Factors determining response to antiepileptic drugs in randomized controlled trials. A systematic review and meta-analysis

A narrative review of the placebo effect: historical roots, current applications, and emerging insights

PURPOSE

Placebo is a term to define physiologically inactive compounds used in treatment that causes physical and emotional changes. The placebo effect, driven by expectation and conditioning, plays a significant role in various conditions like pain, depression, and Parkinson's disease, while the nocebo effect can hinder treatment outcomes. Understanding mechanisms such as neuromodulation and genetics has gained importance in modern medicine. This review aims to explore the clinical relevance of placebo responses, particularly in neuropsychiatric disorders, and their potential in personalized medicine. By integrating placebo research into healthcare, it highlights opportunities to enhance treatment efficacy, improve patient well-being, and reduce reliance on pharmacological interventions.

METHODS

A comprehensive literature search was conducted in PubMed, Scopus, and Google Scholar databases. Recent studies were reviewed to evaluate placebo effects, and the variability of the placebo response in neuropsychiatric disorders was summarized.

RESULTS

Placebo effects significantly impact treatment outcomes across various conditions, including Parkinson's disease, depression, pain syndromes, and epilepsy. The mechanisms involve neurobiological and psychological factors, with evidence suggesting that placebo interventions can modulate neurotransmitter activity and improve patient well-being.

CONCLUSION

Integrating placebo research into clinical practice may enhance treatment outcomes, reduce drug dependency, and support personalized medicine by tailoring interventions to individual placebo responsiveness. Understanding placebo and nocebo mechanisms can optimize therapeutic strategies while minimizing unnecessary pharmacological treatments.

The placebo effect in the treatment of children with epilepsy: A systematic review

PURPOSE

To investigate the placebo effect in the treatment of children and adolescents with epilepsy.

METHODS

We conducted a systematic review of studies comparing anti-seizure medication (ASM) to placebo in children and adolescents with epilepsy. Eligible studies were identified through the database PubMed following PRISMA guidelines resulting in the identification of 1173 articles. Screening and inclusion were assessed by two independent reviewers and 17 studies met inclusion criteria.

RESULTS

Seventeen studies involving children and adolescents with epilepsy were included in this review. Compared to levetiracetam (LEV) and perampanel (PER), the placebo did not show a significant reduction in seizures. However, compared to pregabalin (PGB) the placebo was significant in reducing seizures at lower doses. Results for eslicarbazepine (ESL) were contradictory. Placebo-treated patients generally had lower Child Behavior checklist (CBCL) problem scores than those on LEV, which was associated with higher Total Problem Scores and worse Aggressive Behavior scores. Adverse event (AE) rates in the placebo groups varied widely, from 14 % to 91.8 %.

CONCLUSION

This systematic review examined the effect of placebo treatment compared to ASMs in childhood epilepsy across 17 studies. The effectiveness of placebos was not significant compared to LEV and PER. However, there was a significant placebo effect compared to PGB, which was higher compared to low PGB doses than compared to high PGB doses. AE rates varied widely. Assessing long-term cognitive and behavioral outcomes was challenging due to short study durations and potential biases. Future research could play a critical role in preventing AEs in children undergoing ASM treatment by providing a deeper understanding of the placebo effect associated with these medications.

An empirical study on 209 networks of treatments revealed intransitivity to be common and multiple statistical tests suboptimal to assess transitivity

BACKGROUND

Transitivity assumption is the cornerstone of network meta-analysis (NMA). Investigating the plausibility of transitivity can unveil the credibility of NMA results. The commonness of transitivity was examined based on study dissimilarities regarding several study-level aggregate clinical and methodological characteristics reported in the systematic reviews. The present study also demonstrated the disadvantages of using multiple statistical tests to assess transitivity and compared the conclusions drawn from multiple statistical tests with those from the approach of study dissimilarities for transitivity assessment.

METHODS

An empirical study was conducted using 209 published systematic reviews with NMA to create a database of study-level aggregate clinical and methodological characteristics found in the tracenma R package. For each systematic review, the network of the primary outcome was considered to create a dataset with extracted study-level aggregate clinical and methodological characteristics reported in the systematic review that may act as effect modifiers. Transitivity was evaluated by calculating study dissimilarities based on the extracted characteristics to provide a measure of overall dissimilarity within and between the observed treatment comparisons. Empirically driven thresholds of low dissimilarity were employed to determine the proportion of datasets with evidence of likely intransitivity. One-way ANOVA and chi-squared test were employed for each characteristic to investigate comparison dissimilarity at a significance level of 5%.

RESULTS

Study dissimilarities covered a wide range of possible values across the datasets. A 'likely concerning' extent of study dissimilarities, both intra-comparison and inter-comparison, dominated the analysed datasets. Using a higher dissimilarity threshold, a 'likely concerning' extent of study dissimilarities persisted for objective outcomes but decreased substantially for subjective outcomes. A likely intransitivity prevailed in all datasets; however, using a higher dissimilarity threshold resulted in few networks with transitivity for semi-objective and subjective outcomes. Statistical tests were feasible in 127 (61%) datasets, yielding conflicting conclusions with the approach of study dissimilarities in many datasets.

CONCLUSIONS

Study dissimilarity, manifested from variations in the effect modifiers' distribution across the studies, should be expected and properly quantified. Measuring the overall study dissimilarity between observed comparisons and comparing it with a proper threshold can aid in determining whether concerns of likely intransitivity are warranted.

Demonstration of Group-Level and Individual-Level Efficacy Using Time-to-Event Designs for Clinical Trials of Antiseizure Medications

BACKGROUND AND OBJECTIVES

Participants with treatment-resistant epilepsy who are randomized to add-on placebo and remain in a trial for the typical 3 to 5-month maintenance period may be at increased risk of adverse outcomes. A novel trial design has been suggested, time to prerandomization monthly seizure count (T-PSC), which would limit participants' time on ineffective therapy. We reanalyzed 11 completed trials to determine whether the primary efficacy conclusions at T-PSC matched each of the original, longer trials.

METHODS

A total of 11 double-blind, placebo-controlled trials of levetiracetam, brivaracetam, lacosamide, topiramate, and lamotrigine for either focal-onset or generalized-onset epilepsy were selected. We evaluated the group-level and individual-level efficacy of treatments including the median percent reduction (MPR) in seizure frequency and 50% responder rate (50RR) at T-PSC, time to second seizure, and time to first seizure compared with the full-length trial.

RESULTS

The primary efficacy conclusions of 10 of the 11 trials would have been the same with a T-PSC design compared with the traditional design (the exception of lamotrigine had a very high initial placebo response). As a proportion of the full-length effect size, 90% of the MPR and 85% of the 50RR were seen at T-PSC (95% CI 73%-113% and 65%-110%, respectively). Using the T-PSC design, the time on blinded treatment was at least 312 participant-years shorter (40% of total duration) and 142,000 seizures occurred during this time (60% of total seizures). By contrast, the time to first or second seizure designs reproduced group-level effect size, but the primary efficacy conclusions of each trial and individual-level efficacy correspondence were fair to poor.

DISCUSSION

These results support the use of this trial design for new epilepsy medication trials because this reanalysis of 11 randomized controlled trials demonstrated that observation until T-PSC was sufficient to demonstrate efficacy while potentially improving participant safety by reducing the time of exposure to placebo and inadequate treatment. Despite analysis of 11 trials including 3,619 participants, we did not observe a significant reduction in the group-level effect size, which is directly related to statistical power. The next step is to evaluate whether T-PSC is sufficient to evaluate safety as measured by adverse events.

Placebo response in patients with Dravet syndrome: Post-hoc analysis of two clinical trials

OBJECTIVE

Dravet syndrome is a rare, early childhood-onset epileptic and developmental encephalopathy. Responses to placebo in clinical trials for epilepsy therapies range widely, but factors influencing placebo response remain poorly understood. This study explored placebo response and its effects on safety, efficacy, and quality of life outcomes in patients with Dravet syndrome.

METHODS

We performed exploratory post-hoc analyses of pooled data from placebo-treated patients from the GWPCARE 1B and GWPCARE 2 randomized controlled phase III trials, comparing cannabidiol and matched placebo in 2-18 year old Dravet syndrome patients. All patients had ≥4 convulsive seizures during a baseline period of 4 weeks.

RESULTS

124 Dravet syndrome-treated patients were included in the analysis (2-5 years: n = 35; 6-12 years: n = 52; 13-18 years: n = 37). Convulsive seizures were experienced by all placebo group patients at all timepoints, with decreased median convulsive seizure frequency during the treatment period versus baseline; the number of convulsive seizure-free days was similar to baseline. Convulsive seizure frequency had a nominally significant positive correlation with age and a nominally significant negative correlation with body mass index. Most placebo-treated patients experienced a treatment-emergent adverse event; however, most resolved quickly, and serious adverse events were infrequent. Placebo treatment had very little effect on reported Caregiver Global Impression of Change outcomes versus baseline.

INTERPRETATION

Placebo had little impact on convulsive seizure-free days and Caregiver Global Impression of Change versus baseline, suggesting that these metrics may help differentiate placebo and active treatment effects in future studies. However, future research should further assess placebo responses to confirm these results.

How accurate do self-reported seizures need to be for effective medication management in epilepsy?

Studies suggest that self-reported seizure diaries suffer from 50% under-reporting on average. It is unknown to what extent this impacts medication management. This study used simulation to predict the seizure outcomes of a large heterogeneous clinic population treated with a standardized algorithm based on self-reported seizures. Using CHOCOLATES, a state-of-the-art realistic seizure diary simulator, 100 000 patients were simulated over 10 years. A standard algorithm for medication management was employed at 3 month intervals for all patients. The impact on true seizure rates, expected seizure rates, and time-to-steady-dose were computed for self-reporting sensitivities 0%-100%. Time-to-steady-dose and medication use mostly did not depend on sensitivity. True seizure rate decreased minimally with increasing self-reporting in a non-linear fashion, with the largest decreases at low sensitivity rates (0%-10%). This study suggests that an extremely wide range of sensitivity will have similar seizure outcomes when patients are clinically treated using an algorithm similar to the one presented. Conversely, patients with sensitivity ≤10% would be expected to benefit (via lower seizure rates) from objective devices that provide even small improvements in seizure sensitivity.

Re-evaluating the placebo response in recent canine dietary epilepsy trials

The placebo response is a common phenomenon. Limited evidence is available about its magnitude in canine epilepsy trials, even though it can significantly influence the efficacy evaluation of new treatments. It was hypothesised that the placebo response is diminished when epilepsy trials are conducted in a prospective crossover design. Seizure data spanning six months from three previous multicenter epilepsy studies were analysed. The monthly seizure frequency of 60 dogs diagnosed with idiopathic epilepsy was calculated, comparing baseline data with placebo treatment. Furthermore, differentiation was made between dogs randomised to the placebo group early (Phase 1: first 3 months) or later during the study (Phase 2: second 3 months).The analysis did not reveal any placebo response in terms of monthly seizure frequency. Instead, an increase was noted during the placebo treatment period, with a mean of 2.95 seizures per month compared to 2.30 seizures per month before study entry (p = 0.0378). Additionally, a notable phase effect was observed. Dogs receiving the placebo in the second study phase exhibited a significant increase in monthly seizure frequency compared to baseline (p = 0.0036). Conversely, no significant difference from baseline was observed for dogs receiving the placebo in the first study phase. These findings underscore the considerable variability in placebo responses observed in trials for canine epilepsy, contrasting with previous limited data. The identified phase effect should be carefully considered in the design and evaluation of canine epilepsy trials to ensure a more accurate assessment of efficacy for new treatments.

Effect of antipsychotics and mood stabilisers on metabolism in bipolar disorder: a network meta-analysis of randomised-controlled trials

Background

Antipsychotics and mood stabilisers are gathering attention for the disturbance of metabolism. This network meta-analysis aims to evaluate and rank the metabolic effects of the commonly used antipsychotics and mood stabilisers in treating bipolar disorder (BD).

Methods

Registries including PubMed, Embase, Cochrane Library, Web of Science, Ovid, and Google Scholar were searched before February 15th, 2024, for randomised controlled trials (RCTs) applying antipsychotics or mood stabilisers for BD treatment. The observed outcomes were twelve metabolic indicators. The data were extracted by two reviewers independently, and confirmed by another four reviewers and a corresponding author. The above six reviewers all participated in data analyses. Data extraction was based on PRISMA guidelines, and quality assessment was conducted according to the Cochrane Handbook. Use a random effects model for data pooling. The PROSPERO registration number is CRD42023466669.

Findings

Together, 5421 records were identified, and 41 publications with 11,678 complete-trial participants were confirmed eligible. After eliminating possible sensitivity, risperidone ranked 1st in elevating fasting serum glucose (SUCRA = 90.7%) and serum insulin (SUCRA = 96.6%). Lurasidone was most likely to elevate HbA1c (SUCRA = 82.1%). Olanzapine ranked 1st in elevating serum TC (SUCRA = 93.3%), TG (SUCRA = 89.6%), and LDL (SUCRA = 94.7%). Lamotrigine ranked 1st in reducing HDL (SUCRA = 82.6%). Amisulpride ranked 1st in elevating body weight (SUCRA = 100.0%). For subgroup analyses, quetiapine is more likely to affect indicators of glucose metabolism among male adult patients with bipolar mania, while long-term lurasidone tended to affect glucose metabolism among female patients with bipolar depression. Among patients under 18, divalproex tended to affect glucose metabolism, with lithium affecting lipid metabolism. In addition, most observed antipsychotics performed higher response and remission rates than placebo, and displayed a similar dropout rate with placebo, while no between-group significance of rate was observed among mood stabilisers.

Interpretation

Our findings suggest that overall, antipsychotics are effective in treating BD, while they are also more likely to disturb metabolism than mood stabilisers. Attention should be paid to individual applicability in clinical practice. The results put forward evidence-based information and clinical inspiration for drug compatibility and further research of the BD mechanism.

Funding

The National Key Research and Development Program of China (2023YFC2506200), and the Research Project of Jinan Microecological Biomedicine Shandong Laboratory (No. JNL-2023001B).

Quantifying and controlling the impact of regression to the mean on randomized controlled trials in epilepsy

OBJECTIVE

Randomized controlled trials (RCTs) in epilepsy for drug treatments are plagued by high costs. One potential remedy is to reduce placebo response via better control over regression to the mean (RTM). Here, RTM represents an initial observed seizure rate higher than the long-term average, which gradually settles closer to the average, resulting in apparent response to treatment. This study used simulation to clarify the relationship between eligibility criteria and RTM.

METHODS

Using a statistically realistic seizure diary simulator, the impact of RTM on placebo response and trial efficacy was explored by varying eligibility criteria for a traditional treatment phase II/III RCT for drug-resistant epilepsy.

RESULTS

When the baseline period was included in the eligibility criteria, increasingly larger fractions of RTM were observed (25%-47% vs. 23%-25%). Higher fractions of RTM corresponded with higher expected placebo responses (50% responder rate [RR50]: 2%-9% vs. 0%-8%) and lower statistical efficacy (RR50: 47%-67% vs. 47%-81%). The exclusion of baseline from eligibility criteria was shown to decrease the number of patients needed by roughly 30%.

SIGNIFICANCE

The manipulation of eligibility criteria for RCTs has a predictable and important impact on RTM, and therefore on placebo response; the difference between drug and placebo was more easily detected. This in turn impacts trial efficacy and therefore cost. This study found dramatic improvements in efficacy and cost when baseline was not included in eligibility.

Increasing challenges to trial recruitment and conduct over time

OBJECTIVE

This study was undertaken to evaluate how the challenges in the recruitment and retention of participants in clinical trials for focal onset epilepsy have changed over time.

METHODS

In this systematic analysis of randomized clinical trials of adjunct antiseizure medications for medication-resistant focal onset epilepsy, we evaluated how the numbers of participants, sites, and countries have changed since the first such trial in 1990. We also evaluated the proportion of participants who completed each trial phase and their reasons for early trial exit. We analyzed these trends using mixed effects generalized linear models accounting for the influence of the number of trial sites and trial-specific variability.

RESULTS

The number of participants per site has steadily decreased over decades, with recent trials recruiting fewer than five participants per site (reduction by .16 participants/site/year, p < .0001). Fewer participants also progressed from recruitment to randomization over time (odds ratio = .94/year, p = .014). Concurrently, there has been an increase in the placebo response over time (increase in median percent reduction of .4%/year, p = .02; odds ratio of increase in 50% responder rate of 1.03/year, p = .02), which was not directly associated with the number of sites per trial (p > .20).

SIGNIFICANCE

This historical analysis highlights the increasing challenges with participant recruitment and retention, as well as increasing placebo response. It serves as a call to action to change clinical trial design to address these challenges.

Safety and Tolerability of Lacosamide in Patients With Epilepsy: A Systematic Review and Meta-Analysis

Background: As a third-generation antiseizure medication (ASM), lacosamide (LCM) is recommended worldwide for patients with epilepsy. We aimed to provide more conclusive evidence for the safety and tolerability of LCM in patients with epilepsy. Methods: A systematic search was performed on MEDLINE, Embase, Cochrane Library, CBM, CNKI, IDB, VIP Database, and Wanfang Database from inception to 2021 March, and all studies assessing the safety of LCM were included. A meta-analysis was performed for safety data of LCM. Results: Eighty-three studies involving 12268 populations (11 randomized clinical trials (RCTs), 16 cohort studies, 53 case series, and 3 case reports) were included in our study. Meta-analysis of the total incidence of adverse events (AEs) of LCM was 38.7% [95% CI (35.1%, 45.8%); n=75 studies]. Incidence of withdrawal due to AEs was 10.8% [95% CI (9.1%, 12.6%); n=56 studies], and incidence of serious adverse events (SAEs) was 6.5% [95% CI (4.0%, 8.9%); n=13 studies]. Most AEs were in the nervous system and digestive system. The most common AEs were sedation (15.8%), dizziness (15.7%), fatigue (9.4%), and nausea/vomiting (9.3%). For children, the total incidence of AEs of LCM was 32.8% [95% CI (21.6%, 44.0%); n=16 studies], and the most common AEs were dizziness (8.6%), nausea/vomiting (8.6%), and somnolence (6.8%). Conclusion: Lacosamide is generally safe and well tolerated in patients with epilepsy. Common AEs were sedation, dizziness, and fatigue. It is necessary to pay more attention to the prevention and management of these AEs and conduct more large-scale and high-quality studies to update safety data.

Clinical Management of Drug Resistant Epilepsy: A Review on Current Strategies

Drug resistant epilepsy (DRE) is defined as the persistence of seizures despite at least two syndrome-adapted antiseizure drugs (ASD) used at efficacious daily dose. Despite the increasing number of available ASD, about a third of patients with epilepsy still suffer from drug resistance. Several factors are associated with the risk of evolution to DRE in patients with newly diagnosed epilepsy, including epilepsy onset in the infancy, intellectual disability, symptomatic epilepsy and abnormal neurological exam. Pharmacological management often consists in ASD polytherapy. However, because quality of life is driven by several factors in patients with DRE, including the tolerability of the treatment, ASD management should try to optimize efficacy while anticipating the risks of drug-related adverse events. All patients with DRE should be evaluated at least once in a tertiary epilepsy center, especially to discuss eligibility for non-pharmacological therapies. This is of paramount importance in patients with drug resistant focal epilepsy in whom epilepsy surgery can result in long-term seizure freedom. Vagus nerve stimulation, deep brain stimulation or cortical stimulation can also improve seizure control. Lastly, considering the effect of DRE on psychologic status and social integration, comprehensive care adaptations are always needed in order to improve patients' quality of life.

Clinical Trial Design for Disease-Modifying Therapies for Genetic Epilepsies

Although trials with anti-seizure medications (ASMs) have not shown clear anti-epileptogenic or disease-modifying activity in humans to date, rapid advancements in genomic technology and emerging gene-mediated and gene replacement options offer hope for the successful development of disease-modifying therapies (DMTs) for genetic epilepsies. In fact, more than 26 potential DMTs are in various stages of preclinical and/or clinical development for genetic syndromes associated with epilepsy. The scope of disease-modification includes but is not limited to effects on the underlying pathophysiology, the condition's natural history, epilepsy severity, developmental achievement, function, behavior, sleep, and quality of life. While conventional regulatory clinical trials for epilepsy therapeutics have historically focused on seizure reduction, similarly designed trials may prove ill-equipped to identify these broader disease-modifying benefits. As we look forward to this pipeline of DMTs, focused consideration should be given to the challenges they pose to conventional clinical trial designs for epilepsy therapeutics. Just as DMTs promise to fundamentally alter how we approach the care of patients with genetic epilepsy syndromes, DMTs likewise challenge how we traditionally construct and measure the success of clinical trials. In the following, we briefly review the historical and preclinical frameworks for DMT development for genetic epilepsies and explore the many novel challenges posed for such trials, including the choice of suitable outcome measures, trial structure, timing and duration of treatment, feasible follow-up period, varying safety profile, and ethical concerns.

Pregabalin as adjunctive therapy in adult and pediatric patients with generalized tonic-clonic seizures: A randomized, placebo-controlled trial

OBJECTIVE

Generalized tonic-clonic (GTC) seizures are the most common type of generalized seizure and more common in children than adults. This phase 3 study evaluated the efficacy and safety of pregabalin for GTC seizures in adults and children with epilepsy.

METHODS

This randomized, double-blind, multicenter study evaluated pregabalin (5 mg/kg/day or 10 mg/kg/day) vs placebo as adjunctive therapy for 10 weeks (following a 2-week dose escalation), in pediatric and adult patients (aged 5-65 years) with GTC seizures. Primary endpoint was change in log-transformed 28-day seizure rate during active treatment. Secondary endpoints included responder rates, defined as proportion of patients with ≥50% reduction in 28-day GTC seizure rate from baseline. Safety was monitored throughout.

RESULTS

Of 219 patients, 75, 72, and 72 were randomized to adjunctive pregabalin 5 mg/kg/day, 10 mg/kg/day, and placebo, respectively. Fifteen, 11, and 6 patients discontinued from the 5 mg/kg/day, 10 mg/kg/day, and placebo arms, respectively, most commonly due to adverse events (AEs; 10.7%, 6.9%, and 5.6%, respectively). A nonsignificant change in log-transformed mean 28-day seizure rate was seen with pregabalin 10 mg/kg/day vs placebo (least-squares [LS] mean difference -0.01 [95% confidence interval (CI) -0.19 to 0.16]; P = .8889) and with pregabalin 5 mg/kg/day vs placebo (LS mean difference 0.02 [CI -0.15 to 0.19]; P = .8121). Similar observations were noted for adults and children. No significant differences were seen for secondary endpoints with pregabalin vs placebo, including responder rate. The most common AEs (≥10%) were dizziness, headache, and somnolence. Most were of mild/moderate intensity. Seven patients had serious AEs, with one death in the placebo arm (sudden unexpected death in epilepsy).

SIGNIFICANCE

Adjunctive pregabalin treatment did not change GTC seizure rate in adults or children. The safety profile of pregabalin was similar to that known; treatment was well tolerated with few discontinuations due to AEs.

Is the mechanism of action of antiseizure drugs a key element in the choice of treatment?

About 25 antiseizure drugs are available for the treatment of patients with epilepsy. The choice of the most suited drug for a specific patient is primarily based on the results of the pivotal randomized clinical trials and on the patient's characteristics and comorbidities. Whether or not the mechanism of action of the antiseizure drugs should be also taken into account to better predict the patient's response to the treatment remains a matter of debate. Despite the apparent complexity and diversity of antiseizure drug mechanisms of action, the reality unfortunately remains that they are very close, in particular with regard to their relationship with the pathophysiology of epilepsy. With the only exception of the association between lamotrigine and sodium valproate, there are no clinical data that formally support a synergistic association between certain antiseizure drugs in terms of efficacy. However, anticipating risk of adverse events by limiting as far as possible the combination of drugs, which share the same mechanisms of action, is undoubtedly an important driver of daily therapeutic decisions.

Dose-Ranging Effect of Adjunctive Oral Cannabidiol vs Placebo on Convulsive Seizure Frequency in Dravet Syndrome: A Randomized Clinical Trial

Importance

Clinical evidence supports effectiveness of cannabidiol for treatment-resistant seizures in Dravet syndrome, but this trial is the first to evaluate the 10-mg/kg/d dose.

Objective

To evaluate the efficacy and safety of a pharmaceutical formulation of cannabidiol, 10 and 20 mg/kg/d, vs placebo for adjunctive treatment of convulsive seizures in patients with Dravet syndrome.

Design, Setting, and Participants

This double-blind, placebo-controlled, randomized clinical trial (GWPCARE2) recruited patients from April 13, 2015, to November 10, 2017, with follow-up completed on April 9, 2018. Of 285 patients screened from 38 centers in the United States, Spain, Poland, the Netherlands, Australia, and Israel, 86 were excluded, and 199 were randomized. Patients were aged 2 to 18 years with a confirmed diagnosis of Dravet syndrome and at least 4 convulsive seizures during the 4-week baseline period while receiving at least 1 antiepileptic drug. Data were analyzed from November 16 (date of unblinding) to December 13 (date of final outputs), 2018, based on intention to treat and per protocol.

Interventions

Patients received cannabidiol oral solution at a dose of 10 or 20 mg/kg per day (CBD10 and CBD20 groups, respectively) or matched placebo in 2 equally divided doses for 14 weeks. All patients, caregivers, investigators, and individuals assessing data were blinded to group assignment.

Main Outcomes and Measures

The primary outcome was change from baseline in convulsive seizure frequency during the treatment period. Secondary outcomes included change in all seizure frequency, proportion with at least a 50% reduction in convulsive seizure activity, and change in Caregiver Global Impression of Change score.

Results

Of 198 eligible patients (mean [SD] age, 9.3 [4.4] years; 104 female [52.5%]), 66 were randomized to the CBD10 group, 67 to the CBD20 group, and 65 to the placebo group, and 190 completed treatment. The percentage reduction from baseline in convulsive seizure frequency was 48.7% for CBD10 group and 45.7% for the CBD20 group vs 26.9% for the placebo group; the percentage reduction from placebo was 29.8% (95% CI, 8.4%-46.2%; P = .01) for CBD10 group and 25.7% (95% CI, 2.9%-43.2%; P = .03) for the CBD20 group. The most common adverse events were decreased appetite, diarrhea, somnolence, pyrexia, and fatigue. Five patients in the CBD20 group discontinued owing to adverse events. Elevated liver transaminase levels occurred more frequently in the CBD20 (n = 13) than the CBD10 (n = 3) group, with all affected patients given concomitant valproate sodium.

Conclusions and Relevance

Adjunctive cannabidiol at doses of 10 and 20 mg/kg/d led to similar clinically relevant reductions in convulsive seizure frequency with a better safety and tolerability profile for the 10-mg/kg/d dose in children with treatment-resistant Dravet syndrome. Dose increases of cannabidiol to greater than 10 mg/kg/d should be tailored to individual efficacy and safety.

Trial Registration

ClinicalTrials.gov Identifier: NCT02224703.

Critical Appraisal of Cenobamate as Adjunctive Treatment of Focal Seizures in Adults

Cenobamate (CNB) is the latest antiseizure medication (ASM) authorized for the treatment of focal-onset seizures in adults. Although the precise mechanism of action of CNB is not yet fully understood, this drug inhibits the persistent, rather than transient, voltage-gated sodium channel currents and is a positive allosteric modulator of synaptic and extrasynaptic GABA_A receptors, differently from benzodiazepines. CNB has a non-linear pharmacokinetic with a terminal half-life range of about 50/60 hours within the therapeutic dose range, which allows once daily administration. Cenobamate inhibits cytochrome P450 (CYP) 2C19 and induces CYP3A4 and 2B6, and hence can potentially interact with ASMs (eg, phenytoin, carbamazepine and clobazam) and no-ASMs drugs. In two randomized, double-blind, placebo-controlled trials in patients with focal epilepsies, CNB has shown a particularly good efficacy with a rate of seizure freedom of about 20% during the maintenance period in participants treated with the dose of 400 mg/day. The most common treatment-emergent adverse effects include central nervous system-related symptoms, like dizziness, diplopia, somnolence, and gait disturbances. Safety issues of particular interest are severe skin reactions (drug reaction with eosinophilia and systemic symptoms) and QT shortening, which contraindicates its use in subjects with familial short QT syndrome or in combination with other QT-shortening drugs. The recommended starting dose is 12.5 mg/day, which can be gradually titrated to the target dose (200 mg/day) and further increased up to 400 mg/day. There are several aspects of CNB that need to be still addressed, including the long-term efficacy and the efficacy in patients with generalized seizures. Ongoing studies will clarify these issues. The clinical relevance of the peculiar pharmacokinetics and the pattern of drug-drug interactions also require further investigation.

Pregabalin Population Pharmacokinetic and Exposure-Response Analyses for Focal Onset Seizures in Children (4-16 years) and Adults, to Support Dose Recommendations in Children

Pregabalin is approved in multiple countries as adjunctive therapy for adult patients with focal onset seizures (FOS; previously termed partial onset seizures). This study used population pharmacokinetic (PK) and exposure–response (E‐R) analyses from pooled pregabalin concentration and efficacy data to compare pregabalin exposure and E‐R relationships in pediatric and adult patients with FOS, to support pediatric dosage recommendations. A one‐compartment disposition model was used, with first‐order absorption and body surface area‐normalized creatinine clearance on clearance. Individual pregabalin average steady‐state concentrations were predicted and used in an E‐R analysis of efficacy. The E‐R relationship of pregabalin was similar in pediatric (4–16 years) and adult patients with FOS after accounting for differences in baseline natural log‐transformed 28‐day seizure rate and placebo effect. Population PK simulations showed that children aged 4–16 years and weighing ≥ 30 kg required pregabalin 2.5–10 mg/kg/day to achieve similar pregabalin exposure at steady‐state to adult patients receiving the approved doses of 150–600 mg/day. For children 4–16 years weighing < 30 kg, a higher pregabalin dose of 3.5–14 mg/kg/day was required to achieve equivalent exposure at steady‐state. The results support the dosage guidance provided in the pregabalin prescribing label, whereby pediatric patients (4–16 years) weighing < 30 kg should receive a 40% higher pregabalin dose (per kg of body weight) than patients weighing ≥ 30 kg to achieve similar exposure. Our combined modeling approach may provide guidance for future extrapolation assessment from adult to pediatric patients.

Natural variability in seizure frequency: Implications for trials and placebo

BACKGROUND

Changes in patient-reported seizure frequencies are the gold standard used to test efficacy of new treatments in randomized controlled trials (RCTs). Recent analyses of patient seizure diary data suggest that the placebo response may be attributable to natural fluctuations in seizure frequency, though the evidence is incomplete. Here we develop a data-driven statistical model and assess the impact of the model on interpretation of placebo response.

METHODS

A synthetic seizure diary generator matching statistical properties seen across multiple epilepsy diary datasets was constructed. The model was used to simulate the placebo arm of 5000 RCTs. A meta-analysis of 23 historical RCTs was compared to the simulations.

RESULTS

The placebo 50 %-responder rate (RR50) was 27.3 ± 3.6 % (simulated) and 21.1 ± 10.0 % (historical). The placebo median percent change (MPC) was 22.0 ± 6.0 % (simulated) and 16.7 ± 10.3 % (historical).

CONCLUSIONS

A statistical model of daily seizure count generation which incorporates quantities related to the natural fluctuations of seizure count data produces a placebo response comparable to those seen in historical RCTs. This model may be useful in better understanding the seizure count fluctuations seen in patients in other clinical settings.

Understanding the challenge of comparative effectiveness research in focal epilepsy: A review of network meta-analyses and real-world evidence on antiepileptic drugs

OBJECTIVE

Head-to-head randomized controlled trials (RCTs) are the gold standard for assessing comparative treatment effects. In the absence of direct comparisons between all possible antiepileptic drugs (AEDs), however, clinical decision-making in focal (partial onset) epilepsy relies on alternative evidence borne from indirect comparisons including network meta-analyses (NMAs) and from real-world evidence (RWE) studies. We review NMAs and observational RWE studies comparing AEDs in the adjunctive setting to compare the robustness of these methods and to formulate recommendations for future evidence development.

METHODS

A literature review identified NMAs and RWE studies comparing AEDs for the adjunctive treatment of focal seizures published between January 2008 and October 2018. NMAs were evaluated for robustness using a framework based on guidelines from the National Institute for Health and Care Excellence Decision Support Unit and the International Society for Pharmacoeconomics and Outcomes Research. RWE studies were evaluated using the GRACE checklist.

RESULTS

From a total of 1993 records, 11 NMAs and six RWE studies were eligible. Key limitations identified in the NMAs include nonsystematic selection of RCTs, unexplored heterogeneity between included RCTs in terms of study and patient characteristics, and selection of AEDs and AED doses or dosing strategies that are not reflective of clinical practice. The main limitations of RWE studies concern sample size, design, and analysis methods. Approximately 90% of comparisons between individual AEDs were nonsignificant in the NMAs. None of the RWE studies adjusted for baseline differences between comparator groups; therefore, they lack the validity to make comparative conclusions.

SIGNIFICANCE

Current NMAs and RWE studies provide only nominal comparative evidence for AED treatments in focal epilepsy, and should be used with caution for decision-making due to their methodological limitations. To overcome these hurdles, adherence to methodological guidelines and concerted efforts to collect relevant outcome data in the real world are needed.

Factors Influencing Placebo Responses in Rheumatoid Arthritis Clinical Trials: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Studies

BACKGROUND AND OBJECTIVE

A better understanding of placebo responses and the specific factors influencing these outcomes is important for clinical trial design. We investigated the magnitude of placebo responses at 3 months and the potential factors influencing these outcomes in rheumatoid arthritis (RA) clinical trials.

METHODS

We conducted a systematic review of randomized placebo-controlled trials of pharmacological agents for RA identified from PubMed, Embase, and Cochrane Central Register of Controlled Trials databases. The primary placebo outcome was American College of Rheumatology 20% response rate (ACR20). Data were pooled with a random-effects model. Factors influencing placebo response were assessed by meta-regression analyses. Subgroup analyses were performed for studies conducted in non-Western countries only versus in Western countries (North America and/or Europe) only or both.

RESULTS

The meta-analysis included 88 studies comprising 8406 patients receiving a placebo. The pooled estimate of placebo ACR20 was 29.0% (range 10.0-46.2; 95% confidence interval 27.2-30.9). Placebo ACR20 was negatively associated with trials in non-Western (Asian) countries and patient populations showing an inadequate response to biological disease-modifying antirheumatic drugs (DMARDs) in the multivariable analysis, whereas it was positively associated with the year of publication. No background DMARD treatment was also a negative predictor (albeit statistically non-significant). In subgroup analyses of Western and multiregional studies, study population and publication year were significant factors.

CONCLUSIONS

Our meta-analysis suggests that study location, patient population, and a background DMARD treatment influence placebo ACR20. These along with placebo response temporal profiles have important implications for designing and interpreting RA clinical trials.

From clinical trials of antiepileptic drugs to treatment

Rational prescribing should be based on the assessment of high-quality evidence about the benefits and risks of available treatment options. Because clinical trials, particularly randomized controlled trials (RCTs), provide the best source of evidence, their design and results need to be carefully scrutinized. The majority of RCTs of antiepileptic drugs (AEDs) have been designed to address regulatory requirements, and generally they involve restrictive eligibility criteria, rigid dosing schemes, short duration of follow-up, and comparison with placebo rather than standard treatments. Although these studies have high internal validity, they are conducted in a setting that is distant from routine clinical practice and therefore their usefulness in guiding treatment decisions is limited. Information more directly applicable to clinical practice can be derived from a relatively small number of comparative effectiveness monotherapy RCTs, although the design of some of these studies was probably biased in favor of the sponsor's product. Alarmingly, there is a paucity of well-designed trials in epilepsy syndromes other than focal epilepsies, and no RCTs at all in most of the less common epileptic syndromes of infancy and childhood. In the light of these shortcomings, there is scope for re-assessing regulatory requirements to facilitate generation of data more directly applicable to the routine clinical setting. Likewise, research-funding organizations should be sensitized about the lack of adequate evidence to guide therapeutic practice in epilepsy, and the need to promote high-quality comparative effectiveness trials. Future prospective pragmatic trials may benefit from the increasingly widespread availability of electronic health records.

Is seizure frequency variance a predictable quantity?

Background

There is currently no formal method for predicting the range expected in an individual's seizure counts. Having access to such a prediction would be of benefit for developing more efficient clinical trials, but also for improving clinical care in the outpatient setting.

Methods

Using three independently collected patient diary datasets, we explored the predictability of seizure frequency. Three independent seizure diary databases were explored: SeizureTracker (n = 3016), Human Epilepsy Project (n = 93), and NeuroVista (n = 15). First, the relationship between mean and standard deviation in seizure frequency was assessed. Using that relationship, a prediction for the range of possible seizure frequencies was compared with a traditional prediction scheme commonly used in clinical trials. A validation dataset was obtained from a separate data export of SeizureTracker to further verify the predictions.

Results

A consistent mathematical relationship was observed across datasets. The logarithm of the average seizure count was linearly related to the logarithm of the standard deviation with a high correlation (R² > 0.83). The three datasets showed high predictive accuracy for this log-log relationship of 94%, compared with a predictive accuracy of 77% for a traditional prediction scheme. The independent validation set showed that the log-log predicted 94% of the correct ranges while the RR50 predicted 77%.

Conclusion

Reliably predicting seizure frequency variability is straightforward based on knowledge of mean seizure frequency, across several datasets. With further study, this may help to increase the power of RCTs, and guide clinical practice.

A multi-dataset time-reversal approach to clinical trial placebo response and the relationship to natural variability in epilepsy

PURPOSE

Clinical epilepsy drug trials have been measuring increasingly high placebo response rates, up to 40%. This study was designed to examine the relationship between the natural variability in epilepsy, and the placebo response seen in trials. We tested the hypothesis that 'reversing' trial direction, with the baseline period as the treatment observation phase, would reveal effects of natural variability.

METHOD

Clinical trial simulations were run with time running forward and in reverse. Data sources were: SeizureTracker.com (patient reported diaries), a randomized sham-controlled TMS trial, and chronically implanted intracranial EEG electrodes. Outcomes were 50%-responder rates (RR50) and median percentage change (MPC).

RESULTS

The RR50 results showed evidence that temporal reversal does not prevent large responder rates across datasets. The MPC results negative in the TMS dataset, and positive in the other two.

CONCLUSIONS

Typical RR50s of clinical trials can be reproduced using the natural variability of epilepsy as a substrate across multiple datasets. Therefore, the placebo response in epilepsy clinical trials may be attributable almost entirely to this variability, rather than the "placebo effect".

Does accounting for seizure frequency variability increase clinical trial power?

OBJECTIVE

Seizure frequency variability is associated with placebo responses in randomized controlled trials (RCT). Increased variability can result in drug misclassification and, hence, decreased statistical power. We investigated a new method that directly incorporated variability into RCT analysis, Z_V.

METHODS

Two models were assessed: the traditional 50%-responder rate (RR50), and the variability-corrected score, Z_V. Each predicted seizure frequency upper and lower limits using prior seizures. Accuracy was defined as percentage of time-intervals when the observed seizure frequencies were within the predicted limits. First, we tested the Z_V method on three datasets (SeizureTracker: n=3016, Human Epilepsy Project: n=107, and NeuroVista: n=15). An additional independent SeizureTracker validation dataset was used to generate a set of 200 simulated trials each for 5 different sample sizes (total N=100 to 500 by 100), assuming 20% dropout and 30% drug efficacy. "Power" was determined as the percentage of trials successfully distinguishing placebo from drug (p<0.05).

RESULTS

Prediction accuracy across datasets was, Z_V: 91-100%, RR50: 42-80%. Simulated RCT Z_V analysis achieved >90% power at N=100 per arm while RR50 required N=200 per arm.

SIGNIFICANCE

Z_V may increase the statistical power of an RCT relative to the traditional RR50.

Tolerability of new antiepileptic drugs: a network meta-analysis

OBJECTIVE

The objective of this study was to perform a comparative assessment of tolerability of all licensed new antiepileptic drugs (AEDs) through a network meta-analysis (NMA) including all placebo-controlled double-blind clinical trials (RCTs) in all conditions in which these drugs have been tested.

METHODS

NMA with a frequentist approach was used to compare proportions of patients withdrawing because of adverse events (AEs). Analyses were conducted for all therapeutic doses pooled and specifically for high therapeutic doses. Patients treated with non-therapeutic doses of each drug were excluded.

RESULTS

A total of 195 RCTs were included in the current analysis, comprising a total of 28,013 patients treated with AEDs and 17,908 patients treated with placebo. RCTs included in the analysis were 8 for brivaracetam; 5 for eslicarbazepine; 22 for gabapentin; 7 for lacosamide; 14 for levetiracetam; 14 for lamotrigine; 6 for oxcarbazepine; 9 for perampanel; 50 for pregabalin; 5 for tiagabine; 36 for topiramate; 7 for zonisamide; 4 for gabapentin-extended formulation (ER); 2 each for levetiracetam-ER, lamotrigine-ER, and topiramate-ER; and 1 each for oxcarbazepine-ER and pregabalin-ER. Brivaracetam, gabapentin, gabapentin-ER, and levetiracetam had a significantly lower withdrawal rate compared to several other AEDs, while eslicarbazepine, lacosamide, oxcarbazepine, and topiramate had a higher withdrawal rate. Perampanel, lamotrigine, pregabalin, tiagabine, and zonisamide showed an intermediate pattern of tolerability. Additional analysis has been conducted through selection of highly recommended doses for each drug. This analysis has roughly confirmed results of head to head comparisons of the all-dose analysis, with some exceptions. A further analysis has been conducted after exclusion of RCTs in which patients were allocated to the therapeutic dose of the experimental drug without titration, and it failed to show clinically important differences.

SIGNIFICANCE

Relevant differences in short-term tolerability of AEDs have been observed between AEDs. Brivaracetam, gabapentin, and levetiracetam show the best tolerability profile while other AEDs are at higher risk for intolerable adverse effects.

Simulating Clinical Trials With and Without Intracranial EEG Data

OBJECTIVE

It is currently unknown if knowledge of clinically silent (electrographic) seizures improves the statistical efficiency of clinical trials.

METHODS

Using data obtained from 10 patients with chronically implanted subdural electrodes over an average of 1 year, a Monte Carlo bootstrapping simulation study was performed to estimate the statistical power of running a clinical trial based on A) patient reported seizures with intracranial EEG (icEEG) confirmation, B) all patient reported events, or C) all icEEG confirmed seizures. A "drug" was modeled as having 10%, 20%, 30%, 40% and 50% efficacy in 1000 simulated trials each. Outcomes were represented as percentage of trials that achieved p<0.05 using Fisher Exact test for 50%-responder rates (RR50), and Wilcoxon Rank Sum test for median percentage change (MPC).

RESULTS

At each simulated drug strength, the MPC method showed higher power than RR50. As drug strength increased, statistical power increased. For all cases except RR50 with drug of 10% efficacy, using patient reported events (with or without icEEG confirmation) was not as statistically powerful as using all available intracranially confirmed seizures (p<0.001).

SIGNIFICANCE

This study demonstrated using simulation that additional accuracy in seizure detection using chronically implanted icEEG improves statistical power of clinical trials. Newer invasive and noninvasive seizure detection devices may have the potential to provide greater statistical efficiency, accelerate drug discovery and lower trial costs.

Can Matching-Adjusted Indirect Comparison Methods Mitigate Placebo Response Differences Among Patient Populations in Adjunctive Trials of Brivaracetam and Levetiracetam?

BACKGROUND AND OBJECTIVE

Patients with focal seizures recruited into adjunctive antiepileptic drug (AED) trials have become more refractory and severe over time; concurrently, placebo responses have increased. To attempt to account for heterogeneity among trials, propensity-score weighted patient-level data were used to indirectly compare placebo responses reported in brivaracetam and levetiracetam trials.

METHODS

Patient-level data from randomised, placebo-controlled brivaracetam (recruited 2007-2014) and levetiracetam (1993-1998) trials were pooled. Consistent inclusion/exclusion criteria were applied and outcomes were defined consistently. Potentially confounding baseline characteristics were adjusted for using propensity score weighting. Weighting success was assessed using placebo response.

RESULTS

In total, 707 and 473 active drug and 399 and 253 placebo patients comprised the brivaracetam and levetiracetam groups, respectively. Before weighting, several baseline variables were significantly different between groups; after weighting, prior vagal nerve stimulation, co-morbid depression and co-morbid anxiety remained different. Before weighting, median seizure frequency reduction was 21.7 and 3.9% in the brivaracetam and levetiracetam placebo arms, respectively; after weighting, median reduction was 15.0 and 6.0%. The comparison of non-randomised groups could be biased by unobserved confounding factors and region of residence. Lifetime AED history was unavailable in the brivaracetam trials and excluded from analysis.

CONCLUSIONS

Placebo responses remained different between brivaracetam and levetiracetam trials after propensity score weighting, indicating the presence of residual confounding factors associated with placebo response in these trials. It therefore remains problematic to conduct reliable indirect comparisons of brivaracetam and levetiracetam given the current evidence base, which may apply to comparisons between other AED trials.

Adjunctive pregabalin vs gabapentin for focal seizures: Interpretation of comparative outcomes

Objective:

To evaluate the comparative safety and adjunctive efficacy of pregabalin and gabapentin in reducing seizure frequency in patients with partial-onset seizures based on prestudy modeling showing superior efficacy for pregabalin.

Methods:

The design of this comparative efficacy and safety study of pregabalin and gabapentin as adjunctive treatment in adults with refractory partial-onset seizures was randomized, flexible dose, double blind, and parallel group. The study included a 6-week baseline and a 21-week treatment phase. The primary endpoint was the percentage change from baseline in 28-day seizure rate to the treatment phase.

Results:

A total of 484 patients were randomized to pregabalin (n = 242) or gabapentin (n = 242). Of these, 359 patients (187 pregabalin, 172 gabapentin) completed the treatment phase. The observed median and mean in percentage change from baseline was −58.65 and −47.7 (SD 48.3) for pregabalin and −57.43 and −45.28 (SD 60.6) for gabapentin. For the primary endpoint, there was no significant difference between treatments. The Hodges-Lehman estimated median difference was 0.0 (95% confidence interval −6.0 to 7.0). Safety profiles were comparable and consistent with prior trials.

Conclusions:

The absence of the anticipated efficacy difference based on modeling of prior, nearly identical trials and the larger-than-expected response rates of the 2 antiepileptic drugs were unexpected. These findings raise questions that are potentially important to consider in future comparative efficacy trials.

ClinicalTrials.gov identifier:

NCT00537940.

Classification of evidence:

This study provides Class II evidence that for patients with partial seizures enrolled in this study, pregabalin is not superior to gabapentin in reducing seizure frequency. Because of the atypical response rates, the results of this study are poorly generalizable to other epilepsy populations.

Not all that glitters is gold: A guide to the critical interpretation of drug trials in epilepsy

Clinical trials represent the best source of evidence on which to base treatment decisions. For such evidence to be utilized meaningfully, however, it is essential that results are interpreted correctly. This requires a good understanding of strengths and weaknesses of the adopted design, the clinical relevance of the outcome measures, and the many factors that could affect such outcomes. As a general rule, uncontrolled studies tend to provide misleading evidence as a result of the impact of confounders such as regression to the mean, patient‐related bias, and observer bias. On the other hand, although randomized controlled trials (RCTs) are qualitatively superior, aspects of their execution may still decrease their validity. Bias and decreased validity in RCTs may occur by chance alone (for example, treatment groups may not necessarily be balanced for important variables despite randomization) or because of specific features of the trial design. In the case of industry‐driven studies, bias often influences the outcome in favor of the sponsor's product. Factors that need to be carefully scrutinized include (1) the purpose for which the trial is conducted; (2) potential bias due to unblinding or lack of blinding; (3) the appropriateness of the control group; (4) the power of the study in detecting clinically relevant differences; (5) the extent to which eligibility criteria could affect outcomes and be representative of routine clinical practice; (6) whether the treatments being compared are used optimally in terms of dosing, duration of treatment, and other variables; (7) the appropriateness of the statistical comparisons; (8) the clinical relevance of the outcome measures and whether all key outcome information is reported (for example, responder rates in completers); and (9) potential bias in the way results are presented and discussed. This article discusses each of these aspects and illustrates the discussion with examples taken from published antiepileptic drug trials.

Emerging drugs for partial-onset epilepsy: a review of brivaracetam

There are more than 12 new antiepileptic drugs approved in the last 2 decades. Even with these newer agents, seizure remission is still unachievable in around 30% of patients with partial-onset seizures (POS). Brivaracetam (BRV) is chemically related to levetiracetam (LEV) and possesses a strong binding affinity for the synaptic vesicle protein 2A tenfold above that of LEV, and other possible modes of antiepileptic actions. BRV is now under Phase III development for POS, but data from one Phase III trial also suggested its potential efficacy for primary generalized seizures. The purpose of this review is to provide updated information on the mechanisms of action of the available antiepileptic drugs, with a focus on BRV to assess its pharmacology, pharmacokinetics, clinical efficacy, safety, and tolerability in patients with uncontrolled POS. To date, six Phase IIb and III clinical trials have been performed to investigate the efficacy, safety, and tolerability of BRV as an adjunctive treatment for patients with POS. Generally, BRV was well tolerated and did not show significant difference in safety profile, compared to placebo. The efficacy outcomes of BRV, although not consistent across trials, did indicate that BRV was a promising add-on therapy for patients with POS. In conclusion, the many favorable attributes of BRV, like its high oral efficacy, good tolerability, dosing regimen, and minimal drug interaction, make it a promising antiepileptic therapy for patients with uncontrolled partial-onset epilepsy.

Response to placebo in clinical epilepsy trials--Old ideas and new insights

Randomized placebo-controlled trials are a mainstay of modern clinical epilepsy research; the success or failure of innovative therapies depends on proving superiority to a placebo. Consequently, understanding what drives response to placebo (including the "placebo effect") may facilitate evaluation of new therapies. In this review, part one will explore observations about placebos specific to epilepsy, including the relatively higher placebo response in children, apparent increase in placebo response over the past several decades, geographic variation in placebo effect, relationship to baseline epilepsy characteristics, influence of nocebo on clinical trials, the possible increase in (SUDEP) in placebo arms of trials, and patterns that placebo responses appear to follow in individual patients. Part two will discuss the principal causes of placebo responses, including regression to the mean, anticipation, classical conditioning, the Hawthorne effect, expectations from symbols, and the natural history of disease. Included in part two will be a brief overview of recent advances using simulations from large datasets that have afforded new insights into causes of epilepsy-related placebo responses. In part three, new developments in study design will be explored, including sequential parallel comparison, two-way enriched design, time to pre-randomization, delayed start, and cohort reduction techniques.

Confusing placebo effect with natural history in epilepsy: A big data approach

For unknown reasons, placebos reduce seizures in clinical trials in many patients. It is also unclear why some drugs showing statistical superiority to placebo in one trial may fail to do so in another. Using Seizuretracker.com, a patient-centered database of 684,825 seizures, we simulated "placebo" and "drug" trials. These simulations were employed to clarify the sources of placebo effects in epilepsy, and to identify methods of diminishing placebo effects. Simulation 1 included 9 trials with a 6-week baseline and 6-week test period, starting at time 0, 3, 6…24 months. Here, "placebo" reduced seizures regardless of study start time. Regression-to-the-mean persisted only for 3 to 6 months. Simulation 2 comprised a 6-week baseline and then 2 years of follow-up. Seizure frequencies continued to improve throughout follow-up. Although the group improved, individuals switched from improvement to worsening and back. Simulation 3 involved a placebo-controlled "drug" trial, to explore methods of placebo response reduction. An efficacious "drug" failed to demonstrate a significant effect compared with "placebo" (p = 0.12), although modifications either in study start time (p = 0.025) or baseline population reduction (p = 0.0028) allowed the drug to achieve a statistically significant effect compared with placebo. In epilepsy clinical trials, some seizure reduction traditionally attributed to placebo effect may reflect the natural course of the disease itself. Understanding these dynamics will allow future investigations into optimal clinical trial design and may lead to identification of more effective therapies. Ann Neurol 2015;78:329-336.

Predictors of placebo response in peripheral neuropathic pain: insights from pregabalin clinical trials

Background

Greater understanding of factors associated with the high placebo-response rates noted in recent neuropathic pain trials may improve trial design. This study investigated placebo response and its predictors in pregabalin trials in patients with diabetic peripheral neuropathy (DPN) or postherpetic neuralgia.

Patients and methods

Individual patient data from 16 randomized, placebo-controlled, double-blind trials of pregabalin in 3,053 patients with DPN and 1,460 patients with postherpetic neuralgia were pooled (by condition and all together) in order to investigate the placebo response and its predictors. Univariate and multivariate analyses were performed across all 16 trials to identify predictors of change in pain score in patients. Trials with a >2-point mean reduction in pain score at endpoint with placebo were designated high placebo response and were compared with low placebo-response trials (those with a ≤2-point mean reduction) with respect to patient and study characteristics.

Results

Three high placebo-response studies were identified, with all in DPN patients and all conducted postapproval of pregabalin. Younger age, higher mean baseline pain score, longer study duration, higher ratio of patients on active treatment to placebo, and study conducted postapproval were all significantly associated with a higher placebo response (P<0.05). There was a trend towards an increased placebo response in all studies over time without any corresponding change in the response to pregabalin.

Conclusion

Consideration of the factors identified here as contributing to a higher placebo response could help improve the sensitivity and accuracy of clinical trials in patients with neuropathic pain.

Characterization of the adverse events profile of placebo-treated patients in randomized controlled trials on drug-resistant focal epilepsies

In epilepsy trials a substantial proportion of patients receiving placebo has some improvement or experience adverse events (AEs) which match those related to active drug. The characterization of factors influencing these responses is crucial for a better comprehension of study results and to improve design of new trials. Seventy-one placebo-controlled, double-blind trials in drug-resistant focal epilepsies has been selected. The effect of multiple factors on some outcome measures were explored using a meta-regression model. For subjective and objective AEs, risk difference (RD) was calculated and entered in an inverse variance-weighted linear meta-regression model as independent variable to evaluate the relationship with data reported in placebo-treated patients. The number of study arms influence the percentage of patients withdrawing because of AEs and the highest dose of the experimental drug used in each RCT correlates with withdrawal because of AEs and with subjective AEs. Higher titration speed is associated with lower percentages of responders and higher reporting of both objective and subjective AEs. The correlation between proportions of placebo-treated patients with subjective and objective neurological AEs and relative RD, was significant (P = 0.002 r = 0.364 and P < 0.001 r = 0.650, respectively). Efficacy and tolerability outcomes of the placebo groups are intrinsically tied to the trial methodology and to the outcomes observed in patients treated with the active drug. The correlation for objective and subjective AEs between RD and the placebo-treated patients suggest that investigators are influenced by factors which operate within each specific trial.

Network meta-analyses of antiepileptic drug efficacy and tolerability in drug-resistant focal epilepsies: a clinical perspective

PURPOSE

Network meta-analysis (NMA) is a new technique that allows multiple treatment comparisons and provides estimates of effect sizes for all possible pair-wise comparisons. Several NMAs of antiepileptic drug (AED) efficacy and tolerability in individuals with refractory focal epilepsy, however, came to non-specific and, in some cases, divergent conclusions. We review some clinical factors that may be responsible for these inconsistent findings.

RESULTS

A major issue is the small number of individuals included in the meta-analyses with consequent wide confidence intervals and lack of ability to achieve significant results. Further issues are lack of robustness of the measured efficacy outcome-the responder ratio (the percentage of individuals with a >50 % improvement in seizure frequency); the selection of randomized studies (RCTs) included, i.e., the inclusion of studies with heterogeneous populations (children and adults); and inclusion of people treated with different doses of the experimental drug. Some methods of analysing data from RCTs, such as the last observation carried forward (LOCF) analysis, the choice of different phases of the study to compare to baseline, and the year in which the trial was conducted, selectively affect measurement of efficacy outcomes. Titration speed and other methodological aspects selectively affect tolerability.

CONCLUSION

Several factors restrict the analysis of clinically useful estimates of the comparative efficacy of AEDs, while analysis of tolerability may be easier to accomplish.

Efficacy and safety of extended-release oxcarbazepine (Oxtellar XR™) as adjunctive therapy in patients with refractory partial-onset seizures: a randomized controlled trial

Objective

To evaluate the efficacy, tolerability, and safety of once-daily 1200 mg and 2400 mg SPN-804 (Oxtellar XR™, Supernus Pharmaceuticals), an extended-release tablet formulation of oxcarbazepine (OXC), added to 1-3 concomitant antiepileptic drugs (AEDs) in adults with refractory partial-onset seizures, with or without secondary generalization.

Methods

The Prospective, Randomized Study of OXC XR in Subjects with Partial Epilepsy Refractory (PROSPER) study was a multinational, randomized, double-blind, parallel-group Phase 3 study. The primary efficacy endpoint was median percent reduction from baseline in monthly (28-day) seizure frequency for the 16-week double-blind treatment period in the intent-to-treat (ITT) population with analyzable seizure data. Other efficacy analyses included proportion of patients with ≥ 50% seizure reduction, proportion of patients seizure free, and the relationship between clinical response and plasma concentration.

Results

Median percent reduction was -28.7% for placebo, −38.2% (P = 0.08 vs placebo) for once-daily SPN-804 1200 mg, and −42.9% (P = 0.003) for SPN-804 2400 mg. Responder rates were 28.1%, 36.1% (P = 0.08), and 40.7% (P = 0.02); 16-week seizure-free rates in a pragmatic ITT analysis were 3.3%, 4.9% (P = 0.59), and 11.4% (P = 0.008), respectively. When data were analyzed separately for study site clusters, a post hoc analysis demonstrated that both SPN-804 dosages were significantly superior to placebo in median percent seizure reduction (placebo: −13.3%; 1200 mg: −34.5%, P = 0.02; 2400 mg: −52.7%, P = 0.006) in the North American study site cluster. A concentration–response analysis also supported a clinically meaningful effect for 1200 mg. Adverse event types reflected the drug's established profile. Adverse event frequency was consistent with a pharmacokinetic profile in which SPN-804 produces lower peak plasma concentrations vs immediate-release OXC. Once-daily dosing was not associated with any new safety signals.

Conclusions

Adjunctive once-daily SPN-804 improved seizure control in patients with inadequately controlled partial-onset seizures. Adverse event occurrence and discontinuations due to adverse events suggest improved tolerability vs previously published data with immediate-release OXC.

Comparative efficacy and tolerability of anti-epileptic drugs for refractory focal epilepsy: systematic review and network meta-analysis reveals the need for long term comparator trials

AIMS

To evaluate the comparative efficacy (50% reduction in seizure frequency) and tolerability (premature withdrawal due to adverse events) of anti-epileptic drugs (AEDs) for refractory epilepsy.

METHODS

We searched Cochrane Central Register of Controlled Trials (Cochrane Library 2009, issue 2) including Epilepsy Group's specialized register, MEDLINE (1950 to March 2009), EMBASE (1980 to March 2009), and Current Contents Connect (1998 to March 2009) to conduct a systematic review of published studies, developed a treatment network and undertook a network meta-analysis.

RESULTS

Forty-three eligible trials with 6346 patients and 12 interventions, including placebo, contributed to the analysis. Only three direct drug comparator trials were identified, the remaining 40 trials being placebo-controlled. Conventional random-effects meta-analysis indicated all drugs were superior in efficacy to placebo (overall odds ratio (OR] 3.78, 95% CI 3.14, 4.55) but did not permit firm distinction between drugs on the basis of the efficacy or tolerability. A Bayesian network meta-analysis prioritized oxcarbazepine, topiramate and pregabalin on the basis of short term efficacy. However, sodium valproate, levetiracetam, gabapentin and vigabatrin were prioritized on the basis of short-term efficacy and tolerability, with the caveat that vigabatrin is recognized as being associated with serious visual disturbance with chronic use.

CONCLUSION

Of the wide range of AEDs licensed for the treatment of refractory epilepsy, sodium valproate, levetiracetam and gabapentin demonstrated the best balance of efficacy and tolerability. Until regulators mandate greater use of active comparator trials with longer term follow-up, network meta-analysis provides the only available means to quantify these clinically important parameters.

Adjunctive brivaracetam in adults with uncontrolled focal epilepsy: results from a double-blind, randomized, placebo-controlled trial

PURPOSE

Brivaracetam (BRV) is a novel high-affinity synaptic vesicle protein 2A ligand in clinical development for the treatment of epilepsy. This phase III study (N01252; NCT00490035) evaluated the efficacy and safety/tolerability of BRV (20, 50, and 100 mg/day) compared with placebo (PBO) in patients aged 16-70 years with uncontrolled focal seizures with/without secondary generalization, despite treatment with one to two concomitant antiepileptic drugs at a stable and optimal dosage.

METHODS

This was a double-blind, randomized, placebo-controlled trial conducted across Europe and India. Eligible patients had two or more focal seizures/month for 3 months prior to screening and eight or more focal seizures during the 8-week prospective baseline. Concomitant use of levetiracetam was limited to 20% of randomized patients. Patients were randomized (1:1:1:1) to BRV 20, 50, 100 mg/day or PBO with no up-titration for 12 weeks, followed by down-titration or entry into a long-term follow-up study. The primary efficacy end point was percent reduction over PBO in baseline-adjusted focal seizure frequency/week over the 12-week treatment period. Comparison of BRV with PBO was sequential to control for multiplicity (50, 100, 20 mg/day), and thus required BRV to demonstrate superiority over PBO at 50 mg/day to meet the primary efficacy end point. Secondary efficacy variables were median percent reduction from baseline in focal seizure frequency/week, ≥50% responder rate, and seizure freedom (all seizure types). Safety assessments included treatment-emergent adverse events (TEAEs).

KEY FINDINGS

Of 399 randomized patients, 398 were included in the intent-to-treat (ITT) and safety populations. Overall, 367 (92.2%) of 398 patients completed the study (BRV: 93.9%, 88.9%, and 94.0% for 20, 50, and 100 mg/day, respectively; PBO: 92.0%) and 345 (86.7%) of 398 patients continued into long-term follow-up studies (BRV: 87.9%, 82.8%, and 88.0% for 20, 50, and 100 mg/day, respectively; PBO: 88.0%). The study did not meet its primary efficacy end point based on the predefined sequential testing strategy. Indeed, percent reduction over PBO in baseline-adjusted focal seizure frequency/week (primary efficacy analysis) was 6.8% (p = 0.239), 6.5% (p = 0.261), and 11.7% (p = 0.037) for BRV 20, 50, and 100 mg/day, respectively. Median percent reduction from baseline in focal seizure frequency/week was 30.0% (p = 0.019), 26.8% (p = 0.092), and 32.5% (p = 0.004) for BRV 20, 50, and 100 mg/day, respectively, compared with 17.0% for PBO. Responder rates (≥50%) were 27.3% (p = 0.339), 27.3% (p = 0.372), and 36.0% (p = 0.023) for BRV 20, 50, and 100 mg/day, respectively, compared with 20.0% for PBO. Complete seizure freedom was reported by 2/99, 0/99, and 4/100 patients on BRV 20, 50, and 100 mg/day, respectively, compared with 0/100 on PBO. The incidence of TEAEs was higher for BRV 20 (56/99, 56.6%), 50 (62/99, 62.6%), and 100 mg/day (63/100, 63.0%) than PBO (53/100, 53.0%); most TEAEs were mild or moderate in severity. The most frequently reported TEAEs in the BRV groups were headache, somnolence, dizziness, and fatigue.

SIGNIFICANCE

In this study of adjunctive BRV (20-100 mg/day) in adults with uncontrolled focal seizures, the primary efficacy analysis based on the 50 mg/day dose was not statistically significant. However, BRV 100 mg/day reduced baseline-adjusted focal seizure frequency/week by 11.7% over PBO, achieving statistical significance (p = 0.037). Secondary efficacy analyses (percent reduction from baseline in focal seizure frequency/week, ≥50% responder rate) provided supportive evidence for the efficacy of BRV 100 mg/day. BRV 20-100 mg/day was well tolerated without up-titration, with a high completion rate.

Investigation of influencing factors on higher placebo response in East Asian versus Western clinical trials for partial epilepsy: a meta-analysis

BACKGROUND

Placebo response in clinical trials for anti-epileptic drugs (AEDs) has been examined and a recent meta-analysis revealed that East Asian trials showed unexpectedly higher placebo response. As multi-national trials have become common, it is important to understand placebo response in different settings, including regions/countries for future clinical trials.

OBJECTIVE

The present meta-analysis aims to investigate the potential factors that contribute to higher placebo response in clinical trials for add-on therapy to adult patients with refractory partial epilepsy in East Asian and Western populations.

METHODS

A database was established based on published clinical trials conducted in East Asian and Western countries. The relationship between the degree of placebo response and potential influencing factors was examined by logistic regression analyses.

RESULTS

The database included 33 trials from five AEDs: gabapentin, topiramate, levetiracetam, pregabalin, and zonisamide. Placebo response was associated with patient characteristics such as disease duration, percentage of patients with complex partial seizure (CPS) at baseline, percentage of patients treated with two AEDs, protocol-required seizure frequency at baseline, and year of publication. Logistic regression analysis demonstrated that the placebo response in East Asian trials was statistically higher than that in Western trials.

CONCLUSION

Patient characteristics such as longer disease duration and CPS at baseline contribute to a reduction in placebo response in clinical trials of AEDs for partial epilepsy. While the reasons for the geographical difference in placebo response are not clear, these and other patient characteristics contributing to placebo response should be carefully considered in the design of future clinical trials of AEDs for partial epilepsy.

Profile of perampanel and its potential in the treatment of partial onset seizures

Perampanel (PER) is a novel antiepileptic compound that decreases neuronal excitability by modulating glutamatergic transmission through selective noncompetitive blockade of AMPA receptors. PER has been evaluated in three pivotal placebo-controlled randomized trials as adjunctive therapy in adult drug-resistant partial epilepsy. In comparison to placebo, adjunctive PER effectively reduces seizure frequency. The relative risk of the responder rate (95% confidence interval [CI]) was thus 1.60 (1.08-2.36), 1.79 (1.42-2.25) and 1.66 (1.24-2.23) for once-daily PER 4 mg/day, 8 mg/day and 12 mg/day, respectively. The most common adverse events associated with PER were nonspecific central nervous system side effects. Some concerns have been raised about risk of clinically significant weight gain and of psychiatric adverse events. Long-term open-label extensions of the three pivotal trials are underway. PER has recently been approved both in Europe and in the USA for the adjunctive treatment of partial onset seizures in patients aged 12 years and above. However, in the absence of a direct comparison between PER and other licensed antiepileptic drugs' efficacy and tolerability, the clinical advantages of PER over the other drugs in intractable partial epilepsy remains to be determined.

Levetiracetam add-on for drug-resistant focal epilepsy: an updated Cochrane Review

BACKGROUND

Epilepsy is an important neurological condition and drug resistance in epilepsy is particularly common in individuals with focal seizures. In this review, we summarise the current evidence regarding a new antiepileptic drug, levetiracetam, when used as add-on treatment for controlling drug-resistant focal epilepsy. This is an update to a Cochrane Review that was originally published in 2001.

OBJECTIVES

To evaluate the effectiveness of levetiracetam, added on to usual care, in treating drug-resistant focal epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group's Specialized Register (August 2012), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library Issue 7, 2012), and MEDLINE (1946 to August week 1, 2012). We also contacted the manufacturers of levetiracetam and researchers in the field to seek any ongoing or unpublished trials.

SELECTION CRITERIA

Randomised, placebo-controlled trials of add-on levetiracetam treatment in people with drug-resistant focal epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, assessed trials for bias, extracted data, and evaluated the overall quality of evidence. Outcomes investigated included 50% or greater reduction in focal seizure frequency (response); less than 50% reduction in focal seizure frequency (non-response); treatment withdrawal; adverse effects (including a specific analysis of changes in behaviour); cognitive effects and quality of life (QoL). Risk ratios (RR) with 95% confidence intervals (CIs) were used as measures of effect (99% CIs for adverse effects). Primary analyses were Intention-to-Treat (ITT). Dose response and inter-trial heterogeneity were evaluated in regression models.

MAIN RESULTS

Eleven trials (1861 participants) were included. They predominantly possessed low risks of bias. Participants were adults in nine trials (1565 participants) and children in the remaining two trials (296 participants). The dose of levetiracetam tested was 1000 to 4000 mg/day in adults, and 60 mg/kg/day in children. Treatment ranged from 12 to 24 weeks. For the 50% or greater reduction in focal seizure frequency outcome, the RR was significantly in favour of levetiracetam at all doses. The naive estimates, ignoring dose, showed children (52% responded) as better responders than adults (39% responded) on levetiracetam. 25% of children and 16% of adults responded to placebo. The Number Needed to Treat for an additional beneficial outcome for children and adults was four (95% CI three to seven) and five (95% CI four to six), respectively. The significant levels of statistical heterogeneity between trials on adults precluded valid provision of an overall RR (ignoring dose). Results for the two trials that tested levetiracetam 2000 mg on adults were sufficiently similar to be combined to give an RR for 50% or greater reduction in focal seizure frequency of 4.91 (95% CI 2.75 to 8.77), with an RR of 0.68 (95% CI 0.60 to 0.77) for non-response. At this dose, 37% and 8% of adults were responders in the levetiracetam and placebo groups, respectively. Regression analysis demonstrated that much of the heterogeneity between adult trials was likely to be explained by different doses of levetiracetam tested and different years of trial publication. There was no evidence of statistical heterogeneity between trials on children. For these trials, the RR for 50% or greater reduction in focal seizure frequency was 1.91 (95% CI 1.38 to 2.63), with an RR of 0.68 (95% CI 0.56 to 0.81) for non-response. 27% of children responded. Participants were not significantly more likely to have levetiracetam withdrawn (RR 0.98; 95% CI 0.73 to 1.32 and RR 0.80; 95% CI 0.43 to 1.46 for adults and children, respectively). For adults, somnolence (RR 1.51; 99% CI 1.06 to 2.17) and infection (RR 1.76; 99% CI 1.03 to 3.02) were significantly associated with levetiracetam. Accidental injury was significantly associated with placebo (RR 0.60; 99% CI 0.39 to 0.92). No individual adverse effect was significantly associated with levetiracetam in children. Changes in behaviour were negligible in adults (1% affected; RR 1.79; 99% CI 0.59 to 5.41) but significant in children (23% affected; RR 1.90; 99% CI 1.16 to 3.11). Cognitive effect and QoL outcomes suggested that levetiracetam had a positive effect on cognition and some aspects of QoL in adults. In children, levetiracetam did not appear to alter cognitive function but there was evidence of worsening in certain aspects of child behaviour. The overall quality of evidence used was high.

AUTHORS' CONCLUSIONS

This update adds seven more trials to the original review, which contained four trials. At every dose analysed, levetiracetam significantly reduced focal seizure frequency relative to placebo. This indicates that levetiracetam can significantly reduce focal seizure frequency when it is used as an add-on treatment for both adults and children with drug-resistant focal epilepsy. As there was evidence of significant levels of statistical heterogeneity within this positive effect it is difficult to be precise about the relative magnitude of the effect. At a dose of 2000 mg, levetiracetam may be expected to be 3.9 times more effective than placebo; with 30% of adults being responders at this dose. At a dose of 60 mg/kg/day, levetiracetam may be expected to be 0.9 times more effective than placebo; with 25% of children being responders at this dose. When dose was ignored, children were better responders than adults by around 4% to 13%. The results grossly suggest that one child or adult may respond to levetiracetam for every four or five children or adults, respectively, that have received levetiracetam rather than placebo. The drug seems to be well tolerated in both adults and children although non-specific changes in behaviour may be experienced in as high as 20% of children. This aspect of the adverse-effect profile of levetiracetam was analysed crudely and requires further investigation and validation. It seems reasonable to continue the use of levetiracetam in both adults and children with drug-resistant focal epilepsy. The results cannot be used to confirm longer-term or monotherapy effects of levetiracetam or its effects on generalised seizures. The conclusions are largely unchanged from those in the original review. The most significant contribution of this update is the addition of paediatric data into the analysis.

Lamotrigine XR conversion to monotherapy: first study using a historical control group

The efficacy and safety of lamotrigine extended-release tablets (LTG XR) as monotherapy for partial seizures were evaluated using the conversion-to-monotherapy design, and historical data as the control. This methodology was recently approved by the United States Food and Drug Administration, and this study is the first historical control design in epilepsy to complete enrollment. Patients ≥13 years old with uncontrolled partial epilepsy receiving monotherapy with valproate or a noninducing antiepileptic drug were converted to once-daily LTG XR (250 mg or 300 mg) as monotherapy and were followed up for 12 additional weeks. Efficacy was measured by the proportion of patients meeting predefined escape criteria for seizure worsening compared with aggregated pseudoplacebo control data from 8 previously conducted conversion-to-monotherapy trials. Nonoverlap of the 95% confidence limit for LTG XR and the 95% prediction interval of the historical control denotes efficacy. Of 226 randomized patients, 174 (93 in 300 mg/day group and 81 in 250 mg/day group) started withdrawal of the background AED and were evaluated for escape. In the historical control analysis population, the lower 95% prediction interval of the historical control (65.3%) was not overlapped by the upper 95% confidence limit of either LTG XR (300 mg/day; 37.2%) or LTG XR (250 mg/day; 43.4%). Adverse events were reported in 53% and 61% of patients receiving LTG XR (300 mg/day and 250 mg/day, respectively). LTG XR (250 mg or 300 mg once daily) is effective for conversion-to-monotherapy treatment of partial seizures in patients ≥13 years old.

Levetiracetam add-on for drug-resistant localization related (partial) epilepsy

BACKGROUND

The majority of patients with epilepsy have a good prognosis and their seizures are well controlled by a single antiepileptic drug. However, up to 30% develop refractory seizures, particularly those with partial seizures. In this review, we summarise the current evidence regarding a new antiepileptic drug, levetiracetam, when used as an add-on treatment for drug-resistant localization related (partial) epilepsy.

OBJECTIVES

To evaluate the effects of levetiracetam on seizures, side effects, quality of life and cognition, when used as an add-on treatment for patients with a drug-resistant localization related (partial) epilepsy.

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group trials register, the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2000). In addition, we contacted UCB SA (makers of levetiracetam) and experts in the field to seek any ongoing studies or unpublished studies.

SELECTION CRITERIA

Randomized placebo controlled add-on trials of levetiracetam in patients with a drug-resistant localization related (partial) epilepsy.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted relevant data. The following outcomes were assessed: (a) 50% or greater reduction in total seizure frequency; (b) treatment withdrawal (any reason); (c) side effects; (d) cognitive effects; (e) quality of life. Primary analyses were intention to treat. Sensitivity best and worst case analyses were also undertaken. Summary odds ratios (ORs) were estimated for each outcome. Dose response was evaluated in regression models.

MAIN RESULTS

Four trials (1023 patients) were included. All four trials had data for treatment withdrawal and side effect outcomes. Three trials (904 patients) had data for 50% or greater reduction in seizure frequency. Three trials (595 patients) had data for quality of life and cognitive outcomes. The overall Odds Ratio (OR) (95% Confidence Interval (CI)) for 50% or greater reduction in total seizure frequency outcome was 3.81 (2.78,5.22). Dose regression analysis shows clear evidence that levetiracetam reduces seizure frequency with an increase in efficacy with increasing dose of levetiracetam. Approximately 15% of patients taking 1000 mg and 20-30% of patients taking 3000 mg levetiracetam per day have a 50% or greater reduction in seizure frequency. Patients were not significantly more likely to have levetiracetam withdrawn, OR (95% CI) 1.25 (0.87,1.80). The following side effects were significantly associated with levetiracetam: dizziness 2.36 (1.21, 4.61) and infection 1.82 (1.05, 3.14) whereas accidental injury was significantly associated with placebo 0.55 (0.32, 0.93). Quality of life and cognitive effect outcomes suggest that levetiracetam has a positive effect on cognition and some aspects of quality of life.

REVIEWER'S CONCLUSIONS

Levetiracetam reduces seizure frequency when used as an add-on treatment for patients with a drug-resistant localization related (partial) epilepsy, and seems well tolerated. Minimum effective and maximum tolerated doses have not been identified. The trials reviewed were of 16-24 weeks duration and results cannot be used to confirm longer term effects. Our results cannot be extrapolated to monotherapy or to patients with other seizure types or epilepsy syndromes. Great care should also be taken with any attempt to apply these results to children.