Blood and cerebrospinal fluid pharmacokinetics of the novel anticonvulsant levetiracetam (ucb L059) in the rat

Pharmacokinetic and pharmacodynamic data from the NEOLEV1 and NEOLEV2 studies

OBJECTIVES

To confirm that levetiracetam (LEV) demonstrates predictable pharmacokinetics(PK) at higher doses and to study the pharmacodynamics(PD) of LEV.

DESIGN

Pharmacokinetic data from the NEOLEV1 and NEOLEV2 trials were analysed using a non-linear mixed effects modelling approach. A post hoc analysis of the effect of LEV on seizure burden was conducted.

SETTING

Neonatal intensive care unit.

PATIENTS

Term neonates with electrographically confirmed seizures.

INTERVENTIONS

In NEOLEV1, neonates with seizures persisting following phenobarbital (PHB) received LEV 20 or 40 mg/kg bolus followed by 5 or 10 mg/kg maintenance dose(MD) daily. In NEOLEV2, patients received a 40 mg/kg intravenous LEV load, followed by 10 mg/kg doses 8 hourly. If seizures persisted, a further 20 mg/kg intravenous load was given. If seizures persisted, PHB was given. PK data were collected from 16 NEOLEV1 patients and 33 NEOLEV2 patients. cEEG data from 48 NEOLEV2 patients were analysed to investigate onset of action and seizure burden reduction.

MAIN OUTCOME MEASURES

Clearance (CL) and volume of distribution (Vd) were determined. Covariates that significantly affected LEV disposition were identified.

RESULTS

Primary outcome: The median initial LEV level was 57 µg/mL (range 19-107) after the first loading dose and at least 12 µg/mL at 48 hours in all infants. CL and Vd were estimated to be 0.0538 L/hour and 0.832 L, respectively. A direct relationship between postnatal age and CL was observed. The final population pharmacokinetic(PopPK) model described the observed data well without significant biases. CL and Vd were described as CL (L/hour)=0.0538×(weight in kg/3.34)0.75×(postnatal age in days/5.5) 0.402 and Vd (L)=0.832×(weight in kg/3.34).Seizure burden reduced within 30 min of LEV administration. 28% of patients were completely seizure free after LEV. In an additional 25% of patients, seizure burden reduced by 50%.

CONCLUSIONS

LEV pharmacokinetics remained predictable at higher doses. Very high-dose LEV can now be studied in neonates.

TRIAL REGISTRATION NUMBER

NCT01720667.

Interspecies Brain PBPK Modeling Platform to Predict Passive Transport through the Blood-Brain Barrier and Assess Target Site Disposition

The high failure rate of central nervous system (CNS) drugs is partly associated with an insufficient understanding of target site exposure. Blood-brain barrier (BBB) permeability evaluation tools are needed to explore drugs' ability to access the CNS. An outstanding aspect of physiologically based pharmacokinetic (PBPK) models is the integration of knowledge on drug-specific and system-specific characteristics, allowing the identification of the relevant factors involved in target site distribution. We aimed to qualify a PBPK platform model to be used as a tool to predict CNS concentrations when significant transporter activity is absent and human data are sparse or unavailable. Data from the literature on the plasma and CNS of rats and humans regarding acetaminophen, oxycodone, lacosamide, ibuprofen, and levetiracetam were collected. Human BBB permeability values were extrapolated from rats using inter-species differences in BBB surface area. The percentage of predicted AUC and Cmax within the 1.25-fold criterion was 85% and 100% for rats and humans, respectively, with an overall GMFE of <1.25 in all cases. This work demonstrated the successful application of the PBPK platform for predicting human CNS concentrations of drugs passively crossing the BBB. Future applications include the selection of promising CNS drug candidates and the evaluation of new posologies for existing drugs.

Temporal relationship between levetiracetam nonadherence and breakthrough seizures in a preclinical model of temporal lobe epilepsy

OBJECTIVE

Poor medication adherence remains a concern for individuals managing their epilepsy with antiseizure medicines (ASMs); however, ethical concerns around withholding medication make it impossible to study the causal relationship between missed doses and seizures in patients. Previous preclinical studies from our group suggest that mechanistically distinct ASMs have varying degrees of forgiveness when a dose is missed. However, with only a few ASMs studied in the context of nonadherence, we sought to expand on previous work to understand the relationship between levetiracetam (LEV) nonadherence and breakthrough seizures.

METHODS

Chronic oral dosing was initiated in rats with established epilepsy via our automated medication-in-food delivery system coupled to 24/7 video-electroencephalographic recording. Baseline seizure burden was established for 4 weeks before enrolling subjects into a 4-week treatment period with LEV in a 100% fully adherent (75 mg/kg four times daily) or 50% variably adherent paradigm. The temporal relationship between missed doses and breakthrough seizures was correlated with LEV plasma and brain concentrations in separate cohorts of animals.

RESULTS

Full adherence to LEV significantly improved seizure control by 50% in half of the animals. Poor adherence worsened seizure frequency by 85%, with most rats having more severe seizures that formed in clusters following missed doses. LEV concentrations remained below therapeutic levels (<10 μg/mL) in nonadherent animals, with brain and plasma levels directly correlating with the degree of adherence in a 24-h period. Missed doses of LEV immediately increased the risk of breakthrough seizures; however, this risk was significantly reduced with improved adherence in a 24-h period.

SIGNIFICANCE

These findings enhance our understanding of ASM nonadherence in preclinical models, highlighting that the timing of missed doses and their impact on seizures may vary between different ASMs. Notably, LEV demonstrates a robust pharmacokinetic reliance on missed doses leading to breakthrough seizures.

Treatment of Status Epilepticus after Traumatic Brain Injury Using an Antiseizure Drug Combined with a Tissue Recovery Enhancer Revealed by Systems Biology

We tested a hypothesis that in silico-discovered compounds targeting traumatic brain injury (TBI)-induced transcriptomics dysregulations will mitigate TBI-induced molecular pathology and augment the effect of co-administered antiseizure treatment, thereby alleviating functional impairment. In silico bioinformatic analysis revealed five compounds substantially affecting TBI-induced transcriptomics regulation, including calpain inhibitor, chlorpromazine, geldanamycin, tranylcypromine, and trichostatin A (TSA). In vitro exposure of neuronal-BV2-microglial co-cultures to compounds revealed that TSA had the best overall neuroprotective, antioxidative, and anti-inflammatory effects. In vivo assessment in a rat TBI model revealed that TSA as a monotherapy (1 mg/kg/d) or in combination with the antiseizure drug levetiracetam (LEV 150 mg/kg/d) mildly mitigated the increase in plasma levels of the neurofilament subunit pNF-H and cortical lesion area. The percentage of rats with seizures during 0-72 h post-injury was reduced in the following order: TBI-vehicle 80%, TBI-TSA (1 mg/kg) 86%, TBI-LEV (54 mg/kg) 50%, TBI-LEV (150 mg/kg) 40% (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 30% (p < 0.05). Cumulative seizure duration was reduced in the following order: TBI-vehicle 727 ± 688 s, TBI-TSA 898 ± 937 s, TBI-LEV (54 mg/kg) 358 ± 715 s, TBI-LEV (150 mg/kg) 42 ± 64 (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 109 ± 282 s (p < 0.05). This first preclinical intervention study on post-TBI acute seizures shows that a combination therapy with the tissue recovery enhancer TSA and LEV was safe but exhibited no clear benefit over LEV monotherapy on antiseizure efficacy. A longer follow-up is needed to confirm the possible beneficial effects of LEV monotherapy and combination therapy with TSA on chronic post-TBI structural and functional outcomes, including epileptogenesis.

Discovery of E2730, a novel selective uncompetitive GAT1 inhibitor, as a candidate for anti-seizure medication

OBJECTIVE

As of 2022, 36 anti-seizure medications (ASMs) have been licensed for the treatment of epilepsy, however, adverse effects (AEs) are commonly reported. Therefore, ASMs with a wide margin between therapeutic effects and AEs are preferred over ASMs that are associated with a narrow margin between efficacy and risk of AEs. E2730 was discovered using in vivo phenotypic screening and characterized as an uncompetitive, yet selective, inhibitor of γ-aminobutyric acid (GABA) transporter 1 (GAT1). Here, we describe the preclinical characteristics of E2730.

METHODS

Anti-seizure effects of E2730 were evaluated in several animal models of epilepsy: corneal kindling, 6 Hz-44 mA psychomotor seizure, amygdala kindling, Fragile X syndrome, and Dravet syndrome models. Effects of E2730 on motor coordination were assessed in accelerating rotarod tests. The mechanism of action of E2730 was explored by [3 H]E2730 binding assay. The GAT1-selectivity over other GABA transporters was examined by GABA uptake assay of GAT1, GAT2, GAT3, or betaine/GABA transporter 1 (BGT-1) stably expressing HEK293 cells. To further investigate the mechanism for E2730-mediated inhibition of GAT1, in vivo microdialysis and in vitro GABA uptake assays were conducted under conditions of different GABA concentrations.

RESULTS

E2730 showed anti-seizure effects in the assessed animal models with an approximately >20-‍fold margin between efficacy and motor incoordination. [3 H]E2730 binding on brain synaptosomal membrane was abolished in GAT1-deficient mice, and E2730 selectively inhibited GAT1-mediated GABA uptake over other GABA transporters. In addition, results of GABA uptake assays showed that E2730-mediated inhibition of GAT1 positively correlated to the level of ambient GABA in vitro. E2730 also increased extracellular GABA concentration in hyperactivated conditions but not under basal levels in vivo.

SIGNIFICANCE

E2730 is a novel, selective, uncompetitive GAT1 inhibitor, which acts selectively under the condition of increasing synaptic activity, contributing to a wide margin between therapeutic effect and motor incoordination.

Levetiracetam Mechanisms of Action: From Molecules to Systems

Epilepsy is a chronic disease that affects millions of people worldwide. Antiepileptic drugs (AEDs) are used to control seizures. Even though parts of their mechanisms of action are known, there are still components that need to be studied. Therefore, the search for novel drugs, new molecular targets, and a better understanding of the mechanisms of action of existing drugs is still crucial. Levetiracetam (LEV) is an AED that has been shown to be effective in seizure control and is well-tolerable, with a novel mechanism of action through an interaction with the synaptic vesicle protein 2A (SV2A). Moreover, LEV has other molecular targets that involve calcium homeostasis, the GABAergic system, and AMPA receptors among others, that might be integrated into a single mechanism of action that could explain the antiepileptogenic, anti-inflammatory, neuroprotective, and antioxidant properties of LEV. This puts it as a possible multitarget drug with clinical applications other than for epilepsy. According to the above, the objective of this work was to carry out a comprehensive and integrative review of LEV in relation to its clinical uses, structural properties, therapeutical targets, and different molecular, genetic, and systemic action mechanisms in order to consider LEV as a candidate for drug repurposing.

Levetiracetam promoted rat embryonic neurogenesis via NMDA receptor-mediated mechanism in vitro

AIMS

Levetiracetam (LEV) is a broad-spectrum antiepileptic drug with neuroprotective properties and novel mechanisms of action. Some evidence suggests that LEV may impact adult neurogenesis, but the results are controversial. The present study was aimed to evaluate the effects of LEV on the proliferation and differentiation of rat embryonic neural stem cells (NSCs) and to explore the role of GABAB or NMDA receptors.

MAIN METHODS

NSCs were isolated from rat fetal ganglionic eminence at embryonic day 14.5. The effects of LEV on viability, proliferation, neurosphere formation, and neuronal or astroglial differentiation of NSCs were assessed using resazurin, BrdU incorporation, immunocytochemistry, quantitative real-time PCR, and western blotting. Additionally, we addressed the relationship between treatment with NMDA and GABAB receptor antagonists (MK801 and saclofen, respectively) in combination with LEV on these parameters.

KEY FINDINGS

The data showed that LEV (50 μM) significantly increased the number (p < 0.01) and diameter of neurospheres (p < 0.05), enhanced proliferation (p < 0.01), and promoted neuronal differentiation, as revealed by significantly increased expressions of DCX and NeuN. The expressions of astroglial markers, GFAP and Olig2, were markedly reduced. The addition of MK801 (10 μM) significantly diminished neurospheres growth (p < 0.001), decreased the number of proliferating cells (p < 0.01), and reduced the number of new neurons (p < 0.001) but increased the astroglial cells (p < 0.001) induced by LEV. Co-treatment with saclofen (25 μM) did not significantly affect LEV-induced NSCs proliferation and differentiation.

SIGNIFICANCE

Our findings suggest that LEV may enhance rat embryonic neurogenesis mainly through an NMDA receptor-mediated mechanism.

Pharmacokinetics of levetiracetam in neurosurgical ICU patients

BACKGROUND/OBJECTIVES

The pharmacokinetics (PK) of drugs is dramatically altered in critical illness. Augmented renal clearance (ARC), a phenomenon characterized by creatinine clearance (CrCl) greater than 130 ml/min/1.73m², is commonly described in critically ill patients. Levetiracetam, an antiepileptic drug commonly prescribed for seizure prophylaxis in the neurosurgical ICU, undergoes predominant elimination via the kidneys. Hence, we hypothesize that current dosing practice of intravenous (IV) levetiracetam 500 mg twice daily is inadequate for critically ill patients due to enhanced drug elimination. The objectives of our study were to describe the population PK of levetiractam using a nonparametric approach to design an optimal dosing regimen for critically ill neurosurgical patients.

METHODS

This was a prospective, observational, population PK study. Serial blood samples were obtained from neurosurgical ICU patients who received at least one dose of IV levetiracetam. We used uHPLC to analyze these samples and Pmetrics™ software to perform PK analysis.

RESULTS

Twenty subjects were included, with a median age of 54 years and CrCl of 104 ml/min. A two-compartmental model with linear elimination adequately described the profile of levetiracetam. Mean clearance (CL) was 3.55 L/h and volume of distribution (V) was 18.8 L. No covariates were included in the final model. Monte Carlo simulations showed a low probability of target attainment (PTA, trough at steady state of ≥6 mg/L) with a standard dose of 500 mg twice daily. A dose of at least 1000 mg twice daily was required to achieve 80% PTA. Two subjects, both with subtherapeutic trough levels, developed early onset seizures.

CONCLUSION

Our study examined the population PK of levetiracetam in a critically ill neurosurgical population. We found that this population displayed higher clearance and required higher doses to achieve target levels.

Early intervention with levetiracetam prevents the development of cortical hyperexcitability and spontaneous epileptiform activity in two models of neurotrauma in rats

This study examined the antiepileptogenic potential of the antiseizure drug (ASD) levetiracetam (LEV) using the in vitro traumatized-slice and in vivo controlled cortical impact (CCI) models of traumatic brain injury (TBI) in rats when administered early after the injury. For the in vitro model, acute coronal slices (400-450 μm) of rat neocortex (P21-32) were injured via a surgical cut that separated the superficial layers from the deeper regions. Persistent stimulus-evoked epileptiform activity developed within 1-2 h after trauma. In randomly selected slices, LEV (500 μM) was bath-applied for 1 h starting immediately or delayed by 30-80 min after injury. Treated and untreated slices were examined for epileptiform activity via intracellular and extracellular recordings. For the in vivo model, rats (P24-32) were subjected to a non-penetrating, focal, CCI injury targeting the neocortex (5.0 mm diameter; 2.0 mm depth). Immediately after injury, rats were given either a single dose of LEV (60-150 mg/kg, i.p.) or the saline vehicle. At 2-3 weeks after the injury, ex vivo cortical slices were examined for epileptiform activity. The results from the traumatized-slice experiments showed that in vitro treatment with LEV within 60 min of injury significantly reduced (> 50%) the proportion of slices that exhibited stimulus-evoked epileptiform activity. LEV treatment also increased the stimulus intensity required to trigger epileptiform bursts in injured slices by 2-4 fold. Consistent with these findings, LEV treatment of CCI-injured rats (n = 15) significantly reduced the proportion of animals that exhibited spontaneous and stimulus-evoked epileptiform bursts in ex vivo cortical slices compared to saline-treated controls (n = 15 rats), and also significantly increased the stimulus intensity required to evoke epileptiform bursts. These results suggest that early administration of LEV has the potential to prevent or reduce posttraumatic epileptogenesis and that there may be a narrow therapeutic window for successful prophylactic intervention.

Pharmacokinetics of a commercially available product and a compounded formulation of extended-release levetiracetam after oral administration of a single dose in cats

OBJECTIVE

To compare pharmacokinetics of levetiracetam in serum and CSF of cats after oral administration of extended-release (ER) levetiracetam.

ANIMALS

9 healthy cats.

PROCEDURES

Cats received 1 dose of a commercially available ER levetiracetam product (500 mg, PO). Thirteen blood and 10 CSF samples were collected over a 24-hour period for pharmacokinetic analysis. After 1 week, cats received 1 dose of a compounded ER levetiracetam formulation (500 mg, PO), and samples were obtained at the same times for analysis.

RESULTS

CSF concentrations of levetiracetam closely paralleled serum concentrations. There were significant differences between the commercially available product and the compounded formulation for mean ± SD serum maximum concentration (C_max; 126 ± 33 μg/mL and 169 ± 51 μg/mL, respectively), C_max corrected for dose (0.83 ± 0.10 μg/mL/mg and 1.10 ± 0.28 μg/mL/mg, respectively), and time to C_max (5.1 ± 1.6 hours and 3.1 ± 1.5 hours, respectively). Half-life for the commercially available product and compounded formulation of ER levetiracetam was 4.3 ± 2.0 hours and 5.0 ± 1.6 hours, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The commercially available product and compounded formulation of ER levetiracetam both maintained concentrations in healthy cats 12 hours after oral administration that have been found to be therapeutic in humans (ie, 5 μg/mL). Results of this study supported dosing intervals of 12 hours, and potentially 24 hours, for oral administration of ER levetiracetam to cats. Monitoring of serum concentrations of levetiracetam can be used as an accurate representation of levetiracetam concentrations in CSF of cats.

Mode of seizure inhibition by sodium channel blockers, an SV2A ligand, and an AMPA receptor antagonist in a rat amygdala kindling model

PURPOSE

A number of antiepileptic drugs (AEDs) with a variety of modes of action, are effective in treating focal seizures. Several AEDs, such as perampanel (PER), levetiracetam (LEV), lacosamide (LCM), lamotrigine (LTG), and carbamazepine (CBZ), have been shown to elevate the seizure threshold in kindling models. These AEDs are clinically effective, but differences exist in the anti-seizure profiles of drugs with similar modes of action. Therefore, we hypothesized that there are differences in how these AEDs affect seizures. Here, we evaluated the effects of AEDs on various seizure parameters in a rat amygdala kindling model upon stimulation at the after-discharge threshold (ADT) and at three-times the ADT (3xADT) to characterize the differences in the effects of these AEDs.

METHODS

PER, LEV, LCM, LTG, CBZ, or vehicle was administered intraperitoneally to fully kindled rats. Changes in Racine seizure score, after-discharge duration (ADD), and latency to Racine score 4 generalized seizure (S₄L) were measured to assess differences in the modes of seizure inhibition among the AEDs. Stimulation at 3xADT was used to eliminate the influence of any AED-induced elevation of the seizure threshold on these parameters.

RESULTS

PER, LEV, LCM, LTG, and CBZ significantly reduced the seizure score from Racine score 5 after stimulation at the ADT; this effect was lost with LEV and LTG after stimulation at 3xADT. PER and LEV significantly shortened the ADD when the seizure focus was stimulated at the ADT, whereas LCM, LTG, and CBZ did not. LEV, LCM, LTG, and CBZ failed to shorten the ADD upon stimulation at 3xADT. PER dose-dependently and significantly increased S₄L, even at doses that were ineffective for seizure score reduction, after stimulation at both the ADT and 3xADT. LEV and LTG significantly increased S₄L after stimulation at the ADT, whereas LCM and CBZ did not significantly increase S₄L at any of the doses tested.

CONCLUSIONS

The sodium channel blockers (LCM, LTG, and CBZ) appeared to act by elevation of the seizure threshold via reduction of neuronal excitability, whereas the AMPA receptor antagonist (PER) and the SV2A ligand (LEV), as well as LTG, exerted their effects through the weakening of synaptic transmission in neuronal networks at the seizure focus. Maintenance of the effect of PER even at 3xADT suggests direct and strong modulation of excitatory synaptic transmission by PER, both at the focus and along the seizure propagation route. These findings may provide further rationale for usage of AEDs beyond their respective modes of action.

Levetiracetam circulating concentrations and response in status epilepticus

INTRODUCTION

Intravenous levetiracetam (LEV) is broadly used in the treatment of status epilepticus (SE). A loading dose is usually infused, aiming to reach quickly the range of plasma concentrations considered as therapeutic (12-46 mg/l). The aim of the study was to evaluate the response to LEV in SE, correlated exposure assessed by plasma concentration monitoring, as well as calculated exposure parameters.

MATERIALS & METHODS

We retrospectively analyzed a SE registry, including patients since 2015 with at least one available LEV plasma level measured less than 36 h after loading. A Bayesian maximum likelihood approach based on a population pharmacokinetic model was used to estimate LEV exposure parameters. We compared plasma levels and pharmacokinetics parameter estimates between responders and nonresponders. Therapeutic response was defined as SE cessation within 24 h following LEV introduction without a need for additional antiepileptic drug (AED).

RESULTS

We included 29 patients (45 plasma levels). Variability was salient in LEV loading doses (ranging between 17 and 38 mg/kg) and monitoring practice. There was no difference in median plasma concentrations (19.5 versus 21.5 mg/l; p = 0.71), median estimated LEV exposure (25.8 versus 37.0 mg/l; p = 0.61), peak (30.4 versus 41.5 mg/l; p = 0.36), or residual levels after loading dose (14.4 versus 20.5 mg/l; p = 0.07) between responders and nonresponders.

CONCLUSIONS

Levetiracetam exposure does not seem to differ significantly between responders and nonresponders; greater exposure was not associated with better outcome. Loading doses of 30 mg/kg seem, however, appropriate to quickly reach the target exposure level. The short LEV half-life makes standardized sampling measurement necessary to obtain directly interpretable LEV levels.

Pyridoxine Add-On Treatment for the Control of Behavioral Adverse Effects Induced by Levetiracetam in Children: A Case-Control Prospective Study

BACKGROUND

Few studies on adult and pediatric patients have shown pyridoxine efficacy as additional therapy for those receiving levetiracetam (LEV) to prevent and mitigate behavioral adverse effects (BAEs).

OBJECTIVE

The aim of our study was to analyze the safety and efficacy of pyridoxine supplementation in the prevention of LEV adverse effects, including suicidal ideation.

METHODS

This randomized, case-control trial included patients receiving LEV as monotherapy treatment. Patients were subdivided into 2 groups, according to whether they were treated with LEV only (group 1) or LEV with supplemental pyridoxine (group 2).

RESULTS

In both cohorts, the most frequent BAEs were irritability/aggression followed by depression and confusion. Those patients (92%) who initiated pyridoxine after 1 month of LEV treatment did not need to change or suspend LEV ( P < 0.001), and BAE improved after 9.06 ± 3.05 days of pyridoxine supplementation. None of the patients complained of symptoms of pyridoxine toxicity, and no new adverse effects of LEV off-label were reported.

CONCLUSIONS

In our study, we found pyridoxine to be safe and effective in controlling LEV-induced BAEs in children.

Protein instability, haploinsufficiency, and cortical hyper-excitability underlie STXBP1 encephalopathy

De novo heterozygous mutations in STXBP1/Munc18-1 cause early infantile epileptic encephalopathies (EIEE4, OMIM #612164) characterized by infantile epilepsy, developmental delay, intellectual disability, and can include autistic features. We characterized the cellular deficits for an allelic series of seven STXBP1 mutations and developed four mouse models that recapitulate the abnormal EEG activity and cognitive aspects of human STXBP1-encephalopathy. Disease-causing STXBP1 variants supported synaptic transmission to a variable extent on a null background, but had no effect when overexpressed on a heterozygous background. All disease variants had severely decreased protein levels. Together, these cellular studies suggest that impaired protein stability and STXBP1 haploinsufficiency explain STXBP1-encephalopathy and that, therefore, Stxbp1+/- mice provide a valid mouse model. Simultaneous video and EEG recordings revealed that Stxbp1+/- mice with different genomic backgrounds recapitulate the seizure/spasm phenotype observed in humans, characterized by myoclonic jerks and spike-wave discharges that were suppressed by the antiepileptic drug levetiracetam. Mice heterozygous for Stxbp1 in GABAergic neurons only, showed impaired viability, 50% died within 2-3 weeks, and the rest showed stronger epileptic activity. c-Fos staining implicated neocortical areas, but not other brain regions, as the seizure foci. Stxbp1+/- mice showed impaired cognitive performance, hyperactivity and anxiety-like behaviour, without altered social behaviour. Taken together, these data demonstrate the construct, face and predictive validity of Stxbp1+/- mice and point to protein instability, haploinsufficiency and imbalanced excitation in neocortex, as the underlying mechanism of STXBP1-encephalopathy. The mouse models reported here are valid models for development of therapeutic interventions targeting STXBP1-encephalopathy.

What goes up must come down: homeostatic synaptic plasticity strategies in neurological disease

Brain activity levels are tightly regulated to minimize imbalances in activity state. Deviations from the normal range of activity are deleterious and often associated with neurological disorders. To maintain optimal levels of activity, regulatory mechanisms termed homeostatic synaptic plasticity establish desired 'set points' for neural activity, monitor the network for deviations from the set point and initiate compensatory responses to return activity to the appropriate level that permits physiological function [1,2]. We speculate that impaired homeostatic control may contribute to the etiology of various neurological disorders including epilepsy and Alzheimer's disease, two disorders that exhibit hyperexcitability as a key feature during pathogenesis. Here, we will focus on recent progress in developing homeostatic regulation of neural activity as a therapeutic tool.

Disposition of levetiracetam in healthy adult horses

Nine horses received 20 mg/kg of intravenous (LEV_IV ); 30 mg/kg of intragastric, crushed immediate release (LEV_CIR ); and 30 mg/kg of intragastric, crushed extended release (LEV_CER ) levetiracetam, in a three-way randomized crossover design. Crushed tablets were dissolved in water and administered by nasogastric tube. Serum samples were collected over 48 hr, and levetiracetam concentrations were determined by immunoassay. Mean ± SD peak concentrations for LEV_CIR and LEV_CER were 50.72 ± 10.60 and 53.58 ± 15.94 μg/ml, respectively. The y-intercept for IV administration was 64.54 ± 24.99 μg/ml. The terminal half-life was 6.38 ± 1.97, 7.07 ± 1.93 and 6.22 ± 1.35 hr for LEV_CIR , LEV_CER, and LEV_IV , respectively. Volume of distribution at steady-state was 630 ± 73.4 ml/kg. Total body clearance after IV administration was 74.40 ± 19.20 ml kg^-1  hr^-1 . Bioavailability was 96 ± 10, and 98 ± 13% for LEV_CIR and LEV_CER , respectively. A single dose of Levetiracetam (LEV) was well tolerated. Based on this study, a recommended dosing regimen of intravenous or oral LEV of 32 mg/kg every 12 hr is likely to achieve and maintain plasma concentrations within the therapeutic range suggested for humans, with optimal kinetics throughout the dosing interval in healthy adult horses. Repeated dosing and pharmacodynamic studies are warranted.

Newer Antiepileptic Drugs in Status Epilepticus: Prescription Trends and Outcomes in Comparison with Traditional Agents

INTRODUCTION

Newer antiepileptic drugs (AEDs) are increasingly prescribed; however, relatively limited data are available regarding their use in status epilepticus (SE) and the impact on outcome.

OBJECTIVES

The aim of this study was to explore the evolution in prescription patterns of newer and traditional AEDs in this clinical setting, and their association with prognosis.

METHODS

We analyzed our prospective adult SE registry over a 10-year period (2007-2016) and assessed the yearly use of newer and traditional AEDs and their association with mortality, return to baseline conditions at discharge, and SE refractoriness, defined as treatment resistance to two AEDs, including benzodiazepines.

RESULTS

In 884 SE episodes, corresponding to 719 patients, the prescription of at least one newer AED increased from 0.38 per SE episode in 2007 to 1.24 per SE episode in 2016 (mostly due to the introduction of levetiracetam and lacosamide). Traditional AEDs (excluding benzodiazepines) decreased over time from 0.74 in 2007 to 0.41 in 2016, correlating with the decreasing use of phenytoin. The prescription of newer AEDs was independently associated with a lower chance of return to baseline conditions at discharge (odds ratio [OR] 0.58, 95% confidence interval [CI] 0.40-0.84) and a higher rate of SE refractoriness (OR 19.84, 95% CI 12.76-30.84), but not with changes in mortality (OR 1.08, 95% CI 0.58-2.00).

CONCLUSION

We observed a growing trend in the prescription of newer AEDs in SE over the last decade; however, our findings might suggest an associated increased risk of SE refractoriness and new disability at hospital discharge. Pending prospective, comparative studies, this may justify some caution in the routine use of newer AEDs in SE.

Dose-dependent effects of levetiracetam after hypoxia and hypothermia in the neonatal mouse brain

Perinatal asphyxia to the developing brain remains a major cause of morbidity. Hypothermia is currently the only established neuroprotective treatment available for term born infants with hypoxic-ischemic encephalopathy, saving one in seven to eight infants from developing severe neurological deficits. Therefore, additional treatments with clinically applicable drugs are indispensable. This study investigates a potential additive neuroprotective effect of levetiracetam combined with hypothermia after hypoxia-induced brain injury in neonatal mice. 9-day-old C57BL/6-mice (P9) were subjected either to acute hypoxia or room-air. After 90min of systemic hypoxia (6% O2), pups were randomized into six groups: 1) vehicle, 2) low-dose levetiracetam (LEV), 3) high-dose LEV, 4) hypothermia (HT), 5) HT combined with low-dose LEV and 6) HT combined with high-dose LEV. Pro-apoptotic factors, neuronal structures, and myelination were analysed by histology and on protein level at appropriate time points. On P28 to P37 long-term outcome was assessed by neurobehavioral testing. Hypothermia confers acute and long-term neuroprotection by reducing apoptosis and preservation of myelinating oligodendrocytes and neurons in a model of acute hypoxia in the neonatal mouse brain. Low-dose LEV caused no adverse effects after neonatal hypoxic brain damage treated with hypothermia whereas administration of high-dose LEV alone or in combination with hypothermia increased neuronal apoptosis after hypoxic brain injury. LEV in low- dosage had no additive neuroprotective effect following acute hypoxic brain injury.

Brivaracetam, a selective high-affinity synaptic vesicle protein 2A (SV2A) ligand with preclinical evidence of high brain permeability and fast onset of action

OBJECTIVE

Rapid distribution to the brain is a prerequisite for antiepileptic drugs used for treatment of acute seizures. The preclinical studies described here investigated the high-affinity synaptic vesicle glycoprotein 2A (SV2A) antiepileptic drug brivara-cetam (BRV) for its rate of brain penetration and its onset of action. BRV was compared with levetiracetam (LEV).

METHODS

In vitro permeation studies were performed using Caco-2 cells. Plasma and brain levels were measured over time after single oral dosing to audiogenic mice and were correlated with anticonvulsant activity. Tissue distribution was investigated after single dosing to rat (BRV and LEV) and dog (LEV only). Positron emission tomography (PET) displacement studies were performed in rhesus monkeys using the SV2A PET tracer [11C]UCB-J. The time course of PET tracer displacement was measured following single intravenous (IV) dosing with LEV or BRV. Rodent distribution data and physiologically based pharmacokinetic (PBPK) modeling were used to compute blood-brain barrier permeability (permeability surface area product, PS) values and then predict brain kinetics in man.

RESULTS

In rodents, BRV consistently showed a faster entry into the brain than LEV; this correlated with a faster onset of action against seizures in audiogenic susceptible mice. The higher permeability of BRV was also demonstrated in human cells in vitro. PBPK modeling predicted that, following IV dosing to human subjects, BRV might distribute to the brain within a few minutes compared with approximately 1 h for LEV (PS of 0.315 and 0.015 ml/min/g for BRV and LEV, respectively). These data were supported by a nonhuman primate PET study showing faster SV2A occupancy by BRV compared with LEV.

SIGNIFICANCE

These preclinical data demonstrate that BRV has rapid brain entry and fast brain SV2A occupancy, consistent with the fast onset of action in the audiogenic seizure mice assay. The potential benefit of BRV for treatment of acute seizures remains to be confirmed in clinical studies.

Intravenous and Intramuscular Formulations of Antiseizure Drugs in the Treatment of Epilepsy

Intravenous and intramuscular antiseizure drugs (ASDs) are essential in the treatment of clinical seizure emergencies as well as in replacement therapy when oral administration is not possible. The parenteral formulations provide rapid delivery and complete (intravenous) or nearly complete (intramuscular) bioavailability. Controlled administration of the ASD is feasible with intravenous but not intramuscular formulations. This article reviews the literature and discusses the chemistry, pharmacology, pharmacokinetics, and clinical use of currently available intravenous and intramuscular ASD formulations as well as the development of new formulations and agents. Intravenous or intramuscular formulations of lorazepam, diazepam, midazolam, and clonazepam are typically used as the initial treatment agents in seizure emergencies. Recent studies also support the use of intramuscular midazolam as easier than the intravenous delivery of lorazepam in the pre-hospital setting. However, benzodiazepines may be associated with hypotension and respiratory depression. Although loading with intravenous phenytoin was an early approach to treatment, it is associated with cardiac arrhythmias, hypotension, and tissue injury at the injection site. This has made it less favored than fosphenytoin, a water-soluble, phosphorylated phenytoin molecule. Other drugs being used for acute seizure emergencies are intravenous formulations of valproic acid, levetiracetam, and lacosamide. However, the comparative effectiveness of these for status epilepticus (SE) has not been evaluated adequately. Consequently, guidelines for the medical management of SE continue to recommend lorazepam followed by fosphenytoin, or phenytoin if fosphenytoin is not available. Intravenous solutions for carbamazepine, lamotrigine, and topiramate have been developed but remain investigational. The current ASDs were not developed for use in emergency situations, but were adapted from ASDs approved for chronic oral use. New approaches for bringing drugs from experimental models to treatment of human SE are needed.

Prehospital treatment with levetiracetam plus clonazepam or placebo plus clonazepam in status epilepticus (SAMUKeppra): a randomised, double-blind, phase 3 trial

BACKGROUND

Generalised convulsive status epilepticus (GCSE) should be treated quickly. Benzodiazepines are the only drug treatment available so far that is effective before admission to hospital. We assessed whether addition of the antiepileptic drug levetiracetam to the benzodiazepine clonazepam would improve prehospital treatment of GCSE.

METHODS

We did a prehospital, randomised, double-blind, phase 3, placebo-controlled, superiority trial to determine the efficacy of adding intravenous levetiracetam (2.5 g) to clonazepam (1 mg) in treatment of GCSE in 13 emergency medical service centres and 26 hospital departments in France. Randomisation was done at the Paris Descartes Clinical Research Unit with a list of random numbers generated by computer. Adults with convulsions lasting longer than 5 min were randomly assigned (1:1) by prehospital physicians to receive levetiracetam or placebo in combination with clonazepam. All physicians and paramedics were masked to group assignments. If the status epilepticus lasted beyond 5 min after drug injection, a second dose of 1 mg clonazepam was given. The primary outcome was cessation of convulsions within 15 min of drug injection. We analysed the modified intention-to-treat population that had received at least one injection of clonazepam and levetiracetam or placebo, excluding patients without valid consent and those randomised more than once. The trial is registered at EudraCT, number 2007-005782-35.

FINDINGS

Between July 20, 2009, and Dec 15, 2012, 107 patients were randomly assigned to receive placebo and 96 were assigned to receive levetiracetam. The trial was discontinued on Dec 15, 2012 when interim analysis showed no evidence of a treatment difference, and 68 patients in each group were included in the modified intention-to-treat analysis. Convulsions stopped at 15 min of drug injection in 57 of 68 patients (84%) receiving clonazepam and placebo and in 50 of 68 patients (74%) receiving clonazepam and levetiracetam (percentage difference -10.3%, 95% CI -24.0 to 3.4). Three deaths, 19 of 47 (40 %) serious adverse events, and 90 of 197 (46%) non-serious events were reported in the levetiracetam group, and four deaths, 28 of 47 (60%) serious events, and 107 of 197 (54%) non-serious events were reported in the placebo group.

INTERPRETATION

The addition of levetiracetam to clonazepam treatment presented no advantage over clonazepam treatment alone in the control of GCSE before admission to hospital. Future prehospital trials could assess the efficacy of clonazepam alone as a first-line treatment in status epilepticus and the efficacy of a second injection of clonazepam with another antiepileptic drug as second-line treatment.

FUNDING

UCB Pharma.

Intramuscular and rectal therapies of acute seizures

The intramuscular (IM) and rectal routes are alternative routes of delivery for antiepileptic drugs (AEDs) when the intravenous route is not practical or possible. For treatment of acute seizures, the AED used should have a short time to maximum concentration (Tmax). Some AEDs have preparations that may be given intramuscularly. These include the benzodiazepines (diazepam, lorazepam, and midazolam) and others (fosphenytoin, levetiracetam). Although phenytoin and valproate have parenteral preparations, these should not be given intramuscularly. A recent study of prehospital treatment of status epilepticus evaluated a midazolam (MDZ) autoinjector delivering IM drug compared to IV lorazepam (LZP). Seizures were absent on arrival to the emergency department in 73.4% of the IM MDZ compared to a 63.4% response in LZP-treated subjects (p < 0.001 for superiority). Almost all AEDs have been evaluated for rectal administration as solutions, gels, and suppositories. In a placebo-controlled study, diazepam (DZP) was administered at home by caregivers in doses that ranged from 0.2 to 0.5 mg/kg. Diazepam was superior to placebo in reduced seizure frequency in children (p < 0.001) and in adults (p = 0.02) and time to recurrent seizures after an initial treatment (p < 0.001). Thus, at this time, only MZD given intramuscularly and DZP given rectally appear to have the properties required for rapid enough absorption to be useful when intravenous routes are not possible. Some drugs cannot be administered rectally owing to factors such as poor absorption or poor solubility in aqueous solutions. The relative rectal bioavailability of gabapentin, oxcarbazepine, and phenytoin is so low that the current formulations are not considered to be suitable for administration by this route. When administered as a solution, diazepam is rapidly absorbed rectally, reaching the Tmax within 5-20 min in children. By contrast, rectal administration of lorazepam is relatively slow, with a Tmax of 1-2h. The dependence of gabapentin on an active transport system, and the much-reduced surface area of the rectum compared with the small intestine, may be responsible for its lack of absorption from the rectum. This article is part of a Special Issue entitled "Status Epilepticus".

Levetiracetam Monotherapy in Children with Epilepsy: A Systematic Review

BACKGROUND

Levetiracetam, a second-generation anti-epileptic drug (AED) with a good efficacy and safety profile, is licensed as monotherapy for adults and children older than 16 years with focal seizures with or without secondary generalization. However, it is increasingly being used off-label in younger children.

OBJECTIVES

We critically reviewed the available evidence and discuss the present status of levetiracetam monotherapy in children 0-16 years old.

DATA SOURCES

We systematically searched the literature using PubMed, Web of Science and Embase up to August 2014 for articles on levetiracetam monotherapy in children. Keywords were levetiracetam, monotherapy and child*. The titles and abstracts of 532 articles were evaluated by AW, of which 480 were excluded. The full texts of the other 52 articles were assessed for relevance.

RESULTS

We covered one review, one opinion statement and 32 studies in this review, including four randomized controlled trials, ten open-label prospective studies, eight retrospective studies, and ten case reports. The formal evidence for levetiracetam monotherapy in children is minimal: it is potentially efficacious or effective as initial monotherapy in children with benign epilepsy with centrotemporal spikes. In all of the published studies, however, efficacy and tolerability of levetiracetam seemed to be good and comparable to other AEDs.

CONCLUSION

The data of 32 studies on levetiracetam monotherapy in children were insufficient to confirm that levetiracetam is effective as initial monotherapy for different types of seizures and/or epilepsy syndromes. There is still an urgent need for well designed trials to justify the widespread use of levetiracetam monotherapy in children of all ages.

Levetiracetam results in increased and decreased alcohol drinking with different access procedures in C57BL/6J mice

The antiepileptic levetiracetam (LEV) has been investigated for the treatment of alcohol abuse. However, little is known about how LEV alters the behavioral effects of alcohol in laboratory animals. The acute effects of LEV on alcohol drinking by male C57BL/6J mice were investigated using two different drinking procedures, limited access [drinking-in-the-dark (DID)] and intermittent access (IA) drinking. In the first experiment (DID), mice had access to a single bottle containing alcohol or sucrose for 4 h every other day. In the second experiment (IA), mice had IA to two bottles, one containing alcohol or sucrose and one containing water, for 24 h on Monday, Wednesday, and Friday. In both experiments, mice were administered LEV (0.3-100 mg/kg intraperitoneally) or vehicle 30 min before access to the drinking solutions. In the DID mice, LEV increased alcohol intake from 4.3 to 5.4 g/kg, whereas in the IA mice LEV decreased alcohol intake from 4.8 to 3.0 g/kg in the first 4 h of access and decreased 24 h alcohol intake from 20 to ∼15 g/kg. These effects appear specific to alcohol, as LEV did not affect sucrose intake in either experiment. LEV appears to differentially affect drinking in animal models of moderate and heavier alcohol consumption.

The antiepileptic drug levetiracetam suppresses non-convulsive seizure activity and reduces ischemic brain damage in rats subjected to permanent middle cerebral artery occlusion

The antiepileptic drug Levetiracetam (Lev) has neuroprotective properties in experimental stroke, cerebral hemorrhage and neurotrauma. In these conditions, non-convulsive seizures (NCSs) propagate from the core of the focal lesion into perilesional tissue, enlarging the damaged area and promoting epileptogenesis. Here, we explore whether Lev neuroprotective effect is accompanied by changes in NCS generation or propagation. In particular, we performed continuous EEG recordings before and after the permanent occlusion of the middle cerebral artery (pMCAO) in rats that received Lev (100 mg/kg) or its vehicle immediately before surgery. Both in Lev-treated and in control rats, EEG activity was suppressed after pMCAO. In control but not in Lev-treated rats, EEG activity reappeared approximately 30-45 min after pMCAO. It initially consisted in single spikes and, then, evolved into spike-and-wave and polyspike-and-wave discharges. In Lev-treated rats, only rare spike events were observed and the EEG power was significantly smaller than in controls. Approximately 24 hours after pMCAO, EEG activity increased in Lev-treated rats because of the appearance of polyspike events whose power was, however, significantly smaller than in controls. In rats sacrificed 24 hours after pMCAO, the ischemic lesion was approximately 50% smaller in Lev-treated than in control rats. A similar neuroprotection was observed in rats sacrificed 72 hours after pMCAO. In conclusion, in rats subjected to pMCAO, a single Lev injection suppresses NCS occurrence for at least 24 hours. This electrophysiological effect could explain the long lasting reduction of ischemic brain damage caused by this drug.

Pharmacological and neuroethological studies of three antiepileptic drugs in the Genetic Audiogenic Seizure Hamster (GASH:Sal)

Epilepsy modeling is essential for understanding the basic mechanisms of the epileptic process. The Genetic Audiogenic Seizure Hamster (GASH:Sal) exhibits generalized tonic-clonic seizures of genetic origin in response to sound stimulation and is currently being validated as a reliable model of epilepsy. Here, we performed a pharmacological and neuroethological study using well-known and widely used antiepileptic drugs (AEDs), including phenobarbital (PB), valproic acid (VPA), and levetiracetam (LEV). The intraperitoneal administration of PB (5-20mg/kg) and VPA (100-300mg/kg) produced a dose-dependent decrease in GASH:Sal audiogenic seizure severity scores. The administration of LEV (30-100mg/kg) did not produce a clear effect. Phenobarbital showed a short plasmatic life and had a high antiepileptic effect starting at 10mg/kg that was accompanied by ataxia. Valproic acid acted only at high concentrations and was the AED with the most ataxic effects. Levetiracetam at all doses also produced sedation and ataxia side effects. We conclude that the GASH:Sal is a reliable genetic model of epilepsy suitable to evaluate AEDs.

A simple assay for determination of levetiracetam in rat dried blood spots by LC-MS/MS

BACKGROUND

A simple LC-MS/MS method was developed and validated for the quantification of levetiracetam (LEV, Keppra®), a broad-spectrum antiepileptic drug (AED) in rat dried blood spots (DBS). LEV was simply extracted with methanol spiked with adenosine (ADE) as IS before LC-MS/MS analysis. The correlation between the DBS and plasma concentrations of LEV was also determined.

RESULTS

Linearity was from 0.067-60 µg/ml for LEV in DBS samples. The intra- and inter-day accuracy and precision of the assay met validation acceptance criteria. The developed assay was applied to monitor levetiracetam DBS levels in Sprague-Dawley rats after intravenous administration. DBS concentrations were well correlated to the plasma concentrations (R² = 0.9399), as fraction of LEV bound to blood cells remains very constant (0.466 ± 0.041) over a wide concentration range.

CONCLUSION

The study illustrated that DBS could be used as alternative matrix for monitoring LEV in preclinical studies.

Levetiracetam has opposite effects on alcohol- and cocaine-related behaviors in C57BL/6J mice

The antiepileptic drug levetiracetam (LEV) is a potential treatment for alcohol use disorders, yet few preclinical studies exist on its effects in animal models relevant to drug or alcohol abuse. We investigated the effects of LEV on locomotor stimulation following acute and repeated administration of alcohol or cocaine and on alcohol- and cocaine-mediated changes in responding for brain stimulation reward (BSR) in C57BL/6J mice. LEV alone (10.0-100.0 mg/kg intraperitoneally) had no significant effect on locomotor activity or intracranial self-stimulation. Pretreatment with LEV reduced acute locomotor stimulation by 2.0 g/kg alcohol, attenuated the development of locomotor sensitization to alcohol with repeated exposure, and produced a shift in the dose-response curve for alcohol on BSR threshold without affecting maximum operant response rate (MAX). Conversely, LEV pretreatment enhanced both acute locomotor stimulation by 15 mg/kg cocaine and development of locomotor sensitization following repeated exposure and produced a leftward shift in the dose-response curve for cocaine on BSR threshold without affecting MAX. Electrophysiological recordings in vitro showed that LEV reduced excitatory currents in both ventral tegmental area (VTA) dopamine neurons and nucleus accumbens (NAc) medium spiny neurons, consistent with a presynaptic effect. The opposite effects of LEV pretreatment on alcohol- and cocaine-related behaviors may predict its clinical utility in the treatment of patients with alcohol, but not psychostimulant abuse disorders.

A new mechanism for antiepileptic drug action: vesicular entry may mediate the effects of levetiracetam

Levetiracetam (LEV) is one of the most commonly prescribed antiepileptic drugs, but its mechanism of action is uncertain. Based on prior information that LEV binds to the vesicular protein synaptic vesicle protein 2A and reduces presynaptic neurotransmitter release, we wanted to more rigorously characterize its effect on transmitter release and explain the requirement for a prolonged incubation period for its full effect to manifest. During whole cell patch recordings from rat hippocampal pyramidal neurons in vitro, we found that LEV decreased synaptic currents in a frequency-dependent manner and reduced the readily releasable pool of vesicles. When we manipulated spontaneous activity and stimulation paradigms, we found that synaptic activity during LEV incubation alters the time at which LEV's effect appears, as well as its magnitude. We believe that synaptic activity and concomitant vesicular release allow LEV to enter recycling vesicles to reach its binding site, synaptic vesicle protein 2A. In support of this hypothesis, a vesicular "load-unload" protocol using hypertonic sucrose in the presence of LEV quickly induced LEV's effect. The effect rapidly disappeared after unloading in the absence of LEV. These findings are compatible with LEV acting at an intravesicular binding site to modulate the release of transmitter and with its most marked effect on rapidly discharging neurons. Our results identify a unique neurobiological explanation for LEV's highly selective antiepileptic effect and suggest that synaptic vesicle proteins might be appropriate targets for the development of other neuroactive drugs.

Levetiracetam in submaximal subcutaneous pentylentetrazol-induced seizures in rats

Despite anticonvulsant efficacy in animal models of generalized epilepsy, levetiracetam was not effective in the maximal subcutaneous PTZ model in mice and rats. Aim of this study was to assess the efficacy of levetiracetam (LEV) against submaximal, s.c. MET test (PTZ at the dose of 70 mg/kg) acute seizures in Wistar rats, in comparison to valproic acid (VPA). Thirty male Wistar rats (P42) were divided in three drug-treatment groups (10 rats in each group) as follows: valproic acid, levetiracetam, and controls. All animals were tested for seizure threshold at age P50. VPA (110 mg/kg) and LEV (108 mg/kg) were freshly dissolved in saline and injected i.p. in 2-3 ml/kg, 15 and 30 min, respectively, before pentylenetetrazol (PTZ) injection at the dose of 70 mg/kg. The average latency of the seizure type 3 (generalized clonic seizure with loss of righting reflexes) significantly differed between controls and the drug-treated animal groups (p < or = 0.02). The average duration of the seizure type 2 (threshold seizure) was significantly longer in both groups compared to controls (<0.02). In conclusion, LEV plays a role against seizures triggered by subcutaneous PTZ injection given at submaximal doses in rats, as demonstrated by a significant increase in duration of the seizure type 2 (threshold seizure).

Levetiracetam enhances p53-mediated MGMT inhibition and sensitizes glioblastoma cells to temozolomide

Antiepileptic drugs (AEDs) are frequently used to treat seizures in glioma patients. AEDs may have an unrecognized impact in modulating O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair protein that has an important role in tumor cell resistance to alkylating agents. We report that levetiracetam (LEV) is the most potent MGMT inhibitor among several AEDs with diverse MGMT regulatory actions. In vitro, when used at concentrations within the human therapeutic range for seizure prophylaxis, LEV decreases MGMT protein and mRNA expression levels. Chromatin immunoprecipitation analysis reveals that LEV enhances p53 binding on the MGMT promoter by recruiting the mSin3A/histone deacetylase 1 (HDAC1) corepressor complex. However, LEV does not exert any MGMT inhibitory activity when the expression of either p53, mSin3A, or HDAC1 is abrogated. LEV inhibits malignant glioma cell proliferation and increases glioma cell sensitivity to the monofunctional alkylating agent temozolomide. In 4 newly diagnosed patients who had 2 craniotomies 7-14 days apart, prior to the initiation of any tumor-specific treatment, samples obtained before and after LEV treatment showed the inhibition of MGMT expression. Our results suggest that the choice of AED in patients with malignant gliomas may have an unrecognized impact in clinical practice and research trial design.

Intravenous levetiracetam in the rat pilocarpine-induced status epilepticus model: behavioral, physiological and histological studies

PURPOSE

Status epilepticus is a neurological emergency associated with neuronal injury, lasting behavioral disturbance, and a high rate of mortality. Intravenous levetiracetam (LEV), an anti-epileptic drug approved to treat partial seizures, has recently been introduced. We sought to determine the effect of LEV administered intravenously in a chemoconvulsant model of status epilepticus.

METHODS

We examined the effect of intravenous LEV in the rat lithium-pilocarpine model of status epilepticus. Ten or 30 min after the onset of behavioral status epilepticus, animals were treated with LEV (200-1200 mg/kg i.v.) administered in a single bolus. Behavioral responses were recorded. Selected animals had continuous EEG recording before, during and after the administration of LEV. Some animals were sacrificed 24 h after the experiment and processed for histochemical assessment of neuronal injury.

RESULTS

When administered 30 min after the onset of behavioral epileptic seizures, transient attenuation of ictal behavior was observed in animals treated with 800 mg/kg or more of LEV. The duration of behavioral attenuation increased sharply as the dose rose to 1000 mg/kg or higher, from a mean of 4-23.6 min. When administered 10 min after seizure onset, 400 mg/kg of LEV resulted in transient ictal behavioral attenuation, and higher doses caused relatively longer periods of attenuation. Pretreatment with LEV prior to pilocarpine also delayed the onset of seizures. EEG recordings, however, showed no significant attenuation of ictal discharge. By contrast, TUNEL staining demonstrated less neuronal injury in hippocampii and other limbic structures in animals that responded behaviorally to LEV.

CONCLUSIONS

Intravenous administration of LEV in a chemoconvulsant model of status epilepticus results in attenuation of behavioral manifestations of seizure discharge and in reduction of neuronal injury but does not significantly alter ictal discharge recorded by EEG.

Two years of experience in the treatment of status epilepticus with intravenous levetiracetam

Since its introduction in 2006, 43 patients with various forms of status epilepticus (SE) have been treated with the intravenous formulation of levetiracetam (LEV) in our clinic. After ineffective treatment with benzodiazepines, intravenous LEV was administered as a short infusion (nonconvulsive and subtle SE) at a dose of 1000 or 2000 mg. In cases of convulsive SE, a fractionated injection of 1000 or 2000 mg was used. When the results for both are combined, SE could be terminated in 19 of 43 patients. Intravenous LEV was more effective in simple focal SE (3/5), complex focal SE (11/18) and myoclonic status (2/2) than in nonconvulsive (2/8) and subtle (1/2) SE. In no case was (secondarily) generalized convulsive status epilepticus (0/8) terminated. Intravenous LEV was also well-tolerated when injected in fractionated form. No severe adverse reactions were observed. As a result of this investigation, intravenous LEV in moderate doses may represent an efficacious and well-tolerated alternative for the treatment of focal (simple and complex focal) and myoclonic SE. Further investigations are needed to confirm this assumption as the patient numbers are quite low.

Levetiracetam prevents kindling-induced asymmetric accumulation of hippocampal 7S SNARE complexes

PURPOSE

Understanding the molecular mechanisms underlying epilepsy is crucial to designing novel therapeutic regimens. This report focuses on alterations in the secretory machinery responsible for neurotransmitter (NT) release. Soluble N-ethylmaleimide sensitive factor (NSF) attachment protein receptor (SNARE) complexes mediate the fusion of synaptic vesicle and active zone membranes, thus mediating NT secretion. SNARE regulators control where and when SNARE complexes are formed. Previous studies showed an asymmetric accumulation of 7S SNARE complexes (7SC) in the ipsilateral hippocampus of kindled animals. The present studies probe the persistence of 7SC accumulation and the effect of the anticonvulsant, levetiracetam (LEV), on 7SC and SNARE regulators.

METHOD

Quantitative Western blotting was used to monitor levels of 7SC and SNARE regulators in hippocampal synaptosomes from kindled animals both before and after LEV treatment.

RESULTS

The asymmetric accumulation of 7SC is present 1-year postamygdalar kindling. The synaptic vesicle protein, synaptic vesicle protein 2 (SV2), a primary LEV-binding protein, and the SNARE regulator Tomosyn increase, whereas NSF decreases in association with this accumulation. Treatment with LEV prevented kindling-induced accumulation of SV2, but did not affect the transient increase of Tomosyn or the long-term decrease NSF. LEV treatment retarded the electrical and behavioral concomitants of amygdalar kindling coincident with a decrease in accumulation of 7SC.

CONCLUSIONS

The ipsilateral hippocampal accumulation of SNARE complexes is an altered molecular process associated with kindling that appears permanent. Kindling epileptogenesis alters synaptosomal levels of the SNARE regulators: NSF, SV2, and Tomosyn. Concomitant treatment with LEV reverses the kindling-induced 7SC accumulation and increase of SV2.

Prophylactic treatment with levetiracetam after status epilepticus: lack of effect on epileptogenesis, neuronal damage, and behavioral alterations in rats

Levetiracetam (LEV) is a structurally novel antiepileptic drug (AED) which has demonstrated a broad spectrum of anticonvulsant activities both in experimental and clinical studies. Previous experiments in the kindling model suggested that LEV, in addition to its seizure-suppressing activity, may possess antiepileptogenic or disease-modifying activity. In the present study, we evaluated this possibility by using a rat model in which epilepsy with spontaneous recurrent seizures (SRS), behavioral alterations, and hippocampal damages develop after a status epilepticus (SE) induced by sustained electrical stimulation of the basal amygdala. Two experimental protocols were used. In the first protocol, LEV treatment was started 24h after onset of electrical amygdala stimulation without prior termination of the SE. In the second protocol, the SE was interrupted after 4h by diazepam, immediately followed by onset of treatment with LEV. Treatment with LEV was continued for 8 weeks (experiment #1) or 5 weeks (experiment #2) after SE, using continuous drug administration via osmotic minipumps. The occurrence of SRS was recorded during and after treatment. In addition, the rats were tested in a battery of behavioral tests, including the elevated-plus maze and the Morris water maze. Finally, the brains of the animals were analyzed for histological lesions in the hippocampal formation. With the experimental protocols chosen for these experiments, LEV did not exert antiepileptogenic or neuroprotective activity. Furthermore, the behavioral alterations, e.g., behavioral hyperexcitability and learning deficits, in epileptic rats were not affected by treatment with LEV after SE. These data do not support the idea that administration of LEV after SE prevents or reduces the long-term alterations developing after such brain insult in rats.

The efficacy and tolerability of levetiracetam in pharmacoresistant epileptic dogs

Twenty-two dogs with idiopathic epilepsy which were pharmacoresistant to phenobarbitone and bromide were treated with levetiracetam as an add-on medication. Records of eight dogs were used retrospectively to determine a safe, efficient levetiracetam dosage. Fourteen dogs were entered into a prospective, open label, non-comparative study. After 2 months of levetiracetam oral treatment (10 mg/kg TID), 8/14 dogs responded significantly to the treatment and seizure frequency was reduced by 50%. In dogs that remained refractory, the dosage was increased to 20 mg/kg TID for 2 months. One further dog responded to levetiracetam treatment. Levetiracetam responders had a significant decrease in seizure frequency of 77% (7.9+/-5.2 to 1.8+/-1.7 seizures/month) and a decrease in seizure days per month of 68% (3.8+/-1.7 to 1.2+/-1.1 seizure days/month). However, 6/9 responders experienced an increase in seizure frequency and seizure days after 4-8 months continuing with the levetiracetam treatment at the last effective dosage. Levetiracetam was well tolerated by all dogs and sedation was the only side-effect reported in just one of the 14 dogs.

The pharmacokinetics of antiepileptic drugs in rats: consequences for maintaining effective drug levels during prolonged drug administration in rat models of epilepsy

Rodent models of chronic epilepsy with spontaneous recurrent seizures likely represent the closest parallel to the human condition. Such models may be best suited for therapy discovery for pharmacoresistant epilepsy and for antiepileptogenic or disease-modifying therapeutics. However, the use of such rodent models for therapy discovery creates problems with regard to maintaining effective drug levels throughout a prolonged testing period. This is particularly due to the fact that rodents such as rats and mice eliminate most drugs much more rapidly than humans. Thus, knowledge about elimination rate of a test drug in a laboratory species is essential for development of a treatment paradigm that allows maintaining adequate drug levels in the system over the period of treatment. Currently, the most popular models of epilepsy with spontaneous seizures are poststatus epilepticus models of temporal lobe epilepsy in rats. Such models are both used for studies on antiepileptogenesis and drug resistance. For validation of these models, current antiepileptic drugs (AEDs) have to be used. In this article, the elimination rates of these AEDs and their effective plasma levels in rats are reviewed as a guide for developing treatment protocols for chronic drug testing. The advantages and disadvantages of several technologies for drug delivery are discussed, and some examples for calculation of adequate treatment protocols are given. As shown in this review, because of the rapid elimination of most AEDs in rats, it is no trivial task to maintain effective steady-state AED levels in the plasma throughout the day over multiple days to ensure that there will be adequate levels in the system for the purpose of the experiment. However, the use of an adequate dosing regimen that is based on elimination rate is an absolute prerequisite when using rat models for discovery of new antiepileptogenic therapies or therapies for pharmacoresistant epilepsy, because otherwise such models may lead to erroneous conclusions about drug efficacy.

Single-dose pharmacokinetics of levetiracetam in healthy Chinese male subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Levetiracetam has been evaluated for epilepsy since 1992. * Pharmacokinetic studies of levetiracetam have been conducted in healthy volunteers, in adults, children and elderly patients with epilepsy, and in patients with renal and hepatic impairment. * Although this antiepileptic has been well studied in Western countries, this paper describes the first such trial of the drug in a Chinese population.

WHAT THIS STUDY ADDS

* Information is given on the pharmacokinetics, dose proportionality, safety and tolerability profile of levetiracetam in healthy male Chinese volunteers, and the results are compared with published data obtained in White subjects. * The pharmacokinetics and the pattern of adverse events of levetiracetam in Chinese subjects are similar to the data reported in White subjects.

AIMS

The main aims of this study were to evaluate the pharmacokinetics of levetiracetam in healthy male Chinese volunteers and to assess the dose proportionality between the 500-mg and 1500-mg single doses.

METHODS

This was a randomized, single-centre, single-dose, two-way crossover study. Twenty-six healthy male Chinese subjects were enrolled. All subjects received a single dose of 500 mg or 1500 mg levetiracetam tablet(s) on the dosing day, and the wash-out period was 7 days. Blood was obtained for a 36-h pharmacokinetic evaluation.

RESULTS

Following single-dose administration of 500 mg and 1500 mg of levetiracetam, the median t(max) was 0.5 and 0.5 h; t(1/2) was 7.3 +/- 0.8 and 7.3 +/- 0.7 h; C(max) was 13.6 +/- 3.2 and 47.1 +/- 12.1 microg ml(-1); AUC(0-infinity) was 109.3 +/- 14.1 and 340.4 +/- 50.6 microg h(-1) ml(-1); and AUC(0-t) was 105.7 +/- 13.3 and 329.0 +/- 47.9 microg h(-1) ml(-1), respectively.

CONCLUSIONS

Both C(max) and AUCs were dose-proportional over the range of 500-1500 mg. The pharmacokinetic data obtained in these Chinese subjects were similar to the historical data from a matched group of White subjects.

Levetiracetam and felbamate interact both pharmacodynamically and pharmacokinetically: an isobolographic analysis in the mouse maximal electroshock model

PURPOSE

Polytherapy with two or more antiepileptic drugs (AEDs) is generally required for approximately 30% of patients with epilepsy, who do not respond satisfactorily to monotherapy. The potential usefulness of AED combinations, producing synergistic anticonvulsant efficacy and minimal adverse effects, is therefore of significant importance. The present study sought to ascertain the potential usefulness of levetiracetam (LEV) and felbamate (FBM) in combination in the mouse maximal electroshock (MES)-induced seizure model.

METHODS

The anticonvulsant interaction profile between LEV and FBM in the mouse MES-induced seizure model was determined using type II isobolographic analysis. Acute adverse effects (motor performance) were ascertained by use of the chimney test. LEV and FBM brain concentrations were measured by HPLC in order to determine any pharmacokinetic contribution to the observed antiseizure effect.

RESULTS

LEV in combination with FBM, at the fixed ratios of 1:2, 1:1, 2:1, and 4:1, were supraadditive, whereas at the fixed ratio of 1:4, additivity was observed in the mouse MES model. Furthermore, none of the investigated combinations altered motor performance in the chimney test. Brain FBM concentrations were unaffected by concomitant LEV administration. In contrast, FBM significantly increased LEV brain concentrations.

CONCLUSIONS

LEV in combination with FBM was associated with pharmacodynamic supraadditivity in the MES test. However, this anticonvulsant supraadditivity was associated with a concurrent increase in brain LEV concentrations indicating a pharmacokinetic contribution to the observed pharmacodynamic interaction between LEV and FBM.