Aggravation of epilepsy by antiepileptic drugs

Approach to Patients with Seizures and Epilepsy: A Guide for Primary Care Physicians

Seizures and epilepsy are common neurologic conditions that are frequently encountered in the outpatient primary care setting. An accurate diagnosis relies on a thorough clinical history and evaluation. Understanding seizure semiology and classification is crucial in conducting the initial assessment. Knowledge of common seizure triggers and provoking factors can further guide diagnostic testing and initial management. The pharmacodynamic characteristics and side effect profiles of anti-seizure medications are important considerations when deciding treatment and counseling patients, particularly those with comorbidities and in special populations such as patient of childbearing potential.

Pharmacodynamic rationale for the choice of antiseizure medications in the paediatric population

In the landscape of paediatric epilepsy treatment, over 20 anti-seizure medications (ASMs) have gained approval from Drug Regulatory Agencies, each delineating clear indications. However, the complexity of managing drug-resistant epilepsy often necessitates the concurrent use of multiple medications. This therapeutic challenge highlights a notable gap: the absence of standardized guidelines, compelling clinicians to rely on empirical clinical experience when selecting combination therapies. This comprehensive review aims to explore current evidence elucidating the preferential utilization of specific ASMs or their combinations, with a primary emphasis on pharmacodynamic considerations. The fundamental objective underlying rational polytherapy is the strategic combination of medications, harnessing diverse mechanisms of action to optimize efficacy while mitigating shared side effects. Moreover, the intricate interplay between epilepsy and comorbidities partly may influence the treatment selection process. Despite advancements, unresolved queries persist, notably concerning the mechanisms underpinning drug resistance and the paradoxical exacerbation of seizures. By synthesizing existing evidence and addressing pertinent unresolved issues, this review aims to contribute to the evolving landscape of paediatric epilepsy treatment strategies, paving the way for more informed and efficacious therapeutic interventions.

Transient targeting of hypothalamic orexin neurons alleviates seizures in a mouse model of epilepsy

Lateral hypothalamic (LH) hypocretin/orexin neurons (HONs) control brain-wide electrical excitation. Abnormally high excitation produces epileptic seizures, which affect millions of people and need better treatments. HON population activity spikes from minute to minute, but the role of this in seizures is unknown. Here, we describe correlative and causal links between HON activity spikes and seizures. Applying temporally-targeted HON recordings and optogenetic silencing to a male mouse model of acute epilepsy, we found that pre-seizure HON activity predicts and controls the electrophysiology and behavioral pathology of subsequent seizures. No such links were detected for HON activity during seizures. Having thus defined the time window where HONs influence seizures, we targeted it with LH deep brain stimulation (DBS), which inhibited HON population activity, and produced seizure protection. Collectively, these results uncover a feature of brain activity linked to seizures, and demonstrate a proof-of-concept treatment that controls this feature and alleviates epilepsy.

Paradoxical effects of levetiracetam in people with epilepsy with rhythmic epileptiform discharges

OBJECTIVE

To elucidate the incidence and risk factors for paradoxical effects (i.e., increased seizure frequency, increased seizure severity, or onset of new seizure types) of levetiracetam (LEV) in people with epilepsy (PWE) and identify the usefulness of electroencephalography (EEG) in predicting these effects.

METHODS

We examined data for consecutive PWE treated with LEV. All PWE underwent EEG and magnetic resonance imaging (MRI) before LEV administration. We also evaluated the incidence of paradoxical LEV effects and conducted multivariate logistic regression analyses to identify the associated factors.

RESULTS

In total, 210 (66.2%) of 317 PWEs treated in our department had a history of LEV use. The incidence of paradoxical LEV effects was 5.2% (n = 11) and was significantly associated with a high LEV dose (p = 0.029), high seizure frequency (p = 0.005), temporal lobe epilepsy (p = 0.004), focal awareness seizure (p = 0.004), focal impaired awareness seizure (p = 0.007), spike (p = 0.015), rhythmic epileptiform discharges (REDs; p = 0.003), and MRI-identified focal cortical dysplasia (FCD; p < 0.0001). Multivariate analyses revealed that REDs (odds ratio [OR] = 5.35, p = 0.048, 95% confidence interval [CI]: 1.01-28.21) were independently associated with paradoxical LEV effects.

CONCLUSIONS

Paradoxical LEV effects occurred in PWE, particularly in those with drug-resistant focal epilepsy. Furthermore, the occurrence of REDs in EEG was an independent factor associated with the paradoxical effects of LEV in PWE.

Seizure exacerbation with anti-seizure medications in adult patients with epilepsy

There are numerous reports of seizure exacerbation related to specific anti-seizure medications (ASMs); however, a quantitative analysis with clearly defined parameters for seizure exacerbation in an outpatient setting is lacking. This retrospective study examines adult patients starting a single ASM and follows patient outcomes over the course of treatment, with quantitative evaluation of the incidence of paradoxical seizure exacerbation. In this study, outpatient encounters with five epileptologists at the Baylor College of Medicine Comprehensive Epilepsy Center were evaluated over a 10-month period. Seizure exacerbation was defined as an increase in seizure frequency at least 2 times greater than the baseline seizure frequency after initiation of an ASM, with return to baseline after ASM discontinuation. Patients were stratified into four categories: (1) probable ASM-induced seizure exacerbation; (2) possible ASM-induced seizure exacerbation; (3) non-ASM induced seizure exacerbation; or (4) no seizure exacerbation. Out of a total of 236 encounters where an ASM was initiated, we found that 5.5% of patients experienced some form of seizure exacerbation. However, only 1.3% of patients had probable ASM-induced seizure exacerbation. Consistent with prior studies, our data indicate seizure exacerbation in adults is rare with the initiation of ASMs. However, further studies with a larger sample size are necessary to better understand what factors may predispose patients to potential medication-induced seizure exacerbation.

[Paradoxical effect of levetiracetam on seizure suppression: three cases showing U curve association between dose and effect]

We experienced 3 adult patients with intractable focal epilepsy treated by levetiracetam (LEV) as polytherapy, who showed paradoxical effect (PE). Starting dose of LEV was small (62.5, 250 mg/day) and we gradually increased by less than 250 mg/day, every more than 2 weeks. Within 6 months after LEV was added, LEV of 750 to 1,000 mg/day brought reduction of seizure frequency. Serum concentration of LEV was 13.3 and 14.0 μg/ml. In order to obtain better seizure control, LEV was increased up to 1,000-2,500 mg/day (19.3-35.0 μg/ml) within one year, and they developed PE. They all showed increased habitual seizures, occurring in cluster. Once dose of LEV deceased down to what produced the maximum seizure suppression, all of the patients regained the better seizure control. It is most likely that at least in some patients like present 3 cases, PE of LEV may express U curve association between dose and effect and that it was only delineated by slow titration.

Medical Management in Focal versus Generalized Epilepsy

About 70% of children with new-onset epilepsy have the potential to become seizure-free on antiepileptic drug (AED) monotherapy with appropriately selected first-line medication. In ideal world, physician is expected to achieve best possible seizure control without impacting the quality of life. There is rapid increase in number of AEDs available over last couple of decades. Although not necessarily all of them are superior to old generation drugs in terms of seizure control, certainly there is change in landscape from perspective of tolerability and side-effect profile. Physicians must therefore be familiar with safety, tolerability, therapeutic effects, synergistic combinations as well as AEDs to avoid in specific circumstances. The article attempts to give general overview of available AEDs under broad umbrella of effectiveness against focal and generalized seizures as well as drugs with “broad spectrum.” The emergence of newer AEDs with broad spectrum and favorable side-effect profile is welcome. However, the future lies in better understanding of underlying diverse pathophysiology of clinical symptom “epilepsy” and developing new compounds acting on molecular targets as well as individualizing therapy. Technological advances in molecular genetics research are bringing precision medicine to the fore.

Risk factors of paradoxical reactions to anti-seizure medication in genetic generalized epilepsy

This study aimed at providing valid estimates for the risk of clinically relevant seizure aggravation by recommended anti-seizure medications in patients with Genetic Generalized Epilepsy (GGE). To this aim, treatment response, side effects and paradoxical reactions to anti-seizure treatment were retrospectively assessed in a near-population based cohort comprising 471 adult GGE patients. A total of 1046 treatment attempts were analyzed (lamotrigine: 351, valproic acid: 295, levetiracetam: 249, primidone/phenobarbital: 94, zonisamide: 57). Under lamotrigine, seizure aggravation was observed in 15 patients (two patients during levetiracetam, one patient during zonisamide, none during phenobarbital and valproic acid). All but two patients with paradoxical reactions to lamotrigine were diagnosed with juvenile myoclonic epilepsy (JME), otherwise, the clinical and electroencephalographic characteristics of patients with paradoxical reactions did not differ. At treatment start, the estimated risk of a paradoxical reaction to lamotrigine was 7.9 % in JME patients (n = 190). For all GGE patients (incl. JME), the estimated risk of clinically relevant seizure aggravation under treatment with lamotrigine was 3.7 % (1.8 % for zonisamide and 0.8 % for levetiracetam). In conclusion, clinical significant aggravation of seizure frequency is common in lamotrigine-treated JME patients but rare in patients with other GGE subsyndromes or under treatment with other recommended anti-seizure medication.

The Pharmacology and Clinical Efficacy of Antiseizure Medications: From Bromide Salts to Cenobamate and Beyond

Epilepsy is one of the most common and disabling chronic neurological disorders. Antiseizure medications (ASMs), previously referred to as anticonvulsant or antiepileptic drugs, are the mainstay of symptomatic epilepsy treatment. Epilepsy is a multifaceted complex disease and so is its treatment. Currently, about 30 ASMs are available for epilepsy therapy. Furthermore, several ASMs are approved therapies in nonepileptic conditions, including neuropathic pain, migraine, bipolar disorder, and generalized anxiety disorder. Because of this wide spectrum of therapeutic activity, ASMs are among the most often prescribed centrally active agents. Most ASMs act by modulation of voltage-gated ion channels; by enhancement of gamma aminobutyric acid-mediated inhibition; through interactions with elements of the synaptic release machinery; by blockade of ionotropic glutamate receptors; or by combinations of these mechanisms. Because of differences in their mechanisms of action, most ASMs do not suppress all types of seizures, so appropriate treatment choices are important. The goal of epilepsy therapy is the complete elimination of seizures; however, this is not achievable in about one-third of patients. Both in vivo and in vitro models of seizures and epilepsy are used to discover ASMs that are more effective in patients with continued drug-resistant seizures. Furthermore, therapies that are specific to epilepsy etiology are being developed. Currently, ~ 30 new compounds with diverse antiseizure mechanisms are in the preclinical or clinical drug development pipeline. Moreover, therapies with potential antiepileptogenic or disease-modifying effects are in preclinical and clinical development. Overall, the world of epilepsy therapy development is changing and evolving in many exciting and important ways. However, while new epilepsy therapies are developed, knowledge of the pharmacokinetics, antiseizure efficacy and spectrum, and adverse effect profiles of currently used ASMs is an essential component of treating epilepsy successfully and maintaining a high quality of life for every patient, particularly those receiving polypharmacy for drug-resistant seizures.

Alternatives to valproate in girls and women of childbearing potential with Idiopathic Generalized Epilepsies: state of the art and guidance for the clinician proposed by the Epilepsy and Gender Commission of the Italian League Against Epilepsy (LICE)

Following recent European Medication Agency restrictions on valproate (VPA) use in girls and women of childbearing potential (WOCP), the Commission on Epilepsy and Gender of the Italian League against Epilepsy integrated current literature and legislative data in order to provide clinicians with guidance on antiseizure medication (ASM) prescription for Idiopathic Generalized Epilepsies (IGEs) in this population, avoiding VPA. We reviewed the updated literature on ASMs and examined the teratogenicity of those showing efficacy in IGEs. For all relevant ASMs, we considered the indications for use and the pregnancy and contraception-related recommendations given in the Italian Summary of Product Characteristics (SmPC) and on the websites of the European Medicines Agency (EMA) and other European Union (EU) countries' regulatory agencies. With the exception of absence seizures, the literature lacks high quality studies on ASMs in IGEs. In girls and WOCP, levetiracetam and lamotrigine should be considered the first-choice drugs in Generalized Tonic-Clonic Seizures Alone and in Juvenile Myoclonic Epilepsy, lamotrigine in Juvenile Absence Epilepsy, and ethosuximide in Childhood Absence Epilepsy. Although supported by the literature, several ASMs are off label, contraindicated or burdened by special warnings in pregnancy. Some discrepancies emerged between the various SmPC warnings for different brands of the same active principle. We provided a therapeutic algorithm for each IGE syndrome and highlighted the need for revised prescription rules, consistent with the latest literature data, uniformity of SmPC warnings for the same active principle, and more data on the efficacy of new ASMs in IGEs and their safety in pregnancy.

Pharmacological Management of the Genetic Generalised Epilepsies in Adolescents and Adults

Common genetic generalised epilepsy syndromes encountered by clinicians include childhood and juvenile absence epilepsies, juvenile myoclonic epilepsy and generalised tonic-clonic seizures on awakening. Treatment of these syndromes involves largely the use of broad-spectrum antiseizure drugs. Those effective for the generalised epilepsies include sodium valproate, phenobarbital, ethosuximide, clobazam, clonazepam, lamotrigine, levetiracetam, topiramate, zonisamide and, more recently, perampanel and brivaracetam. Results from the few rigorous studies comparing outcomes with drugs for genetic generalised epilepsies show valproate to be the most effective. The majority of patients with genetic generalised epilepsy syndromes will become seizure free on antiseizure monotherapy; those for whom control proves elusive may benefit from combination regimens. Early counselling regarding management may assist the patient to come to terms with their diagnosis and improve long-term outcomes. Treatment can be lifelong in some individuals, although others may remain seizure free without medication. Choice of antiseizure medication depends on the efficacy for specific seizure types, as well as tolerability. For patients prescribed comedication, drug interactions should be considered. In particular, for young women taking oral hormonal contraceptives, ≥ 200 mg/day of topiramate can decrease the circulating concentration of ethinylestradiol and ≥ 12 mg/day of perampanel can induce levonorgestrel metabolism. The use of valproate in women of childbearing potential is limited by associated teratogenic and neurodevelopmental effects in offspring. Given that valproate is often the antiseizure drug of choice for genetic generalised epilepsies, this creates a dilemma for patients and clinicians. Decision making can be aided by comprehensive assessment and discussion of treatment options. Psychiatric comorbidities are common in adolescents and adults with genetic generalised epilepsies. These worsen the prognosis, both in terms of seizure control and quality of life. Attendant lifestyle issues can impact significantly on the individual and society. Frontal lobe dysfunction, which can present in patients with juvenile myoclonic epilepsy, can adversely affect the long-term outlook, regardless of the nature of seizure control. Ongoing management requires consideration of psychosocial and behavioural factors that can complicate diagnosis and treatment. An assured supportive attitude by the neurologist can be an important contributor to a positive outcome. The mechanisms underlying genetic generalised epilepsies, including genetic abnormalities, are unclear at present. As the pathophysiology is unravelled, this may lead to the development of novel therapies and improved outcomes for patients with these syndromes.

A retrospective observational study of EEG findings and antiepileptic drug use among children referred for EEG to Zambia's University Teaching Hospital

Objective

Despite the heavy burden of epilepsy in Sub‐Saharan Africa, there remains a relative paucity of neurophysiology services and limited published data on electroencephalography (EEG) features among African children. The aim of this study was to describe clinical characteristics, EEG findings, and antiepileptic drug (AED) use among children referred for EEG to the University Teaching Hospital in Zambia.

Methods

EEG referrals and reports from 2013–2015 were reviewed. Within the context of routine care, EEG studies were interpreted by readers with advanced training in child neurology and clinical neurophysiology. Clinical data provided in the referral including seizure semiology and EEG findings were systematically extracted and analyzed.

Results

A total of 1,217 EEG reports were reviewed, with 1,187 included in the analysis. Median age was 7 years (interquartile range [IQR] 3–11) and 57% were male. Seventy‐three percent of 554 had documented seizure onset before 5 years of age. Among the 23% with seizure etiology documented, 78% were associated with perinatal injuries and central nervous system (CNS) infections. EEG abnormalities were found in 75% of the studies. Clinical semiology per referral identified focal seizures in 29%, but EEG findings increased this proportion to 63% (p = 0.004). Sixty‐two percent were taking AEDs, with 85% on monotherapy. The most commonly used AED was carbamazepine (49%).There was no association between the choice of AED and clinical semiology (all p's > 0.05).

Significance

This tertiary care center study identified >60% of referred children to have localization‐related epilepsies, with at least 18% of epilepsies being from potentially preventable causes. These findings are consistent with multi‐country, population‐based data from elsewhere in Africa. Seizure semiology assessed in routine, nonspecialist care does not predict AED choice, and the presence of focality is underestimated in routine care.

Methylated flavonoids as anti-seizure agents: Naringenin 4',7-dimethyl ether attenuates epileptic seizures in zebrafish and mouse models

Epilepsy is a neurological disease that affects more than 70 million people worldwide and is characterized by the presence of spontaneous unprovoked recurrent seizures. Existing anti-seizure drugs (ASDs) have side effects and fail to control seizures in 30% of patients due to drug resistance. Hence, safer and more efficacious drugs are sorely needed. Flavonoids are polyphenolic structures naturally present in most plants and consumed daily with no adverse effects reported. These structures have shown activity in several seizure and epilepsy animal models through allosteric modulation of GABA_A receptors, but also via potent anti-inflammatory action in the brain. As such, dietary flavonoids offer an interesting source for ASD and anti-epileptogenic drug (AED) discovery, but their pharmaceutical potential is often hampered by metabolic instability and low oral bioavailability. It has been argued that their drug-likeness can be improved via methylation of the free hydroxyl groups, thereby dramatically enhancing metabolic stability and membrane transport, facilitating absorption and highly increasing bioavailability. Since no scientific data is available regarding the use of methylated flavonoids in the fight against epilepsy, we studied naringenin (NRG), kaempferol (KFL), and three methylated derivatives, i.e., naringenin 7-O-methyl ether (NRG-M), naringenin 4',7-dimethyl ether (NRG-DM), and kaempferide (4'-O-methyl kaempferol) (KFD) in the zebrafish pentylenetetrazole (PTZ) seizure model. We demonstrate that the methylated flavanones NRG-DM and NRG-M are highly effective against PTZ-induced seizures in larval zebrafish, whereas NRG and the flavonols KFL and KFD possess only a limited activity. Moreover, we show that NRG-DM is active in two standard acute mouse seizure models, i.e., the timed i.v. PTZ seizure model and the 6-Hz psychomotor seizure model. Based on these results, NRG-DM is proposed as a lead compound that is worth further investigation for the treatment of generalized seizures and drug-resistant focal seizures. Our data therefore highlights the potential of methylated flavonoids in the search for new and improved ASDs.

A pediatric epilepsy diagnostic tool for use in resource-limited settings: A pilot study

OBJECTIVE

It is estimated that nearly 80% of the 50 million people affected with epilepsy globally live in regions where specialist care and diagnostic tests are scarce and care is often delivered through a primary health provider with limited training. To improve diagnostic accuracy of the history and physical examination, we developed and piloted a questionnaire to discriminate between focal versus generalized epilepsy, with the future goal to guide medication choices.

METHODS

Through literature review and retrospective chart review of 75 children with epilepsy at Boston Children's Hospital, a 15-item questionnaire was developed. Simple motor seizures were excluded for the purposes of this questionnaire. The questionnaire was then translated in local dialects and prospectively validated at Muhimbili National Hospital in Dar Es Salaam, Tanzania, and University Teaching Hospital in Lusaka, Zambia. Children 6months-18years of age with suspected or active epilepsy were identified, and a nonphysician administered the questionnaire to the patient's caregiver. Next, each patient was evaluated by a pediatric neurologist blinded to the questionnaire results, and together with locally obtained but remotely interpreted EEG, an electroclinical diagnosis was made. The questionnaire data were compared with this clinical gold standard.

RESULTS

A total of 59 children participated: 28 from Tanzania and 31 from Zambia. Sixteen patients were excluded: 5 were excluded because of incomplete data, and 11 did not meet criteria for epilepsy based on initial screening questions. Of the remaining 43 patients, 28 had focal or multifocal epilepsy (65%), and 15 (35%) had generalized epilepsy. The questionnaire had a sensitivity of 78% and positive predictive value of 81.5%. Data were analyzed using a Rasch model, testing the questionnaire's internal consistency, reliability, and its discriminative validity in classifying focal versus generalized epilepsy against an electroclinical diagnosis. The mean epilepsy score for focal epilepsy was 0.084 logits compared with -1.147 logits for generalized epilepsy, demonstrating a large effect size [F (1, 41)=13.490, p<0.001].

CONCLUSIONS

Our questionnaire provides a straightforward method to improve diagnostic accuracy, and could assist in bridging the diagnostic gap in pediatric epilepsy in resource-limited settings. This tool was specifically designed to be easily implemented by any healthcare provider. This pilot study prompts broader prospective validation in additional settings for further refinement, and for performance assessment of impact on provider's practice, ability to guide medication choices, and ultimately improve treatment outcomes in resource-limited regions.

Drug-resistant epilepsy: definition and treatment alternatives

INTRODUCTION

Drug-resistant epilepsy affects 25% of all epileptic patients, and quality of life decreases in these patients due to their seizures. Early detection is crucial in order to establish potential treatment alternatives and determine if the patient is a surgical candidate.

DEVELOPMENT

PubMed search for articles, recommendations published by major medical societies, and clinical practice guidelines for drug-resistant epilepsy and its medical and surgical treatment options. Evidence and recommendations are classified according to the criteria of the Oxford Centre for Evidence-Based Medicine (2001) and the European Federation of Neurological Societies (2004) for therapeutic actions.

CONCLUSIONS

Identifying patients with drug-resistant epilepsy is important for optimising drug therapy. Experts recommend rational polytherapy with antiepileptic drugs to find more effective combinations with fewer adverse effects. When adequate seizure control is not achieved, a presurgical evaluation in an epilepsy referral centre is recommended. These evaluations explore how to resect the epileptogenic zone without causing functional deficits in cases in which this is feasible. If resective surgery is not achievable, palliative surgery or neurostimulation systems (including vagus nerve, trigeminal nerve, or deep brain stimulation) may be an option. Other treatment alternatives such as ketogenic diet may also be considered in selected patients.

Initiating antiepileptic drug treatment and characteristics of drugs

This chapter covers the main steps involved in the initiation of antiepileptic drug therapy. Aspects covered specifically include the decision whether or not to initiate treatment, the selection process of a drug of first choice for a given patient with a particular seizure type or epilepsy syndrome, and the process of initiating therapy with the selected drug of first choice. Suggested choices of antiepileptic drugs by seizure type or epilepsy syndrome are summarized in a table. In an appendix, these drugs are reviewed individually with regard to their clinical use. The emphasis is on initial dose, dosage escalation, common and serious adverse effects, baseline evaluation, monitoring of therapy, and relevant drug interactions.

Current advances in childhood absence epilepsy

BACKGROUND

Childhood absence epilepsy is an age-dependent, idiopathic, generalized epilepsy with a characteristic seizure appearance. The disorder is likely to be multifactorial, resulting from interactions between genetic and acquired factors, but the debate is still open. We review recent studies on different aspects of childhood absence epilepsy and also to describe new concepts.

METHODS

Data for this review were identified using Medline and PubMed survey to locate studies dealing with childhood absence epilepsy. Searches included articles published between 1924 and 2013.

RESULTS

The diagnosis comprises predominant and associated seizure types associated with other clinical and electroencephalographic characteristics. Many studies have challenged the prevailing concepts, particularly with respect to the pathophysiological mechanisms underlying the electroencephalographic seizure discharges. Childhood absence epilepsy fits the definition of system epilepsy as a condition resulting from the persisting susceptibility of the thalamocortical system as a whole to generate seizures. This syndrome, if properly defined using strict diagnostic criteria, has a good prognosis. In some cases, it may affect multiple cognitive functions determining risk for academic and functional difficulties; the detection of children at risk allows tailored interventions. Childhood absence epilepsy is usually treated with ethosuximide, valproate, lamotrigine, or levetiracetam, but the most efficacious and tolerable initial empirical treatment has not been well defined.

CONCLUSIONS

We review recent studies and new concepts on the electroclinical features and pathophysiological findings of childhood absence epilepsy in order to highlight areas of consensus as well as areas of uncertainty that indicate directions for future research.

Epileptic encephalopathies in adults and childhood

Epileptic encephalopathies are motor-mental retardations or cognitive disorders secondary to epileptic seizures or epileptiform activities. Encephalopaties due to brain damage, medications, or systemic diseases are generally not in the scope of this definition, but they may rarely accompany the condition. Appropriate differential diagnosis of epileptic seizures as well as subclinical electroencephalographic discharges are crucial for management of seizures and epileptiform discharges and relative regression of cognitive deterioration in long-term followup. Proper antiepileptic drug, hormonal treatment, or i.v. immunoglobulin choice play major role in prognosis. In this paper, we evaluated the current treatment approaches by reviewing clinical electrophysiological characteristics of epileptic encephalopathies.

Antiepileptic drug monotherapy versus polytherapy: pursuing seizure freedom and tolerability in adults

PURPOSE OF REVIEW

Despite the availability of many new antiepileptic drugs (AEDs), only around 50% of people with epilepsy will become seizure free on their first drug. This article explores treatment options and issues influencing whether AEDs should be substituted or combined in the remainder of the patient population.

RECENT FINDINGS

Prior to the introduction of novel AEDs, it was generally opined that combining traditional agents did not necessarily lead to an improvement in seizure control and might increase the propensity for side effects. Newer AEDs, many with different mechanisms of action, have increased the potential for polytherapy regimens, although robust data to support or refute this therapeutic strategy are sparse. It seems sensible to substitute rather than combine when the first AED produces an idiosyncratic reaction, is poorly tolerated at a low/moderate dose or shows no efficacy. Polytherapy may be preferred if the patient tolerates their first or second AED well, but with a suboptimal response, particularly when there is an identifiable anatomical substrate for the seizures. AED selection requires consideration of many factors some of which are discussed in this study.

SUMMARY

There are no definitive answers on whether to combine or substitute AEDs. Different strategies are required for different scenarios in different patients.

"Electro-clinical syndromes" with onset in paediatric age: the highlights of the clinical-EEG, genetic and therapeutic advances

The genetic causes underlying epilepsy remain largely unknown, and the impact of available genetic data on the nosology of epilepsy is still limited. Thus, at present, classification of epileptic disorders should be mainly based on electroclinical features. Electro-clinical syndrome is a term used to identify a group of clinical entities showing a cluster of electro-clinical characteristics, with signs and symptoms that together define a distinctive, recognizable, clinical disorder. These often become the focus of treatment trials as well as of genetic, neuropsychological, and neuroimaging investigations. They are distinctive disorders identifiable on the basis of a typical age onset, specific EEG characteristics, seizure types, and often other features which, when taken together, permit a specific diagnosis which, in turn, often has implications for treatment, management, and prognosis. Each electro-clinical syndrome can be classified according to age at onset, cognitive and developmental antecedents and consequences, motor and sensory examinations, EEG features, provoking or triggering factors, and patterns of seizure occurrence with respect to sleep. Therefore, according to the age at onset, here we review the more frequently observed paediatric electro-clinical syndrome from their clinical-EEG, genetic and therapeutic point of views.

Antiepileptic drug therapy: does mechanism of action matter?

This article represents a synthesis of presentations made by the authors during a scientific meeting held in London on 7 June 2010 and organized by GlaxoSmithKline. Each speaker produced a short précis of his lecture to answer a specific question, resulting in an overview of what we know about the relevance of the mechanisms of action of antiepileptic drugs in determining appropriate combination therapies for the treatment of drug-resistant epilepsy.

Experience with lacosamide in a series of children with drug-resistant focal epilepsy

We report our pediatric experience with lacosamide, a new antiepileptic drug, approved by the US Food and Drug Administration as adjunctive therapy in focal epilepsy in patients more than 17 years old. We retrospectively reviewed charts for lacosamide use and seizure frequency outcome in patients with focal epilepsy (Wilcoxon signed rank test). Sixteen patients (7 boys) were identified (median dose 275 mg daily, 4.7 mg/kg daily; mean age 14.9 years, range 8-21 years). Patients were receiving a median of 2 antiepileptic drugs (interquartile range [IQR] 1.7-3) in addition to having undergone previous epilepsy surgery (n=3), vagus nerve stimulation (n=9), and ketogenic diet (n=3). Causes included structural (encephalomalacia and diffuse encephalitis, 1 each; stroke in 2) and genetic abnormalities (Aarskog and Rett syndromes, 1 each) or cause not known (n=10). Median seizure frequency at baseline was 57 per month (IQR 7-75), and after a median follow-up of 4 months (range 1-13 months) of receiving lacosamide, it was 12.5 per month (IQR 3-75), (P<0.01). Six patients (37.5%; 3 seizure free) were classified as having disease that responded to therapy (≥50% reduction seizure frequency) and 10 as having disease that did not respond to therapy (<50% in 3; increase in 1; unchanged in 6). Adverse events (tics, behavioral disturbance, seizure worsening, and depression with suicidal ideation in 1 patient each) prompted lacosamide discontinuation in 4/16 (25%). This retrospective study of 16 children with drug-resistant focal epilepsy demonstrated good response to adjunctive lacosamide therapy (median seizure reduction of 39.6%; 37.5% with ≥50% seizure reduction) without severe adverse events.

"Epileptic encephalopathy" of infancy and childhood: electro-clinical pictures and recent understandings

There is growing interest in the diagnosis of cognitive impairment among children with epilepsy. It is well known that status of seizures control has to be carefully investigated because it can be sufficient "per se" to cause progressive mental deterioration conditions. Subclinical electroencephalographic discharges may have subtle effects on cognition, learning and sleep patterns, even in the absence of clinical or sub-clinical seizures. In this respect, electroencephalographic monitoring (long-term and nocturnal recording) and in particular an all night video-polysomnography (V-NPSG) record can be crucial to detect the presence of unrecognized seizures and/or an inter-ictal nocturnal EEG discharge increasing. Epileptic encephalopathies (EE) are a group of conditions in which the higher cognitive functions are deteriorate as a consequence of epileptic activity, which, in fact, consists of frequent seizures and/or florid and prolonged interictal paroxysmal discharges, focal or generalized. AEDs represent the first line in opposing the burden of both, the poor seizures control and the poor interictal discharges control, in the cognitive deterioration of EE affected children. Thus, to improve the long-term cognitive/behavioural prognosis in these refractory epileptic children, it should be taken into account both a good seizures control and a strict sleep control, choosing carefully antiepileptic drugs which are able to control not only seizures clinically recognizable but even the EEG discharges onset and its increasing and spreading during sleep. Here, we review the efficacy and safety of the newer AEDs that, to date, are used in the treatment of EE in infancy and childhood.

Treatment initiation in epilepsy: an expert consensus in Spain

OBJECTIVE

The goals of this study were to explore the diverse criteria surrounding indications for antiepileptic therapy and to establish a consensus on drug selection for initial monotherapy in adult patients with epilepsy.

METHODS

The study was performed using the modified Delphi method, which aims to achieve professional consensus by means of a series of questionnaires. Three different groups of items were evaluated: the beginning of antiepileptic treatment, the drug selected for initial monotherapy with respect to the type of epilepsy, and the drug selected for initial monotherapy with respect to comorbidity.

RESULTS

Sixty experts completed two rounds of a questionnaire. In the first round, consensus was reached on 135 of the 194 questions analyzed. After the second round, consensus was reached on 148 items. The main findings of the survey revealed a consensus on beginning treatment after the first seizure when the EEG showed abnormalities such as generalized spike-wave discharges, when MRI demonstrated an epileptogenic brain lesion, and in elderly patients. Regarding to the antiepileptic drug selected for initial monotherapy with respect to type of epilepsy, levetiracetam and lamotrigine were recommended for generalized tonic-clonic seizures regardless of sex or age; levetiracetam was recommended for myoclonic epilepsy regardless of sex; valproic acid, ethosuximide, levetiracetam, and lamotrigine were chosen for absence epilepsy; and carbamazepine, levetiracetam, lamotrigine, and oxcarbazepine were recommended for partial epilepsy regardless of age or sex. Finally, in the evaluation of drug selection with respect to comorbidity, first-generation drugs were less recommended than second-generation drugs, which were clearly preferable. The drugs on which there was a greater consensus were levetiracetam, lamotrigine, valproic acid, and topiramate.

CONCLUSIONS

There is a tendency to begin treatment after the first seizure, depending on the results of additional testing. In general, first-generation drugs are less recommended for different types of epilepsy, especially in the presence of a comorbid condition. However, the authors are conveying perceptions and opinions, the effect of which on treatment outcomes has not been evaluated.

The Use of Antiepileptic Drugs (AEDs) for the Treatment of Pediatric Aggression and Mood Disorders

Aggressive symptomatology presents across multiple psychiatric, developmental, neurological and behavioral disorders, complicating the diagnosis and treatment of the underlying pathology. Anti-Epileptic Drugs (AEDs) have become an appealing alternative in the treatment of aggression, mood lability and impulsivity in adult and pediatric populations, although few controlled trials have explored their efficacy in treating pediatric populations. This review of the literature synthesizes the available data on ten AEDs - valproate, carbamazepine, oxcarbazepine, phenytoin, lamotrigine, topiramate, levetiracetam, zonisamide, gabapentin and tiagabine - in an attempt to assess evidence for the efficacy of AEDs in the treatment of aggression in pediatric populations. Our review revealed modest evidence that some of the AEDs produced improvement in pediatric aggression, but controlled trials in pediatric bipolar disorder have not been promising. Valproate is the best supported AED for aggression and should be considered as a first line of treatment. When monotherapy is insufficient, combining an AED with either lithium or an atypical anti-psychotic can result in better efficacy. Additionally, our review indicates that medications with predominately GABA-ergic mechanisms of action are not effective in treating aggression, and medications which decrease glutaminergic transmission tended to have more cognitive adverse effects. Agents with multiple mechanisms of action may be more effective.

Seizure aggravation-evidence that oxcarbazepine requires monitoring

Aggravation of Seizures and/or EEG Features in Children Treated with Oxcarbazepine Monotherapy. Vendrame M, Khurana DS, Cruz M, Melvin J, Valencia I, Legido A, Kothare SV. Epilepsia 2007;48(11):2116–2120. Epub 2007 Jul 21. PURPOSE: Exacerbation of epilepsy may occur following initiation of therapy with antiepileptic drugs (AEDs). The aim of this study is to analyze the clinical and EEG characteristics of a group of pediatric patients with worsening of seizures and/or EEG deterioration while on oxcarbazepine (OXC). METHODS: A retrospective analysis of a clinical database was performed to identify patients with epilepsy treated with OXC over the past 3 years. History, neurological examination, and EEG findings were reviewed to identify any who had developed exacerbation of seizures or new abnormalities on EEG. RESULTS: Of 290 patients on OXC, we identified 12 patients with new onset seizures, all with initial normal neurological exam and normal EEG, who developed either worsening of preexisting seizures, new seizure types, and/or EEG deterioration following introduction of OXC monotherapy. EEG changes were primarily characterized by new onset of generalized epileptiform activity not reported on the initial baseline EEG. Following substitution of OXC with a broad spectrum AED, significant improvement of seizure control and improvement in the EEG was observed. CONCLUSIONS: These findings suggest that OXC can aggravate seizures and/or worsen EEG features in children. Following initiation of therapy with OXC, monitoring of patients with follow-up EEGs may be important, especially in patients who do not show adequate response to therapy.

The ketogenic diet in a pill: is this possible?

Over the past decade, much progress has been made in understanding the mechanisms of ketogenic diet (KD) action. From the complex systemic and metabolic changes induced by the KD have emerged innovative hypotheses attempting to link biochemical adaptations to its clinical effects. Despite such developments, the fundamental question of how the KD works remains as elusive as ever. At present, it is unclear which of the many potential mechanisms proposed thus far are directly relevant to the clinical effects of the KD. It is unlikely that these numerous hypotheses can be unified into a single mechanism (or a final common pathway). Nevertheless, it may be instructive to consider each of these putative mechanisms in turn and ask the following question: if the mechanism or target in question is a critical determinant of the anticonvulsant efficacy of the KD, then would a similar intervention known to be based on that mechanism yield a comparable effect? Perhaps answering this question for each mechanistic speculation might help substantiate (or invalidate) that particular hypothesis. Can the KD be packaged into a pill? At present, the answer is likely "no." We have yet to discover a "magic bullet" that completely mirrors the anticonvulsant (and potential neuroprotective) effects of the KD. However, without a clearer understanding of the mechanistic elements comprising the complex metabolic puzzle posed by the KD, we would be left only with empiric observations, and to wonder curiously how a high-fat diet can exert such profound clinical effects.

Treatment of Lennox-Gastaut syndrome: overview and recent findings

Lennox-Gastaut syndrome (LGS) is a rare, age-related syndrome, characterized by multiple seizure types, a specific electro-encephalographic pattern, and mental regression. However, published data on the etiology, evolution, and therapeutic approach of LGS are contradictory, partly because the precise definition of LGS used in the literature varies. In the most recent classification, LGS belongs to the epileptic encephalopathies and is highly refractory to all antiepileptic drugs. Numerous treatments, medical and non-medical, have been proposed and results mostly from open studies or case series have been published. Sometimes, patients with LGS are included in a more global group of patients with refractory epilepsy. Only 6 randomized double-blind controlled trials of medical treatments, which included patients with LGS, have been published. Overall, treatment is rarely effective and the final prognosis remains poor in spite of new therapeutic strategies. Co-morbidities need specific treatment. This paper summarizes the definition, diagnosis and therapeutic approach to LGS, including not only recognized antiepileptic drugs, but also "off label" medications, immune therapy, diet, surgery and some perspectives for the future.

Topiramate or valproate in patients with juvenile myoclonic epilepsy: a randomized open-label comparison

Few randomized, controlled trials evaluating antiepileptic drug (AED) efficacy and tolerability have focused solely on patients with juvenile myoclonic epilepsy (JME). We conducted a pilot, randomized controlled trial comparing topiramate (N=19) and valproate (N=9) in adolescents/adults with JME to evaluate clinical response when these broad-spectrum agents are titrated to optimal effect. Rating scales were used to systematically assess tolerability. Among patients completing 26 weeks of treatment, 8 of 12 (67%) in the topiramate group and 4 of 7 (57%) in the valproate group were seizure-free during the 12-week maintenance period. Median daily dose was 250mg topiramate or 750mg valproate. Two (11%) topiramate-treated patients and one (11%) valproate-treated patient discontinued due to adverse events. Systemic toxicity scores, but not neurotoxicity scores, differed substantially between the two groups; greater systemic toxicity was associated with valproate. Our preliminary findings that topiramate may be an effective, well-tolerated alternative to valproate warrant validation in a double-blind trial.

Rat epileptic seizures evoked by BmK αIV and its possible mechanisms involved in sodium channels

This study showed that rat unilateral intracerebroventricular injection of BmK alphaIV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK alphaIV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK alphaIV on intrasynaptosomal free calcium concentration [Ca(2+)](i) and sodium concentration [Na(+)](i) revealed that BmK alphaIV-evoked glutamate release from synaptosomes was associated with an increase in Ca(2+) and Na(+) influx. Moreover, BmK alphaIV-mediated glutamate release and ion influx was completely blocked by tetrodotoxin, a blocker of sodium channel. Together, these results suggest that the induction of BmK alphaIV-evoked epileptic seizures may be involved in the modulation of BmK alphaIV on tetrodotoxin-sensitive sodium channels located on the nerve terminal, which subsequently enhances the Ca(2+) influx to cause an increase of glutamate release. These findings may provide some insight regarding the mechanism of neuronal action of BmK alphaIV in the central nervous system for understanding epileptogenesis involved in sodium channels.

Antiepileptic drug treatment in children

Epilepsy is one of the most common neurological disorders of childhood, and antiepileptic drugs represent the main component of its treatment. The current emphasis in epilepsy treatment is to improve quality of life, not only by suppressing seizure, but also by minimizing the side effects of medications. The last 15 years have been characterized by significant advances in the development of new agents that have helped us to get closer to this goal. Knowledge of the essential properties, key indications and interactions of each antiepileptic drug will help to optimize efficacy and reduce adverse reactions. Age is also a determining factor of the epilepsy phenotype and its treatment. This review addresses the principles of pediatric epilepsy treatment, summarizes the profile of each of the commonly used antiepileptic drugs, and provides a treatment paradigm for particular seizures and epilepsy syndromes of childhood.

Lacosamide: a review of preclinical properties

Lacosamide (LCM), (SPM 927, (R)-2-acetamido-N-benzyl-3-methoxypropionamide, previously referred to as harkoseride or ADD 234037) is a member of a series of functionalized amino acids that were specifically synthesized as anticonvulsive drug candidates. LCM has demonstrated antiepileptic effectiveness in different rodent seizure models and antinociceptive potential in experimental animal models that reflect distinct types and symptoms of neuropathic as well as chronic inflammatory pain. Recent results suggest that LCM has a dual mode of action underlying its anticonvulsant and analgesic activity. It was found that LCM selectively enhances slow inactivation of voltage-gated sodium channels without affecting fast inactivation. Furthermore, employing proteomic affinity-labeling techniques, collapsin-response mediator protein 2 (CRMP-2 alias DRP-2) was identified as a binding partner. Follow-up experiments confirmed a functional interaction of LCM with CRMP-2 in vitro. LCM did not inhibit or induce a wide variety of cytochrome P450 enzymes at therapeutic concentrations. In safety pharmacology and toxicology studies conducted in mice, rats, rabbits, and dogs, LCM was well tolerated. Either none or only minor side effects were observed in safety studies involving the central nervous, respiratory, gastrointestinal, and renal systems and there is no indication of abuse liability. Repeated dose toxicity studies demonstrated that after either intravenous or oral administration of LCM the adverse events were reversible and consisted mostly of exaggerated pharmacodynamic effects on the CNS. No genotoxic or carcinogenic effects were observed in vivo, and LCM showed a favorable profile in reproductive and developmental animal studies. Currently, LCM is in a late stage of clinical development as an adjunctive treatment for patients with uncontrolled partial-onset seizures, and it is being assessed as monotherapy in patients with painful diabetic neuropathy. Further trials to identify LCM's potential in pain and for other indications have been initiated.

The office management of epilepsy

Epilepsy in children is mostly diagnosed and treated in an ambulatory office setting. This article reviews the literature and offers opinions about the best practice from the time of diagnosis through to remission and beyond. The diagnosis and assignment of an epilepsy syndrome may be difficult, and even experts disagree in many cases. Regular review of the basic diagnosis and semiology of seizures is suggested throughout treatment. Workup should always include an electroencephalogram and usually magnetic resonance imaging. Antiepileptic drugs (AEDs) suppress seizures but appear to have little effect on long-term remission, and the choice of AED is for the most part arbitrary with most AEDs having a similar success rate when used as the first drug. Families have a great need for accurate information, and their ability to cope with the unpredictable nature of seizures may be assisted by "rescue" home benzodiazepines. Surveillance for drug toxicity and side effects is a critical clinical skill that is not assisted by routine blood tests or AED serum levels. Most children with epilepsy do not have many seizures and need not have significant restrictions on their activities. In the long run, comorbidities (especially learning and behavior problems) have a greater impact on social function than the epilepsy. Management of these problems may extend well beyond remission of the epilepsy. The child neurologist needs to prepare children with persistent epilepsy for transfer to adult epilepsy services.

Lamotrigine adjunctive therapy among children and adolescents with primary generalized tonic-clonic seizures

CONTEXT AND OBJECTIVE

Primary generalized tonic-clonic seizures are relatively more common among children than among adults. Primary generalized tonic-clonic seizures are associated with increased risk of injury and death. Therefore, effective control of primary generalized tonic-clonic seizures is necessary to reduce epilepsy-related morbidity and mortality. Lamotrigine has demonstrated efficacy from published randomized clinical trials for childhood partial seizures, absence seizures, and for the generalized seizures associated with Lennox-Gastaut syndrome. A randomized, blinded, placebo-controlled study was conducted to assess the efficacy and tolerability of adjunctive therapy with lamotrigine in the treatment of primary generalized tonic-clonic seizures among patients > or = 2 years of age; we report the data from children and adolescents 2 to 20 years of age from this randomized clinical trial. This is the first published analysis of data from a randomized, double-blind, controlled clinical trial of primary generalized tonic-clonic seizures focusing on children and adolescents.

PATIENTS AND METHODS

We randomly assigned (1:1) 117 patients, aged 2 to 55 years, with primary generalized tonic-clonic seizures inadequately controlled on 1 to 2 current antiepileptic drugs and with evidence of primary generalized tonic-clonic seizures on electroencephalogram and no historical or electroencephalogram evidence of partial seizures to either lamotrigine or placebo in a double-blind parallel group clinical trial from 2001 through 2004. We analyzed the subgroup of children and adolescents, aged 2 to 20 years (n = 45), from this randomized clinical trial. Patients having > or = 3 primary generalized tonic-clonic seizures over an 8-week baseline were randomly assigned (1:1) to receive either lamotrigine or placebo. The treatment period consisted of an escalation phase (12 weeks for patients 2-12 years; 7 weeks for patients > 12 years) and a maintenance phase (12 weeks). The study had 4 phases: screening phase, baseline phase, escalation phase, and maintenance phase. During the screening phase, baseline medical examinations and seizure type and seizure frequency assessments were performed. During the 8-week baseline phase, the number and dosages of concomitant antiepileptic drugs were maintained while seizure frequency was assessed. The assessment of primary generalized tonic-clonic seizure frequency was determined during the 8-week baseline phase. Patients eligible for random assignment experienced > or =3 primary generalized tonic-clonic seizures during the baseline phase and > or = 1 primary generalized tonic-clonic seizure in the 8 weeks before the baseline phase. Lamotrigine was introduced and titrated using a schedule based on the patients' age and concurrent antiepileptic drug regimen. During the escalation phase, the number and doses of concomitant antiepileptic drugs were not changed. The escalation phase was followed by a 12-week maintenance phase during which time the lamotrigine dose was maintained at a specific dose defined by the patients' age and concomitant antiepileptic drugs, whereas the doses of concurrent antiepileptic drugs were maintained at a constant dose. Concurrent antiepileptic drugs could not be discontinued or added during the maintenance phase. The primary efficacy end point measure was the median reduction in the frequency of primary generalized tonic-clonic seizures from baseline; seizure counts were recorded prospectively in standardized daily seizure diaries. Other efficacy end point data for analysis were as follows: the median seizure counts, the median percentage change from the baseline phase in average monthly seizure frequency for other generalized seizure types, and the percentage of patients with a reduction of > or = 25%, > or = 50%, > or = 75%, or 100% in frequencies of primary generalized tonic-clonic seizures and all generalized seizures during the escalation phase and/or maintenance phase relative to the baseline phase. Accurate counts of absence seizure frequency require electroencephalogram-video monitoring; absence seizure frequency was not an outcome measure for this analysis.

RESULTS

Forty-five (21 lamotrigine and 24 placebo) patients 2 to 19 years of age were randomly assigned and received study drug. Eight patients (3 lamotrigine and 5 placebo) had a combination of clinical (myoclonus and/or absence seizures) and electroencephalogram findings that were consistent with juvenile myoclonic epilepsy. Among the 45 children randomly assigned, 74% had generalized spike, polyspike, and/or generalized spike and wave discharges on routine electroencephalogram recordings; the remaining 26% of children had no electroencephalogram findings suggestive of partial epilepsy and a clear history consistent with primary generalized tonic-clonic seizures. Electroencephalogram findings were not significantly different between the lamotrigine and the placebo treatment groups. The median percentage decrease from baseline in primary generalized tonic-clonic seizures during the entire treatment period was 77% in the lamotrigine group and 40% in the placebo group (P = .044). The median primary generalized tonic-clonic seizure counts per month were 0.7 in the lamotrigine group and 3.6 in the placebo group during escalation (P = .008), 0.3 in the lamotrigine group and 2.0 in the placebo group during maintenance (P = .005), and 0.4 in the lamotrigine group and 2.5 in the placebo group during the entire treatment period (P = .007). Trends were noted during escalation and maintenance with a median percentage decrease in primary generalized tonic-clonic seizures during escalation of 72% in the lamotrigine group and 30% in the placebo group (P = .059), and 83% in the lamotrigine group and 42% in the placebo group during maintenance (P = .058). During the maintenance phase, 48% of lamotrigine patients were seizure free compared with 17% treated with placebo (P = .051). One patient from each treatment group discontinued from the study because of an adverse event; 1 patient who received lamotrigine experienced "disorientation"; and 1 patient who received placebo had a convulsion with apnea. No rashes occurred among patients taking lamotrigine or placebo. No patient experienced worsening of the intensity or frequency of myoclonus.

CONCLUSIONS

Adjunctive lamotrigine therapy seems effective in controlling primary generalized tonic-clonic seizures among patients 2 to 20 years of age.

Enhancement of brain kynurenic acid production by anticonvulsants—Novel mechanism of antiepileptic activity?

In this study, we describe the effect of antiepileptic drugs on the production of kynurenic acid in rat cortical slices, and on the activity of kynurenic acid biosynthetic enzymes, kynurenine aminotransferases (KATs I and II) in the brain tissue. Phenobarbital, felbamate, phenytoin and lamotrigine (all at 0.5-3.0 mM) enhanced kynurenic acid production in vitro, and stimulated the activity of KAT I. In contrast, vigabatrin, gabapentin and tiagabine inhibited kynurenic acid synthesis in cortical slices with IC(50) of 3.9 (2.8-7.9), 3.7 (2.5-5.4) and 7.5 (3.5-14.3) mM, respectively. Vigabatrin, gabapentin and tiagabine reduced also the activity of KAT I with IC(50) of 1.6 (1.1-2.4), 0.1 (0.01-0.15), 0.9 (0.7-1.2) mM, and the activity of KAT II with IC(50) values of 6.0 (4.8-7.5), 0.2 (0.1-0.3) and 2.0 (1.5-2.6) mM, respectively. In conclusion, the enhancement of kynurenic acid formation displayed by carbamazepine, phenytoin, phenobarbital, felbamate and lamotrigine seems to be a novel mechanism, synergistic with other actions of these drugs, and potentially valuable in terms of better control of epilepsy.