Pregabalin for relief of neuropathic pain associated with diabetic neuropathy: a randomized, double-blind study

Pregabalin for Neuropathic Pain and Itch in Recessive Dystrophic Epidermolysis Bullosa: A Randomized Crossover Trial

Importance

Patients with recessive dystrophic epidermolysis bullosa (RDEB) experience neuropathic pain and itch. There is a lack of evidence on any treatment for these symptoms in patients with RDEB.

Objectives

To test the efficacy of pregabalin in the treatment of neuropathic pain and itch in patients with RDEB.

Design, Setting, and Participants

A randomized, double-blinded, crossover trial of oral pregabalin (50-300 mg/d) vs placebo was conducted at 2 sites, Toronto (Canada) and Santiago (Chile) from January 1, 2019, to December 31, 2020. Patients eligible to participate were diagnosed with RDEB, aged 8 to 40 years, not pregnant or lactating (if female), and had evidence of probable neuropathic pain and itching defined as distal thermal sensory loss (confirmed by thermal roller), score of 4 or greater on the Douleur Neuropathique 4 questionnaire (DN4), and score greater than 4 on the 10-point visual analog scale [VAS]). Patients with a clinically important or poorly controlled medical or psychiatric condition or pregabalin intolerance or allergy were excluded. Of 41 patients screened, 3 were not eligible and 28 declined enrollment. Data analyses were performed in 2021 through 2023.

Intervention

Participants received both pregabalin and matched placebo (titrated to a maximum-tolerated dose of 300 mg/day) in a randomized sequence so that comparisons could be made within participants and between groups.

Main Outcomes and Measures

Difference in the mean pain and itch scores between pregabalin and placebo treatment (measured using VAS) before and after intervention.

Results

In all, 10 participants were randomized to 2 groups, 6 patients (mean [SD] age, 26.7 [8.1] years; 3 females [50%]) in group 1, and 4 patients (mean [SD] age, 26.5 [7.8] years, 2 females [50%]) in group 2. Group 1 received a sequence of pregabalin-placebo while group 2 received placebo-pregabalin. Pregabalin significantly reduced mean (SD) pain scores by 1.9 (1.5) points when controlling for sequence and treatment period vs baseline, while placebo had 0.1 (2.0) points of reduction. The effect of pregabalin was a mild but significant reduction in itch compared to baseline (mean [SD] points, 0.9 [2.2]), whereas the placebo produced no reduction (0.1 [2.5]). The mean pregabalin dose was generally well tolerated.

Conclusions and Relevance

The results of this randomized crossover trial indicate that pregabalin significantly reduced pain and itch scores from baseline compared to placebo in patients with RDEB. This feasibility study provided preliminary data on the efficacy of pregabalin in managing pain and itch in RDEB and gathered essential data to inform the design of a larger cohort trial.

Trial Registration

ClinicalTrials.gov Identifier: NCT03928093.

Comparative efficacy and safety of gabapentin, pregabalin, oxcarbazepine, and duloxetine in diabetic peripheral neuropathy: A network meta-analysis

Purpose

To conduct a network meta-analysis comparing the safety and efficacy of gabapentin (GBP), pregabalin (PGB), oxcarbazepine (OXC), and duloxetine (DLX) in treating diabetic peripheral neuropathy (DPN).

Materials and Methods

The study's eligibility criteria includee randomized controlled trials (RCTs) with a focus on DPN patients receiving GBP, PGB, DLX, or OXC versus placebo. Noncompliant trials with incomplete information and observational studies were excluded.

Results

Twelve (RCTs) of PGB, 2 of GBP, 3 of DLX, and 1 of OXC met the inclusion criteria. When drugs were compared for efficacy (direct comparison), GBP (Odd's ratio [OR] = 3.208, P < 0.001) was most effective followed by OXC (OR = 2.4, P = 0.0248), DLX (OR = 2.346, P < 0.001), and PGB (OR = 2.161, P < 0.001). When drugs were compared for withdrawal due to adverse drug reaction (ADR) (direct comparison), GBP (OR = 1.3818, P = 0.766) was safest followed by PGB (OR = 2.16, P < 0.001), DLX (OR = 2.469, P < 0.001), and OXC (OR = 4.4967, P = 0.001). Indirect comparison was done for efficacy, DLX was statistically significant than PGB and OXC (DLX vs. PGB, P = 0.03; DLX vs. OXC, P = 0.02). When indirect comparison was done for patient withdrawal due to ADR, OXC was worst (GBP vs. OXC, P = 0.0001; PGB vs. OXC, P = 0.007; DLX vs. OXC, P = 0.015). When drugs were compared for individual ADRs (direct comparison), dizziness was most commonly seen with OXC (OR = 9.6535, P = 1.8425), headache with OXC (OR = 3.8686, P = 0.006), somnolence with PGB (OR = 5.189, P < 0.001), and nausea with DLX (OR = 3.264, P < 0.001). GBP was most effective and safest drug followed by OXC > DLX > PGB for efficacy and PGB > DLX > OXC for safety.

Conclusion

In evaluating medications for DPN against placebo, GBP and OXC demonstrated the highest effectiveness while maintaining a favorable safety profile.

Comparative Study on the Efficacy of Pregabalin Versus Limaprost in Patients With Lumbar Spinal Stenosis: A Prospective, Randomized Controlled Trial

BACKGROUND

Patients with Lumbar Spinal Stenosis (LSS) typically complain of back pain and leg pain. These symptoms reduce the quality of life (QoL) and also cause sleep disturbances. This study compares pregabalin and limaprost's efficacy in LSS for pain, disability, QoL, and sleep, aiming to offer insights for medication selection.

METHODS

This study was designed as a prospective, randomized, single-center, single-blinded, clinical superiority trial targeting patients with LSS. For 6 weeks, 111 patients per group were administered medication following a standard regimen, after which patient-reported outcomes were measured. The primary outcome was the Visual Analogue Scale (VAS) for back and leg pain, and the secondary outcomes included the Oswestry Disability Index (ODI), European Quality of Life 5 Dimensions (EQ-5D), and sleep quality.

RESULTS

After 6 weeks of medication, there were significant improvements over time in the primary outcome, VAS for back pain and leg pain, in both groups, but no significant difference between the 2 groups. Similarly, for the secondary outcomes, ODI and EQ-5D, both groups showed significant improvements, yet there was no significant difference between them. In the subgroup analysis targeting poor sleepers (Pittsburgh sleep quality index, PSQI >5), both groups also exhibited significant improvements in sleep quality, but again, there was no significant difference between the groups.

CONCLUSIONS

Efficacy of pregabalin, limaprost in back and leg pain, ODI, EQ-5D, and sleep quality, but there was no significant difference between the 2 groups. Thus, it is advisable to prescribe based on individual drug responses and potential complications.

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

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

Placebo and nocebo responses in painful diabetic neuropathy: systematic review and meta-analysis

ABSTRACT

This preregistered (CRD42021223379) systematic review and meta-analysis aimed to characterize the placebo and nocebo responses in placebo-controlled randomized clinical trials (RCTs) on painful diabetic neuropathy (PDN), updating the previous literature by a decade. Four databases were searched for PDN trials published in the past 20 years, testing oral medications, adopting a parallel-group design. Magnitude of placebo or nocebo responses, Cochrane risk of bias, heterogeneity, and moderators were evaluated. Searches identified 21 studies (2425 placebo-treated patients). The overall mean pooled placebo response was -1.54 change in the pain intensity from baseline [95% confidence interval (CI): -1.52, -1.56, I 2 = 72], with a moderate effect size (Cohen d = 0.72). The pooled placebo 50% response rate was 25% [95% CI: 22, 29, I 2 = 50%]. The overall percentage of patients with adverse events (AEs) in the placebo arms was 53.3% [95% CI: 50.9, 55.7], with 5.1% [95% CI: 4.2, 6] of patients dropping out due to AEs. The year of study initiation was the only significant moderator of placebo response (regression coefficient = -0.06, [95% CI: -0.10, -0.02, P = 0.007]). More recent RCTs tended to be longer, bigger, and to include older patients (N = 21, rs = 0.455, P = 0.038, rs = 0.600, P = 0.004, rs = 0.472, P = 0.031, respectively). Our findings confirm the magnitude of placebo and nocebo responses, identify the year of study initiation as the only significant moderator of placebo response, draw attention to contextual factors such as confidence in PDN treatments, patients' previous negative experiences, intervention duration, and information provided to patients before enrollment.

The safety and efficacy of gabapentinoids in the management of neuropathic pain: a systematic review with meta-analysis of randomised controlled trials

BACKGROUND

There are increasing concerns regarding the abusive potential of gabapentinoids putting at risk patients with neuropathic pain requiring long-term pain management. The evidence to support this is rather inconcusive.

AIM

This systematic review aimed to evaluate the safety and efficacy of gabapentinoids in the management of neuropathic pain with a focus on randomised controlled trials (RCTs) and categorising the side effects according to the body systems they were affecting.

METHOD

Searches were conducted in MEDLINE (PubMed), EMBASE, Web of Science, PsycoINFO, and CINAHL (EBSCO), and included RCTs to identify and critically appraise studies investigating safety and therapeutic effects of gabapentionoids in adults with neuropathic pain. Data extraction was conducted using an established Cochrane form and the risk-of-bias tool was used in the assessment of quality.

RESULTS

50 studies (12,398 participants) were included. The majority of adverse events pertained to the nervous system (7 effects) or psychiatric (3 effects) disorders. There were more adverse effects reported with pregabalin (36 effects) than with gabapentin (22 effects). Six pregabalin studies reported euphoria as a side effect, while no studies reported euphoria with gabapentin. This was the only side effect that may correlate with addictive potential. Gabapentioids were reported to significantly reduce pain compared to placebo.

CONCLUSION

Despite RCTs documenting the adverse events of gabapentionoids on the nervous system, there was no evidence of gabapentinoid use leading to addiction, suggesting an urgent need to design studies investigating their abusive potential.

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

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

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.

Comparative Benefit-Risk Assessment for Lidocaine 700 mg Medicated Plaster and Pregabalin in Peripheral Neuropathic Pain Following a Structured Framework Approach

Introduction

Peripheral neuropathic pain (PNP) is difficult to treat. Several oral drugs are recommended as first-line treatments. Nevertheless, many patients cannot obtain sufficient pain relief or do not tolerate systemically active treatments. Topical treatments, with a lower risk of systemic side effects such as lidocaine 700 mg medicated plaster, are also recommended in treatment guidelines. This analysis compares the benefit–risk balance of topical 700 mg lidocaine medicated plaster with the benefit–risk balance of oral pregabalin administration for the treatment of PNP following current recommendations on benefit–risk assessment (BRA) methodology.

Methods

The Benefit–Risk Action Team (BRAT) framework was used as structured approach. Selection of key benefits and risks was supported by a patient survey. Published randomized controlled clinical trials were the main source to identify data related to key benefits and risks. The outcome of randomized clinical trials was compared with real-world evidence (RWE) data for consistency.

Results

Identified key benefits were pain reduction and improvement in quality of life. Key risks identified were application site reactions, dizziness, confusion, weight gain, peripheral edema, and blurred vision. Overall, there was similarity in key benefits between the comparators; however, a clear advantage regarding key risks in favor of lidocaine 700 mg medicated plaster was observed. This observation was consistent across data from a direct comparison trial, randomized placebo-controlled trials, as well as data from RWE studies. The low number of randomized controlled trials for lidocaine 700 mg medicated plaster was the main limitation.

Conclusion

Guided by the opinion of patients regarding key benefits and risks deemed important for treatments of peripheral neuropathic pain, our analysis showed that lidocaine 700 mg medicated plaster has a more favorable benefit–risk balance compared to pregabalin (300 and 600 mg daily).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40122-021-00340-2.

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

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

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

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

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

Systematic Review Registration: PROSPERO, identifier: CRD42020197397.

Evaluating the impact of gabapentinoids on sleep health in patients with chronic neuropathic pain: a systematic review and meta-analysis

Chronic neuropathic pain (NP) is debilitating and impacts sleep health and quality of life. Treatment with gabapentinoids (GBs) has been shown to reduce pain, but its effects on sleep health have not been systematically evaluated. The objective of this systematic review and meta-analysis was to assess the relationship between GB therapy dose and duration on sleep quality, daytime somnolence, and intensity of pain in patients with NP. Subgroup comparisons were planned for high- vs low-dose GBs, where 300 mg per day or more of pregabalin was used to classify high-dose therapy. Trial data were segregated by duration less than 6 weeks and 6 weeks or greater. Twenty randomized controlled trials were included. Primary outcome measures included pain-related sleep interference and incidence of daytime somnolence. Secondary outcomes included daily pain scores (numerical rating scale 0-10) and patient global impression of change. Significant improvement in sleep quality was observed after 6 weeks of GB treatment when compared with placebo (standardized mean difference 0.39, 95% confidence interval 0.32-0.46 P < 0.001). Increased daytime somnolence was observed among all GB-treated groups when compared with placebo. Treated patients were also more likely to report improvement of patient global impression of change scores. Pain scores decreased significantly in patients both after 6 weeks of treatment (P < 0.001) and in trials less than 6 weeks (P = 0.017) when compared with placebo. Our data demonstrate that GBs have a positive impact on sleep health, quality of life, and pain in patients with NP syndromes. However, these benefits come at the expense of daytime somnolence.

State-of-the-art pharmacotherapy for diabetic neuropathy

INTRODUCTION

The global epidemic of diabetes has led to an epidemic of diabetes complications. Diabetic neuropathy is the most common microvascular complication, of which diabetic peripheral neuropathy (DPN) and autonomic neuropathy (AN) are the most prevalent, affecting ~50% of patients. DPN results in pain with a poor quality of life and a loss of sensation with an increased risk of foot ulceration. Autonomic neuropathy can cause significant morbidity in a minority and is associated with increased mortality. The cornerstone of treatment to prevent or limit the progression of DPN/AN is multifactorial risk factor modification including treatment of glycemia, lipids and blood pressure. Whilst, there are no FDA-approved disease-modifying therapies, there are a number of therapies to relieve symptoms in DPN and AN.

AREAS COVERED

The authors discuss current approved therapies for painful diabetic neuropathy and autonomic neuropathy. They also address the potential role of improving risk factors to limit the development and progression of diabetic neuropathy and new pathogenetic and pain-relieving treatments.

EXPERT OPINION

The FDA-approved Pregabalin and Duloxetine over 25 years ago and Tapentadol, 6 years ago for painful diabetic neuropathy. There are currently no FDA-approved disease-modifying treatments for diabetic neuropathy which has been attributed to inappropriate models of the disease with limited translational capacity and major limitations of trial designs and endpoints in clinical trials.

Diabetic Peripheral Neuropathy: Diagnosis and Treatment

BACKGROUND

Diabetic peripheral neuropathy (DPN) is traditionally divided into large and small fibre neuropathy (SFN). Damage to the large fibres can be detected using nerve conduction studies (NCS) and often results in a significant reduction in sensitivity and loss of protective sensation, while damage to the small fibres is hard to reliably detect and can be either asymptomatic, associated with insensitivity to noxious stimuli, or often manifests itself as intractable neuropathic pain.

OBJECTIVE

To describe the recent advances in both detection, grading, and treatment of DPN as well as the accompanying neuropathic pain.

METHODS

A review of relevant, peer-reviewed, English literature from MEDLINE, EMBASE and Cochrane Library between January 1st 1967 and January 1st 2020 was used.

RESULTS

We identified more than three hundred studies on methods for detecting and grading DPN, and more than eighty randomised-controlled trials for treating painful diabetic neuropathy.

CONCLUSION

NCS remains the method of choice for detecting LFN in people with diabetes, while a gold standard for the detection of SFN is yet to be internationally accepted. In the recent years, several methods with huge potential for detecting and grading this condition have become available including skin biopsies and corneal confocal microscopy, which in the future could represent reliable endpoints for clinical studies. While several newer methods for detecting SFN have been developed, no new drugs have been accepted for treating neuropathic pain in people with diabetes. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors and anticonvulsants remain first line treatment, while newer agents targeting the proposed pathophysiology of DPN are being developed.

Treatment of diabetic peripheral neuropathy: a review

OBJECTIVES

This review surveys current pharmacotherapies available for the treatment of diabetic peripheral neuropathy (DPN), emphasising their mechanisms of action.

METHODS

A comprehensive literature review focusing on the 'pharmacotherapy and treatment of diabetic peripheral neuropathy' was conducted. The Database of International Pharmaceutical Abstracts, EMBASE, PubMed, OVID, Scopus, Google and Google Scholar were searched, and reference lists of relevant articles were also included.

KEY FINDINGS

Diabetic peripheral neuropathy is often inadequately treated, and the role of improving glycaemic control specifically in type-2 diabetes remains unclear. It is crucial to explore the mechanisms of action and effectiveness of available therapies. Major international clinical guidelines for the management of DPN recommend several symptomatic treatments. First-line therapies include tricyclic antidepressants, serotonin-noradrenaline reuptake inhibitors, and anticonvulsants that act on calcium channels. Other therapies include opioids and topical agents such as capsaicin and lidocaine. The objectives of this paper are to review current guidelines for the pharmacological management of DPN and to discuss research relevant to the further development of pharmacological recommendations for the treatment of diabetic neuropathy.

SUMMARY

Diabetic neuropathy is a highly prevalent, disabling condition, the management of which is associated with significant costs. Evidence supports the use of specific anticonvulsants and antidepressants for pain management in patients with diabetic peripheral neuropathy. All current guidelines advise a personalised approach with a low-dose start that is tailored to the maximum response having the least side effects or adverse events.

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).

Pregabalin and gabapentin in neuropathic pain management after spinal cord injury: a systematic review and meta-analysis

Neuropathic pain after spinal cord injury (SCI) has a significant negative impact on the patients’ quality of life. The objective of this systematic review is to examine the safety and efficacy of pregabalin (PGB) and gabapentin (GBP) in the treatment of neuropathic pain due to SCI. PubMed, the Cochrane Library, Embase, Scopus, and the Web of Science were searched up to December 2018. The reference lists of key and review studies were reviewed for additional citations. The quality of the studies was evaluated using the Cochrane Collaboration’s tools for assessing the risk of bias. A meta-analysis was performed for primary and secondary outcomes. Eight studies were eligible for inclusion. Meta-analysis of PGB vs. placebo showed that PGB was effective for neuropathic pain (standardized mean difference [SMD] = −0.40; 95% confidence interval [CI]: −0.78, −0.01), anxiety (MD = −0.68; 95% CI: −0.77, −0.59), depression (mean difference [MD] = −0.99; 95% CI: −1.08, −0.89), and sleep interference (MD = −1.08; 95% CI: −1.13, −1.02). Also, GBP was more effective than a placebo for reducing pain. No significant difference was observed between the efficacy of the two drugs (MD = −0.37; 95% CI: −1.67, 0.93). There was no significant difference between the two drugs for discontinuation due to adverse events (risk ratio = 3.00; 95% CI: 0.81, 11.15). PGB and GBP were effective vs. placebos in decreasing neuropathic pain after SCI. Also, there was no significant difference between the two drugs for decreasing pain and adverse events.

Systematic review and network meta-analysis of the efficacy and safety of lidocaine 700 mg medicated plaster vs. pregabalin

Objective: Neuropathic pain prevalence is estimated between 7% and 10% of the population. International guidelines recommend a variety of drugs at different therapy lines for pain relief. However, side effect profiles, for example, prompted the UK government recently to classify pregabalin and gabapentin as class C drugs. Lidocaine 700 mg medicated plaster (LMP) might be a safer alternative. A systematic review assessed how LMP and pregabalin compared in terms of efficacy and safety. The review focused on pain reduction, quality of life and adverse events in peripheral neuropathic pain (PNP) i.e. post-herpetic neuralgia, diabetic peripheral neuropathy, post-surgical/trauma, or other PNP conditions.Methods: Electronic databases were searched as well as a number of other sources up to November 2018. Sensitive strategies were used, with no restriction by language or publication status. Two independent reviewers screened records and extracted data with consensus determining final decisions. Risk of bias was assessed using the Cochrane Collaboration 2011 checklist for RCTs. Full network meta-analysis was conducted to compare LMP to pregabalin 300/600 mg in terms of pain reduction, quality of life, as well as serious adverse events and selected adverse events. Trials with enriched enrolment design were excluded.Results: Searches retrieved 7,104 records. In total 111 references pertaining to 43 RCTs were included for data extraction. Bayesian network meta-analysis of several pain outcomes showed no clear difference in efficacy between treatments However, LMP was clearly advantageous in terms of dizziness and any adverse event vs. pregabalin 600 mg/day and discontinuations vs. pregabalin 300 mg/day or 600 mg/day, as well as being associated with improved quality of life (albeit in this case based on weak evidence).Conclusions: LMP was found to be similar to pregabalin in reducing pain in all populations but had a better adverse events profile.

Integrating Machine Learning With Microsimulation to Classify Hypothetical, Novel Patients for Predicting Pregabalin Treatment Response Based on Observational and Randomized Data in Patients With Painful Diabetic Peripheral Neuropathy

Purpose

Variability in patient treatment responses can be a barrier to effective care. Utilization of available patient databases may improve the prediction of treatment responses. We evaluated machine learning methods to predict novel, individual patient responses to pregabalin for painful diabetic peripheral neuropathy, utilizing an agent-based modeling and simulation platform that integrates real-world observational study (OS) data and randomized clinical trial (RCT) data.

Patients and methods

The best supervised machine learning methods were selected (through literature review) and combined in a novel way for aligning patients with relevant subgroups that best enable prediction of pregabalin responses. Data were derived from a German OS of pregabalin (N=2642) and nine international RCTs (N=1320). Coarsened exact matching of OS and RCT patients was used and a hierarchical cluster analysis was implemented. We tested which machine learning methods would best align candidate patients with specific clusters that predict their pain scores over time. Cluster alignments would trigger assignments of cluster-specific time-series regressions with lagged variables as inputs in order to simulate "virtual" patients and generate 1000 trajectory variations for given novel patients.

Results

Instance-based machine learning methods (k-nearest neighbor, supervised fuzzy c-means) were selected for quantitative analyses. Each method alone correctly classified 56.7% and 39.1% of patients, respectively. An "ensemble method" (combining both methods) correctly classified 98.4% and 95.9% of patients in the training and testing datasets, respectively.

Conclusion

An ensemble combination of two instance-based machine learning techniques best accommodated different data types (dichotomous, categorical, continuous) and performed better than either technique alone in assigning novel patients to subgroups for predicting treatment outcomes using microsimulation. Assignment of novel patients to a cluster of similar patients has the potential to improve prediction of patient outcomes for chronic conditions in which initial treatment response can be incorporated using microsimulation.

Clinical trial registries

www.clinicaltrials.gov: NCT00156078, NCT00159679, NCT00143156, NCT00553475.

The relationship between the reporting of euphoria events and early treatment responses to pregabalin: an exploratory post-hoc analysis

Background

Euphoria is a complex, multifactorial problem that is reported as an adverse event in clinical trials of analgesics including pregabalin. The relationship between the reporting of euphoria events and pregabalin early treatment responses was examined in this exploratory post-hoc analysis.

Methods

Data were from patients with neuropathic or non-neuropathic chronic pain enrolled in 40 randomized clinical trials, who received pregabalin (75–600 mg/day) or placebo. Reports of treatment-emergent euphoria events were based on the Medical Dictionary of Regulatory Activities preferred term “euphoric mood”. Prevalence rates of euphoria events overall and by indication were assessed. Post-treatment endpoints included ≥30% improvements in pain and sleep scores up to 3 weeks as well as a ≥1-point improvement in daily pain score up to 11 days after treatment.

Results

13,252 patients were analyzed; 8,501 (64.1%) and 4,751 (35.9%) received pregabalin and placebo, respectively. Overall, 1.7% (n=222) of patients reported euphoria events. Among pregabalin-treated patients, a larger proportion who reported euphoria events achieved an early pain response compared with those who did not report euphoria (30% pain responders in week 1 with euphoria events [43.0%], without euphoria events [24.2%]). Results were similar for weeks 2 and 3. For Days 2–11, a larger proportion of pregabalin-treated patients with (relative to without) euphoria events were 1-point pain responders. Findings were similar in pregabalin-treated patients for sleep endpoints (30% sleep responders in week 1 with euphoria events [50.7%], without euphoria events [36.1%]). Similar results were found for weeks 2 and 3. Patients who received placebo showed similar patterns, although the overall number of them who reported euphoria events was small (n=13).

Conclusion

In patients who received pregabalin for neuropathic or non-neuropathic chronic pain, those who experienced euphoria events may have better early treatment responses than those who did not report euphoria events.

The efficacy of pregabalin for the treatment of neuropathic pain in Japanese subjects with moderate or severe baseline pain

Purpose

Although analyses of pooled clinical trial data have reported how international populations respond to pregabalin by baseline neuropathic pain (NeP) severity, no studies have evaluated this specifically in patients from Japan. Thus, this post hoc pooled analysis evaluated the efficacy of pregabalin in Japanese subjects for treating moderate or severe baseline NeP.

Patients and methods

Data were pooled from three placebo-controlled trials enrolling Japanese subjects with postherpetic neuralgia (PHN), diabetic peripheral neuropathy (DPN), and spinal cord injury (SCI). The efficacy of pregabalin was evaluated by baseline pain severity (moderate or severe NeP). The trials on PHN and DPN included a 1-week titration of pregabalin from 150 mg/day to 300 or 600 mg/day; the SCI trial included a 4-week dose optimization phase (150 mg/day, titrated up to 600 mg/day). Treatment durations were 13–16 weeks (excluding 1-week taper periods), and pregabalin was administered in two divided doses per day.

Results

Mean baseline pain scores and demographic characteristics were comparable between treatment cohorts. Pregabalin treatment significantly reduced pain scores from baseline to endpoint compared with placebo in subjects with both moderate (P<0.001) and severe (P<0.05) baseline pain. Significant improvements in mean sleep scores from baseline to endpoint were associated with pregabalin compared with placebo in subjects with both moderate and severe baseline pain (both P<0.0001). A greater proportion of subjects in both pain cohorts achieved a ≥30% reduction in pain from baseline with pregabalin vs placebo (P<0.05). Higher proportions of pregabalin-treated vs placebo-treated subjects shifted to a less severe pain category at endpoint. Consistent with the known safety profile of pregabalin, common adverse events included dizziness, somnolence, weight gain, and peripheral edema.

Conclusion

Pregabalin demonstrated efficacy for pain relief and sleep improvement with a consistent safety profile in Japanese subjects with either moderate or severe baseline pain severity.

ClinicalTrials.gov identifiers

NCT0039490130, NCT0055347522, NCT0040774524

Evaluation of composite responder outcomes of pain intensity and physical function in neuropathic pain clinical trials: an ACTTION individual patient data analysis

Integrating information on physical function and pain intensity into a composite measure may provide a useful method for assessing treatment efficacy in clinical trials of chronic pain. Accordingly, we evaluated composite outcomes in trials of duloxetine, gabapentin, and pregabalin. Data on 2287 patients in 9 trials for painful diabetic peripheral neuropathy (DPN) and 1513 patients in 6 trials for postherpetic neuralgia (PHN) were analyzed. All trials assessed pain intensity on a 0 to 10 numeric rating scale and physical function with the 10-item subscale of the Short Form-36, ranging 0 to 100 with higher scores indicating better function. Correlation between change in pain intensity from baseline to posttreatment and change in physical function was small in DPN (ρ = -0.22; P < 0.001) and nonsignificant in PHN (ρ = -0.05; P = 0.08). Assay sensitivities of 10 composite outcomes were examined in a random subsample of patients enrolled in pregabalin trials for DPN and PHN. Of these, a responder outcome of ≥50% improvement in pain intensity, or a ≥20% improvement in pain intensity and ≥30% improvement in physical function was not only significantly associated with pregabalin vs placebo in the development cohorts for both pain conditions but also in the validation cohorts. Furthermore, this composite outcome was cross-validated in trials of gabapentin for PHN and duloxetine for DPN, and had slightly lower number needed to treat than a standard responder outcome of ≥50% reduction in pain intensity. In summary, this study identified a composite outcome of pain intensity and physical function that may improve the assay sensitivity of future neuropathic pain trials.

Pregabalin in the Management of Painful Diabetic Neuropathy: A Narrative Review

Pregabalin is a first-line treatment in all major international guidelines on the management of painful diabetic neuropathy (pDPN). Treatment with pregabalin leads to a clinically meaningful improvement in pain scores, offers consistent relief of pain and has an acceptable tolerance level. Despite its efficacy in relieving neuropathic pain, more robust methods and comprehensive studies are required to evaluate its effects in relation to co-morbid anxiety and sleep interference in pDPN. The sustained benefits of modulating pain have prompted further exploration of other potential target sites and the development of alternative GABAergic agents such as mirogabalin. This review evaluates the role of pregabalin in the management of pDPN as well as its potential adverse effects, such as somnolence and dizziness, which can lead to withdrawal in ~ 30% of long-term use. Recent concern about misuse and an increase in deaths linked to its use has led to demands for reclassification of pregabalin as a class C controlled substance in the UK. We believe these demands need to be tempered in relation to the difficulties it would create for repeat prescriptions for the many millions of patients with pDPN for whom pregabalin provides benefit.Plain Language Summary: Plain language summary available for this article.

Tricyclic Antidepressant and/or γ-Aminobutyric Acid-Analog Use Is Associated With Fall Risk in Diabetic Peripheral Neuropathy

BACKGROUND/OBJECTIVES

Peripheral neuropathy is a common diabetes complication that can increase fall risk. Regarding fall risk, the impact of pain management using tricyclic antidepressants (TCAs) or γ-aminobutyric acid (GABA) analogs is unclear because these medications can also cause falls. This study investigates the impact of these drugs on fall and fracture risk in older diabetic peripheral neuropathy (DPN) patients.

DESIGN

Historical cohort study with 1-to-1 propensity matching of TCA/GABA-analog users and nonusers.

SETTING

Nationally representative 5% Medicare sample between the years 2008 and 2010.

PARTICIPANTS

After applying all selection criteria, 5,550 patients with prescription and 22,200 patients without prescription of TCAs/GABA-analogs were identified. Both patient groups were then stratified for fall history and matched based on propensity of receiving TCAs/GABA-analogs within each group.

MEASUREMENTS

Patients were followed until the first incidence of fall or the first incidence of fracture during the follow-up period (for up to 5 years).

RESULTS

After matching, users and nonusers were largely similar. After covariate adjustment, TCA/GABA-analog use was associated with a statistically significant increase in fall risk (adjusted hazard ratio [HR] = 1.11; 95% confidence interval [CI] = 1.03-1.20), but was not associated with fracture risk (adjusted HR = 1.09; 95% CI = 0.99-1.19) in the conventional analysis. Treating TCA/GABA-analog use as a time-dependent covariate resulted in statistically significant associations of TCA/GABA-analog use with both fall and fracture risk (HR = 1.26 [95% CI = 1.17-1.36]; and HR = 1.12 [95% CI = 1.02-1.24], respectively).

CONCLUSION

Among older patients with DPN, GABA-analogs or TCAs increase fall risk and possibly fracture risk. Use of these medications is therefore a potentially modifiable risk factor for falls and fractures in this population.

Pregabalin for neuropathic pain in adults

BACKGROUND

This review updates part of an earlier Cochrane Review titled "Pregabalin for acute and chronic pain in adults", and considers only neuropathic pain (pain from damage to nervous tissue). Antiepileptic drugs have long been used in pain management. Pregabalin is an antiepileptic drug used in management of chronic pain conditions.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of pregabalin for chronic neuropathic pain in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase for randomised controlled trials from January 2009 to April 2018, online clinical trials registries, and reference lists.

SELECTION CRITERIA

We included randomised, double-blind trials of two weeks' duration or longer, comparing pregabalin (any route of administration) with placebo or another active treatment for neuropathic pain, with participant-reported pain assessment.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality and biases. Primary outcomes were: at least 30% pain intensity reduction over baseline; much or very much improved on the Patient Global Impression of Change (PGIC) Scale (moderate benefit); at least 50% pain intensity reduction; or very much improved on PGIC (substantial benefit). We calculated risk ratio (RR) and number needed to treat for an additional beneficial (NNTB) or harmful outcome (NNTH). We assessed the quality of the evidence using GRADE.

MAIN RESULTS

We included 45 studies lasting 2 to 16 weeks, with 11,906 participants - 68% from 31 new studies. Oral pregabalin doses of 150 mg, 300 mg, and 600 mg daily were compared with placebo. Postherpetic neuralgia, painful diabetic neuropathy, and mixed neuropathic pain predominated (85% of participants). High risk of bias was due mainly to small study size (nine studies), but many studies had unclear risk of bias, mainly due to incomplete outcome data, size, and allocation concealment.Postherpetic neuralgia: More participants had at least 30% pain intensity reduction with pregabalin 300 mg than with placebo (50% vs 25%; RR 2.1 (95% confidence interval (CI) 1.6 to 2.6); NNTB 3.9 (3.0 to 5.6); 3 studies, 589 participants, moderate-quality evidence), and more had at least 50% pain intensity reduction (32% vs 13%; RR 2.5 (95% CI 1.9 to 3.4); NNTB 5.3 (3.9 to 8.1); 4 studies, 713 participants, moderate-quality evidence). More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (62% vs 24%; RR 2.5 (95% CI 2.0 to 3.2); NNTB 2.7 (2.2 to 3.7); 3 studies, 537 participants, moderate-quality evidence), and more had at least 50% pain intensity reduction (41% vs 15%; RR 2.7 (95% CI 2.0 to 3.5); NNTB 3.9 (3.1 to 5.5); 4 studies, 732 participants, moderate-quality evidence). Somnolence and dizziness were more common with pregabalin than with placebo (moderate-quality evidence): somnolence 300 mg 16% versus 5.5%, 600 mg 25% versus 5.8%; dizziness 300 mg 29% versus 8.1%, 600 mg 35% versus 8.8%.Painful diabetic neuropathy: More participants had at least 30% pain intensity reduction with pregabalin 300 mg than with placebo (47% vs 42%; RR 1.1 (95% CI 1.01 to 1.2); NNTB 22 (12 to 200); 8 studies, 2320 participants, moderate-quality evidence), more had at least 50% pain intensity reduction (31% vs 24%; RR 1.3 (95% CI 1.2 to 1.5); NNTB 22 (12 to 200); 11 studies, 2931 participants, moderate-quality evidence), and more had PGIC much or very much improved (51% vs 30%; RR 1.8 (95% CI 1.5 to 2.0); NNTB 4.9 (3.8 to 6.9); 5 studies, 1050 participants, moderate-quality evidence). More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (63% vs 52%; RR 1.2 (95% CI 1.04 to 1.4); NNTB 9.6 (5.5 to 41); 2 studies, 611 participants, low-quality evidence), and more had at least 50% pain intensity reduction (41% vs 28%; RR 1.4 (95% CI 1.2 to 1.7); NNTB 7.8 (5.4 to 14); 5 studies, 1015 participants, low-quality evidence). Somnolence and dizziness were more common with pregabalin than with placebo (moderate-quality evidence): somnolence 300 mg 11% versus 3.1%, 600 mg 15% versus 4.5%; dizziness 300 mg 13% versus 3.8%, 600 mg 22% versus 4.4%.Mixed or unclassified post-traumatic neuropathic pain: More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (48% vs 36%; RR 1.2 (1.1 to 1.4); NNTB 8.2 (5.7 to 15); 4 studies, 1367 participants, low-quality evidence), and more had at least 50% pain intensity reduction (34% vs 20%; RR 1.5 (1.2 to 1.9); NNTB 7.2 (5.4 to 11); 4 studies, 1367 participants, moderate-quality evidence). Somnolence (12% vs 3.9%) and dizziness (23% vs 6.2%) were more common with pregabalin.Central neuropathic pain: More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (44% vs 28%; RR 1.6 (1.3 to 2.0); NNTB 5.9 (4.1 to 11); 3 studies, 562 participants, low-quality evidence) and at least 50% pain intensity reduction (26% vs 15%; RR 1.7 (1.2 to 2.3); NNTB 9.8 (6.0 to 28); 3 studies, 562 participants, low-quality evidence). Somnolence (32% vs 11%) and dizziness (23% vs 8.6%) were more common with pregabalin.Other neuropathic pain conditions: Studies show no evidence of benefit for 600 mg pregabalin in HIV neuropathy (2 studies, 674 participants, moderate-quality evidence) and limited evidence of benefit in neuropathic back pain or sciatica, neuropathic cancer pain, or polyneuropathy.Serious adverse events, all conditions: Serious adverse events were no more common with placebo than with pregabalin 300 mg (3.1% vs 2.6%; RR 1.2 (95% CI 0.8 to 1.7); 17 studies, 4112 participants, high-quality evidence) or pregabalin 600 mg (3.4% vs 3.4%; RR 1.1 (95% CI 0.8 to 1.5); 16 studies, 3995 participants, high-quality evidence).

AUTHORS' CONCLUSIONS

Evidence shows efficacy of pregabalin in postherpetic neuralgia, painful diabetic neuralgia, and mixed or unclassified post-traumatic neuropathic pain, and absence of efficacy in HIV neuropathy; evidence of efficacy in central neuropathic pain is inadequate. Some people will derive substantial benefit with pregabalin; more will have moderate benefit, but many will have no benefit or will discontinue treatment. There were no substantial changes since the 2009 review.

Benefits and harms of pregabalin in the management of neuropathic pain: a rapid review and meta-analysis of randomised clinical trials

OBJECTIVE

To assess the benefits and harms of pregabalin in the management of neuropathic pain.

DESIGN

Rapid review and meta-analysis of phase III, randomised, placebo-controlled trials.

PARTICIPANTS

Adults aged 18 years and above with neuropathic pain defined according to the International Association for the Study of Pain criteria.

INTERVENTIONS

Pregabalin or placebo.

PRIMARY AND SECONDARY OUTCOME MEASURES

Our primary outcomes were pain (as measured using validated scales) and adverse events. Our secondary outcomes were sleep disturbance, quality of life, Patient Global Impression of Change, Clinician Global Impression scale, anxiety and depression scores, overall discontinuations and discontinuations because of adverse events.

RESULTS

We included 28 trials comprising 6087 participants. The neuropathic pain conditions studied were diabetic peripheral neuropathy, postherpetic neuralgia, herpes zoster, sciatica (radicular pain), poststroke pain and spinal cord injury-related pain. Patients who took pregabalin reported significant reductions in pain (numerical rating scale (NRS)) compared with placebo (standardised mean difference (SMD) -0.49 (95% CI -0.66 to -0.32, p<0.00001), very low quality evidence). Pregabalin significantly reduced sleep interference scores (NRS) compared with placebo (SMD -0.38 (95% CI -0.50 to -0.26, p<0.00001), moderate quality evidence. Pregabalin significantly increased the risk of adverse events compared with placebo (RR 1.33 (95% CI 1.23 to 1.44, p<0.00001, low quality evidence)). The risks of experiencing weight gain, somnolence, dizziness, peripheral oedema, fatigue, visual disturbances, ataxia, non-peripheral oedema, vertigo and euphoria were significantly increased with pregabalin. Pregabalin was significantly more likely than placebo to lead to discontinuation of the drug because of adverse events (RR 1.91 (95% CI 1.54 to 2.37, p<0.00001), low quality evidence).

CONCLUSION

Pregabalin has beneficial effects on some symptoms of neuropathic pain. However, its use significantly increases the risk of a number of adverse events and discontinuation due to adverse events. The quality of the evidence from journal publications is low.

Using time series analysis approaches for improved prediction of pain outcomes in subgroups of patients with painful diabetic peripheral neuropathy

Prior work applied hierarchical clustering, coarsened exact matching (CEM), time series regressions with lagged variables as inputs, and microsimulation to data from three randomized clinical trials (RCTs) and a large German observational study (OS) to predict pregabalin pain reduction outcomes for patients with painful diabetic peripheral neuropathy. Here, data were added from six RCTs to reduce covariate bias of the same OS and improve accuracy and/or increase the variety of patients for pain response prediction. Using hierarchical cluster analysis and CEM, a matched dataset was created from the OS (N = 2642) and nine total RCTs (N = 1320). Using a maximum likelihood method, we estimated weekly pain scores for pregabalin-treated patients for each cluster (matched dataset); the models were validated with RCT data that did not match with OS data. We predicted novel ‘virtual’ patient pain scores over time using simulations including instance-based machine learning techniques to assign novel patients to a cluster, then applying cluster-specific regressions to predict pain response trajectories. Six clusters were identified according to baseline variables (gender, age, insulin use, body mass index, depression history, pregabalin monotherapy, prior gabapentin, pain score, and pain-related sleep interference score). CEM yielded 1766 patients (matched dataset) having lower covariate imbalances. Regression models for pain performed well (adjusted R-squared 0.90–0.93; root mean square errors 0.41–0.48). Simulations showed positive predictive values for achieving >50% and >30% change-from-baseline pain score improvements (range 68.6–83.8% and 86.5–93.9%, respectively). Using more RCTs (nine vs. the earlier three) enabled matching of 46.7% more patients in the OS dataset, with substantially reduced global imbalance vs. not matching. This larger RCT pool covered 66.8% of possible patient characteristic combinations (vs. 25.0% with three original RCTs) and made prediction possible for a broader spectrum of patients.

Trial Registration: www.clinicaltrials.gov (as applicable): NCT00156078, NCT00159679, NCT00143156, NCT00553475.

Prediction of therapeutic response to pregabalin in subjects with neuropathic pain

OBJECTIVE

To evaluate four models based on potential predictors for achieving a response to pregabalin treatment for neuropathic pain (NeP).

METHODS

In total, 46 pain studies were screened, of which 27 NeP studies met the criteria for inclusion in this analysis. Data were pooled from these 27 placebo-controlled randomized trials to assess if baseline characteristics (including mean pain and pain-related sleep interference [PRSI] scores), early clinical response during weeks 1-3 of treatment (change from baseline in pain and PRSI scores), and presence of treatment-emergent adverse events (AEs) were predictive of therapeutic response. Therapeutic response was defined as a ≥30% reduction from baseline in either pain and/or PRSI scores at week 5 with supplemental analyses to predict pain outcomes at weeks 8 and 12. Predictors of Patient Global Impression of Change (PGIC) were also evaluated. Four models were assessed: Random Forest, Logistic Regression, Naïve Bayes, and Partial Least Squares.

RESULTS

The number of pregabalin-treated subjects in the training/test datasets, respectively, were 2818/1407 (30% pain analysis), 2812/1405 (30% sleep analysis), and 2693/1345 (PGIC analysis). All four models demonstrated consistent results, and the most important predictors of treatment outcomes at week 5 and pain outcomes at weeks 8 and 12 were the reduction in pain score and sleep score in the first 1-3 weeks. The presence or absence of the most common AEs in the first 1-3 weeks was not correlated with any treatment outcome.

CONCLUSIONS

Subjects with an early response to pregabalin are more likely to experience an end-of-treatment response.

The efficacy of pregabalin for treating pain associated with diabetic peripheral neuropathy in subjects with type 1 or type 2 diabetes mellitus

OBJECTIVE

The objective of this study was to compare the efficacy and safety of pregabalin for painful diabetic peripheral neuropathy (pDPN) in subjects with type 1 (T1DM) or 2 diabetes mellitus (T2DM).

METHODS

Pooled data from 10 randomized clinical trials (pregabalin-treated T1DM and T2DM subjects with pDPN) were analyzed for change from baseline (CFB) scores (pain and sleep disturbance) using mixed model repeated measures (MMRM) through Week 12 and last observation carried forward (LOCF). Adverse events (AEs) were recorded.

RESULTS

Pregabalin-treated (T1DM 156 [8.7%]; T2DM 1632 [91.3%]) and placebo subjects (T1DM 92 [9.6%]; T2DM 868 [90.4%]) had comparable baseline demographic characteristics between treatment groups within the same diabetes type. T2DM (vs. T1DM) subjects were ∼10 years older. With pregabalin and placebo, respectively, mean ± SD baseline pain (T1DM: 6.2 ± 1.4 and 6.5 ± 1.6; T2DM: 6.5 ± 1.5 and 6.4 ± 1.5) and sleep scores (T1DM: 5.2 ± 2.4 and 5.2 ± 2.7; T2DM: 5.3 ± 2.5 and 5.1 ± 2.5) were comparable. Using MMRM, mean CFB treatment differences (pregabalin minus placebo) were significantly different for pain and sleep with either diabetes types (all weeks p < .05). With LOCF, pregabalin's odds ratios (ORs) of achieving 30% pain reduction were similar with T2DM (OR, 1.91, 95% CI [1.61, 2.27]) and T1DM (2.01 [1.18, 3.44]) (both p ≤ .01). Pregabalin's ORs of 30% improvement in sleep quality were 1.81 (95% CI, 1.06, 3.09) with T1DM and 2.01 (1.69, 2.39) with T2DM (both p < .05). AEs were consistent with the known safety profile of pregabalin.

CONCLUSIONS

Pregabalin significantly improved pain and sleep quality, without a clinically meaningful difference between diabetes types. ClinicalTrial.gov registration: NCT00156078, NCT00159679, NCT00143156, NCT00553475.

Predicting Responses to Pregabalin for Painful Diabetic Peripheral Neuropathy Based on Trajectory-Focused Patient Profiles Derived from the First 4 Weeks of Treatment

INTRODUCTION

Prediction of final clinical outcomes based on early weeks of treatment can enable more effective patient care for chronic pain. Our goal was to predict, with at least 90% accuracy, 12- to 13-week outcomes for pregabalin-treated painful diabetic peripheral neuropathy (pDPN) patients based on 4 weeks of pain and pain-related sleep interference data.

METHODS

We utilized active treatment data from six placebo-controlled randomized controlled trials (n = 939) designed to evaluate efficacy of pregabalin for reducing pain in patients with pDPN. We implemented a three-step, trajectory-focused analytics approach based upon patient responses collected during the first 4 weeks using monotonicity, path length, frequency domain (FD), and k-nearest neighbor (kNN) methods. The first two steps were based on combinations of baseline pain, pain at 4 weeks, weekly monotonicity and path length during the first 4 weeks, and assignment of patients to one of four responder groups (based on presence/absence of 50% or 30% reduction from baseline pain at 4 and at 12/13 weeks). The third step included agreement between prediction of logistic regression of daily FD amplitudes and assignment made from kNN analyses.

RESULTS

Step 1 correctly assigned 520/939 patients from the six studies to a responder group using a 3-metric combination approach based on unique assignment to a 50% responder group. Step 2 (applied to the remaining 419 patients) predicted an additional 121 patients, using a blend of 50% and 30% responder thresholds. Step 3 (using a combination of FD and kNN analyses) predicted 204 of the remaining 298 patients using the 50% responder threshold. Our approach correctly predicted 90.0% of all patients.

CONCLUSION

By correctly predicting 12- to 13-week responder outcomes with 90% accuracy based on responses from the first month of treatment, we demonstrated the value of trajectory measures in predicting pDPN patient response to pregabalin.

TRIAL REGISTRATION

www.clinicaltrials.gov identifiers, NCT00156078/NCT00159679/NCT00143156/NCT00553475.

FUNDING

Pfizer. Plain language summary available for this article.

Cerebral Biochemical Effect of Pregabalin in Patients with Painful Diabetic Neuropathy: A Randomized Controlled Trial

INTRODUCTION

With the development of new neuroimaging tools it has become possible to assess neurochemical alterations in patients experiencing chronic pain and to determine how these factors change during pharmacological treatment. The goal of this study was to examine the exact neurochemical mechanism underlying pregabalin treatment, utilizing magnetic resonance spectroscopy (¹H-MRS), in a population of patients with painful diabetic polyneuropathy (PDN), with the overall aim to ultimately objectify the clinical effect of pregabalin.

METHODS

A double blind, randomized, placebo-controlled study was conducted. A total of 27 patients with PDN were enrolled in the study, of whom 13 received placebo treatment (control group) and 14 received pregabalin (intervention group). Pregabalin treatment consisted of stepwise dose escalation over the study period from 75 mg daily ultimately to 600 mg daily. ¹H-MRS was performed at 3T on four regions of interest in the brain: the rostral anterior cingulate cortex (rACC), left and right thalamus and prefrontal cortex. The absolute concentrations of N-acetyl aspartate, glutamate, glutamine, gamma-amino-butyric-acid (GABA), glucose (Glc) and myo-inositol (mINS) were determined using LCModel.

RESULTS

The concentration of most neurometabolites in the placebo and pregabalin group did not significantly differ over time, with only a small significant difference in Glc level in the left thalamus (p = 0.049). Comparison of the effects of the different doses revealed significant differences for mINS in the rACC (baseline 2.42 ± 1.21 vs. 450 mg 1.58 ± 0.94; p = 0.022) and dorsolateral prefrontal cortex (75 mg 2.38 ± 0.89 vs. 450 mg 1.59 ± 0.85; p = 0.042) and also for GABA in the rACC (75 mg 0.53 ± 0.51 vs. 225 mg 0.28 ± 0.19; p = 0.014).

CONCLUSION

No differences were found in metabolite concentrations between the placebo (control) and intervention groups, but some differences, although small, were found between the different doses.

TRIAL REGISTRATION

This study is registered at ClinicalTrials.gov (NCT01180608).

FUNDING

Lyrica Independent Investigator Research Award (LIIRA) 2010 (Pfizer) funded the study.

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.

Efficacy and safety of pregabalin for painful diabetic peripheral neuropathy in a population of Chinese patients: A randomized placebo-controlled trial

BACKGROUND

Limited information exists regarding the efficacy of pregabalin in Chinese patients with painful diabetic peripheral neuropathy (pDPN).

METHODS

An 11-week double-blind placebo-controlled trial was performed in Chinese pDPN patients randomized (1 : 1) to 300 mg/day pregabalin or placebo. The primary outcome was change from baseline to endpoint in mean pain score (MPS; 0, no pain; 10, worst possible pain; using the mean of the last seven daily pain scores). Secondary outcomes included weekly MPS and responder status (MPS reduced by ≥30% or ≥50% vs baseline). Subgroup analysis assessed patients with severe (≥7) baseline MPS. Adverse events (AEs) were reported.

RESULTS

In all, 620 patients were randomized (pregabalin, n = 313; placebo, n = 307). Improvement in MPS with pregabalin versus placebo was not significant (P = 0.0559). Post hoc sensitivity analyses, excluding one patient/site due to Good Clinical Practice (GCP) non-compliance, showed pregabalin significantly improved MPS when excluding the patient (P = 0.0448) or site (P = 0.0142). Pregabalin significantly improved weekly MPS (P = 0.0164) and ≥50% responders at endpoint (P = 0.0384). Improvement in proportion of ≥30% responders, impression of change, pain intensity, and sleep did not differ significantly between the treatment groups. In the severe pDPN subpopulation, pregabalin significantly improved MPS versus placebo (P = 0.0040). The most commonly reported AE was dizziness (9.6% vs 3.9% with placebo).

CONCLUSIONS

Pregabalin did not significantly improve the primary measure of pain in the trial. Significant reductions in MPS were observed when excluding the GCP non-compliant patient/site and in the severe pDPN subpopulation. Pregabalin was well tolerated in Chinese pDPN patients.

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.

Impact of pregabalin on early phase post-thoracotomy pain compared with epidural analgesia

Background

The purpose of this randomized study was to compare the effects of pregabalin with epidural analgesia on early phase post-thoracotomy pain.

Methods

This study was conducted on 90 adult patients who underwent thoracotomy. Patients were randomly divided into two groups, an epidural analgesia group, where 45 patients received 0.2% ropivacaine hydrochloride and fentanyl through a thoracic epidural catheter, and a pregabalin group, where 45 patients received 75 mg pregabalin orally twice daily. Both groups were also administered orally with celecoxib along with each treatment. Numerical rating scale (NRS) and sleep interference rate (SIR) were evaluated on the first day, third day, and fifth day after surgery. Anesthetic induction time, operation time, recovery time, the use of additional analgesic drugs and adverse effects were also examined.

Results

NRS and SIR were significantly lower in the pregabalin group at all time points (P<0.05). The number of patients requiring additional analgesic drugs within 24 hours after surgery showed no difference between the two groups; however, the number was significantly decreased in the pregabalin group after post-operative day 1 (P<0.001). Adverse effects including pneumonia, dysuria, constipation and nausea were identified among many patients in the epidural analgesia group (P<0.05). Operation time and recovery time were the same for both groups, while the epidural analgesia group showed a significantly longer anesthetic induction time (P<0.001).

Conclusions

Pregabalin is considered to be a safe and effective treatment method which is an alternative to epidural analgesia for acute post-thoracotomy pain.

The Quest for more Research on Painful Diabetic Neuropathy

A 62-year-old diabetologist diagnosed himself to have diabetes type-2, with an HbA1c of 9.5. Five months after lifestyle intervention and a multi-drug approach, HbA1c was 6.3, systolic blood pressure was below 135mmHg and BMI reduced to 27. But he suffered from severe painful diabetic neuropathy. Therefore he decided to visit his friend, a famous neuroscientist at an even more famous university. He asked him several plain questions: 1. What is the natural course of painful diabetic neuropathy? 2. Why do I have, despite almost normalizing HbA1c, more problems than before? 3. Are you sure my problems are due to diabetes or should we do a nerve biopsy? 4. Are there imaging techniques helpful for the diagnosis of this diabetic complication, starting in the distal nerve endings of the foot and slowly moving ahead? 5. Can you suggest any drug, specific and effective, for relieving painful diabetic neuropathy? This review will use the experts' answers to the questions of the diabetologist, not only to give a summary of the current knowledge, but even more to highlight areas of research needed for improving the fate of patients with painful diabetic neuropathy. Based on the unknowns, which exceed the knowns in diabetic neuropathy, a quest for more public support of research is made.

Ultra-Low Doses of Naltrexone Enhance the Antiallodynic Effect of Pregabalin or Gabapentin in Neuropathic Rats

Preclinical Research Treatment of neuropathic pain is an area of largely unmet medical need. Pregabalin and gabapentin are anticonvulsants widely used for the treatment of neuropathic pain. Unfortunately, these drugs are only effective in 50-60% of the treated patients. In addition, both drugs have substantial side effects. Several studies have reported that ultralow doses of opioid receptor antagonists can induce analgesia and enhance the analgesic effect of opioids in rodents and humans. The objective of the present study was to assess the antiallodynic synergistic interaction between gabapentinoids and naltrexone in rats. Oral administration of pregabalin (ED₅₀  = 2.79 ± 0.16 mg/kg) or gabapentin (ED₅₀  = 21.04 ± 2.87 mg/kg) as well as intrathecal naltrexone (ED₅₀  = 0.11 ± 0.02 ng) reduced in a dose-dependent manner tactile allodynia in rats. Maximal antiallodynic effects (∼100%) were reached with 30 mg/kg of pregabalin, 300 mg/kg of gabapentin or 0.5 ng of naltrexone. Co-administration of pregabalin or gabapentin and naltrexone in a fixed-dose ratio (1:1) remarkably reduced spinal nerve ligation-induced tactile allodynia showing a synergistic interaction. The data indicate that combinations of pregabalin or gabapentin and ultra-low doses of naltrexone are able to reduce tactile allodynia in neuropathic rats with lower doses that those used when drugs are given individually and with an improved side effects profile. Drug Dev Res 78 : 371-380, 2017. © 2017 Wiley Periodicals, Inc.

Pregabalin for the treatment of neuropathic pain: a narrative review for primary care providers

BACKGROUND

Neuropathic pain (NeP) is a distinct type of pain caused by damage to the nervous system itself. This often severe and chronic type of pain requires specific treatments that target the underlying pain pathophysiology.

AIM

The purpose of the current narrative review is to provide an overview of pregabalin (Lyrica ¹ ) for the treatment of NeP including its effects on pain, pain-related sleep interference, and other health-related outcomes, timing of therapeutic effect, safety and tolerability, and dosing. The information provided here will help primary care providers develop more effective NeP treatment strategies.

Neuropathic pain responds better to increased doses of pregabalin: an in-depth analysis of flexible-dose clinical trials

Background

Pregabalin is an effective treatment option for many patients with neuropathic pain. Higher doses of pregabalin have been shown to be more effective in improving pain outcomes but, in practice, failing to appropriately increase the dose can leave patients under-treated.

Methods

This was a pooled analysis of 6 flexible-dose clinical trials of pregabalin in patients with neuropathic pain (diabetic peripheral neuropathy, peripheral herpetic neuralgia, posttraumatic pain, or postsurgical pain). Patients were divided into “dose pathway” groups based on their weekly pregabalin dose from the start of their trial to the first week of their maintenance phase. These were: 150 mg/day only; 150 to 300 mg/day; 150 to 300 to 450 mg/day; 150 to 300 to 450 to 600 mg/day; 150 to 300 to 600 mg/day; 300 to 600 mg/day. Pain outcomes assessed for each group at each new dose were proportion of 30% and 50% responders (≥30% or ≥50% reduction in mean pain score from baseline) and mean change in pain score. Percent change in mean pain score from baseline was assessed using a marginal structural model.

Results

Seven hundred and sixty-one patients treated with flexible-dose pregabalin were included in the analysis. For each dose pathway group, there was a notably greater proportion of 30% and 50% responders and change in pain score, at each escalating dose. As assessed by the marginal structural model, higher doses of pregabalin were estimated to result in a significantly greater change in mean pain score at each week. This dose response with flexible-dose pregabalin was consistent with that previously observed with fixed-dose pregabalin.

Conclusion

Many patients who do not respond to lower doses of pregabalin will respond with notable improvements in pain outcomes when the dose is escalated. These data should encourage physicians treating patients with neuropathic pain to escalate pregabalin to the dose that delivers optimal analgesia and tolerable side effects.

Effects of Pregabalin in Patients with Neuropathic Pain Previously Treated with Gabapentin: A Pooled Analysis of Parallel-Group, Randomized, Placebo-controlled Clinical Trials

OBJECTIVES

This analysis compared the therapeutic response of pregabalin in patients with neuropathic pain (NeP) who had been previously treated with gabapentin to the therapeutic response in patients who had not received gabapentin previously.

METHODS

Data were pooled from 18 randomized, double-blind, placebo-controlled trials of pregabalin in patients with NeP. Pregabalin-mediated changes in pain and pain-related sleep interference scores, patient global impression of change scores at endpoint, and the occurrence of adverse events were compared between patients who had received gabapentin previously (+GBN) and patients who had not received gabapentin previously (-GBN).

RESULTS

There were no significant differences between the -GBN and +GBN cohorts with regard to the extent of pain relief and relief of pain-related sleep interference for any dose of pregabalin (150, 300, 600, or 150 to 600 mg/day) at any time point (6, 8, or 12 weeks). Additionally, there was no significant difference in the distribution of patient global impression of change scores at study endpoint, or the occurrence of adverse events, between the -GBN and +GBN cohorts.

DISCUSSION

The findings presented here support the idea that pregabalin may be used successfully to treat patients with NeP who may be refractory, respond inadequately, or are intolerant to gabapentin. These findings highlight the importance of tailoring treatment of NeP based on individual patient response to different treatments, including the trial of multiple agents within the same mechanistic class.

Does Duration of Neuropathic Pain Impact the Effectiveness of Pregabalin?

BACKGROUND

Patients with chronic pain conditions such as neuropathic pain frequently experience delays in diagnosis and treatment. Ideally, all patients should be treated in a timely manner, but in those patients with more established disease it is important to know that approved treatments remain effective.

METHODS

This was a pooled analysis of 19 randomized placebo-controlled trials of pregabalin for peripheral neuropathic pain conditions, including diabetic peripheral neuropathy, postherpetic neuralgia, and post-traumatic/postsurgical pain. Patients were divided into 5 pain duration categories based on time since onset of pain (< 6 months, 6 months to < 1 year, 1 year to < 2 years, 2 years to < 5 years, and ≥ 5 years). Mean change in pain score at endpoint, vs. placebo, was assessed for each category, together with changes in Patient Global Impression of Change (PGIC) responders ("very much" or "much" improved at endpoint).

RESULTS

The analysis included 5,783 patients (n = 3,619 pregabalin; n = 2,164 placebo). Mean baseline pain scores were similar across the pain duration categories (range 6.3 to 6.5). Pregabalin significantly improved pain score at endpoint, vs. placebo, in all patients together (treatment difference [95% confidence interval], -0.59 [-0.67, -0.52], P < 0.0001) and similarly in each pain duration category (P < 0.0001 for each). There were significantly more PGIC responders with pregabalin, vs. placebo, for all patients (45.0% vs. 30.9%, P < 0.0001) and each category separately (P < 0.001 for each). There were no consistent, significant differences in treatment response between the different pain duration categories.

CONCLUSIONS

Pregabalin significantly improves pain irrespective of the length of time since onset of neuropathic pain.

Capsaicin 8% Patch Versus Oral Neuropathic Pain Medications for the Treatment of Painful Diabetic Peripheral Neuropathy: A Systematic Literature Review and Network Meta-analysis

PURPOSE

A network meta-analysis (NMA) was performed, aiming to assess the relative efficacy and tolerability of the capsaicin 179-mg (8% weight for weight) cutaneous patch (capsaicin 8% patch) compared with oral, centrally acting agents (ie, pregabalin, gabapentin, duloxetine, amitriptyline) in patients with painful diabetic peripheral neuropathy (PDPN).

METHODS

A systematic search of EMBASE/MEDLINE, Cochrane Library, and the National Health Service Centre for Reviews and Dissemination Database of Abstracts of Reviews of Effects was conducted to identify all randomized controlled trials. Data from eligible studies according to predefined inclusion and exclusion criteria were extracted, and analyses were based on aggregate-level data. Efficacy outcomes were the proportions of patients with ≥30% and ≥50% reductions in pain, and tolerability outcomes were somnolence, dizziness, nausea, diarrhea, constipation, headache, fatigue, insomnia, and rate of discontinuation due to adverse events (AEs). Data were analyzed by using a Bayesian NMA. Fixed and random effects models were estimated. Relative treatment effect was presented as odds ratios (ORs) with 95% CIs. Sources of heterogeneity were assessed.

FINDINGS

The NMA included 25 randomized controlled trials. For ≥30% pain reduction, the capsaicin 8% patch was significantly more effective than placebo (OR, 2.28 [95% CI, 1.19-4.03]), exhibited a numerical advantage compared with pregabalin (OR, 1.83 [95% CI, 0.91-3.34]) and gabapentin (OR, 1.66 [95% CI, 0.74-3.23]), and had similar efficacy compared with duloxetine (OR, 0.99 [95% CI, 0.5-1.79]). The evidence available was not sufficient to assess the relative efficacy of amitriptyline. In the NMA for tolerability, the capsaicin 8% patch was only included for headache because the incidence was 0% for the other outcomes. Oral, centrally acting agents had a significantly elevated risk compared with placebo for somnolence (pregabalin, gabapentin, duloxetine, and amitriptyline), dizziness (pregabalin, gabapentin, duloxetine, and amitriptyline), nausea (duloxetine), diarrhea (duloxetine), fatigue (duloxetine), and discontinuation because of AEs (pregabalin, gabapentin, and duloxetine). Compared with pregabalin and gabapentin, duloxetine had a significantly lower risk of dizziness but a significantly higher risk of nausea.

IMPLICATIONS

This NMA suggests that the efficacy observed with the capsaicin 8% patch is similar to that observed with oral agents (ie, pregabalin, duloxetine, gabapentin) in patients with PDPN. The oral agents were associated with a significantly elevated risk of somnolence, dizziness, fatigue, and discontinuation because of AEs compared with placebo. The capsaicin 8% patch was as effective as oral centrally acting agents in these patients with PDPN but offers systemic tolerability benefits.

Pharmacotherapy for diabetic peripheral neuropathy pain and quality of life: A systematic review

OBJECTIVE

To systematically assess the effect of pharmacologic treatments of diabetic peripheral neuropathy (DPN) on pain and quality of life.

METHODS

We searched PubMed and Cochrane Database of Systematic Reviews for systematic reviews from 2011 to October 12, 2015, and PubMed, Embase, and the Cochrane Central Register of Controlled Trials for primary studies from January 1, 2013, to May 24, 2016. We searched Clinicaltrials.gov on March 9, 2016. Two reviewers independently evaluated studies for eligibility, serially abstracted data, and independently evaluated risk of bias and graded strength of evidence (SOE).

RESULTS

We updated a recently completed systematic review of 57 eligible studies with 24 additional published studies and 25 unpublished studies. For reducing neuropathy-related pain, the serotonin-norepinephrine reuptake inhibitors duloxetine and venlafaxine (moderate SOE), the anticonvulsants pregabalin and oxcarbazepine (low SOE), the drug classes tricyclic antidepressants (low SOE) and atypical opioids (low SOE), and botulinum toxin (low SOE) were more effective than placebo. We could not draw conclusions about quality of life due to incomplete reporting. All studies were short-term (less than 6 months), and all effective drugs had more than 9% dropouts from adverse effects.

CONCLUSIONS

For reducing pain, duloxetine and venlafaxine, pregabalin and oxcarbazepine, tricyclic antidepressants, atypical opioids, and botulinum toxin were more effective than placebo. However, quality of life was poorly reported, studies were short-term, drugs had substantial dropout rates, and opioids have significant risks. Future studies should evaluate longer-term outcomes, use methods and measures recommended by pain organizations, and assess patients' quality of life.

Glycemic and serum lipid control in patients with painful diabetic peripheral neuropathy treated with pregabalin

AIM

To evaluate pregabalin effects on glycemic (hemoglobin A1c [HbA1c] and glucose) and lipid (low- and high-density lipoprotein [LDL and HDL, respectively], and total cholesterol, and triglycerides) control in patients with painful diabetic peripheral neuropathy (pDPN).

METHODS

Data from 11 randomized, double-blind trials were pooled to assess change-from-baseline treatment differences (pregabalin or placebo) in glycemic and lipid parameters using analysis of covariance.

RESULTS

Patients received pregabalin doses (mg/d) of 150 (n=176), 300 (n=559), 600 (n=705), 150-600 (flexible dose, n=521), or placebo (n=1050). Statistically significant mean [95% confidence interval] within-treatment (pregabalin) changes occurred in HDL (600mg/d: -1.61mg/dl [-3.17, -0.05]), total cholesterol (flexible dose: -6.03mg/dl [-11.68, -0.39]), and triglycerides (flexible dose: +15.39mg/dl [1.56, 29.23]). Statistically significant differences from placebo were found in HbA1c (300mg/d: +0.11% [0.01, 0.21]) and HDL cholesterol (300mg/d: -1.78mg/dl [-3.36, -0.19], 600mg/d: -2.53mg/dl [-4.49, -0.57]). No within- or between-treatment changes were large enough to be clinically meaningful.

CONCLUSION

No apparent clinically meaningful effects of pregabalin on glycemic/lipid control were found in patients with pDPN.