A comparative evaluation of amitriptyline and duloxetine in painful diabetic neuropathy: a randomized, double-blind, cross-over clinical trial

Effectiveness of Duloxetine versus Other Therapeutic Modalities in Patients with Diabetic Neuropathic Pain: A Systematic Review and Meta-Analysis

Objectives: Diabetic peripheral neuropathy (DPN) is a chronic complication of diabetes mellitus (DM) with symptoms like intense pain and impaired quality of life. This condition has no treatment; instead, the pain is managed with various antidepressants, including duloxetine. The aim of this study is to analyze the evidence on the efficacy of duloxetine in the management of DPN. Methods: A systematic search in different databases was conducted using the keywords "diabetic neuropathy", "duloxetine therapy", "neuropathic pain", and "Diabetes Mellitus". Finally, eight studies were included in this meta-analysis. Results: All articles comparing duloxetine at different doses vs. a placebo reported significant differences in favor of duloxetine on pain scales like 24 h Average Pain Severity (standardized mean difference [SMD] = -1.06, confidence interval [CI] = -1.09 to -1.03, and p < 0.00001) and BPI Severity (SMD = -0.70, CI = -0.72 to -0.68, and p < 0.00001), among others. A total of 75% of the meta-analyses of studies comparing duloxetine at different doses showed a tendency in favor of the 120 mg/d dose. There were significant differences in favor of duloxetine when compared to routine care on the Euro Quality of Life (SMD = -0.04, CI = -0.04 to -0.03, and p < 0.00001) and SF-36 Survey (SMD = -5.86, CI = -6.28 to -5.44, and p < 0.00001) scales. There were no significant differences on the visual analog scale (VAS) when comparing duloxetine and gabapentin. Conclusions: Duloxetine appears to be effective in the management of DPN in different pain, symptom improvement, and quality of life scales.

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

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

Novel drugs affecting diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) poses a significant threat, affecting half of the global diabetic population and leading to severe complications, including pain, impaired mobility, and potential amputation. The delayed manifestation of diabetic neuropathy (DN) makes early diagnosis challenging, contributing to its debilitating impact on individuals with diabetes mellitus (DM). This review examines the multifaceted nature of DPN, focusing on the intricate interplay between oxidative stress, metabolic pathways, and the resulting neuronal damage. It delves into the challenges of diagnosing DN, emphasizing the critical role played by hyperglycemia in triggering these cascading effects. Furthermore, the study explores the limitations of current neuropathic pain drugs, prompting an investigation into a myriad of pharmaceutical agents tested in both human and animal trials over the past decade. The methodology scrutinizes these agents for their potential to provide symptomatic relief for DPN. The investigation reveals promising results from various pharmaceutical agents tested for DPN relief, showcasing their efficacy in ameliorating symptoms. However, a notable gap persists in addressing the underlying problem of DPN. The results underscore the complexity of DPN and the challenges in developing therapies that go beyond symptomatic relief. Despite advancements in treating DPN symptoms, there remains a scarcity of options addressing the underlying problem. This review consolidates the state-of-the-art drugs designed to combat DPN, highlighting their efficacy in alleviating symptoms. Additionally, it emphasizes the need for a deeper understanding of the diverse processes and pathways involved in DPN pathogenesis.

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

BACKGROUND

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

METHODS

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

RESULT

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

CONCLUSION

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

Diabetic Neuropathy: An Overview of Molecular Pathways and Protective Mechanisms of Phytobioactives

Diabetic neuropathy (DN) is a common and debilitating complication of diabetes mellitus that affects the peripheral nerves and causes pain, numbness, and impaired function. The pathogenesis of DN involves multiple molecular mechanisms, such as oxidative stress, inflammation, and pathways of advanced glycation end products, polyol, hexosamine, and protein kinase C. Phytochemicals are natural compounds derived from plants that have various biological activities and therapeutic potential. Flavonoids, terpenes, alkaloids, stilbenes, and tannins are some of the phytochemicals that have been identified as having protective potential for diabetic neuropathy. These compounds can modulate various cellular pathways involved in the development and progression of neuropathy, including reducing oxidative stress and inflammation and promoting nerve growth and repair. In this review, the current evidence on the effects of phytochemicals on DN by focusing on five major classes, flavonoids, terpenes, alkaloids, stilbenes, and tannins, are summarized. This compilation also discusses the possible molecular targets of numerous pathways of DN that these phytochemicals modulate. These phytochemicals may offer a promising alternative or complementary approach to conventional drugs for DN management by modulating multiple pathological pathways and restoring nerve function.

Real world outcomes with spinal cord stimulation

High frequency spinal cord stimulation (SCS) is a safe and effective treatment option for refractory painful diabetic neuropathy and should be considered for use early in the course of the disease. Raising awareness of this minimally invasive treatment option among physician networks is of major importance.

Oral proniosomal amitriptyline and liraglutide for management of diabetic neuropathy: Exceptional control over hyperglycemia and neuropathic pain

Exploitation of nanocarriers provides a compartment for enclosing drugs to protect them from degradation and potentiate their therapeutic efficiency. In the current study, amitriptyline- and liraglutide-loaded proniosomes were constructed for management of diabetic neuropathy, a serious complication associated with diabetes, that triggers spontaneous pain in patients and results in impaired quality of life. The developed therapeutic proniosomes were extensively characterized via dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and Fourier transform-infrared spectroscopy. High entrapment efficiency could be attained for both drugs in the proniosomes, and the reconstituted amitriptyline- and liraglutide-loaded niosomes possessed spherical morphology and particle sizes of 585.3 nm and 864.4 nm, respectively. In a diabetic neuropathy rat model, oral administration of the developed amitriptyline- and liraglutide-loaded proniosomes significantly controlled blood glucose levels, reduced neuropathic pain, oxidative stress and inflammatory markers, and improved histological structure of the sciatic nerve as compared to the oral and subcutaneous administration of amitriptyline and liraglutide, respectively. Loading of the tricyclic antidepressant amitriptyline and the antidiabetic peptide liraglutide into proniosomes resulted in exceptional control over hyperglycemia and neuropathic pain, and thus could provide an auspicious delivery system for management of neuropathic pain and control of blood glucose levels.

Issues and challenges in diabetic neuropathy management: A narrative review

Diabetic neuropathy (DN) is a devastating disorder with an increasing prevalence globally. This epidemic can pose a critical burden on individuals and com-munities, subsequently affecting the productivity and economic output of a country. With more people living a sedentary lifestyle, the incidence of DN is escalating worldwide. Many researchers have relentlessly worked on ways to combat this devastating disease. Their efforts have given rise to a number of commercially available therapies that can alleviate the symptoms of DN. Unfortunately, most of these therapies are only partially effective. Worse still, some are associated with unfavorable side effects. This narrative review aims to highlight current issues and challenges in the management of DN, especially from the perspective of molecular mechanisms that lead to its progression, with the hope of providing future direction in the management of DN. To improve the approaches to diabetic management, the suggested resolutions in the literature are also discussed in this review. This review will provide an in-depth understanding of the causative mechanisms of DN, apart from the insights to improve the quality and strategic approaches to DN management.

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

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Optimal pharmacotherapy pathway in adults with diabetic peripheral neuropathic pain: the OPTION-DM RCT

BACKGROUND

The mainstay of treatment for diabetic peripheral neuropathic pain is pharmacotherapy, but the current National Institute for Health and Care Excellence guideline is not based on robust evidence, as the treatments and their combinations have not been directly compared.

OBJECTIVES

To determine the most clinically beneficial, cost-effective and tolerated treatment pathway for diabetic peripheral neuropathic pain.

DESIGN

A randomised crossover trial with health economic analysis.

SETTING

Twenty-one secondary care centres in the UK.

PARTICIPANTS

Adults with diabetic peripheral neuropathic pain with a 7-day average self-rated pain score of ≥ 4 points (Numeric Rating Scale 0-10).

INTERVENTIONS

Participants were randomised to three commonly used treatment pathways: (1) amitriptyline supplemented with pregabalin, (2) duloxetine supplemented with pregabalin and (3) pregabalin supplemented with amitriptyline. Participants and research teams were blinded to treatment allocation, using over-encapsulated capsules and matching placebos. Site pharmacists were unblinded.

OUTCOMES

The primary outcome was the difference in 7-day average 24-hour Numeric Rating Scale score between pathways, measured during the final week of each pathway. Secondary end points included 7-day average daily Numeric Rating Scale pain score at week 6 between monotherapies, quality of life (Short Form questionnaire-36 items), Hospital Anxiety and Depression Scale score, the proportion of patients achieving 30% and 50% pain reduction, Brief Pain Inventory - Modified Short Form items scores, Insomnia Severity Index score, Neuropathic Pain Symptom Inventory score, tolerability (scale 0-10), Patient Global Impression of Change score at week 16 and patients' preferred treatment pathway at week 50. Adverse events and serious adverse events were recorded. A within-trial cost-utility analysis was carried out to compare treatment pathways using incremental costs per quality-adjusted life-years from an NHS and social care perspective.

RESULTS

A total of 140 participants were randomised from 13 UK centres, 130 of whom were included in the analyses. Pain score at week 16 was similar between the arms, with a mean difference of -0.1 points (98.3% confidence interval -0.5 to 0.3 points) for duloxetine supplemented with pregabalin compared with amitriptyline supplemented with pregabalin, a mean difference of -0.1 points (98.3% confidence interval -0.5 to 0.3 points) for pregabalin supplemented with amitriptyline compared with amitriptyline supplemented with pregabalin and a mean difference of 0.0 points (98.3% confidence interval -0.4 to 0.4 points) for pregabalin supplemented with amitriptyline compared with duloxetine supplemented with pregabalin. Results for tolerability, discontinuation and quality of life were similar. The adverse events were predictable for each drug. Combination therapy (weeks 6-16) was associated with a further reduction in Numeric Rating Scale pain score (mean 1.0 points, 98.3% confidence interval 0.6 to 1.3 points) compared with those who remained on monotherapy (mean 0.2 points, 98.3% confidence interval -0.1 to 0.5 points). The pregabalin supplemented with amitriptyline pathway had the fewest monotherapy discontinuations due to treatment-emergent adverse events and was most commonly preferred (most commonly preferred by participants: amitriptyline supplemented with pregabalin, 24%; duloxetine supplemented with pregabalin, 33%; pregabalin supplemented with amitriptyline, 43%; p = 0.26). No single pathway was superior in cost-effectiveness. The incremental gains in quality-adjusted life-years were small for each pathway comparison [amitriptyline supplemented with pregabalin compared with duloxetine supplemented with pregabalin -0.002 (95% confidence interval -0.011 to 0.007) quality-adjusted life-years, amitriptyline supplemented with pregabalin compared with pregabalin supplemented with amitriptyline -0.006 (95% confidence interval -0.002 to 0.014) quality-adjusted life-years and duloxetine supplemented with pregabalin compared with pregabalin supplemented with amitriptyline 0.007 (95% confidence interval 0.0002 to 0.015) quality-adjusted life-years] and incremental costs over 16 weeks were similar [amitriptyline supplemented with pregabalin compared with duloxetine supplemented with pregabalin -£113 (95% confidence interval -£381 to £90), amitriptyline supplemented with pregabalin compared with pregabalin supplemented with amitriptyline £155 (95% confidence interval -£37 to £625) and duloxetine supplemented with pregabalin compared with pregabalin supplemented with amitriptyline £141 (95% confidence interval -£13 to £398)].

LIMITATIONS

Although there was no placebo arm, there is strong evidence for the use of each study medication from randomised placebo-controlled trials. The addition of a placebo arm would have increased the duration of this already long and demanding trial and it was not felt to be ethically justifiable.

FUTURE WORK

Future research should explore (1) variations in diabetic peripheral neuropathic pain management at the practice level, (2) how OPTION-DM (Optimal Pathway for TreatIng neurOpathic paiN in Diabetes Mellitus) trial findings can be best implemented, (3) why some patients respond to a particular drug and others do not and (4) what options there are for further treatments for those patients on combination treatment with inadequate pain relief.

CONCLUSIONS

The three treatment pathways appear to give comparable patient outcomes at similar costs, suggesting that the optimal treatment may depend on patients' preference in terms of side effects.

TRIAL REGISTRATION

The trial is registered as ISRCTN17545443 and EudraCT 2016-003146-89.

FUNDING

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme, and will be published in full in Health Technology Assessment; Vol. 26, No. 39. See the NIHR Journals Library website for further project information.

Comparison of amitriptyline supplemented with pregabalin, pregabalin supplemented with amitriptyline, and duloxetine supplemented with pregabalin for the treatment of diabetic peripheral neuropathic pain (OPTION-DM): a multicentre, double-blind, randomised crossover trial

BACKGROUND

Diabetic peripheral neuropathic pain (DPNP) is common and often distressing. Most guidelines recommend amitriptyline, duloxetine, pregabalin, or gabapentin as initial analgesic treatment for DPNP, but there is little comparative evidence on which one is best or whether they should be combined. We aimed to assess the efficacy and tolerability of different combinations of first-line drugs for treatment of DPNP.

METHODS

OPTION-DM was a multicentre, randomised, double-blind, crossover trial in patients with DPNP with mean daily pain numerical rating scale (NRS) of 4 or higher (scale is 0-10) from 13 UK centres. Participants were randomly assigned (1:1:1:1:1:1), with a predetermined randomisation schedule stratified by site using permuted blocks of size six or 12, to receive one of six ordered sequences of the three treatment pathways: amitriptyline supplemented with pregabalin (A-P), pregabalin supplemented with amitriptyline (P-A), and duloxetine supplemented with pregabalin (D-P), each pathway lasting 16 weeks. Monotherapy was given for 6 weeks and was supplemented with the combination medication if there was suboptimal pain relief (NRS >3), reflecting current clinical practice. Both treatments were titrated towards maximum tolerated dose (75 mg per day for amitriptyline, 120 mg per day for duloxetine, and 600 mg per day for pregabalin). The primary outcome was the difference in 7-day average daily pain during the final week of each pathway. This trial is registered with ISRCTN, ISRCTN17545443.

FINDINGS

Between Nov 14, 2017, and July 29, 2019, 252 patients were screened, 140 patients were randomly assigned, and 130 started a treatment pathway (with 84 completing at least two pathways) and were analysed for the primary outcome. The 7-day average NRS scores at week 16 decreased from a mean 6·6 (SD 1·5) at baseline to 3·3 (1·8) at week 16 in all three pathways. The mean difference was -0·1 (98·3% CI -0·5 to 0·3) for D-P versus A-P, -0·1 (-0·5 to 0·3) for P-A versus A-P, and 0·0 (-0·4 to 0·4) for P-A versus D-P, and thus not significant. Mean NRS reduction in patients on combination therapy was greater than in those who remained on monotherapy (1·0 [SD 1·3] vs 0·2 [1·5]). Adverse events were predictable for the monotherapies: we observed a significant increase in dizziness in the P-A pathway, nausea in the D-P pathway, and dry mouth in the A-P pathway.

INTERPRETATION

To our knowledge, this was the largest and longest ever, head-to-head, crossover neuropathic pain trial. We showed that all three treatment pathways and monotherapies had similar analgesic efficacy. Combination treatment was well tolerated and led to improved pain relief in patients with suboptimal pain control with a monotherapy.

FUNDING

National Institute for Health Research (NIHR) Health Technology Assessment programme.

Prevention and Management Strategies for Diabetic Neuropathy

Diabetic neuropathy (DN) is a common complication of diabetes that is becoming an increasing concern as the prevalence of diabetes rapidly rises. There are several types of DN, but the most prevalent and studied type is distal symmetrical polyneuropathy, which is the focus of this review and is simply referred to as DN. It can lead to a wide range of sensorimotor and psychosocial symptoms and is a major risk factor for diabetic foot ulceration and Charcot neuropathic osteoarthropathy, which are associated with high rates of lower limb amputation and mortality. The prevention and management of DN are thus critical, and clinical guidelines recommend several strategies for these based on the best available evidence. This article aims to provide a narrative review of DN prevention and management strategies by discussing these guidelines and the evidence that supports them. First, the epidemiology and diverse clinical manifestations of DN are summarized. Then, prevention strategies such as glycemic control, lifestyle modifications and footcare are discussed, as well as the importance of early diagnosis. Finally, neuropathic pain management strategies and promising novel therapies under investigation such as neuromodulation devices and nutraceuticals are reviewed.

An overview of painful diabetic peripheral neuropathy: Diagnosis and treatment advancements

Diabetes mellitus remains a public health problem, affecting 422 million people worldwide. Currently, there is no consensus around treating painful diabetic peripheral neuropathy in a step-wise manner. Among the non-pharmacological interventions, neuromodulation has become a promising alternative. Over the past decade, significant clinical trials have paved the way for prompt inclusion of high-frequency spinal cord stimulation within the painful diabetic peripheral neuropathy treatment algorithm. This article aims to provide an updated evidence-based approach for the management of painful diabetic peripheral neuropathy.

Isolation of Thymol from Trachyspermum ammi Fruits for Treatment of Diabetes and Diabetic Neuropathy in STZ-Induced Rats

Terpenoids and phenols from Trachyspermum ammi (T. ammi) have reported some pharmacological actions. The objective of the work was to isolate the active constituent, its identification by spectroscopic techniques, and evaluation of the antidiabetic and neuroprotective activity from T. ammi on STZ Wistar rats. The dried fruits of T ammi were kept in a hydrodistillation apparatus to collect essential oil. The isolated fraction went through TLC, UV, FTIR, HPLC, HRMS, C¹³, and ¹H NMR for characterization. Two dosage concentrations from the isolated compound were prepared as 10 and 20 mg/kg for treatment groups. The groups were tested for thermal and mechanical hyperalgesia, writhing, grip strength, spontaneous locomotor test, neuromuscular coordination tests, and histopathological and lipid profile analysis. Diabetes was induced by streptozotocin (45 mg/kg i.p.) and 12 weeks of treatment-induced diabetic neuropathy in Wistar rats. Biomarkers were evaluated to understand the neuropathic protection of thymol on STZ-treated Wistar rats. The biomarker studies (SOD, NO, LPO, Na⁺K⁺ATPase, and TNF-α) further confirmed thymol's diabetic neuropathy protective action. This study suggests that isolated compound thymol was antidiabetic and neuroprotective as it has shown controlled glucose levels defensive nerve damage in STZ Wistar rats. P < 0.05 level of significance was observed in the levels of endogenous biomarkers, fasting blood glucose levels, actophotometer response, and response latency in treated groups compared to the diabetic group, whereas P < 0.001 level of significance during lipid profile levels, thermal algesia, and neuromuscular comparison tests was noted in treated groups compared to the diabetic group.

Current Strategies for the Management of Painful Diabetic Neuropathy

The development of painful diabetic neuropathy (PDN) is a common complication of chronic diabetes that can be associated with significant disability and healthcare costs. Prompt symptom identification and aggressive glycemic control is essential in controlling the development of neuropathic complications; however, adequate pain relief remains challenging and there are considerable unmet needs in this patient population. Although guidelines have been established regarding the pharmacological management of PDN, pain control is inadequate or refractory in a high proportion of patients. Pharmacotherapy with anticonvulsants (pregabalin, gabapentin) and antidepressants (duloxetine) are common first-line agents. The use of oral opioids is associated with considerable morbidity and mortality and can also lead to opioid-induced hyperalgesia. Their use is therefore discouraged. There is an emerging role for neuromodulation treatment modalities including intrathecal drug delivery, spinal cord stimulation, and dorsal root ganglion stimulation. Furthermore, consideration of holistic alternative therapies such as yoga and acupuncture may augment a multidisciplinary treatment approach. This aim of this review is to focus on the current management strategies for the treatment of PDN, with a discussion of treatment rationale and practical considerations for their implementation.

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.

Pharmacotherapy of Painful Diabetic Neuropathy: A Clinical Update

The rising prevalence of diabetes mellitus (DM) leads on to an increase in chronic diabetic complications. Diabetic peripheral neuropathies (DPNs) are common chronic complications of diabetes. Distal symmetric polyneuropathy is the most prevalent form. Most patients with DPN will remain pain-free; however, painful DPN (PDPN) occurs in 6-34% of all DM patients and is associated with reduced health-related-quality-of-life and substantial economic burden. Symptomatic treatment of PDPN and diabetic autonomic neuropathy is the key treatment goals. Using certain patient related characteristics, subjects with PDPN can be stratified and assigned targeted therapies to produce better pain outcomes. The aim of this review is to discuss the various pathogenetic mechanisms of DPN with special reference to the mechanisms leading to PDPN and the various pharmacological and non-pharmacological therapies available for its management. Recommended pharmacological therapies include anticonvulsants, antidepressants, opioid analgesics, and topical medications.

Role of Mechanoinsensitive Nociceptors in Painful Diabetic Peripheral Neuropathy

The cutaneous mechanisms that trigger spontaneous neuropathic pain in diabetic peripheral neuropathy (PDPN) are far from clear. Two types of nociceptors are found within the epidermal and dermal skin layers. Small-diameter lightly myelinated Aδ and unmyelinated C cutaneous mechano and heat-sensitive (AMH and CMH) and C mechanoinsensitive (CMi) nociceptors transmit pain from the periphery to central nervous system. AMH and CMH fibers are mainly located in the epidermis, and CMi fibers are distributed in the dermis. In DPN, dying back intra-epidermal AMH and CMH fibers leads to reduced pain sensitivity, and the patients exhibit significantly increased pain thresholds to acute pain when tested using traditional methods. The role of CMi fibers in painful neuropathies has not been fully explored. Microneurography has been the only tool to access CMi fibers and differentiate AMH, CMH, and CMi fiber types. Due to the complexity, its use is impractical in clinical settings. In contrast, a newly developed diode laser fiber selective stimulation (DLss) technique allows to safely and selectively stimulate Aδ and C fibers in the superficial and deep skin layers. DLss data demonstrate that patients with painful DPN have increased Aδ fiber pain thresholds, while C-fiber thresholds are intact because, in these patients, CMi fibers are abnormally spontaneously active. It is also possible to determine the involvement of CMi fibers by measuring the area of DLss-induced neurogenic axon reflex flare. The differences in AMH, CMH, and CMi fibers identify patients with painful and painless neuropathy. In this review, we will discuss the role of CMi fibers in PDPN.

Efficacy and safety of low-dose naltrexone in painful diabetic neuropathy: A randomized, double-blind, active-control, crossover clinical trial

BACKGROUND

There is a need for newer therapies for chronic painful diabetic neuropathy as the existing drugs have their own limitations. Clinical trials on low-dose naltrexone (1-5 mg/d) showed efficacy and safety in certain chronic painful conditions, but not in painful diabetic neuropathy. Hence the present study was planned.

METHODS

Sixty-seven participants with painful diabetic neuropathy were randomized to receive either 2 mg naltrexone or 10 mg amitriptyline daily following a 2-week run-in period. The participants were followed up every 2 weeks for a total of 6 weeks. Up-titration was done (to 4 mg naltrexone or 25/50 mg amitriptyline) if the pain reduction was less than 20% on the visual analog scale (VAS) during the next follow-up visit. Efficacy was assessed using the change in VAS score at the end of 6 weeks from baseline. Safety was evaluated at each follow-up visit. After 2 weeks of washout period, the participants were crossed over to receive the comparator drug for another 6 weeks with similar evaluations.

RESULTS

The difference (confidence interval) in the change in VAS score between groups from baseline was 1.64 (-0.92 to 4.20) in per-protocol analysis and 1.5 (-1.11 to 4.13) in intention-to-treat analysis. Eight and fifty-two adverse events were reported in the naltrexone and amitriptyline groups, respectively (P < .001). The most common adverse events were mild diarrhea with naltrexone and somnolence with amitriptyline.

CONCLUSIONS

Low-dose naltrexone exhibited similar efficacy and a superior safety profile compared with amitriptyline in painful diabetic neuropathy.

A randomized control trial of duloxetine and gabapentin in painful diabetic neuropathy

BACKGROUND

To analyze the efficacy and safety of duloxetine and gabapentin in painful diabetic neuropathy (PDN).

METHODS

A randomized, open-label, active control, 12-week trial was conducted. A total of 86 participants were randomized in 1:1 ratio into gabapentin 300 mg and duloxetine 60 mg groups. The primary efficacy objective was comparison of mean change in Visual Analogue Scale (VAS) (0-100 points) scores between duloxetine and gabapentin. The symptom scores and adverse events were assessed as secondary outcomes.

RESULTS

Statistically significant (P value<.001) improvement was observed in VAS scores in both duloxetine group and gabapentin group at 12 weeks as compared to baseline. However, no significant difference in VAS scores between duloxetine and gabapentin. Similar improvement in diabetic neuropathy symptoms (DNS), diabetic neuropathy examination (DNE), and neuropathic disability score (NDS) was observed in either group over 12 weeks. There were no significant differences in DNS (P = 0.578), DNE (P = 0.410), and NDS (P = 0.071) scores between the two treatment groups. The overall safety evaluation of both duloxetine and gabapentin were similar. The most common adverse events reported were gastrointestinal.

CONCLUSION

The results indicated that both drugs were effective for the symptomatic relief from PDN and had similar efficacy. Follow-up of patients was only for 12 weeks and therefore the long-term efficacy and safety of the study drugs could not be assessed.

Treatment of Painful Diabetic Neuropathy-A Narrative Review of Pharmacological and Interventional Approaches

Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus that is associated with a significant decline in quality of life. Like other painful neuropathic conditions, PDN is difficult to manage clinically, and a variety of pharmacological and non-pharmacological options are available for this condition. Recommended pharmacotherapies include anticonvulsive agents, antidepressant drugs, and topical capsaicin; and tapentadol, which combines opioid agonism and norepinephrine reuptake inhibition, has also recently been approved for use. Additionally, several neuromodulation therapies have been successfully used for pain relief in PDN, including intrathecal therapy, transcutaneous electrical nerve stimulation (TENS), and spinal cord stimulation (SCS). Recently, 10 kHz SCS has been shown to provide clinically meaningful pain relief for patients refractory to conventional medical management, with a subset of patients demonstrating improvement in neurological function. This literature review is intended to discuss the dosage and prospective data associated with pain management therapies for PDN.

Oral pharmacotherapeutics for the management of peripheral neuropathic pain conditions - a review of clinical trials

INTRODUCTION

Epidemiological studies have shown that 6.9-10% of people suffer from neuropathic pain, a complex painful condition which is often undertreated. Data regarding the effectiveness of treatment options for patients with neuropathic pain is inconsistent, and there is no single treatment option that shows cost-effectiveness across studies.

AREAS COVERED

In this narrative review, the authors present the results of different prospective, randomized controlled trials, systematic reviews and meta-analyses assessing the effects of different oral medications in the management of various peripheral neuropathic pain conditions. The authors discuss the effectiveness of commonly used oral medications such as voltage-gated calcium channels antagonists, voltage-gated sodium channel antagonists, serotonin-norepinephrine reuptake inhibitors, NMDA antagonists, and medications with other mechanisms of action.

EXPERT OPINION

Most of the presented medications were more effective than placebo; however, when compared to each other, none of them were significantly superior. The heterogeneity of the studies looking into different oral neuropathic conditions has been the major issue that prevents us from making stronger recommendations. There are multiple reasons including high placebo responsiveness, improperly treated underlying comorbidities (particularly anxiety and depression), and inter-patient variability. Different sensory phenotypes should also be taken into consideration when designing future clinical trials for neuropathic pain.

High-frequency spinal cord stimulation at 10 kHz for the treatment of painful diabetic neuropathy: design of a multicenter, randomized controlled trial (SENZA-PDN)

BACKGROUND

Painful diabetic neuropathy (PDN), a debilitating and progressive chronic pain condition that significantly impacts quality of life, is one of the common complications seen with long-standing diabetes mellitus. Neither pharmacological treatments nor low-frequency spinal cord stimulation (SCS) has provided significant and long-term pain relief for patients with PDN. This study aims to document the value of 10-kHz SCS in addition to conventional medical management (CMM) compared with CMM alone in patients with refractory PDN.

METHODS

In a prospective, multicenter, randomized controlled trial (SENZA-PDN), 216 subjects with PDN will be assigned 1:1 to receive 10-kHz SCS combined with CMM or CMM alone after appropriate institutional review board approvals and followed for 24 months. Key inclusion criteria include (1) symptoms of PDN for at least 12 months, (2) average pain intensity of at least 5 cm-on a 0- to 10-cm visual analog scale (VAS)-in the lower limbs, and (3) an appropriate candidate for SCS. Key exclusion criteria include (1) large or gangrenous ulcers or (2) average pain intensity of at least 3 cm on VAS in the upper limbs or both. Along with pain VAS, neurological assessments, health-related quality of life, sleep quality, and patient satisfaction will be captured. The primary endpoint comparing responder rates (≥50% pain relief) and safety rates between the treatment groups will be assessed at 3 months. Several secondary endpoints will also be reported on.

DISCUSSION

Enrollment commenced in 2017 and was completed in 2019. This study will help to determine whether 10-kHz SCS improves clinical outcomes and health-related quality of life and is a cost-effective treatment for PDN that is refractory to CMM.

TRIAL REGISTRATION

ClincalTrials.gov identifier: NCT03228420 (registered 24 July 2017).

Current Pharmacological Treatment of Painful Diabetic Neuropathy: A Narrative Review

Background and Objectives: Distal symmetrical polyneuropathy (DSPN) is one of the most common chronic complications of diabetes mellitus. Although it is usually characterized by progressive sensory loss, some patients may develop chronic pain. Assessment of DSPN is not difficult, but the biggest challenge is making the correct diagnosis and choosing the right treatment. The treatment of DSPN has three primary objectives: glycemic control, pathogenic mechanisms, and pain management. The aim of this brief narrative review is to summarize the current pharmacological treatment of painful DSPN. It also summarizes knowledge on pathogenesis-oriented therapy, which is generally overlooked in many publications and guidelines. Materials and Methods: The present review reports the relevant information available on DSPN treatment. The search was performed on PubMed, Cochrane, Semantic Scholar, Medline, Scopus, and Cochrane Library databases, including among others the terms "distal symmetrical polyneuropathy", "neuropathic pain treatment", "diabetic neuropathy", "diabetes complications", "glycaemic control", "antidepressants", "opioids", and "anticonvulsants". Results: First-line drugs include antidepressants (selective serotonin reuptake inhibitors and tricyclic antidepressants) and pregabalin. Second- and third-line drugs include opioids and topical analgesics. While potentially effective in the treatment of neuropathic pain, opioids are not considered to be the first choice because of adverse reactions and addiction concerns. Conclusions: DSPN is a common complication in patients with diabetes, and severely affects the quality of life of these patients. Although multiple therapies are available, the guidelines and recommendations regarding the treatment of diabetic neuropathy have failed to offer a unitary consensus, which often hinders the therapeutic options in clinical practice.

Neuroprotective effect of duloxetine in a mouse model of diabetic neuropathy: Role of glia suppressing mechanisms

AIMS

Painful diabetic neuropathy (PDN) is one of the most frequent complications of diabetes and the current therapies have limited efficacy. This study aimed to study the neuroprotective effect of duloxetine, a serotonin noradrenaline reuptake inhibitor (SNRI), in a mouse model of diabetic neuropathy.

MAIN METHODS

Nine weeks after developing of PDN, mice were treated with either saline or duloxetine (15 or 30 mg/kg) for four weeks. The effect of duloxetine was assessed in terms of pain responses, histopathology of sciatic nerve and spinal cord, sciatic nerve growth factor (NGF) gene expression and on the spinal expression of astrocytes (glial fibrillary acidic protein, GFAP) and microglia (CD₁₁b).

KEY FINDINGS

The present results highlighted that duloxetine (30 mg/kg) increased the withdrawal threshold in von-Frey test. In addition, both doses of duloxetine prolonged the licking time and latency to jump in the hot-plate test. Moreover, duloxetine administration downregulated the spinal expression of both CD₁₁b and GFAP associated with enhancement in sciatic mRNA expression of NGF.

SIGNIFICANCE

The current results highlighted that duloxetine provided peripheral and central neuroprotective effects in neuropathic pain is, at least in part, related to its downregulation in spinal astrocytes and microglia. Further, this neuroprotective effect was accompanied by upregulation of sciatic expression of NGF.

Duloxetine in Painful Diabetic Neuropathy: A Systematic Review

OBJECTIVE

To systematically review the evidence for duloxetine in the management of painful diabetic neuropathy (PDN).

METHODS

Electronic searches of Medline and PubMed were performed from 2005 till October 2015 using medical subject headings and free-text words. Two independent reviewers extracted the data and assessed the methodological quality of the selected studies.

RESULTS

Twenty-three studies met our inclusion criteria and 8 were considered of high quality and were included to this review. Because of heterogeneity of the studies included in this review, statistical pooling of the data was not possible. We found good evidence for use of duloxetine in PDN over placebo and pregabalin but there was no benefit of duloxetine over amitriptyline.

CONCLUSIONS

Duloxetine has a beneficial effect over placebo. Nevertheless, the evidence of superiority of duloxetine over pregabalin and amitriptyline should be explored further as there was only 1 trial for each category. Provided majority of the PDN patients share cardiovascular complications, use of duloxetine will be a good option for treating pain associated with PDN over amitriptyline. Future randomized controlled trials should be designed keeping this in mind.

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.

Acid-Sensing Ion Channels as Potential Pharmacological Targets in Peripheral and Central Nervous System Diseases

Acid-sensing ion channels (ASICs) are widely expressed in the body and represent good sensors for detecting protons. The pH drop in the nervous system is equivalent to ischemia and acidosis, and ASICs are very good detectors in discriminating slight changes in acidity. ASICs are important pharmacological targets being involved in a variety of pathophysiological processes affecting both the peripheral nervous system (e.g., peripheral pain, diabetic neuropathy) and the central nervous system (e.g., stroke, epilepsy, migraine, anxiety, fear, depression, neurodegenerative diseases, etc.). This review discusses the role played by ASICs in different pathologies and the pharmacological agents acting on ASICs that might represent promising drugs. As the majority of above-mentioned pathologies involve not only neuronal dysfunctions but also microvascular alterations, in the next future, ASICs may be also considered as potential pharmacological targets at the vasculature level. Perspectives and limitations in the use of ASICs antagonists and modulators as pharmaceutical agents are also discussed.

Evidence and clinical considerations for the use of serotonin and norepinephrine reuptake inhibitors for the treatment of painful neuropathy

Introduction

Peripheral neuropathy is a painful condition that can lead to a reduction in quality of life. The pain, which stems from damaged, hyperexcitable neurons, does not respond to traditional analgesics. However, due to the underlying mechanism of pain, some antidepressants are effective in managing peripheral neuropathy. The purpose of this review is to evaluate the available literature on serotonin-norepinephrine reuptake inhibitors for the management of peripheral neuropathy and outline clinical considerations for choosing an agent.

Methods

PubMed, Ovid/MEDLINE, and Scopus queries were conducted for relevant literature. Search types were limited to keyword searches and articles were limited to those published prior to March 31, 2015.

Results

There were 19 randomized controlled trials included in this review. No articles were found investigating the use of desvenlafaxine, milnacipran, or levomilnacipran for treatment of neuropathy. Both duloxetine and venlafaxine improved pain severity scores for patients suffering from painful peripheral neuropathy compared to placebo.

Discussion

Duloxetine and venlafaxine are able to decrease the severity of peripheral neuropathic pain. None of the trials found that either one of the therapies was able to completely eliminate pain for the patients, which should be an important counseling point for patients to understand. Additionally, patient-specific factors should be considered when choosing an agent, including comorbid disease states and potentially interacting medications.

Trends, correlates, and disease patterns of antidepressant use among elderly persons in Taiwan

PURPOSE

The population-based National Health Insurance database was used to investigate the trends, correlates, and disease patterns for elderly people in Taiwan who use antidepressants.

METHODS

The National Health Research Institute provided a database of 1000,000 random subjects for study. We created a sample of subjects who were older than 65 years from 1997 to 2005. Trends, prevalence, and associated factors of antidepressant use were detected. We also examined the proportion of antidepressant use for psychiatric and medical disorders.

RESULTS

The one-year prevalence of antidepressant use in elderly persons increased from 5.8 % in 1997 to 9.8 % in 2005. The one-year prevalence rates of tricyclic antidepressant (TCA), selective serotonin reuptake inhibitor (SSRI), serotonin-norepinephrine reuptake inhibitor (SNRI), serotonin modulator, and other antidepressant use in 2005 were 5.3, 2.6, 0.4, 2.9, and 0.6 %, respectively. Overall antidepressant use was higher for those in the 75- to 84-year-old age group, females, and those with higher Charlson Comorbidity Index scores. Among subjects using TCAs, 77.6 % users did not have a psychiatric diagnosis. Psychiatric disorders were commonly found in most SSRI and SNRI users (85.1 and 90.1 %, respectively). Subjects using SSRIs and SNRIs had higher proportions of psychiatric disorders such as neurotic depression, major depression, senile and presenile organic psychotic conditions, and anxiety.

CONCLUSION

The prevalence of antidepressant use among elderly persons increased greatly from 1997 to 2005. SSRIs, SNRIs, and other antidepressants were used mostly by subjects with psychiatric disorders, whereas TCAs were used mostly by subjects with nonpsychiatric disorders.

A review of the clinical utility of duloxetine in the treatment of diabetic peripheral neuropathic pain

Diabetes mellitus is a world-wide epidemic with many long-term complications, with neuropathy being the most common. In particular, diabetic peripheral neuropathic pain (DPNP), can be one of the most distressing complications associated with diabetes, leading to decreases in physical and mental quality of life. Despite the availability of many efficient medications, DPNP remains a challenge to treat, and the optimal sequencing of pharmacotherapy remains unknown. Currently, there are only three medications approved by the US Food and Drug Administration specifically for the management of DPNP. Duloxetine (DUL), a selective serotonin-norepinephrine reuptake inhibitor, is one of these. With the goal of optimizing pharmacotherapy use in DPNP population, a review of current literature was conducted, and the clinical utility of DUL described. Along with early clinical trials, recently published observational studies and pharmacoeconomic models may be useful in guiding decision making by clinicians and managed care organizations. In real-world practice settings, DUL is associated with decreased or similar opioid utilization, increased medication adherence, and similar health care costs compared with current standard of care. DUL has consistently been found to be a cost-effective option over short time-horizons. Currently, the long-term cost-effectiveness of DUL is unknown. Evidence derived from randomized clinical trials, real-world observations, and economic models support the use of DUL as a first-line treatment option from the perspective of the patient, clinician, and managed care payer.

Amitriptyline for neuropathic pain in adults

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 12, 2012. That review considered both fibromyalgia and neuropathic pain, but the effects of amitriptyline for fibromyalgia are now dealt with in a separate review.Amitriptyline is a tricyclic antidepressant that is widely used to treat chronic neuropathic pain (pain due to nerve damage). It is recommended as a first line treatment in many guidelines. Neuropathic pain can be treated with antidepressant drugs in doses below those at which the drugs act as antidepressants.

OBJECTIVES

To assess the analgesic efficacy of amitriptyline for relief of chronic neuropathic pain, and the adverse events associated with its use in clinical trials.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and EMBASE to March 2015, together with two clinical trial registries, and the reference lists of retrieved papers, previous systematic reviews, and other reviews; we also used our own hand searched database for older studies.

SELECTION CRITERIA

We included randomised, double-blind studies of at least four weeks' duration comparing amitriptyline with placebo or another active treatment in chronic neuropathic pain conditions.

DATA COLLECTION AND ANALYSIS

We performed analysis using three tiers of evidence. First tier evidence derived from data meeting current best standards and subject to minimal risk of bias (outcome equivalent to substantial pain intensity reduction, intention-to-treat analysis without imputation for dropouts; at least 200 participants in the comparison, 8 to 12 weeks' duration, parallel design), second tier from data that failed to meet one or more of these criteria and were considered at some risk of bias but with adequate numbers in the comparison, and third tier from data involving small numbers of participants that were considered very likely to be biased or used outcomes of limited clinical utility, or both.

MAIN RESULTS

We included 15 studies from the earlier review and two new studies (17 studies, 1342 participants) in seven neuropathic pain conditions. Eight cross-over studies with 302 participants had a median of 36 participants, and nine parallel group studies with 1040 participants had a median of 84 participants. Study quality was modest, though most studies were at high risk of bias due to small size.There was no first-tier or second-tier evidence for amitriptyline in treating any neuropathic pain condition. Only third-tier evidence was available. For only two of seven studies reporting useful efficacy data was amitriptyline significantly better than placebo (very low quality evidence).More participants experienced at least one adverse event; 55% of participants taking amitriptyline and 36% taking placebo. The risk ratio (RR) was 1.5 (95% confidence interval (CI) 1.3 to 1.8) and the number needed to treat for an additional harmful outcome was 5.2 (3.6 to 9.1) (low quality evidence). Serious adverse events were rare. Adverse event and all-cause withdrawals were not different, but were rarely reported (very low quality evidence).

AUTHORS' CONCLUSIONS

Amitriptyline has been a first-line treatment for neuropathic pain for many years. The fact that there is no supportive unbiased evidence for a beneficial effect is disappointing, but has to be balanced against decades of successful treatment in many people with neuropathic pain. There is no good evidence of a lack of effect; rather our concern should be of overestimation of treatment effect. Amitriptyline should continue to be used as part of the treatment of neuropathic pain, but only a minority of people will achieve satisfactory pain relief. Limited information suggests that failure with one antidepressant does not mean failure with all.

Pharmacological treatment of diabetic peripheral neuropathy

Pain modulation is a key treatment goal for diabetic peripheral neuropathy patients. Guidelines have recommended antidepressant, anticonvulsant, analgesic, and topical medications-both approved and off-label-to reduce pain in this population.

Effectiveness of duloxetine compared with pregabalin and gabapentin in diabetic peripheral neuropathic pain: results from a German observational study

OBJECTIVES

This study aimed to compare the effectiveness of duloxetine (DLX) and the anticonvulsants pregabalin (PGB) and gabapentin (GBP) for the treatment of diabetic peripheral neuropathic pain (DPNP) in routine clinical care.

MATERIALS AND METHODS

Data from a 6-month, noninterventional study involving 2575 patients in whom treatment of DPNP was initiated with or changed to DLX, PGB, or GBP (n=1523) were analyzed post hoc; patients treated with other medications or combinations were excluded from this analysis. Propensity scoring was used to compare patient groups, assessing Brief Pain Inventory (BPI), Clinical and Patient Global Impression (CGI/PGI), the Hospital Anxiety and Depression Scale (HADS), the Sheehan Disability Scale (SDS), and the Short Form Health Survey (SF 12).

RESULTS

Mean median daily dosage over 6 months was 53.9 mg for DLX (N=931), 173.5 mg for PGB (N=248), and 727.8 mg for GBP (N=351). BPI average pain severity (last observation carried forward, mean [SD]) decreased by 2.3 [2.30] points for DLX patients, and by 1.9 [2.22] in PGB, and 1.1 [2.15] in GBP patients. This difference remained statistically significant (DLX vs. PGB: P=0.029; DLX vs. GBP: P<0.001) after adjustment by propensity scores. Similar findings were also seen for the BPI interference score, CGI and PGI, the HADS anxiety score, the HADS depression score.

DISCUSSION

When compared with DLX, the low doses of PGB and GBP used in this noninterventional study might have contributed to the lower effectiveness found for both anticonvulsants in the treatment of patients with DPNP.

Review of antidepressants in the treatment of neuropathic pain

Introduction

Neuropathy is a pathological pain disorder characterized by burning, stabbing, and cramping sensations. There are multiple etiologies for this pain such as diabetes, vascular disorders, and chemotherapy treatment. Neurotransmitters, such as norepinephrine and serotonin, are thought to play a part in the modulation of this pain. The objective of this review is to summarize the current literature to support the efficacy and impact of adverse events of the various classes of antidepressants utilized in the treatment of neuropathic pain.

Methods

A Medline/Pubmed search was conducted to identify randomized clinical trials within the last 12 years examining the efficacy and safety of antidepressants for the treatment of neuropathy. Systematic reviews and meta-analyses were also included.

Results

Antidepressants are commonly used in the treatment of neuropathy, with meta-analyses supporting the use of tricyclic antidepressants and selective norepinephrine serotonin reuptake inhibitors. Trials indicate that venlafaxine, duloxetine, and tricyclic antidepressants (TCAs) have comparable efficacy, but TCAs have a higher incidence of adverse effects. Other antidepressants, such as citalopram, paroxetine, and bupropion have limited evidence supporting their use in neuropathy.

Discussion

Based on the evidence reviewed, venlafaxine and duloxetine should be used as first-line agents. TCAs should be used as second-line agents, due to higher incidence of adverse effects. Other treatment options include citalopram, paroxetine, and bupropion, but data supporting their efficacy is limited.

Diabetic neuropathic pain: Physiopathology and treatment

Diabetic neuropathy is a common complication of both type 1 and type 2 diabetes, which affects over 90% of the diabetic patients. Although pain is one of the main symptoms of diabetic neuropathy, its pathophysiological mechanisms are not yet fully known. It is widely accepted that the toxic effects of hyperglycemia play an important role in the development of this complication, but several other hypotheses have been postulated. The management of diabetic neuropathic pain consists basically in excluding other causes of painful peripheral neuropathy, improving glycemic control as a prophylactic therapy and using medications to alleviate pain. First line drugs for pain relief include anticonvulsants, such as pregabalin and gabapentin and antidepressants, especially those that act to inhibit the reuptake of serotonin and noradrenaline. In addition, there is experimental and clinical evidence that opioids can be helpful in pain control, mainly if associated with first line drugs. Other agents, including for topical application, such as capsaicin cream and lidocaine patches, have also been proposed to be useful as adjuvants in the control of diabetic neuropathic pain, but the clinical evidence is insufficient to support their use. In conclusion, a better understanding of the mechanisms underlying diabetic neuropathic pain will contribute to the search of new therapies, but also to the improvement of the guidelines to optimize pain control with the drugs currently available.

Treatment of painful diabetic peripheral neuropathy

BACKGROUND

Painful diabetic peripheral neuropathy impairs quality of life and can be difficult to treat.

OBJECTIVE

To discuss current treatment recommendations for painful diabetic peripheral neuropathy.

STUDY DESIGN

Literature review.

METHODS

Systematic review of the literature discussing treatment of painful diabetic peripheral neuropathy. Existing treatment guidelines were studied and compared.

RESULTS

Painful diabetic peripheral neuropathy occurs in about one in six people with diabetes. This condition impairs quality of life and increases healthcare costs. Treatment recommendations exist, but individual patient therapy can require a trial-and-error approach. Many treatment options have adjuvant benefits or side effects which should be considered prior to initiating therapy. Often, a combination of treatment modalities with various mechanisms of action is required for adequate pain control. Adequate medication titration and a reasonable trial period should be allowed.

CONCLUSION

The treatment of painful diabetic peripheral neuropathy can be challenging, but effective management can improve patient's quality of life.

CLINICAL RELEVANCE

Painful diabetic peripheral neuropathy impairs quality of life and can be difficult to treat. Many treatment options have adjuvant benefits or side effects which should be considered prior to initiating therapy. Often, a combination of treatment modalities with various mechanisms of action is required for adequate pain control.

Information for physicians and pharmacists about drugs that might cause dry mouth: a study of monographs and published literature

BACKGROUND

Over three-quarters of the older population take medications that can potentially cause dry mouth. Physicians or pharmacists rarely inform patients about this adverse effect and its potentially severe damage to the teeth, mouth and general health.

OBJECTIVES

The objectives of this study were to (1) identify warnings in the literature about dry mouth associated with the most frequently prescribed pharmaceutical products in Canada; and (2) consider how this information might be obtained by physicians, pharmacists and patients.

METHODS

Monographs on the 72 most frequently prescribed medications during 2010 were retrieved from the Compendium of Pharmaceuticals and Specialties (CPS, a standard drug information reference for physicians and pharmacists), the National Library of Medicine's 'DailyMed' database, directly from the manufacturers, and from a systematic search of biomedical journals.

RESULTS

The CPS provided monographs for 43% of the medications, and requests to manufacturers produced the remaining monographs. Mentions of dry mouth were identified in 61% of the products (43% amongst CPS monographs; an additional 43% amongst manufacturers' monographs; 7% in the DailyMed database and 7% from biomedical journals); five medications had contradictory reports in different monographs.

CONCLUSION

Nearly two-thirds (61%) of the most commonly prescribed medications can cause dry mouth, yet warnings about this adverse effect and its potentially serious consequences are not readily available to physicians, pharmacists, dentists or patients.

Comparative safety and tolerability of duloxetine vs. pregabalin vs. duloxetine plus gabapentin in patients with diabetic peripheral neuropathic pain

OBJECTIVE

The safety and tolerability of three treatments for diabetic peripheral neuropathic pain (DPNP) were compared.

METHODS

A 12-week, randomized, open-label study confirming the non-inferiority of duloxetine (N = 138) vs. pregabalin (N = 134) and the combination of duloxetine plus gabapentin (N = 135) as the primary outcome was previously published. Patients had an inadequate pain response to a stable dose of gabapentin (≥ 900 mg/day) for ≥ 5 weeks prior to study enrolment. Data from that study were assessed in this current analysis for a detailed report of safety and tolerability.

RESULTS

Completion rates did not differ significantly between the groups. Discontinuation because of adverse events was significantly greater in the duloxetine (19.6%) vs. pregabalin group (10.4%; p = 0.04); no differences emerged between the duloxetine vs. duloxetine plus gabapentin (13.3%) groups (p = 0.19) or pregabalin vs. duloxetine plus gabapentin groups (p = 0.57). Adverse event rates varied: nausea, insomnia, hyperhidrosis and decreased appetite were reported significantly more often in patients treated with duloxetine vs. patients treated with pregabalin (each p ≤ 0.01); insomnia significantly more in patients treated with duloxetine vs. duloxetine plus gabapentin (p = 0.01); peripheral oedema significantly more in patients treated with pregabalin vs. duloxetine and duloxetine plus gabapentin (p ≤ 0.001 each) and nausea, hyperhidrosis, decreased appetite and vomiting significantly more in patients treated with duloxetine plus gabapentin vs. pregabalin (each p ≤ 0.05). At end-point, weight change differed significantly among treatment groups: patients in the pregabalin group on average gained weight (1.0 ± 0.04 kg); while, patients in the duloxetine and duloxetine plus gabapentin groups on average lost weight (-2.39 ± 0.04 and -1.06 ± 0.04 kg, respectively) (pregabalin vs. duloxetine, p ≤ 0.001; pregabalin vs. duloxetine plus gabapentin, p ≤ 0.001; duloxetine vs. duloxetine plus gabapentin, p = 0.01).

CONCLUSION

Duloxetine, pregabalin and duloxetine plus gabapentin were generally safe and tolerable for the treatment of DPNP.

Clinical experience with desvenlafaxine in treatment of pain associated with diabetic peripheral neuropathy

Purpose

To assess the safety and efficacy of the serotonin–norepinephrine reuptake inhibitor desvenlafaxine in adults with painful diabetic peripheral neuropathy (DPN).

ClinicalTrials.gov identifiers

NCT00283842, NCT01050218.

Patients and methods

This was a 13-week, randomized, double-blind, placebo-controlled, fixed-dose study of desvenlafaxine in adults with painful DPN. The primary efficacy endpoint was change from baseline in numeric rating scale (NRS) score. Patients who completed the 13-week trial could continue in a 9-month open-label, flexible-dose extension study.

Results

A total of 412 patients were randomized to treatment with placebo or desvenlafaxine 50, 100, 200, or 400 mg/day. Of those, 240 patients continued in the extension study. After a planned interim analysis, conducted when the first 225 patients had completed 6 weeks of treatment in the short-term study, randomization to the 50 mg or 400 mg doses was stopped. At week 13, the mean change from baseline in NRS score was significantly greater compared with placebo in the desvenlafaxine 200 mg (difference [95% confidence interval {CI}]: 1.10 [0.50 to 1.70]; P<0.001) and 400 mg groups (0.91 [95% CI: 0.23 to 1.59]; P=0.027); differences from placebo were not statistically significant for the 50 mg (0.58 [95% CI: −0.08 to 1.25]) and 100 mg (0.59 [95% CI: –0.03 to 1.21]) groups. Nausea and dizziness were the most common treatment-emergent adverse events reported in the short-term study, and the most common adverse events leading to discontinuation in the short-term study and the extension. Adverse events rates were dose-dependent in the short-term studies.

Conclusion

Desvenlafaxine was effective in relieving pain associated with DPN at doses of 200 and 400 mg/day, and improved activity impairment at all doses assessed. Desvenlafaxine was generally well-tolerated in the short-term and long-term studies.

Duloxetine for treating painful neuropathy, chronic pain or fibromyalgia

BACKGROUND

Duloxetine is a balanced serotonin and noradrenaline reuptake inhibitor licensed for the treatment of major depressive disorders, urinary stress incontinence and the management of neuropathic pain associated with diabetic peripheral neuropathy. A number of trials have been conducted to investigate the use of duloxetine in neuropathic and nociceptive painful conditions. This is the first update of a review first published in 2010.

OBJECTIVES

To assess the benefits and harms of duloxetine for treating painful neuropathy and different types of chronic pain.

SEARCH METHODS

On 19th November 2013, we searched The Cochrane Neuromuscular Group Specialized Register, CENTRAL, DARE, HTA, NHSEED, MEDLINE, and EMBASE. We searched ClinicalTrials.gov for ongoing trials in April 2013. We also searched the reference lists of identified publications for trials of duloxetine for the treatment of painful peripheral neuropathy or chronic pain.

SELECTION CRITERIA

We selected all randomised or quasi-randomised trials of any formulation of duloxetine, used for the treatment of painful peripheral neuropathy or chronic pain in adults.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We identified 18 trials, which included 6407 participants. We found 12 of these studies in the literature search for this update. Eight studies included a total of 2728 participants with painful diabetic neuropathy and six studies involved 2249 participants with fibromyalgia. Three studies included participants with depression and painful physical symptoms and one included participants with central neuropathic pain. Studies were mostly at low risk of bias, although significant drop outs, imputation methods and almost every study being performed or sponsored by the drug manufacturer add to the risk of bias in some domains. Duloxetine at 60 mg daily is effective in treating painful diabetic peripheral neuropathy in the short term, with a risk ratio (RR) for ≥ 50% pain reduction at 12 weeks of 1.73 (95% CI 1.44 to 2.08). The related NNTB is 5 (95% CI 4 to 7). Duloxetine at 60 mg daily is also effective for fibromyalgia over 12 weeks (RR for ≥ 50% reduction in pain 1.57, 95% CI 1.20 to 2.06; NNTB 8, 95% CI 4 to 21) and over 28 weeks (RR 1.58, 95% CI 1.10 to 2.27) as well as for painful physical symptoms in depression (RR 1.37, 95% CI 1.19 to 1.59; NNTB 8, 95% CI 5 to 14). There was no effect on central neuropathic pain in a single, small, high quality trial. In all conditions, adverse events were common in both treatment and placebo arms but more common in the treatment arm, with a dose-dependent effect. Most adverse effects were minor, but 16% of participants stopped the drug due to adverse effects. Serious adverse events were rare.

AUTHORS' CONCLUSIONS

There is adequate amounts of moderate quality evidence from eight studies performed by the manufacturers of duloxetine that doses of 60 mg and 120 mg daily are efficacious for treating pain in diabetic peripheral neuropathy but lower daily doses are not. Further trials are not required. In fibromyalgia, there is lower quality evidence that duloxetine is effective at similar doses to those used in diabetic peripheral neuropathy and with a similar magnitude of effect. The effect in fibromyalgia may be achieved through a greater improvement in mental symptoms than in somatic physical pain. There is low to moderate quality evidence that pain relief is also achieved in pain associated with depressive symptoms, but the NNTB of 8 in fibromyalgia and depression is not an indication of substantial efficacy. More trials (preferably independent investigator led studies) in these indications are required to reach an optimal information size to make convincing determinations of efficacy.Minor side effects are common and more common with duloxetine 60 mg and particularly with 120 mg daily, than 20 mg daily, but serious side effects are rare.Improved direct comparisons of duloxetine with other antidepressants and with other drugs, such as pregabalin, that have already been shown to be efficacious in neuropathic pain would be appropriate. Unbiased economic comparisons would further help decision making, but no high quality study includes economic data.

Gabapentin reverses central pain sensitization following a collagenase-induced intrathalamic hemorrhage in rats

PURPOSE

The treatment of central neuropathic pain remains amongst the biggest challenges for pain specialists. The main objective of this study was to assess gabapentin (GBP), amitriptyline (AMI), and carbamazepine (CARBA) for the treatment of a rodent central neuropathic pain model.

METHODS

Male Sprague Dawley rats were trained on the rotarod, Hargreaves, Von Frey and acetone behavioral tests, and baseline values were obtained prior to surgery. A stereotaxic injection of either a collagenase solution or saline was made in the right ventral posterolateral thalamic nucleus. The rats were tested on days 2, 4, 8, and 11 postsurgery. They were retested at regular intervals from day 15 to day 25 postsurgery, after oral administration of either the vehicle (n=7 and n=8 rats with intracerebral injections of collagenase and saline, respectively) or the different drugs (GBP [60 mg/kg], AMI [10 mg/kg], CARBA [100 mg/kg]; n=8 rats/drug).

RESULTS

A significant decrease in the mechanical thresholds and no change in heat threshold were observed in both hind limbs in the collagenase group, as we had previously shown elsewhere. Reversal of the mechanical hypersensitivity was achieved only with GBP (P<0.05). AMI and CARBA, at the dosages used, failed to show any effect on mechanical thresholds. Transient cold allodynia was observed in some collagenase-injected rats but failed to be statistically significant.

CONCLUSION

Intrathalamic hemorrhaging in the ventrolateral thalamic nucleus induced a bilateral mechanical allodynia, which was reversed by GBP but not AMI or CARBA.