Topiramate vs placebo in painful diabetic neuropathy: analgesic and metabolic effects

Safety and Efficacy of Topiramate in Individuals With Cryptogenic Sensory Peripheral Neuropathy With Metabolic Syndrome: The TopCSPN Randomized Clinical Trial

Importance

Cryptogenic sensory peripheral neuropathy (CSPN) is highly prevalent and often disabling due to neuropathic pain. Metabolic syndrome and its components increase neuropathy risk. Diet and exercise have shown promise but are limited by poor adherence.

Objective

To determine whether topiramate can slow decline in intraepidermal nerve fiber density (IENFD) and/or neuropathy-specific quality of life measured using the Norfolk Quality of Life-Diabetic Neuropathy (NQOL-DN) scale.

Design, Setting, and Participants

Topiramate as a Disease-Modifying Therapy for CSPN (TopCSPN) was a double-blind, placebo-controlled, randomized clinical trial conducted between February 2018 and October 2021. TopCSPN was performed at 20 sites in the National Institutes of Health-funded Network for Excellence in Neurosciences Clinical Trials (NeuroNEXT). Individuals with CSPN and metabolic syndrome aged 18 to 80 years were screened and randomly assigned by body mass index (<30 vs ≥30), which is calculated as weight in kilograms divided by height in meters squared. Patients were excluded if they had poorly controlled diabetes, prior topiramate treatment, recurrent nephrolithiasis, type 1 diabetes, use of insulin within 3 months before screening, history of foot ulceration, planned bariatric surgery, history of alcohol or drug overuse in the 2 years before screening, family history of a hereditary neuropathy, or an alternative neuropathy cause.

Interventions

Participants received topiramate or matched placebo titrated to a maximum-tolerated dose of 100 mg per day.

Main Outcomes and Measures

IENFD and NQOL-DN score were co-primary outcome measures. A positive study was defined as efficacy in both or efficacy in one and noninferiority in the other.

Results

A total of 211 individuals were screened, and 132 were randomly assigned to treatment groups: 66 in the topiramate group and 66 in the placebo group. Age and sex were similar between groups (topiramate: mean [SD] age, 61 (10) years; 38 male [58%]; placebo: mean [SD] age, 62 (11) years; 44 male [67%]). The difference in change in IENFD and NQOL-DN score was noninferior but not superior in the intention-to-treat (ITT) analysis (IENFD, 0.21 fibers/mm per year; 95% CI, -0.43 to ∞ fibers/mm per year and NQOL-DN score, -1.52 points per year; 95% CI, -∞ to 1.19 points per year). A per-protocol analysis excluding noncompliant participants based on serum topiramate levels and those with major protocol deviations demonstrated superiority in NQOL-DN score (-3.69 points per year; 95% CI, -∞ to -0.73 points per year). Patients treated with topiramate had a mean (SD) annual change in IENFD of 0.56 fibers/mm per year relative to placebo (95% CI, -0.21 to ∞ fibers/mm per year). Although IENFD was stable in the topiramate group compared with a decline consistent with expected natural history, this difference did not demonstrate superiority.

Conclusion and Relevance

Topiramate did not slow IENFD decline or affect NQOL-DN score in the primary ITT analysis. Some participants were intolerant of topiramate. NQOL-DN score was superior among those compliant based on serum levels and without major protocol deviations.

Trial Registration

ClinicalTrials.gov Identifier: NCT02878798.

Effects of autonomic nervous system disorders on male infertility

The male reproductive functions are largely regulated by the autonomic nervous system. Male sexual behavior and fertility primarily depend on the normal function of the higher neural centers related to the autonomic nervous system, the hypothalamic-pituitary-gonadal axis, the autonomic nervous components within the spinal cord and spinal nerves, and certain somatic nerves in the pelvic floor. In this review article, we will summarize the role of the autonomic nervous system in regulating male reproductive capabilities and fertility, its impact on male infertility under abnormal conditions, including the role of drug-induced autonomic nervous dysfunctions on male infertility. The main purpose of this article was to provide an overview of the effects of autonomic nervous dysfunction on male reproductive function and shed light on the potential therapeutic target for male infertility.

Topiramate affords neuroprotection in diabetic neuropathy model via downregulating spinal GFAP/inflammatory burden and improving neurofilament production

The current study aimed to test the neuroprotective action of topiramate in mouse peripheral diabetic neuropathy (DN) and explored some mechanisms underlying this action. Mice were assigned as vehicle group, DN group, DN + topiramate 10-mg/kg and DN + topiramate 30-mg/kg. Mice were tested for allodynia and hyperalgesia and then spinal cord and sciatic nerves specimens were examined microscopically and neurofilament heavy chain (NEFH) immunostaining was performed. Results indicated that DN mice had lower the hotplate latency time (0.46-fold of latency to licking) and lower von-Frey test pain threshold (0.6-fold of filament size) while treatment with topiramate increased these values significantly. Sciatic nerves from DN control mice showed axonal degeneration while spinal cords showed elevated GFAP (5.6-fold) and inflammatory cytokines (∼3- to 4-fold) but lower plasticity as indicated by GAP-43 (0.25-fold). Topiramate produced neuroprotection and suppressed spinal cord GFAP/inflammation but enhanced GAP-43. This study reinforces topiramate as neuroprotection and explained some mechanisms included in alleviating neuropathy.

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.

Diabetic neuropathy: an insight on the transition from synthetic drugs to herbal therapies

The global pandemic of prediabetes and diabetes has led to a severe corresponding complication of these disorders. Neuropathy is one of the most prevalent complication of diabetes is, affecting blood supply of the peripheral nervous system that may eventually results into loss of sensations, injuries, diabetic foot and death. The utmost identified risk of diabetic neuropathy is uncontrolled high blood glucose levels. However, aging, body mass index (BMI), oxidative stress, inflammation, increased HbA1c levels and blood pressure are among the other key factors involved in the upsurge of this disease. The so far treatment to deal with diabetic neuropathy is controlling metabolic glucose levels. Apart from this, drugs like reactive oxygen species (ROS) inhibitors, aldose reductase inhibitors, PKC inhibitors, Serotonin-norepinephrine reuptake inhibitors (SNRIs), anticonvulsants, N-methyl-D-aspartate receptor (NMDAR) antagonists, are the other prescribed medications. However, the related side-effects (hallucinations, drowsiness, memory deficits), cost, poor pharmacokinetics and drug resistance brought the trust of patients down and thus herbal renaissance is occurring all over the word as the people have shifted their intentions from synthetic drugs to herbal remedies. Medicinal plants have widely been utilized as herbal remedies against number of ailments in Indian medicinal history. Their bioactive components are very much potent to handle different chronic disorders and complications with lesser-known side effects. Therefore, the current article mainly concludes the etiology and pathophysiology of diabetic neuropathy. Furthermore, it also highlights the important roles of medicinal plants and their naturally occurring bioactive compounds in addressing this disease.

Exercise and Nutraceuticals: Eminent approach for Diabetic Neuropathy

Diabetic neuropathy is an incapacitating chronic pathological condition that encompasses a large group of diseases and manifestations of nerve damage. It affects approximately 50% of patients with diabetes mellitus. Autonomic, sensory, and motor neurons are affected. Disabilities are severe, along with poor recovery and diverse pathophysiology. Physical exercise and herbal-based therapies have the potential to decrease the disabilities associated with diabetic neuropathy. Aerobic exercises like walking, weight lifting, the use of nutraceuticals and herbal extracts are found to be effective. Literature from the public domain was studied emphasizing various beneficial effects of different exercises, use of herbal and nutraceuticals for their therapeutic action in diabetic neuropathy. Routine exercises and administration of herbal and nutraceuticals, either the extract of plant material containing the active phytoconstituent or isolated phytoconstituent at safe concentration, have been shown to have promising positive action in the treatment of diabetic neuropathy. Exercise has shown promising effects on vascular and neuronal health and has proven to be well effective in the treatment as well as prevention of diabetic neuropathy by various novel mechanisms, including herbal and nutraceuticals therapy is also beneficial for the condition. They primarily show the anti-oxidant effect, secretagogue, anti-inflammatory, analgesic, and neuroprotective action. Severe adverse events are rare with these therapies. The current review investigates the benefits of exercise and nutraceutical therapies in the treatment of diabetic neuropathy.

Pharmacological Management of Painful Peripheral Neuropathies: A Systematic Review

Introduction

Peripheral neuropathic pain (PNP) arises either acutely or in the chronic phase of a lesion or disease of the peripheral nervous system and is associated with a notable disease burden. The management of PNP is often challenging. The aim of this systematic review was to evaluate current evidence, derived from randomized controlled trials (RCTs) that have assessed pharmacological interventions for the treatment of PNP due to polyneuropathy (PN).

Methods

A systematic search of the PubMed database led to the identification of 538 papers, of which 457 were excluded due to not meeting the eligibility criteria, and two articles were identified through screening of the reference lists of the 81 eligible studies. Ultimately, 83 papers were included in this systematic review.

Results

The best available evidence for the management of painful diabetic polyneuropathy (DPN) is for amitriptyline, duloxetine, gabapentin, pregabalin and venlafaxine as monotherapies and oxycodone as add-on therapy (level II of evidence). Tramadol appears to be effective when used as a monotherapy and add-on therapy in patients with PN of various etiologies (level II of evidence). Weaker evidence (level III) is available on the effectiveness of several other agents discussed in this review for the management of PNP due to PN.

Discussion

Response to treatment may be affected by the underlying pathophysiological mechanisms that are involved in the pathogenesis of the PN and, therefore, it is very important to thoroughly investigate patients presenting with PNP to determine the causes of this neuropathy. Future RCTs should be conducted to shed more light on the use of pharmacological approaches in patients with other forms of PNP and to design specific treatment algorithms.

Electronic supplementary material

The online version of this article (10.1007/s40122-020-00210-3) contains supplementary material, which is available to authorized users.

Management of Neuropathic Pain in Polyneuropathy

PURPOSE OF REVIEW

Many polyneuropathies cause significant neuropathic pain, resulting in substantial morbidity and reduced quality of life. Appropriate management is crucial for maintaining quality of life for patients with painful polyneuropathies. The US Food and Drug Administration (FDA) has only approved one new drug for painful diabetic neuropathy in the past decade, a topical capsaicin patch that was initially approved for the treatment of postherpetic neuralgia in 2009. Gabapentinoids and serotonin norepinephrine reuptake inhibitors (SNRIs) continue to have an advantage in safety profiles and efficacy. Other antiepileptic medications remain second-line agents because of fewer studies documenting efficacy.

RECENT FINDINGS

This article reviews recent literature on complementary and pharmacologic therapies for the management of painful polyneuropathies. Exercise has emerged as an important therapeutic tool and may also improve the underlying polyneuropathy in the setting of obesity, metabolic syndrome, and diabetes.

SUMMARY

The approach to management of painful polyneuropathies is multifactorial, using both pharmacologic and nonpharmacologic measures to improve pain severity and patient quality of life.

Mirogabalin and emerging therapies for diabetic neuropathy

There are currently no approved disease-modifying therapies for diabetic neuropathy, and there are only 3 US Food and Drug Administration-approved therapies (pregabalin, duloxetine, and tapentadol) for painful diabetic neuropathy. They each have moderate efficacy with adverse effects limiting optimal dose titration. There is a considerable need for new therapies for the management of painful diabetic neuropathy. We reviewed the potential role of mirogabalin, which like gabapentin and pregabalin modulates the alpha-2/delta-1 subunit of the voltage-gated calcium channel, allowing the influx of calcium and release of neurotransmitters at the synaptic cleft in the central nervous system and spinal cord. It has shown efficacy and good tolerability in a Phase II study in diabetic painful neuropathy and based on the results of two Phase III clinical trials in diabetic painful neuropathy and post-herpetic neuralgia, Daiichi Sankyo submitted a marketing application for neuropathic pain in Japan in February 2018. We have also reviewed potential new therapies, currently in Phase II clinical trials that may modify disease and/or relieve neuropathic pain through novel modes of action.

Diabetic Peripheral Neuropathy: Epidemiology, Diagnosis, and Pharmacotherapy

PURPOSE

Diabetic peripheral neuropathy (DPN) is the commonest cause of neuropathy worldwide, and its prevalence increases with the duration of diabetes. It affects approximately half of patients with diabetes. DPN is symmetric and predominantly sensory, starting distally and gradually spreading proximally in a glove-and-stocking distribution. It causes substantial morbidity and is associated with increased mortality. The unrelenting nature of pain in this condition can negatively affect a patient's sleep, mood, and functionality and result in a poor quality of life. The purpose of this review was to critically review the current literature on the diagnosis and treatment of DPN, with a focus on the treatment of neuropathic pain in DPN.

METHODS

A comprehensive literature review was undertaken, incorporating article searches in electronic databases (EMBASE, PubMed, OVID) and reference lists of relevant articles with the authors' expertise in DPN. This review considers seminal and novel research in epidemiology; diagnosis, especially in relation to novel surrogate end points; and the treatment of neuropathic pain in DPN. We also consider potential new pharmacotherapies for painful DPN.

FINDINGS

DPN is often misdiagnosed and inadequately treated. Other than improving glycemic control, there is no licensed pathogenetic treatment for diabetic neuropathy. Management of painful DPN remains challenging due to difficulties in personalizing therapy and ascertaining the best dosing strategy, choice of initial pharmacotherapy, consideration of combination therapy, and deciding on defining treatment for poor analgesic responders. Duloxetine and pregabalin remain first-line therapy for neuropathic pain in DPN in all 5 of the major published guidelines by the American Association of Clinical Endocrinologists, American Academy of Neurology, European Federation of Neurological Societies, National Institute of Clinical Excellence (United Kingdom), and the American Diabetes Association, and their use has been approved by the US Food and Drug Administration.

IMPLICATIONS

Clinical recognition of DPN is imperative for allowing timely symptom management to reduce the morbidity associated with this condition.

Carbamazepine, a beta-cell protecting drug, reduces type 1 diabetes incidence in NOD mice

Pancreatic beta-cells are selectively destroyed by the host immune system in type 1 diabetes. Thus, drugs that preserve beta-cell mass and/or function have the potential to prevent or slow the progression of this disease. We recently reported that the use-dependent sodium channel blocker, carbamazepine, protects beta-cells from inflammatory cytokines in vitro. Here, we tested the effects of carbamazepine treatment in female non-obese diabetic (NOD) mice by supplementing LabDiet 5053 with 0.5% w/w carbamazepine to achieve serum carbamazepine levels of 14.98 ± 3.19 µM. Remarkably, diabetes incidence over 25 weeks, as determined by fasting blood glucose, was ~50% lower in carbamazepine treated animals. Partial protection from diabetes in carbamazepine-fed NOD mice was also associated with improved glucose tolerance at 6 weeks of age, prior to the onset of diabetes in our colony. Less insulitis was detected in carbamazepine treated NOD mice at 6 weeks of age, but we did not observe differences in CD4⁺ and CD8⁺ T cell composition in the pancreatic lymph node, as well as circulating markers of inflammation. Taken together, our results demonstrate that carbamazepine reduces the development of type 1 diabetes in NOD mice by maintaining functional beta-cell mass.

Alternatives to Opioids in the Pharmacologic Management of Chronic Pain Syndromes: A Narrative Review of Randomized, Controlled, and Blinded Clinical Trials

Chronic pain exerts a tremendous burden on individuals and societies. If one views chronic pain as a single disease entity, then it is the most common and costly medical condition. At present, medical professionals who treat patients in chronic pain are recommended to provide comprehensive and multidisciplinary treatments, which may include pharmacotherapy. Many providers use nonopioid medications to treat chronic pain; however, for some patients, opioid analgesics are the exclusive treatment of chronic pain. However, there is currently an epidemic of opioid use in the United States, and recent guidelines from the Centers for Disease Control (CDC) have recommended that the use of opioids for nonmalignant chronic pain be used only in certain circumstances. The goal of this review was to report the current body of evidence-based medicine gained from prospective, randomized-controlled, blinded studies on the use of nonopioid analgesics for the most common noncancer chronic pain conditions. A total of 9566 studies were obtained during literature searches, and 271 of these met inclusion for this review. Overall, while many nonopioid analgesics have been found to be effective in reducing pain for many chronic pain conditions, it is evident that the number of high-quality studies is lacking, and the effect sizes noted in many studies are not considered to be clinically significant despite statistical significance. More research is needed to determine effective and mechanism-based treatments for the chronic pain syndromes discussed in this review. Utilization of rigorous and homogeneous research methodology would likely allow for better consistency and reproducibility, which is of utmost importance in guiding evidence-based care.

Comparison of the effect of topiramate versus gabapentin on neuropathic pain in patients with polyneuropathy: A randomized clinical trial

BACKGROUND

Neuropathic pain is one of the most common complaints of neurologic clinics. Neuropathic pain is common and important and has inappropriate complications, and despite their importance, there is no effective treatment for them.

OBJECTIVE

Because of the importance of neuropathic pain and safe and effective treatment, in this study, we determined the effect of topiramate versus gabapentin in patients with neuropathic pain.

METHODS

In this randomized clinical trial, 30 patients with pain attributed to neuropathy who had at least one month of neuropathic pain in one area, were randomized to receive either gabapentin, titrated from 300 mg/day to a maximum of 900 mg/day or topiramate, titrated from 50 mg/day to a maximum of 100 mg/day after a 4-week period in the neurology clinic of Imam Khomeini Hospital of Urmia city, Iran in 2015. Complication, drug tolerance rate and pain were investigated. The pain was measured on visual analog scale (VAS). The data were analyzed by SPSS version 18, and using descriptive statistics, t-test, and ANOVA.

RESULTS

In patients treated by gabapentin, the primary pain score was 74.33±10.29, this score decreased to 49.46±11.41 and 29.93±11.92 in the second and fourth week after intervention with gabapentin. In topiramate treated patients, the primary score was 76.00±9.69. It decreased to 54.33±10.31 and 34.20±6.09 at the same time. There were no significant differences between both groups in terms of average reduction of pain intensity [gabapentin group (59.73%) compared with topiramate (55%) (p=0.48)]. In the present study, the only complication reported in patients treated by gabapentin was drowsiness, but other uncommon side effects were nausea and dizziness.

CONCLUSION

This study showed that both gabapentin and topiramate reduce pain. Topiramate can also be a good alternative choice, if gabapentin has side effects for patients and it cannot be tolerated, topiramate can be a good replacement.

TRIAL REGISTRATION

The trial was registered at the Thai Registry of Clinical Trials (http://www.clinicaltrials.in.th) with the TCTR ID: TCTR20170615001.

FUNDING

This research has been financially supported by Research Council of Urmia University of Medical Sciences.

Topiramate Confers Neuroprotection Against Methylphenidate-Induced Neurodegeneration in Dentate Gyrus and CA1 Regions of Hippocampus via CREB/BDNF Pathway in Rats

Methylphenidate (MPH) abuse can cause serious neurological damages. The neuroprotective effects of topiramate (TPM) have been reported already, but its mechanism of action still remains unclear. The current study evaluates in vivo role of CREB/BDNF in TPM protection of the rat hippocampal cells from methylphenidate-induced apoptosis, oxidative stress, and inflammation. A total of 60 adult male rats were divided into six groups. Groups 1 and 2 received normal saline (0.7 ml/rat) and MPH (10 mg/kg) respectively for 14 days. Groups 3 and 4 were concurrently treated with MPH (10 mg/kg) and TPM 50 and 100 mg/kg respectively for 14 days. Groups 5 and 6 were treated with 50 and 100 mg/kg TPM only respectively. After drug administration, open field test (OFT) was used to investigate motor activity. The hippocampus was then isolated and the apoptotic, antiapoptotic, oxidative, antioxidant, and inflammatory factors were measured. Expression of the total and phosphorylated CREB and BDNF in gene and protein levels, and gene expression of Ak1, CaMK4, MAPK3, PKA, and c-Fos levels were also measured. MPH significantly decreased motor activity in OFT. TPM (50 and 100 mg/kg) decreased MPH-induced motor activity disturbance. Additionally, MPH significantly increased Bax protein level, CaMK4 gene expression, lipid peroxidation, catalase activity, mitochondrial GSH, IL-1β, and TNF-α levels in isolated hippocampal cells. Also CREB, in total and phosphorylated forms, BDNF and Bcl-2 protein levels, Ak1, MAPK3, PKA and c-Fos gene expression, superoxide dismutase, glutathione peroxidase, and glutathione reductase activities decreased significantly by MPH. TPM (50 and 100 mg/kg), both in the presence and absence of MPH, attenuated the effects of MPH. Immunohistochemistry data showed that TPM increased localization of the total and phosphorylated forms of CREB in dentate gyrus (DG) and CA1 areas of the hippocampus. It seems that TPM can be used as a neuroprotective agent against apoptosis, oxidative stress, and neuroinflammation induced by frequent use of MPH. This might be probably mediated by the CREB/BDNF and their upstream signaling pathways.

Current Ideas on the Treatment Of Diabetic Neuropathies

Diabetic neuropathies are common and their prevalence is rising with the growth in the global prevalence of type 2 diabetes. Several patterns of neuropathy have now been described, with diabetic sensorimotor polyneuropathy (DPN) being the most common. Autonomic neuropathy, entrapment neuropathies including carpal tunnel syndrome and ulnar neuropathy at the elbow pose additional burdens. DPN can be detected in over half of all diabetic subjects and approximately 20% of all patients with DPN also experience neuropathic pain, a complication with major impacts on quality of life. Currently, the only available treatments for DPN are optimal glucose control and pain management, whereas interventions, beyond optimizing hyperglycemic control, to address the underlying polyneuropathy are not available. Here we review current treatment options and new literature relating to DPN, with an emphasis on novel and emerging treatments.

Pharmacologic Management of Upper Extremity Chronic Nerve Pain

The treatment of pain is a complex process that requires a team approach. This article provides an overview of the pharmaceutical treatments available. It gives providers treating upper extremity disorders more tools to treat their patients with chronic pain. Another goal is to improve hand providers' understanding of the medications their pain colleagues prescribe in shared patients. Pharmaceuticals are an important component in the treatment of chronic pain and opioids are often not a good solution. Knowing what other medications are available can improve the care for these challenging patients.

Burning through the pain: treatments for diabetic neuropathy

The rise in the global burden of diabetes is spurring an increase in the prevalence of its complications. Diabetic peripheral neuropathy (DPN) is a common and devastating complication of diabetes, with multiple clinical manifestations. The most common is a symmetrical length-dependent dysfunction and damage of peripheral nerves. The management of DPN rests on three tenets: intensive glycaemic control, even though the evidence of benefit is questionable in people with type 2 diabetes; pathogenetic therapies; and symptomatic treatment. A number of pathogenetic treatments have been evaluated in phase III clinical trials, including α-lipoic acid (stems reactive oxygen species formation), benfotiamine (prevents vascular damage) and aldose-reductase inhibitors (reduce flux through the polyol pathway), protein kinase C inhibitors (prevent hyperglycaemia-induced activation of protein kinase C), nerve growth factors (stimulate nerve regeneration) and Actovegin® (improves tissue glucose and oxygen uptake). However, none have gained US Food and Drug Administration or European Medicines Agency (EMA) approval, questioning the validity of current trial designs and the endpoints deployed to define efficacy. For painful diabetic neuropathy, clinical guidelines recommend: atypical analgesics for pain relief, including duloxetine and amitriptyline; the γ-aminobutyric acid analogues gabapentin and pregabalin; opioids, including Tapentadol; and topical agents such as lidocaine and capsaicin. No single effective treatment exists for painful DPN, highlighting a growing need for studies to evaluate more potent and targeted drugs, as well as combinations. A number of novel potential candidates, including erythropoietin analogues and angiotensin II type 2 receptor anatagonists are currently being evaluated in phase II clinical trials.

Treating Diabetic Neuropathy: Present Strategies and Emerging Solutions

Diabetic peripheral neuropathies (DPN) are a heterogeneous group of disorders caused by neuronal dysfunction in patients with diabetes. They have differing clinical courses, distributions, fiber involvement (large or small), and pathophysiology. These complications are associated with increased morbidity, distress, and healthcare costs. Approximately 50% of patients with diabetes develop peripheral neuropathy, and the projected rise in the global burden of diabetes is spurring an increase in neuropathy. Distal symmetrical polyneuropathy (DSPN) with painful diabetic neuropathy, occurring in around 20% of diabetes patients, and diabetic autonomic neuropathy (DAN) are the most common manifestations of DPN. Optimal glucose control represents the only broadly accepted therapeutic option though evidence of its benefit in type 2 diabetes is unclear. A number of symptomatic treatments are recommended in clinical guidelines for the management of painful DPN, including antidepressants such as amitriptyline and duloxetine, the γ-aminobutyric acid analogues gabapentin and pregabalin, opioids, and topical agents such as capsaicin. However, monotherapy is frequently not effective in achieving complete resolution of pain in DPN. There is a growing need for head-to-head studies of different single-drug and combination pharmacotherapies. Due to the ubiquity of autonomic innervation in the body, DAN causes a plethora of symptoms and signs affecting cardiovascular, urogenital, gastrointestinal, pupillomotor, thermoregulatory, and sudomotor systems. The current treatment of DAN is largely symptomatic, and does not correct the underlying autonomic nerve deficit. A number of novel potential candidates, including erythropoietin analogues, angiotensin II receptor type 2 antagonists, and sodium channel blockers are currently being evaluated in phase II clinical trials.

Improvement in chronic low back pain in an obese patient with topiramate use

The objective of this study was to demonstrate efficacy, benefit, and potential use of topiramate in treating obese patients with chronic low back pain. This is a case report from an outpatient academic pain multidisciplinary clinical center. The patient was a 30-year-old morbidly obese (body mass index [BMI]: 61.4 kg/m(2)) female suffering from chronic low back pain. With a known association between obesity and chronic low back pain, and a possible role of topiramate in treating both simultaneously, the patient was started on a therapeutic trial of topiramate. Over a period of a 12-week topiramate therapy, the patient experienced clinically meaningful and significant weight loss as well as improvement in her chronic low back pain and functionality. With more substantial evidence, pain physicians may start considering using topiramate in the multimodal management of obesity-related chronic low back pain based on their thoughtful consideration of the drug's efficacy and side effects and the patient's comorbidities and preferences.

Critical appraisal of international guidelines for the management of diabetic neuropathy: is there global agreement in the internet era?

Purpose. The management of diabetic neuropathy (DN) can be challenging. There exist many guidelines for DN management, but the quality of these guidelines has not been systematically evaluated or compared. The objective of our study was to assess the quality of these guidelines as a step toward their future optimization, the development of international guidelines, and, ultimately, the improvement of the care process. Methods. Relevant data were selected to identify international guidelines. The Appraisal of Guidelines for Research and Evaluation II (AGREE II) tool was used to evaluate the quality of the selected guidelines. In addition, the reviewers summarized and compared all of the recommendations from the included guidelines for DN's management. Results. Thirteen guidelines were included after the selection process. According to AGREE II, few guidelines scored well for all three aspects of DN management. Detailed comparisons revealed that these guidelines provide inconsistent recommendations, making it difficult for diabetes clinicians to choose appropriate guideline. Conclusions. The quality of most guidelines for the management of DN should be improved. Further studies should concentrate on developing internationally accepted and evidence-based guidelines that could be used for clinical decision making to improve patient care.

Treatment of painful diabetic neuropathy

Painful diabetic neuropathy (PDN) is a debilitating consequence of diabetes that may be present in as many as one in five patients with diabetes. The objective assessment of PDN is difficult, making it challenging to diagnose and assess in both clinical practice and clinical trials. No single treatment exists to prevent or reverse neuropathic changes or to provide total pain relief. Treatment of PDN is based on three major approaches: intensive glycaemic control and risk factor management, treatments based on pathogenetic mechanisms, and symptomatic pain management. Clinical guidelines recommend pain relief in PDN through the use of antidepressants such as amitriptyline and duloxetine, the γ-aminobutyric acid analogues gabapentin and pregabalin, opioids and topical agents such as capsaicin. Of these medications, duloxetine and pregabalin were approved by the US Food and Drug Administration (FDA) in 2004 and tapentadol extended release was approved in 2012 for the treatment of PDN. Proposed pathogenetic treatments include α-lipoic acid (stems reactive oxygen species formation), benfotiamine (prevents vascular damage in diabetes) and aldose-reductase inhibitors (reduces flux through the polyol pathway). There is a growing need for studies to evaluate the most potent drugs or combinations for the management of PDN to maximize pain relief and improve quality of life. A number of agents are potential candidates for future use in PDN therapy, including Nav 1.7 antagonists, N-type calcium channel blockers, NGF antibodies and angiotensin II type 2 receptor antagonists.

Evaluating the Phase II drugs currently under investigation for diabetic neuropathy

Introduction: The worldwide number of patients suffering from diabetes mellitus (DM) is projected to approach 552 million by the year 2030. As diabetic neuropathy (DN) is present in 8% of new diabetic patients at the time of diagnosis and occurs in ∼ 50% of all patients with established DM, the number of patients who will develop painful DN will also increase. The suboptimal efficacies of currently approved drugs have prompted investigators to develop new therapeutic agents for the management of painful DN. Areas covered: In this review, the authors present and elucidate the current status of drugs under investigation for the treatment of painful DN. A short synopsis of currently approved drugs is also given. Literature information and data analysis were retrieved from PubMed, the American Diabetes and Neurological Associations Websites and ClinicalTrials.gov. The keywords used in the search included: DM, DN, painful diabetic neuropathy. Expert opinion: In addition to treating the pain associated with DN, the actual causes of the disease should also be targeted for improved management. It is hoped that drugs which improve vascular blood flow, induce neural regeneration, reduce hyperglycemia, oxidative stress and inflammation can be more effective for the overall treatment of painful DN.

Effect of topiramate on hippocampus-dependent spatial memory in rats

BACKGROUND

Topiramate, a new generation antiepileptic agent with a complex mechanism of action, has a broad pharmacological profile which includes a neuroprotective effect. It has been proven to be efficacious in treating alcohol dependence through a previously confirmed association with memory processes.

METHODS

Topiramate was administered in single doses of 120 and 40 mg/kg and multiple doses of 60 mg/kg for 12 days. Its influence on the spatial memory of rats was evaluated using the Morris water maze test. The time needed to localize the platform, the distance travelled and time spent in the platform zone were recorded.

RESULTS

Single doses of topiramate induce deterioration of spatial memory, with high doses having more pronounced and longer lasting effects. Multiple administration of a medial dose does not significantly affect the learning process.

CONCLUSIONS

The influence of topiramate on the hippocampus-related memory processes may play a key role in its "anti-alcohol" effect.

New approaches to the pharmacotherapy of neuropathic pain

Pain is one of the most debilitating symptoms that presents with neuropathy. Neuropathic pain syndrome is a challenge to treat and, even with appropriate evidence-based treatment, only a 40% reduction of symptoms can be achieved in approximately half of patients. Furthermore, efficient doses are often difficult to obtain because of adverse effects. These observations underline that the treatment of neuropathic pain is still an unmet medical need. New approaches to the pharmacotherapy of neuropathy embrace different lines of work, including a fundamental mechanism-based approach, a clinical mechanism-based approach and an evidence-based approach. Moreover, interindividual variability in drug response, and genetic polymorphism in particular, is an emerging aspect to consider. Together with reviewing recent evidence-based guidelines as well as briefly discussing genetic polymorphisms that may influence the individual responses to treatments, this article will focus on what a mechanism-based approach is bringing to the clinical setting, on the perspective in fundamental research and on the difficulty of bridging the gap between fundamental notions and positive clinical outcomes.

Therapy for diabetic neuropathy: an overview

Neuropathy is a highly prevalent complication of diabetes that is only likely to increase as the diabetic epidemic continues. Unfortunately, the only disease-modifying treatment is to address the underlying diabetes with enhanced glucose control. In patients with type 1 diabetes, improved glycemic control dramatically reduces the incidence of neuropathy. In contrast, in patients with type 2 diabetes, better glucose control has only a marginal effect on the prevention of neuropathy. However, recognition and treatment of neuropathic pain is also important. An ever expanding number of randomized, controlled clinical trials support multiple medications for the reduction of pain. This includes medications such as calcium channel agonists, tricyclic antidepressants, and selective serotonin/norepinephrine reuptake inhibitors. However, the precise order and combination of these medications remains unclear. Furthermore, several new promising medications are being developed. Overall, the cornerstones of the treatment of diabetic neuropathy are improved glycemic control and initiation of a neuropathic pain medication with high levels of evidence to support its use when pain is present.

Diabetic neuropathy

Diabetic neuropathy (DN) is the most common and troublesome complication of diabetes mellitus, leading to the greatest morbidity and mortality and resulting in a huge economic burden for diabetes care. The clinical assessment of diabetic peripheral neuropathy and its treatment options are multifactorial. Patients with DN should be screened for autonomic neuropathy, as there is a high degree of coexistence of the two complications. A review of the clinical assessment and treatment algorithms for diabetic neuropathy, painful neuropathy, and autonomic dysfunction is provided.

Topiramate for neuropathic pain and fibromyalgia in adults

BACKGROUND

Topiramate is an antiepileptic drug with multiple possible mechanisms of action. Antiepileptic drugs are widely used to treat chronic neuropathic pain (pain due to nerve damage) and fibromyalgia, and many guidelines recommend them.

OBJECTIVES

To assess the analgesic efficacy and associated adverse events of topiramate for chronic neuropathic pain and fibromyalgia in adults (aged 18 years and above).

SEARCH METHODS

On 8 May 2013, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, and EMBASE. We reviewed the bibliographies of all randomised trials identified and review articles, and also searched two clinical trial databases, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform, to identify additional published or unpublished data.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) with double-blind assessment of participant outcomes following two weeks of treatment or longer (though the emphasis of the review was on studies of eight weeks or longer) that used a placebo or active comparator.

DATA COLLECTION AND ANALYSIS

We extracted efficacy and adverse event data, and two study authors examined issues of study quality independently. We performed analysis using two tiers of evidence. The first tier used data where studies reported the outcome of at least 50% pain reduction from baseline, lasted at least eight weeks, had a parallel group design, included 200 or more participants in the comparison, and reported an intention-to-treat analysis. First tier studies did not use last-observation-carried-forward (LOCF) or other imputation methods for dropouts. The second tier used data that failed to meet this standard; second tier results were therefore subject to potential bias.

MAIN RESULTS

We included four studies with 1684 participants. Three parallel-group placebo comparisons were in painful diabetic neuropathy (1643 participants), and one cross-over study with diphenhydramine as an active placebo (41 participants) was in lumbar radiculopathy. Doses of topiramate were titrated up to 200 mg/day or 400 mg/day. All studies had one or more sources of potential major bias, as they either used LOCF imputation or were of small size.No study provided first tier evidence for an efficacy outcome. There was no convincing evidence for efficacy of topiramate at 200 to 400 mg/day over placebo.Eighty-two per cent of participants taking topiramate 200 to 400 mg/day experienced at least one adverse event, as did 71% with placebo, and the number needed to treat for an additional harmful effect (NNTH) was 8.6 (95% confidence interval (CI) 4.9 to 35). There was no difference in serious adverse events recorded (6.6% versus 7.5%). Adverse event withdrawals with 400 mg daily were much more common with topiramate (27%) than with placebo (8%), with an NNTH of 5.4 (95% CI 4.3 to 7.1). Lack of efficacy withdrawal was less frequent with topiramate (12%) than placebo (18%). Weight loss was a common event in most studies. No deaths attributable to treatment were reported.

AUTHORS' CONCLUSIONS

Topiramate is without evidence of efficacy in diabetic neuropathic pain, the only neuropathic condition in which it has been adequately tested. The data we have includes the likelihood of major bias due to LOCF imputation, where adverse event withdrawals are much higher with active treatment than placebo control. Despite the strong potential for bias, no difference in efficacy between topiramate and placebo was apparent.

Pharmacologic management of diabetic peripheral neuropathic pain

INTRODUCTION

Diabetic peripheral neuropathic pain (DPNP) is a debilitating and distressing complication that occurs in patients with diabetes mellitus. This article provides an overview of diabetic peripheral neuropathy focusing on DPNP.

AREAS COVERED

This article reviews the diagnosis, pathogenesis, prevention and treatment of diabetic neuropathy and neuropathic pain. A comprehensive and systematic Medline search of the published literature for treatment of diabetic peripheral neuropathy was done from 1965 to December 2012. Studies not in English language were excluded.

EXPERT OPINION

Neuropathic pain is difficult to treat, and patients rarely experience complete pain relief. Despite several pharmacological agents being used in the treatment of DPNP, only duloxetine and pregabalin have evidence-based support for controlling DPNP.

Anti-epileptic drugs for pain #271

TCAs, SNRIs, and the AEDs gabapentin and pregabalin are the best adjuvant analgesics for neuropathic pain. For patients who are intolerant to or who experience pain unresponsive to the above medications, one can consider therapy with carbamazepine, oxcarbazepine, valproic acid, topiramate, or lacosamide. However, as these agents are associated with more side effects and lower rates of efficacy, expert consultation is strongly recommended.

Systematic review and meta-analysis of pharmacological therapies for painful diabetic peripheral neuropathy

BACKGROUND

Painful diabetic peripheral neuropathy (pDPN) is prevalent among persons with diabetes and increases over time. Published guidelines recommend a number of medications to treat this condition providing clinicians with a variety of treatment options. This study provides a comprehensive systematic review and meta-analysis of published pharmacologic therapies for pDPN.

METHODS

The published literature was systematically searched to identify randomized, controlled trials of all available pharmacologic treatments for pDPN (recommended or nonrecommended) reporting predefined efficacy and safety outcomes. Bayesian fixed-effect mixed treatment comparison methods were used to assess relative therapeutic efficacy and harms.

RESULTS

Data from 58 studies including 29 interventions and 11,883 patients were analyzed. Pain reduction over that of placebo on the 11-point numeric rating scale ranged from -3.29 for sodium valproate (95% credible interval [CrI] = [-4.21, -2.36]) to 1.67 for Sativex (-0.47, 0.60). Estimates for most treatments were clustered between 0 and -1.5 and were associated with more study data and smaller CrIs. Pregabalin (≥ 300 mg/day) was the most effective on the 100-point visual analog scale (-21.88; [-27.06, -16.68]); topiramate was the least (-3.09; [-3.99, -2.18]). Relative risks (RRs) of 30% pain reduction ranged from 0.78 (Sativex) to 1.84 (lidocaine 5% plaster). Analysis of the RR ratio of these 2 treatments reveals marginal significance for Sativex (3.27; [1.07, 9.81]), indicating the best treatment is only slightly better than the worst. Relative risks of 50% pain reduction ranged from 0.98 (0.56, 1.52) (amitriptyline) to 2.25 (1.51, 3.00) (alpha-lipoic acid). RR ratio for these treatments was not statistically different (3.39; [0.88, 3.34]). Fluoxetine had the lowest risk of adverse events (0.94; [0.62, 1.23]); oxycodone had the highest (1.55; [1.45, 1.64]). Discontinuation RRs were clustered around 0.8 to 1.5, with those on the extreme having greater uncertainty.

CONCLUSIONS

Selecting an appropriate pDPN therapy is key given the large number of available treatments. Comparative results revealed relative equivalence among many of the studied interventions having the largest overall sample sizes and highlight the importance of standardization of methods to effectively assess pain.

Treatment of painful peripheral neuropathy

Neuropathic pain management is an important aspect in the management of painful peripheral neuropathy. Anticonvulsants and antidepressants have been studied extensively and are often used as first-line agents in the management of neuropathic pain. In this article, data from multiple randomized controlled studies on painful peripheral neuropathies are summarized to guide physicians in treating neuropathic pain. Treatment is a challenge given the diverse mechanisms of pain and variable responses in individuals. However, most patients derive pain relief from a well-chosen monotherapy or well-designed polypharmacy that combines agents with different mechanisms of action.

Painful diabetic polyneuropathy: approach to diagnosis and management

OBJECTIVES

To provide a current overview of the diagnostic work-up and management of painful diabetic polyneuropathy (PDPN).

METHODS

A review covering the literature from 2004 to 2011, which describes the tools designed to diagnose neuropathic pain and assess its severity, including self-administered questionnaires, validated laboratory tests and simple handheld screening devices, and the evidence-based therapeutic approaches to PDPN.

RESULTS

The clinical aspects, pathogenesis, and comorbidities of PDPN, as well as its impact on health related quality of life (HR-QoL), are the main drivers for the management of patients with suspected PDPN. PDPN treatment consists first of all in improving glycemic control and lifestyle intervention. A number of symptomatic pharmacological agents are available for pain control: tricyclic antidepressants and selective serotonin norepinephrine reuptake inhibitors (venlafaxine and duloxetine), α2-delta ligands (gabapentin and pregabalin), opioid analgesics (tramadol and oxycodone), and agents for topical use, such as lidocaine patch and capsaicin cream. With the exception of transcutaneous electrical nerve stimulation, physical treatment is not supported by adequate evidence.

DISCUSSION

As efficacy and tolerability of current therapy for PDPN are not ideal, the need for a better approach in management further exists. Novel compounds should be developed for the treatment of PDPN.

Guidelines in the management of diabetic nerve pain: clinical utility of pregabalin

Diabetic peripheral neuropathy is a common complication of diabetes. It presents as a variety of syndromes for which there is no universally accepted unique classification. Sensorimotor polyneuropathy is the most common type, affecting about 30% of diabetic patients in hospital care and 25% of those in the community. Pain is the reason for 40% of patient visits in a primary care setting, and about 20% of these have had pain for greater than 6 months. Chronic pain may be nociceptive, which occurs as a result of disease or damage to tissue with no abnormality in the nervous system. In contrast, neuropathic pain is defined as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system." Persistent neuropathic pain interferes significantly with quality of life, impairing sleep and recreation; it also significantly impacts emotional well-being, and is associated with depression, anxiety, and noncompliance with treatment. Painful diabetic peripheral neuropathy is a difficult-to-manage clinical problem, and patients with this condition are more apt to seek medical attention than those with other types of diabetic neuropathy. Early recognition of psychological problems is critical to the management of pain, and physicians need to go beyond the management of pain per se if they are to achieve success. This evidence-based review of the assessment of the patient with pain in diabetes addresses the state-of-the-art management of pain, recognizing all the conditions that produce pain in diabetes and the evidence in support of a variety of treatments currently available. A search of the full Medline database for the last 10 years was conducted in August 2012 using the terms painful diabetic peripheral neuropathy, painful diabetic peripheral polyneuropathy, painful diabetic neuropathy and pain in diabetes. In addition, recent reviews addressing this issue were adopted as necessary. In particular, reports from the American Academy of Neurology and the Toronto Consensus Panel on Diabetic Neuropathy were included. Unfortunately, the results of evidence-based studies do not necessarily take into account the presence of comorbidities, the cost of treatment, or the role of third-party payers in decision-making. Thus, this review attempts to give a more balanced view of the management of pain in the diabetic patient with neuropathy and in particular the role of pregabalin.

Mechanisms of neuropathic pain

Neuropathic pain is a disease of global burden. Its symptoms include spontaneous and stimulus-evoked painful sensations. Several maladaptive mechanisms underlying these symptoms have been elucidated in recent years: peripheral sensitization of nociception, abnormal excitability of afferent neurons, central sensitization comprising pronociceptive facilitation, disinhibition of nociception and central reorganization processes, and sympathetically maintained pain. This review aims to illustrate these pathophysiological principles, focussing on molecular and neurophysiological findings. Finally therapeutic options based on these findings are discussed.