Gabapentin dosing for neuropathic pain: evidence from randomized, placebo-controlled clinical trials

6-Methoxyflavone antagonizes chronic constriction injury and diabetes associated neuropathic nociception expression

Neuropathy is a disturbance of function or a pathological change in nerves causing poor health and quality of life. A proportion of chronic pain patients in the community suffer persistent neuropathic pain symptoms because current drug therapies may be suboptimal so there is a need for new therapeutic modalities. This study investigated the neuroprotective flavonoid, 6-methoxyflavone (6MF), as a potential therapeutic agent and gabapentin as the standard comparator, against neuropathic models. Thus, neuropathic-like states were induced in Sprague-Dawley rats using sciatic nerve chronic constriction injury (CCI) mononeuropathy and systemic administration of streptozotocin (STZ) to induce polyneuropathy. Subsequent behaviors reflecting allodynia, hyperalgesia, and vulvodynia were assessed and any possible motoric side-effects were evaluated including locomotor activity, as well as rotarod discoordination and gait disruption. 6MF (25-75 mg/kg) antagonized neuropathic-like nociceptive behaviors including static- (pressure) and dynamic- (light brushing) hindpaw allodynia plus heat/cold and pressure hyperalgesia in the CCI and STZ models. 6MF also reduced static and dynamic components of vulvodynia in the STZ induced polyneuropathy model. Additionally, 6MF reversed CCI and STZ suppression of locomotor activity and rotarod discoordination, suggesting a beneficial activity on motor side effects, in contrast to gabapentin. Hence, 6MF possesses anti-neuropathic-like activity not only against different nociceptive modalities but also impairment of motoric side effects.

Probable chronic pain, brain structure, and Alzheimer's plasma biomarkers in older men

Chronic pain leads to tau accumulation and hippocampal atrophy in mice. In this study, we provide one of the first assessments in humans, examining the associations of probable chronic pain with hippocampal volume, integrity of the locus coeruleus (LC)-an upstream site of tau deposition-and Alzheimer's Disease-related plasma biomarkers. Participants were mostly cognitively unimpaired men. Probable chronic pain was defined as moderate-to-severe pain in 2+ study waves at average ages 56, 62, and 68. At age 68, 424 participants underwent structural magnestic resonance imaging (MRI) of hippocampal volume and LC-sensitive MRI providing an index of LC integrity (LC contrast-to-noise ratio). Analyses adjusted for confounders including major health conditions, depressive symptoms, and opioid use. Models showed that men with probable chronic pain had smaller hippocampal volume and lower rostral-middle-but not caudal-LC contrast-to-noise ratio compared to men without probable chronic pain. Men with probable chronic pain also had higher levels of plasma total tau, beta-amyloid-42, and beta-amyloid-40 compared to men without probable chronic pain. These findings suggest that probable chronic pain is associated with tau accumulation and reduced structural brain integrity in regions affected early in the development of Alzheimer's Disease. PERSPECTIVE: Probable chronic pain was associated with plasma biomarkers and brain regions that are affected early in Alzheimer's disease (AD). Reducing pain in midlife and elucidating biological mechanisms may help to reduce the risk of AD in older adults.

Gabapentinoid prescriptions for neuropathic and musculoskeletal pain in Lebanon

Aim: The purpose of this study is to analyze the different characteristics of gabapentinoids prescription by Lebanese orthopedics surgeons. Methods: This is an observational, cross-sectional study using a survey which was carried out in collaboration with the Lebanese Orthopedic Society over a 3-month period. Results: Forty-two orthopedic surgeons responded, most of them prescribing gabapentinoids in their daily practice with only half of the patients feeling relief after taking them. Furthermore, most of the surgeons prescribed these drugs for patients above 18 years old and for both acute and chronic pain. Conclusion: Even though almost half of the patients do not experience relief after taking gabapentinoids, these drugs are becoming more and more prescribed.

Role of Palliative Care in the Supportive Management of AL Amyloidosis-A Review

Light chain amyloidosis is a plasma-cell disorder with a poor prognosis. It is a progressive condition, causing worsening pain, disability, and life-limiting complications involving multiple organ systems. The medical regimen can be complex, including chemotherapy or immunotherapy for the disease itself, as well as treatment for pain, gastrointestinal and cardiorespiratory symptoms, and various secondary symptoms. Patients and their families must have a realistic awareness of the illness and of the goals and limitations of treatments in making informed decisions about medical therapy, supportive management, and end-of-life planning. Palliative care services can thus improve patients' quality of life and may even reduce overall treatment costs. Light chain (AL) amyloidosis is a clonal plasma cell disorder characterized by the excessive secretion of light chains by an indolent plasma cell clone that gradually accumulates in vital organs as amyloid fibrils and leads to end-organ damage. With progressive disease, most patients develop diverse clinical symptoms and complications that negatively impact quality of life and increase mortality. Complications include cardiac problems including heart failure, hypotension, pleural effusions, renal involvement including nephrotic syndrome with peripheral edema, gastrointestinal symptoms leading to anorexia and cachexia, complex pain syndromes, and mood disorders. The prognosis of patients with advanced AL amyloidosis is dismal. With such a complex presentation, and high morbidity and mortality rates, there is a critical need for the establishment of a palliative care program in clinical management. This paper provides an evidence-based overview of the integration of palliative care in the clinical management of AL amyloidosis as a means of reducing ER visits, rehospitalizations, and in-hospital mortality. We also discuss potential future collaborative directions in various aspects of clinical care related to AL amyloidosis.

Gabapentin improves neuropathic pain in Minamata disease model rats

BACKGROUND

Methylmercury (MeHg), the causative agent of Minamata disease, damages the cranial nervous system and causes specific sensory disturbances, especially hypoesthesia, in the extremities. However, recent reports demonstrate that patients with chronic Minamata disease conversely develop neuropathic pain in the lower extremities. Studies on our established Minamata disease model rats showed that MeHg-mediated neurodegeneration might induce neuropathic pain by over time through inducing rewiring with neuronal activation in the somatosensory cortex via microglial activation in the spinal dorsal horn.

METHODS

In this study, the effects of gabapentin, a potentially effective treatment for neuropathic pain, was evaluated using this Minamata disease model rats. To further elucidate the mechanism of its medicinal effects, histochemical and biochemical analyses of the nervous system of Minamata disease model rats were conducted.

RESULTS

Gabapentin treatment restored the reduction in the pain threshold caused by MeHg exposure in rats. Histochemical and biochemical analyses revealed that gabapentin showed no effect on MeHg-induced neurodegeneration in entire nervous system and microglial activation in the spinal dorsal horn. However, it was shown that gabapentin may reduce excessive synaptogenesis through its antagonist action on the alpha2-delta-1 subunit of calcium channels in the somatosensory cortex.

CONCLUSIONS

These results indicate that gabapentin may alleviated neuropathic pain in MeHg poisoning, as typified by Minamata disease, by reversibly modulation synaptic rewiring in the somatosensory cortex.

Analyzing the Antinociceptive Effect of Interleukin-31 in Mice

The theory that an itch inhibits pain has been refuted; however, previous research did not investigate this theory for an interleukin-31 (IL-31)-induced itch. Previously, we have found that morphine-induced antinociception was partially reduced in IL-31 receptor A (IL-31RA)-deficient (IL-31RAKI) mice, indicating that IL-31RA may play an important role in morphine-induced peripheral antinociception. In the present study, we evaluated the effect of IL-31-induced analgesia on a 2,4,6-trinitrochlorobenzene (TNCB)-sensitized mice using a hot-plate test. This test evaluated the antinociceptive activity of morphine and non-steroidal anti-inflammatory drugs (NSAIDs). Repeated pretreatment with IL-31 showed significant antinociceptive action. Furthermore, its combination with morphine, but not with NSAIDs, increased the analgesic action. In contrast, treatment with TNCB and capsaicin decreased antinociception. Moreover, TNCB increased IL-31RA expression in the dorsal root ganglia at 24 h, whereas capsaicin inhibited it. The comparative action of several analgesics on TNCB or capsaicin was evaluated using a hot-plate test, which revealed that the antinociceptive activity was decreased or disappeared in response to capsaicin-induced pain in IL-31RAKI mice. These results indicate that the analgesic action of IL-31 involves the peripheral nervous system, which affects sensory nerves. These results provide a basis for developing novel analgesics using this mechanism.

Characterization of Outpatient Gabapentinoid Prescribing for Pain

Two statements from national organizations outline recommended minimum effective doses of gabapentin and pregabalin for the treatment of diabetic peripheral neuropathy (DPN). However, studies of real-world gabapentinoid dosing demonstrate that the recommended dose targets are frequently not met and do not consider renal insufficiency. This study aimed to characterize gabapentinoid prescribing patterns in patients receiving primary care at two internal medicine clinics within an academic medical center. This retrospective chart review included adult outpatients who were newly initiated on gabapentin or pregabalin between October 1, 2017 and October 1, 2020 and reviewed for 12 months. A total of 1,221 patients were included in the study with 1,079 (88.4%) prescribed gabapentin and 142 (11.6%) prescribed pregabalin. Only 22.4% of patients prescribed gabapentin and 33.3% of patients prescribed pregabalin with adequate renal function met the minimum effective dosing of gabapentin 1800 mg per day and pregabalin 300 mg per day provided by the American Diabetes Association (ADA) and American Academy of Neurology (AAN). This study supports the need for optimization of gabapentinoid dosing to ensure an adequate trial at the minimum effective dose is completed.

Mechanisms of Transmission and Processing of Pain: A Narrative Review

Knowledge about the mechanisms of transmission and the processing of nociceptive information, both in healthy and pathological states, has greatly expanded in recent years. This rapid progress is due to a multidisciplinary approach involving the simultaneous use of different branches of study, such as systems neurobiology, behavioral analysis, genetics, and cell and molecular techniques. This narrative review aims to clarify the mechanisms of transmission and the processing of pain while also taking into account the characteristics and properties of nociceptors and how the immune system influences pain perception. Moreover, several important aspects of this crucial theme of human life will be discussed. Nociceptor neurons and the immune system play a key role in pain and inflammation. The interactions between the immune system and nociceptors occur within peripheral sites of injury and the central nervous system. The modulation of nociceptor activity or chemical mediators may provide promising novel approaches to the treatment of pain and chronic inflammatory disease. The sensory nervous system is fundamental in the modulation of the host's protective response, and understanding its interactions is pivotal in the process of revealing new strategies for the treatment of pain.

Gabapentinoids for Pain: A Review of Published Comparative Effectiveness Trials and Data Submitted to the FDA for Approval

Use of the gabapentinoids for pain continues to increase. In 2018, the US Food and Drug Administration (FDA) strengthened the warnings for both gabapentin and pregabalin to emphasize the central nervous system side effects and the risk of respiratory depression, especially when combined with other centrally acting drugs. We reviewed the published comparative effectiveness literature for gabapentinoids for pain as well as all trials (published and unpublished) used by the FDA for the approval of the five pain indications for these agents (one for gabapentin, four for pregabalin). Among the findings of interest are the fact that the FDA rejected the application for gabapentin for diabetic peripheral neuropathy based on the risk versus benefit profile of that drug in the clinical trials that were submitted by the manufacturer. Additionally, both the comparative effectiveness trials as well as the studies used by the FDA tend to be short in duration and show only modest pain benefits for the gabapentinoids. The placebo response in these trials was frequently one-third to one-half as great as the pain benefit demonstrated by the gabapentinoid. Based on the available clinical trial evidence, we feel prescribers should be cautious when using gabapentinoids for pain, particularly when using these agents for a prolonged period or when combined with other, centrally acting agents.

Comparison of the Efficacy and Safety of Duloxetine and Gabapentin in Diabetic Peripheral Neuropathic Pain: A Meta-Analysis

Background

Diabetic peripheral neuropathic pain (DPNP) is a common chronic pain condition affecting diabetic patients and has growing importance because of the increasing prevalence of patients with type 2 diabetes mellitus. Pain is the most troublesome symptom of DPNP, increasingly recognized as an important and independent feature of DPNP. This meta-analysis aims to compare the efficacy and safety of duloxetine and gabapentin in the treatment of diabetic peripheral neuropathic pain (DPNP) and therefore to provide evidence-based medicine for clinical treatment.

Methods

Relevant randomized controlled trials on duloxetine versus gabapentin for DPNP were searched from PubMed, Embase, Cochrane Library, Web of Science, CNKI, WanFang, VIP, and Chinese Biomedical Literature Database from database inception to October 2021. The data were analyzed by RevMan 5.3 software.

Results

Seven studies were included. The results showed that, at the end of the study, duloxetine was significantly superior to gabapentin in terms of the incidence of adverse reactions (RR = 0.59, 95% CI: 0.45–0.79, P < 0.01), sleep interference score (SMD = −0.35, 95% CI: −0.63 to −0.08, P < 0.05), but no significant differences in VAS score (SMD = −0.14, 95% CI: −0.31–0.03, P > 0.05), overall response rate (RR = 1.05, 95% CI: 0.92–1.20, P > 0.05), and clinical global impression of change (SMD = 0.07, 95% CI: −0.20–0.35, P > 0.05).

Conclusion

Compared with gabapentin, duloxetine has no obvious advantage in the treatment of diabetic peripheral neuralgia, but it has less side effects and significantly higher safety.

Therapeutic interventions to urologic chronic pelvic pain syndrome and UPOINT system for clinical phenotyping: How far are we?

The assessment and management of urologic chronic pelvic pain syndrome (UCPPS), is controversial. It is classified by voiding symptoms, pelvic pain, and bladder pain, which is weekly treated, weekly understood, and bothersome. In the aspect of clinical efforts and research to help people with this syndrome have been hampered by the deficiency of a widely reliable, accepted, and a valuable tool to evaluate the patient symptoms and quality of life (QoL) impact. However, the etiology comes into sight is multifactorial, and available treatment options have been imprecise considerably in present years. We compiled the published literature on the assessment of the syndrome, a tentative role of pharmacological and non-pharmacological (conservative, alternative, and invasive therapy) interventions in eradicating the disease as well as improving symptoms. The previously published literature on animal models has established the association of immune systems in the etiology, pathogenesis, and progression of the disease. The UPOINT system for clinical phenotyping of UCPPS patients has six predefined domains that direct multimodal therapy, which would lead to significant symptom improvement in the medical field. The narrative review aims to scrutinize the fluctuating scientist's views on the evaluation of patient and multimodal treatment of the UPOINT system.

Basis for diurnal exacerbation of neuropathic pain hypersensitivity and its application for drug development

In addition to diurnal rhythms in physiology and behavior, a variety of pathological conditions also exhibit marked day-night changes in symptom intensity, exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and chronic pain disorders. Currently, novel therapeutic approaches are facilitated by the development of chemical compounds targeted to key proteins that cause diurnal exacerbation of pathological events. Neuropathic pain is a chronic condition that occurs by tumor-induced nerve compression, cancer cell infiltration into the nerve, diabetes, and herpes virus infection. One troublesome hallmark symptom of neuropathic pain is hypersensitivity to normally innocuous stimuli known as "mechanical allodynia" that is often refractory to common analgesic therapies. Millions of patients worldwide presently endure neuropathic pain. We summarize the recent insights gained into the mechanism of diurnal exacerbation of neuropathic pain hypersensitivity and introduce the strategy of circadian clock-based drug development.

Multimodal nonopioid pain protocol provides equivalent pain control versus opioids following arthroscopic shoulder labral surgery: a prospective randomized controlled trial

BACKGROUND

This study aimed to compare postoperative pain and patient satisfaction in patients undergoing primary arthroscopic labral surgery managed with either a nonopioid alternative pain regimen or a traditional opioid pain regimen.

METHODS

Sixty consecutive patients undergoing primary arthroscopic shoulder labral surgery were assessed for participation. In accordance with the Consolidated Standards of Reporting Trials (CONSORT) 2010 statement, a prospective randomized controlled trial was performed. The 2 arms of the study were a multimodal nonopioid analgesic protocol as the experimental group and a standard opioid regimen as the control group. The primary outcome was postoperative pain scores (on a visual analog scale [VAS]) for the first 10 days postoperatively. Secondary outcomes included patient satisfaction, patient-reported outcomes, and complications. Randomization was performed with a random number generator, and all data were collected by blinded observers. Patients were not blinded.

RESULTS

Twelve patients did not meet the inclusion criteria or declined to participate. Thus, 48 patients were included in the final analysis: 24 in the nonopioid group and 24 in the opioid group. There was no significant difference in VAS or PROMIS (Patient-Reported Outcomes Measurement Information System) scores between patients in the 2 cohorts on any postoperative day (P > .05). When we controlled for confounding factors with repeated-measures mixed models, the nonopioid cohort reported significantly lower VAS and PROMIS (Patient-Reported Outcomes Measurement Information System) Pain Interference scores (P < .01) at all time points. No difference was found in reported adverse events (constipation, diarrhea, drowsiness, nausea, and upset stomach) between cohorts at any time point (P > .05).

CONCLUSION

This study found that a multimodal nonopioid pain regimen provided, at the minimum, equivalent pain control, an equivalent adverse reaction profile, and equivalent patient satisfaction when compared with a standard opioid-based regimen following arthroscopic shoulder labral surgery.

Comparison of efficacy and safety of gabapentin and duloxetine in painful diabetic peripheral neuropathy: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

In patients with diabetes mellitus, painful diabetic peripheral neuropathy (PDPN) is a frequent complication and can cause poor quality of life. We compared the efficacy and safety of duloxetine with those of gabapentin in patients with PDPN through a systematic review and meta-analysis of randomised controlled trials.

MATERIALS AND METHODS

PubMed, Embase and the Cochrane Library were searched for eligible studies published from database inception to January 2021. Visual Analogue Scale (VAS), sleep interference score, Clinical Global Impression of Change (CGIC), Patient Global Impression of Change (PGIC), Diabetic Neuropathy Symptom (DNS) score, Diabetic Neuropathic Examination (DNE) score, Neuropathic Disability Score (NDS) and side effects were used to compare duloxetine and gabapentin in patients with PDPN.

RESULTS

Three eligible randomised controlled trials involving 290 patients were included. No significant differences were observed between patients receiving duloxetine and gabapentin with respect to VAS (mean change difference = -1.23, 95% CI, -6.09 to 3.62; P = .62), sleep interference score (mean change difference = 0.42, 95% CI, -0.15 to 1.00; P = .15), CGIC (mean difference = 0.04, 95% CI, -0.11 to 0.20; P = .60), PGIC (mean difference= 0.24, 95% CI, -0.13 to 0.60; P = .21), DNS (mean change difference = 0.14, 95% CI, -0.35 to 0.63; P = .58), DNE (mean change difference = 0.26, 95% CI, -0.35 to 0.86; P = .41) and NDS (mean change difference = 0.30, 95% CI, -0.02 to 0.63; P = .07).

CONCLUSIONS

No significant differences were observed in the efficacy of duloxetine and gabapentin when treating patients with PDPN.

Management of diabetic neuropathy

Diabetic neuropathy is a neurodegenerative disorder that may alter both the somatic and autonomic peripheral nervous systems in the context of diabetes mellitus (DM). It is a prevalent and burdensome chronic complication of DM, that requires timely management. Optimized glycemic control (mainly for type 1 DM), multifactorial intervention (mainly for type 2 DM), with lifestyle intervention/physical exercise, and weight loss represent the basis of management for diabetic distal symmetrical polyneuropathy, and should be implemented early in the disease course. Despite better understanding of the pathogenetic mechanisms of diabetic peripheral neuropathy, there is still a stringent need for more pathogenetic-based agents that would significantly modify the natural history of the disease. The paper reviews the available drugs and current recommendations for the management of distal symmetrical polyneuropathy, including pain management, and for diabetic autonomic neuropathy. Evaluation of drug combinations that would perhaps be more efficient in slowing the progression of the disease or even reversing it, and that would provide a better pain management is still needed.

Pharmacokinetics of oral and compounded intravenous gabapentin in Duroc swine (Sus Scrofa)

The objective of this study was to determine the pharmacokinetics (PK) of oral (OS; 20 mg/kg) and compounded intravenous (IV; 5.5 mg/kg) gabapentin in 6 healthy, adult, Duroc pigs. Subjects were randomized to receive IV and OS gabapentin in a cross-over design, with at least 14 days of wash-out period between the two rounds of drug administrations. Blood samples were obtained before gabapentin administration and at various times up to 24 h, and harvested plasma was stored at -80°C until analysis. Concentration of gabapentin was quantified using a previously validated liquid chromatography/tandem mass spectrometry method, and compartment models were fitted to time-concentration data using non-linear mixed effect (population) analysis. A two-compartment model best fitted the data following IV administration. Typical values for volume of the central compartment and clearance and calculated volume of distribution at steady-state and terminal half-life were 170 ml/kg, 1.2 ml/(kg*min), and 594 ml/kg and 360 min, respectively. For the oral route, absorption half-life, estimated maximal plasma concentration and time to reach maximal plasma concentration were 58 min, 9155 ng/ml, and 194 min, respectively. Estimated oral bioavailability was 47%. Short-lived sedation (approximately 15 min) with sternal or lateral recumbency after IV administration was observed in all subjects without adverse clinical effects. Simulation based on the results of this study suggests that a first oral gabapentin dose of 15 mg/kg and subsequent doses of 8.5 mg/kg every 8 h would achieve and maintain plasma concentrations between 5 and 8 μg/ml in pigs.

Anesthetic Management of a Complex Regional Pain Syndrome (CRPS) Patient With Ketamine

Complex regional pain syndrome (CRPS) is a potentially debilitating form of neuropathic pain that may manifest following a traumatic injury or surgery. CRPS is also known as algodystrophy, causalgia, or reflex sympathetic dystrophy (RSD). Patients describe unbearable burning pain from nonnociceptive stimuli, such as when taking a shower or brushing against another object. Regular tactile stimuli encountered during routine dental procedures may not be well-tolerated by a patient with CRPS. Ketamine infusions have been reported to help alleviate acute exacerbations or "flare-ups" of CRPS symptoms. This case report provides a brief overview of CRPS pathophysiology and treatment including data supporting the use of ketamine infusions and a discussion regarding the anesthetic management of a patient with CRPS presenting for dental care under deep sedation utilizing high-dose intravenous ketamine.

Trigeminal neuralgia management after microvascular decompression surgery: two case reports

Trigeminal neuralgia (TN) involves chronic neuropathic pain, characterized by attacks of repeating short episodes of unilateral shock-like pain, which are abrupt in onset and termination. Anticonvulsants, such as carbamazepine, are the gold standard first-line drugs for pharmacological treatment. Microvascular decompression (MVD) surgery is often the course of action if pharmacological management with anticonvulsants is unsuccessful. MVD surgery is an effective therapy in approximately 83% of cases. However, persistent neuropathic pain after MVD surgery may require reintroduction of pharmacotherapy. This case report presents two patients with persistent pain after MVD requiring reintroduction of pharmacological therapy. Although MVD is successful for patients with failed pharmacological management, it is an invasive procedure and requires hospitalization of the patient. About one-third of patients suffer from recurrent TN after MVD. Often, alternative treatment protocols, including the reintroduction of medications, may be necessary to achieve improvement. This case report presents two cases of post-MVD recurrent pain. Further research is lacking on the success rates of subsequent medication therapy after MVD has proven less effective in managing TN.

Effect of gabapentin on sleep-deprivation-induced disruption of prepulse inhibition

RATIONALE

There are controversial reports on the effects of gabapentin in respect to psychotic symptoms. Prepulse inhibition of the acoustic startle response is an operational measure of sensorimotor gating. In laboratory rodents, deficits in sensorimotor gating are used to model behavioral endophenotypes of schizophrenia. Sleep deprivation disrupts prepulse inhibition and can be used as a psychosis model to evaluate effects of gabapentin.

OBJECTIVES

This study aimed to investigate behavioral effects of gabapentin in both naïve and sleep-deprived rats.

METHODS

Sleep deprivation was induced in male Wistar rats by using the modified multiple platform technique in a water tank for 72 h. The effect of water tank itself was studied in a sham group. The effects of oral acute and subchronic (4.5 days) gabapentin doses (25, 100, or 200 mg/kg/day) on sensorimotor gating and locomotor activity was evaluated by prepulse inhibition test and locomotor activity test, respectively. Plasma gabapentin levels of some groups and body weights of all groups were also assessed.

RESULTS

Sleep deprivation disrupted prepulse inhibition, increased locomotor activity, reduced gabapentin plasma levels, and body weights. Some gabapentin doses disrupted sensorimotor gating irrespective of sleep condition. Some gabapentin doses increased locomotor activity in non-sleep-deprived rats and decreased locomotor activity in sleep-deprived rats. On the contrary, gabapentin did not normalize sleep deprivation-induced disruption in sensorimotor gating.

CONCLUSIONS

Sleep deprivation via modified multiple platform technique could be used as an animal model for psychosis. Gabapentin may have dose- and duration-dependent effects on sensorimotor gating and locomotor activity.

Behavioral Effects of Continuously Administered Bergamot Essential Oil on Mice With Partial Sciatic Nerve Ligation

Neuropathic pain is an intractable chronic pain condition that is mainly caused by allodynia. We had previously reported that intra-plantar administration of bergamot essential oil (BEO) containing an aromatic compound significantly suppressed partial sciatic nerve ligation (PSNL)-induced mechanical allodynia via opioid mu receptors in mice. However, it has also been reported that the inhalation of BEO reduced formalin-induced nociceptive responses. Therefore, we aimed to elucidate whether the analgesic action of BEO is mediated by olfactory stimulation through volatile components. In the current study, BEO was continuously administered with an osmotic pump during PSNL surgery, and the effects on mice behavior were examined pharmacologically using a double activity monitoring system, which can detect two-dimensional planar motion in a cage with an infrared beam sensor as well as active motion with a running wheel. Here, we report that the two-dimensional planar activity significantly increased in mice with PSNL in the light phase (from 8 o’clock to 20 o’clock) but not in the dark phase (from 20 o’clock to 8 o’clock) from the second day after surgery. However, this increase was not observed when BEO was continuously administered. The effect of BEO on the two-dimensional planar counts in mice with PSNL was antagonized by naloxone hydrochloride. Regarding the running wheel activity, the number of rotations decreased by PSNL in the dark phase from the 8th day after surgery. However, this was not apparent with BEO use. The effect of BEO on the number of rotations was also antagonized by naloxone hydrochloride. Furthermore, inhalation of BEO in PSNL mice did not affect mechanical allodynia or the two-dimensional planar motion or running wheel activities. These findings indicate that BEO exhibits an analgesic action, which is mediated by opioid receptors and not by the olfactory system.

Neuropathic Pain and Sickle Cell Disease: a Review of Pharmacologic Management

PURPOSE OF REVIEW

Sickle cell disease (SCD) remains among the most common and severe monogenic disorders present in the world today. Although sickle cell pain has been traditionally characterized as nociceptive, a significant portion of sickle cell patients has reported neuropathic pain symptoms. Our review article will discuss clinical aspects of SCD-related neuropathic pain, epidemiology of neuropathic pain among individuals with SCD, pain mechanisms, and current and future potential pharmacological interventions.

RECENT FINDINGS

Neuropathic pain in SCD is a complicated condition that often has a lifelong and significant negative impact on life; therefore, improved pain management is considered a significant and unmet need. Neuropathic pain mechanisms are heterogeneous, and the difficulty in determining their individual contribution to specific pain types may contribute to poor treatment outcomes in this population. Our review article outlines several pharmacological modalities which may be employed to treat neuropathic pain in SCD patients.

A Practical Approach to Using Adjuvant Analgesics in Older Adults

The adjuvant analgesics are a large and diverse group of drugs that were developed for primary indications other than pain and are potentially useful analgesics for one or more painful conditions. The "adjuvant" designation reflects their early use as opioid co-analgesics for cancer pain. During the past 3 decades, their role in pain management has changed with the advent of many new entities, emerging data from numerous analgesic trials, and growing clinical experience. Many of these drugs are now used as primary analgesics for specific types of chronic pain. With proper patient selection and cautious administration, they can potentially contribute meaningfully to the management of chronic pain in older adults. A practical approach categorizes the many adjuvant analgesics by broad indications: multipurpose drugs and drugs that target neuropathic pain, musculoskeletal pain, and cancer pain, respectively. This article reviews the status of the evidence supporting the analgesic potential of the adjuvant analgesics and discusses best practices in terms of drug selection and dosing. J Am Geriatr Soc 68:691-698, 2020.

Neuropathic Pain and Burning Mouth Syndrome: An Overview and Current Update

Burning mouth syndrome/glossodynia and trigeminal neuropathic conditions can have serious negative impact on a patient's overall quality of life. These conditions are often hard to diagnose and even harder to fully treat and manage, but it is important for dentists/oral and maxillofacial surgeons to be aware of these conditions and modalities of their treatment. Often the only method for arriving at the proper diagnosis is for patients to undergo traditional approaches for treatment of presenting signs and symptoms, and it is the unexpected failure of interventional therapies that leads ultimately to a proper diagnosis.

γ-Aminobutyric Acid and Derivatives Reduce the Incidence of Acute Pain after Herpes Zoster - A Systematic Review and Meta-analysis

Herpes zoster (HZ) causes considerable pain and distress, and γ-Aminobutyric acid (GABA) and its derivatives are assumed to control this, but the available data are inconsistent. This meta-analysis and systematic review aimed to assess the effectiveness of GABA derivatives in the prevention of acute herpetic pain. The metaanalysis was conducted following the PRISMA guidelines using PICO format, registered in PROSPERO number CRD42018095758. PubMed, Web of Science, Ovid, Scopus, and EMBASE databases were searched. Records were included if they were randomized controlled trials of patients undergoing HZ infection, investigating the effect of GABA derivatives versus placebo in the treatment of HZ pain. Eligible trials were evaluated for the risk of bias. Then data were extracted and analysed. The number of patients with observed presence of pain after treatment was used to calculate odds ratio in a random effect model with the DerSimonian-Laird estimator. The I2 statistic was analysed for heterogeneity. The potential risk of bias was measured using Egger's regression test. The meta-analysis included three randomized controlled trials with a total of 297 patients. The incidence of acute HZ pain events for GABA group was significantly lower compared to placebo group,18/148 vs 44/149, respectively (OR = 0.36; 95% CI = 0.14 to 0.93; Z = 2.11; P = 0.035), Egger's test yielded P = 0.308. In conclusion, the present meta-analysis demonstrates that GABA derivatives reduce the incidence of acute herpetic pain. However, additional, well-designed randomized clinical trials are needed to determine their dose- and time-dependency regarding this symptom.

Observational, open-label, non-randomized study on the efficacy of onabotulinumtoxinA in the treatment of nummular headache: The pre-numabot study

Background

Nummular headache is a primary headache characterised by superficial, coin-shaped pain. Superficial sensory fibre dysfunction might be involved in its pathophysiology. Considering the mechanism of action of onabotulinumtoxinA, it could be a reasonable option in treatment of nummular headache. The aim of the study was to evaluate the efficacy and tolerability of onabotulinumtoxinA in a series of nummular headache patients.

Patients and methods

This was an observational, prospective, non-randomized and open-label study. Nummular headache patients with at least 10 headache days in three preceding months were included. They were administered 25 units of onabotulinumtoxinA. The primary endpoint was the decrease of headache days per month, evaluated between weeks 20 to 24, compared with baseline. The secondary endpoints included reduction of intense headache days and acute treatment days evaluated between weeks 20–24 and weeks 8–12, compared with baseline. The 30%, 50% and 75% responder rates were determined, and tolerability described.

Results

We included 53 patients, 67.9% females, with a median age of 54 years. Preventive treatment had been used previously in 60.4% of patients. The median diameter of the nummular headache was 5 cm. At baseline, the number of headache days per month was 24.5 (7.3); the number of intense headache days was 12.5 (10.1), and the number of acute treatment days was 12.8 (7.8). After onabotulinumtoxinA, the mean number of headache days per month decreased to 6.9 (9.3) between weeks 20 and 24 ( p < 0.001). Secondary endpoints concerning intense headache days per month and acute treatment days per month were also statistically significant ( p < 0.001). The 50% responder rate, evaluated between weeks 20 and 24, was 77.4% and the 75% responder rate was 52.8%. Concerning tolerability, 26 patients (49.1%) experienced an adverse event (AE), the commonest being injection-site pain in 12 cases (22.6%). There were no moderate or severe AEs.

Conclusion

It was found that after injecting onabotulinumtoxinA, the number of headache days per month was reduced in nummular headache patients. The number of intense headache days per month and acute treatment days were also lowered. No serious adverse events occurred during treatment.

A comparative double-blind randomized study on the effectiveness of Duloxetine and Gabapentin on painful diabetic peripheral polyneuropathy

Background: The most common cause of polyneuropathy is diabetes mellitus. Neuropathic pain is seen in 26% of diabetic population. Therapeutic techniques for this disease can become challenging. Method: This study was a prospective comparative double-blind randomized study which was conducted during an eight-week period. Totally, 104 painful diabetic peripheral polyneuropathy (PDPP) patients who had a minimum Visual Analog Scale (VAS) of 40 millimeters, received no pain-controlling medication, and had no other severe disease at its final stage were randomly assigned to two groups (n=52) through the four block method. One group received Duloxetine and the other received Gabapentin. The effectiveness was measured through primary effectiveness (VAS scale) and secondary effectiveness (Sleep Interference Score, and Clinical Global Impression of Change (CGIC)). Medication compliance was assessed by enumerating the number of patients who refused treatment because of side effects. The Fisher's exact T-test and ANOVA were used for data analysis. This study was approved by the Ethics Committee of Jundishapur, University of Medical sciences Ahvaz, Iran, under reference number: IR.AJUMS.REC.1395.78. In addition, this study was registered and approved in the Iranian Registry of Clinical Trials (IRCT ID: IRCT20161023030455N2) (http://irct.ir/). Results: VAS, Sleep Interference Score, and CGIC were significantly improved (P<0.05) through time in both groups, [For GBP: VAS^Baseline=64±20.03, VAS^week1=55.32±18.76, VAS^week4=44.68±15.82, VAS^week8=39.43±14.32; For DLX: VAS^Base-line=62±21.18, VAS^week1=58.76±20.37, VAS^week4=45.84±16.21, VAS^week8=36.78±15.62] while a significant difference between the two groups was not observed (P<0.05). However, such significant improvements were not observed in the Duloxetine group at the end of the first week (P=674). Improvement in Sleep Interference Score and CGIC were similar to the results for the VAS scale. Side effects in the Duloxetine group (n=2) compared to the Gabapentin group (n=9) were significantly less (P<0.001). As a result, medication acceptance in the Duloxetine group (n=47) was significantly better than the Gabapentin (n=41) group (P<0.001). Conclusion: Both Duloxetine and Gabapentin are effective for the treatment of PDPP. On the one hand, Gabapentin shows the effect earlier while has more side effects. Conversely, Duloxetine has better medication compliance. Trial registration: The method of this study was approved by the Ethics Committee of Jundishapur University of Medical Sciences, Ahvaz, Iran, under reference number: IR.AJUMS.REC.1395.78. In addition, this study was registered and approved in the Iranian Registry of Clinical Trials (IRCT ID: IRCT20161023030455N2) (http://irct.ir/).

Diabetic neuropathy

The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.

Diabetic neuropathy

The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.

Interventions to chronic prostatitis/Chronic pelvic pain syndrome treatment. Where are we standing and what's next?

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a frustrating syndrome. The pathogenesis and state of the art treatment of CP/CPPS are not known. A wide variety of therapies including anti-inflammatories, antibiotics, alpha-blockers, neuropathic pain modulators, and 5α-reductase inhibitors are in practice. These treatment strategies focus on alleviating symptoms in specific domains without treating root-cause and therapeutic outcome is far from satisfactory. We review the literature on current pharmacological treatments for CP/CPPS in detail and suggest future perspectives to modify the treatment strategies. We suggest that introducing novel treatment strategies such as gene editing, and T_regs expressing chimeric receptors may improve the treatment outcomes by inducing immune tolerance and controlling expression of pro-inflammatory cytokines.

The Effect of Once-Daily Gabapentin Extended Release Formulation in Patients With Postamputation Pain

Objectives

To compare gabapentin extended-release, a gastro-retentive formulation, in relieving postamputation pain among gabapentin-experienced and gabapentin-naïve patients.

Design

Open-labeled pilot study.

Subjects

Sixteen patients with postamputation pain (8 patients in the gabapentin-experienced and 8 patients in the gabapentin-naïve groups).

Methods

Patients were started on gabapentin extended-release and were followed up for 8 weeks. Patients reported their pain severity during rest and movement using a numeric rating scale (NRS), interference of pain with daily activities using the modified brief pain inventory (MBPI) questionnaire, and treatment satisfaction using the treatment satisfaction questionnaire for medication (TSQM).

Results

Patients from both gabapentin-experienced and gabapentin-naïve groups achieved a significant and sustainable pain relief over the course of therapy. The pain scores at rest decreased in both gabapentin-experienced and gabapentin-naïve groups from 5.88 ± 1.36 and 4.88 ± 2.95 to 1.88 ± 0.99 and 1.38 ± 1.51, respectively. An average percent of pain relief with gabapentin extended-release was noted to be significant (p < 0.01) after 8 weeks of therapy among gabapentin-experienced (81.25 ± 16.42%) and gabapentin-naïve groups (85 ± 17.73%) when compared to baseline for gabapentin-experienced (31.25 ± 29%) and gabapentin-naïve groups (36.25 ± 34.2%), respectively. Gabapentin-experienced and gabapentin-naïve groups had no significant difference in global satisfaction from treatment (79.14 ± 10.47 and 83.3 ± 20.82), convenience of treatment (73.78 ± 19.04 and 90.44 ± 11.66), effectiveness of treatment (72.6 ± 10.1 and 79.73 ± 11.6). The only statistically significant difference among gabapentin-experienced and gabapentin-naïve groups was found in adverse event tolerability (65.78 ± 10.36 and 85.8 ± 10.14, p < 0.01).

Conclusion

Once-daily dosing of gabapentin-extended release showed significant improvement in pain severity and functional status, with no difference found between gabapentin-experienced versus gabapentin-naïve patients.

Evoked hypoalgesia is accompanied by tonic pain and immune cell infiltration in the dorsal root ganglia at late stages of diabetic neuropathy in mice

Diabetic peripheral neuropathy is a major debilitating late complication of diabetes, which significantly reduces the quality of life in patients. Diabetic peripheral neuropathy is associated with a wide spectrum of sensory abnormalities, where in loss of sensation or hypoalgesia to applied external stimuli is paradoxically accompanied by debilitating tonic spontaneous pain. In numerous studies on animal models of diabetic peripheral neuropathy, behavioural measurements have been largely confined to analysis of evoked withdrawal to mechanical and thermal stimuli applied to dermatomes, whereas spontaneous, on-going pain has not been widely studied. In the Streptozotocin model of type 1 diabetes, we employed the Conditioned Place Preference test to assess tonic pain. Our results indicate that both phases, that is, early evoked hypersensitivity (i.e. 5–7 weeks post-Streptozotocin) as well as late stage hypoalgesia (i.e. 17–20 weeks post-Streptozotocin) are accompanied by significant tonic pain in mice with diabetic peripheral neuropathy. We also report on the temporal relation between on-going pain and neuropathological changes in the dorsal root ganglia of mice with diabetic peripheral neuropathy up to 6 months post-Streptozotocin. Neither early hypersensitivity nor late hypoalgesia were associated with markers of cellular stress in the dorsal root ganglia. Whereas significant neutrophil infiltration was observed in the dorsal root ganglia over both early and late stages post-Streptozotocin, T-cell infiltration in the dorsal root ganglia was prominent at late stages post-Streptozotocin. Thus, longitudinal analyses reveal that similar to patients with chronic diabetic peripheral neuropathy, mice show tonic pain despite sensory loss after several months in the Streptozotocin model, which is accompanied by neuroimmune interactions in the dorsal root ganglia.

PHARMACOKINETICS OF ORAL GABAPENTIN IN CARIBBEAN FLAMINGOS ( PHOENICOPTERUS RUBER RUBER)

Gabapentin is a first-line treatment for neuropathic pain and adjunct anticonvulsant medication in humans and other species. Gabapentin may have advantages over other analgesics because of its broad therapeutic range with limited adverse effects and wide availability as an oral formulation. This study determined the pharmacokinetics of gabapentin in Caribbean flamingos ( Phoenicopterus ruber ruber) after a single-dose oral administration of either 15 mg/kg ( n = 6) or 25 mg/kg ( n = 6). Plasma gabapentin concentrations were determined using liquid chromatography with mass spectrometry, and pharmacokinetic analysis was performed using noncompartmental methods. Respectively for the 15 mg/kg and 25 mg/kg dose, mean peak plasma concentration ( C_max) was (mean ± pseudo SD) 13.23 ± 1.47 and 24.48 ± 5.81 μg/ml; mean time to peak plasma concentration ( T_max) was 0.50 ± 0.24 and 0.56 ± 0.28 hr; mean area under the curve (AUC) was 76.0 ± 26.3 and 114.7 ± 27.5 hr·μg/ml; and mean terminal half-life ( T_1/2) was 3.39 ± 0.90 and 4.46 ± 1.12 hr. Based on the results of this study, gabapentin dosed at 25 mg/kg orally in most Caribbean flamingos is likely to maintain plasma concentrations above the therapeutic range established for humans for approximately 12 hr.

Canadian Urological Association best practice report on chronic scrotal pain

N/A

Gabapentin dose and the 30-day risk of altered mental status in older adults: A retrospective population-based study

Gabapentin is an effective treatment for chronic neuropathic pain but may cause dizziness, drowsiness, and confusion in some older adults. The goal of this study was to assess the association between gabapentin dosing and adverse outcomes by obtaining estimates of the 30-day risk of hospitalization with altered mental status and mortality in older adults (mean age 76 years) in Ontario, Canada initiated on high dose (>600 mg/day; n = 34,159) compared to low dose (≤600 mg/day; n = 76,025) oral gabapentin in routine outpatient care. A population-based, retrospective cohort study assessing new gabapentin use between 2002 to 2014 was conducted. The primary outcome was 30-day hospitalization with an urgent head computed tomography (CT) scan in the absence of evidence of stroke (a proxy for altered mental status). The secondary outcome was 30-day all-cause mortality. The baseline characteristics measured in the two dose groups were similar. Initiation of a high versus low dose of gabapentin was associated with a higher risk of hospitalization with head CT scan (1.27% vs. 1.06%, absolute risk difference 0.21%, adjusted relative risk 1.29 [95% CI 1.14 to 1.46], number needed to treat 477) but not a statistically significant higher risk of mortality (1.25% vs. 1.16%, absolute risk difference of 0.09%, adjusted relative risk of 1.01 [95% CI 0.89 to 1.14]). Overall, the risk of being hospitalized with altered mental status after initiating gabapentin remains low, but may be reduced through the judicious use of gabapentin, use of the lowest dose to control pain, and vigilance for early signs of altered mental status.

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.

Erythromelalgia: a cutaneous manifestation of neuropathy?

The low prevalence of erythromelalgia, classified as an orphan disease, poses diagnostic and therapeutic difficulties. The aim of this review is to be an update of the specialized bibliography. Erythromelalgia is an infrequent episodic acrosyndrome affecting mainly both lower limbs symmetrically with the classic triad of erythema, warmth and burning pain. Primary erythromelalgia is an autosomal dominant inherited disorder, while secondary is associated with myeloproliferative diseases, among others. In its etiopathogenesis, there are neural and vascular abnormalities that can be combined. The diagnosis is based on exhaustive clinical history and physical examination. Complications are due to changes in the skin barrier function, ischemia and compromise of cutaneous nerves. Because of the complexity of its pathogenesis, erythromelalgia should always be included in the differential diagnosis of conditions that cause chronic pain and/or peripheral edema. The prevention of crisis is based on a strict control of triggers and promotion of preventive measures. Since there is no specific and effective treatment, control should focus on the underlying disease. However, there are numerous topical and systemic therapies that patients can benefit from.

Oxcarbazepine for neuropathic pain

BACKGROUND

Several anticonvulsant drugs are used in the management of neuropathic pain. Oxcarbazepine is an anticonvulsant drug closely related to carbamazepine. Oxcarbazepine has been reported to be efficacious in the treatment of neuropathic pain, but evidence from randomised controlled trials (RCTs) is conflicting. Oxcarbazepine is reportedly better tolerated than carbamazepine. This is the first update of a review published in 2013.

OBJECTIVES

To assess the benefits and harms of oxcarbazepine for different types of neuropathic pain.

SEARCH METHODS

On 21 November 2016, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE and Embase. We searched the Chinese Biomedical Retrieval System (January 1978 to November 2016). We searched the US National Institutes of Health (NIH) databases and the World Health Organization (WHO) International Clinical Trials Registry Platform for ongoing trials in January 2017, and we wrote to the companies who make oxcarbazepine and to pain experts requesting additional information.

SELECTION CRITERIA

All RCTs and randomised cross-over studies of oxcarbazepine for the treatment of people of any age or sex with any neuropathic pain were eligible. We planned to include trials of oxcarbazepine compared with placebo or any other intervention with a treatment duration of at least six weeks, regardless of administration route and dose.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

Five multicentre, randomised, placebo-controlled, double-blind trials with a total of 862 participants were eligible for inclusion in this updated review. Three trials involved participants with painful diabetic peripheral neuropathy (DPN) (n = 634), one included people with neuropathic pain due to radiculopathy (n = 145), and one, which was newly identified at this update, involved participants with peripheral neuropathic pain of mixed origin (polyneuropathy, peripheral nerve injury or postherpetic neuralgia) (n = 83). Some studies did not report all outcomes of interest. For painful DPN, compared to the baseline, the proportion of participants who reported at least a 50% or 30% reduction of pain scores after 16 weeks of treatment in the oxcarbazepine group versus the placebo group were: at least 50% reduction: 34.8% with oxcarbazepine versus 18.2% with placebo (risk ratio (RR) 1.91, 95% confidence interval (CI) 1.08 to 3.39, number of people needed to treat for an additional beneficial outcome (NNTB) 6, 95% CI 3 to 41); and at least 30% reduction: 44.9% with oxcarbazepine versus 28.6% with placebo (RR 1.57, 95% CI 1.01 to 2.44; NNTB 6, 95% CI 3 to 114; n = 146). Both results were based on data from a single trial, since two trials that found little or no benefit did not provide data that could be included in a meta-analysis. Although these trials were well designed, incomplete outcome data and possible unblinding of participants due to obvious adverse effects placed the results at a high risk of bias. There was also serious imprecision and a high risk of publication bias. The radiculopathy trial reported no benefit for the outcome 'at least 50% pain relief' from oxcarbazepine. In mixed neuropathies, 19.3% of people receiving oxcarbazepine versus 4.8% receiving placebo had at least 50% pain relief. These small trials had low event rates and provided, at best, low-quality evidence for any outcome. The proportion of people with 'improved' or 'very much improved' pain was 45.9% with oxcarbazepine versus 30.1% with placebo in DPN (RR 1.46, 95% CI 1.13 to 1.88; n = 493; 2 trials; very-low-quality evidence) and 23.9% with oxcarbazepine versus 14.9% with placebo in radiculopathy (RR 1.61, 95% CI 0.81 to 3.20; n = 145).We found no trials in other types of neuropathic pain such as trigeminal neuralgia.Trial reports stated that most adverse effects were mild to moderate in severity. Based on moderate-quality evidence from the three DPN trials, serious adverse effects occurred in 8.3% with oxcarbazepine and 2.5% with placebo (RR 3.65, 95% CI 1.45 to 9.20; n = 634; moderate-quality evidence). The number needed to treat for an additional harmful (serious adverse effect) outcome (NNTH) was 17 (95% CI 11 to 42). The RR for serious adverse effects in the radiculopathy trial was 3.13 (95% CI 0.65 to 14.98, n = 145). The fifth trial did not provide data.More people withdrew because of adverse effects with oxcarbazepine than with placebo (DPN: 25.6% with oxcarbazepine versus 6.8% with placebo; RR 3.83, 95% CI 2.29 to 6.40; radiculopathy: 42.3% with oxcarbazepine versus 14.9% with placebo; RR 2.84, 95% CI 1.55 to 5.23; mixed neuropathic pain: 13.5% with oxcarbazepine versus 1.2% with placebo; RR 11.51, 95% CI 1.54 to 86.15).

AUTHORS' CONCLUSIONS

This review found little evidence to support the effectiveness of oxcarbazepine in painful diabetic neuropathy, neuropathic pain from radiculopathy and a mixture of neuropathies. Some very-low-quality evidence suggests efficacy but small trials, low event rates, heterogeneity in some measures and a high risk of publication bias means that we have very low confidence in the measures of effect. Adverse effects, serious adverse effects and adverse effects leading to discontinuation are probably more common with oxcarbazepine than placebo; however, the numbers of participants and event rates are low. More well-designed, multicentre RCTs investigating oxcarbazepine for various types of neuropathic pain are needed, and selective publication of studies or data should be avoided.