Comparative anticonvulsant and mechanistic profile of the established and newer antiepileptic drugs

Arbidol, an antiviral drug, identified as a sodium channel blocker with anticonvulsant activity

BACKGROUND AND PURPOSE

Sodium channel blockers (SCBs) have traditionally been utilized as anti-seizure medications by primarily targeting the inactivation process. In a drug discovery project aiming at finding potential anticonvulsants, we have identified arbidol, originally an antiviral drug, as a potent SCB. In order to evaluate its anticonvulsant potential, we have thoroughly examined its biophysical properties as well as its effects on animal seizure models.

EXPERIMENTAL APPROACH

Patch clamp recording was used to investigate the electrophysiological properties of arbidol, as well as the binding and unbinding kinetics of arbidol, carbamazepine and lacosamide. Furthermore, we evaluated the anticonvulsant effects of arbidol using three different seizure models in male mice.

KEY RESULTS

Arbidol effectively suppressed neuronal epileptiform activity by blocking sodium channels. Arbidol demonstrated a distinct mode of action by interacting with both the fast and slow inactivation of Nav1.2 channels compared with carbamazepine and lacosamide. A kinetic study suggested that the binding and unbinding rates might be associated with the specific characteristics of these three drugs. Arbidol targeted the classical binding site of local anaesthetics, effectively inhibited the gain-of-function effects of Nav1.2 epileptic mutations and exhibited varying degrees of anticonvulsant effects in the maximal electroshock model and subcutaneous pentylenetetrazol model but had no effect in the pilocarpine-induced status epilepticus model.

CONCLUSIONS AND IMPLICATIONS

Arbidol shows promising potential as an anticonvulsant agent, providing a unique mode of action that sets it apart from existing SCBs.

Anticonvulsant effects of cenobamate in chemically and electrically induced seizure models in rodents

Background

Cenobamate is an antiseizure medication used to treat partial-onset (focal) seizures. It is a molecule with one chiral center and a unique dual mechanism of action: enhancement of fast and slow inactivation of sodium channels with preferential inhibition of the persistent current and positive allosteric modulation of GABAA receptor-mediated ion channels.

Aims/Methods

Anticonvulsant effects of cenobamate (YKP3089; R-enantiomer), YKP3090 (S-enantiomer), and YKP1983 (racemate) were evaluated in chemically and electrically induced focal and generalized seizure models in rodents. The Genetic Absence Epilepsy Rat from Strasbourg (GAERS) model examined the effect of cenobamate on spike-wave seizures. Motor coordination was assessed with rotarod tests and minimal motor impairment exams.

Results

Early in development, cenobamate was found to have activity in focal and generalized seizure models in animals and was selected for continued development. Cenobamate prevented seizures in a dose-dependent manner, prevented seizure spread, and increased seizure threshold without potentiating seizure initiation or the development of tolerance to its anticonvulsant effects. In contrast, YKP3090 and YKP1983 were only effective against generalized tonic-clonic seizures. Cenobamate also protected mice from 6 Hz psychomotor-induced seizures. Cenobamate showed significant dose-dependent reductions in the number and cumulative duration of spike-and-wave discharges in the GAERS model.

Discussion

Cenobamate showed efficacy or efficacy signals in all animal models of epilepsy tested with a favorable risk-versus-benefit ratio, supporting its clinical use in the treatment of partial-onset (focal) seizures in adults and warranting further clinical research in generalized seizures and absence seizures.

Development and Validation of a Highly Sensitive and Rapid LC-MS3 Strategy to Determine Oxcarbazepine and Its Active Metabolite in the Serum of Patients with Epilepsy and Its Application in Therapeutic Drug Monitoring

A sensitive and rapid bioanalytical method based on the LC-triple-stage fragmentation (LC-MS³) strategy on a hybrid triple quadrupole-linear ion trap mass spectrometer in combination with protein precipitation extraction for sample pretreatment has been developed and validated for the simultaneous determination of the antiepileptic drug oxcarbazepine (OXC) and its main active metabolite (MHD) in human serum. The separation was performed on a Waters XBridge BEH C18 column (2.5 µm, 2.1 × 50 mm) in isocratic elution with 0.1% formic acid in water and methanol (50:50, v:v) as the mobile phase. The run time for each sample was 2.0 min. The calibration curves ranging from 25 to 1600 ng/mL for OXC and from 0.5 to 32 μg/mL for MHD showed correlation coefficients (r) better than 0.99. All of the validation data, such as precision, accuracy and other parameters, fit the requirements of the current bioanalytical method validation guidelines. The LC-MS³ method for quantitation of OXC and MHD was compared with the LC-MRM based method. Passing–Bablok regression coefficients and Bland–Altman plots showed that the developed LC–MS³ method is a reliable method for quantitative analysis of OXC and MHD. The proposed LC-MS³ method was successfully applied to determine the serum concentrations of OXC and MHD to support a clinical study.

Prospects for new drugs to treat binge-eating disorder: Insights from psychopathology and neuropharmacology

BACKGROUND

Binge-eating disorder (BED) is a common psychiatric condition with adverse psychological and metabolic consequences. Lisdexamfetamine (LDX) is the only approved BED drug treatment. New drugs to treat BED are urgently needed.

METHODS

A comprehensive review of published psychopathological, pharmacological and clinical findings.

RESULTS

The evidence supports the hypothesis that BED is an impulse control disorder with similarities to ADHD, including responsiveness to catecholaminergic drugs, for example LDX and dasotraline. The target product profile (TPP) of the ideal BED drug combines treating the psychopathological drivers of the disorder with an independent weight-loss effect. Drugs with proven efficacy in BED have a common pharmacology; they potentiate central noradrenergic and dopaminergic neurotransmission. Because of the overlap between pharmacotherapy in attention deficit hyperactivity disorder (ADHD) and BED, drug-candidates from diverse pharmacological classes, which have already failed in ADHD would also be predicted to fail if tested in BED. The failure in BED trials of drugs with diverse pharmacological mechanisms indicates many possible avenues for drug discovery can probably be discounted.

CONCLUSIONS

(1) The efficacy of drugs for BED is dependent on reducing its core psychopathologies of impulsivity, compulsivity and perseveration and by increasing cognitive control of eating. (2) The analysis revealed a large number of pharmacological mechanisms are unlikely to be productive in the search for effective new BED drugs. (3) The most promising areas for new treatments for BED are drugs, which augment noradrenergic and dopaminergic neurotransmission and/or those which are effective in ADHD.

What pharmacological interventions are effective in binge-eating disorder? Insights from a critical evaluation of the evidence from clinical trials

Binge-eating disorder (BED) is the commonest eating disorder and an important causal factor in obesity. Lisdexamfetamine is the only approved pharmacological treatment. Many drugs have been clinically evaluated and several were described as potentially promising treatments. A comprehensive reassessment of the evidence from these clinical trials has been performed. The questions to be answered were: (1) Does the evidence support claims of efficacy? (2) What pharmacological mechanisms show promise for developing new BED drugs? (3) What are the clinical implications for treating BED? PubMed and internal database searches identified every available published drug trial in BED. The trials and their results were summarised and reviewed to re-evaluate the evidence. Factors taken into consideration included psychiatric diagnosis, primary endpoint, secondary outcome measures, trial size, blinding and controls, drop-out rates, placebo response rates and weight-loss. Drugs were classified according to their pharmacology and therapeutic indication to determine which mechanisms were effective and to provide insights into the psychopathology of BED. For most drugs, robust evidence of efficacy in BED is insubstantial or absent. Some catecholaminergic drugs developed for ADHD are also effective in BED; other pharmacological mechanisms are weakly efficacious at best. Reducing BED severity has little impact on weight. Conversely, weight-loss from anti-obesity therapy is ineffective in ameliorating the psychopathological drivers of BED. (1) BED is a psychiatric not a metabolic disorder. (2) Weight-loss drugs are generally ineffective in BED. (3) Efficacy in BED is restricted to powerful catecholaminergic drugs. (4) Drugs acting via noradrenaline, 5-HT, GABA, carbonic anhydrase inhibition, opioid receptors and various ion channels are generally minimally effective at best. (5) Efficacy in BED is dependent on treating its core psychopathology; reducing impulsivity and compulsivity and increasing cognitive restraint over eating. (6) Obese subjects with BED may benefit from separate treatments for these two disorders.

The Anticonvulsant Lamotrigine Reduces Bout-Like Alcohol Drinking in Rats

We used an optical lickometer system to study drinking microstructure and effect of lamotrigine in voluntary alcohol-drinking rats. We showed that, similar to humans, animals differ by their drinking microstructure where some consume alcohol exclusively in a bout-like patterns. The study suggests that anticonvulsants, such as lamotrigine, may be one treatment strategy specifically affecting this type of drinking.

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.

α-Substituted Lactams and Acetamides: Ion Channel Modulators that Show Promise in Treating Drug-resistant Epilepsy

The two main problems in the pharmacotherapy of epilepsy are resistance to currently available first-line medications (which occurs in about one third of patients) and the high incidence of side effects. To address these two challenges, extensive efforts are being undertaken to design new, structurally distinct antiepileptic drugs with a broad spectrum of anticonvulsant activity. Tests in animal models of epilepsy indicate that α-substituted lactams and acetamides show a broad spectrum of anticonvulsant activity (including very promising activity in drug-resistant models) as well as an excellent safety profile. Limited clinical results confirm these preclinical findings. In the first part of this review, pharmacology and toxicology of α-substituted lactams and acetamides and their putative protein targets in the brain have been discussed. This is followed by a discussion of structure-activity relationships among α-alkyl-, α-aryl-, and α-aryl-α-alkyl-substituted derivatives. The most promising structures seem to be those related to 3-ethyl-3-phenylpyrrolidin-2-one, 2-phenylbutyramide, and 2- sec-butylvaleramide. The information presented in this review is expected to facilitate rational drug design and development efforts for α-substituted lactams and acetamides.

Evaluation of the impact of compound C11 a new anticonvulsant candidate on cognitive functions and hippocampal neurogenesis in mouse brain

Searching for the new and effective anticonvulsants in our previous study we developed a new hybrid compound C-11 derived from 2-(2,5-dioxopyrrolidin-1-yl) propanamide. C11 revealed high efficacy in acute animal seizure models such as the maximal electroshock model (MES), the pentylenetetrazole model (PTZ) and the 6 Hz (6 Hz, 32 mA) seizure model, as well as in the kindling model of epilepsy induced by repeated injection of PTZ in mice. In the aim of further in vivo C11 characterization, in the current studies we evaluated its influence on cognitive functions, neurodegeneration and neurogenesis process in mice after chronical treatment. All experiments were performed on 6 weeks old male C57/BL mice. The following drugs were used: C11, levetiracetam (LEV), ethosuximide (ETS) and lacosamide (LCM). We analyzed proliferation, migration and differentiation of newborn cells as well as neurodegenerative changes in a mouse brain after long-term treatment with aforementioned AEDs. Additionally, we evaluated changes in learning and memory functions in response to chronic C11, LEV, LCM and ETS treatment. C11 as well as LEV and ETS did not disturb the proliferation of newborn cells compared to the control mice, whereas LCM treatment significantly decreased it. Chronic AEDs therapy did not induce significant neurodegenerative changes. Behavioral studies with using Morris Water Maze test did not indicate any disturbances in the spatial learning and memory after C11 as well as LEV and ETS treatment in comparison to the control group except LCM mice where significant dysfunctions in time, distance and direct swim to the platform were observed. Interestingly, results obtained from in vivo MRI spectroscopy showed a statistically significant increase of one of the neurometabolites- N-acetyloaspartate (NAA) for LCM and LEV mice. A new hybrid compound C11 in contrast to LCM has no negative impact on the process of neurogenesis and neurodegeneration in the mouse hippocampus. Furthermore, chronic treatment with C11 turned out to have no negative impact on cognitive functions of treated mice, which, is certainly of great importance for further more advanced preclinical and especially clinical trials.

Studies on Anticonvulsant Effects of Novel Histamine H3R Antagonists in Electrically and Chemically Induced Seizures in Rats

A newly developed series of non-imidazole histamine H3 receptor (H3R) antagonists (1⁻16) was evaluated in vivo for anticonvulsant effects in three different seizure models in Wistar rats. Among the novel H3R antagonists examined, H3R antagonist 4 shortened the duration of tonic hind limb extension (THLE) in a dose-dependent fashion in the maximal electroshock (MES)-induced seizure and offered full protection against pentylenetetrazole (PTZ)-induced generalized tonic-clonic seizure (GTCS), following acute systemic administration (2.5, 5, 10, and 15 mg/kg, i.p.). However, only H3R antagonist 13, without appreciable protective effects in MES- and PTZ-induced seizure, fully protected animals in the strychnine (STR)-induced GTCS following acute systemic pretreatment (10 mg/kg, i.p.). Moreover, the protective effect observed with H3R antagonist 4 in MES-induced seizure was completely abolished when animals were co-administered with the H3R agonist (R)-α-methylhistamine (RAMH, 10 mg/kg, i.p.). However, RAMH failed to abolish the full protection provided by the H3R antagonist 4 in PTZ-induced seizure and H3R antagonist 13 in STR-induced seizure. Furthermore, in vitro antiproliferative effects or possible metabolic interactions could not be observed for compound 4. Additionally, the predictive in silico, as well as in vitro, metabolic stability for the most promising H3R antagonist 4 was assessed. The obtained results show prospective effects of non-imidazole H3R antagonists as innovative antiepileptic drugs (AEDs) for potential single use against epilepsy.

Anticonvulsant effect of anacardic acid in murine models: Putative role of GABAergic and antioxidant mechanisms

Epilepsy is a neurological disease affecting people of all ages worldwide. Side effects of antiepileptic drugs and their association with oxidative stress stimulate the search for new drugs, which would be more affordable with fewer adverse effects. Accordingly, the aim of the present work is to evaluate the anticonvulsant effect of anacardic acid (AA), a natural compound extracted from cashew liquid (Anacardium occidentalis), in murine models, as well as its antioxidant actions in Saccharomyces cerevisiae. AA (>90% purity) was tested, in vivo, in male Swiss mice (25-30 g) with four convulsive models, (1) pentylenetetrazole, (2) pilocarpine, (3) electroshock, and (4) kainic acid, at doses of 25, 50, and 100 mg/kg, body weight (B.W.) Additionally, the effective dose, toxic dose, and protective index studies were also performed. Results revealed that AA exhibits anticonvulsive effects in models 1, 3, and 4, with a mean effective dose (ED₅₀) of 39.64 (model 1) >100 mg/kg, B.W. (model 2), and 38.36 (model 3); furthermore, AA displays a protection index of 1.49 (model 1), <0.6 (model 2, and 1.54 (model 3). In addition, AA showed antioxidant activities in S. cerevisiae mutated for superoxide dismutases (SOD). In conclusion, these results show that AA exhibits significant anticonvulsant and antioxidant activities and may be used as a promising natural product for the treatment of epilepsy.

Anticonvulsant evaluation of novel non-imidazole histamine H3R antagonists in different convulsion models in rats

Novel non-imidazole histamine H3 receptor (H3R) antagonists (2-8) were developed and assessed for in-vitro antagonist binding affinities at the human histamine H1-H4R. These novel H3R antagonists (2-8) were examined in-vivo for anticonvulsant effects in three different convulsion models in male adult rats. Compound 6 significantly and dose-dependently exhibited decreased duration of tonic hind limb extension (THLE) in the maximal electroshock (MES)- and fully protected animals against pentylenetetrazole (PTZ)-induced convulsion, following acute systemic administration (5, 10, and 20 mg/kg, i.p.). Contrary, all compounds 2-8 showed moderate protection in the strychnine (STR)-induced convulsion model following acute pretreatment (10 mg/kg, i.p.). Moreover, the acute systemic administration of H3R antagonist 6 (10 mg/kg, i.p.) significantly prolonged latency time for MES convulsions. Furthermore, the anticonvulsant effect observed with compound 6 in MES-model was entirely abrogated when rats were co-injected with the brain penetrant H1R antagonist pyrilamine (PYR) but not the brain penetrant H2R antagonist zolantidine (ZOL). However, PYR and ZOL failed to abolish the full protection provided by the H3R antagonist 6 in PTZ- and STR-models. No mutagenic or antiproliferative effects or potential metabolic interactions were shown for compound 6 when assessing its antiproliferative activities and metabolic profiling applying in-vitro methods. These findings demonstrate the potential of non-imidazole H3R antagonists as novel antiepileptic drugs (AEDs) either for single use or in addition to currently available epilepsy medications.

Treatment Strategies for Dravet Syndrome

Dravet syndrome (DS) is a medically refractory epilepsy that onsets in the first year of life with prolonged seizures, often triggered by fever. Over time, patients develop other seizure types (myoclonic, atypical absences, drops), intellectual disability, crouch gait and other co-morbidities (sleep problems, autonomic dysfunction). Complete seizure control is generally not achievable with current therapies, and the goals of treatment are to balance reduction of seizure burden with adverse effects of therapies. Treatment of co-morbidities must also be addressed, as they have a significant impact on the quality of life of patients with DS. Seizures are typically worsened with sodium-channel agents. Accepted first-line agents include clobazam and valproic acid, although these rarely provide adequate seizure control. Benefit has also been noted with stiripentol, topiramate, levetiracetam, the ketogenic diet and vagal nerve stimulation. Several agents presently in development, specifically fenfluramine and cannabidiol, have shown efficacy in clinical trials. Status epilepticus is a recurring problem for patients with DS, particularly in their early childhood years. All patients should be prescribed a home rescue therapy (usually a benzodiazepine) but should also have a written seizure action plan that outlines when rescue should be given and further steps to take in the local hospital if the seizure persists despite home rescue therapy.

Treatment with lacosamide impedes generalized seizures in a rodent model of cortical dysplasia

OBJECTIVE

Epilepsy is a common neurologic disorder resulting in spontaneous, recurrent seizures. About 30-40% of patients are not responsive to pharmacologic therapies. This may be due to the differences between individual patients such as etiology, underlying pathophysiology, and seizure focus, and it highlights the importance of new drug discovery and testing in this field. Our goal was to determine the efficacy of lacosamide (LCM), a drug approved for the treatment of focal seizures, in a model of generalized epilepsy with cortical dysplasia (CD). We sought to compare LCM to levetiracetam (LEV), a drug that is currently used for the treatment of both partial and generalized epilepsy and to test its proficiency.

METHODS

Pregnant rats were irradiated to produce pups with malformed cortices in a model of CD, which will be referred to as the "first hit." Adult animals, developed normally (NL) and irradiated (XRT), were surgically implanted with electroencephalography (EEG) electrodes. Baseline EEG was recorded on all rats prior to pretreatments with either LCM, LEV, or placebo (PBO). After 30 min, all rats were injected with a subconvulsive dose of pentylenetetrazole (PTZ), a γ-aminobutyric acid receptor A (GABA_A ) antagonist used to provoke generalized seizures as a "second hit."

RESULTS

LCM and LEV were both effective against seizures induced by PTZ. XRT rats had a higher seizure incidence with longer and more severe seizures than NL rats. Seizure duration was decreased with both LCM and LEV in all animals. In XRT rats, there was a significant reduction in acute seizure incidence and severity with both LCM and LEV after PTZ injection.

SIGNIFICANCE

Our results suggest that LCM could be used as a potential treatment option for generalized epilepsy with CD as the underlying pathology.

The genotoxic effect of oxcarbazepine on mice blood lymphocytes

This study was conducted to assess the amount of DNA damage caused by Oxcarbazepine (OXC) through single cell gel electrophoresis (SCGE) technique/comet assay. OXC derived from dibenzazepine series is an effective second generation antiepileptic drug (AED) for both children and adults. Side effects like genotoxic effects of AEDs are of prime importance resulting from toxic metabolites, free radicals and reactive oxygen species (ROS). Forty Eight adult male Bagg's albino mice (BALB/c) were randomly classified into eight groups, each comprising of six animals. Two of these groups were control and six were tested groups. Control groups were injected with 1% tween 80 while tested groups were injected with 10, 20, and 40 mg/kg-day OXC for seven days (acute therapy) and 28 days (subchronic therapy) in peritoneal cavity. Blood samples were collected by cardiac puncture and subjected to comet assay for the analysis of DNA damage. Per sample 100 cells were scored and classified according to comet tail length. The results showed that OXC in acute and long term therapies had significantly higher (p < 0.05) genotoxicity in treated groups as compared to control groups. Our study suggests that OXC may cause significant DNA damage in both acute as well as in subchronic therapies.

Animal Models of Seizures and Epilepsy: Past, Present, and Future Role for the Discovery of Antiseizure Drugs

The identification of potential therapeutic agents for the treatment of epilepsy requires the use of seizure models. Except for some early treatments, including bromides and phenobarbital, the antiseizure activity of all clinically used drugs was, for the most part, defined by acute seizure models in rodents using the maximal electroshock and subcutaneous pentylenetetrazole seizure tests and the electrically kindled rat. Unfortunately, the clinical evidence to date would suggest that none of these models, albeit useful, are likely to identify those therapeutics that will effectively manage patients with drug resistant seizures. Over the last 30 years, a number of animal models have been developed that display varying degrees of pharmacoresistance, such as the phenytoin- or lamotrigine-resistant kindled rat, the 6-Hz mouse model of partial seizures, the intrahippocampal kainate model in mice, or rats in which spontaneous recurrent seizures develops after inducing status epilepticus by chemical or electrical stimulation. As such, these models can be used to study mechanisms of drug resistance and may provide a unique opportunity for identifying a truly novel antiseizure drug (ASD), but thus far clinical evidence for this hope is lacking. Although animal models of drug resistant seizures are now included in ASD discovery approaches such as the ETSP (epilepsy therapy screening program), it is important to note that no single model has been validated for use to identify potential compounds for as yet drug resistant seizures, but rather a battery of such models should be employed, thus enhancing the sensitivity to discover novel, highly effective ASDs. The present review describes the previous and current approaches used in the search for new ASDs and offers some insight into future directions incorporating new and emerging animal models of therapy resistance.

Astrocytic GABA Transporters: Pharmacological Properties and Targets for Antiepileptic Drugs

Inactivation of GABA-mediated neurotransmission is achieved by high-affinity transporters located at both GABAergic neurons and the surrounding astrocytes. Early studies of the pharmacological properties of neuronal and glial GABA transporters suggested that different types of transporters might be expressed in the two cell types, and such a scenario was confirmed by the cloning of four distinctly different GABA transporters from a number of different species. These GABA-transport entities have been extensively characterized using a large number of GABA analogues of restricted conformation, and several of these compounds have been shown to exhibit pronounced anticonvulsant activity in a variety of animal seizure models. As proof of concept of the validity of this drug development approach, one GABA-transport inhibitor, tiagabine, has been developed as a clinically active antiepileptic drug. This review provides a detailed account of efforts to design new subtype-selective GABA-transport inhibitors aiming at identifying novel antiepileptic drug candidates.

Formulation and evaluation of transdermal drug delivery of topiramate

Background:

Transdermal drug delivery system (TDDS) was designed to sustain the release and improve the bioavailability of drug and patient compliance. Among the various types of transdermal patches, matrix dispersion type systems disperse the drug in the solvent along with the polymers and solvent is allowed to evaporate forming a homogeneous drug-polymer matrix. The objective of the present study was to design and formulate TDDS of topiramate (TPM) and to evaluate their extended release in vitro and ex vivo.

Materials and Methods:

In the present study, an attempt has been made to develop a matrix-type transdermal therapeutic system comprising TPM with different ratios of hydrophilic and hydrophobic polymeric combinations using solvent casting technique.

Results:

The physicochemical compatibility of the drug and the polymers was studied by Fourier transform infrared spectroscopy. The results obtained showed no physical-chemical incompatibility between the drug and the polymers. The patches were further subjected to various physical evaluations along with the ex vivo permeation studies using pig ear skin.

Conclusions:

On the basis of results obtained from the physical evaluation and ex vivo studies the patches containing the polymers, that is, Eudragit L 100 and polyvinylpyrrolidone, with oleic acid as the penetration enhancer were considered as the best formulations for the transdermal delivery of TPM.

Non-imidazole-based histamine H3 receptor antagonists with anticonvulsant activity in different seizure models in male adult rats

A series of twelve novel non-imidazole-based ligands (3–14) was developed and evaluated for its in vitro binding properties at the human histamine H3 receptor (hH3R). The novel ligands were investigated for their in vivo protective effects in different seizure models in male adult rats. Among the H3R ligands (3–14) tested, ligand 14 showed significant and dose-dependent reduction in the duration of tonic hind limb extension in maximal electroshock (MES)-induced seizure model subsequent to acute systemic administration (5, 10, and 20 mg/kg, intraperitoneally), whereas ligands 4, 6, and 7 without appreciable protection in MES model were most promising in pentylenetetrazole (PTZ) model. Moreover, the protective effect observed for ligand 14 in MES model was lower than that observed for the reference drug phenytoin and was entirely abrogated when rats were co-administered with the brain-penetrant H1R antagonist pyrilamine (PYR) but not the brain-penetrant H2R antagonist zolantidine (ZOL), demonstrating that histaminergic neurotransmission by activation of postsynaptically located H1Rs seems to be involved in the protective action. On the contrary, PYR and ZOL failed to abrogate the full protection provided by 4 in PTZ model and the moderate protective effect by 14 in strychnine (STR) model. Moreover, the experimental and in silico estimation of properties such as metabolism was performed for five selected test compounds. Also, lipophilicity using planar reversed-phase thin-layer chromatography method was included for better understanding of the molecular properties of the tested compounds. Additionally, the absorption, distribution, metabolism, and elimination and toxicity parameters were evaluated for the most promising compounds 2, 4, 6, 7, and 14 utilizing in vitro methods. These interesting results highlight the potential of H3R ligands as new antiepileptic drugs or as adjuvants to available epilepsy medications.

Anticonvulsant Use in Treating Dementia-Related Agitation

Dementia is often accompanied by disturbances in behavior which require treatment with medications. Traditionally, antipsychotics and benzodiazepines have been used. Their modest beneficial effects must be balanced against toxicities such as drug-induced parkinsonism which leads to falls, and worsened cognitive function. Anticonvulsant medications have been used in the past to treat agitated and aggressive behaviors from various conditions. Recent reports attest to their usefulness in treating behavioral problems secondary to dementia. Carbamazepine and divalproex sodium have proven effective in treatment while newer agents like gabapentin may be useful as well. These agents may be preferable because they target a broad variety of symptoms and diseases, are less likely to induce extrapyramidal reactions and some have a low drug interaction profile.

Evaluating the safety and efficacy of felbamate in the context of a black box warning: A single center experience

INTRODUCTION

Felbamate was approved in 1993 to treat partial seizures with and without secondary generalization in adults and in Lennox-Gastaut Syndrome in children. Its use was later restricted when rare but fatal cases of aplastic anemia and hepatic failure were identified.

METHODS

This single center analysis retrospectively evaluated the safety and efficacy of felbamate in a cohort of children, adolescents, and adults with epilepsy.

RESULTS

A chart review identified 103 patients taking felbamate. The range of felbamate dose was 300-4500 mg (mean: 1800 ± 900 mg). The duration of therapy ranged from 1 month to 20 years (mean duration: 35 ± 45 months). Eighteen (17.5%) subjects experienced adverse events including insomnia, nausea, vomiting, decreased appetite, weight loss, gastric discomfort, diarrhea, mood and behavioral problems, high blood pressure, headache, and elevated liver enzymes. Out of these, 6 (5.9%) patients discontinued the therapy. No hepatic failure or agranulocytosis was observed. Fifty-nine (57.72%) patients achieved ≥ 50% reduction in seizure frequency, and 30 (29.12%) patients achieved seizure freedom.

CONCLUSIONS

These findings suggest that felbamate is safe, well tolerated, and effective in treatment of various types of epilepsy syndromes.

Influence of MPEP (a selective mGluR5 antagonist) on the anticonvulsant action of novel antiepileptic drugs against maximal electroshock-induced seizures in mice

The aim of this study was to determine the effects of 2-methyl-6-(phenylethynyl)pyridine (MPEP - a selective antagonist for the glutamate metabotropic receptor subtype mGluR5) on the protective action of some novel antiepileptic drugs (lamotrigine, oxcarbazepine, pregabalin and topiramate) against maximal electroshock-induced seizures in mice. Brain concentrations of antiepileptic drugs were measured to determine whether MPEP altered pharmacokinetics of antiepileptic drugs. Intraperitoneal injection of 1.5 and 2mg/kg of MPEP significantly elevated the threshold for electroconvulsions in mice, whereas MPEP at a dose of 1mg/kg considerably enhanced the anticonvulsant activity of pregabalin and topiramate, but not that of lamotrigine or oxcarbazepine in the maximal electroshock-induced seizures in mice. Pharmacokinetic results revealed that MPEP (1mg/kg) did not alter total brain concentrations of pregabalin and topiramate, and the observed effect in the mouse maximal electroshock seizure model was pharmacodynamic in nature. Collectively, our preclinical data suggest that MPEP may be a safe and beneficial adjunct to the therapeutic effects of antiepileptic drugs in human patients.

Successful Treatment of Electrographic Status Epilepticus of Sleep With Felbamate in a Patient With SLC9A6 Mutation

BACKGROUND

Mutations of SLC9A6 may cause an X-linked clinical syndrome first described by Christianson in 1999 in which affected males exhibited profound intellectual disability, autism, drug-resistant epilepsy, ophthalmoplegia, mild craniofacial dysmorphism, microcephaly, and ataxia.

METHODS

We describe a child with an SLC9A6 mutation and an electroencephalographic pattern consistent with electrographic status epilepticus of sleep.

RESULTS

Our patient's electrographic status epilepticus of sleep resolved after treatment with felbamate. Following treatment, he remained seizure-free but did not make significant or lasting gains in language.

CONCLUSION

Our report extends the clinical epilepsy phenotype in children with SLC9A6 mutations to include electrographic status epilepticus of sleep. In addition, felbamate was an effective treatment for electrographic status epilepticus of sleep in our patient.

Efficacy and Safety of Topiramate for Essential Tremor: A Meta-Analysis of Randomized Controlled Trials

Essential tremor (ET) is the most common movement disorder that is frequently treated by propranolol or primidone. However, 30% of patients with ET do not respond to either propranolol or primidone. The objective of this study was to assess the efficacy and safety of topiramate for ET.We searched the MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials for relevant randomized controlled trials on the effects of topiramate for ET. A meta-analysis technique was applied to estimate the efficacy and safety of topiramate. The primary outcome was the change in the Fahn-Tolosa-Marin tremor rating scale (TRS). The secondary outcomes included the respective change in the location, motor tasks/function and function disability scores, and adverse events.We included 3 randomized controlled trials with a total of 294 participants. Topiramate was significantly better than placebo in reducing TRS of patients with ET (mean difference [MD] -8.58, 95% confidence interval [CI] -15.46 to -1.70). Changes from the scales of upper limb tremor severity (MD -5.12, 95% CI -7.79 to -2.45), motor tasks/function (MD -5.07, 95% CI -7.12 to -3.03), and functional disability (MD -4.72, 95% CI -6.77 to -2.67) were significantly greater with topiramate than with placebo. More participants taking topiramate experienced adverse events leading to withdrawal than those taking placebo (risk difference 19%, 95% CI 11%-27%).There is consistent evidence supporting the efficacy of topiramate in treating ET; however, a significant proportion of participants withdrew due to its adverse effects.

International Veterinary Epilepsy Task Force consensus proposal: medical treatment of canine epilepsy in Europe

In Europe, the number of antiepileptic drugs (AEDs) licensed for dogs has grown considerably over the last years. Nevertheless, the same questions remain, which include, 1) when to start treatment, 2) which drug is best used initially, 3) which adjunctive AED can be advised if treatment with the initial drug is unsatisfactory, and 4) when treatment changes should be considered. In this consensus proposal, an overview is given on the aim of AED treatment, when to start long-term treatment in canine epilepsy and which veterinary AEDs are currently in use for dogs. The consensus proposal for drug treatment protocols, 1) is based on current published evidence-based literature, 2) considers the current legal framework of the cascade regulation for the prescription of veterinary drugs in Europe, and 3) reflects the authors' experience. With this paper it is aimed to provide a consensus for the management of canine idiopathic epilepsy. Furthermore, for the management of structural epilepsy AEDs are inevitable in addition to treating the underlying cause, if possible.

Enteral topiramate in a pediatric patient with refractory status epilepticus: a case report and review of the literature

We describe the use of topiramate in a healthy 12-year-old (88-kg) male who developed refractory generalized convulsive status epilepticus. Seizures persisted despite aggressive use of benzodiazepines (intravenous lorazepam; oral clorazepate), barbiturates (i.e., phenobarbital, pentobarbital), and hydantoins. The child's seizures were controlled with nasogastrically administered topiramate in doses up to 500 mg twice daily (11.4 mg/kg/day). The patient did not display any clinical or laboratory signs of metabolic acidosis while receiving topiramate. Topiramate should be considered as a treatment option in refractory status epilepticus.

Levetiracetam accelerates the onset of supply rate depression in synaptic vesicle trafficking

OBJECTIVE

To determine if levetiracetam (LEV) enhances the impact in excitatory presynaptic terminals of a rate-limiting mechanism in vesicle trafficking termed supply rate depression that emerges to limit synaptic transmission during heavy, epileptiform use.

METHODS

The effect of LEV was measured with electrophysiologic assays of monosynaptic connections in ex vivo hippocampal slices from wild-type and synapsin knockout mice, and in primary cell culture neurons from wild-type and synaptic vesicle glycoprotein 2a (SV2a) knockout mice.

RESULTS

LEV enhanced the impact of supply rate depression at Schaffer collateral synapses by shortening the time course for induction. The LEV effect was selective for supply rate depression because other presynaptic vesicle trafficking mechanisms were not affected. The half maximal effective concentration (EC50 ) was ~50 μm. The maximal effect was ~15% and occurred at 100 μm, which is a clinically relevant concentration. An experimental protocol is established for distinguishing atypical antiepileptic drugs (AEDs) that affect supply rate depression, such as LEV, from typical AEDs, such as carbamazepine, that affect upstream mechanisms. The LEV effect was abolished at synapses from knockout mice lacking SV2a and from synapses lacking synapsin 1 and 2.

SIGNIFICANCE

The findings are consistent with the new hypothesis that LEV acts to treat epilepsy by accelerating the induction of supply rate depression at excitatory synapses during incipient epileptic activity. The absence of the effect in the knockouts confirms that presynaptic function is the target. More specifically, the absence in SV2a knockouts is consistent with previous binding studies suggesting that SV2a is the target for LEV. The absence in synapsin knockouts indicates that the phenotypic target intersects with the biochemical pathway that is altered in synapsin knockouts. The results from synapsin knockouts additionally suggest that development of functional analogs with increased potency might be possible because induction of supply rate depression is faster in synapsin knockouts compared to wild-type synapses treated with LEV.

Synthesis and anticonvulsant activity of novel purine derivatives

A series of new purines containing triazole and other heterocycle substituents was synthesized and evaluated for their preliminary anticonvulsant activity and neurotoxicity by using the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) and rotarod neurotoxicity (TOX) tests. Among the compounds studied, 9-decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5e) was the most potent compound, with a median effective dose of 23.4 mg/kg and a high protective index of more than 25.6 after intraperitoneal administration in mice. Compound 5e showed significant oral activity against MES-induced seizures in mice, with an ED50 of 39.4 mg/kg and a PI above 31.6. These results demonstrate that compound 5e possesses better anticonvulsant activity and is safer than the commercially available drugs carbamazepine and valproate in MES, scPTZ and TOX models.

SKF-96365 strongly inhibits voltage-gated sodium current in rat ventricular myocytes

SKF-96365 (1-(beta-[3-(4-methoxy-phenyl) propoxy]-4-methoxyphenethyl)-1H-imidazole hydrochloride) is a general TRPC channel antagonist commonly used to characterize the potential functions of TRPC channels in cardiovascular system. Recent reports showed that SKF-96365 induced a reduction in cardiac conduction. The present study investigates whether the reduced cardiac conduction caused by SKF-96365 is related to the blockade of voltage-gated sodium current (I Na) in rat ventricular myocytes using the whole-cell patch voltage-clamp technique. It was found that SKF-96365 inhibited I Na in rat ventricular myocytes in a concentration-dependent manner. The compound (1 μM) negatively shifted the potential of I Na availability by 9.5 mV, increased the closed-state inactivation of I Na, and slowed the recovery of I Na from inactivation. The inhibition of cardiac I Na by SKF-96365 was use-dependent and frequency-dependent, and the IC₅₀ was decreased from 1.36 μM at 0.5 Hz to 1.03, 0.81, 0.61, 0.56 μM at 1, 2, 5, 10 Hz, respectively. However, the selective TRPC3 antagonist Pyr3 decreased cardiac I Na by 8.5% at 10 μM with a weak use and frequency dependence. These results demonstrate that the TRPC channel antagonist SKF-96365 strongly blocks cardiac I Na in use-dependent and frequency-dependent manners. Caution should be taken for interpreting the alteration of cardiac electrical activity when SKF-96365 is used in native cells as a TRPC antagonist.

Anticonvulsant profile of 2-ethylthio-7-methyl-4-(4-methylphenyl)pyrazolo[1,5-a][1,3,5]triazine

This work evaluates the central nervous effects in ICR strain mice of 2-ethylthio-7-methyl-4-(4-methylphenyl)pyrazolo[1,5-a][1,3,5]triazine (MH4b1), a compound obtained by an efficient one-step reaction of S,S-diethyl 4-methylbenzoylimidodithiocarbonate with 5-amino-3-methyl-1H-pyrazole, in order to assess its neuro-pharmacological profile. The tests applied were: maximal electroshock seizure (MES), pentylenetetrazole (PTZ) seizures, forced swimming, plus maze, marble burying, sleeping time, rota-rod and catalepsy. In addition, MH4b1 binding to the benzodiazepine site of the GABA-A receptor and MH4b1 inhibition of monoamine oxidase (MAO) subtypes A and B were evaluated. MH4b1 showed anticonvulsant effects in a dose dependent manner (30-300 mg/kg, p.o.) against MES and inhibition of MAO-B (IC50: 24.5 µM) without activity at the benzodiazepine site. These data suggest that MH4b1 has anticonvulsant properties related to MAO-B inhibition.

Effects of WIN 55,212-2 mesylate on the anticonvulsant action of lamotrigine, oxcarbazepine, pregabalin and topiramate against maximal electroshock-induced seizures in mice

The aim of this study was to determine the effect of WIN 55,212-2 mesylate (WIN - a non-selective cannabinoid CB1 and CB2 receptor agonist) on the protective action of four second-generation antiepileptic drugs (lamotrigine, oxcarbazepine, pregabalin and topiramate) in the mouse maximal electroshock seizure model. Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2s stimulus duration) delivered via auricular electrodes. Drug-related adverse effects were ascertained by use of the chimney test (evaluating motor performance), the step-through passive avoidance task (assessing long-term memory) and the grip-strength test (evaluating skeletal muscular strength). Total brain concentrations of antiepileptic drugs were measured by high-pressure liquid chromatography to ascertain any pharmacokinetic contribution to the observed antiseizure effect. Results indicate that WIN (5mg/kg, i.p.) significantly enhanced the anticonvulsant action of lamotrigine (P<0.05), pregabalin (P<0.001) and topiramate (P<0.05), but not that of oxcarbazepine in the maximal electroshock-induced tonic seizure test in mice. Furthermore, none of the investigated combinations of WIN with antiepileptic drugs were associated with any concurrent adverse effects with regards to motor performance, long-term memory or muscular strength. Pharmacokinetic characterization revealed that WIN had no impact on total brain concentrations of lamotrigine, oxcarbazepine, pregabalin and topiramate in mice. These preclinical data would suggest that WIN in combination with lamotrigine, pregabalin and topiramate is associated with beneficial anticonvulsant pharmacodynamic interactions in the maximal electroshock-induced tonic seizure test.

Anticonvulsant action of indazole

Here we report that indazole is characterized as a potential anticonvulsant, inhibiting pentylenetetrazole-, electroshock- and strychnine-induced convulsions in mice (ED50's: 39.9, 43.2 and 82.4 mg/kg, respectively) but not bicuculline- and picrotoxin-induced convulsions. The median toxic dose (TD(50)) of indazole was 52.3 mg/kg by the minimal motor impairment test. Therefore, nontoxic doses produced anticonvulsant activity against pentylenetetrazole- and electroshock-induced seizures. Indazole (50 mg/kg) had no effect on spontaneous activity but induced hypothermia. It also inhibited the metabolism of dopamine and 5-hydroxytryptamine in the brain in vivo and the activities of monoamine oxidase A and B in vitro, with IC(50) values of 20.6 μM and 16.3 μM, respectively. However, these inhibitory effects do not account for the anticonvulsant activity because treatment with typical monoamine oxidase inhibitors such as pargyline or tranylcypromine did not completely reproduce the anticonvulsant activity of indazole. In the animal seizure models tested, the anticonvulsant profile of indazole most resembled that of gabapentin and somewhat resembled those of the AMPA/kainate antagonist NBQX and the sodium channel inhibitor phenytoin, but differed from that of benzodiazepine. The isobolographic analyses showed that the interactive mode of indazole with gabapentin, NBQX or phenytoin is additive. These results suggest that indazole has anticonvulsant activity and multiple mechanisms.

Combined carbamazepine and pregabalin therapy in a rat model of neuropathic pain

BACKGROUND

Carbamazepine and pregabalin have proven effects against neuropathic pain. Carbamazepine blocks voltage-dependent Na(+) channels, whereas pregabalin blocks voltage-dependent Ca(2+) channels. The authors hypothesized that the co-administration of these drugs would synergistically reduce neuropathic pain.

METHODS

Neuropathic pain was induced by L5 nerve ligation in Sprague-Dawley rats. To determine their ED(50) values, carbamazepine and pregabalin were orally administered at 0.3, 3, 10, or 30 mg kg(-1). The drugs were then co-administered at 0, 1/4×ED(50), 1/2×ED(50), 1.5×ED(50), and 2×ED(50) to determine the ED(50) and ED(75) values of the drugs in combination. Allodynia was determined using the von Frey hair test and dose-effect curves and isobolograms were used to investigate drug interactions. Levels of the acute reactive protein c-Fos in the dorsal horn were evaluated as an indicator of pathological nerve excitation.

RESULTS

At ED(50) levels, carbamazepine and pregabalin did not exhibit synergism, but doses higher than ED(75) were found to be synergistic. The combination index was 0.18 (strong synergy) and dose reductions were 35.7-fold for carbamazepine and 6.8-fold for pregabalin when co-administered when compared with a single administration at ED(75). The percentage allodynia relief was only 60% for carbamazepine and 80% for pregabalin by single administration, whereas their co-administration relieved allodynia by 100%. Furthermore, treatment decreased c-Fos expression in the dorsal horn, but expressional differences between animals treated with carbamazepine plus pregabalin were not significantly different from those treated with single drug.

CONCLUSIONS

Carbamazepine and pregabalin ameliorate neuropathic pain synergistically at higher doses.

Clinical pattern and associations of oxaliplatin acute neurotoxicity: a prospective study in 170 patients with colorectal cancer

BACKGROUND

The objective of the current prospective, multicenter, international study was to trace the incidence and severity of acute oxaliplatin-induced peripheral neuropathy (OXLIPN) and to determine its clinical pattern. The authors also specifically tested whether patients who had more symptoms of acute OXLIPN eventually would develop a more severe chronic, cumulative form of OXLIPN.

METHODS

One hundred seventy patients (mean ± standard deviation age, 63.7 ± 8.7 years) who were scheduled to receive either combined leucovorin, 5-fluoruracil, and oxaliplatin (FOLFOX) or combined capecitabine and oxaliplatin (XELOX) for metastatic colorectal cancer were monitored prospectively at baseline and were followed in 4 European sites. The incidence of hyperexcitability symptoms secondary to acute OXLIPN was assessed by using a descriptive questionnaire (yes/no question) at each clinical evaluation. Motor and neurosensory criteria according to version 3 of the National Cancer Institute's Common Toxicity Criteria were applied to clinically grade the severity of OXLIPN.

RESULTS

Acute OXLIPN was present in 146 of 170 patients (85.9%). The vast majority of these patients manifested cold-induced perioral (95.2%) or pharyngolaryngeal (91.8%) dysesthesias. Severe acute OXLIPN that required prolongation of oxaliplatin infusion from 2 hours to 4 to 6 hours occurred in 32 of 146 patients (21.9%). The increased number of acute OXLIPN symptoms was correlated significantly (Spearman rho correlation coefficient [r]) with both the development (r = 0.602; P < .001) and the degree of the chronic, cumulative form (r = 0.702; P < .001).

CONCLUSIONS

The current results indicated that the vast majority of patients with colorectal cancer who receive oxaliplatin-based chemotherapy will manifest symptoms of a transient acute syndrome soon after oxaliplatin administration. Patients who have a more complex combination of acute phenomena related to axonal hyperexcitability are those who eventually develop more severe OXLIPN. Therefore, it may be advisable to test agents against acute OXLIPN to verify their effects on the chronic form.

Receptor targets for antidepressant therapy in bipolar disorder: an overview

The treatment of bipolar depression is one of the most challenging issues in contemporary psychiatry. Currently only quetiapine and the olanzapine-fluoxetine combination are officially approved by the FDA against this condition. The neurobiology of bipolar depression and the possible targets of bipolar antidepressant therapy remain relatively elusive. We performed a complete and systematic review to identify agents with definite positive or negative results concerning efficacy followed by a second systematic review to identify the pharmacodynamic properties of these agents. The comparison of properties suggests that the stronger predictors for antidepressant efficacy in bipolar depression were norepinephrine alpha-1, dopamine D1 and histamine antagonism, followed by 5-HT2A, muscarinic and dopamine D2 and D3 antagonism and eventually by norepinephrine reuptake inhibition and 5HT-1A agonism. Serotonin reuptake which constitutes the cornerstone in unipolar depression treatment does not seem to play a significant role for bipolar depression. Our exhaustive review is compatible with a complex model with multiple levels of interaction between the major neurotransmitter systems without a single target being either necessary or sufficient to elicit the antidepressant effect in bipolar depression.

Acute seizure tests in epilepsy research: electroshock- and chemical-induced convulsions in the mouse

Epilepsy is a common (50 million patients worldwide) neurological disorder characterized by seizures that are caused by episodic abnormal electrical activity in the brain. Animal models play an essential role in epilepsy research including the discovery and development of new antiepileptic drugs. Described in this unit are protocols for traditional acute tests in which seizures are induced by either an electrical stimulation or a convulsant agent in non-epileptic mice. Specifically, protocols for the following acute seizure tests are provided: the maximal electroshock induced test (MES), the maximal electroshock seizure threshold (MEST) test, the 6-Hz seizure test, the subcutaneous pentylenetetrazol (s.c. PTZ) seizure test, and the intravenous pentylenetetrazol (i.v. PTZ) seizure test. These tests can be used to characterize anticonvulsant and/or proconvulsant properties of compounds in mice. The MES, s.c. PTZ, and 6-Hz seizure tests represent the three most widely used animal tests in drug-screening programs. Although the parameters of these tests are optimized for mice, the same tests (except for the 6-Hz seizure test), with some modifications, can be used with rats.

Preclinical antiepileptic actions of selective serotonin reuptake inhibitors--implications for clinical trial design

Selective serotonin reuptake inhibitors (SSRIs) can reduce seizure frequency in humans, but no large-scale clinical trials have been done to test the utility of SSRIs as potential antiepileptic drugs. This may be caused in part by a small number of reports on seizures triggered by SSRI treatment. The preclinical literature on SSRIs is somewhat conflicting, which is likely to contribute to the hesitance in accepting SSRIs as possible anticonvulsant drug therapy. A careful review of preclinical studies reveals that SSRIs appear to have region-specific and seizure subtype-specific effects, with models of chronic partial epilepsy being more likely to respond than models of acute generalized seizures. Moreover, this preclinical profile is similar to that of clinical antiepileptic drugs. These observations suggest that SSRIs are promising antiepileptic agents, and that clinical trials may benefit from defining patient groups according to the underlying pathology.

Anticonvulsant drugs, brain glutamate dehydrogenase activity and oxygen consumption

Glutamate dehydrogenase (GDH, E.C. 1.4.1.3.) is a key enzyme for the biosynthesis and modulation of glutamate (GLU) metabolism and an indirect γ-aminobutyric acid (GABA) source, here we studied the effect of anticonvulsants such as pyridoxal phosphate (PPAL), aminooxyacetic acid (AAOA), and hydroxylamine (OHAMINE) on GDH activity in mouse brain. Moreover, since GLU is a glucogenic molecule and anoxia is a primary cause of convulsions, we explore the effect of these drugs on oxygen consumption. Experiments were performed in vitro as well as in vivo for both oxidative deamination of GLU and reductive amination of α-ketoglutarate (αK). Results in vitro showed that PPAL decreased oxidative deamination of GLU and oxygen consumption, whereas AAOA and OHAMINE inhibited GDH activity competitively and also inhibited oxygen consumption when αK reductive amination was carried out. In contrast, results showed that in vivo, all anticonvulsants enhanced GLU utilization by GDH and also decreased oxygen consumption. Together, results suggest that GDH activity has repercussions on oxygen consumption, which may indicate that the enzyme activity is highly regulated by energy requirements for metabolic activity. Besides, GDH may participate in regulation of GLU and, indirectly GABA levels, hence in neuronal excitability, becoming a key enzyme in seizures mechanism.

Involvement of GABAergic and glutamatergic systems in the anticonvulsant activity of 3-alkynyl selenophene in 21 day-old rats

In this study, we investigated the role of GABAergic and glutamatergic systems in the anticonvulsant action of 3-alkynyl selenophene (3-ASP) in a pilocarpine (PC) model of seizures. To this purpose, 21 day-old rats were administered with an anticonvulsant dose of 3-ASP (50 mg/kg, per oral, p.o.), and [(3)H]γ-aminobutyric acid (GABA) and [(3)H]glutamate uptakes were carried out in slices of cerebral cortex and hippocampus. [(3)H]GABA uptake was decreased in cerebral cortex (64%) and hippocampus (58%) slices of 21 day-old rats treated with 3-ASP. In contrast, no alteration was observed in [(3)H]glutamate uptake in cerebral cortex and hippocampus slices of 21 day-old rats that received 3-ASP. Considering the drugs that increase synaptic GABA levels, by inhibiting its uptake or catabolism, are effective anticonvulsants, we further investigated the possible interaction between sub-effective doses of 3-ASP and GABA uptake or GABA transaminase (GABA-T) inhibitors in PC-induced seizures in 21 day-old rats. For this end, sub-effective doses of 3-ASP (10 mg/kg, p.o.) and DL-2,4-diamino-n-butyric acid hydrochloride (DABA, an inhibitor of GABA uptake--2 mg/kg, intraperitoneally; i.p.) or aminooxyacetic acid hemihydrochloride (AOAA; a GABA-T inhibitor--10 mg/kg, i.p.) were co-administrated to 21 day-old rats before PC (400 mg/kg; i.p.) treatment, and the appearance of seizures was recorded. Results demonstrated that treatment with AOAA and 3-ASP or DABA and 3-ASP significantly abolished the number of convulsing animals induced by PC. The present study indicates that 3-ASP reduced [(3)H]GABA uptake, suggesting that its anticonvulsant action is related to an increase in inhibitory tonus.

Fronto-limbic dysfunction in mania pre-treatment and persistent amygdala over-activity post-treatment in pediatric bipolar disorder

RATIONALE

Neural deficits at the interface of affect and cognition may improve with pharmacotherapy in pediatric bipolar disorder (PBD).

OBJECTIVES

We examined lamotrigine treatment impact on the neural interface of working memory and affect in PBD.

METHODS

Un-medicated, acutely ill, patients with mania and hypomania (n = 17), and healthy controls (HC; n = 13; mean age = 13.36 ± 2.55) performed an affective two-back functional magnetic resonance imaging task with blocks of angry vs neutral faces (i.e., angry face condition) or happy vs neutral faces (i.e., happy face condition) before treatment and at follow-up, after 8-week treatment with second-generation antipsychotics followed by 6 weeks of lamotrigine monotherapy.

RESULTS

At baseline, for the angry face condition, PBD, relative to HC, showed reduced activation in the left ventrolateral prefrontal cortex (VLPFC) and right caudate; for the happy face condition, PBD showed increased activation in bilateral PFC and right amygdala and middle temporal gyrus. Post-treatment, PBD showed greater activation in right amygdala relative to HC for both conditions. Patients, relative to HC, exhibited greater changes over time in the right VLPFC and amygdala, left subgenual anterior cingulate cortex and left caudate for the angry face condition, and in right middle temporal gyrus for the happy face condition.

CONCLUSIONS

Pharmacotherapy resulted in symptom improvement and normalization of higher cortical emotional and cognitive regions in patients relative to HC, suggesting that the VLPFC dysfunction may be state-specific in PBD. Amygdala was overactive in PBD, relative to HC, regardless of reduction in manic symptoms, and may be a trait marker of PBD.

Pharmacotherapy for children and adolescents with epilepsy

INTRODUCTION

Childhood epilepsies are the most frequent neurological problems that occur in children. Despite the introduction of new antiepileptic drugs (AEDs) 25-30% of children with epilepsy remain refractory to medical therapy.

AREAS COVERED

This review aims to highlight the main published data on the treatment of childhood epilepsy. The electronic database, PubMed, and abstract proceedings were used to identify studies. The aim of antiepileptic therapy should be to provide complete seizure control, if possible without the burden of any side effect. Since 1993, new agents have been approved for use as an antiepileptic. Although there are few published data (especially in pediatric populations) to establish that the second-generation AEDs are more efficacious than the older AEDs, they appear to have better tolerability.

EXPERT OPINION

Old AEDs are efficacious agents that continue to play a major role in the current treatment of epilepsy. These agents actually remain the first-line treatment for many specific seizure types or epileptic syndromes. The new AEDs were initially approved as adjunct agents and--subsequently--as monotherapy for various seizure types in the adult and children. Despite these improvements, few AEDs are now considered to be a first-choice for the treatment of epilepsy in children.