Efficacy Of New Antiepileptic Drugs Research Articles

Management strategies for refractory status epilepticus

Refractory status epilepticus (RSE) is defined as the persistence of either clinical or electrographic seizures despite the administration of appropriate doses of an initial benzodiazepine and suitable second-line antiepileptic drugs (AEDs). The Neurocritical Care Society and the American Epilepsy Society have proposed a treatment paradigm for the management of convulsive status epilepticus (CSE). The third-line therapy in refractory CSE may involve general anesthesia using intravenous midazolam, propofol, or other agents, while recent evidence supports the use of ketamine to manage RSE in both adults and children. However, although these treatment strategies are frequently employed in nonconvulsive status epilepticus (NCSE), the efficacy of AEDs and anesthetics in NCSE has not been thoroughly investigated. Recent evidence has demonstrated the safety and efficacy of newer AEDs, including levetiracetam and lacosamide, in the treatment of status epilepticus (SE) and RSE, which also encompasses NCSE. Use of multiple combinations of various intravenous AEDs can also be considered in NCSE before the administration of general anesthesia. In addition, AEDs alone exhibit limited effectiveness in managing SE for new-onset RSE (NORSE) and its subset, febrile infection-related epilepsy syndrome. Therefore, in cases of refractory status, it is imperative to explore treatment options beyond AEDs, including immunotherapy and the incorporation of a ketogenic diet. The present review suggests treatment approaches for RSE based on subgroups, including CSE, NCSE, and NORSE. A discussion of recent clinical studies on AEDs and anesthetics in the management of RSE, as well as proposed treatment methods for NORSE, is also provided.

Ultrasound-induced seizures in a mouse model of KCNQ2-NEO-DEE

PurposeKCNQ2 neonatal developmental and epileptic encephalopathy (NEO-DEE) is characterized by intractable seizures accompanied by an abnormal neurodevelopment. In a mouse model of NEO-DEE carrying the p.(Thr274Met) variant of Kcnq2, spontaneous generalized seizures occur unexpectedly preventing controlled studies and highlighting the necessity for a customized setup to trigger seizures on demand. We aimed to obtain a stable and objective read-out to control the efficacy of new antiepileptic drugs or to test seizure susceptibility. We developed a protocol to trigger ultrasound-induced seizures (UIS) on demand in this model. MethodsWe tested the ability of our protocol to induce seizures at four developmental stages in the Kcnq2p.(Thr274Met/+) mouse model. We mapped the activated brain regions using c-fos protein labeling 2 h after seizure induction. ResultsWe show that the UIS have the same phenotypic expression and the same severity as spontaneous generalized seizures (SGS) in the Kcnq2-NEO-DEE mouse model. The developmental period during which mice exhibit SGS corresponds to the period during which Kcnq2p.(Thr274Met/+) mice are the most susceptible to US. C-fos labeling reveals a subset of 6 brain regions activated 2 h after the induction of the seizure. The same regions were identified in the context of seizure induction in other rodent models. ConclusionThis study provides a non-invasive and easy to use method to induce seizures in a Kcnq2-NEO-DEE mouse model and documents early neuronal activation in specific brain regions. This method can be used to test the efficacy of new antiepileptic approaches for this intractable form of genetic epilepsy.

Polymorphisms Affecting the Response to Novel Antiepileptic Drugs.

Epilepsy is one of the most frequent chronic neurologic disorders that affects nearly 1% of the population worldwide, especially in developing countries. Currently, several antiepileptic drugs (AEDs) are available for its therapy, and although the prognosis is good for most patients, 20%-30% amongst them do not reach seizure freedom. Numerous factors may explain AED-resistance such as sex, age, ethnicity, type of seizure, early epilepsy onset, suboptimal dosing, poor drug compliance, alcohol abuse, and in particular, genetic factors. Specifically, the interindividual differences in drug response can be caused by single nucleotide polymorphisms (SNPs) in genes encoding for drug efflux transporters, for the brain targets of AEDs, and for enzymes involved in drug metabolism. In this review, we used the PubMed database to retrieve studies that assessed the influence of SNPs on the pharmacokinetic (PK), pharmacodynamic (PD), and efficacy of new antiepileptic drugs. Our results showed that polymorphisms in the ABCB1, ABCC2, UGT1A4, UGT2B7, UGT2B15, CYP2C9, and CYP2C19 genes have an influence on the PK and efficacy of AEDs, suggesting that a genetic pre-evaluation of epileptic patients could help clinicians in prescribing a personalized treatment to improve the efficacy and the safety of the therapy.

Systematic Approach for Drug Repositioning of Anti-Epileptic Drugs.

Epilepsy is a central neurological disorder affecting individuals of all ages and causing unpredictable seizures. In spite of the improved efficacy of new antiepileptic drugs and novel therapy, there are still approximately 20%~30% of patients, who have either intractable or uncontrolled seizures. The epilepsy drug–target network (EDT) is constructed and successfully demonstrates the characteristics and efficacy of popularly used AEDs through the identification of causative genes for 60 epilepsy patients. We discovered that the causative genes of most intractable patients were not the targets of existing AEDs, as well as being very far from the etiological mechanisms of existing AEDs in the functional networks. We show that the existence of new drugs that target the causative genes of intractable epilepsy patients, which will be potential candidates for refractory epilepsy patients. Our systematic approach demonstrates a new possibility for drug repositioning through the combination of the drug-target and functional networks.

The 4-Aminopyridine Model of Acute Seizures in vitro Elucidates Efficacy of New Antiepileptic Drugs.

Up to date, preclinical screening for new antiepileptic substances is performed by a combination of different in vivo models of acute seizures, for which large numbers of animals are necessary. So far, little attention has been paid to in vitro models, which are also able to detect antiepileptic efficacy and in principle could likewise serve for exploratory preclinical screening. One of the established in vitro models of acute seizures is the 4-aminopyridine (4-AP) model. Previous studies have shown that the 4-AP model is capable to recapitulate the antiepileptic efficacy of standard antiepileptic drugs (AEDs) such as valproate or carbamazepine. Here, we employed a dual methodological approach using electrophysiology and optical imaging to systematically test the antiepileptic efficacy of three new-generation AEDs with distinct mechanisms of action (lacosamide, zonisamide, and levetiracetam). We found that frequency of 4-AP induced seizure like events (SLE) was the most sensitive parameter to detect dose-dependent antiepileptic effects in these compounds. Specifically, levetiracetam reduced SLE frequency while lacosamide and zonisamide at higher doses completely blocked SLE incidence. Analysis of the intrinsic optical signal additionally revealed a subiculum-specific reduction of the area involved in the propagation of ictal activity when lacosamide or zonisamide were administered. Taken together, our data adds some evidence that acute seizure models in vitro are in principle capable to detect antiepileptic effects across different mechanisms of action with efficacy similar to acute models in vivo. Further studies with negative controls, e.g., penicillin as a proconvulsant, and other clinically relevant AEDs are needed to determine if this acute in vitro model might be useful as exploratory screening tool. In view of the increasing sensitivity toward animal welfare, an affective in vitro model may help to reduce the number of laboratory animals deployed in burdening in vivo experiments and to preselect substances for subsequent testing in time- and cost-laborious models of chronic epilepsy.

Emerging trends and knowledge structure of epilepsy during pregnancy research for 2000-2018: a bibliometric analysis.

BackgroundEpilepsy during pregnancy presents a unique set of challenges for pregnant women, the fetus, and the health care community. As research in this area advances rapidly, it is critical to keep up with the emerging trends and key turning points of the development of the domain knowledge. This study aimed to construct a series of science maps to quantitatively and qualitatively evaluate the intellectual landscape and research frontiers in the field of epilepsy during pregnancy research.MethodsAll publications were extracted from the Web of Science Core Collection database. Bibliometric analysis was used to analyze the scientific research outputs, including journals, countries/regions, institutions, authors (cited authors), intellectual base and research hotspots.ResultsA total of 2,225 publications related to epilepsy during pregnancy were identified as published between 2000 and 2018. The overall trend of the number of publications showed a fluctuating growth from 59 articles in 2000 to 198 in 2018. Neurology was the leading journal in the field of epilepsy and pregnancy research both in terms of impact factor score (8.055) and H-index value (77). The US retained its leading position and exerted a pivotal influence in this area. The University of Melbourne was identified as a good research institution for research collaboration. Prof. Pennell and Tomson have made great achievements in this area, and Prof. Tomson laid a foundation for the development of this domain. The keyword “neonatal seizures” ranked first in research hotspots, and the keyword “autism spectrum disorders (ASD)” ranked first in research frontiers.ConclusionsEpilepsy during pregnancy is a fascinating and rapid development of subject matter. A more recent emerging trend focused on comprehensive management of pregnant and lactating women, evaluation of the safety and efficacy of newer antiepileptic drugs. The keywords “management issue,” “brain injury,” “meta-analysis,” “in utero exposure,” and “ASD” were the latest research frontiers and should be closely observed.

A Model of Chronic Temporal Lobe Epilepsy Presenting Constantly Rhythmic and Robust Spontaneous Seizures, Co-morbidities and Hippocampal Neuropathology.

Many animal prototypes illustrating the various attributes of human temporal lobe epilepsy (TLE) are available. These models have been invaluable for comprehending multiple epileptogenic processes, modifications in electrophysiological properties, neuronal hyperexcitability, neurodegeneration, neural plasticity, and chronic neuroinflammation in TLE. Some models have also uncovered the efficacy of new antiepileptic drugs or biologics for alleviating epileptogenesis, cognitive impairments, or spontaneous recurrent seizures (SRS). Nonetheless, the suitability of these models for testing candidate therapeutics in conditions such as chronic TLE is debatable because of a lower frequency of SRS and an inconsistent pattern of SRS activity over days, weeks or months. An ideal prototype of chronic TLE for investigating novel therapeutics would need to display a large number of SRS with a dependable frequency and severity and related co-morbidities. This study presents a new kainic acid (KA) model of chronic TLE generated through induction of status epilepticus (SE) in 6-8 weeks old male F344 rats. A rigorous characterization in the chronic epilepsy period validated that the animal prototype mimicked the most salient features of robust chronic TLE. Animals displayed a constant frequency and intensity of SRS across weeks and months in the 5th and 6th month after SE, as well as cognitive and mood impairments. Moreover, SRS frequency displayed a rhythmic pattern with 24-hour periodicity and a consistently higher number of SRS in the daylight period. Besides, the model showed many neuropathological features of chronic TLE, which include a partial loss of inhibitory interneurons, reduced neurogenesis with persistent aberrant migration of newly born neurons, chronic neuroinflammation typified by hypertrophied astrocytes and rod-shaped microglia, and a significant aberrant mossy fiber sprouting in the hippocampus. This consistent chronic seizure model is ideal for investigating the efficacy of various antiepileptic drugs and biologics as well as understanding multiple pathophysiological mechanisms underlying chronic epilepsy.

The ‘Photosensitivity Model’ is (also) a model for focal (partial) seizures

The ‘Photosensitivity Model’ uses a standardized stimulation protocol of repeated intermittent photic stimulation (IPS) over a three-day period, with administration of a single dose of an investigational antiepileptic drug (AED) after a baseline IPS day in photosensitive patients, followed by a third IPS day to determine duration of effect. This ‘Photosensitivity Model’ has shown its value in the development of new AEDs. Levetiracetam (LEV), currently a first-line AED in new-onset focal epilepsies, was not effective in classical animal models, but showed dose-dependent efficacy in the human ‘Photosensitivity Model’. Nevertheless, concerns have been expressed that AEDs selectively suppressing focal seizures might not suppress generalized photoparoxysmal EEG responses (PPR), the pharmacodynamic outcome measure in the Model. Herein, the following questions have been addressed: I. Can patients with generalized epileptiform discharges, evoked by IPS, so-called PPR, have focal epilepsy (focal seizures)? II. Are the photosensitive patients with focal epilepsy, who have participated in the photosensitivity trials, non-responsive to a new AED under investigation, as compared to those with generalized epilepsies? III. Are “focal epilepsy” AEDs effective both in the ‘Photosensitivity Model’ and in real life in photosensitive patients? We performed a systematic literature review of PPR in focal seizures and focal epilepsy and we analyzed data (published and unpublished) from 20 different potential AEDs studied prospectively in the ‘Photosensitivity Model’. Finally, the PPR effects of Na+ channel-blocking AEDs (considered as the most typical AEDs for focal epilepsy) are discussed with unequivocal examples given of the focal nature of a patient’s PPR. Based on the entire data evidence, we conclude that: 1. PPRs certainly exist in focal epilepsy (17% on average); 2. Clinical signs and symptoms of PPRs can be focal and 3. PPRs can definitely be used to identify or to prove efficacy of new AEDs for patients with focal epilepsy.

Optical triggered seizures using a caged 4-Aminopyridine.

Animal models of epilepsy are critical not only for understanding the fundamental mechanism of epilepsy but also for testing the efficacy of new antiepileptic drugs and novel therapeutic interventions. Photorelease of caged molecules is widely used in biological research to control pharmacologic events with high spatio-temporal resolution. We developed a technique for in vivo optical triggering of neocortical seizures using a novel caged compound based on ruthenium photochemistry (RuBi-4AP). Epileptiform events in mouse cortex were induced with blue light in both whole brain and focal illumination. Multi-electrode array recording and optical techniques were used to characterize the propagation of these epileptic events, including interictal spikes, polyspikes, and ictal discharges. These results demonstrate a novel optically-triggered seizure model, with high spatio-temporal control, that could have widespread application in the investigation of ictal onset, propagation and to develop novel light-based therapeutic interventions.

Old versus New: Why Do We Need New Antiepileptic Drugs?

Achieving complete seizure remission without adverse events is the goal of epilepsy treatment. Recently, many new antiepileptic drugs (AEDs) have been developed. Even though the efficacy of new AEDs is not stronger than that of old AEDs, there are advantages in using new AEDs. They have unique or different mechanisms of action that enable the creation of possible synergistic combinations. They usually exhibit fewer or no pharmacokinetic drug interactions. Furthermore, the response to AEDs varies individually. A similar efficacy does not imply a similar response from all patients. Many new AEDs have fewer adverse events, including induction of congenital malformations. Other concerns about the long-term effects of established AEDs, such as bone health and development of atherosclerosis, may be alleviated by the use of new AEDs. New AEDs are needed to achieve better care of patients with epilepsy.

Therapy for hyperthermia-induced seizures in Scn1a mutant rats

Mutations in the SCN1A gene, which encodes the α1 subunit of voltage-gated sodium channels, cause generalized epilepsy with febrile seizures plus (GEFS+) and severe myoclonic epilepsy of infancy (SMEI). N1417H-Scn1a mutant rats are considered to be an animal model of human FS+ or GEFS+. To assess the pharmacologic validity of this model, we compared the efficacies of eight different antiepileptic drugs (AEDs) for the treatment of hyperthermia-induced seizures using N1417H-Scn1a mutant rats. AEDs used in this study included valproate, carbamazepine (CBZ), phenobarbital, gabapentin, acetazolamide, diazepam (DZP), topiramate, and potassium bromide (KBr). The effects of these AEDs were evaluated using the hot water model, which is a model of experimental FS. Five-week-old rats were pretreated with each AED and immersed in water at 45°C to induce hyperthermia-induced seizures. The seizure manifestations and video-electroencephalographic recordings were evaluated. Furthermore, the effects of each AED on motor coordination and balance were assessed using the balance-beam test. KBr significantly reduced seizure durations, and its anticonvulsant effects were comparable to those of DZP. On the other hand, CBZ decreased the seizure threshold. In addition, DZP and not KBr showed significant impairment in motor coordination and balance. DZP and KBr showed potent inhibitory effects against hyperthermia-induced seizures in the Scn1a mutant rats, whereas CBZ exhibited adverse effects. These responses to hyperthermia-induced seizures were similar to those in patients with GEFS+ and SMEI. N1417H-Scn1a mutant rats may, therefore, be useful for testing the efficacy of new AEDs against FS in GEFS+ and SMEI patients.

Efficacy of New Antiepileptic Drugs

Regarding efficacy of new antiepileptic drugs (AEDs) for seizure control, there are three important clinical questions. How effective are new AEDs when corrected for the efficacy of placebo? And even more important: How do new AEDs fare in terms of seizure remission compared with established agents? And finally: Have patients seizure-free on new AEDs a better chance for lasting remission after withdrawal versus those withdrawing from older agents? The answers raise concerns. Although add-on therapy with marketed new AEDs is more effective than placebo, as expected, the treatment difference for becoming seizure-free is disappointingly small (6%; 95% CI: 4-8%; z = 6.47; p < 0.001). Although many, but not all, new AEDs have comparable efficacy to old standard drugs in well-controlled trials, none of the new AEDs is superior to old drugs in terms of seizure remission. So far, we have no antiepileptogenic treatments that prevent the development of epilepsy or modify its detrimental course. The sobering results suggest the need for novel experimental and clinical strategies for the development of more effective new AEDs that interrupt ictogenesis more effectively and prevent or abort epileptogenesis. Ideally, we need new drugs that block both ictogenesis and epileptogenesis, resulting in complete cure of epilepsy.

When clinical trials make history: Demonstrating efficacy of new antiepileptic drugs as monotherapy

Regulatory requirements to demonstrate the efficacy of novel antiepileptic drugs (AEDs) as monotherapy differ between Europe and the United States. European regulators require a comparison with an established, optimally dosed AED, typically using a noninferiority design, whereas the U.S. Food and Drug Administration (FDA) demands demonstration of superiority versus a comparator. Because placebo cannot be used as sole therapy and it is unrealistic to expect that a new AED will be more efficacious than established agents at full dosages, superiority monotherapy trials in epilepsy have traditionally relied on inclusion of controls treated with a suboptimal (low-dose) comparator. In the most common design, refractory patients are randomized to conversion to monotherapy with a full dose of the investigational agent or a low-dose active control, and are required to exit the trial if seizures deteriorate. Efficacy is demonstrated when exit rates are lower in the full-dose group than in controls. Although this design is efficient in demonstrating superiority, the use of suboptimal treatments has been increasingly criticized on ethical grounds. A meta-analysis has now demonstrated that patients randomized to suboptimal treatments in all previous trials had similar outcomes, thereby allowing the build up of a dataset of historical controls against which response to investigational AEDs can be compared in future trials. Use of historical controls has been accepted by the FDA, subject to compliance with rigorous methodologic requirements. Although the avoidance of suboptimal treatments in future trials is a welcome development, the conversion-to-monotherapy design is still far from being fully satisfactory and is not exempt from methodologic concerns.

Epilepsy surgery, antiepileptic drug trials, and the role of evidence

We assessed whether recent randomized controlled trials (RCTs) of antiepileptic drugs (AEDs) are informed by evidence about surgical effectiveness. We explored whether RCTs of AEDs consider the patients' candidacy for surgery in their eligibility criteria, and whether the necessary investigations are requested in participating patients to determine their potential eligibility for surgery. We systematically analyzed RCTs published in the last 2 years investigating the efficacy of new AEDs in localization-related epilepsy. Results from a surgical RCT and recommendations from an epilepsy surgery practice parameter were used to assess the degree to which surgical evidence informed the drug study design. Eleven RCTs were analyzed. All were conducted in countries with access to epilepsy surgery. None of the studies required magnetic resonance imaging (MRI) with an epilepsy protocol or explicit statement of the epilepsy syndrome, which could lead to the identification of surgical candidates. Having temporal lobe epilepsy or being a potential surgical candidate were not exclusion criteria in any of the trials. The primary efficacy end point was the reduction in seizure frequency or responder rate. Seizure freedom was never the primary outcome, and it was reported in only seven studies. The pooled data analysis of these trials revealed that 1.9% of patients became seizure-free on placebo and 4.4% on the study drug (p < 0.01). Important aspects of patient selection for new AED trials are not informed by the evidence about surgical effectiveness. Investigations that could lead to identification of patients for presurgical evaluation were not required in any of the studies.

Monotherapy clinical trial design

Monotherapy of epilepsy is usually preferable to polytherapy for a variety of reasons. However, investigational or newer antiepileptic drugs (AEDs) are typically evaluated as add-on therapy in patients with refractory seizures. Because coadministered drugs are subject to drug interactions, add-on trials of AEDs do not necessarily address the utility of a new AED as monotherapy or its use in patients with newly diagnosed epilepsy, in whom monotherapy is usually sufficient. Monotherapy clinical trials are difficult to design because randomizing epilepsy patients to placebo or pseudoplacebo is considered unethical, and results from active-drug noninferiority designs are difficult to interpret. Active-drug superiority designs have been developed in an attempt to provide useful information about the monotherapeutic efficacy of new AEDs. The conversion to monotherapy trial design, introduced in the late 1970s, provides for initial add-on of an investigational agent to a preexisting drug in patients with uncontrolled seizures, followed by gradual discontinuation of the preexisting treatment and an eventual monotherapy phase of the investigational agent. Conversion to monotherapy trials are typically of short duration and have been criticized for failing to provide adequate time for titration to optimal dose, an inability to examine tolerance development or long-term safety, and possibly placing enrolled patients at increased risk for morbidity, but they have been used to obtain data about monotherapy efficacy sufficient for regulatory authority approval. Relevant clinical trial data are needed to guide treatment choices in patients who have failed previous monotherapy. To date, large-scale prospective trials comparing monotherapy with old and new AEDs have not shown superior efficacy of the new AEDs but have demonstrated their better tolerability and safety. It is hoped that use of appropriately designed monotherapy clinical trials will help to identify a new generation of AEDs in the future for monotherapy in epilepsy patients.

Canine epilepsy: What can we learn from human seizure disorders?

Epilepsy is a common neurological disorder in both dogs and humans. It is refractory to therapy in approximately one-third of canine patients, and even with the advent of new antiepileptic drugs for humans, appropriate treatment options in dogs remain limited. The pathogenesis and pathophysiology of epilepsy is being studied extensively in both human patients and rodent models of experimental epilepsy at the cellular and molecular level, but very little is known about the aetiologies of epilepsies in dogs. In this review, canine epilepsy will be discussed with reference to the human epilepsies and experimental epilepsy research. There is much work to be done in order to classify canine seizure types and breed-specific epileptic syndromes, particularly with reference to electroencephalographic abnormalities and possible genetic abnormalities. The review considers the appropriate use of antiepileptic drugs: phenobarbitone and potassium bromide are effective in most canine patients, although dosing regimes need to be carefully tailored to the individual, with serum concentration measurement. However, a significant proportion of patients remains refractory to these drugs. Work is currently underway to test the efficacy of newer antiepileptic drugs in the treatment of canine epilepsy, and preliminary data suggest that human drugs such as levetiracetam and gabapentin are of benefit in dogs with refractory epilepsy.

Anticonvulsant drug or neuromodulator? The growing case for anticonvulsant uses beyond epilepsy.

Epilepsy drugs were often used for other disorders before their effectiveness in epilepsy was fully appreciated, and the efficacy of newer antiepileptic drugs for conditions other than epilepsy is now being studied.

Measuring the efficacy of antiepileptic drugs

Clinical trials of new antiepileptic drugs (AEDs) include regulatory studies aimed at demonstrating efficacy and reasonable safety, post-marketing open-open label studies and longer term outcome studies. Regulatory trials involve a carefully selected population of patients and are conducted under rigorously standardised conditions. Data from such studies cannot often be translated into clinical practice. Pragmatic post-marketing studies using flexible dosing schedules allow clinicians to better judge the utility of the new drug in a wider population of patients with epilepsy and decide the most appropriate dosing schedules. This paper discusses some of the issues surrounding the measurement of efficacy of new AEDs in both pre- and post-marketing phases of their development. All of the newer AEDs are initially used in patients with refractory partial seizures as adjunctive treatment. These trials are generally parallel-group studies although cross-over designs have been employed. The use of placebo-control is uncontroversial in this type of study. Efficacy endpoints are generally manipulations of seizure frequency on study drug compared to control. Global outcome measures and health related quality of life scores can also be used to measure efficacy. As the standard AEDs are associated with a high rate of seizure remission in patients who receive them as monotherapy, demonstration of superior efficacy of a new agent in a comparative trial will require large numbers of patients in a design that takes into account the natural history of treated epilepsy. Comparing investigational agents to a standard AED in an ‘active-control’ study with demonstration of equivalent efficacy would seem to be an acceptable way of assessing efficacy of new AEDs in this population. Some regulators, however, do not accept equivalence as proof of efficacy and insist on demonstration of superiority compared to a control. The use of placebo alone in the control group is ethically dubious. Several innovative study designs have, therefore, been used to satisfy regulatory requirements, while maintaining patient safety including withdrawal to monotherapy using high versus low dose comparators. Observational outcome studies provide the best opportunity of exploring the long-term utility of individual AEDs. Such studies largely follow standard clinical practice and need considerable time and resources. They can, however, yield valuable information about the effectiveness of AEDs in everyday clinical practice. Data from regulatory trials should be complemented by postmarketing studies and longer term studies of outcome to help clinicians decide the best way of utilising new AEDs and establishing their role in the therapeutic armamentarium.

Clinical efficacy of new antiepileptic drugs in refractory partial epilepsy: experience in the United States with three novel drugs.

A number of new antiepileptic drugs (AEDs), including topiramate (TPM), felbamate (FBM), and gabapentin (GBP), are approved or believed to be close to approval for marketing in the United States. Key efficacy findings for these AEDs in refractory partial epilepsy were reviewed. Large and significant drug-placebo differences were observed with TPM in two large dose-finding trials conducted in the United States. The minimal effective dose of TPM in the population studied was determined to be approximately 200 mg/day, and doses above 600 mg/day produced good efficacy but little incremental benefit versus the lower dosages for the overall study population. FBM is active in partial epilepsy, although seizure reduction is less marked and drug interactions complicate the findings. GBP is also active in this population, but only the 1,800 mg/day dosage was significantly better than placebo with respect to percent responders. It may be useful to explore higher dosage ranges for both FBM and GBP if they can be well tolerated.

Methodological requirements for clinical trials in refractory epilepsies — our experience with zonisamide

1. The guidelines for clinical evaluation of antiepileptic drugs (AEDs), proposed by the International League Against Epilepsy in 1989, were scrutinized through our clinical experiences with zonisamide. 2. Seizure type, seizure frequency, number of concomitant AEDs, and type of epilepsy were found to be essential factors in quantitatively determining the efficacy of a new drug. 3. The majority of patients selected according to the guidelines consist inevitably of those with complex partial seizures with or without secondary generalization. Consequently, the efficacy of new AEDs is evaluated mainly in patients with partial seizures, and it is difficult to evaluate their efficacy in those with refractory generalized seizures, either convulsive or nonconvulsive. 4. In order to avoid such predilection, patients with various types of generalized seizures who are taking one or two conventional AEDs should account for 30 to 40 % of the total patient population selected for clinical drug trials.