N-of-1 randomized trials to assess the efficacy of gabapentin for chronic neuropathic pain

Toward responsible clinical n-of-1 strategies for rare diseases

N-of-1 strategies can provide high-quality evidence of treatment efficacy at the individual level and optimize evidence-based selection of off-label treatments for patients with rare diseases. Given their design characteristics, n-of-1 strategies are considered to lay at the intersection between medical research and clinical care. Therefore, whether n-of-1 strategies should be governed by research or care regulations remains a debated issue. Here, we delineate differences between medical research and optimized clinical care, and distinguish the regulations which apply to either. We also set standards for responsible optimized clinical n-of-1 strategies with (off-label) treatments for rare diseases. Implementing clinical n-of-1 strategies as defined here could aid in optimized treatment selection for such diseases.

Individual Treatment Trials—Do Experts Know and Use This Option to Improve the Treatability of Mucopolysaccharidosis?

Mucopolysaccharidoses (MPS) are a group of rare, heterogeneous, lysosomal storage disorders. Patients show a broad spectrum of clinical features with a substantial unmet medical need. Individual treatment trials (ITTs) might be a valid, time- and cost-efficient way to facilitate personalized medicine in the sense of drug repurposing in MPS. However, this treatment option has so far hardly been used—at least hardly been reported or published. Therefore, we aimed to investigate the awareness and utilization of ITTs among MPS clinicians, as well as the potential challenges and innovative approaches to overcome key hurdles, by using an international expert survey on ITTs, namely, ESITT. Although 74% (20/27) were familiar with the concept of ITTs, only 37% (10/27) ever used it, and subsequently only 15% (2/16) published their results. The indicated hurdles of ITTs in MPS were mainly the lack of time and know-how. An evidence-based tool, which provides resources and expertise needed for high-quality ITTs, was highly appreciated by the vast majority (89%; 23/26). The ESITT highlights a serious deficiency of ITT implementation in MPS—a promising option to improve its treatability. Furthermore, we discuss the challenges and innovative approaches to overcome key barriers to ITTs in MPS.

Optimizing and Accelerating the Development of Precision Pain Treatments for Chronic Pain: IMMPACT Review and Recommendations

Large variability in the individual response to even the most-efficacious pain treatments is observed clinically, which has led to calls for a more personalized, tailored approach to treating patients with pain (ie, "precision pain medicine"). Precision pain medicine, currently an aspirational goal, would consist of empirically based algorithms that determine the optimal treatments, or treatment combinations, for specific patients (ie, targeting the right treatment, in the right dose, to the right patient, at the right time). Answering this question of "what works for whom" will certainly improve the clinical care of patients with pain. It may also support the success of novel drug development in pain, making it easier to identify novel treatments that work for certain patients and more accurately identify the magnitude of the treatment effect for those subgroups. Significant preliminary work has been done in this area, and analgesic trials are beginning to utilize precision pain medicine approaches such as stratified allocation on the basis of prespecified patient phenotypes using assessment methodologies such as quantitative sensory testing. Current major challenges within the field include: 1) identifying optimal measurement approaches to assessing patient characteristics that are most robustly and consistently predictive of inter-patient variation in specific analgesic treatment outcomes, 2) designing clinical trials that can identify treatment-by-phenotype interactions, and 3) selecting the most promising therapeutics to be tested in this way. This review surveys the current state of precision pain medicine, with a focus on drug treatments (which have been most-studied in a precision pain medicine context). It further presents a set of evidence-based recommendations for accelerating the application of precision pain methods in chronic pain research. PERSPECTIVE: Given the considerable variability in treatment outcomes for chronic pain, progress in precision pain treatment is critical for the field. An array of phenotypes and mechanisms contribute to chronic pain; this review summarizes current knowledge regarding which treatments are most effective for patients with specific biopsychosocial characteristics.

Assessment of a Mobile Health iPhone App for Semiautomated Self-management of Chronic Recurrent Medical Conditions Using an N-of-1 Trial Framework: Feasibility Pilot Study

BACKGROUND

Management of chronic recurrent medical conditions (CRMCs), such as migraine headaches, chronic pain, and anxiety/depression, remains a major challenge for modern providers. Our team has developed an edge-based, semiautomated mobile health (mHealth) technology called iMTracker that employs the N-of-1 trial approach to allow self-management of CRMCs.

OBJECTIVE

This study examines the patterns of adoption, identifies CRMCs that users selected for self-application, and explores barriers to use of the iMTracker app.

METHODS

This is a feasibility pilot study with internet-based recruitment that ran from May 15, 2019, to December 23, 2020. We recruited 180 patients to pilot test the iMTracker app for user-selected CRMCs for a 3-month period. Patients were administered surveys before and after the study.

RESULTS

We found reasonable usage rates: a total of 73/103 (70.9%) patients who were not lost to follow-up reported the full 3-month use of the app. Most users chose to use the iMTracker app to self-manage chronic pain (other than headaches; 80/212, 37.7%), followed by headaches in 36/212 (17.0%) and mental health (anxiety and depression) in 27/212 (12.8%). The recurrence rate of CRMCs was at least weekly in over 93% (169/180) of patients, with 36.1% (65/180) of CRMCs recurring multiple times in a day, 41.7% (75/180) daily, and 16.1% (29/180) weekly. We found that the main barriers to use were the design and technical function of the app, but that use of the app resulted in an improvement in confidence in the efficiency and safety/privacy of this approach.

CONCLUSIONS

The iMTracker app provides a feasible platform for the N-of-1 trial approach to self-management of CRMCs, although internet-based recruitment provided limited follow-up, suggesting that in-person evaluation may be needed. The rate of CRMC recurrence was high enough to allow the N-of-1 trial assessment for most traits.

Status of N-of-1 Trials in Chronic Pain Management: A Narrative Review

N-of-1 trials are randomized controlled clinical trials conducted exclusively on a single patient. The ultimate aim of N-of-1 trials is to optimize a strategy in a particular individual. Chronic pain is a common but refractory clinical problem. Its diverse etiologies and broad variations among patients often lead to the requirement of individualizing medicine. Thus, chronic pain represents a classical condition for N-of-1 clinical trials. Studies have indicated that N-of-1 benefits patients with chronic pain, multiple comorbidities, and uncertain variations during therapies; however, this approach it is not yet adopted as the first choice in pain clinics. To dissect the current status of N-of-1 in chronic pain management, as well as the limitations for its implementation, we herein studied all N-of-1 studies related to chronic pain by searching three major databases (PubMed, ClinicalTrial.gov, Cochrane Library) for publications between 1985 and 2020. Of 35 eligibility papers, 19 were selected for analysis. Results confirmed that N-of-1 trials have solved the refractory cases including osteoarthritis, chronic musculoskeletal pain, and neuropathic pain; however, none of the trials dealt with cancer pain. Longer time and more efforts are needed from investigators when carrying out N-of-1 trials, which inevitably result in implementation difficulties. Of note, all recruited trials were conducted in developed countries. As mobile devices have been introduced and protocols improve, renewed interest in the implementation of N-of-1 trials will occur. Collectively, a previously underestimated conflict between "precision medicine" and "poor implementation" has put N-of-1 in a challenging position for chronic pain management.

Comparing pregabalin and gabapentin for persistent neuropathic pain: A protocol for a pilot N-of-1 trial series

Background

Evidence-based management of neuropathic pain is commonly ineffective due to the large variability in response between cases. Patients often have to trial several drugs before finding one that provides adequate relief, leading to increased costs and worsened outcomes. There is thus a need for tools to guide and streamline prescribing decisions in neuropathic pain. N-of-1 trials provide a potentially precise and economical method of selecting between multiple interventions in an individual patient, and merit a feasibility assessment for use in clinical pain practice.

Aims

We aim to evaluate the feasibility of N-of-1 trials to compare pregabalin and gabapentin for individual presentations of neuropathic pain.

Methods

This is a double-blinded multiple crossover study, with recruitment from existing patients at an outpatient pain clinic in New South Wales, Australia. Participants will undergo three 4-week treatment pairs, comprising 2 weeks of pregabalin (150–600 mg/day) and 2 weeks of gabapentin (900–3600 mg/day), in an individually randomised order. Intervention doses will be derived from participants’ existing treatment dose. Medications will be taken orally three times daily. The primary outcome will be pain intensity; measures will be self-reported daily in patient diaries. After completing all three cycles, participants and their physicians will be presented with the results of the trial to form an informed decision about their treatment.

Discussion

As a stable yet debilitating condition, neuropathic pain is especially amenable to an N-of-1 study design. A successful trial would represent a significant quality of life improvement for the patient, possibly extending over the course of their lifetime.

N-of-1 Trials in Neurology: A Systematic Review

ObjectiveTo perform a systematic review of published N-of-1 trials (e.g. single patient cross-over trials) in neurological disorders, including an assessment of methodological quality and reporting.MethodsWe searched PubMed, MEDLINE and Embase, from inception date - the first of December 2019, for reports on N-of-1 trials in neurological disorders. Basic trial information on design, disease, intervention, analysis and treatment success was extracted. Strengths and weaknesses of the N-of-1 trials were assessed using the CONSORT extension for N-of-1 trials (CENT) 2015 criteria checklist and the Jadad score as measures of quality and reporting.ResultsWe retrieved 40 reports of N-of-1 trials in neurological disorders (19 individual N-of-1 trials, 21 series of N-of-1 trials). Most N-of-1 trials were performed in neuromuscular and neurodegenerative / movement disorders. Unlike the majority of trials that studied the main symptom(s) of a chronic stable condition, nine N-of-1 trials studied a stable chronic symptom of a progressive or acute neurological disorder. Besides pharmacological interventions, electrical stimulation protocols and nutritional products were studied. A mean total CENT score of 20.88 (SD, 9.10; range 0-43) and mean total Jadad score of 2.90 (SD, 2.15; range 0-5) were found as methodological measures of quality and reporting across all N-of-1 trialsConclusionsN-of-1 trials have been reported in numerous neurological disorders, not only in chronic stable disorders, but also in progressive or acute disorders with a stable symptom. This indicates the emerging therapeutic area of N-of-1 trials in Neurology.Methodological quality and reporting of N-of-1 trials were found suboptimal and can easily be improved in future trials by appropriately describing the methods of blinding and randomization and follow CENT guidelines. As most N-of-1 trials remain unreported in medical literature, this systematic review probably only represent the tip of the iceberg of conducted N-of-1 trials in neurological disorders. In addition to conventional trial designs, N-of-1 trials can help to bridge the gap between research and clinical care by providing an alternative, personalized level 1 evidence-base for suitable treatments.

Establishment of an International Collaborative Network for N-of-1 Trials and Single-Case Designs

In this article we briefly examine the unique features of Single-Case Designs (SCDs) (studies in a single participant), their history and current trends, and real-world clinical applications. The International Collaborative Network for N-of-1 Trials and Single-Case Designs (ICN) is a formal collaborative network for individuals with an interest in SCDs. The ICN was established in 2017 to support the SCD scientific community and provide opportunities for collaboration, a global communication channel, resource sharing and knowledge exchange. In May 2021, there were more than 420 members in 31 countries. A member survey was undertaken in 2019 to identify priorities for the ICN for the following few years. This article outlines the key priorities identified and the ICN's progress to date in these key areas including network activities (developing a communications strategy to increase awareness, collecting/sharing a comprehensive set of resources, guidelines and tips, and incorporating the consumer perspective) and scientific activities (writing position papers and guest editing special journal issues, exploring key stakeholder perspectives about SCDs, and working to streamline ethical approval processes for SCDs). The ICN provides a practical means to engage with this methodology through membership. We encourage clinicians, researchers, industry, and healthcare consumers to learn more about and conduct SCDs, and to join us in our mission of using SCDs to improve health outcomes for individuals and populations.

Racial and ethnic minority patient participation in N-of-1 trials: perspectives of healthcare providers and patients

Aim: Patients from racial and ethnic minority backgrounds in the USA have historically been under-represented in research trials. Understanding their viewpoints regarding participation in N-of-1 trials is imperative as we design and implement these studies. Materials & methods: We conducted six focus groups of racial and ethnic minority patients (n = 25) and providers (n = 9). We used content analysis to identify themes. Results: Our results noted the importance of considering family members in N-of-1 trial recruitment and participation, patients' desire for education as a design feature, for 'lifestyle' changes as a treatment option and for use of nonevidence-based treatments in the design of future N-of-1 trials. Conclusion: Personalized trials have the potential to change the way we deliver primary care and improve disparities for minorities.

Innovation in Regulatory Science Is Meeting Evolution of Clinical Evidence Generation

At the turn of the century, the pharmaceutical industry began a transition toward a focus on oncology, rare diseases, and other areas of high unmet need that required a new, more complex approach to drug development. For many of these disease states and novel approaches to therapy, traditional approaches to clinical trial design fall short, and a number of innovative trial designs have emerged. In light of these changes, regulators across the globe are implementing new programs to provide regular development program support, facilitate accelerated access, use real-world data, and use digital tools to improve patients' lives. Emerging market regulators are also focusing on simplifying their regulatory pathways via regional harmonization schemes with varying levels of ambition. These changes in the external environment imply that biopharma regulatory teams need to adapt and evolve, leveraging digital tools, data, and analytics, and positioning themselves as strategic advisors during development.

Personalised Medicine Using N-of-1 Trials: Overcoming Barriers to Delivery

In this paper we discuss the value of N-of-1 trials in personalising health care. We describe the challenges faced in implementing N-of-1 trials in the United Kingdom’s National Health Service and suggest how making greater use of these personalised trials might be facilitated.

Protocol: Using N-of-1 tests to identify responders to melatonin for sleep disturbance in Parkinson's disease

BACKGROUND

40% of Parkinson's Disease (PD) sufferers experience insomnia, impacting health and quality of life for patients and family members, especially carers. There is little evidence that current treatments are effective.

OBJECTIVES

To determine the effectiveness of melatonin in reducing insomnia in 44 individuals with PD using N-of-1 trials. To aggregate group data to arrive at population estimates of effectiveness (measured by improvements in PDSS-2) and safety (measured by adverse events) of melatonin in improving insomnia in PD. To assess the feasibility of offering N-of-1 trials for insomnia in PD.

METHODOLOGY

Participants will receive either immediate-release melatonin or placebo in random order in 3 paired two-week treatment periods (12 weeks total). Based on their response in a two-week run-in period on 3 mg daily, they will trial either 3 mg or 6 mg. Patients will keep daily sleep diaries and wear a MotionWatch throughout. After the trial patients will discuss their individual report with their doctor, which provides direct feedback about effectiveness and safety of melatonin for them.

STATISTICAL METHODS

We will analyse N-of-1 tests 1) individually: effects of melatonin on PDSS-2 and safety will be reported; and 2) aggregated across individual N-of-1 studies, combined using a Bayesian multilevel random effects model, which will account for repeated measures on individuals over time, and will return posterior estimates of overall treatment effect, and effect in each individual.

CLINICAL TRIAL REGISTRATION NUMBER

ACTRN12617001103358.

N-of-1 Clinical Trials in Nutritional Interventions Directed at Improving Cognitive Function

Longer life expectancy has led to an increase in the prevalence of age-related cognitive decline and dementia worldwide. Due to the current lack of effective treatment for these conditions, preventive strategies represent a research priority. A large body of evidence suggests that nutrition is involved in the pathogenesis of age-related cognitive decline, but also that it may play a critical role in slowing down its progression. At a population level, healthy dietary patterns interventions, such as the Mediterranean and the MIND diets, have been associated with improved cognitive performance and a decreased risk of neurodegenerative disease development. In the era of evidence-based medicine and patient-centered healthcare, personalized nutritional recommendations would offer a considerable opportunity in preventing cognitive decline progression. N-of-1 clinical trials have emerged as a fundamental design in evidence-based medicine. They consider each individual as the only unit of observation and intervention. The aggregation of series of N-of-1 clinical trials also enables population-level conclusions. This review provides a general view of the current scientific evidence regarding nutrition and cognitive decline, and critically states its limitations when translating results into the clinical practice. Furthermore, we suggest methodological strategies to develop N-of-1 clinical trials focused on nutrition and cognition in an older population. Finally, we evaluate the potential challenges that researchers may face when performing studies in precision nutrition and cognition.

Demonstrating Heterogeneity of Treatment Effects Among Patients: An Overlooked but Important Step Toward Precision Medicine

Although heterogeneity in the observed outcomes in clinical trials is often assumed to reflect a true heterogeneous response, it could actually be due to random variability. This retrospective analysis of four randomized, double-blind, placebo-controlled multiperiod (i.e., episode) crossover trials of fentanyl for breakthrough cancer pain illustrates the use of multiperiod crossover trials to examine heterogeneity of treatment response. A mixed-effects model, including fixed effects for treatment and episode and random effects for patient and treatment-by-patient interaction, was used to assess the heterogeneity in patients' responses to treatment during each episode. A significant treatment-by-patient interaction was found for three of four trials (P < 0.05), suggesting heterogeneity of the effect of fentanyl among different patients in each trial. Similar analyses in other therapeutic areas could identify conditions and therapies that should be investigated further for predictors of treatment response in efforts to maximize the efficiency of developing precision medicine strategies.

N-of-1 trials for assessing the effects of deprescribing medications on short-term clinical outcomes in older adults: a systematic review

OBJECTIVES

The objective of this study was to determine the applicability of utilizing the N-of-1 method for deprescribing trials in older adults.

STUDY DESIGN AND SETTING

Systematic review of any human studies conducted in older adults (≥50 years), deprescribing any long-term treatment over less than a year using the N-of-1 trial method was performed. Two authors independently reviewed all articles for eligibility and extracted data. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Quality assessment of trials was carried out using the Physiotherapy Evidence Database scale.

RESULTS

Six studies were identified and extracted. Trials investigated the efficacy of pharmacological and non-pharmacological therapies for treating diseases. Four trials demonstrated non-significant benefits of treatment, with a significant number of patients discontinuing their medications in two trials where follow-up data was collected (N = 8/18, 9/14 [44.4--64.3%]). In two studies, where treatment was beneficial, all participants were found to be maintaining regimen at follow-up.

CONCLUSION

The N-of-1 trial methodology can be used to generate patient-specific evidence of medication and inform prescribing decisions. Future studies are required to assess the feasibility of using the N-of-1 method to determine the effects of deprescribing medications on short-term outcomes.

Sample size considerations for n-of-1 trials

N-of-1 trials are trials in which patients are treated with two or more treatments on multiple occasions. They can have many different purposes and can be analysed in different frameworks. In this note, five different criteria for planning sample sizes for n-of-1 trials are identified, and formulae and advice to address the associated tasks are provided. The basic design addressed is that of randomisation to treatment and control within cycles of pairs of episodes and the model assumed is that of a Normal-Normal mixture with variance components corresponding to within-cycle within-patient variation and treatment-by-patient interaction. The code to accomplish the tasks has been written in GenStat®, SAS® and R® and the application of the approaches is illustrated.

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.

Comparative effectiveness of antihypertensive treatment for older children with primary hypertension: study protocol for a series of n-of-1 randomized trials

BACKGROUND

Children are increasingly being diagnosed with primary hypertension. The absence of comparative effectiveness research of antihypertensive medications in children has contributed to considerable differences in prescribing practices among physicians treating children with primary hypertension. Even if parallel-group trials had established a best overall choice for most of these children, the best medication for an individual may differ from the best overall medication.

METHODS/DESIGN

This project consists of a series of systematically administered n-of-1 trials among older children to verify the need for ongoing antihypertensive treatment and, if so, to identify the preferred single drug therapy from among the three major classes of drugs commonly used for primary hypertension (angiotensin-converting enzyme inhibitors, calcium channel blockers, and diuretics). We will determine whether one of these is the preferred therapy for the great majority of patients. The "preferred" therapy is the drug which produces normal ambulatory blood pressure, with the greatest reduction in blood pressure without unacceptable side effects. We will recruit 50 patients from the Houston Pediatric and Adolescent Hypertension Program clinic. For each patient, the three drugs will be prescribed in random order and each drug will be taken for 2 weeks. The effectiveness of each therapy will be measured with 24-h ambulatory blood pressure monitoring, and tolerability will be assessed using a side effect questionnaire. Participants will rotate through treatment periods, repeating drugs and adjusting doses until the preferred therapy is identified. In assessing whether one of the medications is most effective for the majority of subjects, the primary outcome will be the percentage of participants for whom each drug is selected as the preferred therapy. We hypothesize that no drug will be selected for the great majority of the subjects, a finding that would support consideration of clinical use of n-of-1 trials. Secondary analyses will explore whether patient characteristics predict which medication will be selected as a preferred drug.

DISCUSSION

This study will help optimize care of participating patients and provide evidence regarding the usefulness of n-of-1 trials in identifying appropriate treatment for children with hypertension and potentially other disorders.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02412761 (registered 4/8/2015).

Use of non-opioid analgesics as adjuvants to opioid analgesia for cancer pain management in an inpatient palliative unit: does this improve pain control and reduce opioid requirements?

BACKGROUND

Cancer pain is complex, and despite the introduction of the WHO cancer pain ladder, few studies have looked at the prevalence of adjuvant medication use in an inpatient palliative medicine unit. In this study, we evaluate the use of adjuvant pain medications in patients admitted to an inpatient palliative care unit and whether their use affects pain scores or opiate dosing.

METHODS

In this retrospective observational study, patients admitted to the inpatient palliative care unit over a 3-month period with a diagnosis of cancer on opioid therapy were selected. Data pertaining to demographics, diagnosis, oral morphine dose equivalent of the opioid at the time of discharge, adjuvant analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and pain scores as reported by nurses and physicians were collected.

RESULTS

Seventy-seven patients were eligible over a 3-month period, out of which 65 (84 %) were taking an adjuvant medication. The most commonly prescribed adjuvant was gabapentin (70 %). Fifty-seven percent were taking more than one adjuvant. There were more women in the group receiving adjuvants (57 vs. 17%, p = 0.010). Those without adjuvants compared with those on adjuvants did not have worse pain scores on discharge as reported by physicians (0.8 ± 0.8 vs. 1.0 ± 0.7, p = 0.58) or nurses (2.0 ± 2.7 vs. 2.1 ± 2.6, p = 0.86). There was no difference in morphine equivalent doses of the opioid in both groups (median (min, max); 112 (58, 504) vs. 200 (30, 5,040)) at the time of discharge; 75-80 % of patients had improvement in pain scores as measured by a two-point reduction in numerical rating scale (NRS).

DISCUSSION

This study shows that adjuvant medications are commonly used for treating pain in patients with cancer. More than half of study population were on two adjuvants or an adjuvant plus NSAID along with an opioid. We did not demonstrate any benefit in terms of improved pain scores or opioid doses with adjuvants, but this could reflect confounding variables and physician choice. Larger prospective studies are needed to define the opioid-sparing effects of adjuvants.

CONCLUSION

Adjuvant agents are used in over 80 % of those treated for cancer 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.

Complex regional pain syndrome: From diagnosis to rehabilitation

Complex regional pain syndrome (CRPS) is a debilitating pathology characterised by intense chronic pain associated with vasomotor, sensory and motor dysfunction of the affected limb. Although the pathophysiology of CRPS is not fully understood, it is recognised that inflammatory processes and autonomic dysfunction are involved. These processes are associated with peripheral and central sensitisation as well as changes in brain structure and function, and are reflected in the clinical presentation of CRPS. CRPS management requires an interdisciplinary team and requires the therapeutic approach to be individualised. With regard to pharmacological treatment, bisphosphonates, corticosteroids, ketamine and anticonvulsants have been demonstrated to be effective for CRPS management. Psychotherapy, including cognitive-behavioural therapy, has produced promising results but more studies are needed to confirm its efficacy. Among rehabilitation interventions, there is evidence of the efficacy of physiotherapy and occupational therapy in diminishing CRPS symptoms and achieving a higher level of functioning. In this regard, the rehabilitation modality that seems the most promising according to the actual literature is graded motor imagery, which can help to reverse the maladaptive neuroplasticity occurring in CRPS.

A comparison of four methods for the analysis of N-of-1 trials

OBJECTIVE

To provide a practical guidance for the analysis of N-of-1 trials by comparing four commonly used models.

METHODS

The four models, paired t-test, mixed effects model of difference, mixed effects model and meta-analysis of summary data were compared using a simulation study. The assumed 3-cycles and 4-cycles N-of-1 trials were set with sample sizes of 1, 3, 5, 10, 20 and 30 respectively under normally distributed assumption. The data were generated based on variance-covariance matrix under the assumption of (i) compound symmetry structure or first-order autoregressive structure, and (ii) no carryover effect or 20% carryover effect. Type I error, power, bias (mean error), and mean square error (MSE) of effect differences between two groups were used to evaluate the performance of the four models.

RESULTS

The results from the 3-cycles and 4-cycles N-of-1 trials were comparable with respect to type I error, power, bias and MSE. Paired t-test yielded type I error near to the nominal level, higher power, comparable bias and small MSE, whether there was carryover effect or not. Compared with paired t-test, mixed effects model produced similar size of type I error, smaller bias, but lower power and bigger MSE. Mixed effects model of difference and meta-analysis of summary data yielded type I error far from the nominal level, low power, and large bias and MSE irrespective of the presence or absence of carryover effect.

CONCLUSION

We recommended paired t-test to be used for normally distributed data of N-of-1 trials because of its optimal statistical performance. In the presence of carryover effects, mixed effects model could be used as an alternative.

The patient-specific functional scale: psychometrics, clinimetrics, and application as a clinical outcome measure

STUDY DESIGN

Systematic review of the literature.

OBJECTIVE

To summarize peer-reviewed literature on the reliability, validity, and responsiveness of the Patient-Specific Functional Scale (PSFS), and to identify its use as an outcome measure.

METHODS

Searches were performed of several electronic databases from 1995 to May 2010. Studies included were published articles containing (1) primary research investigating the psychometric and clinimetrics of the PSFS or (2) the implementation of the PSFS as an outcome measure. We assessed the methodological quality of studies included in the first category.

RESULTS

Two hundred forty-two articles published from 1994 to May 2010 were identified. Of these, 66 met the inclusion criteria for this review, with 13 reporting the measurement properties of the PSFS, 55 implementing the PSFS as an outcome measure, and 2 doing both of the above. The PSFS was reported to be valid, reliable, and responsive in populations with knee dysfunction, cervical radiculopathy, acute low back pain, mechanical low back pain, and neck dysfunction. The PSFS was found to be reliable and responsive in populations with chronic low back pain. The PSFS was also reported to be valid, reliable, or responsive in individuals with a limited number of acute, subacute, and chronic conditions. This review found that the PSFS is also being used as an outcome measure in many other conditions, despite a lack of published evidence supporting its validity in these conditions.

CONCLUSION

Although the use of the PSFS as an outcome measure is increasing in physiotherapy practice, there are gaps in the research literature regarding its validity, reliability, and responsiveness in many health conditions.

Gabapentin for chronic neuropathic pain and fibromyalgia in adults

BACKGROUND

This review updates parts of two earlier Cochrane reviews investigating effects of gabapentin in chronic neuropathic pain (pain due to nerve damage). Antiepileptic drugs are used to manage pain, predominantly for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for chronic neuropathic pain management.

SEARCH STRATEGY

We identified randomised trials of gabapentin in acute, chronic or cancer pain from MEDLINE, EMBASE, and CENTRAL. We obtained clinical trial reports and synopses of published and unpublished studies from Internet sources. The date of the most recent search was January 2011.

SELECTION CRITERIA

Randomised, double-blind studies reporting the analgesic and adverse effects of gabapentin in neuropathic pain with assessment of pain intensity and/or pain relief, using validated scales. Participants were adults aged 18 and over.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We calculated numbers needed to treat to benefit (NNTs), concentrating on IMMPACT (Initiative on Methods, Measurement and Pain Assessment in Clinical Trials) definitions of at least moderate and substantial benefit, and to harm (NNH) for adverse effects and withdrawal. Meta-analysis was undertaken using a fixed-effect model.

MAIN RESULTS

Twenty-nine studies (3571 participants), studied gabapentin at daily doses of 1200 mg or more in 12 chronic pain conditions; 78% of participants were in studies of postherpetic neuralgia, painful diabetic neuropathy or mixed neuropathic pain. Using the IMMPACT definition of at least moderate benefit, gabapentin was superior to placebo in 14 studies with 2831 participants, 43% improving with gabapentin and 26% with placebo; the NNT was 5.8 (4.8 to 7.2). Using the IMMPACT definition of substantial benefit, gabapentin was superior to placebo in 13 studies with 2627 participants, 31% improving with gabapentin and 17% with placebo; the NNT was 6.8 (5.6 to 8.7). These estimates of efficacy are more conservative than those reported in a previous review. Data from few studies and participants were available for other painful conditions.Adverse events occurred significantly more often with gabapentin. Persons taking gabapentin can expect to have at least one adverse event (66%), withdraw because of an adverse event (12%), suffer dizziness (21%), somnolence (16%), peripheral oedema (8%), and gait disturbance (9%). Serious adverse events (4%) were no more common than with placebo.There were insufficient data for comparisons with other active treatments.

AUTHORS' CONCLUSIONS

Gabapentin provides pain relief of a high level in about a third of people who take if for painful neuropathic pain. Adverse events are frequent, but mostly tolerable. More conservative estimates of efficacy resulted from using better definitions of efficacy outcome at higher, clinically important, levels, combined with a considerable increase in the numbers of studies and participants available for analysis.

Using N-of-1 trials to improve patient management and save costs

BACKGROUND

N-of-1 trials test treatment effectiveness within an individual patient.

OBJECTIVE

To assess (i) the impact of three different N-of-1 trials on both clinical and economic outcomes over 12 months and (ii) whether the use of N-of-1 trials to target patients' access to high-cost drugs might be cost-effective in Australia.

DESIGN

Descriptive study of management change, persistence, and costs summarizing three N-of-1 trials.

PARTICIPANTS

Volunteer patients with osteoarthritis, chronic neuropathic pain or ADHD whose optimal choice of treatment was uncertain.

INTERVENTIONS

Double-blind cyclical alternative medications for the three conditions.

MEASURES

Detailed resource use, treatment and health outcomes (response) data collected by postal and telephone surveys immediately before and after the trial and at 3, 6 and 12 months. Estimated costs to the Australian healthcare system for the pre-trial vs. 12 months post-trial.

RESULTS

Participants persisting with the joint patient-doctor decision 12 months after trial completion were 32% for osteoarthritis, 45% for chronic neuropathic pain and 70% for the ADHD trials. Cost-offsets were obtained from reduced usage of non-optimal drugs, and reduced medical consultations. Drug costs increased for the chronic neuropathic pain and ADHD trials due to many patients being on either low-cost or no pharmaceuticals before the trial.

CONCLUSIONS

N-of-1 trials are an effective method to identify optimal treatment in patients in whom disease management is uncertain. Using this evidence-based approach, patients and doctors tend to persist with optimal treatment resulting in cost-savings. N-of-1 trials are clinically acceptable and may be an effective way of rationally prescribing some expensive long-term medicines.

Stakeholders' views on the routine use of n-of-1 trials to improve clinical care and to make resource allocation decisions for drug use

N-of-1 trials are empirical formal tests using a within-patient randomised, double-blind, cross-over comparison of drug and placebo (or another drug), which we adapted to study individual patients' responses as a clinical tool to guide clinical management. We administered semi-structured interviews to gauge stakeholder perspectives on the possibility of using routine n-of-1 trials for this purpose. Stakeholders included government and non-government health care sector, and patient, clinician and consumer, organisations. Stakeholders supported more widespread implementation of n-of-1 trials, in a targeted fashion, with some caveats. Barriers to their widespread implementation included constraints on doctors' time, doctors' acceptance, drug company acceptance, patient willingness, and cost. Strategies for overcoming barriers included conditional Pharmaceutical Benefits Scheme listing if cost-effective. There was little consensus on which model of n-of-1 trial implementation would be most effective. We discuss different approaches to addressing the several concerns raised to enable widespread introduction of n-of-1 trials into routine clinical practice as a decision tool.

EFNS guidelines on the pharmacological treatment of neuropathic pain: 2010 revision

BACKGROUND AND OBJECTIVES

This second European Federation of Neurological Societies Task Force aimed at updating the existing evidence about the pharmacological treatment of neuropathic pain since 2005.

METHODS

Studies were identified using the Cochrane Database and Medline. Trials were classified according to the aetiological condition. All class I and II randomized controlled trials (RCTs) were assessed; lower class studies were considered only in conditions that had no top-level studies. Treatments administered using repeated or single administrations were considered, provided they are feasible in an outpatient setting.

RESULTS

Most large RCTs included patients with diabetic polyneuropathies and post-herpetic neuralgia, while an increasing number of smaller studies explored other conditions. Drugs generally have similar efficacy in various conditions, except in trigeminal neuralgia, chronic radiculopathy and HIV neuropathy, with level A evidence in support of tricyclic antidepressants (TCA), pregabalin, gabapentin, tramadol and opioids (in various conditions), duloxetine, venlafaxine, topical lidocaine and capsaicin patches (in restricted conditions). Combination therapy appears useful for TCA-gabapentin and gabapentin-opioids (level A).

CONCLUSIONS

There are still too few large-scale comparative studies. For future trials, we recommend to assess comorbidities, quality of life, symptoms and signs with standardized tools and attempt to better define responder profiles to specific drug treatments.