Transdermal Buprenorphine Relieves Neuropathic Pain: A Randomized, Double-Blind, Parallel-Group, Placebo-Controlled Trial in Diabetic Peripheral Neuropathic Pain

Methadone and Buprenorphine in the Perioperative Setting: A Review of the Literature

PURPOSE OF REVIEW

The purpose of this review is to highlight the most recent literature and guidelines regarding perioperative methadone and buprenorphine use.

RECENT FINDINGS

Surgical patients taking methadone and buprenorphine are being encountered more frequently in the perioperative period, and providers are becoming more familiar with their pharmacologic properties, benefits as well as precautions. Recommendations pertaining to buprenorphine therapy in the perioperative settings have changed in recent years, owing to more clinical and basic science research. In addition to their use in chronic pain and opioid use disorders, they can also be initiated for acute postoperative pain indications, in select patients and situations. Methadone and buprenorphine are being more commonly prescribed for pain management and opioid use disorder, and their continuation during the perioperative period is generally recommended, to reduce the risk of opioid withdrawal, relapse, or inadequately controlled pain. Additionally, both may be initiated safely and effectively for acute pain management during and after the operating room period.

A Brief Review on the Novel Therapies for Painful Diabetic Neuropathy

PURPOSE OF REVIEW

Almost half of people diagnosed with diabetes mellitus will develop painful diabetic neuropathy (PDN), a condition greatly impacting quality of life with complicated pathology. While there are different FDA approved forms of treatment, many of the existing options are difficult to manage with comorbities and are associated with unwanted side effects. Here, we summarize the current and novel treatments for PDN.

RECENT FINDINGS

Current research is exploring alternative pain management treatments from the first line options of pregabalin, gabapentin, duloxetine, and amitriptyline which often have side effects. The use of FDA approved capsaicin and spinal cord stimulators (SCS) has been incredibly beneficial in addressing this. In addition, new treatments looking at different targets, such as NMDA receptor and the endocannabinoid system, show promising results. There are several treatment options that have been shown to be successful in helping treat PDN, but often require adjunct treatment or alterations due to side effects. While there is ample research for standard medications, treatments such as palmitoylethanolamide and endocannabinoid targets have extremely limited clinical trials. We also found that many studies did not evaluate additional variables other than pain relief, such as functional changes nor were there consistent measurement methods. Future research should continue trials comparing treatment efficacies along with more quality of life measures.

Analgesic Effect of Buprenorphine for Chronic Noncancer Pain: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Buprenorphine is a partial agonist at the µ-opioid receptor and an antagonist at the delta and kappa opioid receptors. It has high affinity and low intrinsic activity at the µ-opioid receptor. Buprenorphine demonstrates no ceiling effect for clinical analgesia, but demonstrates this for respiratory depression and euphoria. It may provide effective analgesia while producing less adverse effects, making it a promising opioid analgesic. A systematic review and meta-analysis were performed to examine the analgesic efficacy of buprenorphine for patients with chronic noncancer pain.

METHODS

PubMed, MEDLNE, Embase, and the Cochrane Library were searched up to January 2022. Randomized controlled trials were included if they compared buprenorphine versus placebo or active analgesic in patients with chronic noncancer pain, where pain score was an outcome. Nonrandomized controlled trials, observational studies, qualitative studies, case reports, and commentaries were excluded. Two investigators independently performed the literature search, study selection, and data collection. A random-effects model was used. The primary outcome was the effect of buprenorphine on pain intensity in patients with chronic noncancer pain based on standardized mean difference (SMD) in pain score. Quality of evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Two separate literature searches were conducted for patients with and without opioid use disorder (OUD). Only one study met the search criteria for those with OUD. Fourteen randomized controlled trials were included for those without OUD. Buprenorphine was associated with reduced pain score (SMD = -0.368, P < .001, I 2 = 89.37%) compared to placebo or active analgesic. Subgroup meta-analyses showed statistically significant differences in favor of buprenorphine versus placebo (SMD = -0.404, P < .001), for chronic low back pain (SMD = -0.383, P < .001), when administered via the transdermal route (SMD = -0.572, P = .001), via the buccal route (SMD = -0.453, P < .001), with length of follow-up lasting <12 weeks (SMD = -0.848, P < .05), and length of follow-up lasting 12 weeks or more (SMD = -0.415, P < .001). There was no significant difference when compared to active analgesic (SMD = 0.045, P > .05). Quality of evidence was low to moderate.

CONCLUSIONS

Buprenorphine was associated with a statistically significant and small reduction in pain intensity compared to placebo. Both the transdermal and buccal routes provided pain relief. There was more evidence supporting its use for chronic low back pain.

Comparative benefits and harms of individual opioids for chronic non-cancer pain: a systematic review and network meta-analysis of randomised trials

BACKGROUND

Most systematic reviews of opioids for chronic pain have pooled treatment effects across individual opioids under the assumption they provide similar benefits and harms. We examined the comparative effects of individual opioids for chronic non-cancer pain through a network meta-analysis of randomised controlled trials.

METHODS

We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Central Register of Controlled Trials to March 2021 for studies that enrolled patients with chronic non-cancer pain, randomised them to receive different opioids, or opioids vs placebo, and followed them for at least 4 weeks. Certainty of evidence was evaluated using the GRADE approach.

RESULTS

We identified 82 eligible trials (22 619 participants) that evaluated 14 opioids. Compared with placebo, several opioids showed superiority to others for analgesia and improvement in physical function; however, when restricted to pooled-effect estimates supported by moderate certainty evidence, no differences between opioids were evident. Among opioids with moderate certainty evidence, all increased the risk of gastrointestinal adverse events compared with placebo, although no opioids were more harmful than others. Low to very low certainty evidence suggests that extended-release vs immediate-release opioids may provide similar benefits for pain relief and physical functioning, and gastrointestinal harms.

CONCLUSIONS

Our findings support the pooling of effect estimates across different types and formulations of opioids to inform effectiveness for chronic non-cancer pain.

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.

Different Drugs for the Treatment of Painful Diabetic Peripheral Neuropathy: A Meta-Analysis

Objective: To systematically evaluate the effects of different drugs for the treatment of painful diabetic peripheral neuropathy.

Methods: All literature from PubMed, Embase, and Cochrane Central Register of Controlled Trials published over the past 12 years (from January 1, 2008 to June 1, 2020) was searched, and two reviewers independently assessed study eligibility, continuous data extraction, independent assessment of bias risk, and graded strength of evidence. The pain score was used as the main result, and 30 and 50% pain reduction and adverse events were used as secondary results.

Results: A total of 37 studies were included. Pregabalin, duloxetine, tapentadol, lacosamide, mirogabalin, and capsaicin were all more effective than placebo in alleviating the pain associated with diabetic peripheral neuropathy, while ABT-894 and gabapentin showed no significant effect. In addition, the efficacy of buprenorphine, tanezumab, fulranumab and others could not be concluded due to insufficient studies.

Conclusion: Pregabalin and duloxetine showed good therapeutic effects on painful DPN, but adverse events were also significant. The analgesic effects of ABT-894 and gabapentin need to be further studied with longer and larger RCTs. As an opioid drug, tapentadol has a good analgesic effect, but due to its addiction, it needs to be very cautious in clinical use. Although lacosamide, mirogabalin, and capsaicin are more effective than placebo, the therapeutic effect is weaker than pregabalin. For the results of our meta-analysis, long-term studies are still needed to verify their efficacy and safety in the future.

Systematic Review Registration: PROSPERO, identifier: CRD42020197397.

Buprenorphine for Chronic Pain: A Safer Alternative to Traditional Opioids

With the ongoing public health crisis with prescription opioids, there is a need for safer alternatives for medication management in chronic pain patients. Buprenorphine is a partial mu-opioid agonist which is commonly utilized to treat patients with opioid-use disorders. The purpose of this review is to discuss the potential use of this medication for the treatment of chronic pain instead of resorting to more traditional Schedule II opioids. Buprenorphine offers a safer alternative for patients who require opioids to manage chronic pain, given the unique pharmacological properties that allow it to provide adequate analgesia with less abuse potential.

An Italian Expert Consensus on the Use of Opioids for the Management of Chronic Non-Oncological Pain in Clinical Practice: Focus on Buprenorphine

Purpose

The aim of the present work was to evaluate the knowledge and prescriptive habits of clinicians involved in the management of chronic non cancer pain (CNCP), with a special focus on the use of opioids.

Methods

A Delphi method was used. A Board of specialists elaborated and discussed a series of statements, based on available literature and personal clinical expertise, about particularly controversial topics on pain pathophysiology and treatment. A Panel of experts in the field of pain management, selected by the Board, was invited to vote the proposed statements, indicating the level of agreement on a 5-point Likert scale (1: strongly disagree; 2: disagree; 3: partially agree; 4: agree; 5: strongly agree). The threshold for consensus was set at minimum 66.6% of the number of respondents with a level of agreement ≥4 (Agree or Strongly agree).

Results

The Board included 5 pain therapists, 1 pharmacologist and 1 methodology expert and drew up a total of 36 statements (for a total of 40 requested answers)”. A total of 100 clinicians were included in the Expert Panel. Respondents were 89 (89%). Consensus was achieved for 32 out of 40 answers. Most of the lack of consensus was recorded for statements regarding opioids use, and resulted from a low level of agreement (3 on the Likert scale), suggesting a neutral position deriving from a lack of knowledge rather than a strong contrary opinion.

Conclusion

Most of the proposed items reached consensus, suggesting a generally homogeneous approach to CNCP management. However, the lack of consensus recorded for several items regarding opioid use confirms the need to fill important gaps in the knowledge of available agents. A clear explanation of the peculiar pharmacological properties of drugs associated with potential clinical advantages (such as buprenorphine) will help optimize pain treatment in both primary care and hospital settings and improving pain control in CNCP patients.

A practical review of buprenorphine utilization for the emergency physician in the era of decreased prescribing restrictions

INTRODUCTION

Opioid abuse and overdose deaths have reached epidemic proportions in the last couple decades. In response to rational prescribing initiatives, utilization of prescription opioids has decreased; however, the number of deaths due to opioid overdoses continues to rise, largely driven by fentanyl analogues in adulterated heroin. Solutions to the opioid crisis must be multifaceted and address underlying opioid addiction. In recent years, buprenorphine has become a cornerstone in the treatment of opioid use disorder (OUD) and initiation of therapy in the emergency department (ED) has become increasingly common. There have also been calls by many organizations to remove the requirement for additional training and X-waiver to prescribe buprenorphine. In April 2021, the Biden Administration eased prescribing restrictions on the drug. These initiatives are expected to increase ED utilization of the buprenorphine. The purpose of this paper is to provide an updated overview of the role and use of buprenorphine in the ED setting so physicians may adapt to the changing practice environment.

OBJECTIVES

This is a narrative review describing the role of buprenorphine in the ED. A PubMed search was conducted using the keywords "opioid epidemic" "buprenorphine," and "medication assisted therapy", and "emergency department". All the articles that contained information on the opioid epidemic, medication assisted therapy, and the biological effects of buprenorphine, that were also relevant to pain management and the ED, were included in the review.

DISCUSSION

Multiple studies have pointed to the effective use of buprenorphine as a treatment for OUDs in ED patients and are superior to standard care; however, there are various barriers to its use in the ED setting.

CONCLUSION

Emergency physicians can influence opioid related morbidity and mortality, by familiarizing themselves with the use of buprenorphine to treat opioid withdrawal and addiction, particularly now that prescribing restrictions have been eased. Further ED research is necessary to assess the optimal use of buprenorphine in this care setting.

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.

Tapentadol, Buprenorphine, and Levorphanol for the Treatment of Neuropathic Pain: a Systematic Review

PURPOSE OF REVIEW

The objective of this systematic review is to present the available evidence for the utilization of the atypical opioids tapentadol, buprenorphine, and levorphanol for the treatment of neuropathic pain.

RECENT FINDINGS

In total, 1619 articles were retrieved of which 10 studies were included. Of 5 included studies pertaining to tapentadol, 4 studies show tapentadol monotherapy to be effective for the treatment of diabetic peripheral neuropathy or chronic, radiating low back pain. Of the 3 studies included for buprenorphine, only one was a randomized controlled trial found not to have a statistically significant reduction in pain with TD buprenorphine likely due to very high withdrawal rates during the trial. Only 2 case reports were included from the available literature for levorphanol providing low-quality anecdotal evidence. The role of tapentadol, buprenorphine, and levorphanol for neuropathic pain conditions requires robust research including randomized controlled trials to evaluate their efficacy and safety.

The Safety of Medications used to Treat Peripheral Neuropathic Pain, Part 2 (Opioids, Cannabinoids and Other Drugs): review of Double-Blind, Placebo-Controlled, Randomized Clinical Trials

INTRODUCTION

Peripheral neuropathic pain is a disabling condition for patients and a challenge for physicians. Although many drugs have been assessed in scientific studies, few have demonstrated clear clinical efficacy against neuropathic pain. Moreover, the paucity of data regarding their safety raises the question of the benefit-risk ratio when used in patients experiencing peripheral neuropathies.

AREAS COVERED

We conducted a review of double-blind, placebo-controlled, randomized clinical trials to assess the safety of medications used to treat peripheral neuropathic pain. This second review was focused on opioids, cannabinoids, and other medications. The aim was to provide an overview of the treatment-emergent adverse events (TEAEs) (≥10%) and the serious adverse effects described in clinical trials.

EXPERT OPINION

Opioids and cannabinoids had significantly more TEAEs than placebos. Locally administered analgesics, such as capsaicin, lidocaine, botulinum toxin A seemed to have the most acceptable safety with only local adverse effects. The results for NMDA antagonists were inconclusive since no safety report was available. Less than half of the studies included presented a good description of TEAEs that included a statistical comparison versus a placebo group. Major methodological improvements must be made to ameliorate the assessment of medication safety in future clinical trials.

Participation of the opioid receptor - nitric oxide - cGMP - K+ channel pathway in the peripheral antinociceptive effect of nalbuphine and buprenorphine in rats

The aim of this study was to examine if the peripheral antinociceptive effects of the opioid agonist/antagonist nalbuphine and buprenorphine involve the sequential participation of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) synthesis followed by K⁺ channel opening in the formalin test. Wistar rats (180-220 g) were injected in the dorsal surface of the right hind paw with formalin (1%). Rats received a subcutaneous (s.c.) injection into the dorsal surface of the paw of vehicles or increasing doses of nalbuphine (50-200 μg/paw) or buprenorphine (1-5 μg/paw) 20 min before formalin injection into the paw. Nalbuphine antinociception was reversed by the s.c. injection into the paw of the inhibitor of NO synthesis (N^G-nitro-l-arginine methyl ester (L-NAME)), by the inhibitor of guanylyl cyclase (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ)), by the K_ir6.1-2, ATP-sensitive K⁺ channel inhibitors (glibenclamide and glipizide), by the K_Ca2.1-3, small conductance Ca²⁺-activated K⁺ channel blocker (apamin), by the K_Ca1.1, large conductance Ca²⁺-activated K⁺ channel blocker (charybdotoxin), and by the K_V, voltage-dependent K⁺ channel inhibitors (4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA)). The antinociceptive effect produced by buprenorphine was blocked by the s.c. injection of 4-AP and TEA but not by L-NAME, ODQ, glibenclamide, glipizide, apamin, or charybdotoxin. The present results provide evidence for differences in peripheral mechanisms of action between these opioid drugs.

The utilization of buprenorphine in chronic pain

Reclassification of chronic pain as a disease may be helpful because patients with chronic pain require significant treatment and rehabilitation with a clear diagnosis. This can help address critical factors including suffering, quality of life, participation, and with family and social life, which continue to become more important in evaluating the quality of the health care we give our patients today. During the past decade of the opioid epidemic, methadone was the primary treatment for opioid addiction until buprenorphine was approved. Buprenorphine's high-affinity partial agonist properties make it a good alternative to methadone due to lower abuse potential and safer adverse effect profile while maintaining significant efficacy. Expanded out-patient prescribing options have allowed physician and physician extenders such as physician assistants and nurse practitioners to treat these patients that otherwise would have been required to utilize methadone. With unique pharmacological properties, buprenorphine is a safe and effective analgesic for chronic pain. The literature for buprenorphine shows great potential for its utilization in the treatment of chronic pain.

Limited Access to On-Label Formulations of Buprenorphine for Chronic Pain as Compared with Conventional Opioids

IMPORTANCE

Buprenorphine is a Schedule III analgesic that is recommended as the firstline long-acting opioid for the treatment of chronic pain due to its ceiling effect on respiratory depression, adverse effect profile, and analgesic efficacy. However, prescription drug coverage policies commonly require that patients try and fail multiple Schedule II conventional opioids before approval of on-label use of buprenorphine for chronic pain.

DESIGN

A retrospective review was performed looking at coverage of buprenorphine in the forms of Butrans and Belbuca. Patient denial letters, web searches of insurance and pharmacy benefit managers (PBMs), and an online tool (formularylookup.com) were used to assess the coverage and availability of buprenorphine for chronic pain.

RESULTS

Unrestricted access to Butrans was reported for 42% of commercial lives and 11% of Medicare lives in all locations. Unrestricted access to Belbuca was reported for 53% of commercial lives and 23% of Medicare lives in all locations. Oxycodone immediate-release has unrestricted access for 84% of commercial plans and 97% of Medicare plans. Morphine extended-release has unrestricted access for 62% of commercial lives and 65% of Medicare lives.

CONCLUSIONS AND RELEVANCE

There are >17,000 prescription opioid-involved deaths each year in the United States. By substituting buprenorphine as the firstline treatment for chronic and even acute pain, there may be fewer prescribed conventional opioids in the United States. Schedule III buprenorphine formulations for chronic pain should be given unrestricted access for appropriate patients before considering a Schedule II opioid as a public health priority.

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.

Pragmatic Opioid Use in Painful Diabetic Neuropathy

The management of painful diabetic neuropathy poses a tough clinical challenge. Although opioid analgesics are considered as second- or third-line agents in the management of moderate-to-severe neuropathic pain, prescription of opioids for this indication is higher than expected. This narrative review is a recommendation on how to ensure pragmatic use of opioids for those with painful diabetic neuropathy while avoiding complications such as opioid overdose, opioid diversion and the development of opioid-use disorder. Risk mitigation strategies at the level of the clinician include periodic assessment and documentation of clinical details, treatment history and psychosocial status. Using a multimodal approach to pain management, medication counselling, adherence monitoring programmes, evidence-based opioid dosing strategies and empowering patients to make treatment decisions are effective strategies in reducing risk associated with prolonged opioid use. At the organisational and policy level, using prescription drug monitoring programmes, carrying out periodic opioid utilisation reviews and providing training to patients and physicians on safe opioid use are useful, implementable strategies.

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.

Transdermal buprenorphine for moderate chronic noncancer pain syndromes

Introduction: Chronic noncancer pain has remained a challenging clinical problem. Opioid analgesics are effective, but they are known to be associated with opioid use disorder and potentially treatment-limiting side effects. Buprenorphine is a Schedule III synthetic opioid in the USA with a chemical structure similar to that of morphine but with a longer duration of action, greater potency, and other unique pharmacological attributes. Its role in treatment of chronic noncancer pain may be broader than currently thought.Areas covered: The pharmacokinetics, pharmacodynamics, clinical efficacy, and safety profile of transdermal buprenorphine in moderate chronic noncancer pain syndromes patients will be discussed.Expert commentary: Buprenorphine offers effective analgesia in the form of a Schedule III drug (rather than Schedule II such as oxycodone or morphine) and transdermal buprenorphine is a convenient, accepted, around-the-clock pain reliever. Its lower potential for abuse should make it a more desirable pain reliever but many payers do not reimburse buprenorphine, driving prescribers and their patients to generic versions of the riskier Schedule II oral opioids such as oxycodone and morphine.

Cancer-Related Neuropathic Pain: Review and Selective Topics

Neuropathic pain is the result of neuroplastic and neuroinflammatory changes from trauma or diseases that damage the somatosensory system. Cancer-related neuropathic pain is caused by treatment, cancer, or paraneoplastic reactions to cancer. Approximately 30% of patients with cancer have neuropathic pain, mostly mixed nociceptive and neuropathic pain. History, physical examination, quantitative sensory testing, skin punch biopsies, and functional MRIs help to divide pain into phenotypes that may facilitate analgesic choices. Guidelines for treating cancer-related neuropathic pain are not consistent and are highly dependent on trials in patients without cancer. Combinations of analgesics are promising, whereas evidence for cannabinoids is meager.