Felbamate in the treatment of Lennox-Gastaut syndrome

Pharmacotherapeutic management of seizures in patients with Angleman syndrome

Approximately 80-90% of patients with Angelman syndrome (AS) develop childhood-onset intractable seizures with major negative impact on the quality of life.Thus adequate management of seizures is the most critical priority to improve health-related quality of life in children with AS.

AREAS COVERED

The primary focus of the review is on pharmacotherapeutic management of seizures. The first part of the review briefly discusses epileptogenesis and polymorphic seizure phenotypes associated with AS to understand pharmacotherapeutic decision-making better. Next, the review explores individual antiseizure medicines (ASMs) and their potential therapeutic utility. Lastly, some future and emerging treatment options are discussed that can transform the management of seizures in patients with AS.

EXPERT OPINION

Evidence for treating seizures in AS mainly derives from low-quality studies. Levetiracetam and clobazam are the most commonly used ASMs. Although the potential utility of several other ASMs(valproate, topiramate, lamotrigine, ethosuximide, clonazepam) has been well documented for some time, the treatment landscape may rapidly evolve due to the availability of newer and better tolerated ASMs(cannabidiol oil, brivaracetam, perampanel). In addition, a better understanding of the underlying pathogenesis and the development of molecular therapeutics offer hope for precision therapies for seizures.

Efficacy and safety of antiseizure medication for Lennox-Gastaut syndrome: a systematic review and network meta-analysis

AIM

To compare and rank the efficacy and safety of antiseizure medication (ASM) in patients with Lennox-Gastaut syndrome (LGS).

METHOD

We included randomized controlled trials (RCTs) assessing the efficacy of ASM for LGS compared with placebo or with each other. The efficacy and safety were reported in terms of an at least 50% monthly seizure frequency reduction in drop seizures, dropout, and serious adverse events. Outcomes were ranked according to the surface under the cumulative ranking curve (SUCRA).

RESULTS

A total of eight RCTs with 1171 patients were included, involving six ASMs: lamotrigine, rufinamide, cannabidiol, topiramate, clobazam, and felbamate. The calculated SUCRA showed that rufinamide, cannabidiol, and topiramate had the highest probability of achieving a response; however, no significant differences were found among these treatments. Cannabidiol, topiramate, and rufinamide were more likely to result in dropouts; moreover, a significantly greater percentage of patients receiving cannabidiol experienced premature discontinuation as compared to placebo, clobazam, and lamotrigine.

INTERPRETATION

All ASMs showed a significantly higher response rate than placebo. SUCRA ranking demonstrated that rufinamide and cannabidiol are more efficacious than other treatments in reducing drop seizures. However, there was no significant difference between these treatments.

Anti-seizure medications for Lennox-Gastaut syndrome

BACKGROUND

Lennox-Gastaut syndrome (LGS) is an age-specific epilepsy syndrome characterised by multiple seizure types, including drop seizures. LGS has a characteristic electroencephalogram, an onset before age eight years and an association with drug resistance. This is an updated version of the Cochrane Review published in 2013.

OBJECTIVES

To assess the efficacy and tolerability of anti-seizure medications (ASMs) for LGS.

SEARCH METHODS

We searched the Cochrane Register of Studies (CRS Web) and MEDLINE (Ovid, 1946 to 28 February 2020) on 2 March 2020. CRS Web includes randomised controlled trials (RCTs) or quasi-RCTs from the Cochrane Central Register of Controlled Trials (CENTRAL); the Specialised Registers of Cochrane Review Groups, including Cochrane Epilepsy; PubMed; Embase; ClinicalTrials.gov; and the World Health Organization's International Clinical Trials Registry Platform (ICTRP). We imposed no language restrictions. We contacted pharmaceutical companies and colleagues in the field to seek any unpublished or ongoing studies.

SELECTION CRITERIA

We considered RCTs, including cross-over trials, of ASMs for LGS in children and adults. We included studies of ASMs used as either monotherapy or as an add-on (adjunctive) therapy. We excluded studies comparing different doses of the same ASM.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures, including independent, dual assessment for risk of bias and application of the GRADE approach to rate the evidence certainty for outcomes.

MAIN RESULTS

We found no trials of ASM monotherapy. The review included 11 trials (1277 participants; approximately 11 weeks to 112 weeks follow-up after randomisation) using add-on ASMs for LGS in children, adolescents and adults. Two studies compared add-on cannabidiol (two doses) with add-on placebo in children and adolescents only. Neither study reported overall seizure cessation or reduction. We found high-certainty evidence that 72 more people per 1000 (confidence interval (CI) 4 more to 351 more) had adverse events (AE) leading to study discontinuation with add-on cannabidiol, compared to add-on placebo (two studies; 396 participants; risk ratio (RR) 4.90, 95% CI 1.21 to 19.87). One study compared add-on cinromide with add-on placebo in children and adolescents only. We found very low-certainty evidence that 35 more people per 1000 (CI 123 fewer to 434 more) had 50% or greater average reduction of overall seizures with add-on cinromide compared to add-on placebo (one study; 56 participants; RR 1.15, 95% CI 0.47 to 2.86). This study did not report participants with AE leading to study discontinuation. One study compared add-on clobazam (three doses) with add-on placebo. This study did not report overall seizure cessation or reduction. We found high-certainty evidence that 106 more people per 1000 (CI 0 more to 538 more) had AE leading to study discontinuation with add-on clobazam compared to add-on placebo (one study; 238 participants; RR 4.12, 95% CI 1.01 to 16.87). One study compared add-on felbamate with add-on placebo. No cases of seizure cessation occurred in either regimen during the treatment phase (one study; 73 participants; low-certainty evidence). There was low-certainty evidence that 53 more people per 1000 (CI 19 fewer to 716 more) with add-on felbamate were seizure-free during an EEG recording at the end of the treatment phase, compared to add-on placebo (RR 2.92, 95% CI 0.32 to 26.77). The study did not report overall seizure reduction. We found low-certainty evidence that one fewer person per 1000 (CI 26 fewer to 388 more) with add-on felbamate had AE leading to study discontinuation compared to add-on placebo (one study, 73 participants; RR 0.97, 95% CI 0.06 to 14.97). Two studies compared add-on lamotrigine with add-on placebo. Neither study reported overall seizure cessation. We found high-certainty evidence that 176 more people per 1000 (CI 30 more to 434 more) had ≥ 50% average seizure reduction with add-on lamotrigine compared to add-on placebo (one study; 167 participants; RR 2.12, 95% CI 1.19 to 3.76). We found low-certainty evidence that 40 fewer people per 1000 (CI 68 fewer to 64 more) had AE leading to study-discontinuation with add-on lamotrigine compared to add-on placebo (one study; 169 participants; RR 0.49, 95% CI 0.13 to 1.82). Two studies compared add-on rufinamide with add-on placebo. Neither study reported seizure cessation. We found high-certainty evidence that 202 more people per 1000 (CI 34 to 567 more) had ≥ 50% average seizure reduction (one study; 138 participants; RR 2.84, 95% CI 1.31 to 6.18). We found low-certainty evidence that 105 more people per 1000 (CI 17 fewer to 967 more) had AE leading to study discontinuation with add-on rufinamide compared to add-on placebo (one study; 59 participants; RR 4.14, 95% CI 0.49 to 34.86). One study compared add-on rufinamide with another add-on ASM. This study did not report overall seizure cessation or reduction. We found low-certainty evidence that three fewer people per 1000 (CI 75 fewer to 715 more) had AE leading to study discontinuation with add-on rufinamide compared to another add-on ASM (one study; 37 participants; RR 0.96, 95% CI 0.10 to 9.57). One study compared add-on topiramate with add-on placebo. This study did not report overall seizure cessation. We found low-certainty evidence for ≥ 75% average seizure reduction with add-on topiramate (one study; 98 participants; Peto odds ratio (Peto OR) 8.22, 99% CI 0.60 to 112.62) and little or no difference to AE leading to study discontinuation compared to add-on placebo; no participants experienced AE leading to study discontinuation (one study; 98 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

RCTs of monotherapy and head-to-head comparison of add-on ASMs are currently lacking. However, we found high-certainty evidence for overall seizure reduction with add-on lamotrigine and rufinamide, with low-certainty evidence for AE leading to study discontinuation compared with add-on placebo or another add-on ASM. The evidence for other add-on ASMs for overall seizure cessation or reduction was low to very low with high- to low-certainty evidence for AE leading to study discontinuation. Future research should consider outcome reporting of overall seizure reduction (applying automated seizure detection devices), impact on development, cognition and behaviour; future research should also investigate age-specific efficacy of ASMs and target underlying aetiologies.

A reappraisal of atypical absence seizures in children and adults: therapeutic implications

Introduction: Atypical absences are generalized epileptic seizures typically affecting children with severe epilepsies and learning difficulties along with other seizure types. Video-EEG is essential for their diagnosis. Recently, atypical absence seizures have been reported as a hallmark of some developmental and epileptic encephalopathies.Areas covered: This is a narrative review of the literature which describes the electroclinical features of atypical seizures, the characteristics of developmental epileptic encephalopathies in which this seizure type can occur, and the evidence supporting the use of individual antiseizure drugs for the treatment of atypical absences.Expert opinion: Treatment of absence seizures typically relies on ethosuximide (ineffective against tonic-clonic seizures), valproate (associated with larger proportion of adverse events), or lamotrigine (less effective than the other two). However, unlike typical absences, atypical absences are usually intractable, persist lifetime, and their prognosis depends on the underlying etiology or associated epilepsy syndrome. Besides efficacy, other relevant factors, such as drug formulation, ease of titration and dosing, and drug interactions, should be considered. Drugs that may worsen epilepsy, cognition and behavior should be avoided. In the vast majority of patients, a polytherapy is required, although usually with limited efficacy. Finally, epilepsy syndromes featuring atypical absences require a multidisciplinary approach.

Efficacy, Retention, and Tolerability of Brivaracetam in Patients With Epileptic Encephalopathies: A Multicenter Cohort Study From Germany

Objective: To evaluate the efficacy and tolerability of brivaracetam (BRV) in a severely drug refractory cohort of patients with epileptic encephalopathies (EE).

Method: A multicenter, retrospective cohort study recruiting all patients treated with EE who began treatment with BRV in an enrolling epilepsy center between 2016 and 2017.

Results: Forty-four patients (27 male [61%], mean age 29 years, range 6 to 62) were treated with BRV. The retention rate was 65% at 3 months, 52% at 6 months and 41% at 12 months. A mean retention time of 5 months resulted in a cumulative exposure to BRV of 310 months. Three patients were seizure free during the baseline. At 3 months, 20 (45%, 20/44 as per intention-to-treat analysis considering all patients that started BRV including three who were seizure free during baseline) were either seizure free (n = 4; 9%, three of them already seizure-free at baseline) or reported at least 25% (n = 4; 9%) or 50% (n = 12; 27%) reduction in seizures. An increase in seizure frequency was reported in two (5%) patients, while there was no change in the seizure frequency of the other patients. A 50% long-term responder rate was apparent in 19 patients (43%), with two (5%) free from seizures for more than six months and in nine patients (20%, with one [2 %] free from seizures) for more than 12 months. Treatment-emergent adverse events were predominantly of psychobehavioural nature and were observed in 16%.

Significance: In this retrospective analysis the rate of patients with a 50% seizure reduction under BRV proofed to be similar to those seen in regulatory trials for focal epilepsies. BRV appears to be safe and relatively well tolerated in EE and might be considered in patients with psychobehavioral adverse events while on levetiracetam.

Treatment-resistant Lennox-Gastaut syndrome: therapeutic trends, challenges and future directions

Lennox-Gastaut syndrome is a severe, childhood-onset electroclinical syndrome comprised of multiple seizure types, intellectual and behavioral disturbances and characteristic findings on electroencephalogram of slow spike and wave complexes and paroxysmal fast frequency activity. Profound morbidity often accompanies a common and severe seizure type, the drop attack. Seizures often remain refractory, or initial treatment efficacy fades. Few individuals are seizure free despite the development of multiple generations of antiseizure medications over decades and high-level evidence on several choices. Approved medications such as lamotrigine, topiramate, rufinamide, felbamate and clobazam have demonstrated efficacy in reducing seizure burden. Cannabidiol has emerged as a promising investigational therapy with vast social interest yet lacks a standard, approved formulation. Palliative surgical procedures, such as vagal nerve stimulation and corpus callosotomy may provide reduction in total seizures and drop attacks. Emerging evidence suggests that complete callosotomy provides greater improvement in seizures without additional side effects. Etiologies such as dysplasia or hypothalamic hamartoma may be amenable for focal resection and thus offer potential to reverse this devastating epileptic encephalopathy.

Pharmacological interventions for epilepsy in people with intellectual disabilities

BACKGROUND

The prevalence of epilepsy among people with intellectual disabilities is much higher than in the general population. Seizures in this population are often complex and refractory to treatment and antiepileptic medication may have a profound effect upon behaviour (Kerr 1997).This is an updated version of a Cochrane Review first published in Issue 3, 2007.

OBJECTIVES

To assess the data available from randomised controlled trials (RCTs) of the efficacy of antiepileptic drug (AED) interventions in people with epilepsy and intellectual disabilities.

SEARCH METHODS

For the latest update of this review, we searched the Cochrane Epilepsy Group Specialised Register (2 September 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO) (2 September 2014), MEDLINE (Ovid, 1946 to 3 September 2014) and PsycINFO (EBSCOhost, 1887 to 3 September 2014).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials (RCTs) of pharmacological interventions for people with epilepsy and a learning disability.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We contacted study authors for additional information. We assessed epilepsy/seizure, behavioural and cognitive outcomes, as well as quality of life and adverse effects.

MAIN RESULTS

We included 14 RCTs (1116 participants) in the present review. Data were heterogenous and a descriptive analysis is presented. In the majority of cases where antiepileptic drugs (AEDs) were trialled in this population, we found moderate reductions in seizure frequency in that there was a significantly higher rate of responders (reduction of 50% or more) in the treatment group compared with the placebo group, with some studies reporting a higher incidence of seizure freedom in the treatment group. In general, AEDs that are proven to be effective in the general epilepsy population are also effective for refractory epilepsy in people with intellectual disability. It is not possible to comment on the relative efficacy of medications, making clinical decisions difficult.In trial settings patients continued on treatment in the majority of cases. Placebo groups often experienced fewer adverse events. Where adverse events were experienced they appeared similar to those in the general population. The methods by which adverse events were recorded and reported appeared to be inconsistent, resulting in very large variation between studies. This is problematic as clinically relevant interpretation of these findings is limited.The quality of evidence provided in the present review is low to moderate. Additionally the majority of studies lacked or used non-reliable measures of behavioural exacerbation. However, where measured, little obvious impact on behaviour was seen in terms of behaviour disorder.

AUTHORS' CONCLUSIONS

This review broadly supports the use of AEDs to reduce seizure frequency in people with refractory epilepsy and intellectual disability. The evidence suggests that adverse events are similar to those in the general population and that behavioural adverse events leading to discontinuation are rare; however, other adverse effects are under-researched.

Localization of epileptogenic zones in Lennox-Gastaut syndrome (LGS) using graph theoretical analysis of ictal intracranial EEG: a preliminary investigation

INTRODUCTION

Precise localization of epileptogenic zones is essential for the successful surgical treatment of refractory epilepsy including Lennox-Gastaut syndrome (LGS). The surgical resection areas are generally determined by epileptologists based on diverse neuroimaging modalities; however, exact epileptogenic zones cannot be accurately localized in many patients with LGS using the conventional methods. Therefore, new reliable algorithms are still required for enhancing the success rate of the resective epilepsy surgery. In the present study, we introduce an approach to localize epileptogenic zones in LGS based on the graph theoretical analysis of ical intracranial EEG (iEEG).

METHODS

Four patients with LGS who became seizure-free after the resective epilepsy surgery were selected. Before the surgery, their epileptogenic zones were delineated using EEG, iEEG, and several conventional imaging modalities. Phase locking value (PLV) analysis was applied to construct functional connectivity networks during ictal events, and then several graph theoretical indices including betweenness centrality (BC) were evaluated for each iEEG sensor to find the primary hubs of the ictal epileptic network. The graph theoretical index values were then overlaid on 3D individual cortical surface.

RESULTS

The iEEG channels with high BC values coincided well with the surgical resection areas. Among various graph theoretical measures such as local efficiency, participation coefficient, and eigenvector centrality, only BC showed fair correspondence with the surgical resection areas.

CONCLUSIONS

The primary hubs in the ictal epileptic networks coincided well with areas of surgical resection in LGS patients with successful surgical outcomes. This observation warrants further studies to determine if the graph theoretical network analysis of ictal iEEG recordings can serve as a new auxiliary tool to localize epileptogenic zones in LGS.

Experience in the use of clobazam in the treatment of Lennox-Gastaut syndrome

Clobazam is a 1,5-benzodiazepine used successfully worldwide since the 1970s as an anxiolytic and antiepileptic drug. Since its recent Food and Drug Administration (FDA) approval in the United States in 2011 as adjunctive treatment for Lennox-Gastaut syndrome, it has continued to show sustained efficacy and a better safety and tolerability profile compared with other benzodiazepines. The two randomized, controlled studies that led to the US FDA approval, as well as the follow-up multicenter, open-label study of clobazam, showed ≥50% seizure reduction for more than 50% of Lennox-Gastaut syndrome patients, while none of the other FDA-approved treatments for LGS have demonstrated efficacy rates better than 50%. Clobazam appears to have a safe profile and sustained effectiveness over the first 3 years of use in LGS and other epilepsy syndromes with intractable seizures, which makes it a viable long-term treatment option.

Treatment of Lennox-Gastaut syndrome

BACKGROUND

The Lennox-Gastaut syndrome (LGS) is an age-specific disorder, characterised by epileptic seizures, a characteristic electroencephalogram (EEG), psychomotor delay and behavioural disorder. It occurs more frequently in males and onset is usually before the age of eight years, with a peak between three and five years of age. Late cases occurring in adolescence and early adulthood have rarely been reported. Language is frequently affected, with both slowness in ideation and expression in addition to difficulties of motor dysfunction. Severe behavioural disorders (e.g. hyperactivity, aggressiveness and autistic tendencies) and personality disorders are nearly always present. There is also a tendency for psychosis to develop with time. The long-term prognosis is poor; although the epilepsy often improves, complete seizure freedom is rare and conversely the mental and psychiatric disorders tend to worsen with time.

OBJECTIVES

To compare the effects of pharmaceutical therapies used to treat LGS in terms of control of seizures and adverse effects. Many people who suffer from this syndrome will already be receiving other antiepileptic medications at the time of their entry into a trial. However, for the purpose of this review we will only consider the effect of the single therapeutic agent being trialled (often as add-on therapy).

SEARCH METHODS

We searched the Cochrane Epilepsy Group's Specialized Register (18 October 2012), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library Issue 10 of 12, 2012) and MEDLINE (1946 to October week 2, 2012). We also searched EMBASE (1980 to March 2003). We imposed no language restrictions. We searched the International Standard Randomised Controlled Trial Number (ISRCTN) register (18 October 2012) for ongoing trials and in addition, we contacted pharmaceutical companies and colleagues in the field to seek any unpublished or ongoing studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs) of the administration of drug therapy to patients with LGS.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. Analysis included assessing study quality, as well as statistical analysis of the effects on overall seizure rates and effects on specific seizure types (e.g. drop attacks), adverse effects and mortality.

MAIN RESULTS

We found nine RCTs, but were unable to perform any meta-analysis, because each trial looked at different populations, different therapies and considered different outcomes.

AUTHORS' CONCLUSIONS

The optimum treatment for LGS remains uncertain and no study to date has shown any one drug to be highly efficacious; rufinamide, lamotrigine, topiramate and felbamate may be helpful as add-on therapy, clobazam may be helpful for drop seizures. Until further research has been undertaken, clinicians will need to continue to consider each patient individually, taking into account the potential benefit of each therapy weighed against the risk of adverse effects.

Update on the management of Lennox-Gastaut syndrome

Lennox-Gastaut syndrome is a severe childhood epilepsy disorder characterized by encephalopathy and multiple, often intractable, seizure types. The drop attack is the most frequently recognizable seizure type in this patient population, and is also the most dangerous physically, thus severely limiting quality of life. The diagnosis is confirmed by electroencephalography, for which the classic pattern is a slow 2.5 Hz generalized spike-and-wave. Newer pharmacologic treatments include rufinimide and clobazam. However, antiepileptic drugs are often exhausted in pursuit of seizure control requiring nonpharmacologic interventions. These include dietary therapies, vagus nerve stimulation, and epilepsy surgery, including corpus callosotomy and focal curative resection. Although large lobar resections are often required, very localized, discrete resections may be possible, as in symptomatic Lennox-Gastaut syndrome (specifically, hypothalamic hamartoma). We review the history of the disease and current management options.

Specific safety and tolerability considerations in the use of anticonvulsant medications in children

Epilepsy is one of the most common neurological disorders in the pediatric age range, and the majority of affected children can be safely and effectively treated with antiepileptic medication. While there are many antiepileptic agents on the market, specific drugs may be more efficacious for certain seizure types or electroclinical syndromes. Furthermore, certain adverse effects are more common with specific classes of medication. Additionally patient-specific factors, such as age, race, other medical conditions, or concurrent medication use may result in higher rates of side effects or altered efficacy. Significant developmental changes in gastric absorption, protein binding, hepatic metabolism, and renal clearance are seen over the pediatric age range, which impact pharmacokinetics. Such changes must be considered to determine optimal dosing and dosing intervals for children at specific ages. Furthermore, approximately one third of children require polytherapy for seizure control, and many more take concurrent medications for other conditions. In such children, drug–drug interactions must be considered to minimize adverse effects and improve efficacy. This review will address issues of antiepileptic drug efficacy, tolerability and ease of use, pharmacokinetics, and drug–drug interactions in the pediatric age range.

Treatment of Lennox-Gastaut syndrome

BACKGROUND

The Lennox-Gastaut syndrome is an age-specific disorder, characterised by epileptic seizures, a characteristic electroencephalogram (EEG), psychomotor delay and behaviour disorders. It occurs more frequently in males and onset is usually before the age of eight, with a peak between three and five years. Late cases occurring in adolescence and early adulthood have rarely been reported. Language is frequently affected, with both slowness in ideation and expression in addition to difficulties of motor dysfunction. Severe behavioural disorders (for example hyperactivity, aggressiveness and autistic tendencies) and personality disorders are nearly always present. There is also a tendency for psychosis to develop with time. The long-term prognosis is poor; although the epilepsy often improves, complete seizure freedom is rare and conversely the mental and psychiatric disorders tend to worsen with time.

OBJECTIVES

To compare the effects of pharmaceutical therapies used to treat Lennox-Gastaut syndrome in terms of control of seizures and adverse effects. Many people who suffer from this syndrome will already be receiving other antiepileptic medications at the time of their entry into a trial. However, for the purpose of this review we will only consider the effect of the single therapeutic agent being trialed (often as add-on therapy).

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group's Specialized Register (February 2009), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2009), and MEDLINE (1950 to January 2009). We also searched EMBASE (1980 to March 2003). We imposed no language restrictions. We searched the ISRCTN register for ongoing trials and in addition, we contacted pharmaceutical companies and colleagues in the field to seek any unpublished or ongoing studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs) of the administration of drug therapy to patients with Lennox-Gastaut syndrome.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. Analysis included assessing study quality, as well as statistical analysis of the effects on overall seizure rates and effects on specific seizure types (e.g. drop attacks), adverse effects and mortality.

MAIN RESULTS

We found seven RCTs, but were unable to perform any meta-analysis, because each trial looked at different populations, different therapies and considered different outcomes.

AUTHORS' CONCLUSIONS

The optimum treatment for Lennox-Gastaut syndrome remains uncertain and no study to date has shown any one drug to be highly efficacious; rufinamide, lamotrigine, topiramate and felbamate may be helpful as add-on therapy. Until further research has been undertaken, clinicians will need to continue to consider each patient individually, taking into account the potential benefit of each therapy weighed against the risk of adverse 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.

Pharmacological interventions for epilepsy in people with intellectual disabilities

BACKGROUND

The development of epilepsy in a person with intellectual disabilities is a common occurrence. In view of the fact that seizures in intellectually disabled people are often complex and refractory to treatment and that antiepileptic medication may have a profound effect upon behaviour in this patient group, it is evident that good quality randomised controlled trials are needed in this population.

OBJECTIVES

The aim of our study was to assess the data available from randomised controlled trials of antiepileptic drug interventions in people with epilepsy and intellectual disabilities.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2006, Issue 4), MEDLINE OVID (1966 to October 2006), PsychInfo OVID (1806 to October 2006) and EMBASE OVID (1980 to April 2005).

SELECTION CRITERIA

Randomised controlled trials (RCTs) of pharmacological interventions for people with epilepsy and a learning disability. RCTs where inadequate methods of allocation concealment had been used were also included.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. Study authors were contacted for additional information. Outcome measures included the following.(1) Retention on treatment.(2) Seizure freedom.(3) Reduction in seizure frequency.(4) Seizure severity scales.(5) Global rating scales.(6) Behavioural outcomes.(7) Cognitive outcomes.(8) Adverse effects.(9) Quality of life.

MAIN RESULTS

Data were heterogenous and a descriptive analysis is presented. This review confirms that in the majority of cases where antiepileptic drugs (AEDs) were trialled in this population, moderate reduction in seizure frequency and occasional seizure freedom were obtained. In general it seems reasonable to say that AEDs proven effective in the general epilepsy population are also effective in refractory epilepsy in people with intellectual disability. It is not possible to comment on relative efficacy between medications making clinical choice decisions difficult. Clinical decision is also likely to be guided by concern over side effects. The quality of the studies does not aid clinicians greatly to this respect. In general it seems that in trial settings patients continue on treatment, in the majority of cases, and placebo groups often experience less in the way of side effects. Where side effects are experienced they appear similar to those seen in non-intellectual disability studies. One area of key concern is that of behavioural exacerbation. The majority of studies are unhelpful due to lack of or non-reliable measures in this area. However, where measured, little obvious impact on behaviour is seen in terms of behaviour disorder.

AUTHORS' CONCLUSIONS

In summary this review broadly supports the use of AEDs to reduce seizure frequency in people with refractory epilepsy and intellectual disability. The evidence suggests that side effects are similar to those in the general population and that behavioural side effects leading to discontinuation are rare but that other effects are under researched.

Cognitive and Behavioral Outcomes of Epileptic Syndromes: Implications for Education and Clinical Practice

The educational and social progress of a child with epilepsy depends not only on seizure control but also on cognitive and behavioral factors. The various epilepsy syndromes of childhood and adolescence differ greatly in terms of cognitive and behavioral outcome. A high proportion of babies who have West syndrome and children who have Dravet syndrome (severe myoclonic epilepsy in infancy) will have long-term cognitive and behavioral problems. The Lennox-Gastaut syndrome also often has a poor prognosis in this regard. Children with the Landau-Kleffner syndrome have a variable prognosis, some regain speech and others have permanent speech impairment. Benign childhood epilepsy with centrotemporal spikes is now recognised as lying on a spectrum with the Landau-Kleffner syndrome: mild cases have few if any cognitive or behavioral problems but others may have quite severe difficulties. People with juvenile myoclonic epilepsy may have characteristics suggesting frontal lobe impairment. The educational and social impairments associated with the epilepsy syndromes of childhood and adolescence are of major importance but they have been the subject of remarkably few well-performed studies. The impairments are not always necessarily permanent and it seems highly likely that the cognitive and behavioural outcome of at least some of these syndromes can be influenced greatly by early effective treatment with either antiepileptic medication or surgery.

Role of valproate across the ages. Treatment of epilepsy in children

In June 2005 a team of experts participated in a workshop with the objective of reaching agreement on the place of valproate use in the treatment of paediatric epilepsy patients. A general "consensus of the meeting" was that the initiation of antiepileptic drug (AED) treatment should be based on a seizure-syndromic approach in children. Participants of the meeting also agreed that valproate is currently the AED with the broadest spectrum across all types of seizures and syndromes. Its superiority has been shown over almost 40 years of clinical experience. The best results are seen in idiopathic generalized epilepsy with or without photosensitivity, idiopathic focal and symptomatic generalized tonic-clonic seizures (GTCS). Evidence supports the use of valproate, ethosuximide and lamotrigine in absence epilepsies and the use of carbamazepine, lamotrigine, oxcarbazepine, phenytoin, topiramate, valproate and phenobarbital for primary GTCS. For new AEDs trials have been undertaken to define their therapeutic role but studies comparing their role to 'old' broad-spectrum drugs in specific syndromes are missing. Experts concluded that intravenous (i.v.) valproate is a useful agent in the treatment of non-convulsive status epilepticus (SE). There is an easy transition to oral treatment following i.v. valproate use. The discussion also concluded that, despite the lack of studies, valproate is an interesting, underutilized alternative in convulsive SE but more controlled studies are needed. The side effects of valproate use are well documented. Its effect on cognition and behaviour is more favourable than many of the other AEDs which is an important consideration in children. Overall, the clinical consensus of the meeting was that valproate's well established therapeutic properties far outweigh the negative side effects. Contraindication or withdrawal should be assessed individually.

Evidence-based Treatment of Idiopathic Generalized Epilepsies with New Antiepileptic Drugs

With the introduction of over ten new antiepileptic drugs (AEDs) since 1993, the hope has been that at least some of these agents would be useful for not just partial seizures, but also for the primary generalized seizures of the idiopathic generalized epilepsies (IGE). The development of evidence-based treatment guidelines in the IGE, however, faces a number of challenges, particularly after an antiepileptic drug (AED) receives approval for one indication. The majority of patients with IGE are controlled with first-line therapy if appropriately selected. Case reports or series typically appear with use in refractory patients, but these studies lack the rigor to allow formulation of guidelines. Still we are beginning to see some good class I and II data to support use of selected second-generation AEDs. It is postulated that lamotrigine (LTG), levetiracetam (LEV), topiramate (TPM), and zonisamide (ZSM) may have efficacy for a broad spectrum of seizure types including those of IGE. At the present time good class I and II evidence exists to support the use of LTG for typical absence, LEV for idiopathic myoclonic seizures, and TPM for primary generalized tonic-clonic seizures, even though only TPM has FDA approval for primary generalized seizures. This article examines the available rigorous evidence that can support these uses and also discusses some selected other reports that suggest a spectrum of efficacy for these new agents.

Topiramate Serum Concentration-to-Dose Ratio

The influence of age and concomitant antiepileptic drugs (AEDs) on the trough steady-state serum concentration of topiramate, normalized to 1 mg/kg body weight or concentration-to-dose ratio (TPM-CDR), was assessed using multivariate methods in samples from 94 epileptic patients (38 under 11 years and 56 over 11 years of age), most of whom were outpatients receiving either just TPM (n = 20) or TPM in combination with other AEDs (n = 74). Analysis of the covariance showed that the age of the patients was influential (P < 0.001) and also showed a difference in TPM-CDR between the non-inducers group (TPM or TPM + lamotrigine or valproate) and the inducers group (TPM + carbamazepine, phenobarbital, or phenytoin) (P < 0.001). The TPM-CDR was 0.4 +/- 0.1 in patients under 11 years with inducers (n = 7), 0.8 +/- 0.3 in patients over 11 years with inducers (n = 32), 1.1 +/- 0.4 in patients under 11 years with noninducers (n = 30), and 1.8 +/- 0.6 in patients over 11 years with noninducers (n = 21). A two-way analysis of the variance showed differences between patients under 11 years and those over 11 years (P < 0.001), and between the noninducers and inducers groups (P < 0.001). TPM-CDR was nearly 50% lower in patients under 11 years than in patients over 11 years, and in patients with TPM + inducers than in patients with TPM or TPM + noninducers, in both children and adults. To achieve the same serum concentration of TPM, children will need double the daily dose per kilogram of TPM required by adults, and both children and adults taking enzyme-inducing AEDs will require double the dose needed by those who do not take them.

Behavioral aspects of pediatric epilepsy syndromes

Apart from control of the seizures, two of the most important factors in determining how well a child with epilepsy progresses toward independence are cognition and behavior. The diagnosis of the correct epilepsy syndrome often provides information with regard to probability of good seizure control and intellectual outcome. However, relatively little has been published on the behavioral aspects of the various epilepsy syndromes. In West syndrome there is emerging evidence that early effective treatment might improve outcome in terms of both cognition and behavior. The work on this syndrome in children with tuberous sclerosis has demonstrated an association between temporal lobe tubers and autism. In Dravet syndrome, a variety of psychiatric disorders have been reported, including hyperactivity and autistic features. This is another epilepsy syndrome that tends to be resistant to treatment, implying that the prognosis has to be guarded. The behavioral problems reported with Lennox-Gastaut syndrome also include autistic features, as well as generally sluggish behavior. It is very likely that these characteristics largely reflect the effect of ongoing seizure activity. Autistic features, aggression, and hyperkinesis have been described with Landau-Kleffner syndrome. The behavior may improve dramatically with appropriate medical treatment or after multiple subpial transection. Although the syndrome of benign partial seizures with centrotemporal or rolandic spikes is said to have a very good prognosis, it is becoming increasingly evident that behavioral problems such as concentration difficulties, tempers, hyperactivity, and impulsivity might occur. Juvenile myoclonic epilepsy has been associated with very variable behavioral traits, sometimes with immature personality features and poor social adjustment suggesting frontal lobe dysfunction. Because many of the reports of behavioral disturbance associated with epilepsy syndromes are anecdotal and do not include validated measures of behavior it would be unwise to draw firm conclusions from them at this stage. Carefully conducted prospective studies, paying particular attention to any behavioral improvements that occur with successful treatment of the epilepsy, are required.

Influence of Dosage, Age, and Co-medication on Plasma Topiramate Concentrations in Children and Adults with Severe Epilepsy and Preliminary Observations on Correlations with Clinical Response

The influence of dosage, age, and co-medication on plasma topiramate (TPM) concentrations at steady state was investigated in 51 patients aged 3 to 30 years. All patients had chronic active epilepsy, and most were receiving concomitant medication with enzyme-inducing anticonvulsants (carbamazepine and phenobarbital). Plasma TPM concentrations were determined by a specific immunoassay in samples obtained before the morning dose. Thirty-five patients could be evaluated prospectively at different dose levels, and the relationship between plasma TPM concentration and dosage was linear over the assessed dose range (1.8 to 10.0 mg/kg) both in adults and in children. The influence of age on pharmacokinetic parameters could be assessed only for the 42 patients co-medicated with enzyme inducers. In these patients dose-normalized plasma TPM concentrations correlated positively with age (r = 0.59, P < 0.0001), where apparent oral clearance values (CL/F) were inversely related to age (r = 0.73, P < 0.0001). In particular, CL/F values in children aged less than 10 years (112 +/- 82 mL/kg/h, mean +/- SD, n = 14) were almost three times as high as those observed in patients aged >15 to 30 years (42 +/- 16 mL/kg/h, n = 17), whereas the CL/F value in children aged 10 to 15 years (66 +/- 22 mL/kg/h, n = 11) was intermediate between those found in the two other age groups. Patients not receiving enzyme-inducing AEDs showed lower CL/F values than did age- and gender-matched patients on enzyme-inducing co-medication. A preliminary evaluation of the relationship between plasma TPM concentration and therapeutic response could be made in 41 patients. No significant difference in drug concentration was detected between patients showing a greater than 50% reduction in seizure frequency compared with baseline (5.9 +/- 2.2 micrograms/mL, n = 30) and those having no clinical improvement (5.2 +/- 2.2 micrograms/mL, n = 11). Likewise, there was no consistent relationship between plasma TPM concentration and appearance of adverse effects. These results indicate that plasma TPM concentrations are linearly related to dosage both in adults and in children and that children aged <10 years require much greater body weight-adjusted dosage to achieve drug levels comparable to those observed in young adults. The marked increase in TPM clearance caused by enzyme-inducing co-medication was confirmed.

Treatment of Lennox-Gastaut syndrome

BACKGROUND

The Lennox-Gastaut syndrome is an age-specific disorder, characterised by epileptic seizures, a characteristic electroencephalogram (EEG), psychomotor delay and personality disorders. It occurs more frequently in males and onset is usually before the age of eight with a peak between three and five years. Late cases occurring in adolescence and early adulthood have rarely been reported. Language is frequently affected with both slowness in ideation and expression in addition to difficulties of motor dysfunction. Severe behavioural disorders (for example hyperactivity, aggressiveness and autistic tendencies)and personality disorders are nearly always present. There is also a tendency for psychosis to develop with time. The long-term prognosis is poor; although the epilepsy often improves, complete seizure freedom is rare and conversely the mental and psychiatric disorders tend to worsen with time.

OBJECTIVES

To compare the effects of pharmaceutical therapies used to treat Lennox-Gastaut syndrome in terms of control of seizures and adverse effects. Many people who suffer from this syndrome will already be receiving other antiepileptic medications at the time of their entry into a trial. However, for the purpose of this review we will only consider the effect of the single therapeutic agent being trialed (often as add-on therapy).

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group trials register (March 2003), MEDLINE (1966 to March 2003) and EMBASE (1980 to March 2003). In addition, we contacted pharmaceutical companies and colleagues in the field to ascertain any unpublished/ongoing studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs) of the administration of drug therapy to patients with Lennox-Gastaut syndrome.

DATA COLLECTION AND ANALYSIS

Data was independently extracted by two reviewers. Analysis included assessing study quality, as well as statistical analysis of the effects on overall seizure rates and effects on specific seizure types (eg drop attacks), adverse effects and mortality.

MAIN RESULTS

We found five RCTs, but were unable to perform any sort of meta-analysis, because each trial looked at different populations, different therapies and considered different outcomes.

REVIEWER'S CONCLUSIONS

The optimum treatment for Lennox-Gastaut syndrome remains uncertain and no study to date has shown any one drug to be highly efficacious; lamotrigine, topiramate and felbamate may be helpful as add-on therapy. Until further research has been undertaken clinicians will need to continue to consider each patient individually, taking into account the potential benefit of each therapy weighed against the risk of adverse effects.

Topiramate therapeutic monitoring in patients with epilepsy: effect of concomitant antiepileptic drugs

The authors assessed the effect of concomitant antiepileptic therapy on steady-state plasma concentrations of the new antiepileptic drug (AED) topiramate and the potential relation between topiramate plasma levels and side effects in a cohort of 116 patients with epilepsy. On the basis of concomitant AEDs, patients were divided into two subgroups, otherwise comparable for age and weight-adjusted daily dose of topiramate. Group A (n = 73) received topiramate plus AED inducers of cytochrome P450 (CYP) metabolism, such as carbamazepine, phenobarbital, and phenytoin. Group B (n = 43) received topiramate plus AEDs without inducing properties of CYP metabolism (namely valproic acid and lamotrigine). Weight-normalized topiramate clearance values, calculated as dosing rate/steady-state plasma drug concentration, were about 1.5-fold in patients receiving AED inducers compared with patients receiving AED noninducers. Topiramate plasma concentrations were linearly related to daily drug doses, regardless of concomitant AED therapy, over a dose range from 25 to 800 mg/d, although, at a given daily dose, a large interpatient variability was observed in matched plasma drug concentrations within each group of patients. Thirty-nine patients (34%) reported side effects associated with topiramate, mostly central nervous system effects. No consistent relation was observed between topiramate plasma concentrations and adverse effects, either in the cohort of patients as a whole or within each subgroup. From a clinical point of view, patients receiving concurrent treatment with enzyme-inducing AEDs can show twofold lower topiramate plasma concentrations compared with patients receiving valproic acid or lamotrigine, and appropriate topiramate dosage adjustments may be required when concomitant AED inducers are either added or withdrawn. Due to the observed variability in topiramate metabolic variables and the complex spectrum of possible pharmacokinetic and pharmacodynamic interactions with the most commonly coprescribed AEDs, monitoring of plasma topiramate concentrations may help the physician in the pharmacokinetic optimization of the drug dosage schedule in individual patients.

Serum concentrations of topiramate in patients with epilepsy: influence of dose, age, and comedication

Topiramate is a new antiepileptic drug (AED) approved as add-on therapy. Previous studies have shown that topiramate has only a limited effect on other AEDs, but its own metabolism can be induced by enzyme-inducing drugs. The aim of this study was to investigate the influence of topiramate dose, age, and comedication, especially of carbamazepine, phenytoin, phenobarbital, oxcarbazepine, lamotrigine, and valproic acid (VPA) on topiramate serum concentrations in patients with epilepsy. In total, 480 samples of 344 inpatients who fulfilled the inclusion criteria (e.g., trough concentration, body weight available) were investigated. The topiramate serum concentration in relation to topiramate dose per body weight (level-to-dose ratio) was calculated and compared for patients receiving topiramate monotherapy and for patients receiving topiramate plus one other AED. Analysis of covariance (using age as covariate) showed that comedication had a highly significant influence on the topiramate serum concentrations. Regression analysis including all 480 samples confirmed that in combinations with phenytoin, carbamazepine, phenobarbital, and oxcarbazepine, the topiramate concentrations were significantly lower compared with topiramate monotherapy, whereas VPA and lamotrigine had no significant influence. Moreover, regression analysis indicated that primidone and methsuximide lowered topiramate concentrations, whereas gabapentin, bromide, and sulthiame did not. In addition to comedication, the patient's age was significantly correlated with topiramate clearance. In accordance with the results of previous studies, these results indicated that infants and children had lower topiramate concentrations than adults receiving the same topiramate dose per body weight. Comedication and age should be considered in adjusting topiramate dosage. Determination of topiramate serum concentrations may be useful, especially when enzyme-inducing drugs are withdrawn or added.

Recent advances in the diagnosis and treatment of epilepsy

Recent advances in the diagnosis and treatment of epilepsies are discussed with special consideration of epidemiology and classification, progress in neuroimaging, electrophysiological studies using EEG and MEG, initiation of medical and surgical treatment, the role of new antiepileptic drugs and selected aspects of genetics of idiopathic epilepsies. In addition from conclusions obtained by the review of recent developments suggestions for future work in Europe are discussed. A constructive approach from multicenter studies requires homologous definitions, documentations and standardization of procedures of trials for European multicenter studies.

Treatment of partial seizures and seizure-like activity with felbamate in six dogs

Six dogs with partial seizures or partial seizure-like activity were treated with the antiepileptic drug felbamate between 1993 and 1998. All dogs had a history and results of diagnostic testing suggestive of either primary (idiopathic) or occult secondary epilepsy. Dogs ranged between four months and eight years of age at the onset of seizure activity. The median time period between onset of the first seizure and the start of felbamate therapy was 3.8 months (range 0.75 to 36 months). Median duration of therapy was nine months (range two to 22 months). All dogs experienced a reduction in seizure frequency after felbamate administration. Median total number of seizures post-treatment was two (range 0 to 9). Two dogs had an immediate and prolonged cessation of seizure activity. Steady-state trough serum felbamate concentrations measured at two weeks, and one, 12 and 22 months after the commencement of therapy in four dogs ranged between 13 and 55 mg/litre (median 35 mg/litre). Reversible haematological adverse effects were detected in two dogs, with one dog developing concurrent keratoconjunctivitis sicca. These results suggest that felbamate can be an effective antiepileptic drug without life-threatening complications when used as monotherapy for partial seizures in the dog.

A randomized open-label study of gabapentin and lamotrigine in adults with learning disability and resistant epilepsy

The aim of this study was to evaluate the efficacy and safety of gabapentin in patients with learning disabilities and resistant epilepsy, comparing the effects of gabapentin with lamotrigine on efficacy, behaviour and mood. An open-label, randomized, parallel group, multicentre add-on study comparing gabapentin with lamotrigine in 109 patients with drug-resistant localization-related epilepsy and learning disabilities was conducted: 39 patients were randomized to gabapentin and 44 to lamotrigine. The study population had a range of learning disabilities and severe partial epilepsy. The percentage of patients achieving a greater than or equal to 50% reduction in seizure frequency on gabapentin was 50%, (mean reduction in seizures was 51%). Compared to 48.6% of lamotrigine patients, no statistically significant treatment differences could be identified. The safety profile of both drugs was consistent with that seen in previous clinical trials. Carer-rated visual analogue scales detected significant improvements (P< 0.05) for the gabapentin-treated patients in seizure severity, attention, general health and sleeping pattern, while for lamotrigine seizure severity improved significantly. For learning disabled patients with resistant epilepsy, gabapentin and lamotrigine provide safe and effective treatment, with positive benefits on behaviour.

A double-blind, placebo-controlled study of topiramate in adult patients with refractory partial epilepsy

PURPOSE

The efficacy and safety of topiramate (TPM) as adjunctive therapy in the treatment of adult Chinese patients with refractory partial epilepsy were investigated in a randomized, double-blind, placebo-controlled study.

METHODS

A total of 46 patients who had four or more complex partial seizures with or without secondary generalization within an 8-week baseline phase were enrolled. Patients were assigned randomly to receive TPM (n = 23) or placebo (n = 23). TPM or placebo was titrated to target doses of 300 mg/d for 6 weeks and maintained at stabilized levels for another 8 weeks. Concomitant antiepileptic drugs remained at constant previous levels during the trial.

RESULTS

In all, 41 patients completed the trial (TPM group, n = 20; placebo group, n = 21). The proportion of patients with a > or =50% reduction from baseline in complex partial seizures was 11 of 23 (47.8%) in the TPM group and 3 of 23 (13.0%) in the placebo group (p = 0.01). In addition, patients treated with TPM had significantly better investigator (p = 0.014) and patient (p = 0.0005) global assessment scores than patients in the placebo group. Adverse events were mostly mild and transient, with no significant differences between treatment groups. Two patients with TPM therapy complained of weight loss. Routine blood cell counts and other laboratory results showed no significant changes from baseline in either treatment group.

CONCLUSIONS

TPM 300 mg/d is effective and well tolerated as treatment for refractory partial epilepsy in adults.

Clinical pharmacology of topiramate: a review

Clinical success with an antiepileptic drug (AED) depends primarily on its efficacy and tolerability. Clinicians also need to have a basic understanding of an AED's pharmacokinetic characteristics, particularly those affecting the potential for drug interactions such as hepatic enzyme inhibition or induction and protein-binding displacement. Successful treatment may be complicated by pharmacokinetic characteristics such as a short half-life, nonlinear kinetics, and active metabolites. Pharmacokinetic characteristics that make a drug easy to use may affect patient adherence. In general, newer AEDs such as topiramate (TPM) are simpler to use than traditional AEDs because they have more favorable pharmacokinetic characteristics and fewer drug interactions.

Topiramate

Six studies are cited to demonstrate that topiramate is effective as adjunctive therapy for refractory partial-onset seizures in adults. Subsequent studies indicate that topiramate is also effective as monotherapy in adults and as adjunctive therapy for partial-onset seizures in children, tonic-clonic seizures of nonfocal origin in children and adults, and drop attacks in Lennox-Gastaut syndrome. Adverse effects for adults and children included dizziness, fatigue, ataxia, confusion, somnolence, nephrolithiasis, paresthesia, and weight loss. More adverse effects were observed at higher doses. Topiramate exhibits rapid absorption, long duration of action, and minimal interaction with other antiepileptic drugs.

Two cases of nonconvulsive status epilepticus in association with tiagabine therapy

We report two patients with intractable partial seizures who developed generalized nonconvulsive status epilepticus (NCSE) after receiving tiagabine (TGB). Neither had a history of absence seizures or generalized epileptic discharges on prior EEG monitoring. Clinicians need to be aware of a possible association between TGB and NCSE.

Estimation of topiramate in subdural cerebrospinal fluid, subcutaneous extracellular fluid, and plasma: a single case microdialysis study

PURPOSE

To estimate topiramate (TPM) concentrations in subdural cerebrospinal fluid (CSF), subcutaneous extracellular fluid (ECF), and plasma and to study the correlation of TPM concentrations in these three different compartments.

METHODS

In this single case study of a patient with drug-resistant partial epilepsy undergoing presurgical evaluation with subdural EEG monitoring, we used microdialysis to estimate concentrations of unbound TPM in CSF of the subdural space and ECF of abdominal subcutaneous tissue. Blood samples were drawn for estimation of TPM concentrations in plasma.

RESULTS

The correlation between unbound TPM concentrations in subdural CSF and abdominal subcutaneous ECF was good. The mean ratio of ECF/CSF TPM concentration was 0.93 (SD+/-0.03) and the correlation coefficient was 0.98. The mean ratio of ECF/total plasma TPM was 0.75 (SD+/-0.06), and the correlation coefficient was 0.99. The mean ratio of CSF/total plasma TPM was 0.81 (SD+/-0.06), and the correlation coefficient was 0.97.

CONCLUSIONS

Assuming a protein binding of TPM of approximately 13%. it is concluded that, based on nine microdialysis samples from a single subject, TPM levels in the CSF at the cortical surface are approximately the same as the unbound plasma levels. Additional patients should be studied to confirm the results.

Qualitative changes of anticonvulsant action of felbamate during development in rats

The anticonvulsant action of felbamate (25, 50, 100 and 150 mg/kg i.p.) was tested against motor seizures induced by pentylenetetrazol in five age-groups of rats (7, 12, 18, 25 and 90 days old). In adult rats, felbamate suppressed generalized tonic-clonic seizures leaving intact minimal clonic seizures. In all groups of rat pups felbamate exhibited a specific action against the tonic phase of generalized tonic-clonic seizures. In addition, the highest dose of felbamate was found to suppress minimal seizures in 18-day-old rats. The changes of felbamate action during ontogeny might be due to multiple mechanisms of anticonvulsant action with an uneven developmental profile.

Advances in the medical treatment of epilepsy

Treatment options for epilepsy, especially using antiepileptic drugs, have increased substantially in the past five years. Since 1993, four novel antiepileptic drugs have been approved and marketed in the United States: felbamate, gabapentin, lamotrigine, and topiramate. Two others, tiagabine and vigabatrin, are likely to be approved in the near future. For many patients, these agents offer the realistic promise of improved seizure control, often with fewer adverse effects and less significant drug interactions compared with older agents. In addition, fosphenytoin, a water-soluble phenytoin prodrug with a number of advantages over intravenous phenytoin, has been released. There are new administration options for carbamazepine, diazepam, and valproic acid. For drug-resistant or -intolerant patients, there has been renewed interest in alternative therapies, especially the ketogenic diet. Taken together, these represent significant therapeutic advances that are benefiting patients with epilepsy. At the same time, improved understanding of the basic mechanisms of epileptogenesis, and of the cellular and molecular actions of available antiepileptic drugs, creates a framework for designing unique therapeutic strategies that are targeted at key sites of vulnerability involved in the development and maintenance of the epileptic state.

Topiramate: a new antiepileptic drug

OBJECTIVE

To review proposed mechanisms of action, clinical pharmacology, efficacy, safety, and tolerability of the antiepileptic drug (AED) topiramate.

METHODS

All available data from the clinical development program--published and unpublished data (provided by investigators or the RW Johnson Pharmaceutical Research Institute)--were analyzed, with emphasis on the results of double-blind, placebo-controlled trials. Data from open-label studies provided information about long-term efficacy and tolerability.

FINDINGS

Topiramate is highly effective in the control of previously therapy-resistant partial seizures, with or without secondary generalization. In the refractory adult patient population enrolled in controlled clinical trials, seizures were reduced by 50% or more in 27-47% of patients compared with 0-18% in placebo-treated patients and by 75% or more in 9-36% of the patients compared with 0-9% of those receiving placebo. The most common adverse effects involve the central nervous system and are mild to moderate in nature. Adverse effects include somnolence, fatigue, psychomotor slowing, and concentration problems. The currently recommended dosing is lower and titration slower than schedules used in the clinical trials; this may improve the tolerability of topiramate. Topiramate has few interactions with currently available AEDs, but phenytoin concentrations increased in some patients. Topiramate can be used initially as adjunctive therapy. Plasma topiramate concentrations are reduced substantially when used with enzyme-inducing AEDs. Open-label data and a single double-blind trial suggest that topiramate monotherapy may be effective. Open-label data also indicate that topiramate may be effective in generalized seizures of nonfocal origin, including those associated with Lennox-Gastaut syndrome.

CONCLUSIONS

The robust clinical effects of topiramate expand the therapeutic options for patients with epilepsy. Controlled clinical trials are needed to verify initial observations that topiramate may be effective against a broad spectrum of seizure types and to directly compare efficacy and tolerability with other new and standard AEDs.

Recent advances in the pharmacotherapy of epilepsy

The therapeutic options for the treatment of epilepsy have expanded during the 1990s. Since 1993, four novel agents (felbamate, gabapentin, lamotrigine, and topiramate) have been approved by the US Food and Drug Administration, primarily for adjunctive treatment of partial seizures. In addition, a water-soluble pro-drug of phenytoin, fosphenytoin, and a sustained-release preparation of carbamazepine have been introduced. The novel anticonvulsants represent a potential improvement for patients whose seizures are incompletely controlled or who experience significant adverse effects with older anticonvulsants. Felbamate, lamotrigine, and topiramate appear to have a broad spectrum of action in seizure control, but felbamate use is limited by the potential for serious adverse effects. Gabapentin, lamotrigine, and topiramate are all well tolerated. Gabapentin has no known drug interactions, whereas lamotrigine and topiramate have limited interactions compared with older agents. The sustained-release preparation of carbamazepine may decrease the incidence of adverse effects and increase patient compliance. Fosphenytoin offers a safer method for intravenous administration of phenytoin and the added flexibility of intramuscular administration. Taken together, these recent advances in treatment may bring about improved efficacy and decreased adverse effects for many patients with epilepsy.

Effect of topiramate on the pharmacokinetics of an oral contraceptive containing norethindrone and ethinyl estradiol in patients with epilepsy

PURPOSE

Because enzyme-inducing antiepileptic drugs (AEDs) can affect pharmacokinetics of oral contraceptives and thereby cause contraceptive failure, the potential effect of topiramate, a new AED, on the pharmacokinetics of the combination oral contraceptive norethindrone/ethinyl estradiol was evaluated.

METHODS

Twelve women receiving stable valproic acid (VPA) monotherapy for epilepsy received a combination norethindrone 1.0 mg/ethinyl estradiol 35-microg tablet daily for 21 days followed by seven daily doses of inert tablets for four 28-day cycles. After a baseline cycle (cycle 1), topiramate 100, 200, and 400 mg every 12 h was administered in cycles 2 through 4, respectively. Serial blood samples were obtained on day 20 of each cycle and were analyzed for norethindrone, ethinyl estradiol, and progesterone by using validated radioimmunoassay methods.

RESULTS

Compared with cycle 1, none of the norethindrone pharmacokinetic parameters changed significantly in the presence of topiramate, 100-400 mg every 12 h. Individual patient serum progesterone concentrations measured during each cycle were at or close to the limit of quantification with no apparent differences among cycles. However, mean area under the concentration-versus-time curve over the 24-h period (AUC(0-24)) values for ethinyl estradiol were 18-30% lower in cycles 2 through 4 compared with cycle 1 (p < or = 0.05 for all pairs), whereas mean oral serum clearance (CL/F) values were 14.7-33.0% higher (p < or = 0.05 for cycles 2 and 4 vs. cycle 1). Mean time of peak concentration (T(max)) values determined during topiramate therapy were not significantly different from those at baseline.

CONCLUSIONS

When prescribing an oral contraceptive for patients receiving topiramate, clinicians should consider initial therapy with an agent containing > or = 35 microg of ethinyl estradiol.

Comparison of the steady-state pharmacokinetics of topiramate and valproate in patients with epilepsy during monotherapy and concomitant therapy

PURPOSE

The steady-state pharmacokinetics of valproate (VPA) and topiramate (TPM) were compared during VPA monotherapy, concomitant VPA and TPM therapy, and TPM monotherapy to evaluate pharmacokinetic interactions.

METHODS

After a 3-week baseline period, 12 patients receiving VPA monotherapy (500 to 2,250 mg every 12 h) received TPM at three escalating doses (from 100 to 200 to 400 mg every 12 h), each for 2 weeks. Thereafter, the VPA dose was tapered by 25% weekly. Blood and urine samples were collected over 12-h intervals during VPA monotherapy and at the end of each stage of TPM dose escalation and TPM monotherapy.

RESULTS

All patients reached TPM monotherapy, and nine achieved satisfactory seizure control for > or = 2 weeks without VPA. TPM plasma peak concentration (C(max)) and area under the concentration-versus-time curve during a 12-h dosing interval (AUC(0-12)) were slightly higher (17%; n = 8) during TPM monotherapy than during concomitant VPA therapy. TPM oral and renal clearances (n = 8) were 25.9 +/- 4.6 and 11.6 +/- 3.2 ml/min during TPM monotherapy and were 29.8 +/- 4.2 and 12.4 +/- 2.7 ml/min during VPA concomitant therapy. VPA AUC(0-12) decreased (11.3%; n = 10) with the addition of TPM 400 mg every 12 h. VPA oral clearance was 12.8 +/- 4.1 ml/min during monotherapy and was 13.8 +/- 4.0, 14.1 +/- 3.9, and 14.5 +/- 5.2 ml/min during coadministration of TPM 100, 200, and 400 mg every 12 h, respectively. Cognitive dysfunction, observed in some patients receiving high doses of VPA with TPM, reversed or improved with VPA dose reduction and discontinuation. The lower-than-normal prestudy platelet count measured in one patient increased to normal levels when VPA was discontinued.

CONCLUSIONS

Because changes in TPM and VPA pharmacokinetics were small, it is unlikely that their concomitant use will have a significant impact on the clinical condition of the patient.

Acute and chronic effects of hypoxia on the developing hippocampus

Perinatal hypoxia is associated with both seizures arising acutely and the subsequent development of temporal lobe epilepsy (as determined retrospectively). We therefore attempted to identify acute and chronic morphological and/or electrophysiological hippocampal pathologies associated with experimentally induced hypoxia in immature rats. Pups were exposed to 15 minutes of hypoxia on 3 successive days (starting on postnatal day 8; P8), or to 60 minutes of hypoxia on P10 with either one or multiple hypoxia-induced seizures. For animals experiencing multiple seizures, flurothyl seizure threshold was significantly lower than that of controls at 60 to 80 days, but not at 10 days, after hypoxia. Acutely, there was a treatment-related increase in the number and the density of pyknotic dentate and hilar neurons, in particular in animals experiencing multiple seizures. However, 60 to 80 days after the multiple-seizure protocol, the number of dentate and hilar neurons did not differ between control and experimental animals. Electrophysiological measures of pyramidal cell properties showed no striking difference between experimental and control animals at any time point. These results indicate that early postnatal hypoxia and hypoxia-induced seizure episodes decrease seizure threshold in the adult but produce minimal acute or chronic morphological or functional changes in the hippocampus.

Pharmacokinetics and interaction profile of topiramate: review and comparison with other newer antiepileptic drugs

Standard antiepileptic drugs (AEDs) have a number of pharmacokinetic shortcomings, and AEDs with more favorable profiles would be preferred. The pharmacokinetics and interaction profile of the recently developed AED topiramate (TPM), is reviewed and compared with those of other newer AEDs including lamotrigine (LTG), gabapentin (GBP), vigabatrin (VGB), and oxcarbazepine (OCBZ). Although none of these agents meets all of the criteria of the "ideal" AED from the pharmacokinetic standpoint, a number of these drugs, including TPM, have desirable properties that distinguish them from the older AEDs and should contribute to their clinical utility.

Overview of the safety of newer antiepileptic drugs

Standard antiepileptic drugs (AEDs) are associated with a wide variety of acute and chronic adverse events and with many interactions with each other and with non-AEDs that complicate patient management. The safety and interaction profiles of the newer AEDs have also been intensively studied. Safety data are available for six of the newer AEDs, lamotrigine (LTG), vigabatrin (VGB), gabapentin (GBP), tiagabine (TGB), felbamate (FBM), and topiramate (TPM). The potential for the most recently developed AEDs for producing rare idiosyncratic reactions cannot be ascertained until additional patient exposures have been reported from careful postmarketing surveillance.

Lamotrigine adjunctive therapy in childhood epileptic encephalopathy (the Lennox Gastaut syndrome)

PURPOSE

We assessed efficacy and safety of adjunctive lamotrigine (LTG) therapy in patients with the Lennox-Gastaut syndrome (LGS).

METHODS

The study was a single-center, retrospective chart review of open-label adjunctive LTG therapy in patients with LGS. Initial LTG dose and titration was dependent on concomitant antiepileptic drugs (AEDs). Efficacy was based on the change in seizure frequency between the initiation of LTG therapy and December 1, 1995 (or LTG discontinuation). Seizure diaries were used to count patient seizures. A secondary evaluation of efficacy was a parental or guardian assessment of the patient's global status. The evaluation of safety involved chart review for treatment-emergent adverse events (AE).

RESULTS

Data from 16 LGS patients were analyzed. Fifty-three percent (8 of 15) had a > 50% reduction in seizure frequency with LTG adjunctive therapy. Tonic, atonic, generalized tonic-clonic (GTCS), and atypical absence seizure frequency but not myoclonic seizure frequency decreased significantly during LTG therapy. Fifty-three percent of the patient's parents (8 of 15) reported that their child's quality of life (QOL) was much or very much improved during the study. The major treatment-emergent AE were infection (50%, 8 of 16) and sleep disturbance (19%, 3 of 16). A rash was noted in 13% (2 of 16) of the patients and resulted in LTG discontinuation in 1. No clinically significant changes were noted in neurologic examination or laboratory tests during the study.

CONCLUSIONS

Our results indicate that LTG adjunctive therapy is effective and well tolerated in patients with LGS.

Pharmacokinetics of new antiepileptic drugs

This article surveys the pharmacokinetic parameters for the new antiepileptic drugs (AEDs): felbamate, gabapentin, lamotrigine, oxcarbazepine, tiagabine, topiramate, and vigabatrin. Compared to the pharmacokinetics of standard AEDs, these new AEDs have progressed in terms of (a) longer half-lives, permitting once- or twice-daily dosing, (b) greatly reduced potential for drug interactions, thus increasing ease of treatment, and (c) general lack of hepatic enzyme induction, which facilitates polytherapy as well as other aspects of treatment.

Progress report on new antiepileptic drugs: a summary of the Third Eilat Conference

The Third Eilat Conference on New Antiepileptic Drugs was held at the Royal Beach Hotel from May 27 to May 30, 1996. Epileptologists and scientists from 20 countries attended the conference, which was held to discuss critical issues in drug development, new antiepileptic drugs (AEDs) in development, progress reports and recent findings of newly marketed AEDs, the use of AEDs in special populations and their utilization in non-epileptic disorders. Over the last seven years, six new AEDs have been introduced worldwide and new information on their safety and efficacy has become available. These include felbamate, gabapentin, lamotrigine, oxcarbazepine, topiramate and vigabatrin. Drugs in development include those at an advanced stage, such as remacemide and tiagabine, as well as those just entering clinical trials, such as rufinamide (CGP 331010) and levetiracetam (ucb LO59). The following is a summary of the presentations for drugs in development and recent findings on newly marketed drugs.

Pharmacokinetic profile of topiramate in comparison with other new antiepileptic drugs

Antiepileptic drugs (AEDs) in broad use today have a number of pharmacokinetic liabilities, including a propensity for clinically meaningful drug interactions. Therefore, new AEDs with improved pharmacokinetic characteristics would be welcomed. The pharmacokinetic profiles of six newer AEDs--topiramate (TPM), gabapentin (GBP), vigabatrin (VGB), lamotrigine (LTG), oxcarbazepine (OCBZ), and felbamate--were reviewed. Some of these AEDs offer an improvement in one or more pharmacokinetic parameters compared with traditional AEDs, with TPM, GBP, VGB, and OCBZ demonstrating the most advantageous overall pharmacokinetic profiles.

Double-blind, placebo-controlled trial of topiramate (600 mg daily) for the treatment of refractory partial epilepsy

PURPOSE

We wished to evaluate adjunctive therapy for partial-onset seizures with topiramate (TPM) for efficacy and safety in a double-blind, placebo-controlled, randomized, parallel-group study.

METHODS

Sixty outpatients with epilepsy (47 men and 13 women, mean age 32.9 years) were studied. All had a documented history of partial-onset seizures with or without secondarily generalized seizures. After an 8-week baseline during which patients had at least one seizure per week, 30 patients each were randomized to TPM 300 mg twice daily (b.i.d.) or placebo for 12 weeks.

RESULTS

TPM was significantly superior to placebo, as indicated by all efficacy assessments: greater median percent reduction from baseline in the average monthly seizure rate (46 vs. -12%, p = 0.004); greater number of treatment responders (patients with > or = 50% reduction in seizure rate) (47 vs. 10%, p = 0.001), and better investigator (p = 0.002) and patient (p = 0.010) global assessments of treatment. Among TPM-treated patients, the most commonly reported adverse events (AE) were headache, somnolence, fatigue, dizziness, and abnormal thinking. Most AE were mild or moderate in severity.

CONCLUSIONS

The results of the present trial indicate that TPM 600 mg/day is effective in the treatment of refractory partial-onset seizures with or without secondarily generalized seizures.