Selection of antiepileptic drug polytherapy based on mechanisms of action: the evidence reviewed

Carbamazepine toxicity with concomitant levetiracetam therapy in patients with epilepsy

AIM

Drug interactions are crucial in understanding the efficacy and safety of co-administered antiepileptic drugs. This study aims to investigate drug interactions between carbamazepine (CBZ) and levetiracetam (LEV) and the factors associated with CBZ toxicity.

METHODS

The present record-based case-control study analyzed data from 158 patients. A univariate analysis was done to identify the association of various factors with toxic trough CBZ concentrations. Frequentist disproportionality analysis was done to determine a signal for the association between concomitant LEV administration and CBZ toxicity. Receiver operating characteristic (ROC) analysis was done to identify the LEV:CBZ dose ratio to differentiate between toxic and non-toxic CBZ concentrations.

RESULTS

The odds of developing manifestations of CBZ toxicity in CBZ + LEV versus CBZ group were 16.65 (95% confidence interval [CI]: 3.52-78.70; p < 0.001). The univariate analysis showed no association between CBZ dose and toxic trough CBZ levels, while an association between LEV administration and toxic trough CBZ levels was evident. A reporting odds ratio (ROR) of 2.25 (95% CI: 1.07-4.72; p = 0.030) and proportional reporting ratio (PRR) of 1.77(95% CI: 1.07-2.94) was observed for toxic levels of CBZ with co-administration of LEV.

A LEV

CBZ dose ratio of 1.86 was identified as a threshold for differentiating between toxic and non-toxic serum concentrations with an accuracy of 72.9%.

CONCLUSIONS

There is a temporal association between LEV administration and toxic blood levels and toxic symptoms of CBZ, the chances of which significantly higher when the dose ratio of LEV:CBZ is 1.86.

Pharmacotherapeutic strategies for drug-resistant epilepsy in children

Drug resistance is defined as the failure of adequate trials of two tolerated and appropriately chosen antiseizure medications to achieve sustained seizure freedom. In case of uncontrolled seizures, pseudo-drug-resistance (poor compliance, a worsening effect of an antiseizure medication, a diagnosis of psychogenic non-epileptic seizure) should be first ruled out in case of pediatric epilepsies. This paper discusses the process of choosing antiseizure medication and the concepts of rationale polytherapy and precision medicine. In drug-resistant epilepsy, when curative surgery is not feasible, the aim of the treatment is focused on the improvement of quality of life rather than on seizure count. In recent years, despite an increase in available antiseizure medications, the incidence of drug-resistant epilepsy has not changed. Precision medicine may offer in rare epilepsies a mechanism-driven treatment, but it is still unclear if this will end up in an improvement of efficacy in drug-resistant epilepsies. Gene therapy with antisense oligonucleotides or Adeno-associated Virus (AAV) is transitioning from the experimental side to the first human trial. It may modify the natural history of selected epileptic syndromes.

Brivaracetam use in clinical practice: a Delphi consensus on its role as first add-on therapy in focal epilepsy and beyond

BACKGROUND

Antiseizure medications remain the cornerstone of treatment for epilepsy, although a proportion of individuals with the condition will continue to experience seizures despite appropriate therapy. Treatment choices for epilepsy are based on variables related to both the individual patient and the available medications. Brivaracetam is a third-generation agent antiseizure medication.

METHODS

We carried out a Delphi consensus exercise to define the role of brivaracetam in clinical practice and to provide guidance about its use as first add-on ASM and in selected clinical scenarios. A total of 15 consensus statements were drafted by an expert panel following review of the literature and all were approved in the first round of voting by panelists. The consensus indicated different clinical scenarios for which brivaracetam can be a good candidate for treatment, including first add-on use.

RESULTS

Overall, brivaracetam was considered to have many advantageous characteristics that render it a suitable option for patients with focal epilepsy, including a fast onset of action, favorable pharmacokinetic profile with few drug-drug interactions, broad-spectrum activity, and being well tolerated across a range of doses. Brivaracetam is also associated with sustained clinical response and good tolerability in the long term.

CONCLUSIONS

These characteristics also make it suitable as an early add-on for the elderly and for patients with post-stroke epilepsy or status epilepticus as highlighted by the present Delphi consensus.

Presynaptic antiseizure medications - basic mechanisms and clues for their rational combinations

Among clinically highly efficient antiseizure medications (ASMs) there are modifiers of the presynaptic release machinery. Of them, levetiracetam and brivaracetam show a high affinity to the synaptic vesicle protein type 2 A (SV2A), whereas pregabalin and gabapentin are selective ligands for the α2δ1 subunits of the voltage-gated calcium channels. In this paper, we present recent progress in understanding the significance of presynaptic release machinery in the neurochemical mechanisms of epilepsy and ASMs. Furthermore, we discuss whether the knowledge of the basic mechanisms of the presynaptically acting ASMs might help establish a rational polytherapy for drug-resistant epilepsy.

Current challenges in focal epilepsy treatment: An Italian Delphi consensus

BACKGROUND

Epilepsy, a globally prevalent neurological condition, presents distinct challenges in management, particularly for focal-onset types. This study aimed at addressing the current challenges and perspectives in focal epilepsy management, with focus on the Italian reality.

METHODS

Using the Delphi methodology, this research collected and analyzed the level of consensus of a panel of Italian epilepsy experts on key aspects of focal epilepsy care. Areas of focus included patient flow, treatment pathways, controlled versus uncontrolled epilepsy, follow-up protocols, and the relevance of patient-reported outcomes (PROs). This method allowed for a comprehensive assessment of consensus and divergences in clinical opinions and practices.

RESULTS

The study achieved consensus on 23 out of 26 statements, with three items failing to reach a consensus. There was strong agreement on the importance of timely intervention, individualized treatment plans, regular follow-ups at Epilepsy Centers, and the role of PROs in clinical practice. In cases of uncontrolled focal epilepsy, there was a clear inclination to pursue alternative treatment options following the failure of two previous therapies. Divergent views were evident on the inclusion of epilepsy surgery in treatment for uncontrolled epilepsy and the routine necessity of EEG evaluations in follow-ups. Other key findings included concerns about the lack of pediatric-specific research limiting current therapeutic options in this patient population, insufficient attention to the transition from pediatric to adult care, and need for improved communication. The results highlighted the complexities in managing epilepsy, with broad consensus on patient care aspects, yet notable divergences in specific treatment and management approaches.

CONCLUSION

The study offered valuable insights into the current state and complexities of managing focal-onset epilepsy. It highlighted many deficiencies in the therapeutic pathway of focal-onset epilepsy in the Italian reality, while it also underscored the importance of patient-centric care, the necessity of early and appropriate intervention, and individualized treatment approaches. The findings also called for continued research, policy development, and healthcare system improvements to enhance epilepsy management, highlighting the ongoing need for tailored healthcare solutions in this evolving field.

A profile of azetukalner for the treatment of epilepsy: from pharmacology to potential for therapy

INTRODUCTION

Epilepsies are a group of heterogeneous brain disorder, and antiseizure medications (ASMs) are the mainstay of treatment. Despite the availability of more than 30 drugs, at least one third of individuals with epilepsy are drug-resistant. This emphasizes the need for novel compounds that combine efficacy with improved tolerability.

AREAS COVERED

A literature review on the pharmacology, efficacy, tolerability, and safety of azetukalner (XEN1101), a second-generation opener of neuronal potassium channels currently in Phase 3 development as ASM.

EXPERT OPINION

Results from the phase 2b clinical trial strongly support the ongoing clinical development of azetukalner as a new ASM. Its pharmacokinetic properties support convenient once-daily dosing, eliminating the need for titration at initiation or tapering at the conclusion of treatment. CYP3A4 is the main enzyme involved in its metabolism and drug-drug interactions can affect the drug exposure. Preliminary analysis of an ongoing open-label study reveals no reported pigmentary abnormalities. The upcoming Phase 3 clinical trials are expected to provide further insight into the efficacy, tolerability, and safety of azetukalner in treating focal-onset and primary generalized tonic-clonic seizures. Structurally distinct from currently marketed ASMs, azetukalner has the potential to be the only-in-class Kv7.2/7.3 opener on the market upon regulatory approval.

Optimizing treatment persistence in epilepsy: a comparative analysis of combined antiseizure medications with different mechanisms of action

Background

Combination therapy with antiseizure medications (ASMs) is a rational strategy if monotherapy cannot effectively control seizures, thereby aiming to improve tolerance and treatment persistence.

Objectives

To compare the efficacy of different ASM combinations among patients.

Design

Patients with epilepsy on monotherapy who had a second ASM added as concomitant two-drug therapy from January 2009 to May 2019 in the Chang Gung Research Database, Taiwan, were included in the analysis.

Methods

ASM combinations were compared based on their primary mechanism of action (MoA) which are as follows: gamma-aminobutyric acid receptor (G), sodium channel blocker (SC), synaptic vesicle protein 2A (SV2), calcium channel blocker (C), and multiple mechanisms (M). Treatment persistence was compared, and the predictors of persistence were analyzed.

Results

In total, 3033 patients were enrolled in this study. Combined ASMs with different MoAs had significantly longer treatment persistence than ASMs with similar MoAs, specifically SC and M combinations. Patients receiving combined ASMs with different MoAs were less likely to discontinue treatment [adjusted hazards ratio: 0.83 (95% CI: 0.75-0.93), p < 0.001]. Among all combinations, the SC + SV2 combination had the longest treatment persistence (mean ± SD: 912.7 ± 841.6 days). Meanwhile, patients receiving the G combination had a higher risk of treatment discontinuation than those receiving the SC + SV2 combination. Underlying malignancies were associated with an increased risk of treatment discontinuation across all MoA categories. Male patients receiving the SC, SV2, and M combinations were more likely to discontinue treatment than female patients. Moreover, patients with renal disease were more likely to discontinue treatment with the SV2 combinations.

Conclusion

ASM combinations with different MoAs had superior efficacy and tolerability to ASM combinations with similar MoAs, particularly SC and M combinations. In our cohort, factors associated with treatment discontinuation included underlying malignancy, male sex, and renal disease. These findings may provide valuable insights into the use of ASM combinations if monotherapy cannot adequately control seizures.

Animal Models of Drug-Resistant Epilepsy as Tools for Deciphering the Cellular and Molecular Mechanisms of Pharmacoresistance and Discovering More Effective Treatments

In the last 30 years, over 20 new anti-seizure medicines (ASMs) have been introduced into the market for the treatment of epilepsy using well-established preclinical seizure and epilepsy models. Despite this success, approximately 20-30% of patients with epilepsy have drug-resistant epilepsy (DRE). The current approach to ASM discovery for DRE relies largely on drug testing in various preclinical model systems that display varying degrees of ASM drug resistance. In recent years, attempts have been made to include more etiologically relevant models in the preclinical evaluation of a new investigational drug. Such models have played an important role in advancing a greater understanding of DRE at a mechanistic level and for hypothesis testing as new experimental evidence becomes available. This review provides a critical discussion of the pharmacology of models of adult focal epilepsy that allow for the selection of ASM responders and nonresponders and those models that display a pharmacoresistance per se to two or more ASMs. In addition, the pharmacology of animal models of major genetic epilepsies is discussed. Importantly, in addition to testing chemical compounds, several of the models discussed here can be used to evaluate other potential therapies for epilepsy such as neurostimulation, dietary treatments, gene therapy, or cell transplantation. This review also discusses the challenges associated with identifying novel therapies in the absence of a greater understanding of the mechanisms that contribute to DRE. Finally, this review discusses the lessons learned from the profile of the recently approved highly efficacious and broad-spectrum ASM cenobamate.

Beneficial Effects of Statins on Seizures Independent of Their Lipid-Lowering Effect: A Narrative Review

Among the many types of central nervous system (CNS) disorders, seizures and epilepsy severely affect the quality of life and routine daily activity of the sufferers. We aimed to review research studies that investigated the effect of statins on the prevention and treatment of seizures and epilepsy. Both animal models and human studies were included in this review. This article starts with a brief introduction about seizure, its prevalence, treatment, and various animal models of seizures and epilepsy. Next, we discuss statin's mechanism of action, side effects, and effects on neurological disorders with a specific focus on seizures. Finally, the effects of different types of statins on seizures are compared. The present review gives a better understanding of the therapeutic effects of statins on neurological disorders in animal models and human studies. This permits researchers to set up study designs to resolve current ambiguities and contradictions on the beneficial effects of statins on neurological disorders.

Ranolazine Interacts Antagonistically with Some Classical Antiepileptic Drugs-An Isobolographic Analysis

Ranolazine, an antianginal and antiarrhythmic drug blocking slow inactivating persistent sodium currents, is described as a compound with anticonvulsant potential. Since arrhythmia often accompanies seizures, patients suffering from epilepsy are frequently co-treated with antiepileptic and antiarrhythmic drugs. The aim of this study was to evaluate the effect of ranolazine on maximal-electroshock (MES)-induced seizures in mice as well as interactions between ranolazine and classical antiepileptic drugs in this model of epilepsy. Types of pharmacodynamic interactions were established by isobolographic analysis of obtained data. The main findings of the study were that ranolazine behaves like an antiseizure drug in the MES test. Moreover, ranolazine interacted antagonistically with carbamazepine, phenytoin, and phenobarbital in the proportions of 1:3 and 1:1. These interactions occurred pharmacodynamic, since ranolazine did not change the brain levels of antiepileptic drugs measured in the fluorescence polarization immunoassay. Ranolazine and its combinations with carbamazepine, phenytoin, and phenobarbital did not impair motor coordination evaluated in the chimney test. Unfortunately, an attempt to conduct a passive avoidance task (evaluating long-term memory) resulted in ranolazine-induced delayed lethality. In conclusion, ranolazine exhibits clear-cut anticonvulsant properties in the MES test but interacts antagonistically with some antiepileptic drugs. The obtained results need confirmation in clinical studies. The mechanisms of ranolazine-induced toxicity require specific explanation.

Effects of Antiarrhythmic Drugs on Antiepileptic Drug Action-A Critical Review of Experimental Findings

Severe cardiac arrhythmias developing in the course of seizures increase the risk of SUDEP (sudden unexpected death in epilepsy). Hence, epilepsy patients with pre-existing arrhythmias should receive appropriate pharmacotherapy. Concomitant treatment with antiarrhythmic and antiseizure medications creates, however, the possibility of drug–drug interactions. This is due, among other reasons, to a similar mechanism of action. Both groups of drugs inhibit the conduction of electrical impulses in excitable tissues. The aim of this review was the analysis of such interactions in animal seizure models, including the maximal electroshock (MES) test in mice, a widely accepted screening test for antiepileptic drugs.

Emerging therapeutic targets for epilepsy: Preclinical insights

INTRODUCTION

Around 30% of patients with epilepsy suffer from drug-resistant seizures. Drug-resistant seizures may have significant consequences such as sudden death in epilepsy, injuries, memory disturbances, and childhood learning and developmental problems. Conventional and newer available antiepileptic drugs (AEDs) work via numerous mechanisms - mainly through inhibition of voltage-operated Na⁺ and/or Ca²⁺ channels, excitation of K⁺ channels, enhancement of GABA-mediated inhibition and/or blockade of glutamate-produced excitation. However, the discovery and development of novel brain targets may improve the future pharmacological management of epilepsy and hence is of pivotal importance.

AREAS COVERED

This article examines novel drug targets such as brain multidrug efflux transporters and inflammatory pathways; it progresses to discuss possible strategies for the management of drug-resistant seizures. Reduction of the consequences of blood brain barrier dysfunction and enhancement of anti-oxidative defense are discussed.

EXPERT OPINION

Novel drug targets comprise brain multidrug efflux transporters, TGF-β, Nrf2-ARE or m-TOR signaling and inflammatory pathways. Gene therapy and antagomirs seem the most promising targets. Epileptic foci may be significantly suppressed by viral-vector-mediated gene transfer, leading to an increased in situ concentration of inhibitory factors (for instance, galanin). Also, antagomirs offer a promising possibility of seizure inhibition by silencing micro-RNAs involved in epileptogenesis and possibly in seizure generation.

Single-Target Versus Multi-Target Drugs Versus Combinations of Drugs With Multiple Targets: Preclinical and Clinical Evidence for the Treatment or Prevention of Epilepsy

Rationally designed multi-target drugs (also termed multimodal drugs, network therapeutics, or designed multiple ligands) have emerged as an attractive drug discovery paradigm in the last 10-20 years, as potential therapeutic solutions for diseases of complex etiology and diseases with significant drug-resistance problems. Such agents that modulate multiple targets simultaneously are developed with the aim of enhancing efficacy or improving safety relative to drugs that address only a single target or to combinations of single-target drugs. Although this strategy has been proposed for epilepsy therapy >25 years ago, to my knowledge, only one antiseizure medication (ASM), padsevonil, has been intentionally developed as a single molecular entity that could target two different mechanisms. This novel drug exhibited promising effects in numerous preclinical models of difficult-to-treat seizures. However, in a recent randomized placebo-controlled phase IIb add-on trial in treatment-resistant focal epilepsy patients, padsevonil did not separate from placebo in its primary endpoints. At about the same time, a novel ASM, cenobamate, exhibited efficacy in several randomized controlled trials in such patients that far surpassed the efficacy of any other of the newer ASMs. Yet, cenobamate was discovered purely by phenotype-based screening and its presumed dual mechanism of action was only described recently. In this review, I will survey the efficacy of single-target vs. multi-target drugs vs. combinations of drugs with multiple targets in the treatment and prevention of epilepsy. Most clinically approved ASMs already act at multiple targets, but it will be important to identify and validate new target combinations that are more effective in drug-resistant epilepsy and eventually may prevent the development or progression of epilepsy.

Perampanel as first add-on antiseizure medication: Italian consensus clinical practice statements

Background

When use of a single antiseizure medication (ASM) fails to induce seizure remission, add-on therapy is justified. Perampanel (PER) is approved in Europe as adjunctive therapy for focal, focal to bilateral tonic-clonic seizures and generalized tonic-clonic seizures. Aim of the study was to establish whether PER is suitable for first add-on use.

Methods

A Delphi methodology was adopted to assess consensus on a list of 39 statements produced by an Expert Board of 5 epileptologists. Using an iterative process, statements were finalized by a Delphi Panel of 84 Italian pediatric and adult neurologists. Each statement was rated anonymously to determine level of agreement on a 9-point Likert scale. Consensus was established as agreement by at least 80% of the panelists. The relevance of each statement was also assessed on a 3-point scale.

Results

Consensus was achieved for 37 statements. Characteristics of PER considered to justify its use as first add-on include evidence of a positive impact on quality of life based on long term retention data, efficacy, tolerability, and ease of use; no worsening of cognitive functions and sleep quality; a low potential for drug interactions; a unique mechanism of action. Potential unfavorable factors are the need for a relatively slow dose titration; the potential occurrence of behavioral adverse effects; lack of information on safety when used in pregnancy; limited access to plasma PER levels.

Conclusion

Perampanel has many features which justify its use as a first add-on. Choice of an ASM as first add-on should be tailored to individual characteristics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02450-y.

Selection of antiseizure medications for first add-on use: A consensus paper

INTRODUCTION

When monotherapy used alone or sequentially fails to achieve seizure control, a trial of combination therapy may be considered.

OBJECTIVE

To define optimal criteria to guide choice of an antiseizure medication (ASM) for use as first add-on.

METHODS

A standardized Delphi procedure was applied to produce a list of consensus statements. First, an Expert Board consisting of 5 epileptologists agreed on a set of 46 statements relevant to the objective. The statements were then finalized through an iterative process by a Delphi Panel of 84 Italian pediatric and adult neurologists with expertise in the management of epilepsy. Panel members provided anonymous ratings of their level of agreement with each statement on a 9-point Likert scale.

RESULTS

Consensus, defined as agreement by at least 80% of Panel members, was reached for 36 statements. Medication-related factors considered to be important for drug selection included efficacy, tolerability and safety, interaction potential, mechanism of action, and ease of use. The need to optimize adherence and to tailor drug selection to individual characteristics was emphasized.

CONCLUSIONS

Choice of an ASM for first add-on requires consideration of many factors, many of which also apply to choose initial treatment. Factors more specifically relevant to add-on use include drug interaction potential and the preference for an ASM with a different mechanism of action.

Effective treatments for FGF12-related early-onset epileptic encephalopathies patients

BACKGROUND

FGF12 (FHF1) gene encodes voltage-gated sodium channel (Nav)-binding protein fibroblast growth factor homologous factor 1, which could cause seizures by regulating voltage dependence of Nav fast inactivation and neuron excitability. The most common pathogenic variant FGF12 c.341G > A related early-onset epileptic encephalopathies (EOEE) was characterized by intractable seizures and developmental disabilities.

RESULTS

Using whole exome sequencing, a de novo hotspot variant c.341G > A (NM_021032.4) of FGF12 was identified in three unrelated EOEE probands. All probands were seizure free after a combination treatment of valproic acid (VPA) and topiramate (TPM). The motor and cognitive skills in two probands were improved due to the early and effective treatment. In order to compare the effectiveness of different treatment strategies for the disease, a review of treatments for FGF12-related epilepsy was made.

CONCLUSION

We reported three FGF12 c.341G > A related EOEE patients responded well to a combination antiepileptic therapy of VPA and TPM. The current study is the first to describe the combination therapy of VPA and TPM in FGF12 c.341G > A related EOEE patients. This study may contribute to future medication consultation for intractable epilepsy with FGF12 hotspot variants.

Understanding mechanisms of drug resistance in epilepsy and strategies for overcoming it

INTRODUCTION

The present evidence indicates that approximately 70% of patients with epilepsy can be successfully treated with antiepileptic drugs (AEDs). A significant proportion of patients are not under sufficient control, and pharmacoresistant epilepsy is clearly associated with poor quality of life and increased morbidity and mortality. There is a great need for newer therapeutic options able to reduce the percentage of drug-resistant patients.

AREAS COVERED

A number of hypotheses trying to explain the development of pharmacoresistance have been put forward. These include: target hypothesis (altered AED targets), transporter (overexpression of brain efflux transporters), pharmacokinetic (overexpression of peripheral efflux transporters in the intestine or kidneys), intrinsic severity (initial high seizure frequency), neural network (aberrant networks), and gene variant hypothesis (genetic polymorphisms).

EXPERT OPINION

A continuous search for newer AEDs or among non-AEDs (blockers of efflux transporters, interleukin antagonists, cyclooxygenase inhibitors, mTOR inhibitors, angiotensin II receptor antagonists) may provide efficacious drugs for the management of drug-resistant epilepsy. Also, combinations of AEDs exerting synergy in preclinical and clinical studies (for instance, lamotrigine + valproate, levetiracetam + valproate, topiramate + carbamazepine) might be of importance in this respect. Preclinically antagonistic combinations must be avoided (lamotrigine + carbamazepine, lamotrigine + oxcarbazepine).

Which treatment strategy in patients with epilepsy with focal seizures uncontrolled by the first anti-seizure medication?

There is no definite proven or accepted strategy in the management of patients with focal epilepsy uncontrolled by the first anti-seizure medication (ASM). Clinical studies failed to find a significant difference in efficacy or tolerability between alternative monotherapy and/or adjunctive therapy in these patients. A second ASM is often added, the efficacy of the combination is assessed, and the dose of the first drug can be gradually reduced and withdrawn. If seizures recur, the effective combination therapy can be reinstated. In this review, we discussed experimental and clinical data about the efficacy and tolerability of the most frequently used combinations of ASMs. Animal studies suggested that the most favorable combinations are those between ASMs with different or multiple mechanisms of action, whereas combining drugs with similar pharmacodynamic properties is often associated with additive or infra-additive efficacy and additive or synergistic toxicity. Clinical studies have shown that levetiracetam (LEV) can be favorably combined with the sodium channel blockers (SCBs) lacosamide (LCM) and lamotrigine (LTG). Lamotrigine is particularly effective when associated with valproate (VPA) and possibly with LEV and topiramate (TPM). Carbamazepine (CBZ) has negative pharmacokinetic interactions with several ASMs and should not be combined with other SCBs; it could be effectively and safely combined with gabapentin (GBP) and LEV. Valproic acid has enzyme inhibiting properties and can be cautiously used with SCBs; its combination with TPM or zonisamide (ZNS) may be associated with higher toxicity.

Survey on Antiepileptic Drug Therapy in Patients with Drug Resistant Epilepsy

Background and Purpose

Individualized anti-epileptic drug (AED) selection in patient with epilepsy is crucial. However, there is no unified opinion in treating patients with drug resistant epilepsy (DRE). This survey aimed to make a consolidate consensus with epileptologists’ perspectives of the treatment for Korean DRE patients by survey responses.

Methods

The survey was conducted with Korean epilepsy experts who have experience prescribing AEDs via e-mail. Survey questionnaires consisted of six items regarding prescription patterns and practical questions in treating patients with DRE in Korea. The research period was from February 2021 to March 2021.

Results

The survey response rate was 83.3% (90/108). Most (77.8%) of the responders are neurologists. The proportion of patients whose seizures were not controlled by the second AED was 26.9%. The proportion of patients who had taken five or more AEDs is 13.9%, and those who are currently taking five or more AEDs are 7.3%, of which 54.5% and 37.9% reported positive effects on additional AED, respectively. The majority (91.1%) of respondents answered that the mechanism of action was the top priority factor when adding AED. Regarding data priority, responders considered that expert opinion should have the top priority, followed by clinical experiences, reimbursement guidelines and clinical evidence. Responders gave 64.9 points (range from 0 to 100) about overall satisfaction on reimbursement system of Health Insurance Review and Assessment Service for AED.

Conclusions

This study on AED therapy for DRE patients is the first nationwide trial in Korean epilepsy experts. In five drug failure, the top priorities on AED selection are mechanism of action and expert opinion. These findings might help to achieve consensus and recognize the insight on optimal therapy of AED in DRE.

Interactions among Lacosamide and Second-Generation Antiepileptic Drugs in the Tonic-Clonic Seizure Model in Mice

Combination therapy with two or three antiseizure medications (ASMs) is sometimes a preferred method of treatment in epilepsy patients. (1) Background: To detect the most beneficial combination among three ASMs, a screen test evaluating in vivo interactions with respect to their anticonvulsant properties, was conducted on albino Swiss mice; (2) Methods: Classification of interactions among lacosamide (LCM) and selected second-generation ASMs (lamotrigine (LTG), pregabalin (PGB), oxcarbazepine (OXC), and topiramate (TPM)) was based on the isobolographic analysis in the mouse maximal electroshock-induced seizure (MES) model. Interactions among LCM and second-generation ASMs were visualized using a polygonogram; (3) Results: In the mouse MES model, synergy was observed for the combinations of LCM + TPM + PGB and LCM + OXC + PGB. Additivity was reported for the other combinations tested i.e., LCM + LTG + TPM, LCM + LTG + PGB, LCM + LTG + OXC, and LCM + OXC + TPM in this seizure model. No adverse effects associated with triple ASM combinations, containing LCM and second-generation ASMs were observed in mice; (4) Conclusions: The combination of LCM + TPM + PGB was the most beneficial combination among the tested in this study, offering synergistic suppression of tonic-clonic seizures in mice subjected to the MES model. Both the isobolographic analysis and polygonogram method can be recommended for experimental epileptology when classifying interactions among the ASMs.

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.

Adjunctive Brivaracetam in Focal Epilepsy: Real-World Evidence from the BRIVAracetam add-on First Italian netwoRk STudy (BRIVAFIRST)

BACKGROUND

In randomized controlled trials, add-on brivaracetam (BRV) reduced seizure frequency in patients with drug-resistant focal epilepsy. Studies performed in a naturalistic setting are a useful complement to characterize the drug profile.

OBJECTIVE

This multicentre study assessed the effectiveness and tolerability of adjunctive BRV in a large population of patients with focal epilepsy in the context of real-world clinical practice.

METHODS

The BRIVAFIRST (BRIVAracetam add-on First Italian netwoRk STudy) was a retrospective, multicentre study including adult patients prescribed adjunctive BRV. Patients with focal epilepsy and 12-month follow-up were considered. Main outcomes included the rates of seizure-freedom, seizure response (≥ 50% reduction in baseline seizure frequency), and treatment discontinuation. The incidence of adverse events (AEs) was also considered. Analyses by levetiracetam (LEV) status and concomitant use of strong enzyme-inducing antiseizure medications (EiASMs) and sodium channel blockers (SCBs) were performed.

RESULTS

A total of 1029 patients with a median age of 45 years (33-56) was included. At 12 months, 169 (16.4%) patients were seizure-free and 383 (37.2%) were seizure responders. The rate of seizure freedom was 22.3% in LEV-naive patients, 7.1% in patients with prior LEV use and discontinuation due to insufficient efficacy, and 31.2% in patients with prior LEV use and discontinuation due to AEs (p < 0.001); the corresponding values for ≥ 50% seizure frequency reduction were 47.9%, 29.7%, and 42.8% (p < 0.001). There were no statistically significant differences in seizure freedom and seizure response rates by use of strong EiASMs. The rates of seizure freedom (20.0% vs. 16.6%;  p = 0.341) and seizure response (39.7% vs. 26.9%; p = 0.006) were higher in patients receiving SCBs than those not receiving SCBs; 265 (25.8%) patients discontinued BRV. AEs were reported by 30.1% of patients, and were less common in patients treated with BRV and concomitant SCBs than those not treated with SCBs (28.9% vs. 39.8%; p = 0.017).

CONCLUSION

The BRIVAFIRST provided real-world evidence on the effectiveness of BRV in patients with focal epilepsy irrespective of LEV history and concomitant ASMs, and suggested favourable therapeutic combinations.

Developing precision treatments for epilepsy using patient and animal models

Introduction: Phenytoin was the first antiepileptic drug (AED) discovered in an animal model of seizures whose clinical efficacy was subsequently confirmed. This clearly indicated that a search for other AEDs had to consider animal studies.Areas covered: Main seizure tests used for the evaluation of possible anticonvulsive activity of potential anticonvulsants and their predictive values have been reviewed. Procedures used for the estimation of antiepileptogenic effects have been also included.Expert opinion: First-line seizure models comprise maximal electroshock (MES)-, pentylenetetrazol (PTZ)- and kindling-induced convulsions in rodents. The MES test may be considered as a convenient and easy model of generalized tonic-clonic seizures, PTZ test - as a model of generalized myoclonic seizures and to a certain degree - absence seizures. Kindled seizures (for example, from amygdala) may be regarded as a model of focal seizures. Some tests have been suggested for the search of AEDs effective in drug-resistant seizures - for instance, 6 Hz (44 mA) test or intrahippocampal kainate model of mesial temporal lobe epilepsy. There are also recommendations from experimental epileptology on synergistic AED combinations for patients with drug-resistant seizures. The clinical evidence on this issue is scarce and favors a combined treatment with valproate + lamotrigine.

Polygonogram with isobolographic synergy for three-drug combinations of phenobarbital with second-generation antiepileptic drugs in the tonic-clonic seizure model in mice

Background

Combination therapy consisting of two or more antiepileptic drugs (AEDs) is usually prescribed for patients with refractory epilepsy. The drug–drug interactions, which may occur among currently available AEDs, are the principal criterion taken by physicians when prescribing the AED combination to the patients. Unfortunately, the number of possible three-drug combinations tremendously increases along with the clinical approval of novel AEDs.

Aim

To isobolographically characterize three-drug interactions of phenobarbital (PB) with lamotrigine (LTG), oxcarbazepine (OXC), pregabalin (PGB) and topiramate (TPM), the maximal electroshock-induced (MES) seizure model was used in male albino Swiss mice.

Materials and method

The MES-induced seizures in mice were generated by alternating current delivered via auricular electrodes. To classify interactions for 6 various three-drug combinations of AEDs (i.e., PB + TPM + PGB, PB + OXC + TPM, PB + LTG + TPM, PB + OXC + PGB, PB + LTG + PGB and PB + LTG + OXC), the type I isobolographic analysis was used. Total brain concentrations of PB were measured by fluorescent polarization immunoassay technique.

Results

The three-drug mixtures of PB + TPM + PGB, PB + OXC + TPM, PB + LTG + TPM, PB + OXC + PGB, PB + LTG + PGB and PB + LTG + OXC protected the male albino Swiss mice from MES-induced seizures. All the observed interactions in this seizure model were supra-additive (synergistic) (p < 0.001), except for the combination of PB + LTG + OXC, which was additive. It was unable to show the impact of the studied second-generation AEDs on total brain content of PB in mice.

Conclusions

The synergistic interactions among PB and LTG, OXC, PGB and TPM in the mouse MES model are worthy of being transferred to clinical trials, especially for the patients with drug resistant epilepsy, who would benefit these treatment options.

Long-term safety and efficacy of safinamide as add-on therapy in levodopa-treated Japanese patients with Parkinson's disease with wearing-off: Results of an open-label study

INTRODUCTION

Safinamide, a selective, reversible monoamine oxidase B inhibitor with a sodium channel inhibitory effect, improves symptoms in advanced Parkinson's disease (PD). This study aimed to confirm the long-term safety and efficacy of safinamide in Japanese PD patients with wearing-off.

METHODS

Japanese PD patients aged ≥30 years with wearing-off were eligible. The primary efficacy endpoint was change from baseline in the mean daily ON-time without troublesome dyskinesias at 52 weeks of treatment. Other efficacy endpoints included changes from baseline in mean daily OFF-time and unified Parkinson's disease rating scale (UPDRS) and PDQ-39 scores.

RESULTS

In total, 203 patients entered the study, and 142 completed the 52-week treatment. Adverse events (AEs) occurred in 78.3% of patients, with nasopharyngitis (20.7%) and dyskinesias (17.7%) as the most common; serious AEs occurred in 17.2%, causing discontinuation in 10.8%. At Week 52, the mean daily ON-time without troublesome dyskinesias increased from baseline by 1.42 h. Change from baseline in mean daily OFF-time was -1.40 h, and that in the UPDRS Part III score in the ON-phase was -6.20.

CONCLUSIONS

As adjunctive treatment with levodopa, safinamide was safe, well tolerated, and effective in improving ON-time and other PD symptoms at 52 weeks.

Sub-additive (antagonistic) interaction of lacosamide with lamotrigine and valproate in the maximal electroshock-induced seizure model in mice: an isobolographic analysis

BACKGROUND

Launching polytherapy with two or three antiseizure drugs (ASDs) in patients with epilepsy is still problematic. The choice of ASDs to combine them together is usually based on clinicians' experience and it requires knowledge about mechanisms of action of the studied ASDs and their drug-drug interactions, whose nature may be favorable, neutral or unfavorable. To characterize three-drug interaction among lacosamide (LCM), lamotrigine (LTG) and valproate (VPA), the type I isobolographic analysis was used. The antiseizure effects of three-drug combination were analyzed in a model of maximal electroshock-induced seizures (MES) in albino Swiss mice.

MATERIALS AND METHODS

The seizure activity in mice was evoked by alternating current stimulation (25 mA, 500 V, 50 Hz, 0.2 s). Both, the type I isobolographic analysis and the test of parallelism of dose-response effects of the ASDs were used so as to properly classify interaction among three ASDs, administered in a fixed ratio combination of 1:1:1.

RESULTS

The three-drug mixture of LCM, LTG and VPA at the fixed ratio of 1:1:1 protected the experimental mice from MES-induced seizures; however, the reported interaction was sub-additive (antagonistic; p < 0.01) with isobolography.

CONCLUSION

The antagonistic pharmacodynamic interaction among LCM, LTG and VPA in the MES test in mice cannot be transferred to clinical settings and this unfavorable combination should not be recommended for patients with epilepsy.

Polygonogram and isobolographic analysis of interactions between various novel antiepileptic drugs in the 6-Hz corneal stimulation-induced seizure model in mice

Pharmacotherapy with two antiepileptic drugs in combination is usually prescribed to epilepsy patients with refractory seizures. The choice of antiepileptic drugs in combination should be based on synergistic cooperation of the drugs with respect to suppression of seizures. The selection of synergistic interactions between antiepileptic drugs is challenging issue for physicians, especially, if 25 antiepileptic drugs are currently available and approved to treat epilepsy patients. The aim of this study was to determine all possible interactions among 5 second-generation antiepileptic drugs (gabapentin (GBP), lacosamide (LCM), levetiracetam (LEV), pregabalin (PGB) and retigabine (RTG)) in the 6-Hz corneal stimulation-induced seizure model in adult male albino Swiss mice. The anticonvulsant effects of 10 various two-drug combinations of antiepileptic drugs were evaluated with type I isobolographic analysis associated with graphical presentation of polygonogram to visualize the types of interactions. Isobolographic analysis revealed that 7 two-drug combinations of LEV+RTG, LEV+LCM, GBP+RTG, PGB+LEV, GBP+LEV, PGB+RTG, PGB+LCM were synergistic in the 6-Hz corneal stimulation-induced seizure model in mice. The additive interaction was observed for the combinations of GBP+LCM, GBP+PGB, and RTG+LCM in this seizure model in mice. The most beneficial combination, offering the highest level of synergistic suppression of seizures in mice was that of LEV+RTG, whereas the most additive combination that protected the animals from seizures was that reporting additivity for RTG+LCM. The strength of interaction for two-drug combinations can be arranged from the synergistic to the additive, as follows: LEV+RTG > LEV+LCM > GBP+RTG > PGB+LEV > GBP+LEV > PGB+RTG > PGB+LCM > GBP+LCM > GBP+PGB > RTG+LCM.

Anti-Epileptogenic Effects of Antiepileptic Drugs

Generally, the prevalence of epilepsy does not exceed 0.9% of the population and approximately 70% of epilepsy patients may be adequately controlled with antiepileptic drugs (AEDs). Moreover, status epilepticus (SE) or even a single seizure may produce neurodegeneration within the brain and SE has been recognized as one of acute brain insults leading to acquired epilepsy via the process of epileptogenesis. Two questions thus arise: (1) Are AEDs able to inhibit SE-induced neurodegeneration? and (2) if so, can a probable neuroprotective potential of particular AEDs stop epileptogenesis? An affirmative answer to the second question would practically point to the preventive potential of a given neuroprotective AED following acute brain insults. The available experimental data indicate that diazepam (at low and high doses), gabapentin, pregabalin, topiramate and valproate exhibited potent or moderate neuroprotective effects in diverse models of SE in rats. However, only diazepam (at high doses), gabapentin and pregabalin exerted some protective activity against acquired epilepsy (spontaneous seizures). As regards valproate, its effects on spontaneous seizures were equivocal. With isobolography, some supra-additive combinations of AEDs have been delineated against experimental seizures. One of such combinations, levetiracetam + topiramate proved highly synergistic in two models of seizures and this particular combination significantly inhibited epileptogenesis in rats following status SE. Importantly, no neuroprotection was evident. It may be strikingly concluded that there is no correlation between neuroprotection and antiepileptogenesis. Probably, preclinically verified combinations of AEDs may be considered for an anti-epileptogenic therapy.

Pharmacodynamic interactions of antiepileptic drugs: From bench to clinical practice

BACKGROUND

Approximately 50% of patients do not achieve seizure control with antiepileptic drug (AED) monotherapy, and polytherapy, with more than one AED, is often required. To date, no evidence-based criteria on how to combine AEDs exist.

OBJECTIVE

This narrative review aimed to provide critical findings of the available literature about the role of pharmacodynamic AEDs' interactions in patients whose epilepsies were treated with polytherapy.

METHODS

Electronic databases, Medical Literature Analysis and Retrieval System Online (MEDLINE) and Excerpta Medica dataBASE (EMBASE), were systematically searched to identify relevant studies on pharmacodynamic AEDs' interactions in patients with epilepsy.

RESULTS AND CONCLUSION

Most data on AED combinations are coming from animal models and preclinical studies. Combining AEDs with different mechanisms of actions seems to have greater effectiveness and lower risk of adverse event development. Conversely, the combination of AEDs may cause pharmacodynamic synergistic effects that may result in not only increased efficacy but also more adverse effects. Despite some AED associations that have been proven to be effective in specific epilepsy/seizure type (e.g., phenobarbital+/phenytoin for tonic seizures and ethosiximide + valproate for absences; lamotrigine + valproate for various epilepsy/seizure types), no clear and definitive evidence exists about AED combinations in humans. Examples of pharmacodynamic interactions that possibly explain the synergistic effects on efficacy or adverse effects include the combination between vigabatrin or pregabalin and sodium channel blockers (supra-additive antiseizure effect) and lacosamide combined with other sodium channel blockers (infra-additive antiseizure effect and neurotoxicity synergistic). The pharmacodynamic lamotrigine-valproate interaction is also supported by synergistic adverse events. Therefore, well-designed double-blind prospective studies recruiting a sufficient number of patients possibly with a crossover design and carefully ascertain the role of pharmacokinetic interactions and variations of AEDs' levels in the blood are needed.

Mechanisms of action of currently used antiseizure drugs

Antiseizure drugs (ASDs) prevent the occurrence of seizures; there is no evidence that they have disease-modifying properties. In the more than 160 years that orally administered ASDs have been available for epilepsy therapy, most agents entering clinical practice were either discovered serendipitously or with the use of animal seizure models. The ASDs originating from these approaches act on brain excitability mechanisms to interfere with the generation and spread of epileptic hyperexcitability, but they do not address the specific defects that are pathogenic in the epilepsies for which they are prescribed, which in most cases are not well understood. There are four broad classes of such ASD mechanisms: (1) modulation of voltage-gated sodium channels (e.g. phenytoin, carbamazepine, lamotrigine), voltage-gated calcium channels (e.g. ethosuximide), and voltage-gated potassium channels [e.g. retigabine (ezogabine)]; (2) enhancement of GABA-mediated inhibitory neurotransmission (e.g. benzodiazepines, tiagabine, vigabatrin); (3) attenuation of glutamate-mediated excitatory neurotransmission (e.g. perampanel); and (4) modulation of neurotransmitter release via a presynaptic action (e.g. levetiracetam, brivaracetam, gabapentin, pregabalin). In the past two decades there has been great progress in identifying the pathophysiological mechanisms of many genetic epilepsies. Given this new understanding, attempts are being made to engineer specific small molecule, antisense and gene therapies that functionally reverse or structurally correct pathogenic defects in epilepsy syndromes. In the near future, these new therapies will begin a paradigm shift in the treatment of some rare genetic epilepsy syndromes, but targeted therapies will remain elusive for the vast majority of epilepsies until their causes are identified. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

The role of polytherapy in the management of epilepsy: suggestions for rational antiepileptic drug selection

Introduction: Antiepileptic polytherapy may be indicated in patients experiencing drug-resistant epilepsy. To date, there are no evidence-based criteria on how to combine different antiepileptic drugs (AEDs) together, in order to obtain the best therapeutic response.Areas covered: This paper reviews the available data about the various associations of AEDs in patients undergoing polytherapy, focusing on the most effective and well-tolerated polytherapies. Moreover, some controversial aspects of this topic are addressed.Expert opinion: Nowadays, there are no guidelines on polytherapy in patients with epilepsy; thus, the management of pharmacoresistant epilepsy is still uncertain, except for valproate/lamotrigine combination, which seems to be the only one recommended. Data regarding mechanism of action, pharmacokinetics, tolerability, and, more importantly, the analysis of the valuable clinical studies of drug combinations can help physicians to choose the best and most effective AED association for each patient.

Clinical opinion: Earlier employment of polytherapy in sequential pharmacotherapy of epilepsy

Modern pharmacotherapy for epilepsy consists of orderly, sequential drug trials, in which antiepileptic drugs (AEDs) are chosen under the concept of individual patient-oriented (or - tailored) pharmacotherapy. Although monotherapy has been established as the preferred mode of AEDs therapy in both newly diagnosed and drug resistant epilepsies, there are still lack of evidence to favor either monotherapy or polytherapy in epilepsy, which has generated continuing controversies on the preferred mode of pharmacotherapy. However, each mode of pharmacotherapy may have both advantages and disadvantages, which are different and variable related to individual case scenario. We conducted a brief comparative overview between monotherapy and polytherapy to provide clues for earlier employment of polytherapy in each steps of sequential drug trials. Previous claims about the advantages of monotherapy over polytherapy are not supported but gradually losing its ground by the introduction of a large number of drugs carrying pharmacological advantages for combination therapy. Current evidence stresses the importance of combining drugs having synergistic interactions for better outcome of polytherapy, which has not been considered in previous clinical investigations comparing monotherapy and polytherapy. It is likely that a significant improvement in the outcome of current AEDs therapy is feasible by earlier employment of polytherapy as well as identification of combination drug regimens carrying synergistic interactions. At present, lamotrigine(LTG) and valproate(VPA) combination regimen is the only well documented synergistic regimen, but there are a long-list of candidate regimens requiring future trials in appropriate designs.

Engineering brain activity patterns by neuromodulator polytherapy for treatment of disorders

Conventional drug screens and treatments often ignore the underlying complexity of brain network dysfunctions, resulting in suboptimal outcomes. Here we ask whether we can correct abnormal functional connectivity of the entire brain by identifying and combining multiple neuromodulators that perturb connectivity in complementary ways. Our approach avoids the combinatorial complexity of screening all drug combinations. We develop a high-speed platform capable of imaging more than 15000 neurons in 50ms to map the entire brain functional connectivity in large numbers of vertebrates under many conditions. Screening a panel of drugs in a zebrafish model of human Dravet syndrome, we show that even drugs with related mechanisms of action can modulate functional connectivity in significantly different ways. By clustering connectivity fingerprints, we algorithmically select small subsets of complementary drugs and rapidly identify combinations that are significantly more effective at correcting abnormal networks and reducing spontaneous seizures than monotherapies, while minimizing behavioral side effects. Even at low concentrations, our polytherapy performs superior to individual drugs even at highest tolerated concentrations.

Brain disorders are associated with network dysfunctions that are not addressed by conventional drug screens. Here, the authors use high-throughput functional imaging of brain activity in zebrafish larvae to study the effects of individual drugs on network connectivity and demonstrate an algorithm that predicts the most effective drug combinations to normalize both the activity patterns and the animal behavior.

Increased Antiseizure Effectiveness with Tiagabine Combined with Sodium Channel Antagonists in Mice Exposed to Hyperbaric Oxygen

Hyperbaric oxygen (HBO₂) is acutely toxic to the central nervous system, culminating in EEG spikes and tonic-clonic convulsions. GABA enhancers and sodium channel antagonists improve seizure latencies in HBO₂ when administered individually, while combining antiepileptic drugs from different functional classes can provide greater seizure latency. We examined the combined effectiveness of GABA enhancers (tiagabine and gabapentin) with sodium channel antagonists (carbamazepine and lamotrigine) in delaying HBO₂-induced seizures. A series of experiments in C57BL/6 mice exposed to 100% oxygen at 5 atmospheres absolute (ATA) were performed. We predicted equally effective doses from individual drug-dose response curves, and the combinations of tiagabine + carbamazepine or lamotrigine were tested to determine the maximally effective combined doses to be used in subsequent experiments designed to identify the type of pharmacodynamic interaction for three fixed-ratio combinations (1:3, 1:1, and 3:1) using isobolographic analysis. For both combinations, the maximally effective combined doses increased seizure latency over controls > 5-fold and were determined to interact synergistically for fixed ratios 1:1 and 3:1, additive for 1:3. These results led us to explore whether the benefits of these drug combinations could be extended to the lungs, since a centrally mediated mechanism is believed to mediate hyperoxic-induced cardiogenic lung injury. Indeed, both combinations attenuated bronchoalveolar lavage protein content by ~ 50%. Combining tiagabine with carbamazepine or lamotrigine not only affords greater antiseizure protection in HBO₂ but also allows for lower doses to be used, minimizing side effects, and attenuating acute lung injury.

Effect of Nobiletin on Experimental Model of Epilepsy

Background

The effects of nobiletin, a plant-derived flavonoid was examined against pentylenetetrazole (PTZ)-induced seizures. The study also aimed to assess whether nobiletin potentiated the effects of antiepileptic drug clonazepam (CZP).

Methods

PTZ (92 mg/kg, subcutaneous) was used to induce seizures in mice. Treatment groups (n = 18/group) received nobiletin (12.5, 25, or 50 mg/kg) via oral gavage for 6 consecutive days and 45 min prior to PTZ injection. CZP (0.015-2.0 mg/kg) was administered 15 min prior to PTZ. Skeletal muscle strength was assessed by measuring grip strength and Chimney test was performed to study the motor performance in animals. TUNEL assay was done to study neuro-apoptosis. RT-PCR and Western blot analysis were performed for assessment of mRNA and protein expressions.

Results

Nobiletin and CZP improved muscle strength and motor coordination and reduced seizure severity significantly. The administration of nobiletin and CZP, individually or in combination, downregulated seizure-induced increases in apoptotic cell count and apoptotic protein expression, modulated the expression of gamma-aminobutyric acid (GABA)A and glutamate decarboxylase 65 and restored the glutamate/GABA balance. Nobiletin and CZP administration significantly upregulated phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling.

Conclusion

Nobiletin exerted protective effect against seizures by regulating signaling pathways associated with epileptogenesis and potentiated the effects of CZP.

Levetiracetam combined with ACEA, highly selective cannabinoid CB1 receptor agonist changes neurogenesis in mouse brain

The aim of the study was to evaluate the impact of second generation antiepileptic drug levetiracetam (LEV) with arachidonyl-2'-chloroethylamide (ACEA) on proliferating neural precursor cells in mouse brain. Additionally, we established the relationship between treatment with ACEA in combination with LEV and hippocampal neurogenesis in mouse brain. All experiments were performed on male CB57/BL mice injected i.p. with LEV (10 mg/kg), ACEA (10 mg/kg) and PMSF (30 mg/kg) for 10 days. Experiments were provided in two stages: stage 1- an acute response of proliferating neural precursor cells to ACEA and LEV administration (Ki-67 staining), stage 2 - a long term response to ACEA and LEV administration (BrDU, NeuN, GFAP staining). Results indicate that ACEA + PMSF and ACEA + PMSF + LEV significantly increased the total number of Ki-67 positive cells comparing to the control group. PMSF and LEV administered alone and in combination had no significant impact on cell proliferation compared to the control group. Results from neurogenesis study indicated that ACEA + PMSF administered alone and in combination with LEV increased the total number of BrDU cells compared to the control group, although LEV on its own decreased the number of BrDU cells. Moreover, the combination of ACEA + PMSF + LEV significantly increased the total number of newborn neurons compared to the control group. In turn, LEV significantly decreased the process of neurogenesis. Astrocytes were considerably reduced in all treated groups as compare to the control mice. These data provide substantial evidence that LEV administered chronically decreases the proliferation and differentiation of newly born cells while combination of LEV + ACEA significantly increases the level of newborn neurons in the dentate subgranular zone.

Interactions of Mexiletine with Novel Antiepileptic Drugs in the Maximal Electroshock Test in Mice: An Isobolographic Analysis

The aim of the study was to evaluate precisely the type of interactions between mexiletine (an antiarrhythmic drug) and four new generation antiepileptic drugs: lamotrigine, oxcarbazepine, topiramate and pregabalin in the maximal electroshock test in mice (MES). The isobolographic analysis was used to assess the nature of interactions between the tested drugs. Total brain concentrations of antiepileptics were also measured to detect possible pharmacokinetic interactions. The results obtained indicated that the mixture of mexiletine and pregabalin at the fixed ratios of 1:1 and 3:1 led to supra-additive interaction in terms of seizure suppression, while the proportion of 1:3 occurred additive. Synergism was also demonstrated for the combination of mexiletine and topiramate in all three proportions. Combinations of mexiletine with lamotrigine and mexiletine with oxcarbazepine were found to be additive. Adverse-effect profiles of mexiletine, antiepileptics and drug combinations were evaluated in the chimney test (motor coordination) and step-through passive-avoidance task (long-term memory). Mexiletine and drug combinations did not impair long-term memory. Moreover, all combinations of mexiletine with lamotrigine, oxcarbazepine and topiramate had no significant effect on motor coordination. However, the results from the chimney test indicated that pregabalin, administered alone at its ED₅₀ dose from the MES-test, significantly impaired motor performance. Similar adverse effects were observed when mexiletine was co-administered with pregabalin at the fixed-dose ratio combinations of 1:1 and 1:3. However, reduction of pregabalin dose at the fixed ratio of 3:1 seems to prevent significant motor impairment. The results may indicate that mexiletine can be considered as an adjunctive drug in antiepileptic treatment, particularly in patients with concomitant cardiac arrhythmia.

A viewpoint on rational and irrational fixed-drug combinations

INTRODUCTION

Considering that there are around 30% of patients with epilepsy resistant to monotherapy, the use of synergistic combinations of antiepileptic drugs is of particular importance. This review shows most beneficial as well as irrational combined treatments both from an experimental and clinical point of view. Areas covered: Preferably, experimental data derived from studies evaluating synergy, additivity, or antagonism by relevant methods, in terms of anticonvulsant or neurotoxic effects and pharmacokinetic data have been considered. Although there have been no randomized clinical trials on this issue, the clinical data have been analyzed from studies on considerable numbers of patients. Case-report studies have been not considered. Expert commentary: The experimental data provide a strong support that co-administration of lamotrigine with carbamazepine is negative, considering the anticonvulsant and neurotoxic effects. Clinical reports do not entirely support this conclusion. Other experimentally documented negative combinations comprise lamotrigine+ oxcarbazepine and oxcarbazepine+ phenytoin. From the experimental and clinical point of view, a combination of lamotrigine+ valproate may deserve recommendation. Other most positive experimental and clinical combinations include carbamazepine+valproate, phenytoin+phenobarbital, carbamazepine+gabapentin, carbamazepine+topiramate, levetiracetam+valproate, levetiracetam+carbamazepine. Certainly, experimental data have some limitations (non-epileptic animals, acute administration of antiepileptic drugs) so all experimental recommendations need a careful clinical evaluation.

A minimally invasive neurostimulation method for controlling abnormal synchronisation in the neuronal activity

Many collective phenomena in Nature emerge from the -partial- synchronisation of the units comprising a system. In the case of the brain, this self-organised process allows groups of neurons to fire in highly intricate partially synchronised patterns and eventually lead to high level cognitive outputs and control over the human body. However, when the synchronisation patterns are altered and hypersynchronisation occurs, undesirable effects can occur. This is particularly striking and well documented in the case of epileptic seizures and tremors in neurodegenerative diseases such as Parkinson's disease. In this paper, we propose an innovative, minimally invasive, control method that can effectively desynchronise misfiring brain regions and thus mitigate and even eliminate the symptoms of the diseases. The control strategy, grounded in the Hamiltonian control theory, is applied to ensembles of neurons modelled via the Kuramoto or the Stuart-Landau models and allows for heterogeneous coupling among the interacting unities. The theory has been complemented with dedicated numerical simulations performed using the small-world Newman-Watts network and the random Erdős-Rényi network. Finally the method has been compared with the gold-standard Proportional-Differential Feedback control technique. Our method is shown to achieve equivalent levels of desynchronisation using lesser control strength and/or fewer controllers, being thus minimally invasive.

Combination of phenobarbital with phenytoin and pregabalin produces synergy in the mouse tonic-clonic seizure model: An isobolographic analysis

AIMS

Despite many antiepileptic drugs (AEDs) are available to treat epilepsy, there is still about 30% of epilepsy patients inadequately treated with these AEDs. For these patients, polytherapy with two or three AEDs to fully control their seizure attacks is recommended. Unfortunately, polytherapy is always associated with drug interactions, whose nature may be beneficial, neutral or unfavorable. To determine a type of interaction for the combination of three AEDs (i.e., phenobarbital [PB], phenytoin [PHT] and pregabalin [PGB]) at the fixed-ratio of 1:1:1, we used a model of tonic-clonic seizures in male albino Swiss mice.

MATERIALS AND METHOD

Tonic-clonic seizures in mice were evoked by a current (sine-wave, 25 mA, 500 V, 0.2 s stimulus duration) delivered via auricular electrodes. The anticonvulsant effects of the three-drug combination (PB, PHT and PGB) in terms of suppression of tonic-clonic seizures in mice were assessed with type I isobolographic analysis. Potential acute side effects for the mixture of PB, PHT and PGB along with total brain concentrations of the AEDs were determined to confirm pharmacodynamic nature of observed interaction.

RESULTS

The three-drug combination of PB, PHT and PGB (at the fixed-ratio of 1:1:1) exerted synergistic interaction (at P < 0.01) in the mouse model of tonic-clonic seizures. The combination of PB, PHT and PGB did not produce any side effects in experimental animals, when measuring long-term memory, muscular strength and motor coordination. The measurement of total brain concentrations of PB, PHT and PGB was conducted to confirm that none of the three AEDs significantly influenced total brain concentrations (pharmacokinetic profiles) of the other co-administered AEDs in mice.

CONCLUSIONS

The synergistic pharmacodynamic interaction for the combination of PB, PHT and PGB observed in this preclinical study can be translated into clinical settings and this favorable AED combination is worthy of being recommended to some patients with refractory epilepsy.

Antiepileptic drug reduction and increased risk of stimulation-evoked focal to bilateral tonic-clonic seizure during cortical stimulation in patients with focal epilepsy

INTRODUCTION

Stimulation-evoked focal to bilateral tonic-clonic seizure (FBTCS) can be a stressful and possibly harmful adverse event for patients during cortical stimulation (CS). We evaluated if drug load reduction of antiepileptic drugs (AEDs) during CS increases the risk of stimulation-evoked FBTCS.

MATERIAL AND METHODS

In this retrospective cohort study, we searched our local database for patients with drug-resistant epilepsy who underwent invasive video-EEG monitoring and CS in the University Hospital la Fe Valencia from January 2006 to November 2016. The AED drug load was calculated with the defined daily dose. We applied a uni- and multivariate logistic regression model to estimate the risk of stimulation-evoked FBTCS and evaluate possible influencing factors. Furthermore, we compared patients whose AEDs were completely withdrawn with those whose AEDs were not.

RESULTS

Fifty-eight patients met the inclusion criteria and were included in the analysis. Stimulating 3806 electrode contact pairs, 152 seizures were evoked in 28 patients (48.3%). Ten seizures (6.6%) in seven patients (12.1%) evolved to FBTCS. In the univariate and multivariate analysis, a 10% reduction in drug load was associated with an increase of the odds ratio (OR) of stimulation-evoked FBTCS by 1.9 (95%-CI 1.2, 4.0, p-value=0.04) and 1.9 (95%-CI 1.2, 4.6, p-value=0.04), respectively. In patients, whose AEDs were completely withdrawn the OR of FBTCS increased by 9.1 (95%CI 1.7, 69.9, p-value=0.01) compared with patients whose AEDs were not completely withdrawn. No other factor (implantation type, maximum stimulus intensity, number of stimulated contacts, history of FBTCS, age, gender, or epilepsy type) appears to have a significant effect on the risk of stimulation-evoked FBTCS.

CONCLUSIONS

The overall risk of stimulation-evoked FBTCS during CS is relatively low. However, a stronger reduction and, especially, a complete withdrawal of AEDs are associated with an increased risk of stimulation-evoked FBTCS.

Selecting Rational Drug Combinations in Epilepsy

Monotherapy remains the standard initial therapy of epilepsy, but when the first antiepileptic drug (AED) fails, combination therapy may be considered. The choice of combination therapy should take into consideration pharmacokinetic interactions, as well as pharmacodynamic interactions related to mechanism of action. There is evidence that an AED combination with different mechanisms of action is more likely to be successful than a combination with the same mechanisms. The combination of lamotrigine and valproate has been demonstrated to be synergistic in its efficacy. However, there are limited data to support other synergistic AED combinations.

Preliminary study of the association between the elimination parameters of phenytoin and phenobarbital

BACKGROUND

Therapeutic drug monitoring is essential for both phenytoin and phenobarbital therapy given their narrow therapeutic indexes. Nevertheless, the measurement of either phenytoin or phenobarbital concentrations might not be available in some rural hospitals. Information assisting individualized phenytoin and phenobarbital combination therapy is important. This study's objective was to determine the relationship between the maximum rate of metabolism of phenytoin (Vmax) and phenobarbital clearance (CLPB), which can serve as a guide to individualized drug therapy.

METHODS

Data on phenytoin and phenobarbital concentrations of 19 epileptic patients concurrently receiving both drugs were obtained from medical records. Phenytoin and phenobarbital pharmacokinetic parameters were studied at steady-state conditions. The relationship between the elimination parameters of both drugs was determined using simple linear regression.

RESULTS

A high correlation coefficient between Vmax and CLPB was found [r=0.744; p<0.001 for Vmax (mg/kg/day) vs. CLPB (L/kg/day)]. Such a relatively strong linear relationship between the elimination parameters of both drugs indicates that Vmax might be predicted from CLPB and vice versa.

CONCLUSIONS

Regression equations were established for estimating Vmax from CLPB, and vice versa in patients treated with combination of phenytoin and phenobarbital. These proposed equations can be of use in aiding individualized drug therapy.

Beneficial Combination of Lacosamide with Retigabine in Experimental Animals: An Isobolographic Analysis

BACKGROUND/AIM

To isobolographically determine the types of interactions that occur between retigabine and lacosamide (LCM; two third-generation antiepileptic drugs) with respect to their anticonvulsant activity and acute adverse effects (sedation) in the maximal electroshock-induced seizures (MES) and chimney test (motor performance) in adult male Swiss mice.

METHODS

Type I isobolographic analysis for nonparallel dose-response effects for the combination of retigabine with LCM (at the fixed-ratio of 1:1) in both the MES and chimney test in mice was performed. Brain concentrations of retigabine and LCM were measured by high-pressure liquid chromatography (HPLC) to characterize any pharmacokinetic interactions occurring when combining these drugs.

RESULTS

Linear regression analysis revealed that retigabine had its dose-response effect line nonparallel to that of LCM in both the MES and chimney tests. The type I isobolographic analysis illustrated that retigabine combined with LCM (fixed-ratio of 1:1) exerted an additive interaction in the mouse MES model and sub-additivity (antagonism) in the chimney test. With HPLC, retigabine and LCM did not mutually change their total brain concentrations, thereby confirming the pharmacodynamic nature of the interaction.

CONCLUSION

LCM combined with retigabine possesses a beneficial preclinical profile (benefit index ranged from 2.07 to 2.50) and this 2-drug combination is worth recommending as treatment plan to patients with pharmacoresistant epilepsy.