Progress report on new antiepileptic drugs: a summary of the Fifth Eilat Conference (EILAT V)

Population Pharmacokinetics and Exposure-Safety of Lipophilic Conjugates Prodrug DP-VPA in Healthy Chinese Subjects for Dose Regime Exploring

Phospholipid-valproic acid (DP-VPA)is a prodrug for treating epilepsy. The present study explored the pharmacokinetics (PK) and exposure safety of DP-VPA to provide a basis for future studies exploring the safe dosage and therapeutic strategies for epilepsy. The study included a randomized placebo-controlled dose-escalation tolerance evaluation trial and a randomized triple crossover food-effect trial in healthy Chinese volunteers. A population pharmacokinetic (PopPK) model was established to analyze the PK of DP-VPA and active metabolite VPA. The exposure safety was assessed with the adverse drug reaction (ADR) in CNS. The PopPK of DP-VPA and metabolite VPA fitted a two-compartment model coupling one-compartment with Michaelis-Menten metabolite kinetics and first-order elimination. The absorption processes after single oral administration of DP-VPA tablet demonstrated nonlinear characteristics, including 0-order kinetic phase and time-dependent phase fitting Weibull distribution. The final model indicated that the DP-VPA PK was significantly affected by dosage and food. The exposure-safety relationship demonstrated a generalized linear regression; mild/moderate ADRs occurred in some subjects with 600 mg and all subjects with 1500 mg of DP-VPA, and no severe ADRs were reported up to 2400 mg. In conclusion, the study established a PopPK model describing the processing of DP-VPA and VPA in healthy Chinese subjects. DP-VPA showed good tolerance after a single dose of 600-2400 mg with nonlinear PK and was affected by dosage and food. Based on the association between neurological ADRs and higher exposure to DP-VPA by exposure-safety analysis, 900-1200 mg was recommended for subsequent study of safety and clinical effectiveness.

Real-Time Reaction Monitoring of Azide-Alkyne Cycloadditions Using Benchtop NMR-Based Signal Amplification by Reversible Exchange (SABRE)

Rufinamide, possessing a triazole ring, is a new antiepileptic drug (AED) relatively well-absorbed in the lower dose range (10 mg/kg per day) and is currently being used in antiepileptic medications. Triazole derivatives can interact with various enzymes and receptors in biological systems via diverse non-covalent interactions, thus inducing versatile biological effects. Strain-promoted azide-alkyne cycloaddition (SPAAC) is a significant method for obtaining triazoles, even under physiological conditions, in the absence of a copper catalyst. To confirm the progress of chemical reactions under biological conditions, research on reaction monitoring at low concentrations is essential. This promising strategy is gaining acceptance for applications in fields such as drug development and nanoscience. We investigated the optimum Ir catalyst and magnetic field for achieving maximum proton hyperpolarization transfer in triazole derivatives. These reactions were analyzed using signal amplification by reversible exchange (SABRE) to overcome the limitations of low sensitivity in nuclear magnetic resonance spectroscopy, when monitoring copper-free click reactions in real time. Finally, a more versatile copper-catalyzed click reaction was monitored in real time, using a 60 MHz benchtop NMR system, in order to analyze the reaction mechanism.

Insights into Structural Modifications of Valproic Acid and Their Pharmacological Profile

Valproic acid (VPA) is a well-established anticonvulsant drug discovered serendipitously and marketed for the treatment of epilepsy, migraine, bipolar disorder and neuropathic pain. Apart from this, VPA has potential therapeutic applications in other central nervous system (CNS) disorders and in various cancer types. Since the discovery of its anticonvulsant activity, substantial efforts have been made to develop structural analogues and derivatives in an attempt to increase potency and decrease adverse side effects, the most significant being teratogenicity and hepatotoxicity. Most of these compounds have shown reduced toxicity with improved potency. The simple structure of VPA offers a great advantage to its modification. This review briefly discusses the pharmacology and molecular targets of VPA. The article then elaborates on the structural modifications in VPA including amide-derivatives, acid and cyclic analogues, urea derivatives and pro-drugs, and compares their pharmacological profile with that of the parent molecule. The current challenges for the clinical use of these derivatives are also discussed. The review is expected to provide necessary knowledgebase for the further development of VPA-derived compounds.

Current Pharmacologic Strategies for Treatment of Intractable Epilepsy in Children

Epileptic encephalopathy (EE) is a devastating pediatric disease that features medically resistant seizures, which can contribute to global developmental delays. Despite technological advancements in genetics, the neurobiological mechanisms of EEs are not fully understood, leaving few therapeutic options for affected patients. In this review, we introduce the most common EEs in pediatrics (i.e., Ohtahara syndrome, Dravet syndrome, and Lennox-Gastaut syndrome) and their molecular mechanisms that cause excitation/inhibition imbalances. We then discuss some of the essential molecules that are frequently dysregulated in EEs. Specifically, we explore voltage-gated ion channels, synaptic transmission-related proteins, and ligand-gated ion channels in association with the pathophysiology of Ohtahara syndrome, Dravet syndrome, and Lennox-Gastaut syndrome. Finally, we review currently available antiepileptic drugs used to treat seizures in patients with EEs. Since these patients often fail to achieve seizure relief even with the combination therapy, further extensive research efforts to explore the involved molecular mechanisms will be required to develop new drugs for patients with intractable epilepsy.

Discovery of Potent Carbonic Anhydrase Inhibitors as Effective Anticonvulsant Agents: Drug Design, Synthesis, and In Vitro and In Vivo Investigations

Two sets of benzenesulfonamide-based effective human carbonic anhydrase (hCA) inhibitors have been developed using the tail approach. The inhibitory action of these novel molecules was examined against four isoforms: hCA I, hCA II, hCA VII, and hCA XII. Most of the molecules disclosed low to medium nanomolar range inhibition against all tested isoforms. Some of the synthesized derivatives selectively inhibited the epilepsy-involved isoforms hCA II and hCA VII, showing low nanomolar affinity. The anticonvulsant activity of selected sulfonamides was assessed using the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (sc-PTZ) in vivo models of epilepsy. These potent CA inhibitors effectively inhibited seizures in both epilepsy models. The most effective compounds showed long duration of action and abolished MES-induced seizures up to 6 h after drug administration. These sulfonamides were found to be orally active anticonvulsants, being nontoxic in neuronal cell lines and in animal models.

Microtubule Dynamics and Neuronal Excitability: Advances on Cytoskeletal Components Implicated in Epileptic Phenomena

Extensive researches have deepened knowledge on the role of synaptic components in epileptogenesis, but limited attention has been devoted to the potential implication of the cytoskeleton. The study of the development of epilepsy and hyperexcitability states involves molecular, synaptic, and structural alterations of neuronal bioelectric activity. In this paper we aim to explore the neurobiological targets involved in microtubule functioning and cytoskeletal transport, i.e. how dynamic scaffolding of microtubules can influence neuronal morphology and excitability, in order to suggest a potential role for microtubule dynamics in the processes turning a normal neuronal network in a hyperexcited one. Pathophysiological alterations of microtubule dynamics inducing neurodegeneration, network remodeling and relative impairment on synaptic transmission were overviewed. Recent researches were reported on the phosphorylation state of microtubule-associated proteins such as tau in neurodegenerative diseases and epileptic states, but also on the effect of microtubule-active agents influencing cytoskeleton destabilization in epilepsy models. The manipulation of microtubule polymerization was found effective in the modulation of hyperexcitability. In addition, it was considered the importance of microtubules and related neurotrophic factors during neural development since they are essential for the formation of a properly functional neuronal network. Otherwise, this can lead to cognitive deficits, hyperexcitability phenomena and neurodevelopmental disorders. Lastly, we evaluated the role of microtubule dynamics on neuronal efficiency considering their importance in the transport of mitochondria, cellular elements fulfilling energy requirements for neuronal activity, and a putative influence on cannabinoid-mediated neuroprotection. This review provides novel perspectives for the implication of microtubule dynamics in the development of epileptic phenomena.

Drug-Lipid Conjugates for Enhanced Oral Drug Delivery

Oral drug delivery route is one of the most convenient and extensively utilised routes for drug administration. But there exists class of drugs which exhibit poor bioavailability on oral drug administration. Designing of drug-lipid conjugates (DLCs) is one of the rationale strategy utilised in overcoming this challenge. This review extensively covers the various dimensions of drug modification using lipids to attain improved oral drug delivery. DLCs help in improving oral delivery by providing benefits like improved permeability, stability in gastric environment, higher drug loading in carriers, formation of self-assembled nanostructures, etc. The clinical effectiveness of DLCs is highlighted from available marketed drug products along with many DLCs in phase of clinical trials. Conclusively, this drug modification strategy can potentially help in augmenting oral drug delivery in future.

Ancient and modern anticonvulsants act synergistically in a KCNQ potassium channel binding pocket

Epilepsy has been treated for centuries with herbal remedies, including leaves of the African shrub Mallotus oppositifolius, yet the underlying molecular mechanisms have remained unclear. Voltage-gated potassium channel isoforms KCNQ2–5, predominantly KCNQ2/3 heteromers, underlie the neuronal M-current, which suppresses neuronal excitability, protecting against seizures. Here, in silico docking, mutagenesis and cellular electrophysiology reveal that two components of M. oppositifolius leaf extract, mallotoxin (MTX) and isovaleric acid (IVA), act synergistically to open neuronal KCNQs, including KCNQ2/3 channels. Correspondingly, MTX and IVA combine to suppress pentylene tetrazole-induced tonic seizures in mice, whereas individually they are ineffective. Co-administering MTX and IVA with the modern, synthetic anticonvulsant retigabine creates a further synergy that voltage independently locks KCNQ2/3 open. Leveraging this synergy, which harnesses ancient and modern medicines to exploit differential KCNQ isoform preferences, presents an approach to developing safe yet effective anticonvulsants.

In some countries, leaves of the shrub Mallotus oppositifolius have been used to treat epilepsy. Here, authors look at the structural and molecular basis for how chemical components of M. oppositifolius have their anticonvulsant effects, via modulation of potassium channel activity.

Discovery of potent anti-convulsant carbonic anhydrase inhibitors: Design, synthesis, in vitro and in vivo appraisal

We report the design, synthesis and pharmacological assessment of novel benzenesulfonamide derivatives acting as effective carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. All the synthesized compounds were screened for their CA inhibitory action against four isoforms of human origin (h), i.e. hCA I, hCA II, hCA VII and hCA IX. In-vitro carbonic anhydrase inhibition studies have shown that first series, 4-(2-(4-(4-substitutedpiperazin-1-yl)benzylidene)hydrazinyl)benzenesulfonamides (4a- 4i) bestowed low nanomolar range to medium nanomolar range inhibitors against hCA II and hCA VII, effectively involved in epileptogenesis. Furthermore, compounds belonging to the second series, 4-(2-(4-(4-substitutedpiperazin-yl)benzylidene)hydrazinecarbonyl)benzenesulfonamides (8a-8k) showed effective inhibition against hCA VII, being less effective against other hCA isoforms. Inspiring with obtained CA inhibition results, we have chosen some of the potent hCA II and hCA VII inhibitors (4g, 4i and 8d) to test their anti-convulsant efficacy in MES and sc-PTZ seizure tests in Swiss Albino male mice. In result, these compounds significantly attenuated both electrical (MES) as well as chemical (sc-PTZ) induced seizures. Next, in advance anticonvulsant tests, compound 8d displayed long duration of action in time course study and successfully attenuated MES induced seizure in mice up to 6 h after drug administration without showing neurotoxicity in rotarod test. Moreover, this compound was also found to be orally active and effectively abolished generalized tonic-clonic seizures in male Wistar rats upon oral administration, being non-toxic in sub acute toxicity studies.

Discovery of Benzenesulfonamide Derivatives as Carbonic Anhydrase Inhibitors with Effective Anticonvulsant Action: Design, Synthesis, and Pharmacological Evaluation

Two series of novel benzenesulfonamide derivatives were synthesized and evaluated for their human carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity against four isoforms, hCA I, hCA II, hCA VII, and hCA IX. It was found that compounds of both series showed low to medium nanomolar inhibitory potential against all isoforms. Some of these derivatives displayed selective inhibition against the epileptogenesis related isoforms hCA II and VII, within the nanomolar range. These potent hCA II and VII inhibitors were evaluated as anticonvulsant agents against MES and sc-PTZ induced convulsions. These sulfonamides effectively abolished induced seizures in both models. Furthermore, time dependent seizure protection capability of the most potent compound was also evaluated. A long duration of action was displayed, with efficacy up to 6 h after drug administration. The compound appeared as an orally active anticonvulsant agent without showing neurotoxicity in a rotarod test, a nontoxic chemical profile being observed in subacute toxicity study.

Discovery of Benzenesulfonamides with Potent Human Carbonic Anhydrase Inhibitory and Effective Anticonvulsant Action: Design, Synthesis, and Pharmacological Assessment

We report two series of novel benzenesulfonamide derivatives acting as effective carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. The synthesized compounds were tested against human (h) isoforms hCA I, hCA II, hCA VII, and hCA XII. The first series of compounds, 4-(3-(2-(4-substitued piperazin-1-yl)ethyl)ureido)benzenesulfonamides, showed low nanomolar inhibitory action against hCA II, being less effective against the other isoforms. The second series, 2-(4-substitued piperazin-1-yl)-N-(4-sulfamoylphenyl)acetamide derivatives, showed low nanomolar inhibitory activity against hCA II and hCA VII, isoforms involved in epileptogenesis. Some of these derivatives were evaluated for their anticonvulsant activity and displayed effective seizure protection against MES and scPTZ induced seizures in Swiss Albino mice. These sulfonamides were also found effective upon oral administration to Wistar rats and inhibited MES induced seizure episodes in this animal model of the disease. Some of the new compounds showed a long duration of action in the performed time course anticonvulsant studies, being nontoxic in subacute toxicity studies.

Identification of Novel Signal Transduction, Immune Function, and Oxidative Stress Genes and Pathways by Topiramate for Treatment of Methamphetamine Dependence Based on Secondary Outcomes

BACKGROUND

Topiramate (TPM) is suggested to be a promising medication for treatment of methamphetamine (METH) dependence, but the molecular basis remains to be elucidated.

METHODS

Among 140 METH-dependent participants randomly assigned to receive either TPM (N = 69) or placebo (N = 71) in a previously conducted randomized controlled trial, 50 TPM- and 49 placebo-treated participants had a total 212 RNA samples available at baseline, week 8, and week 12 time points. Following our primary analysis of gene expression data, we reanalyzed the microarray expression data based on a latent class analysis of binary secondary outcomes during weeks 1-12 that provided a classification of 21 responders and 31 non-responders with consistent responses at both time points.

RESULTS

Based on secondary outcomes, 1,381, 576, 905, and 711 differentially expressed genes at nominal P values < 0.05 were identified in responders versus non-responders for week 8 TPM, week 8 placebo, week 12 TPM, and week 12 placebo groups, respectively. Among 1,381 genes identified in week 8 TPM responders, 359 genes were identified in both week 8 and week 12 TPM groups, of which 300 genes were exclusively detected in TPM responders. Of them, 32 genes had nominal P values < 5 × 10^-3 at either week 8 or week 12 and false discovery rates < 0.15 at both time points with consistent directions of gene expression changes, which include GABARAPL1, GPR155, and IL15RA in GABA receptor signaling that represent direct targets for TPM. Analyses of these 300 genes revealed 7 enriched pathways belonging to neuronal function/synaptic plasticity, signal transduction, inflammation/immune function, and oxidative stress response categories. No pathways were enriched for 72 genes exclusively detected in both week 8 and week 12 placebo groups.

CONCLUSION

This secondary analysis study of gene expression data from a TPM clinical trial not only yielded consistent results with those of primary analysis but also identified additional new genes and pathways on TPM response to METH addiction.

Synaptic Vesicle Glycoprotein 2A Ligands in the Treatment of Epilepsy and Beyond

The synaptic vesicle glycoprotein SV2A belongs to the major facilitator superfamily (MFS) of transporters and is an integral constituent of synaptic vesicle membranes. SV2A has been demonstrated to be involved in vesicle trafficking and exocytosis, processes crucial for neurotransmission. The anti-seizure drug levetiracetam was the first ligand to target SV2A and displays a broad spectrum of anti-seizure activity in various preclinical models. Several lines of preclinical and clinical evidence, including genetics and protein expression changes, support an important role of SV2A in epilepsy pathophysiology. While the functional consequences of SV2A ligand binding are not fully elucidated, studies suggest that subsequent SV2A conformational changes may contribute to seizure protection. Conversely, the recently discovered negative SV2A modulators, such as UCB0255, counteract the anti-seizure effect of levetiracetam and display procognitive properties in preclinical models. More broadly, dysfunction of SV2A may also be involved in Alzheimer's disease and other types of cognitive impairment, suggesting potential novel therapies for levetiracetam and its congeners. Furthermore, emerging data indicate that there may be important roles for two other SV2 isoforms (SV2B and SV2C) in the pathogenesis of epilepsy, as well as other neurodegenerative diseases. Utilization of recently developed SV2A positron emission tomography ligands will strengthen and reinforce the pharmacological evidence that SV2A is a druggable target, and will provide a better understanding of its role in epilepsy and other neurological diseases, aiding in further defining the full therapeutic potential of SV2A modulation.

Hippocampal Hyperexcitability is Modulated by Microtubule-Active Agent: Evidence from In Vivo and In Vitro Epilepsy Models in the Rat

The involvement of microtubule dynamics on bioelectric activity of neurons and neurotransmission represents a fascinating target of research in the context of neural excitability. It has been reported that alteration of microtubule cytoskeleton can lead to profound modifications of neural functioning, with a putative impact on hyperexcitability phenomena. Altogether, in the present study we pointed at exploring the outcomes of modulating the degree of microtubule polymerization in two electrophysiological models of epileptiform activity in the rat hippocampus. To this aim, we used in vivo maximal dentate activation (MDA) and in vitro hippocampal epileptiform bursting activity (HEBA) paradigms to assess the effects of nocodazole (NOC) and paclitaxel (PAC), that respectively destabilize and stabilize microtubule structures. In particular, in the MDA paroxysmal discharge is electrically induced, whereas the HEBA is obtained by altering extracellular ionic concentrations. Our results provided evidence that NOC 10 μM was able to reduce the severity of MDA seizures, without inducing neurotoxicity as verified by the immunohistochemical assay. In some cases, paroxysmal discharge was completely blocked during the maximal effect of the drug. These data were also in agreement with the outcomes of in vitro HEBA, since NOC markedly decreased burst activity that was even silenced occasionally. In contrast, PAC at 10 μM did not exert a clear action in both paradigms. The present study, targeting cellular mechanisms not much considered so far, suggests the possibility that microtubule-active drugs could modulate brain hyperexcitability. This contributes to the hypothesis that cytoskeleton function may affect synaptic processes, relapsing on bioelectric aspects of epileptic activity.

Lennox-Gastaut syndrome. Management update

Lennox-Gastaut syndrome (LGS) is a severe pediatric epilepsy syndrome characterized by mixed seizures, cognitive decline, and generalized slow (<3 Hz) spike wave discharges on electroencephalography. Atonic seizures result in dangerous drop attacks with risks of injury and impairment of the quality of life. The seizures are frequently resistant to multiple antiepileptic (AED) drugs. Newer AEDs, such as rufinamide, are now available. When multiple AED trials fail, non-pharmacological treatments such as the ketogenic diet, vagus nerve stimulation, and epilepsy surgery, should be considered. The aim of this review is to present an updated outline of LGS and the available treatments. Although the prognosis for complete seizure control remains poor, the addition of newer therapies provides an improved hope for some of these patients and their families. Further long term randomized controlled trials are required to compare different therapeutic interventions in terms of efficacy and tolerability.

Torin 1 partially corrects vigabatrin-induced mitochondrial increase in mouse

Recent findings in mice with targeted deletion of the GABA-metabolic enzyme succinic semialdehyde dehydrogenase revealed a new role for supraphysiological GABA (4-aminobutyric acid) in the activation of the mechanistic target of rapamycin (mTOR) that results in disruption of endogenous mitophagy. Employing biochemical and electron microscopic methodology, we examined the hypothesis that similar outcomes would be observed during intervention with vigabatrin, whose antiepileptic capacity hinges on central nervous system GABA elevation. Vigabatrin intervention was associated with significantly enhanced mitochondrial numbers and areas in normal mice that could be selectively normalized with the rapalog and mechanistic target of rapamycin inhibitor, Torin 1. Moreover, short-term administration of vigabatrin induced apoptosis and enhanced phosphorylation of mechanistic target of rapamycin Ser 2448 in liver. Our results provide new insight into adverse outcomes associated with vigabatrin intervention, and the first evidence that its administration is associated with increased mitochondrial number in central and peripheral tissues that may associate with mechanistic target of rapamycin function and enhanced cell death.

Pharmacokinetic of antiepileptic drugs in patients with hepatic or renal impairment

Many factors influence choice of antiepileptic drugs (AEDs), including efficacy of the drug for the indication (epilepsy, neuropathic pain, affective disorder, migraine), tolerability, and toxicity. The first-generation AEDs and some newer AEDs are predominately eliminated by hepatic metabolism. Other recent AEDs are eliminated by renal excretion of unchanged drug or a combination of hepatic metabolism and renal excretion. The effect of renal and hepatic disease on the dosing will depend on the fraction of the AED eliminated by hepatic and/or renal excretion, the metabolic isozymes involved, as well as the extent of protein binding, if therapeutic drug monitoring is used. For drugs that are eliminated by renal excretion, methods of estimating creatinine clearance can be used to determine dose adjustments. For drugs eliminated by hepatic metabolism, there are no specific markers of liver function that can be used to provide guidance in dosage adjustments. Based on studies with probe drugs, the hepatic metabolic enzymes are differentially affected depending on the cause and severity of hepatic disease, which can aid in predicting dose adjustment when clinical data are not available. Several AEDs are also associated with laboratory markers of mild hepatic dysfunction and, rarely, more severe hepatic injury. In contrast, the risk of renal injury from AEDs is generally low. In general, co-morbid hepatic or renal diseases influence the decision for the selection of an AED. For some patients dosing changes to their existing AEDs may be appropriate. For others, a change to another AED may be a better option.

Specific binding of lacosamide to collapsin response mediator protein 2 (CRMP2) and direct impairment of its canonical function: implications for the therapeutic potential of lacosamide

The novel antiepileptic drug lacosamide (LCM; SPM927, Vimpat®) has been heralded as having a dual-mode of action through interactions with both the voltage-gated sodium channel and the neurite outgrowth-promoting collapsin response mediator protein 2 (CRMP2). Lacosamide's ability to dampen neuronal excitability through the voltage-gated sodium channel likely underlies its efficacy in attenuating the symptoms of epilepsy (i.e., seizures). While the role of CRMP2 in epilepsy has not been well studied, given the proposed involvement of circuit reorganization in epileptogenesis, the ability of lacosamide to alter CRMP2 function may prove disease modifying. Recently, however, the validity of lacosamide's interaction with CRMP2 has come under scrutiny. In this review, we address the contradictory reports concerning the binding of lacosamide to CRMP2 as well as the ability of lacosamide to directly impact CRMP2 function. Additionally, we address similarly the contradicting reports regarding the potential disease-modifying effect of lacosamide on the development and progression of epilepsy. As the vast majority of antiepileptic drugs influences only the symptoms of epilepsy, the ability to hinder disease progression would be a major breakthrough in efforts to cure or prevent this debilitating syndrome.

lennox-Gastaut syndrome: an updateon treatment

Lennox-Gastaut syndrome (LGS) is a severe epileptic encephalopathy. Few current treatment options are effective in improving seizure control. This paper reviews the available treatments of LGS and discusses a new option in Canada, rufinamide. It is a wide spectrum anticonvulsant, approved in a number of countries for the treatment of LGS. In a randomized controlled trial in the LGS population, adjunctive rufinamide therapy has been shown to offer significantly greater reduction in total seizure frequency and tonic-atonic seizure frequency in comparison to placebo. Efficacy has been assessed over three years and appears to be sustained. Most adverse events were cognitive (e.g. somnolence) or gastrointestinal in nature and in many cases transient or mild. based on the efficacy and safety data on rufinamide obtained to date, this medication will provide additional benefits to patients with LGS in Canada and is an important consideration for our patients in the adjunctive treatment setting.

Lacosamide displays potent antinociceptive effects in animal models for inflammatory pain

Lacosamide is a functionalized amino acid which was initially synthesized as an antiepileptic drug. In addition to its broad anti-seizure activity, lacosamide was shown to display efficacy in animal models for neuropathic pain and is currently in phase III clinical development for the treatment of epilepsy and neuropathic pain. In order to further profile its antinociceptive properties, the effects of lacosamide on inflammatory pain in the formalin test, the carrageenan model and the adjuvant-induced arthritis model were investigated. For the formalin test, mice received an intraplantar injection of formalin and the subsequent licking response was measured over 45 min. Lacosamide was administered 30 min before formalin. For the carrageenan model, mechanical and thermal hyperalgesia were assessed 3 h following an intraplantar injection of carrageenan. Lacosamide was administered to rats 30 min before pain threshold measurements. For the adjuvant-induced arthritis test rats received intraplantar injections of Freund's complete adjuvant into the right hindpaw which lead to the development of arthritic symptoms in all animals tested for antinociception. On day 11 after arthritis induction, mechanical hyperalgesia was assessed by the modified Randall Selitto paw pressure test following acute treatment with lacosamide. Lacosamide dose-dependently attenuated mechanical hyperalgesia following carrageenan injection and in rats suffering from Freund's complete adjuvant-induced arthritis. Moreover, thermal hyperalgesia induced by carrageenan as well as the formalin-induced licking response were dose-dependently attenuated by lacosamide. These results suggest lacosamide may be active against various forms of acute and chronic inflammatory pain in humans.

Herbs in epilepsy: evidence for efficacy, toxicity, and interactions

Herbs and dietary supplements enjoy widespread use in the treatment of epilepsy although supportive data yielding efficacy and safety are lacking. Ten specific products, American hellebore, betony, blue cohosh, kava, mistletoe, mugwort, pipsissiwa, skullcap, valerian, and melatonin, have either multiple-cited recommendations for use in epilepsy or a rationale for antiepileptic action and are discussed in detail. These items paradoxically often have a proconvulsant effect in addition to potentially serious adverse effects. Herb-drug interactions also occur at the level of the P450 hepatic enzyme system of drug catabolism and the P-glycoprotein transport system regulating the entry of exogenous compounds into the vasculature or blood-brain barrier. Thus, significant pharmacokinetic interactions may occur, in addition to pharmacodynamic interactions and proconvulsant effects of alternative medications themselves. Patients should be inquired as to the nature of any alternative medicine products they are using, with the view that these products may be reasonable if traditional antiepileptic drug therapy is continued, potential adverse effects of the alternative agents are monitored, and the alternative and traditional agents do not conflict.

Antiepileptic drug interactions - principles and clinical implications

Antiepileptic drugs (AEDs) are widely used as long-term adjunctive therapy or as monotherapy in epilepsy and other indications and consist of a group of drugs that are highly susceptible to drug interactions. The purpose of the present review is to focus upon clinically relevant interactions where AEDs are involved and especially on pharmacokinetic interactions. The older AEDs are susceptible to cause induction (carbamazepine, phenobarbital, phenytoin, primidone) or inhibition (valproic acid), resulting in a decrease or increase, respectively, in the serum concentration of other AEDs, as well as other drug classes (anticoagulants, oral contraceptives, antidepressants, antipsychotics, antimicrobal drugs, antineoplastic drugs, and immunosupressants). Conversely, the serum concentrations of AEDs may be increased by enzyme inhibitors among antidepressants and antipsychotics, antimicrobal drugs (as macrolides or isoniazid) and decreased by other mechanisms as induction, reduced absorption or excretion (as oral contraceptives, cimetidine, probenicid and antacides). Pharmacokinetic interactions involving newer AEDs include the enzyme inhibitors felbamate, rufinamide, and stiripentol and the inducers oxcarbazepine and topiramate. Lamotrigine is affected by these drugs, older AEDs and other drug classes as oral contraceptives. Individual AED interactions may be divided into three levels depending on the clinical consequences of alterations in serum concentrations. This approach may point to interactions of specific importance, although it should be implemented with caution, as it is not meant to oversimplify fact matters. Level 1 involves serious clinical consequences, and the combination should be avoided. Level 2 usually implies cautiousness and possible dosage adjustments, as the combination may not be possible to avoid. Level 3 refers to interactions where dosage adjustments are usually not necessary. Updated knowledge regarding drug interactions is important to predict the potential for harmful or lacking effects involving AEDs.

GABAergic drugs in the treatment of epilepsy: modern or outmoded?

Antiepileptic drugs have a number of mechanisms of action that target brain excitability systems. The potentiation of GABAergic inhibitory neurotransmission represents a classic and well-known antiseizure effect. Currently available GABAergic antiepileptic drugs mainly target GABA(A) receptor-associated complexes, GABA reuptake or GABA catabolism. All these compounds, although generally effective, are limited by their deleterious effects on cognition and behavior. The challenge will be to find GABAergic drugs that exhibit the beneficial effects, without the adverse ones.

Pharmacotherapy of epilepsy: newly approved and developmental agents

This article discusses seven newly available antiepileptic drugs (AEDs) and agents in phase III development. Lacosamide, licensed as an adjunctive treatment for partial-onset seizures, primarily acts by enhancing sodium channel slow inactivation. At daily doses of 200-600 mg, the drug significantly reduced partial-onset seizures in adults with refractory epilepsy. The most common adverse effects are CNS related. Rufinamide, available as adjunctive treatment for seizures associated with Lennox-Gastaut syndrome, has an unclear mechanism of action, although it does block voltage-dependent sodium channels. Coadministration of valproic acid significantly increases rufinamide circulating concentrations. The drug has been shown to have efficacy for partial-onset, primary generalized tonic-clonic, tonic-atonic, absence and atypical absence seizures. Adverse effects are mainly somnolence, nausea and vomiting. Eslicarbazepine acetate, a carbamazepine analogue, was recently licensed as adjunctive treatment for partial-onset seizures. Eslicarbazepine acetate acts at voltage-gated sodium channels, although the precise mechanism of action is unclear. The drug had efficacy for partial-onset seizures in three randomized, double-blind, placebo-controlled studies, using 400, 800 or 1200 mg/day. Adverse effects include dizziness and somnolence. Retigabine (ezogabine) exerts its anticonvulsant effect through the opening of neuronal voltage-gated potassium channels. Following significant seizure reduction rates at dosages of 600, 900 and 1200 mg/day, license applications have been submitted for its use as adjunctive treatment for patients with partial-onset seizures. Dose-related adverse effects include somnolence, confusion and dizziness. Brivaracetam is the n-propyl analogue of levetiracetam. Mixed results have been obtained in phase III studies in patients with partial-onset seizures, and further trials in children, patients with photosensitive epilepsy and patients with partial-onset seizures are ongoing. Dizziness, headache and somnolence are the most common adverse effects reported. Perampanel was designed as an AMPA-type glutamate receptor antagonist. Following encouraging results from phase II studies in patients with refractory partial-onset seizures, recruitment for phase III trials is almost complete. Ganaxolone is a neurosteroid with potent antiepileptic activity that modulates GABA(A) receptors in the CNS. Ganaxolone has shown promise in a variety of seizure types. Dizziness and somnolence have been reported in some patients. The availability of new AEDs has widened the choices for clinicians treating patients with epilepsy. However, given the minimal improvement in prognosis and disappointing efficacy outcomes in double-blind, placebo-controlled, dose-ranging regulatory trials, it seems unlikely that these novel agents will have a major impact on outcomes for people with epilepsy.

Treating Lennox-Gastaut syndrome in epileptic pediatric patients with third-generation rufinamide

Lennox-Gastaut syndrome (LGS) is a rare but debilitating pediatric epileptic encephalopathy characterized by multiple intractable seizure types. Treatment of LGS is challenging because of the small number of antiepileptic drugs (AEDs) which are effective for this syndrome, as well as the need for polytherapy in the majority of patients. This review focuses on the treatment of LGS with rufinamide, a recently approved third-generation AED with reported efficacy as adjunctive therapy for LGS. All relevant papers identified through a PubMed search on the treatment of LGS with rufinamide were reviewed. To date, the literature suggests improvements in seizure frequency for pediatric patients with LGS on rufinamide. Rufinamide appears to be especially effective for atonic or drop attack seizures. Rufinamide also displays a favorable adverse event profile compared with the older anticonvulsants, as well as a minimal number of drug interactions, making it a promising option for the adjunctive treatment of seizures associated with LGS.

The first example of a significant active site conformational rearrangement in a carbonic anhydrase-inhibitor adduct: the carbonic anhydrase I-topiramate complex

Topiramate is a widely used antiepileptic drug, which has been demonstrated to act as an efficient weight loss agent. Since several studies have pointed out that is a potent in vitro inhibitor of several Carbonic anhydrase (CA) isozymes, it has been hypothesized that its anti-obesity properties could be ascribed to the inhibition of the CAs involved in de novo lipogenesis. Consequently, the study of the interactions of with all human CA isoforms represents an important step for the rational drug design of selective CA inhibitors to be used as anti-obesity drugs. In this paper we report the crystallographic structure of the adduct that forms with hCA I, showing for the first time a profound reorganization of the CA active site upon binding of the inhibitor. Moreover, a structural comparison with hCA II- and hCA VA- adducts, previously investigated, has been performed showing that a different H-bond network together with the movement of some amino acid residues in the active site may account for the different inhibition constants of toward these three CA isozymes.

The challenge of pain management in patients with myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction. The complexity of the disease and its treatments make MG patients particularly susceptible to adverse effects of drugs. MG is not a painful condition; however, as pain management armamentarium includes drugs from diverse pharmacological groups and with potential for drug-drug interactions, managing pain in patients with MG can be challenging. The underlying disease and the concomitant medications of each patient must be considered and the analgesic treatment individualized. This review presents an update on the various aspects of pain pharmacotherapy in patients with MG, focusing primarily on medications used to treat chronic pain. Drugs discussed are opioids, nonsteroidal anti-inflammatory drugs, antidepressants, anticonvulsants, muscle relaxants, benzodiazepines, intravenous magnesium, and local anesthetics. Drug interactions with agents used for MG treatment (acethylcholinesterase inhibitors, corticosteroids, immunosuppressants) and plasmapheresis are discussed. The clinical usefulness and limitations of each of the drug classes and agents are described.

Lacosamide as treatment for partial epilepsy: mechanisms of action, pharmacology, effects, and safety

Lacosamide (LCM) is a novel agent that has been developed as an antiepileptic drug. In vitro studies suggest that LCM modulates voltage-gated sodium channels by enhancing their slow inactivation. In addition, LCM seems to interact with collapsin-response mediator protein 2 and thus may mediate neuronal plasticity. LCM has an elimination half-life of 13 hours, no relevant protein binding, and does not induce or inhibit enzymes of the cytochrome P450 system. No clinically significant drug-drug interactions have been discovered as yet. Experimental data suggest anticonvulsant as well as analgesic effects. Large clinical studies have demonstrated its efficacy for treatment of patients with partial seizures. LCM is well tolerated, and the most common adverse events are unspecific central nervous system and gastrointestinal effects such as dizziness, vertigo, nausea, and headache. LCM is approved for treatment of partial seizures with or without secondary generalization in the United States and the European Union within a dose range of 200 to 400 mg per day, administered twice daily. In addition to the oral formulations, an intravenous infusion solution is available.

Onset of action and seizure control in Lennox-Gaustaut syndrome: focus on rufinamide

Lennox-Gaustaut syndrome is an electroclinical epilepsy syndrome characterized by the triad of electroencephalogram showing diffuse slow spike-and-wave discharges and paroxysmal fast activity, multiple intractable seizure types, and cognitive impairment. The intractability to seizure medications and cognitive impairment gives rise to eventual institutionalized patient care. Only a small subset of seizure medications has been shown to be helpful in seizure control. Most patients take up to 3 medications at high therapeutic dosing and are susceptible to medication-induced side effects. The lack of medication efficacy in seizure control has led one meta-analysis to conclude that there is no single medication that is highly efficacious in controlling seizures in this syndrome. On this background, a new and structurally novel seizure medication, rufinamide, has been found to be beneficial in the treatment of seizures in this syndrome. In a multicenter, double-blinded, randomized, placebo-controlled study, rufinamide was found to reduce seizures by over 30%. More importantly, it reduced the frequency of the seizure type that induces most of the morbidity of this syndrome, the drop seizure, by over 40%. There were few side effects, the medication was well tolerated, and in the open labeled extension study, tolerance was not found. In this review, we describe the main electroclinical features of Lennox-Gaustaut syndrome and summarize the few controlled studies that have contributed to its rational treatment. Currently, there is no single agent or combination of agents that effectively treat the multiple seizure types and co-morbidities in this syndrome. Our focus will be on the role of the new medication rufinamide in seizure reduction in patients with Lennox-Gaustaut syndrome.

Drug treatment of epilepsy in the century of the ILAE: the second 50 years, 1959-2009

The drug therapy of epilepsy evolved enormously in this 50 year period. Advances in therapeutics included the incorporation of pharmacokinetics into clinical practice, enormous advances in neurochemistry, a trend to antiepileptic drug monotherapy, better drug assessment, better understanding of therapeutic outcomes, and the recognition of the large epilepsy treatment gap in many countries. An unprecedented range of new drugs was introduced in this period. Before 1989, these included carbamazepine, valproate, ethosuximide, and the benzodiazepines. Since 1989, 13 more new drugs have been licensed and marketed and there are others in the pipeline. The International League Against Epilepsy and its leading figures have played an important role in these developments. In this period, too, there has been a rapid expansion in research and development within the pharmaceutical industry and a rise in the value of the antiepileptic drug market. In parallel, governmental regulation of pharmaceuticals has greatly increased. To what extent the overall prognosis of epilepsy has improved as a result of these activities is an interesting and perplexing question.

Nanotechnology for delivery of drugs to the brain for epilepsy

Epilepsy results from aberrant electrical activity that can affect either a focal area or the entire brain. In treating epilepsy with drugs, the aim is to decrease seizure frequency and severity while minimizing toxicity to the brain and other tissues. Antiepileptic drugs (AEDs) are usually administered by oral and intravenous routes, but these drug treatments are not always effective. Drug access to the brain is severely limited by a number of biological factors, particularly the blood-brain barrier, which impedes the ability of AEDs to enter and remain in the brain. To improve the efficacy of AEDs, new drug delivery strategies are being developed; these methods fall into the three main categories: drug modification, blood-brain barrier modification, and direct drug delivery. Recently, all three methods have been improved through the use of drug-loaded nanoparticles.