Enriched enrolment with randomised withdrawal (EERW): Time for a new look at clinical trial design in chronic pain

When does the placebo effect have an impact on network meta-analysis results?

The placebo effect is the 'effect of the simulation of treatment that occurs due to a participant's belief or expectation that a treatment is effective'. Although the effect might be of little importance for some conditions, it can have a great role in others, mostly when the evaluated symptoms are subjective. Several characteristics that include informed consent, number of arms in a study, the occurrence of adverse events and quality of blinding may influence response to placebo and possibly bias the results of randomised controlled trials. Such a bias is inherited in systematic reviews of evidence and their quantitative components, pairwise meta-analysis (when two treatments are compared) and network meta-analysis (when more than two treatments are compared). In this paper, we aim to provide red flags as to when a placebo effect is likely to bias pairwise and network meta-analysis treatment effects. The classic paradigm has been that placebo-controlled randomised trials are focused on estimating the treatment effect. However, the magnitude of placebo effect itself may also in some instances be of interest and has also lately received attention. We use component network meta-analysis to estimate placebo effects. We apply these methods to a published network meta-analysis, examining the relative effectiveness of four psychotherapies and four control treatments for depression in 123 studies.

Review of available data for the efficacy and effectiveness of nabiximols oromucosal spray (Sativex) in multiple sclerosis patients with moderate to severe spasticity

BACKGROUND

Sativex (USAN: nabiximols) oromucosal spray is indicated for treatment of multiple sclerosis (MS) patients with moderate to severe spasticity and inadequate response to other antispasticity medications who demonstrate clinically significant improvement during an initial trial of therapy. This narrative review investigated the efficacy and effectiveness of nabiximols oromucosal spray for moderate to severe MS spasticity by examining spasticity 010 Numerical Rating Scale (NRS) data from interventional and observational studies which featured a 4-week trial period as per the European Union approved label.

SUMMARY

Across both study types, clinically relevant and statistically significant reductions in mean MS spasticity 0-10 NRS scores were measured soon after treatment start and were maintained in the mid to long term in treatment responders. Initial responder rates (≥ 20% NRS improvement from baseline at week 4) ranged from 47.6% to 81.4%, tending lower in the randomized clinical trials setting. Clinically relevant responder rates (≥ 30% NRS improvement from baseline at week 12) were similar between study types (range 3041%) except for one outlier (74% in an observational study). Two open studies reported treatment continuation for ≥ 18 months in approximately half of patients who initiated treatment. In most longer-term studies, symptomatic improvement in MS spasticity was maintained at mean daily dosages of about 67 sprays/day. Safety was consistent with the known profile of nabiximols. Key messages: Experimental and observational studies of nabiximols oromucosal spray recorded similar findings. About half to two-thirds of MS patients who begin treatment will perceive initial symptomatic relief of spasticity within the 4-week trial period. About 40% of patients who initiate treatment will reach the ≥ 30% NRS improvement threshold at 3 months, comprising the majority of patients who continue long-term treatment. A trial of therapy with nabiximols is useful to identify patients most likely to gain longer-term improvement in spasticity symptoms and discontinue those with insufficient benefit.

The PATCH trial: efficacy and safety of 5% lidocaine-medicated plaster for the treatment of patients with trigeminal neuralgia: a study protocol for a multicentric, double-blind, enriched enrolment randomised withdrawal, vehicle-controlled study

INTRODUCTION

Trigeminal neuralgia (TN) is characterised by a sudden, severe, electric shock like paroxysmal pain, which is almost always associated with triggers. Carbamazepine is the first-line medical management of TN. However, side effects are common. Currently, there is no ideal treatment for TN. Since there is a known abnormality of Na+ channels in the trigger zone, 5% lidocaine-medicated plaster (LMP), which can block the Na+ channels on Aδ and C fibres, is an effective treatment method in many chronic pain conditions. A case report has found the benefit of LMP for the treatment of TN without any side effects. Whether LMP is an option for the treatment of TN is worth exploring.

METHODS AND ANALYSIS

The PATCH trial is a double-blind, enriched enrolment with randomised withdrawal, vehicle-controlled trial, aiming to explore the effects and safety of LMP in patients with TN. There is a 3-week initial open-label phase, followed by a 4-week double-blind treatment phase for responders. In the double-blind phase, patients will have to withdraw from this PATCH study if they meet one of the following criteria for treatment failure such as: >50% increase in pain intensity or paroxysms, lack of efficacy or side effects. The primary outcome will be the number of treatment failures. Adverse events will also be monitored throughout the study.

ETHICS AND DISSEMINATION

This study protocol has been approved by the Institutional Review Board of Beijing Tiantan Hospital (approval number: KY 2020-102-02). The results will be disseminated in international academic meetings and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04570293.

Estimands and missing data in clinical trials of chronic pain treatments: advances in design and analysis

In clinical trials of treatments for chronic pain, the percentage of participants who withdraw early can be as high as 50%. Major reasons for early withdrawal in these studies include perceived lack of efficacy and adverse events. Commonly used strategies for accommodating missing data include last observation carried forward, baseline observation carried forward, and more principled methods such as mixed-model repeated-measures and multiple imputation. All these methods require strong and untestable assumptions concerning the conditional distribution of outcomes after dropout, given the observed data. We review recent developments in statistical methods for handling missing data in clinical trials, including implications of the increased emphasis being placed on precise formulation of the study objectives and the estimand (treatment effect to be estimated) of interest. A flexible method that seems to be well suited for the analysis of chronic pain clinical trials is control-based imputation, which allows a variety of assumptions to be made concerning the conditional distribution of postdropout outcomes that can be tailored to the estimand of interest. These assumptions can depend, for example, on the stated reasons for dropout. We illustrate these methods using data from 4 clinical trials of pregabalin for the treatment of painful diabetic peripheral neuropathy and postherpetic neuralgia. When planning chronic pain clinical trials, careful consideration of the trial objectives should determine the definition of the trial estimand, which in turn should inform methods used to accommodate missing data in the statistical analysis.

Essential statistical principles of clinical trials of pain treatments

This article presents an overview of fundamental statistical principles of clinical trials of pain treatments. Statistical considerations relevant to phase 2 proof of concept and phase 3 confirmatory randomized trials investigating efficacy and safety are discussed, including (1) research design; (2) endpoints and analyses; (3) sample size determination and statistical power; (4) missing data and trial estimands; (5) data monitoring and interim analyses; and (6) interpretation of results. Although clinical trials of pharmacologic treatments are emphasized, the key issues raised by these trials are also directly applicable to clinical trials of other types of treatments, including biologics, devices, nonpharmacologic therapies (eg, physical therapy and cognitive-behavior therapy), and complementary and integrative health interventions.

[Method report of the second update of the guidelines on long-term opioid therapy for chronic noncancer pain]

BACKGROUND

The update of the German S3 guidelines on long-term opioid therapy of chronic noncancer pain (CNCP), the LONTS (AWMF registration number 145/003), was scheduled for February 2020 due to the expiry of the validity period.

METHODS

The guidelines were updated by 28 scientific societies and 2 patient self-help organizations under the coordination of the German Pain Society and the Association of the Scientific Medical Societies in Germany (AWMF).

RESULTS

A systematic literature search was performed in the CENTRAL, MEDLINE and Scopus databases from October 2013 to December 2018. The previous meta-analyses of randomized controlled trials (RCT) of opioids in CNPC syndromes with a study duration of ≥4 weeks were updated. Levels of evidence were assigned according to the Oxford Centre for Evidence-Based Medicine version 2009 classification system. The formulation and strength of recommendations was established in a multistep formalized consensus procedure, in accordance with AWMF rules and standards. The guidelines were reviewed by four experts not involved in the development of the guidelines. The public was given the opportunity to comment on the guidelines. The guidelines were approved by the executive boards of the societies that were engaged in development of the guidelines.

CONCLUSION

The guidelines will be published in several forms: complete and short scientific versions as well as clinical practice and patient versions.

Acupuncture for the Relief of Chronic Pain: A Synthesis of Systematic Reviews

Background and Objectives: It is estimated that 28 million people in the UK live with chronic pain. A biopsychosocial approach to chronic pain is recommended which combines pharmacological interventions with behavioural and non-pharmacological treatments. Acupuncture represents one of a number of non-pharmacological interventions for pain. In the current climate of difficult commissioning decisions and constantly changing national guidance, the quest for strong supporting evidence has never been more important. Although hundreds of systematic reviews (SRs) and meta-analyses have been conducted, most have been inconclusive, and this has created uncertainty in clinical policy and practice. There is a need to bring all the evidence together for different pain conditions. The aim of this review is to synthesise SRs of RCTs evaluating the clinical efficacy of acupuncture to alleviate chronic pain and to consider the quality and adequacy of the evidence, including RCT design. Materials and Methods: Electronic databases were searched for English language SRs and meta-analyses on acupuncture for chronic pain. The SRs were scrutinised for methodology, risk of bias and judgement of efficacy. Results: A total of 177 reviews of acupuncture from 1989 to 2019 met our eligibility criteria. The majority of SRs found that RCTs of acupuncture had methodological shortcomings, including inadequate statistical power with a high risk of bias. Heterogeneity between RCTs was such that meta-analysis was often inappropriate. Conclusions: The large quantity of RCTs on acupuncture for chronic pain contained within systematic reviews provide evidence that is conflicting and inconclusive, due in part to recurring methodological shortcomings of RCTs. We suggest that an enriched enrolment with randomised withdrawal design may overcome some of these methodological shortcomings. It is essential that the quality of evidence is improved so that healthcare providers and commissioners can make informed choices on the interventions which can legitimately be provided to patients living with chronic pain.

Checklist for the preparation and review of pain clinical trial publications: a pain-specific supplement to CONSORT

INTRODUCTION

Randomized clinical trials (RCTs) are considered the gold standard when assessing the efficacy of interventions because randomization of treatment assignment minimizes bias in treatment effect estimates. However, if RCTs are not performed with methodological rigor, many opportunities for bias in treatment effect estimates remain. Clear and transparent reporting of RCTs is essential to allow the reader to consider the opportunities for bias when critically evaluating the results. To promote such transparent reporting, the Consolidated Standards of Reporting Trials (CONSORT) group has published a series of recommendations starting in 1996. However, a decade after the publication of the first CONSORT guidelines, systematic reviews of clinical trials in the pain field identified a number of common deficiencies in reporting (e.g., failure to identify primary outcome measures and analyses, indicate clearly the numbers of participants who completed the trial and were included in the analyses, or report harms adequately).

METHODS

Qualitative review of a diverse set of published recommendations and systematic reviews that addressed the reporting of clinical trials, including those related to all therapeutic indications (e.g., CONSORT) and those specific to pain clinical trials.

RESULTS

A checklist designed to supplement the content covered in the CONSORT checklist with added details relating to challenges specific to pain trials or found to be poorly reported in recent pain trials was developed.

CONCLUSIONS

Authors and reviewers of analgesic RCTs should consult the CONSORT guidelines and this checklist to ensure that the issues most pertinent to pain RCTs are reported with transparency.

Randomized clinical trials with run-in periods: frequency, characteristics and reporting

Background

Run-in periods are occasionally used in randomized clinical trials to exclude patients after inclusion, but before randomization. In theory, run-in periods increase the probability of detecting a potential treatment effect, at the cost of possibly affecting external and internal validity. Adequate reporting of exclusions during the run-in period is a prerequisite for judging the risk of compromised validity. Our study aims were to assess the proportion of randomized clinical trials with run-in periods, to characterize such trials and the types of run-in periods and to assess their reporting.

Materials and methods

This was an observational study of 470 PubMed-indexed randomized controlled trial publications from 2014. We compared trials with and without run-in periods, described the types of run-in periods and evaluated the completeness of their reporting by noting whether publications stated the number of excluded patients, reasons for exclusion and baseline characteristics of the excluded patients.

Results

Twenty-five trials reported a run-in period (5%). These were larger than other trials (median number of randomized patients 217 vs 90, P=0.01) and more commonly industry trials (11% vs 3%, P<0.01). The run-in procedures varied in design and purpose. In 23 out of 25 trials (88%), the run-in period was incompletely reported, mostly due to missing baseline characteristics.

Conclusion

Approximately 1 in 20 trials used run-in periods, though much more frequently in industry trials. Reporting of the run-in period was often incomplete, precluding a meaningful assessment of the impact of the run-in period on the validity of trial results. We suggest that current trials with run-in periods are interpreted with caution and that updates of reporting guidelines for randomized trials address the issue.

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.

Treatment Recommendations Should Take Account of Individual Patient Variation Not Just Group Responses

Recommendations for treatment are commonly based on results evaluating variation in systematic effects (group responses) from randomised controlled trials without taking the individual patient's variation into account. In the evaluation of acupuncture-related treatment effects, the trial design and statistical analysis used are a challenge since the assessed variables commonly have subjective properties and are based on the person's own self-report. Thus, the results that are seen are often varied, most likely due to inter-individual variation in rating of the actual variable such that the treatment effects are expressed more (or less) in some individuals than in others. The basis for the individual variation is probably multi-modal and could be related to the individuals’ expectation, gender, genetic polymorphisms and the aetiology of the condition. The assessment methods used should preferably have proven useful in controlled trials, and the methods for statistical analysis should consider the non-metric properties of the variable and the contribution of the individuals’ variation in the results. In order to evaluate the treatment effects more properly and increase the possibility of detecting any effectiveness, it is therefore important to assess the level of perceived dysfunction or symptom, taking into account the individual variation as well as the systematic effects (the effects of the group). In the evaluation of acupuncture effects, both systematic and individual variation should be reported allowing for the detection of subgroup effects and thereby leading to treatment recommendations that are more likely to be based on each individual's specific needs.

Ea versus Sham Acupuncture and no Acupuncture for the Control of Acute and Delayed Chemotherapy-Induced Nausea and Vomiting: A Pilot Study

Objective

To assess the feasibility of undertaking a high-quality randomised controlled study to determine whether EA gives better control of delayed chemotherapy-induced nausea and vomiting (CINV) than sham EA or standard antiemetic treatment alone.

Methods

Patients having their first cycle of moderately or highly emetogenic chemotherapy were randomised to EA, sham EA or standard care. EA was given for 30 min on day 1 at the time of chemotherapy and on day 3 using standard acupuncture points bilaterally. Sham EA was given to points adjacent to true EA points. All patients received usual care, comprising antiemetics, according to hospital guidelines. The primary outcomes related to study feasibility, and the clinical outcome measure was the change in Functional Living Index Emesis (FLIE) score captured on days 1 and 7.

Results

153 participants were screened between April 2009 and May 2011. Eighteen patients did not meet the inclusion criteria, 37 declined to participate and the absence of an acupuncturist or lack of consent from the treating oncologist excluded a further 38 patients; 60 patients were recruited. The FLIE was completed on day 7 by 49 participants; 33 of 40 patients returned on day 3 for treatment. The nausea and vomiting scores were low in all three arms. Adverse events were generally mild and infrequent.

Conclusions

It was feasible to undertake a randomised EA trial on a busy day oncology unit. As few patients experienced nausea with their first cycle of chemotherapy, it was not possible to determine whether EA improves CINV over standard care. An enriched enrolment strategy is indicated for future studies. A simple numerical rating scale may prove a better objective nausea measure than the FLIE.

Trial Registration Number

ACTRN12609001054202.

The MOBILE Study-A Phase IIa Enriched Enrollment Randomized Withdrawal Trial to Assess the Analgesic Efficacy and Safety of ASP8477, a Fatty Acid Amide Hydrolase Inhibitor, in Patients with Peripheral Neuropathic Pain

Objective

To evaluate the analgesic efficacy and safety of ASP8477 in patients with peripheral neuropathic pain (PNP).

Design

Enriched enrollment randomized withdrawal.

Setting

Centers in Poland (four), Czech Republic (six), and the United Kingdom (two).

Subjects

Patients aged 18 years or older with PNP resulting from painful diabetic peripheral neuropathy or postherpetic neuralgia.

Methods

A four-week screening period followed by a single-blind period (six-day dose titration and three-week maintenance period with ASP8477 [20/30 mg BID]). Treatment responders (defined as a ≥30% decrease in the mean average daily pain intensity during the last three days of the single-blind period) were stratified by disease and randomized to receive placebo or continue ASP8477 during a three-week, double-blind, randomized withdrawal period. The primary end point was change in mean 24-hour average numeric pain rating scale (NPRS) from baseline to end of double-blind period.

Results

Among 132 patients who enrolled, 116 entered the single-blind period and 63 (ASP8477, N = 31; placebo, N = 32) completed the double-blind period. There was no difference in mean 24-hour average NPRS score (P = 0.644) or in time-to-treatment failure (P = 0.485) between ASP8477 and placebo. During the single-blind period, 57.8% of patients were treatment responders. ASP8477 was well tolerated. During the single-blind period, 22% of patients experienced at least one treatment-related adverse event (TEAE); during the double-blind period, 8% in the ASP8477 arm and 18% in the placebo arm experienced at least one TEAE.

Conclusions

ASP8477 was well tolerated in patients with PNP; however, ASP8477 did not demonstrate a significant treatment difference compared with placebo.

The research gap in chronic paediatric pain: A systematic review of randomised controlled trials

BACKGROUND AND OBJECTIVE

Chronic pain is associated with significant functional and social impairment. The objective of this review was to assess the characteristics and quality of randomized controlled trials (RCTs) evaluating pain management interventions in children and adolescents with chronic pain.

METHODS

We performed a systematic search of PubMed, Embase and the Cochrane Library up to July 2017. We included RCTs that involved children and adolescents (3 months-18 years) and evaluated the use of pharmacological or non-pharmacological intervention(s) in the context of pain persisting or re-occurring for more than 3 months. Methodological quality was evaluated using the Cochrane Risk of Bias (ROB) Tool.

RESULTS

A total of 58 RCTs were identified and numbers steadily increased over time. The majority were conducted in single hospital institutions, with no information on study funding. Median sample size was 47.5 participants (Q1,Q3: 32, 70). Forty-five percent of RCTs included both adults and children and the median of the mean ages at inclusion was 12.9 years (Q1,Q3: 11, 15). Testing of non-pharmacological interventions was predominant and only 5 RCTs evaluated analgesics or co-analgesics. Abdominal pain, headache/migraine and musculoskeletal pain were the most common types of chronic pain among participants. Methodological quality was poor with 90% of RCTs presenting a high or unclear ROB.

CONCLUSIONS

Evaluation of analgesics targeting chronic pain relief in children and adolescents through RCTs is marginal. Infants and children with long-lasting painful conditions are insufficiently represented in RCTs. We discuss possible research constraints and challenges as well as methodologies to circumvent them.

SIGNIFICANCE

There is a substantial research gap regarding analgesic interventions for children and adolescents with chronic pain. Most clinical trials in the field focus on the evaluation of non-pharmacological interventions and are of low methodological quality. There is also a specific lack of trials involving infants and children and adolescents with long-lasting diseases.

Methods for assessing and controlling placebo effects

The placebo serves as an indispensable control in many randomized trials. When analyzing the benefit of a new treatment, researchers are often confronted with large placebo effects that diminish the treatment effect. Various alternative methods have been proposed for analyzing placebo and treatment effects in studies where large placebo effects are expected or have already occurred. This paper presents an overview of methodological work that has been proposed for assessing and/or controlling for placebo effects in randomized trials. Throughout this paper, two main approaches are discussed. The first approach considers designs that represent alternatives to the classical placebo-controlled randomized trial design. Separately, the second approach considers adopting new methods for the statistical analysis of placebo and treatment effects to be implemented after the data have been collected using a classical randomized trial design.

Comparison of effect sizes between enriched and nonenriched trials of analgesics for chronic musculoskeletal pain: a systematic review

AIMS

To investigate the use of an enriched study design on the estimates of treatment effect in analgesic trials for chronic musculoskeletal pain.

METHODS

Database searches were conducted from 2004 to 2014. We included randomized placebo-controlled trials evaluating pain medications for chronic musculoskeletal pain. Methodological quality was assessed using the PEDro scale. The estimates of treatment effect on pain and adverse events were compared between enriched and nonenriched designs. Metaregression was used to assess the association between the effect size estimate and the study design controlling for analgesic dose and methodological quality.

RESULTS

We included 108 trials, of which 99 were included in the meta-analysis (n = 44 171). There were no overall differences in effect sizes between enriched and nonenriched designs for pain intensity. There was a significant difference for a reduction in any adverse events favouring enriched designs for opioids, but not for other analgesics or the outcome serious adverse events. There was an association between effect size and methodological quality, with failure to blind the outcome assessor and failure to use intention-to-treat analysis being associated with larger effect sizes.

CONCLUSIONS

There is no evidence that the use of an enriched study design changes the treatment effect size estimate for pain. There is some evidence that clinical trials that employ enriched designs report a reduced risk of adverse events in trials for chronic musculoskeletal pain, but it is unclear whether enriched designs influence estimates of serious adverse events. Features of trial design and study quality were associated with treatment effect estimates.

Gabapentin for chronic neuropathic pain in adults

BACKGROUND

Gabapentin is commonly used to treat neuropathic pain (pain due to nerve damage). This review updates a review published in 2014, and previous reviews published in 2011, 2005 and 2000.

OBJECTIVES

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

SEARCH METHODS

For this update we searched CENTRAL), MEDLINE, and Embase for randomised controlled trials from January 2014 to January 2017. We also searched the reference lists of retrieved studies and reviews, and online clinical trials registries.

SELECTION CRITERIA

We included randomised, double-blind trials of two weeks' duration or longer, comparing gabapentin (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 potential bias. Primary outcomes were participants with substantial pain relief (at least 50% pain relief over baseline or very much improved on Patient Global Impression of Change scale (PGIC)), or moderate pain relief (at least 30% pain relief over baseline or much or very much improved on PGIC). We performed a pooled analysis for any substantial or moderate benefit. Where pooled analysis was possible, we used dichotomous data to calculate risk ratio (RR) and number needed to treat for an additional beneficial outcome (NNT) or harmful outcome (NNH). We assessed the quality of the evidence using GRADE and created 'Summary of findings' tables.

MAIN RESULTS

We included four new studies (530 participants), and excluded three previously included studies (126 participants). In all, 37 studies provided information on 5914 participants. Most studies used oral gabapentin or gabapentin encarbil at doses of 1200 mg or more daily in different neuropathic pain conditions, predominantly postherpetic neuralgia and painful diabetic neuropathy. Study duration was typically four to 12 weeks. Not all studies reported important outcomes of interest. High risk of bias occurred mainly due to small size (especially in cross-over studies), and handling of data after study withdrawal.In postherpetic neuralgia, more participants (32%) had substantial benefit (at least 50% pain relief or PGIC very much improved) with gabapentin at 1200 mg daily or greater than with placebo (17%) (RR 1.8 (95% CI 1.5 to 2.1); NNT 6.7 (5.4 to 8.7); 8 studies, 2260 participants, moderate-quality evidence). More participants (46%) had moderate benefit (at least 30% pain relief or PGIC much or very much improved) with gabapentin at 1200 mg daily or greater than with placebo (25%) (RR 1.8 (95% CI 1.6 to 2.0); NNT 4.8 (4.1 to 6.0); 8 studies, 2260 participants, moderate-quality evidence).In painful diabetic neuropathy, more participants (38%) had substantial benefit (at least 50% pain relief or PGIC very much improved) with gabapentin at 1200 mg daily or greater than with placebo (21%) (RR 1.9 (95% CI 1.5 to 2.3); NNT 5.9 (4.6 to 8.3); 6 studies, 1277 participants, moderate-quality evidence). More participants (52%) had moderate benefit (at least 30% pain relief or PGIC much or very much improved) with gabapentin at 1200 mg daily or greater than with placebo (37%) (RR 1.4 (95% CI 1.3 to 1.6); NNT 6.6 (4.9 to 9.9); 7 studies, 1439 participants, moderate-quality evidence).For all conditions combined, adverse event withdrawals were more common with gabapentin (11%) than with placebo (8.2%) (RR 1.4 (95% CI 1.1 to 1.7); NNH 30 (20 to 65); 22 studies, 4346 participants, high-quality evidence). Serious adverse events were no more common with gabapentin (3.2%) than with placebo (2.8%) (RR 1.2 (95% CI 0.8 to 1.7); 19 studies, 3948 participants, moderate-quality evidence); there were eight deaths (very low-quality evidence). Participants experiencing at least one adverse event were more common with gabapentin (63%) than with placebo (49%) (RR 1.3 (95% CI 1.2 to 1.4); NNH 7.5 (6.1 to 9.6); 18 studies, 4279 participants, moderate-quality evidence). Individual adverse events occurred significantly more often with gabapentin. Participants taking gabapentin experienced dizziness (19%), somnolence (14%), peripheral oedema (7%), and gait disturbance (14%).

AUTHORS' CONCLUSIONS

Gabapentin at doses of 1800 mg to 3600 mg daily (1200 mg to 3600 mg gabapentin encarbil) can provide good levels of pain relief to some people with postherpetic neuralgia and peripheral diabetic neuropathy. Evidence for other types of neuropathic pain is very limited. The outcome of at least 50% pain intensity reduction is regarded as a useful outcome of treatment by patients, and the achievement of this degree of pain relief is associated with important beneficial effects on sleep interference, fatigue, and depression, as well as quality of life, function, and work. Around 3 or 4 out of 10 participants achieved this degree of pain relief with gabapentin, compared with 1 or 2 out of 10 for placebo. Over half of those treated with gabapentin will not have worthwhile pain relief but may experience adverse events. Conclusions have not changed since the previous update of this review.

A Phase II Randomized, Double-Blind, Placebo-Controlled Safety and Efficacy Study of Lenalidomide in Lumbar Radicular Pain with a Long-Term Open-Label Extension Phase

Objective

This phase II study assessed lenalidomide efficacy and safety.

Design

Three-phase core study: 14-day prerandomization, 12-week treatment, and 52-week open-label extension.

Setting

Fourteen US centers from July 2005 to July 2007.

Subjects

Chronic lumbar radicular pain patients without history of nerve injury or deficit.

Methods

Subjects were randomized (1:1) to double-blind treatment with lenalidomide 10 mg or placebo once daily for 12 weeks, followed by a 52-week open-label extension. A 12-week, single-center, randomized-withdrawal (1:2, lenalidomide:placebo), exploratory study with open-label extension was undertaken in 12 subjects from the core extension who were naïve to neuropathic medications and with at least a two-point decrease from baseline average daily Pain Intensity-Numerical Rating Scale score.

Results

Of 180 subjects enrolled, 176 had at least one postbaseline measure; 132 completed the 12-week treatment phase. In the core study, no statistically significant difference in Pain Intensity-Numerical Rating Scale mean change (-0.02, P  =   0.958) was observed at week 12 between lenalidomide and placebo; proportions achieving pain reduction at week 12 and other secondary measures were comparable between lenalidomide and placebo. In the exploratory study, week 12 mean changes in Pain Intensity-Numerical Rating Scale scores were -0.05 (lenalidomide: N = 3) and 2.11 (placebo: N = 8). Mean changes in Brief Pain Inventory-short form interference scores were -3.33 and 8.38, respectively; scores at six months were maintained or decreased in 10 of 12 subjects.

Conclusions

While this study does not support lenalidomide use in an unselected lumbar radicular pain population, an immunomodulating agent may relieve pain in select subjects naïve to neuropathic pain medications.

ClinicalTrials.gov identifier: NCT00120120.

Realising stratified psychiatry using multidimensional signatures and trajectories

Background

Stratified or personalised medicine targets treatments for groups of individuals with a disorder based on individual heterogeneity and shared factors that influence the likelihood of response. Psychiatry has traditionally defined diagnoses by constellations of co-occurring signs and symptoms that are assigned a categorical label (e.g. schizophrenia). Trial methodology in psychiatry has evaluated interventions targeted at these categorical entities, with diagnoses being equated to disorders. Recent insights into both the nosology and neurobiology of psychiatric disorder reveal that traditional categorical diagnoses cannot be equated with disorders. We argue that current quantitative methodology (1) inherits these categorical assumptions, (2) allows only for the discovery of average treatment response, (3) relies on composite outcome measures and (4) sacrifices valuable predictive information for stratified and personalised treatment in psychiatry.

Methods and findings

To achieve a truly ‘stratified psychiatry’ we propose and then operationalise two necessary steps: first, a formal multi-dimensional representation of disorder definition and clinical state, and second, the similar redefinition of outcomes as multidimensional constructs that can expose within- and between-patient differences in response. We use the categorical diagnosis of schizophrenia—conceptualised as a label for heterogeneous disorders—as a means of introducing operational definitions of stratified psychiatry using principles from multivariate analysis. We demonstrate this framework by application to the Clinical Antipsychotic Trials of Intervention Effectiveness dataset, showing heterogeneity in both patient clinical states and their trajectories after treatment that are lost in the traditional categorical approach with composite outcomes. We then systematically review a decade of registered clinical trials for cognitive deficits in schizophrenia highlighting existing assumptions of categorical diagnoses and aggregate outcomes while identifying a small number of trials that could be reanalysed using our proposal.

Conclusion

We describe quantitative methods for the development of a multi-dimensional model of clinical state, disorders and trajectories which practically realises stratified psychiatry. We highlight the potential for recovering existing trial data, the implications for stratified psychiatry in trial design and clinical treatment and finally, describe different kinds of probabilistic reasoning tools necessary to implement stratification.

[Methodology of the development of the updated LONTS guidelines for long-term administration of opioids in noncancer pain]

BACKGROUND

The update of the German S3 guidelines on long-term opioid therapy of chronic noncancer pain (CNCP), the"LONTS" (AWMF registration number 145/003) was scheduled for May 2014.

METHODS

The guidelines were developed by 25 scientific societies and two patient self-help organizations under the coordination of the German Pain Society and the Association of the Scientific Medical Societies in Germany (AWMF).

RESULTS

A systematic literature search was performed in the CENTRAL, MEDLINE and Scopus databases from October 2008 to October 2013. Meta-analyses of randomized controlled trials (RCT) of opioids in CNPC of study duration ≥ 4 weeks were conducted. Levels of evidence were assigned according to the Oxford Centre for Evidence-Based Medicine version 2009 classification system. The formulation and strength of recommendations was established in a multistep formalized consensus procedure, in accordance with AWFM rules and standards. The guidelines were reviewed by three scientific societies not involved in their development and were approved by the executive boards of the societies that were engaged in development of the guidelines.

CONCLUSION

The guidelines will be published in several forms: complete and short scientific versions, as well as clinical practice and patient versions.

Pregabalin for pain in fibromyalgia in adults

BACKGROUND

This review updates part of an earlier Cochrane review on 'Pregabalin for acute and chronic pain in adults' (Moore 2009), and considers only fibromyalgia pain.Antiepileptic drugs have been used in pain management since the 1960s. Pregabalin is an antiepileptic drug also used in management of chronic pain conditions, including fibromyalgia. Pain response with pregabalin is associated with major benefits for other symptoms, and improved quality of life and function in people with chronic painful conditions.

OBJECTIVES

To assess the analgesic efficacy and adverse events of pregabalin for pain in fibromyalgia in adults, compared with placebo or any active comparator.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE for randomised controlled trials from inception to May 2009 for the original review and to 16 March 2016 for this update. We also searched the reference lists of retrieved studies and reviews, and online clinical trial registries.

SELECTION CRITERIA

We included randomised, double-blind trials of eight weeks' duration or longer, comparing pregabalin with placebo or another active treatment for relief of pain in fibromyalgia, and reporting on the analgesic effect of pregabalin, with subjective pain assessment by the participant.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality and potential bias. Primary outcomes were participants with moderate pain relief (at least 30% pain relief over baseline or much or very much improved on Patient Global Impression of Change scale (PGIC)) or substantial pain relief (at least 50% pain relief over baseline or very much improved on PGIC). Where pooled analysis was possible, we used dichotomous data to calculate risk ratio and number needed to treat (NNT), using standard methods. We assessed the quality of the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation) and created 'Summary of findings' tables.

MAIN RESULTS

Our searches identified two new published studies with classic design, and one new published study with an enriched enrolment randomised withdrawal (EERW) design.We included eight studies. Five (3283 participants) had a classic design in which participants were randomised at the start of the study to pregabalin (150, 300, 450, or 600 mg daily) or placebo, with assessment after 8 to 13 weeks of stable treatment. No studies included active comparators. Studies had low risk of bias, except that the last observation carried forward (LOCF) imputation method used in analyses of the primary outcomes could overestimate treatment effect.Pregabalin increased the number of participants experiencing substantial benefit (at least 50% pain intensity reduction after 12 or 13 weeks' stable treatment (450 mg: RR 1.8, 95% CI 1.4 to 2.1, 1874 participants, 5 studies, high quality evidence)). Substantial benefit with pregabalin 300 to 600 mg was experienced by about 14% of participants with placebo, but about 9% more with pregabalin 300 to 600 mg (22% to 24%) (high quality evidence). Pregabalin increased the number of participants experiencing moderate benefit (at least 30% pain intensity reduction after 12 or 13 weeks' stable treatment) (450 mg: RR 1.5, 95% CI (1.3 to 1.7), 1874 participants, 5 studies, high quality evidence). Moderate benefit with pregabalin 300 to 600 mg was experienced by about 28% of participants with placebo, but about 11% more with pregabalin 300 to 600 mg (39% to 43%) (high quality evidence). A similar magnitude of effect was found using PGIC of 'very much improved' and 'much or very much improved'. NNTs for these outcomes ranged between 7 and 14 (high quality evidence).A small study (177 participants) compared nightly with twice-daily pregabalin, and concluded there was no difference in effect.Two studies (1492 participants began initial dose titration, 687 participants randomised) had an EERW design in which those with good pain relief after titration were randomised, double blind, to continuing the effective dose (300 to 600 mg pregabalin daily) or a short down-titration to placebo for 13 or 26 weeks. We calculated the outcome of maintained therapeutic response (MTR) without withdrawal, equivalent to a moderate benefit. Of those randomised, 40% had MTR with pregabalin and 20% with placebo (high quality evidence). The NNT was 5, but normalised to the starting population tested it was 12. About 10% of the initial population would have achieved the MTR outcome, similar to the result from studies of classic design. MTR had no imputation concerns.The majority (70% to 90%) of participants in all treatment groups experienced adverse events. Specific adverse events were more common with pregabalin than placebo, in particular dizziness, somnolence, weight gain, and peripheral oedema, with number needed to harm of 3.7, 7.4, 18, and 19 respectively for all doses combined (high quality evidence). Serious adverse events did not differ between active treatment groups and placebo (very low quality evidence). Withdrawals for any reason were more common with pregabalin than placebo only with the 600 mg dose in studies of classic design. Withdrawals due to adverse events were about 10% higher with pregabalin than placebo, but withdrawals due to lack of efficacy were about 6% lower (high quality evidence).

AUTHORS' CONCLUSIONS

Pregabalin 300 to 600 mg produces a major reduction in pain intensity over 12 to 26 weeks with tolerable adverse events for a small proportion of people (about 10% more than placebo) with moderate or severe pain due to fibromyalgia. The degree of pain relief is known to be accompanied by improvements in other symptoms, quality of life, and function. These results are similar to other effective medicines in fibromyalgia (milnacipran, duloxetine).

A randomized double-blind, placebo-controlled efficacy and safety study of ALO-02 (extended-release oxycodone surrounding sequestered naltrexone) for moderate-to-severe chronic low back pain treatment

The objective of this multicenter, double-blind, placebo-controlled, randomized withdrawal study was to evaluate the efficacy and safety of ALO-02, an abuse-deterrent formulation containing pellets of extended-release oxycodone hydrochloride (HCl) surrounding sequestered naltrexone HCl, compared with placebo in the treatment of moderate-to-severe chronic low back pain. An open-label titration period in which all patients received ALO-02 was followed by a double-blind treatment period where patients meeting treatment response criteria were randomized to either a fixed dose of ALO-02 or placebo. Daily average low back pain was assessed using an 11-point numeric rating scale (NRS)-Pain. Of the 663 patients screened, 410 received ALO-02 during the open-label conversion and titration period and 281 patients were randomized to the double-blind treatment period (n = 134, placebo; n = 147, ALO-02). Change in the mean NRS-Pain score from randomization baseline to the final 2 weeks of the treatment period was significantly different favoring ALO-02 compared with placebo (P = 0.0114). Forty-four percent of patients treated with placebo and 57.5% of patients treated with ALO-02 reported ≥30% improvement in weekly average NRS-Pain scores from screening to the final 2 weeks of the treatment period (P = 0.0248). In the double-blind treatment period, 56.8% of patients in the ALO-02 group and 56.0% of patients in the placebo group experienced a treatment-emergent adverse event (TEAE). The most common treatment-related TEAEs for ALO-02 during the treatment period were nausea, vomiting, and constipation, consistent with opioid therapy. ALO-02 has been demonstrated to provide significant reduction of pain in patients with chronic low back pain and has a safety profile similar to other opioids.

Systematic review of enriched enrolment, randomised withdrawal trial designs in chronic pain: a new framework for design and reporting

Enriched enrolment, randomised withdrawal (EERW) pain trials select, before randomisation, patients who respond by demonstrating a predetermined degree of pain relief and acceptance of adverse events. There is uncertainty over the value of this design. We report a systematic review of EERW trials in chronic noncancer pain together with a critical appraisal of methods and potential biases in the methods used and recommendations for the design and reporting of future EERW trials. Electronic and other searches found 25 EERW trials published between 1995 and June 2014, involving 5669 patients in a randomised withdrawal phase comparing drug with placebo; 13 (median, 107 patients) had a randomised withdrawal phase of 6 weeks or less, and 12 (median, 334) lasted 12 to 26 weeks. Risks of bias included short duration, inadequate outcome definition, incomplete outcome data reporting, small size, and inadequate dose tapering on randomisation to placebo. Active treatment was usually better than placebo (22/25 trials). This review reduces the uncertainty around the value of EERW trials in pain. If properly designed, conducted, and reported, they are feasible and useful for making decisions about pain therapies. Shorter, small studies can be explanatory; longer, larger studies can inform practice. Current evidence is inadequate for valid comparisons in outcome between EERW and classical trials, although no gross differences were found. This systematic review provides a framework for assessing potential biases and the value of the EERW trials, and for the design of future studies by making recommendations for the conduct and reporting of EERW trials.

The topical 5% lidocaine medicated plaster in localized neuropathic pain: a reappraisal of the clinical evidence

Topical 5% lidocaine medicated plasters represent a well-established first-line option for the treatment of peripheral localized neuropathic pain (LNP). This review provides an updated overview of the clinical evidence (randomized, controlled, and open-label clinical studies, real-life daily clinical practice, and case series). The 5% lidocaine medicated plaster effectively provides pain relief in postherpetic neuralgia, and data from a large open-label controlled study indicate that the 5% lidocaine medicated plaster is as effective as systemic pregabalin in postherpetic neuralgia and painful diabetic polyneuropathy but with an improved tolerability profile. Additionally, improved analgesia and fewer side effects were experienced by patients treated synchronously with the 5% lidocaine medicated plaster, further demonstrating the value of multimodal analgesia in LNP. The 5% lidocaine medicated plaster provides continued benefit after long-term (≤7 years) use and is also effective in various other LNP conditions. Minor application-site reactions are the most common adverse events associated with the 5% lidocaine medicated plaster; there is minimal risk of systemic adverse events and drug–drug interactions. Although further well-controlled studies are warranted, the 5% lidocaine medicated plaster is efficacious and safe in LNP and may have particular clinical benefit in elderly and/or medically compromised patients because of the low incidence of adverse events.

Methods for identification and confirmation of targeted subgroups in clinical trials: A systematic review

Important objectives in the development of stratified medicines include the identification and confirmation of subgroups of patients with a beneficial treatment effect and a positive benefit-risk balance. We report the results of a literature review on methodological approaches to the design and analysis of clinical trials investigating a potential heterogeneity of treatment effects across subgroups. The identified approaches are classified based on certain characteristics of the proposed trial designs and analysis methods. We distinguish between exploratory and confirmatory subgroup analysis, frequentist, Bayesian and decision-theoretic approaches and, last, fixed-sample, group-sequential, and adaptive designs and illustrate the available trial designs and analysis strategies with published case studies.

An in silico approach helped to identify the best experimental design, population, and outcome for future randomized clinical trials

OBJECTIVES

The main objective of our work was to compare different randomized clinical trial (RCT) experimental designs in terms of power, accuracy of the estimation of treatment effect, and number of patients receiving active treatment using in silico simulations.

STUDY DESIGN AND SETTING

A virtual population of patients was simulated and randomized in potential clinical trials. Treatment effect was modeled using a dose-effect relation for quantitative or qualitative outcomes. Different experimental designs were considered, and performances between designs were compared. One thousand clinical trials were simulated for each design based on an example of modeled disease.

RESULTS

According to simulation results, the number of patients needed to reach 80% power was 50 for crossover, 60 for parallel or randomized withdrawal, 65 for drop the loser (DL), and 70 for early escape or play the winner (PW). For a given sample size, each design had its own advantage: low duration (parallel, early escape), high statistical power and precision (crossover), and higher number of patients receiving the active treatment (PW and DL).

CONCLUSION

Our approach can help to identify the best experimental design, population, and outcome for future RCTs. This may be particularly useful for drug development in rare diseases, theragnostic approaches, or personalized medicine.

Criterion Validation Testing of Clinical Metrology Instruments for Measuring Degenerative Joint Disease Associated Mobility Impairment in Cats

Introduction

Degenerative joint disease and associated pain are common in cats, particularly in older cats. There is a need for treatment options, however evaluation of putative therapies is limited by a lack of suitable, validated outcome measures that can be used in the target population of client owned cats. The objectives of this study were to evaluate low-dose daily meloxicam for the treatment of pain associated with degenerative joint disease in cats, and further validate two clinical metrology instruments, the Feline Musculoskeletal Pain Index (FMPI) and the Client Specific Outcome Measures (CSOM).

Methods

Sixty-six client owned cats with degenerative joint disease and owner-reported impairments in mobility were screened and enrolled into a double-masked, placebo-controlled, randomized clinical trial. Following a run-in baseline period, cats were given either placebo or meloxicam for 21 days, then in a masked washout, cats were all given placebo for 21 days. Subsequently, cats were given the opposite treatment, placebo or meloxicam, for 21 days. Cats wore activity monitors throughout the study, owners completed clinical metrology instruments following each period.

Results

Activity counts were increased in cats during treatment with daily meloxicam (p<0.0001) compared to baseline. The FMPI results and activity count data offer concurrent validation for the FMPI, though the relationship between baseline activity counts and FMPI scores at baseline was poor (R²=0.034). The CSOM did not show responsiveness for improvement in this study, and the relationship between baseline activity counts and CSOM scores at baseline was similarly poor (R²=0.042).

Conclusions

Refinements to the FMPI, including abbreviation of the instrument and scoring as percent of possible score are recommended. This study offered further validation of the FMPI as a clinical metrology instrument for use in detecting therapeutic efficacy in cats with degenerative joint disease.

Meta-analyses of pain studies: What we have learned

Meta-analysis is a statistical procedure that integrates the results of at least two independent studies. The biggest threats to meta-analysis are publication bias due to missing studies with negative results and low-quality evidence due to methodological limitations imposed by included studies. Tools to improve the quality of meta-analysis have been developed by the Cochrane Collaboration and by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Meta-analyses of trials have demonstrated that pain responses in patients with chronic pain, following treatment, are not normally distributed but have a bimodal distribution with the majority of patients having either very little or very good pain relief. The benefit can be detected within 2-4 weeks following drug administration. Further, the efficacy of drug and physical treatments is hampered by high placebo response rates, with modest average benefits with active treatments over placebo in both parallel and crossover design trials.

Once daily controlled-release pregabalin in the treatment of patients with fibromyalgia: a phase III, double-blind, randomized withdrawal, placebo-controlled study

OBJECTIVE

Safety and efficacy of a once daily controlled-released (CR) formulation of pregabalin was evaluated in patients with fibromyalgia using a placebo-controlled, randomized withdrawal design.

RESEARCH DESIGN AND METHODS

This multicenter study included 6 week single-blind pregabalin CR treatment followed by 13 week double-blind treatment with placebo or pregabalin CR. The starting dose of 165 mg/day was escalated during the first 3 weeks, up to 495 mg/day based on efficacy and tolerability. Patients with ≥50% reduction in average daily pain score at the end of the single-blind phase were randomized to continue pregabalin CR at the optimized dose (330-495 mg/day) or to placebo. The primary endpoint was time to loss of therapeutic response (LTR), defined as <30% pain reduction relative to single-blind baseline or discontinuation owing to lack of efficacy or adverse event (AE). Secondary endpoints included measures of pain severity, global assessment, functional status, tiredness/fatigue, and sleep.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT01271933.

RESULTS

A total of 441 patients entered the single-blind phase, and 63 were randomized to pregabalin CR and 58 to placebo. The median time to LTR (Kaplan-Meier analysis) was significantly longer in the pregabalin CR group than placebo (58 vs. 22 days, p = 0.02). By trial end, 34/63 (54.0%) pregabalin CR and 41/58 (70.7%) placebo patients experienced LTR. Significantly more patients reported 'benefit from treatment' (Benefit, Satisfaction, and Willingness to Continue Scale) in the pregabalin CR group; no other secondary endpoints were statistically significant. Most AEs were mild to moderate in severity (most frequent: dizziness, somnolence). The percentage of pregabalin CR patients discontinuing because of AEs was 12.2% and 4.8% in the single-blind and double-blind phases, respectively (placebo, 0%).

CONCLUSIONS

Time to LTR was significantly longer with pregabalin CR versus placebo in fibromyalgia patients who initially showed improvement with pregabalin CR, indicating maintenance of response. Pregabalin CR was well tolerated in most patients. Generalizability may be limited by study duration and selective population.

Research designs for proof-of-concept chronic pain clinical trials: IMMPACT recommendations

Proof-of-concept (POC) clinical trials play an important role in developing novel treatments and determining whether existing treatments may be efficacious in broader populations of patients. The goal of most POC trials is to determine whether a treatment is likely to be efficacious for a given indication and thus whether it is worth investing the financial resources and participant exposure necessary for a confirmatory trial of that intervention. A challenge in designing POC trials is obtaining sufficient information to make this important go/no-go decision in a cost-effective manner. An IMMPACT consensus meeting was convened to discuss design considerations for POC trials in analgesia, with a focus on maximizing power with limited resources and participants. We present general design aspects to consider including patient population, active comparators and placebos, study power, pharmacokinetic-pharmacodynamic relationships, and minimization of missing data. Efficiency of single-dose studies for treatments with rapid onset is discussed. The trade-off between parallel-group and crossover designs with respect to overall sample sizes, trial duration, and applicability is summarized. The advantages and disadvantages of more recent trial designs, including N-of-1 designs, enriched designs, adaptive designs, and sequential parallel comparison designs, are summarized, and recommendations for consideration are provided. More attention to identifying efficient yet powerful designs for POC clinical trials of chronic pain treatments may increase the percentage of truly efficacious pain treatments that are advanced to confirmatory trials while decreasing the percentage of ineffective treatments that continue to be evaluated rather than abandoned.

Botulinum toxin type a injections for cervical and shoulder girdle myofascial pain using an enriched protocol design

BACKGROUND

Myofascial pain syndrome is a regional condition of muscle pain and stiffness and is classically characterized by the presence of trigger points in affected musculature. Botulinum toxin type A (BoNT-A) has been shown to have antinociceptive properties and elicit sustained muscle relaxation, thereby possibly affording even greater relief than traditional strategies. Our goal was to determine whether direct injection of BoNT-A into painful muscle groups is effective for cervical and shoulder girdle myofascial pain.

METHODS

An enriched protocol design was used, wherein 114 patients with cervical and shoulder girdle myofascial pain underwent injection of BoNT-A to determine their response to the drug. Fifty-four responders were then enrolled in a 12-week, randomized, double-blind, placebo-controlled trial. Pain scales and quality of life measures were assessed at baseline and at routine follow-up visits until completion of the study after 26 weeks.

RESULTS

Injection of BoNT-A into painful muscle groups improved average visual numerical pain scores in subjects who received a second dose of BoNT-A compared to placebo (P = 0.019 [0.26, 2.78]). Subjects who received a second dose of BoNT-A had a reduced number of headaches per week (P = 0.04 [0.07, 4.55]). Brief Pain Inventory interference scores for general activity and sleep were improved (P = 0.046 [0.038, 3.700] and 0.02 [0.37, 4.33], respectively) in those who received a second dose of BoNT-A.

CONCLUSION

BoNT-A injected directly into painful muscle groups improves average pain scores and certain aspects of quality of life in patients experiencing severe cervical and shoulder girdle myofascial pain.

Gabapentin for chronic neuropathic pain and fibromyalgia in adults

BACKGROUND

This review is an update of a review published in 2011, itself a major update of previous reviews published in 2005 and 2000, investigating the effects of gabapentin in chronic neuropathic pain (pain due to nerve damage). Antiepileptic drugs are used to manage chronic neuropathic pain and fibromyalgia.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of gabapentin in chronic neuropathic pain and fibromyalgia.

SEARCH METHODS

We identified randomised trials of gabapentin for chronic neuropathic pain or fibromyalgia by searching the databases MEDLINE (1966 to March 2014), EMBASE (1980 to 2014 week 10), and CENTRAL in The Cochrane Library (Issue 3 of 12, 2014). We obtained clinical trial reports and synopses of published and unpublished studies from Internet sources, and searched Clinicaltrials.gov. Searches were run originally in 2011 and the date of the most recent search was 17 March 2014.

SELECTION CRITERIA

Randomised, double-blind studies reporting the analgesic and adverse effects of gabapentin in neuropathic pain or fibromyalgia with assessment of pain intensity, pain relief, or both, using validated scales. Participants were adults.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted efficacy and adverse event data, examined issues of study quality, and assessed risk of bias. 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.For efficacy, we calculated the number needed to treat to benefit (NNT), concentrating on at least 50% pain intensity reduction, and Initiative on Methods, Measurement and Pain Assessment in Clinical Trials (IMMPACT) definitions of at least moderate and substantial benefit. For harm we calculated number needed to treat for harm (NNH) for adverse effects and withdrawal. Meta-analysis was undertaken using a fixed-effect model. We emphasised differences between conditions now defined as neuropathic pain, and other conditions like masticatory pain, complex regional painsyndrome type 1 (CRPS-1), and fibromyalgia.

MAIN RESULTS

Seven new studies with 1919 participants were added. Another report (147 participants) provided results for a study already included, but which previously had no usable data. A further report (170 participants) used an experimental formulation of intrathecal gabapentin. Thirty-seven studies (5633 participants) studied oral gabapentin at daily doses of 1200 mg or more in 12 chronic pain conditions; 84% of participants were in studies of postherpetic neuralgia, painful diabetic neuropathy or mixed neuropathic pain. There was no first tier evidence.Second tier evidence for the outcome of at least 50% pain intensity reduction, considered valuable by patients with chronic pain, showed that gabapentin was significantly better than placebo in postherpetic neuralgia (34% gabapentin versus 21% placebo; NNT 8.0, 95% CI 6.0 to 12) and painful diabetic neuropathy (38% versus 21%, NNT 5.9, 95% CI 4.6 to 8.3). There was insufficient information in other pain conditions to reach any reliable conclusion. There was no obvious difference between standard gabapentin formulations and recently-introduced extended-release or gastro-retentive formulations, or between different doses of gabapentin.Adverse events occurred significantly more often with gabapentin. Persons taking gabapentin could expect to have at least one adverse event (62%), withdraw because of an adverse event (11%), suffer dizziness (19%), somnolence (14%), peripheral oedema (7%), and gait disturbance (9%). Serious adverse events (3%) were no more common than with placebo.There were insufficient data for direct comparisons with other active treatments, and only third tier evidence for other painful conditions.

AUTHORS' CONCLUSIONS

There was no top tier evidence that was unequivocally unbiased. Second tier evidence, with potentially important residual biases, showed that gabapentin at doses of 1200 mg or more was effective for some people with some painful neuropathic pain conditions. The outcome of at least 50% pain intensity reduction is regarded as a useful outcome of treatment by patients, and the achievement of this degree of pain relief is associated with important beneficial effects on sleep interference, fatigue, and depression, as well as quality of life, function, and work. About 35% achieved this degree of pain relief with gabapentin, compared with 21% for placebo. Over half of those treated with gabapentin will not have worthwhile pain relief. Results might vary between different neuropathic pain conditions, and the amount of evidence for gabapentin in neuropathic pain conditions except postherpetic neuralgia and painful diabetic neuropathy, and in fibromyalgia, is very limited.The levels of efficacy found for gabapentin are consistent with those found for other drug therapies in postherpetic neuralgia and painful diabetic neuropathy.

Gabapentin for chronic neuropathic pain and fibromyalgia in adults

BACKGROUND

This review is an update of a review published in 2011, itself a major update of previous reviews published in 2005 and 2000, investigating the effects of gabapentin in chronic neuropathic pain (pain due to nerve damage). Antiepileptic drugs are used to manage chronic neuropathic pain and fibromyalgia.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of gabapentin in chronic neuropathic pain and fibromyalgia.

SEARCH METHODS

We identified randomised trials of gabapentin for chronic neuropathic pain or fibromyalgia by searching the databases MEDLINE (1966 to March 2014), EMBASE (1980 to 2014 week 10), and CENTRAL in The Cochrane Library (Issue 3 of 12, 2014). We obtained clinical trial reports and synopses of published and unpublished studies from Internet sources, and searched Clinicaltrials.gov. Searches were run originally in 2011 and the date of the most recent search was 17 March 2014.

SELECTION CRITERIA

Randomised, double-blind studies reporting the analgesic and adverse effects of gabapentin in neuropathic pain or fibromyalgia with assessment of pain intensity, pain relief, or both, using validated scales. Participants were adults.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted efficacy and adverse event data, examined issues of study quality, and assessed risk of bias. 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.For efficacy, we calculated the number needed to treat to benefit (NNT), concentrating on at least 50% pain intensity reduction, and Initiative on Methods, Measurement and Pain Assessment in Clinical Trials (IMMPACT) definitions of at least moderate and substantial benefit. For harm we calculated number needed to treat for harm (NNH) for adverse effects and withdrawal. Meta-analysis was undertaken using a fixed-effect model. We emphasised differences between conditions now defined as neuropathic pain, and other conditions like masticatory pain, complex regional painsyndrome type 1 (CRPS-1), and fibromyalgia.

MAIN RESULTS

Seven new studies with 1919 participants were added. Another report (147 participants) provided results for a study already included, but which previously had no usable data. A further report (170 participants) used an experimental formulation of intrathecal gabapentin. Thirty-seven studies (5633 participants) studied oral gabapentin at daily doses of 1200 mg or more in 12 chronic pain conditions; 84% of participants were in studies of postherpetic neuralgia, painful diabetic neuropathy or mixed neuropathic pain. There was no first tier evidence.Second tier evidence for the outcome of at least 50% pain intensity reduction, considered valuable by patients with chronic pain, showed that gabapentin was significantly better than placebo in postherpetic neuralgia (34% gabapentin versus 21% placebo; NNT 8.0, 95% CI 6.0 to 12) and painful diabetic neuropathy (38% versus 21%, NNT 5.9, 95% CI 4.6 to 8.3). There was insufficient information in other pain conditions to reach any reliable conclusion. There was no obvious difference between standard gabapentin formulations and recently-introduced extended-release or gastro-retentive formulations, or between different doses of gabapentin.Adverse events occurred significantly more often with gabapentin. Persons taking gabapentin could expect to have at least one adverse event (62%), withdraw because of an adverse event (11%), suffer dizziness (19%), somnolence (14%), peripheral oedema (7%), and gait disturbance (9%). Serious adverse events (3%) were no more common than with placebo.There were insufficient data for direct comparisons with other active treatments, and only third tier evidence for other painful conditions.

AUTHORS' CONCLUSIONS

There was no top tier evidence that was unequivocally unbiased. Second tier evidence, with potentially important residual biases, showed that gabapentin at doses of 1200 mg or more was effective for some people with some painful neuropathic pain conditions. The outcome of at least 50% pain intensity reduction is regarded as a useful outcome of treatment by patients, and the achievement of this degree of pain relief is associated with important beneficial effects on sleep interference, fatigue, and depression, as well as quality of life, function, and work. About 35% achieved this degree of pain relief with gabapentin, compared with 21% for placebo. Over half of those treated with gabapentin will not have worthwhile pain relief. Results might vary between different neuropathic pain conditions, and the amount of evidence for gabapentin in neuropathic pain conditions except postherpetic neuralgia and painful diabetic neuropathy, and in fibromyalgia, is very limited.The levels of efficacy found for gabapentin are consistent with those found for other drug therapies in postherpetic neuralgia and painful diabetic neuropathy.

Carbamazepine for chronic neuropathic pain and fibromyalgia in adults

BACKGROUND

This is an update of a Cochrane review entitled 'Carbamazepine for acute and chronic pain in adults' published in Issue 1, 2011. Some antiepileptic medicines have a place in the treatment of neuropathic pain (pain due to nerve damage). This updated review considers the treatment of chronic neuropathic pain and fibromyalgia only, and adds no new studies. The update uses higher standards of evidence than the earlier review, which results in the exclusion of five studies that were previously included.

OBJECTIVES

To assess the analgesic efficacy of carbamazepine in the treatment of chronic neuropathic pain and fibromyalgia, and to evaluate adverse events reported in the studies.

SEARCH METHODS

We searched for relevant studies in MEDLINE, EMBASE and CENTRAL up to February 2014. Additional studies were sought from clinical trials databases, and the reference list of retrieved articles and reviews.

SELECTION CRITERIA

Randomised, double blind, active or placebo controlled trials (RCTs) investigating the use of carbamazepine (any dose, by any route, and for at least two weeks' duration) for the treatment of chronic neuropathic pain or fibromyalgia, with at least 10 participants per treatment group. Participants were adults aged 18 and over.

DATA COLLECTION AND ANALYSIS

Two study authors independently extracted data on efficacy, adverse events, and withdrawals, and examined issues of study quality. Numbers needed to treat for an additional beneficial effect (NNT) or harmful effect (NNH) with 95% confidence intervals (CIs) were calculated from dichotomous data.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, at least 8 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 was considered very likely to be biased or used outcomes of limited clinical utility, or both.

MAIN RESULTS

Ten included studies (11 publications) enrolled 480 participants with trigeminal neuralgia, diabetic neuropathy, and post stroke pain. Nine studies used a cross-over design, and one a parallel group design. Most of the studies were of short duration, lasting four weeks or less.No study provided first or second tier evidence for an efficacy outcome. Using third tier evidence, carbamazepine generally provided better pain relief than placebo in the three conditions studied, with some indication of pain improvement over mainly the short term, but with poorly defined outcomes, incomplete reporting, and in small numbers of participants. There were too few data in studies comparing carbamazepine with active comparators to draw any conclusions.In four studies 65% (113/173) of participants experienced at least one adverse event with carbamazepine, and 27% (47/173) with placebo; for every five participants treated, two experienced an adverse event who would not have done so with placebo. In eight studies 3% (8/268) of participants withdrew due to adverse events with carbamazepine, and none (0/255) with placebo. Serious adverse events were not reported consistently; rashes were associated with carbamazepine. Four deaths occurred in patients on carbamazepine, with no obvious drug association.

AUTHORS' CONCLUSIONS

Carbamazepine is probably effective in some people with chronic neuropathic pain, but with caveats. No trial was longer than four weeks, had good reporting quality, nor used outcomes equivalent to substantial clinical benefit. In these circumstances, caution is needed in interpretation, and meaningful comparison with other interventions is not possible.

Novel design for a phase IIa placebo-controlled, double-blind randomized withdrawal study to evaluate the safety and efficacy of CNV1014802 in patients with trigeminal neuralgia

Background

Trigeminal neuralgia (TN) is a rare severe unilateral facial pain condition. Current guidelines in trigeminal neuralgia management recommend sodium channel blockers – carbamazepine or oxcarbazepine – as the first-line treatment. However, the currently available drugs are often associated with poor tolerability resulting in sub-optimal pain control. CNV1014802 is a novel sodium channel blocker that is being assessed in the treatment of trigeminal neuralgia. Due to the severity of the condition, it is not ethical to conduct a traditional placebo-controlled randomized controlled trial. It is also difficult to use an active control such as carbamazepine, the current gold standard, because of its complex pharmacology and potential for drug interactions.

Methods/Design

The trial uses a randomized withdrawal design to assess efficacy in this rare condition. There is a 21-day open-label phase followed by a randomized 28-day placebo-controlled phase for responders. Thirty patients will be randomized. The primary outcome measure will be pain relief, but secondary measures of quality of life will be of significant importance given the effect of this condition on activities of daily living. Safety and adverse event endpoints are described.

Discussion

There have been very few well-controlled, randomized, placebo-controlled studies in trigeminal neuralgia, and the majority of drugs have had other primary uses. Due to the severity of the pain, minimizing the time a patient is administered placebo was a key factor in designing this study. This study will not only provide data on the efficacy of CNV1014802 in trigeminal neuralgia, but will also provide information on the effectiveness and acceptability of a novel trial design in trigeminal neuralgia.

Trial registration

Trial number NCT01540630

Antiepileptic drugs for neuropathic pain and fibromyalgia - an overview of Cochrane reviews

BACKGROUND

Antiepileptic drugs have been used for treating different types of neuropathic pain, and sometimes fibromyalgia. Our understanding of quality standards in chronic pain trials has improved to include new sources of potential bias. Individual Cochrane reviews using these new standards have assessed individual antiepileptic drugs. An early review from this group, originally published in 1998, was titled 'Anticonvulsants for acute and chronic pain'. This overview now covers the neuropathic pain aspect of that original review, which was withdrawn in 2009.

OBJECTIVES

To provide an overview of the relative analgesic efficacy of antiepileptic drugs that have been compared with placebo in neuropathic pain and fibromyalgia, and to report on adverse events associated with their use.

METHODS

We included reviews published in theCochrane Database of Systematic Reviews up to August 2013 (Issue 7). We extracted information from each review on measures of efficacy and harm, and methodological details concerning the number of participants, the duration of studies, and the imputation methods used, in order to judge potential biases in available data.We analysed efficacy data for each painful condition in three tiers, according to outcome and freedom from known sources of bias. The first tier met current best standards - at least 50% pain intensity reduction over baseline (or its equivalent), without the use of last observation carried forward (LOCF) for dropouts, an intention-to-treat (ITT) analysis, in parallel group studies with at least 200 participants lasting eight weeks or more. The second tier used data from at least 200 participants where one or more of the above conditions were not met. The third tier of evidence related to data from fewer than 200 participants, or with several important methodological problems that limited interpretation.

MAIN RESULTS

No studies reported top tier results.For gabapentin and pregabalin only we found reasonably good second tier evidence for efficacy in painful diabetic neuropathy and postherpetic neuralgia. In addition, for pregabalin, we found evidence of efficacy in central neuropathic pain and fibromyalgia. Point estimates of numbers needed to treat for an additional beneficial effect (NNTs) were in the range of 4 to 10 for the important outcome of pain intensity reduction over baseline of 50% or more.For other antiepileptic drugs there was no evidence (clonazepam, phenytoin), so little evidence that no sensible judgement could be made about efficacy (valproic acid), low quality evidence likely to be subject to a number of biases overestimating efficacy (carbamazepine), or reasonable quality evidence indicating little or no effect (lamotrigine, oxcarbazepine, topiramate). Lacosamide recorded such a trivial statistical superiority over placebo that it was unreliable to conclude that it had any efficacy where there was possible substantial bias.Any benefits of treatment came with a high risk of adverse events and withdrawal because of adverse events, but serious adverse events were not significantly raised, except with oxcarbazepine.

AUTHORS' CONCLUSIONS

Clinical trial evidence supported the use of only gabapentin and pregabalin in some neuropathic pain conditions (painful diabetic neuropathy, postherpetic neuralgia, and central neuropathic pain) and fibromyalgia. Only a minority of people achieved acceptably good pain relief with either drug, but it is known that quality of life and function improved markedly with the outcome of at least 50% pain intensity reduction. For other antiepileptic drugs there was no evidence, insufficient evidence, or evidence of a lack of effect; this included carbamazepine. Evidence from clinical practice and experience is that some patients can achieve good results with antiepileptics other than gabapentin or pregabalin.There is no firm evidence to answer the important pragmatic questions about which patients should have which drug, and in which order the drugs should be used. There is a clinical effectiveness research agenda to provide evidence about strategies rather than interventions, to produce the overall best results in a population, in the shortest time, and at the lowest cost to healthcare providers.

Challenges in design and interpretation of chronic pain trials

The process of systematic review has shone a light on the methodology of randomized controlled trials. Notably, a range of potential biases hinders the interpretation of chronic pain trials. These include a consistent bias favouring active over placebo in trials that are small and of short duration. The use of the 'last observation carried forward' imputation method is known to inflate results, often generating statistically significance when adverse event withdrawals are high; in clinical practice terms, this is the wrong answer. Patients want outcomes of low pain scores, large reductions in pain and relief from associated symptoms, with improvements in ability to function and in quality of life. Some patients achieve this, but many do not. The distribution of benefit is skewed and the use of average pain scores, or change in pain, can be misleading compared with responder analysis in which withdrawal is regarded as non-response. Historically, chronic pain trials have had a simple classic or a crossover design. They have been small and short, and used inappropriate imputation and outcomes unconnected to the experiences of most patients. While these designs are useful for answering some questions, they may be insensitive for many interventions. Newer designs, like enriched enrolment randomized withdrawal (EERW) trials or clinical effectiveness trials, are potentially more interesting and informative.

What works for whom? Determining the efficacy and harm of treatments for pain

There has been a tension between the needs of regulators and industry to demonstrate that interventions are effective and safe, and the needs of professionals to understand how well interventions will work for their patients, and patients to understand what might work for them as individuals. The custom has been to focus on statistical outcomes based on average results, but in-depth analysis based on outcomes obtained by individual patients demonstrates that few are average. Rather, a minority of patients achieve very large reductions in pain (responders), while the majority achieve little (nonresponders). Those who benefit in terms of pain also benefit in other areas, with improved sleep, fatigue, mood, function, quality of life, and ability to work. This changes how benefit and risk are seen; nonresponders should stop treatments that don't work and not, therefore, be exposed to risks, while responders have very large benefits to offset against rare but potentially serious harm. This alternative view, patient-centred and practice-orientated, has major implications for clinical practice, how and why we do clinical trials and how they are designed, how health economic evaluations are done, for decisions made by regulatory and other bodies, and for the theory and practice of evidence-based medicine.

A randomized, placebo-controlled study of the impact of the 7-day buprenorphine transdermal system on health-related quality of life in opioid-naïve patients with moderate-to-severe chronic low back pain

This study evaluated the impact of treatment with Buprenorphine Transdermal System (BTDS) on the health-related quality of life for patients with moderate-to-severe chronic low back pain (CLBP), and the correspondence between quality of life and pain. A multicenter, enriched, double-blind (DB), placebo-controlled, randomized trial evaluated BTDS 10 and 20 μg/hour for treatment of opioid-naïve patients with moderate-to-severe CLBP. The SF-36v2 survey, which measures 8 domains of quality of life, was administered at screening and following an open-label run-in period with BTDS and at weeks 4, 8, and 12 of the DB phase. Post hoc analyses compared SF-36v2 scores between BTDS and placebo groups during the DB phase. Condition burden was examined through comparisons with a U.S. general population sample. Correlations examined the correspondence between quality of life and pain measures. BTDS produced larger improvements than placebo at 12 weeks in all quality-of-life domains (Ps < .05). Treatment group differences in both physical and mental quality of life emerged by 4 weeks. Patients' pretreatment quality of life was worse than that in the general population (Ps < .05); only BTDS treatment eliminated deficits in pain, social functioning, and role limitations due to emotional health. Improvements in quality of life were moderately associated with pain reduction. These data suggest that moderate-to-severe CLBP patients receiving BTDS exhibited better quality of life than patients receiving placebo.

PERSPECTIVE

This post hoc analysis suggests that patients with moderate-to-severe CLBP treated with BTDS exhibit better health-related quality of life than those using placebo within 4 weeks of treatment, and were more likely to exhibit clinically meaningful improvements in quality of life following 12 weeks of treatment.