most efficacious antidepressant, although the certainty of evidence was lower than that of duloxetine. There was insufficient evidence to draw robust conclusions for the efficacy and safety of any other antidepressant for chronic pain.  Primary efficacy outcomes Duloxetine standard dose (60 mg) showed a small to moderate effect for substantial pain relief (odds ratio (OR) 1.91, 95% confidence interval (CI) 1.69 to 2.17; 16 studies, 4490 participants; moderate-certainty evidence) and continuous pain intensity (standardised mean difference (SMD) -0.31, 95% CI -0.39 to -0.24; 18 studies, 4959 participants; moderate-certainty evidence). For pain intensity, milnacipran standard dose (100 mg) also showed a small effect (SMD -0.22, 95% CI -0.39 to 0.06; 4 studies, 1866 participants; moderate-certainty evidence). Mirtazapine (30 mg) had a moderate effect on mood (SMD -0.5, 95% CI -0.78 to -0.22; 1 study, 406 participants; low-certainty evidence), while duloxetine showed a small effect (SMD -0.16, 95% CI -0.22 to -0.1; 26 studies, 7952 participants; moderate-certainty evidence); however it is important to note that most studies excluded participants with mental health conditions, and so average anxiety and depression scores tended to be in the 'normal' or 'subclinical' ranges at baseline already. Secondary efficacy outcomes Across all secondary efficacy outcomes (moderate pain relief, physical function, sleep, quality of life, and PGIC), duloxetine and milnacipran were the highest-ranked antidepressants with moderate-certainty evidence, although effects were small. For both duloxetine and milnacipran, standard doses were as efficacious as high doses. Safety There was very low-certainty evidence for all safety outcomes (adverse events, serious adverse events, and withdrawal) across all antidepressants. We cannot draw any reliable conclusions from the NMAs for these outcomes.

AUTHORS' CONCLUSIONS

Our review and NMAs show that despite studies investigating 25 different antidepressants, the only antidepressant we are certain about for the treatment of chronic pain is duloxetine. Duloxetine was moderately efficacious across all outcomes at standard dose. There is also promising evidence for milnacipran, although further high-quality research is needed to be confident in these conclusions. Evidence for all other antidepressants was low certainty. As RCTs excluded people with low mood, we were unable to establish the effects of antidepressants for people with chronic pain and depression. There is currently no reliable evidence for the long-term efficacy of any antidepressant, and no reliable evidence for the safety of antidepressants for chronic pain at any time point.

Combination analgesic development for enhanced clinical efficacy (the CADENCE trial): a double-blind, controlled trial of an alpha-lipoic acid-pregabalin combination for fibromyalgia pain

ABSTRACT

Drug therapy for fibromyalgia is limited by incomplete efficacy and dose-limiting adverse effects (AEs). Combining agents with complementary analgesic mechanisms-and differing AE profiles-could provide added benefits. We assessed an alpha-lipoic acid (ALA)-pregabalin combination with a randomized, double-blind, 3-period crossover design. Participants received maximally tolerated doses of ALA, pregabalin, and ALA-pregabalin combination for 6 weeks. The primary outcome was daily pain (0-10); secondary outcomes included Fibromyalgia Impact Questionnaire, SF-36 survey, Medical Outcomes Study Sleep Scale, Beck Depression Inventory (BDI-II), adverse events, and other measures. The primary outcome of daily pain (0-10) during ALA (4.9), pregabalin (4.6), and combination (4.5) was not significantly different (P = 0.54). There were no significant differences between combination and each monotherapy for any secondary outcomes, although combination and pregabalin were both superior to ALA for measures of mood and sleep. Alpha-lipoic acid and pregabalin maximal tolerated doses were similar during combination and monotherapy, and AEs were not frequent with combination therapy. These results do not support any additive benefit of combining ALA with pregabalin for fibromyalgia. The observation of similarly reached maximal tolerated drug doses of these 2 agents (which have differing side-effect profiles) during combination and monotherapy-without increased side effects-provides support for future development of potentially more beneficial combinations with complementary mechanisms and nonoverlapping side effects.

Combination pharmacotherapy for the treatment of neuropathic pain in adults: systematic review and meta-analysis

ABSTRACT

Neuropathic pain causes substantial morbidity and healthcare utilization. Monotherapy with antidepressants or anticonvulsants often fails to provide relief. Combining different drugs sometimes provides improved analgesia and/or tolerability. More than half of patients receive 2 or more analgesics, and combination trials continue to emerge. This review comprehensively searched CENTRAL, MEDLINE, and EMBASE for relevant trials. Included studies are double-blind randomized controlled trials evaluating combinations of 2 or more drugs vs placebo or at least one monotherapy in adults with neuropathic pain. Outcomes included measures of efficacy and adverse effects. Risk of bias was assessed. Meta-analyses compared combination to monotherapy wherever 2 or more similar studies were available. Forty studies (4741 participants) were included. Studies were heterogenous with respect to various characteristics, including dose titration methods and administration (ie, simultaneous vs sequential) of the combination. Few combinations involved a nonsedating drug, and several methodological problems were identified. For opioid-antidepressant, opioid-gabapentinoid, and gabapentinoid-antidepressant combinations, meta-analyses failed to demonstrate superiority over both monotherapies. In general, adverse event profiles were not substantially different for combination therapy compared with monotherapy. Despite widespread use and a growing number of trials, convincing evidence has not yet emerged to suggest superiority of any combination over its respective monotherapies. Therefore, implementing combination therapy-as second- or third-line treatment-in situations where monotherapy is insufficient, should involve closely monitored individual dosing trials to confirm safety and overall added benefit. Further research is needed, including trials of combinations involving nonsedating agents, and to identify clinical settings and specific combinations that safely provide added benefit.

Potential novel therapeutic strategies for neuropathic pain

Purpose

To explore the potential therapeutic strategies of different types of neuropathic pain (NP) and to summarize the cutting-edge novel approaches for NP treatment based on the clinical trials registered on ClinicalTrials.gov.

Methods

The relevant clinical trials were searched using ClinicalTrials.gov Dec 08, 2022. NP is defined as a painful condition caused by neurological lesions or diseases. All data were obtained and reviewed by the investigators to confirm whether they were related to the current topic.

Results

A total of 914 trials were included in this study. They were divided into painful diabetic neuropathy (PDN), postherpetic neuralgia (PHN), sciatica (SC), peripheral nerve injury-related NP (PNI), trigeminal neuralgia (TN), chemotherapy-induced NP (CINP), general peripheral NP (GPNP) and spinal cord injury NP (SCI-NP). Potential novel therapeutic strategies, such as novel drug targets and physical means, were discussed for each type of NP.

Conclusion

NP treatment is mainly dominated by drug therapy, and physical means have become increasingly popular. It is worth noting that novel drug targets, new implications of conventional medicine, and novel physical means can serve as promising strategies for the treatment of NP. However, more attention needs to be paid to the challenges of translating research findings into clinical practice.

Rationale and design of a multicenter randomized clinical trial of vestibulodynia: understanding pathophysiology and determining appropriate treatments (vestibulodynia: UPDATe)

BACKGROUND

Limited data are available to establish evidence-based management protocols for vestibulodynia (VBD), a chronic vulvar pain condition that affects approximately 14 million women in the U.S. For the purposes of the study, our group subdivided VBD subtypes that may benefit from different types of treatment: 1) VBD peripheral (VBD-p), characterized by pain localized to the vulvar vestibule and 2) VBD central (VBD-c), characterized by VBD alongside one or more other chronic overlapping pain conditions (e.g. irritable bowel syndrome, temporomandibular disorder, and fibromyalgia syndrome) that affect remote body regions. Here, we describe the rationale and design of an NIH-funded multicenter clinical trial comparing the effectiveness of topical and/or systemic medication for alleviating pain and normalizing pain- relevant biomarkers among women with VBD-p and VBD-c.

METHODS

Participants will be randomly assigned to one of four parallel arms: peripheral treatment with 5% lidocaine + 0.5 mg/ml 0.02% oestradiol compound cream + oral placebo pill, 2) central treatment with the tricyclic antidepressant nortriptyline + placebo cream, 3) combined peripheral cream and central pill treatments, or 4) placebo cream and placebo pill. The treatment phase will last 16 weeks, with outcome measures and biomarkers assessed at 4 time points (0, 8, 16, and 24 weeks). First, we will compare the efficacy of treatments in alleviating pain using standardized tampon insertion with a numeric rating scale and self-reported pain on the short form McGill Pain Questionnaire. Next, we will compare the efficacy of treatments in improving perceived physical, mental, and sexual health using standardized questionnaires. Finally, we will measure cytokines and microRNAs in local vaginal and circulating blood samples using multiplex assays and RNA sequencing, and determine the ability of these biomarkers to predict treatment response.

CONCLUSION

This is the first multicenter randomized controlled trial to evaluate the efficacy of peripherally and centrally acting medications currently used in clinical practice for treating unique VBD subtypes based on distinct clinical and biological signatures.

ADMINISTRATIVE INFORMATION

Vestibulodynia UPDATe is a multi-centre, two-by-two factorial designed randomized, double-blind, placebo-controlled trial registered at clinical trials.gov (NCT03844412). This work is supported by the R01 HD096331 awarded to Drs. Nackley, Rapkin, Geller and Carey by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).Key messagesPeripheral lidocaine and oestradiol and centrally-targeted nortriptyline medications are used for the treatment of pain in women with VBD, but there is a lack of data from well-powered RCTs.This two-by-two factorial RCT will test the efficacy of these medications in VBD subtypes characterized by distinct clinical characteristics and biomarker profiles.We hope that results will provide clinicians with scientific evidence of therapeutic efficacy in distinct VBD subtypes in an effort to direct and optimize treatment approaches.

The Role of the Locus Coeruleus in Pain and Associated Stress-Related Disorders

The locus coeruleus (LC)-noradrenergic system is the main source of noradrenaline in the central nervous system and is involved intensively in modulating pain and stress-related disorders (e.g., major depressive disorder and anxiety) and in their comorbidity. However, the mechanisms involving the LC that underlie these effects have not been fully elucidated, in part owing to the technical difficulties inherent in exploring such a tiny nucleus. However, novel research tools are now available that have helped redefine the LC system, moving away from the traditional view of LC as a homogeneous structure that exerts a uniform influence on neural activity. Indeed, innovative techniques such as DREADDs (designer receptors exclusively activated by designer drugs) and optogenetics have demonstrated the functional heterogeneity of LC, and novel magnetic resonance imaging applications combined with pupillometry have opened the way to evaluate LC activity in vivo. This review aims to bring together the data available on the efferent activity of the LC-noradrenergic system in relation to pain and its comorbidity with anxiodepressive disorders. Acute pain triggers a robust LC stress response, producing spinal cord-mediated endogenous analgesia while promoting aversion, vigilance, and threat detection through its ascending efferents. However, this protective biological system fails in chronic pain, and LC activity produces pain facilitation, anxiety, increased aversive memory, and behavioral despair, acting at the medulla, prefrontal cortex, and amygdala levels. Thus, the activation/deactivation of specific LC projections contributes to different behavioral outcomes in the shift from acute to chronic pain.

Pharmacological treatments of neuropathic pain: real-life comparisons using propensity score matching

ABSTRACT

Studies comparing different drug treatments for chronic neuropathic pain (NP) are very limited. We, therefore, examined 4 recommended treatments, namely, antidepressants (duloxetine, venlafaxine, and tricyclic antidepressants), antiepileptics (gabapentine and pregabalin), weak opioids, and strong opioids, among patients with NP evaluated before first visit in a tertiary pain treatment centre and 6 months later. Patients with both a clinical diagnosis of NP and a DN4 score ≥3/7 were selected from patients enrolled in the Quebec Pain Registry. Each participant was assigned an inverse weighting of the probability of receiving any NP treatment, taking into account their age, sex, baseline pain intensity, pain duration, pain catastrophizing tendency, education level, employment, and comedications at 6-month follow-up (M6). Patients were considered as improved if they presented at least a 30% reduction on average pain intensity at M6 compared with baseline. A total of 944 patients completed both baseline and M6 evaluations. Overall, 23.0% of patients were significantly improved for pain intensity at M6. There was no significant difference in proportions patients taking or not antidepressants, gabapentinoids, or weak opioids. Among patients taking strong opioids (N = 288), 13.9% (N = 40/288) were improved vs 27.0% (177/656) of those who were not on opioids (P < 0.004). Inverse probability of treatment weighting confirmed that the proportion of patients who improved was significantly lower among those taking strong opioids compared with those who did not (P < 0.001). In conclusion, long-term use of strong opioids is a treatment suited for a limited proportion of patients with chronic NP.

Screening, diagnosis and management of diabetic sensorimotor polyneuropathy in clinical practice: International expert consensus recommendations

Diabetic sensorimotor polyneuropathy (DSPN) affects around one third of people with diabetes and accounts for considerable morbidity, increased risk of mortality, reduced quality of life, and increased health care costs resulting particularly from neuropathic pain and foot ulcers. Painful DSPN is encountered in 13-26% of diabetes patients, while up to 50% of patients with DSPN may be asymptomatic. Unfortunately, DSPN still remains inadequately diagnosed and treated. Herein we provide international expert consensus recommendations and algorithms for screening, diagnosis, and treatment of DSPN in clinical practice derived from a Delphi process. Typical neuropathic symptoms include pain, paresthesias, and numbness particularly in the feet and calves. Clinical diagnosis of DSPN is based on neuropathic symptoms and signs (deficits). Management of DSPN includes three cornerstones: (1) lifestyle modification, optimal diabetes treatment aimed at near-normoglycemia, and multifactorial cardiovascular risk intervention, (2) pathogenetically oriented pharmacotherapy (e.g. α-lipoic acid and benfotiamine), and (3) symptomatic treatment of neuropathic pain including analgesic pharmacotherapy (antidepressants, anticonvulsants, opioids, capsaicin 8% patch and combinations, if required) and non-pharmacological options. Considering the individual risk profile, pain management should not only aim at pain relief, but also allow for improvement in quality of sleep, functionality, and general quality of life.

Nonopioid drug combinations for cancer pain: a systematic review

Pain is highly prevalent in patients with cancer-nearly 40% report moderate-severe pain, which is commonly treated with opioids. Increasing cancer survivorship, opioid epidemics in some regions of the world, and limited opioid access in other regions have focused attention on nonopioid treatments. Given the limitations of monotherapy, combining nonopioids-such as antiepileptics and antidepressants-have shown promise in noncancer pain. This review seeks to evaluate efficacy of nonopioid combinations for cancer-related pain. Systematic searches of PubMed, EMBASE, and Cochrane CENTRAL were conducted for double-blind, randomized, controlled trials comparing a nonopioid combination with at least one of its components and/or placebo. This search yielded 4 randomized controlled trials, published between 1998 and 2019 involving studies of (1) imipramine + diclofenac; (2) mitoxantrone + prednisone + clodronate; (3) pentoxifylline + tocopherol + clodronate; and (4) duloxetine + pregabalin + opioid. In the first 3 of these trials, trends favouring combination efficacy failed to reach statistical significance. However, in the fourth trial, duloxetine + pregabalin + opioid was superior to pregabalin + opioid. This review illustrates recognition for the need to evaluate nonopioid drug combinations in cancer pain, although few trials have been published to date. Given the growing practice of prescribing more than 1 nonopioid for cancer pain and the need to expand the evidence base for rational combination therapy, more high-quality trials in this area are needed.

Neuropathic Pain in Neurologic Disorders: A Narrative Review

Neuropathic pain is defined as a painful condition caused by neurological lesions or diseases. Sometimes, neurological disorders may also be associated with neuropathic pain, which can be challenging to manage. For example, multiple sclerosis (MS) may cause chronic centralized painful symptoms due to nerve damage. Other chronic neuropathic pain syndromes may occur in the form of post-stroke pain, spinal cord injury pain, and other central pain syndromes. Chronic neuropathic pain is associated with dysfunction, disability, depression, disturbed sleep, and reduced quality of life. Early diagnosis may help improve outcomes, and pain control can be an important factor in restoring function. There are more than 100 different types of peripheral neuropathy and those involving sensory neurons can provoke painful symptoms. Accurate diagnosis of peripheral neuropathy is essential for pain control. Further examples are represented by gluten neuropathy, which is an extraintestinal manifestation of gluten sensitivity and presents as a form of peripheral neuropathy; in these unusual cases, neuropathy may be managed with diet. Neuropathic pain has been linked to CoronaVirus Disease (COVID) infection both during acute infection and as a post-viral syndrome known as long COVID. In this last case, neuropathic pain relates to the host’s response to the virus. However, neuropathic pain may occur after any critical illness and has been observed as part of a syndrome following intensive care unit hospitalization.

Long-Term Opioid Use Following Surgery for Symptomatic Neuroma

BACKGROUND

 Identifying patients at risk for prolonged opioid use following surgery for symptomatic neuroma would be beneficial for perioperative management. The aim of this study is to identify the factors associated with postoperative opioid use of >4 weeks in patients undergoing neuroma surgery.

METHODS

 After retrospective identification, 77 patients who underwent surgery for symptomatic neuroma of the upper or lower extremity were enrolled. Patients completed the Patient-Reported Outcomes Measurement Information System (PROMIS) depression, Numeric Rating Scale (NRS) pain score, and a custom medication questionnaire at a median of 9.7 years (range: 2.5-16.8 years) following surgery. Neuroma excision followed by nerve implantation (n = 39, 51%), nerve reconstruction/repair (n = 18, 23%), and excision alone (n = 16, 21%) were the most common surgical treatments.

RESULTS

 Overall, 27% (n = 21) of patients reported opioid use of more than 4 weeks postoperatively. Twenty-three patients (30%) reported preoperative opioid use of which 11 (48%) did not report opioid use for >4 weeks, postoperatively. In multivariable logistic regression, preoperative opioid use was independently associated with opioid use of >4 weeks, postoperatively (odds ratio [OR] = 4.4, 95% confidence interval [CI]: 1.36-14.3, p = 0.013).

CONCLUSION

 Neuroma surgery reduces opioid use in many patients but patients who are taking opioids preoperatively are at risk for longer opioid use. Almost one-third of patients reported opioid use longer than 4 weeks, postoperatively.

The Treatment of Painful Diabetic Neuropathy

Painful diabetic peripheral neuropathy (painful-DPN) is a highly prevalent and disabling condition, affecting up to one-third of patients with diabetes. This condition can have a profound impact resulting in a poor quality of life, disruption of employment, impaired sleep, and poor mental health with an excess of depression and anxiety. The management of painful-DPN poses a great challenge. Unfortunately, currently there are no Food and Drug Administration (USA) approved disease-modifying treatments for diabetic peripheral neuropathy (DPN) as trials of putative pathogenetic treatments have failed at phase 3 clinical trial stage. Therefore, the focus of managing painful- DPN other than improving glycaemic control and cardiovascular risk factor modification is treating symptoms. The recommended treatments based on expert international consensus for painful- DPN have remained essentially unchanged for the last decade. Both the serotonin re-uptake inhibitor (SNRI) duloxetine and α2δ ligand pregabalin have the most robust evidence for treating painful-DPN. The weak opioids (e.g. tapentadol and tramadol, both of which have an SNRI effect), tricyclic antidepressants such as amitriptyline and α2δ ligand gabapentin are also widely recommended and prescribed agents. Opioids (except tramadol and tapentadol), should be prescribed with caution in view of the lack of definitive data surrounding efficacy, concerns surrounding addiction and adverse events. Recently, emerging therapies have gained local licenses, including the α2δ ligand mirogabalin (Japan) and the high dose 8% capsaicin patch (FDA and Europe). The management of refractory painful-DPN is difficult; specialist pain services may offer off-label therapies (e.g. botulinum toxin, intravenous lidocaine and spinal cord stimulation), although there is limited clinical trial evidence supporting their use. Additionally, despite combination therapy being commonly used clinically, there is little evidence supporting this practise. There is a need for further clinical trials to assess novel therapeutic agents, optimal combination therapy and existing agents to determine which are the most effective for the treatment of painful-DPN. This article reviews the evidence for the treatment of painful-DPN, including emerging treatment strategies such as novel compounds and stratification of patients according to individual characteristics (e.g. pain phenotype, neuroimaging and genotype) to improve treatment responses.

Neuropharmacological basis for multimodal analgesia in chronic pain

Managing chronic pain remains a major unmet clinical challenge. Patients can be treated with a range of interventions, but pharmacotherapy is the most common. These include opioids, antidepressants, calcium channel modulators, sodium channel blockers, and nonsteroidal anti-inflammatory drugs. Many of these drugs target a particular mechanism; however, chronic pain in many diseases is multifactorial and induces plasticity throughout the sensory neuroaxis. Furthermore, comorbidities such as depression, anxiety, and sleep disturbances worsen quality of life. Given the complexity of mechanisms and symptoms in patients, it is unsurprising that many fail to achieve adequate pain relief from a single agent. The efforts to develop novel drug classes with better efficacy have not always proved successful; a multimodal or combination approach to analgesia is an important strategy in pain control. Many patients frequently take more than one medication, but high-quality evidence to support various combinations is often sparse. Ideally, combining drugs would produce synergistic action to maximize analgesia and reduce side effects, although sub-additive and additive analgesia is still advantageous if additive side-effects can be avoided. In this review, we discuss pain mechanisms, drug actions, and the rationale for mechanism-led treatment selection.Abbreviations: COX - cyclooxygenase, CGRP - calcitonin gene-related peptide, CPM - conditioned pain modulation, NGF - nerve growth factor, NNT - number needed to treat, NMDA - N-methyl-d-aspartate, NSAID - nonsteroidal anti-inflammatory drugs, TCA - tricyclic antidepressant, SNRI - serotonin-noradrenaline reuptake inhibitor, QST - quantitative sensory testing.

[Diagnostics and therapy of neuropathic pain]

Neuropathic pain is pain caused by a lesion or disease of the somatosensory nervous system. Scientific studies have shown that neuropathic pain is the result of complex altered signalling processes in the peripheral and central nervous system. Current forms of treatment of neuropathic pain are causally oriented but also aim at symptomatic analgesia by pharmacological and nonpharmacological methods. Furthermore, psychological pain management techniques are used in a supportive role. This review summarizes the contemporary diagnostics of neuropathic pain using frequent diseases as examples and presents the evidence from randomized controlled trials on the treatment of neuropathic pain. Treatment guidelines for pharmacological management of neuropathic pain include evidence-based use of antidepressants, anticonvulsants, opioids, capsaicin and lidocaine.

Combination Therapy for Neuropathic Pain: A Review of Recent Evidence

Pharmacological treatment is not very effective for neuropathic pain (NP). A progressive decrease in the estimated effect of NP drugs has been reported, giving rise to an increase in the use of the multimodal analgesic approach. We performed a new independent review to assess whether more and better-quality evidence has become available since the last systematic review. We evaluated the efficacy, tolerability, and safety of double-blinded randomized controlled trials involving only adult participants and comparing combination therapy (CT: ≥2 drugs) with a placebo and/or at least one other comparator with an NP indication. The primary outcome assessed was the proportion of participants reporting ≥50% pain reductions from baseline. The secondary outcome assessed was the proportion of drop-outs due to treatment-emergent adverse events. After removing duplicates, 2323 citations were screened, with 164 articles assessed for eligibility, from which 16 were included for qualitative analysis. From the latter, only five lasted for at least 12 weeks and only six complied with the required data for complete analysis. CT has been adopted for years without robust evidence. Efforts have been made to achieve better-quality evidence, but the quality has not improved over the years. In this regard, guidelines for NP should attempt to make recommendations about CT research, prioritizing which combinations to analyze.

Treatment of neuropathic pain

Background: Neuropathic pain presents a therapeutic challenge because patients cannot be relieved from it, even when all known medical options have been tried. Several treatment guidelines have been provided, and several pharmacotherapies have been proposed with non-pharmacological treatments. This study aimed to present the current pharmacological and non-pharmacological treatments used to treat patients with neuropathic pain. Furthermore, several treatment guidelines for neuropathic pain are compared.Current Concepts: Tricyclic antidepressants, gabapentinoids, and serotonin-norepinephrine reuptake inhibitors are the first-line agents recommended by clinical guidelines in several countries. Tramadol and topical agents are recommended as second-line agents. Opioids and cannabinoids are recommended as third-line agents; cannabinoids are recommended by Canadian treatment guidelines. Combination therapy may be more effective because it results in synergistic pain-relieving effects, and the individual drug dose may be lower. Non-pharmacologic treatment is recommended as third-line or supplementary management because of the lack of evidence.Discussion and Conclusion: Several guidelines have recommended similar drugs; however, it is impossible to completely cure neuropathic pain. Therefore, therapeutic goals must be realistically discussed to improve patient compliance. In addition, additional studies based on pathophysiological mechanisms should be conducted to improve the management of neuropathic pain.

Expert review and recommendations for the management of acute, chronic, and neuropathic pain in Qatar

BACKGROUND

Pain management is an evolving area of expertise in Qatar. Gaps in knowledge, inadequate training for physicians and nurses, and the absence of policies/guidelines are the main barriers to effective pain management in Qatar. In addition, the use of certain pain medication, especially opioids, is highly regulated, limiting their availability in outpatient pain management. These factors are responsible for the undertreatment of pain in Qatar. This study aimed to standardize evidence-based local recommendations for pharmacological treatment of pain in Qatar.

METHODS

An expert panel of physicians from different disciplines, with experience in diagnosis and treatment of the three pain types (i.e., acute, chronic, and neuropathic), was convened for two face-to-face meetings in Doha, Qatar, on November 29, 2019, and on February 22, 2020, with subsequent virtual meetings. A literature search was performed on Medline and Google Scholar databases from inception till December 2019, and all relevant articles were selected. Based on these articles and repeated feedback from the authors, the final pain treatment protocols were developed.

RESULTS

Recommendations for the treatment of acute pain, based on pain severity, followed three approaches: acetaminophen/paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) for mild pain and moderate pain and referral to a pain specialist for severe pain. Acetaminophen/paracetamol or NSAIDs is recommended for chronic pain, and the use of opioids was strongly discouraged because of its long-term side effects. For neuropathic pain, tricyclic antidepressants or gabapentin or pregabalin or serotonin-norepinephrine reuptake inhibitors were recommended first-line agents. Non-responders must be referred to neurologists or a pain specialist.

CONCLUSION

The expert panel provides recommendations for the management of acute, chronic, and neuropathic pain based on international guidelines adapted to local practice and treatment availability in Qatar. More importantly, the panel has recommended taking extreme caution in the use of opioids for long-term management of chronic pain and to refer the patient to a pain specialist clinician as required.

Double-blind, randomized, placebo-controlled crossover trial of alpha-lipoic acid for the treatment of fibromyalgia pain: the IMPALA trial

ABSTRACT

Fibromyalgia is a common and challenging chronic pain disorder with few, if any, highly effective and well-tolerated treatments. Alpha-lipoic acid (ALA) is a nonsedating antioxidant with evidence of efficacy in the treatment of symptomatic diabetic neuropathy that has not been evaluated in the setting of fibromyalgia treatment. Thus, we conducted a single-centre, proof-of-concept, randomized, placebo-controlled, crossover trial of ALA for the treatment of fibromyalgia. Twenty-seven participants were recruited, and 24 participants completed both treatment periods of the trial. The median maximal tolerated dose of ALA in this trial was 1663 mg/day. Treatment-emergent adverse events with ALA were infrequent and not statistically different from placebo. For the primary outcome of pain intensity, and for several other validated secondary outcomes, there were no statistically significant differences between placebo and ALA. A post hoc exploratory subgroup analysis showed a significant interaction between gender and treatment with a significant favourable placebo-ALA difference in pain for men, but not for women. Overall, the results of this trial do not provide any evidence to suggest promise for ALA as an effective treatment for fibromyalgia, which is predominantly prevalent in women. This negative clinical trial represents an important step in a collective strategy to identify new, better tolerated and more effective treatments for fibromyalgia.

Pharmacotherapeutic Options for Managing Neuropathic Pain: A Systematic Review and Meta-Analysis

Despite an increasing number of available therapies, the treatment of neuropathic pain remains a major issue. Systematic reviews and meta-analyses indicate that only a minority of patients with neuropathic pain have an adequate response to pharmacological treatment and that most drugs have dose-limiting side effects. We conducted a systematic review and meta-analysis of randomised controlled trials published in the last five years. We searched for relevant papers within PubMed, EMBASE, the Cochrane Database of Systematic Reviews, and the Clinical Trials database (ClinicalTrials.gov). Two authors independently selected studies for inclusion, data extraction, and bias assessment. We identified 39 randomised controlled trials and included 16 in the meta-analysis. Trial outcomes were generally modest even for first-line drugs such as tricyclic antidepressants, serotonin-noradrenaline reuptake inhibitors, and gabapentinoids. Many drugs acting on new pain targets are currently under development. Clinical data are currently available for sodium channel isoform-specific antagonists, anti-nerve growth factor molecules, and fatty acid amide hydrolase inhibitors.

A functional polymorphism in the ATP-Binding Cassette B1 transporter predicts pharmacologic response to combination of nortriptyline and morphine in neuropathic pain patients

Many genetic markers have been associated with variations in treatment response to analgesics, but none have been assessed in the context of combination therapies. In this study, the treatment effects of nortriptyline and morphine were tested for an association with genetic markers relevant to pain pathways. Treatment effects were determined for single and combination therapies. A total of 24 functional single nucleotide polymorphisms were tested within the gene loci of mu-opioid receptor (OPRM1) gene locus, ATP-Binding Cassette B1 Transporter (ABCB1), Cytochrome P450 gene family (CYP2C19 and CYP2D6), catecholamine inactivator Catechol-O-Methyl Transferase (COMT), and serotonin receptor 2A (HTR2A). Genotyping was performed in a population of neuropathic pain patients who previously participated in a clinical trial. For monotherapy, neither nortriptyline nor morphine responses were associated with single nucleotide polymorphisms. However, for nortriptyline + morphine combination therapy, the single nucleotide polymorphism rs1045642 within the drug efflux pump ABCB1 transporter significantly predicted analgesic response. The presence of the C allele accounted for 51% of pain variance in this subgroup in response to combination treatment. The T-allele homozygotes demonstrated only 20% improvement in pain scores, whereas the C-allele homozygotes 88%. There was no significant contribution of rs1045642 to the medication side effects under all treatment conditions. The UK Biobank data set was then used to validate this genetic association. Here, patients receiving similar combination therapy (opioid + tricyclic antidepressant) carrying the C allele of rs1045642 displayed 33% fewer body pain sites than patients without that allele, suggesting better pain control. In all, our results show a robust effect of the rs1045642 polymorphism in response to chronic pain treatment with a nortriptyline + morphine combination.

Nonopioid drug combinations for cancer pain: protocol for a systematic review

This protocol will guide a review of clinical trials that evaluate the efficacy and safety of nonopioid analgesic drug combinations for the management of cancer-related pain.

Introduction:

Pain related to cancer, and its treatment, is common, may severely impair quality of life, and imposes a burden on patients, their families and caregivers, and society. Cancer-related pain is often challenging to manage, with limitations of analgesic drugs including incomplete efficacy and dose-related adverse effects.

Objectives:

Given problems with, and limitations of, opioid use for cancer-related pain, the identification of nonopioid treatment strategies that could improve cancer pain care is an attractive concept. The hypothesis that combinations of mechanistically distinct analgesic drugs could provide superior analgesia and/or fewer adverse effects has been tested in several pain conditions, including in cancer-related pain. Here, we propose to review trials of nonopioid analgesic combinations for cancer-related pain.

Methods:

Using a predefined literature search strategy, trials—comparing the combination of 2 or more nonopioid analgesics with at least one of the combination's individual components—will be searched on the PubMed and EMBASE databases from their inception until the date the searches are run. Outcomes will include pain intensity or relief, adverse effects, and concomitant opioid consumption.

Results/Conclusions:

This review is expected to synthesize available evidence describing the efficacy and safety of nonopioid analgesic combinations for cancer-related pain. Furthermore, a review of this literature will serve to identify future research goals that would advance our knowledge in this area.

The use of antineuropathic medications for the treatment of chronic pain

Chronic pain syndromes cost the US healthcare system over $600 billion per year. A subtype of chronic pain is neuropathic pain (NP), which is defined as "pain caused by a lesion or disease of the somatosensory system," according to the International Association for the Study of Pain (IASP). The pathophysiology of neuropathic pain is very complex, and more research needs to be done to find the exact mechanism. Patients that have preexisting conditions such as cancer and diabetes are at high-risk of developing NP. Many NP patients are misdiagnosed and receive delayed treatment due to a lack of a standardized classification system that allows clinicians to identify, understand, and utilize pain management in these patients. Medications like tricyclic antidepressants, serotonin-norepinephrine reuptake Inhibitor (SNRIs), and gabapentinoids are first-line treatments followed by opioids, cannabinoids, and other drugs. There are limited studies on the treatment of NP.

Pharmacological and non-pharmacological treatments for neuropathic pain: Systematic review and French recommendations

Neuropathic pain remains a significant unmet medical need. Several recommendations have recently been proposed concerning pharmacotherapy, neurostimulation techniques and interventional management, but no comprehensive guideline encompassing all these treatments has yet been issued. We performed a systematic review of pharmacotherapy, neurostimulation, surgery, psychotherapies and other types of therapy for peripheral or central neuropathic pain, based on studies published in peer-reviewed journals before January 2018. The main inclusion criteria were chronic neuropathic pain for at least three months, a randomized controlled methodology, at least three weeks of follow-up, at least 10 patients per group, and a double-blind design for drug therapy. Based on the GRADE system, we provide weak-to-strong recommendations for use and proposal as a first-line treatment for SNRIs (duloxetine and venlafaxine), gabapentin and tricyclic antidepressants and, for topical lidocaine and transcutaneous electrical nerve stimulation specifically for peripheral neuropathic pain; a weak recommendation for use and proposal as a second-line treatment for pregabalin, tramadol, combination therapy (antidepressant combined with gabapentinoids), and for high-concentration capsaicin patches and botulinum toxin A specifically for peripheral neuropathic pain; a weak recommendation for use and proposal as a third-line treatment for high-frequency rTMS of the motor cortex, spinal cord stimulation (failed back surgery syndrome and painful diabetic polyneuropathy) and strong opioids (in the absence of an alternative). Psychotherapy (cognitive behavioral therapy and mindfulness) is recommended as a second-line therapy, as an add-on to other therapies. An algorithm encompassing all the recommended treatments is proposed.

Dynamic Brain Activity Following Auricular Point Acupressure in Chemotherapy-Induced Neuropathy: A Pilot Longitudinal Functional Magnetic Resonance Imaging Study

Background

The objective of this study was to investigate the dynamic brain activity following auricular point acupressure (APA) in chemotherapy-induced neuropathy (CIN).

Methods

Participants received 4 weeks of APA in an open-pilot trial with repeated observation. Along with the clinical self-reported CIN outcomes, objective outcomes were measured over the course of the treatment by physiological changes in pain sensory thresholds from quantitative sensory testing (QST) and repeated functional magnetic resonance imaging scans.

Results

After 4 weeks of APA, participants had reported clinically significant improvements (ie, ≥30%) in a reduction of CIN symptoms (including pain, numbness, tingling, and stiffness) in lower extremity stiffness (32%), reduced foot sensitivity (13%), and higher pain threshold (13%). Across the 11 intrinsic brain networks examined, there was a trend toward significance of the connectivity of the basal ganglia network (BGN) to the salience network (SAL), which was decreased pre-APA versus immediate-APA (effect size [ES] = 1.04, P = .07). The BGN also demonstrated decreased connectivity with the language network pre-APA versus delayed imaging post-APA (ES = −0.92, P = .07). Furthermore, there was increased executive control network (ECN) and SAL within-network connectivity comparing pre-APA to delayed imaging post-APA, trending toward significance (ES = 0.41, P = .09 and ES = 0.17, P = .09, respectively).

Conclusion

The changes in connectivity and activity within or between the ECN, SAL, and BGN from pre- to post-APA suggest ongoing alterations in brain functional connectivity following APA, particularly in the insula, anterior cingulate, and dorsolateral prefrontal cortices, which play significant roles in pain, memory, and cognitive function.

[Update in the pharmacological treatment of neuropathic pain]

We provide an updated review of the pharmacological treatment of neuropathic pain, with emphasis on the latest evidence-based recommendations. Drugs proposed as first line include tricyclic antidepressants (particularly amitriptyline), serotonin-noradrenaline reuptake inhibitors (particularly duloxetine), pregabalin and gabapentin. Second-line treatments include 5% lidocaine medicated plasters and capsaicin 8% patches, only for peripheral neuropathic pain and tramadol; whereas potent opioids and botulinum toxin A (for peripheral neuropathic pain) are considered third-line treatments. Future perspectives include the development of new drugs and a more personalised therapeutic approach, which is made possible by recent progress in the assessment and understanding of neuropathic pain.

Preliminary Effectiveness of Auricular Point Acupressure on Chemotherapy-Induced Neuropathy: Part 1 Self-Reported Outcomes

PURPOSE

To reduce chemotherapy-induced neuropathy (CIN)-a significant challenge among cancer patients following chemotherapy-we explored the effects of auricular point acupressure (APA), which involves needleless, acupuncture-like stimulation on specific ear points.

DESIGN/METHOD

This pilot study examined the effects of a 4-week APA intervention in the management of CIN. Descriptive analysis was used to examine the changes in study outcomes.

RESULTS

Fifteen participants were enrolled. Two participants dropped out because they developed new medical conditions. Thirteen participants completed the study (87% retention rate). Study participants had more severe symptoms in their lower extremities (i.e., toes, feet, soles) than in their upper extremities (i.e., fingers, wrists, elbows). After the 4-week APA intervention, the mean percentage change scores ranged from 38% (tingling) to 49% (numbness); compared to pre-intervention, the therapeutic effects of APA were sustained at the 1-month follow-up. Function in both upper and lower extremities improved after the APA intervention (≥28%) and continued to improve at the 1-month follow-up (≥36%).

CONCLUSIONS

Preliminary results from this small sample provide initial evidence of the effectiveness of APA on CIN. Future studies should confirm these results using a larger sample, a comparative sham control, and an examination of the underlying physiological mechanisms of the anti-CIN effects of APA.

CLINICAL IMPLICATIONS

APA may provide an inexpensive and effective complementary approach for the self-management of CIN. Once the seeds have been taped to the patient's ear by the provider, patients are empowered to self-manage their CIN in their own environment.

Designing and conducting proof-of-concept chronic pain analgesic clinical trials

Introduction:

The evolution of pain treatment is dependent on successful development and testing of interventions. Proof-of-concept (POC) studies bridge the gap between identification of a novel target and evaluation of the candidate intervention's efficacy within a pain model or the intended clinical pain population.

Methods:

This narrative review describes and evaluates clinical trial phases, specific POC pain trials, and approaches to patient profiling.

Results:

We describe common POC trial designs and their value and challenges, a mechanism-based approach, and statistical issues for consideration.

Conclusion:

Proof-of-concept trials provide initial evidence for target use in a specific population, the most appropriate dosing strategy, and duration of treatment. A significant goal in designing an informative and efficient POC study is to ensure that the study is safe and sufficiently sensitive to detect a preliminary efficacy signal (ie, a potentially valuable therapy). Proof-of-concept studies help avoid resources wasted on targets/molecules that are not likely to succeed. As such, the design of a successful POC trial requires careful consideration of the research objective, patient population, the particular intervention, and outcome(s) of interest. These trials provide the basis for future, larger-scale studies confirming efficacy, tolerability, side effects, and other associated risks.

Opioid Adjuncts: Optimizing Opioid Therapy With Nonopioid Medications

In this article, we describe a variety of medications that physicians managing outpatient chronic pain should familiarize themselves with to better aid their approach to multimodal pain therapy. Physicians should always consider the use of an adjuvant or coanalgesic drug as first-line treatments. Although many of these medications are not primarily analgesics, in clinical practice they have independent analgesic effects or synergistic analgesic properties when used with opioids. The use of adjunct analgesics reduces opioid-related adverse effects and optimizes pain management. Although there may be some medication overlap with this section and the ERAS section, the purpose of this article is to understand prolonged use in the outpatient setting to reduce opioid use or limit opioid dose with adjuvant therapy.

Monoamines as Drug Targets in Chronic Pain: Focusing on Neuropathic Pain

Monoamines are involved in regulating the endogenous pain system and indeed, peripheral and central monoaminergic dysfunction has been demonstrated in certain types of pain, particularly in neuropathic pain. Accordingly, drugs that modulate the monaminergic system and that were originally designed to treat depression are now considered to be first line treatments for certain types of neuropathic pain (e.g., serotonin and noradrenaline (and also dopamine) reuptake inhibitors). The analgesia induced by these drugs seems to be mediated by inhibiting the reuptake of these monoamines, thereby reinforcing the descending inhibitory pain pathways. Hence, it is of particular interest to study the monoaminergic mechanisms involved in the development and maintenance of chronic pain. Other analgesic drugs may also be used in combination with monoamines to facilitate descending pain inhibition (e.g., gabapentinoids and opioids) and such combinations are often also used to alleviate certain types of chronic pain. By contrast, while NSAIDs are thought to influence the monoaminergic system, they just produce consistent analgesia in inflammatory pain. Thus, in this review we will provide preclinical and clinical evidence of the role of monoamines in the modulation of chronic pain, reviewing how this system is implicated in the analgesic mechanism of action of antidepressants, gabapentinoids, atypical opioids, NSAIDs and histaminergic drugs.

Opioids for Chronic Noncancer Pain: A Systematic Review and Meta-analysis

IMPORTANCE

Harms and benefits of opioids for chronic noncancer pain remain unclear.

OBJECTIVE

To systematically review randomized clinical trials (RCTs) of opioids for chronic noncancer pain.

DATA SOURCES AND STUDY SELECTION

The databases of CENTRAL, CINAHL, EMBASE, MEDLINE, AMED, and PsycINFO were searched from inception to April 2018 for RCTs of opioids for chronic noncancer pain vs any nonopioid control.

DATA EXTRACTION AND SYNTHESIS

Paired reviewers independently extracted data. The analyses used random-effects models and the Grading of Recommendations Assessment, Development and Evaluation to rate the quality of the evidence.

MAIN OUTCOMES AND MEASURES

The primary outcomes were pain intensity (score range, 0-10 cm on a visual analog scale for pain; lower is better and the minimally important difference [MID] is 1 cm), physical functioning (score range, 0-100 points on the 36-item Short Form physical component score [SF-36 PCS]; higher is better and the MID is 5 points), and incidence of vomiting.

RESULTS

Ninety-six RCTs including 26 169 participants (61% female; median age, 58 years [interquartile range, 51-61 years]) were included. Of the included studies, there were 25 trials of neuropathic pain, 32 trials of nociceptive pain, 33 trials of central sensitization (pain present in the absence of tissue damage), and 6 trials of mixed types of pain. Compared with placebo, opioid use was associated with reduced pain (weighted mean difference [WMD], -0.69 cm [95% CI, -0.82 to -0.56 cm] on a 10-cm visual analog scale for pain; modeled risk difference for achieving the MID, 11.9% [95% CI, 9.7% to 14.1%]), improved physical functioning (WMD, 2.04 points [95% CI, 1.41 to 2.68 points] on the 100-point SF-36 PCS; modeled risk difference for achieving the MID, 8.5% [95% CI, 5.9% to 11.2%]), and increased vomiting (5.9% with opioids vs 2.3% with placebo for trials that excluded patients with adverse events during a run-in period). Low- to moderate-quality evidence suggested similar associations of opioids with improvements in pain and physical functioning compared with nonsteroidal anti-inflammatory drugs (pain: WMD, -0.60 cm [95% CI, -1.54 to 0.34 cm]; physical functioning: WMD, -0.90 points [95% CI, -2.69 to 0.89 points]), tricyclic antidepressants (pain: WMD, -0.13 cm [95% CI, -0.99 to 0.74 cm]; physical functioning: WMD, -5.31 points [95% CI, -13.77 to 3.14 points]), and anticonvulsants (pain: WMD, -0.90 cm [95% CI, -1.65 to -0.14 cm]; physical functioning: WMD, 0.45 points [95% CI, -5.77 to 6.66 points]).

CONCLUSIONS AND RELEVANCE

In this meta-analysis of RCTs of patients with chronic noncancer pain, evidence from high-quality studies showed that opioid use was associated with statistically significant but small improvements in pain and physical functioning, and increased risk of vomiting compared with placebo. Comparisons of opioids with nonopioid alternatives suggested that the benefit for pain and functioning may be similar, although the evidence was from studies of only low to moderate quality.

Care After Chemotherapy: Peripheral Neuropathy, Cannabis for Symptom Control, and Mindfulness

As cancer therapies improve, patients are living longer. With these improvements in therapy comes a responsibility to optimize patients' quality of life during cancer therapy and beyond. This report reviews three timely and important topics. The first section reviews the mechanism underlying chemotherapy-induced peripheral neuropathy and evaluates the evidence for interventions to prevent and treat peripheral neuropathy. It also provides a framework for approaching the diagnosis and management of this common and bothersome side effect. The second section addresses the controversial but effective use of cannabinoids for cancer and chemotherapy symptoms. Although clinical trials are difficult to conduct because of the political and social stigma of this class of drugs, this review provides evidence of the efficacy of cannabinoids for treatment of pain and nausea. The last section addresses the mind-body connection, with a focus on the negative emotions patients with cancer often experience. This section assesses the literature regarding mindfulness-based programs to improve cancer-related stress. These three topics may appear unrelated, but all address one common goal: treating the body and the mind to optimize quality of life during and after cancer therapy.

Perspectives on the opioid crisis from pain medicine clinicians

Patients experiencing a terminal drug related event reflect a sentinel event. If this pharmacotherapy is a widely used agent, it may be viewed as a catastrophic problem. If patients are dying from illegal drug use when the medical establishment fails them by withdrawing or minimizing their medically prescribed medication, then the burden rests with their health care providers, legislation, and insurance carriers to actively participate in a collegial fashion to achieve parity. Causing a decay in functionality in previously functional patients, may occur with appropriately prescribed opioid medications addressing non-cancer pain when withdrawing or diminishing either with or without patient consent. The members of the medical profession have diminished their prescribing of opioids for their patients out of apparent fear of reprisal, state or federal government sanctions, and other concerned groups. Diminishing former dosages or deleting the opioid medication, preferably in concert with the patient, often results in inequitable patient care. Enforcing sanctioned decreases or ceasing to prescribe from their former required/established opioid medications precipitate patient discord. In absence of opioid misuse, abuse, diversion or addiction based upon medical "guidelines" and with a poor foundation of Evidence Based Medicine the CDC guidelines, it may be masked as a true guideline reflecting a decrement of clinical judgment, wisdom, and compassion. This article also discusses the role of pharmacy chains, insurance carriers, and their pharmacy benefit managers (PBMs) contribution to this multidimensional problem. There may be a potential solution, identified in this paper, if all the associated political, medical and insurance groups work cohesively to improve patient care. This article and the CDC guidelines are not focused at hospice, palliative, end of life care pain management.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Opioids combined with antidepressants or antiepileptic drugs for cancer pain: Systematic review and meta-analysis

BACKGROUND

Combining antidepressant or antiepileptic drugs with opioids has resulted in increased pain relief when used for neuropathic pain in non-cancer conditions. However, evidence to support their effectiveness in cancer pain is lacking.

AIM

To determine if there is additional benefit when opioids are combined with antidepressant or antiepileptic drugs for cancer pain.

DESIGN

Systematic review and meta-analysis. Randomised control trials comparing opioid analgesia in combination with antidepressant or antiepileptic drugs versus opioid monotherapy were sought. Data on pain and adverse events were extracted. Data were pooled using DerSimonian-Laird random-effects meta-analyses, and heterogeneity was assessed.

RESULTS

Seven randomised controlled trials that randomised 605 patients were included in the review. Patients' pain was described as neuropathic cancer pain, cancer bone pain and non-specific cancer pain. Four randomised controlled trials were included in the meta-analysis in which opioid in combination with either gabapentin or pregabalin was compared with opioid monotherapy. The pooled standardised mean difference was 0.16 (95% confidence interval, -0.19, 0.51) showing no significant difference in pain relief between the groups. Adverse events were more frequent in the combination arms. Data on amitriptyline, fluvoxamine and phenytoin were inconclusive.

CONCLUSION

Combining opioid analgesia with gabapentinoids did not significantly improve pain relief in patients with tumour-related cancer pain compared with opioid monotherapy. Due to the heterogeneity of patient samples, benefit in patients with definite neuropathic cancer pain cannot be excluded. Clinicians should balance the small likelihood of benefit in patients with tumour-related cancer pain against the increased risk of adverse effects of combination therapy.

Neuropathic Corneal Pain: Approaches for Management

Neuropathic pain is caused by a primary lesion or dysfunction of the nervous system and can occur in the cornea. However, neuropathic corneal pain (NCP) is currently an ill-defined disease. Patients with NCP are extremely challenging to manage, and evidence-based clinical recommendations for the management of patients with NCP are scarce. The objectives of this review are to provide guidelines for diagnosis and treatment of patients with NCP and to summarize current evidence-based literature in this area. We performed a systematic literature search of all relevant publications between 1966 and 2017. Treatment recommendations are, in part, based on methodologically sound randomized controlled trials (RCTs), demonstrating superiority to placebo or relevant control treatments, and on the consistency of evidence, degree of efficacy, and safety. In addition, the recommendations include our own extensive experience in the management of these patients over the past decade. A comprehensive algorithm, based on clinical evaluation and complementary tests, is presented for diagnosis and subcategorization of patients with NCP. Recommended first-line topical treatments include neuroregenerative and anti-inflammatory agents, and first-line systemic pharmacotherapy includes tricyclic antidepressants and an anticonvulsant. Second-line oral treatments recommended include an opioid-antagonist and opiate analgesics. Complementary and alternative treatments, such as cardiovascular exercise, acupuncture, omega-3 fatty acid supplementation, and gluten-free diet, may have additional benefits, as do potential noninvasive and invasive procedures in recalcitrant cases. Medication selection should be tailored on an individual basis, considering side effects, comorbidities, and levels of peripheral and centralized pain. Nevertheless, there is an urgent need for long-term studies and RCTs assessing the efficacy of treatments for NCP.