The acute and chronic effects of the novel anticonvulsant lacosamide in an experimental model of status epilepticus

Efficacy of Lacosamide and Rufinamide as Adjuncts to Midazolam-Ketamine Treatment Against Cholinergic-Induced Status Epilepticus in Rats

Benzodiazepine pharmacoresistance develops when treatment of status epilepticus (SE) is delayed. This response may result from gamma-aminobutyric acid A receptors (GABAAR) internalization that follows prolonged SE; this receptor trafficking results in fewer GABAAR in the synapse to restore inhibition. Increase in synaptic N-methyl-D-aspartate receptors (NMDAR) also occurs in rodent models of SE. Lacosamide, a third-generation antiseizure medication (ASM), acts on the slow inactivation of voltage-gated sodium channels. Another ASM, rufinamide, similarly acts on sodium channels by extending the duration of time spent in the inactivation stage. Combination therapy of the benzodiazepine midazolam, NMDAR antagonist ketamine, and ASMs lacosamide (or rufinamide) was investigated for efficacy against soman (GD)-induced SE and neuropathology. Adult male rats implanted with telemetry transmitters for monitoring electroencephalographic (EEG) activity were exposed to a seizure-inducing dose of GD and treated with an admix of atropine sulfate and HI-6 1 minute later and with midazolam monotherapy or combination therapy 40 minutes after EEG seizure onset. Rats were monitored continuously for seizure activity for two weeks, after which brains were processed for assessment of neurodegeneration, neuronal loss, and neuroinflammatory responses. Simultaneous administration of midazolam, ketamine, and lacosamide (or rufinamide) was more protective against GD-induced SE compared with midazolam monotherapy. In general, lacosamide triple therapy had more positive outcomes on measures of epileptogenesis, EEG power integral, and the number of brain regions protected from neuropathology compared with rats treated with rufinamide triple therapy. Overall, both drugs were well tolerated in these combination models. SIGNIFICANCE STATEMENT: We currently report on improved efficacy of antiseizure medications lacosamide and rufinamide, each administered in combination with ketamine (NMDAR antagonist) and midazolam (benzodiazepine), in combatting soman (GD)-induced seizure, epileptogenesis, and brain pathology over that provided by midazolam monotherapy, or dual therapy of midazolam and lacosamide (or rufinamide) in rats. Administration of lacosamide as adjunct to midazolam and ketamine was particularly effective against GD-induced toxicity. However, protection was incomplete, suggesting the need for further study.

Effect of Lacosamide and Ethosuximide Chronic Treatment on Neural Precursor Cells and Cognitive Functions after Pilocarpine Induced Status Epilepticus in Mice

Seizures in about 40% of patients with epilepsy fail to respond to anti-seizure medication (ASM) and may lead to uncontrolled and prolonged seizures often inducing status epilepticus (SE). The aim of the study was to evaluate the impact of a long-term treatment with two different generation ASMs: ethosuximide (ETS, a classic ASM) and lacosamide (LCM, a 3rd generation ASM) on neural stem cells’ (NSCs’) proliferation and learning and memory functions after pilocarpine (PILO)-induced SE in mice. The following drugs were used: LCM (10 mg/kg), ETS (20 mg/kg), and PILO (300 mg/kg). Cell counting was done using confocal microscope and ImageJ software. Cognitive functions were evaluated with the Morris water maze (MWM) test. The level of several selected neurometabolites was measured with magnetic resonance spectroscopy (MRS). Obtained results indicated no significant impact of ETS treatment on the neurogenesis process in PILO mice. Interestingly, LCM significantly decreased the total amount of newborn neurons. The MWM test indicated no significant changes in the time and distance traveled by the ETS and LCM groups compared to PILO control mice, although all measured parameters were more favorable for the PILO mice treated with ASM. Conclusions: The presented results show that long term treatment with LCM and ETS seems to be safe for the cognitive functions and the proper course of neurogenesis in the mouse PILO-induced SE model, although one should remember that LCM administered chronically may act to reduce new neurons’ formation.

Antiepileptic Drug Therapy for Status Epilepticus

Status epilepticus (SE) is one of the most serious neurologic emergencies. SE is a condition that encompasses a broad range of semiologic subtypes and heterogeneous etiologies. The treatment of SE primarily involves the management of the underlying etiology and the use of antiepileptic drug therapy to rapidly terminate seizure activities. The Drug Committee of the Korean Epilepsy Society performed a review of existing guidelines and literature with the aim of providing practical recommendations for antiepileptic drug therapy. This article is one of a series of review articles by the Drug Committee and it summarizes staged antiepileptic drug therapy for SE. While evidence of good quality supports the use of benzodiazepines as the first-line treatment of SE, such evidence informing the administration of second- or third-line treatments is lacking; hence, the recommendations presented herein concerning the treatment of established and refractory SE are based on case series and expert opinions. The choice of antiepileptic drugs in each stage should consider the characteristics and circumstances of each patient, as well as their estimated benefit and risk to them. In tandem with the antiepileptic drug therapy, careful searching for and treatment of the underlying etiology are required.

Role of Lacosamide in Preventing Pentylenetetrazole Kindling-Induced Alterations in the Expression of the Gamma-2 Subunit of the GABAA Receptor in Rats

Background:

Epilepsy remains challenging to treat still no etiologic treatment has been identified, however, some antiepileptic drugs (AEDs) are able to modify the pathogenesis of the disease. Lacosamide (LCM) has been shown to possess complex anticonvulsant and neuroprotective actions, being an enhancer of the slow inactivation of voltage-gated sodium channels, and it has the potential to prevent epileptogenesis. Recent evidence has shown that LCM indirectly improves the function of GABAA receptors. Receptors at most GABAergic synapses involve the gamma-2 subunit, which contributes to both phasic and tonic inhibition, and its presence assures benzodiazepine sensitivity. Moreover, mutant gamma-2 subunits were associated with generalized epilepsy syndromes. In animal models, the expression of the gamma-2 subunit of the gamma-aminobutyric acid A receptor (GABAAg2) was shown to be increased in pentylenetetrazole (PTZ)-induced chemical kindling in Wistar rats.

Objective:

This study hypothesized that LCM might affect the kindling process by influencing the expression of GABAA receptors in the hippocampus.

Methods:

The gene and protein expression levels of the GABAAg2 were studied using RT-qPCR and immunofluorescent staining.

Results:

It was found that LCM treatment (10 mg/kg i.p. daily for 57 days) reduced the maximal intensity of the PTZ-induced seizures but did not prevent kindling. On the other hand, LCM treatment reverted the increase of mRNA expression of GABAAg2 in the hippocampus and prevented the decrease of GABAAg2 protein in the hippocampal CA1 region.

Conclusion:

LCM could exhibit modulatory effects on the GABAergic system of the hippocampus that may be independent of the anticonvulsant action.

Effects of Carbamazepine, Lacosamide and Zonisamide on Gliotransmitter Release Associated with Activated Astroglial Hemichannels

Recent studies using the genetic partial epilepsy model have demonstrated that hyperfunction of astroglial hemichannels contributes to pathomechanism of epileptic seizure. Therefore, to explore the novel anticonvulsive mechanisms, the present study determined the effects of voltage-dependent Na⁺ channel (VDSC)-inhibiting anticonvulsants, carbamazepine (CBZ), lacosamide (LCM), and zonisamide (ZNS) on the astroglial release of l-glutamate and adenosine triphosphate (ATP). The effects of subchronic administration of therapeutic-relevant dose of three anticonvulsants on the release of l-glutamate and ATP in the orbitofrontal cortex (OFC) were determined using microdialysis. The concentration-dependent effects of acute and subchronic administrations of anticonvulsants on astroglial gliotransmitter release were determined using primary cultured astrocytes. The concentration-dependent effects of subchronic administrations of anticonvulsants on connexin43 (Cx43) expression in the plasma membrane of primary cultured astrocytes were determined using the Simple Western system. An increase in the levels of extracellular K⁺ resulted in a concentration-dependent increase in the astroglial release of l-glutamate and ATP. The depleted levels of extracellular Ca²⁺ alone did not affect astroglial gliotransmitter release but did accelerate K⁺-evoked gliotransmitter release via activation of astroglial hemichannels. Both non-selective hemichannel inhibitor carbenoxolone (CBX) and selective Cx43 inhibitor GAP19 prevented both gliotransmitter release through activated astroglial hemichannels and the hemichannel-activating process induced by elevation of the levels of extracellular K⁺ with depletion of the levels of extracellular Ca²⁺. ZNS subchronically decreased Cx43 expression and acutely/subchronically inhibited Cx43 hemichannel activity. LCM acutely inhibited hemichannel activity but did not subchronically affect Cx43 expression. Therapeutic-relevant concentration of CBZ did not affect hemichannel activity or Cx43 expression, but supratherapeutic concentration of CBZ decreased Cx43 expression and hemichannel activity. Therefore, the present study demonstrated the distinct effects of CBZ, LCM, and ZNS on gliotransmitter release via modulation of astroglial hemichannel function. The different features of the effects of three VDSC-inhibiting anticonvulsants on astroglial transmission associated with hemichannels, at least partially, possibly contributing to the formation of the properties of these three anticonvulsants, including the antiepileptic spectrum and adverse effects regarding mood and cognitive disturbance.

Pharmacotherapy for Refractory and Super-Refractory Status Epilepticus in Adults

Patients with prolonged seizures that do not respond to intravenous benzodiazepines and a second-line anticonvulsant suffer from refractory status epilepticus and those with seizures that do not respond to continuous intravenous anesthetic anticonvulsants suffer from super-refractory status epilepticus. Both conditions are associated with significant morbidity and mortality. A strict pharmacological treatment regimen is urgently required, but the level of evidence for the available drugs is very low. Refractory complex focal status epilepticus generally does not require anesthetics, but all intravenous non-anesthetizing anticonvulsants may be used. Most descriptive data are available for levetiracetam, phenytoin and valproate. Refractory generalized convulsive status epilepticus is a life-threatening emergency, and long-term clinical consequences are eminent. Administration of intravenous anesthetics is mandatory, and drugs acting at the inhibitory gamma-aminobutyric acid (GABA)_A receptor such as midazolam, propofol and thiopental/pentobarbital are recommended without preference for one of those. One in five patients with anesthetic treatment does not respond and has super-refractory status epilepticus. With sustained seizure activity, excitatory N-methyl-d-aspartate (NMDA) receptors are increasingly expressed post-synaptically. Ketamine is an antagonist at this receptor and may prove efficient in some patients at later stages. Neurosteroids such as allopregnanolone increase sensitivity at GABA_A receptors; a Phase 1/2 trial demonstrated safety and tolerability, but randomized controlled data failed to demonstrate efficacy. Adjunct ketogenic diet may contribute to termination of difficult-to-treat status epilepticus. Randomized controlled trials are needed to increase evidence for treatment of refractory and super-refractory status epilepticus, but there are multiple obstacles for realization. Hitherto, prospective multicenter registries for pharmacological treatment may help to improve our knowledge.

Agomelatine alleviates neuronal loss through BDNF signaling in the post-status epilepticus model induced by kainic acid in rat

Recently, we have reported that while agomelatine (Ago) is unable to prevent development of epilepsy it exerts a strong neuroprotective and anti-inflammatory response in the KA post-status epilepticus (SE) rat model. In the present study, we aimed to explore whether the brain-derived neurotrophic factor (BDNF) in the hippocampus is involved in the neuroprotective effect of Ago against the KA-induced SE and epileptiform activity four months later in rats. Lacosamide (LCM) was used as a positive control. The EEG-recorded seizure activity was also evaluated in two treatment protocols. In Experiment#1, Ago given repeatedly at a dose of 40 mg/kg during the course of SE was unable neither to modify EEG-recorded epileptiform activity nor the video- and EEG-recorded spontaneous seizures four months later compared to LCM (50 mg/kg). However, both Ago and LCM inhibited the expression of BDNF in the mossy fibers and also prevented neuronal loss in the dorsal hippocampal and the piriform cortex after SE. In Experiment#2, acute injection of Ago and LCM on epileptic rats, characterized by high seizure rates, did not prevent EEG-recorded paroxysmal events while only LCM decreased either absolute or relative powers of gamma (28-60 Hz) and high (HI) (60-120 Hz) frequency bands to baseline in the frontal and parietal cortex, respectively. Our results suggest that the protection against neuronal loss in specific limbic regions and overexpressed BDNF in the mossy fibers resulting from the repeated treatment with Ago and LCM, respectively, during SE is not a prerequisite for alleviation of epileptogenesis and development of epilepsy. In addition, a reduction of gamma and HI bands in the frontal and parietal cortex is not associated with EEG-recorded paroxysmal events after acute injection of LCM.

Intravenous lacosamide (LCM) in status epilepticus (SE): Weight-adjusted dose and efficacy

BACKGROUND

Some studies suggest higher efficacy of lacosamide (LCM) in status epilepticus (SE) with higher loading doses; however, this weight-adjusted dose has not been evaluated.

OBJECTIVE

The objective was to evaluate the relationship between loading weight-adjusted dose and efficacy of LCM in SE.

METHODS

A group of patients with SE treated with LCM from Spanish hospitals was examined retrospectively. Demographic data, type of SE, etiology, response rate, last antiepileptic drug (AED) used, treatment line in which LCM was used, total loading dose, and weight-adjusted dose were collected.

RESULTS

One hundred sixty-five cases of SE were collected; 87 (52.7%) patients had nonconvulsive SE. Mean age was 64.2 ± 17.2 and 60.6% (n = 100) were men. Regarding etiology, SE was considered as acute symptomatic in 85 (51.5%), remote symptomatic in 51 (30.9%), progressive symptomatic in 10 (6.1%), and cryptogenic in 19 (11.5%). Lacosamide was used as the third drug in 46.1%, and as a second option in 28%. In 115 patients, clonazepam had been used as the first option, and no benzodiazepines had been administered in the remaining 50. The median loading dose was 400 mg (100-600 mg), and the weight-adjusted dose was 5 mg/kg (3-6 mg/kg). The response rate was 63.3%, and 55.1% responded within the first 12 h. Efficacy was significantly higher in patients who had taken benzodiazepines at LCM loading doses >5.3 mg/kg (p = 0.006). This relationship was maintained independent of using other concomitant AEDs. However, if benzodiazepines were not taken, this relationship was not found.

CONCLUSIONS

In adults with benzodiazepine-resistant SE, the response rate to LCM was higher, with weight-adjusted doses above 5.3 mg/kg.

Inverted-U response of lacosamide on pilocarpine-induced status epilepticus and oxidative stress in C57BL/6 mice is independent of hippocampal collapsin response mediator protein-2

OBJECTIVE

Currently, lacosamide (LCM) is not approved for use in status epilepticus (SE) but several shreds of evidence are available to support its use. The present study was, therefore, undertaken to evaluate the effect of LCM on pilocarpine (PILO) induced SE and neurodegeneration in C57BL/6 mice and to ascertain the involvement of CRMP-2 in mediating above effect.

METHODS

Pilocarpine-induced SE model was developed to explore the effect of LCM 20, 40 and 80 mg/kg in mice. We assessed the seizure severity, seizure latency, spontaneous alternation behavior (SAB) and motor coordination by behavioral observation. Histopathological evaluation and measurement of the levels of CRMP-2, reduced glutathione (GSH) and malondialdehyde (MDA) were carried out in mice hippocampus.

RESULTS

LCM exhibited a biphasic effect i.e., protection against SE at 20 mg/kg and 40 mg/kg dose whilst aggravated seizure-like behavior and mortality at 80 mg/kg. Further, it increased percentage alternation (i.e., restored spatial memory) in SAB and elevated motor impairment with increasing dose. Histologically, LCM 20 mg/kg and 40 mg/kg (but not 80 mg/kg) reduced neurodegeneration. LCM 20 mg/kg and 40 mg/kg reversed the elevated MDA and GSH levels while 80 mg/kg showed a tendency to increase oxidative stress. In contrast, LCM (at all doses) reversed the pilocarpine-induced elevation of collapsin response mediator protein-2 (CRMP-2).

CONCLUSION

LCM protected against pilocarpine-induced SE, associated neurodegeneration and improved pilocarpine-associated impairment of spatial memory. The study reveals that CRMP-2 may not be mediating the inverted-U-response of LCM at least in pilocarpine model. Therefore, the anti-oxidant effect of LCM (and not its ability to modulate CRMP-2) was anticipated as the mechanism underlying neuroprotection.

Comparison of lacosamide versus sodium valproate in status epilepticus: A pilot study

PURPOSE

The purpose of this study was to compare the efficacy and safety of lacosamide (LCM) and sodium valproate (SVA) in lorazepam (LOR)-resistant SE.

METHODS

Patients with LOR-resistant SE were randomized to intravenous LCM 400mg at the rate of 60mg/kg/min or SVA 30mg/kg at the rate of 100mg/min. The SE severity score (STESS), duration of SE and its etiology, and MRI findings were noted. Primary outcome was seizure cessation for 1h, and secondary outcomes were 24h seizure remission, in-hospital death, and severe adverse events (SAE).

RESULTS

Sixty-six patients were included, and their median age was 40 (range 18-90) years. Thirty-three patients each received LCM and SVA. Their demographic, clinical, STESS, etiology, and MRI findings were not significantly different. One-hour seizure remission was not significantly different between LCM and SVA groups (66.7% vs 69.7%; P=0.79). Twenty-four-hour seizure freedom was insignificantly higher in SVA (20, 66.6%) compared with LCM group (15, 45.5%). Death (10 vs 12) and composite side effects (4 vs 6) were also not significantly different in LCM and SVA groups. LCM was associated with hypotension and bradycardia (1 patient), and SVA with liver dysfunction (6).

CONCLUSION

In patients with LOR-resistant SE, both LCM and SVA have comparable efficacy and safety.

Acute and long-term effects of brivaracetam and brivaracetam-diazepam combinations in an experimental model of status epilepticus

Objective

To evaluate acute and long‐term effects of intravenous brivaracetam (BRV) and BRV + diazepam (DZP) combination treatment in a rat model of self‐sustaining status epilepticus (SSSE).

Methods

Rats were treated with BRV (10 mg/kg) 10 min after initiation of perforant path stimulation (PPS) as early treatment; or BRV (10–300 mg/kg), DZP (1 mg/kg), or BRV (0.3–10 mg/kg) + DZP (1 mg/kg) 10 min after the end of PPS (established SSSE). Seizure activity was recorded electrographically for 24 h posttreatment (acute effects), and for 1 week at 6–8 weeks or 12 months' posttreatment (long‐term effects). All treatments were compared with control rats using one‐way analysis of variance (ANOVA) and Bonferroni's test, or Kruskal‐–Wallis and Dunn's multiple comparison tests, when appropriate.

Results

Treatment of established SSSE with BRV (10–300 mg/kg) resulted in dose‐dependent reduction in SSSE duration and cumulative seizure time, achieving statistical significance at doses ≥100 mg/kg. Lower doses of BRV (0.3–10 mg/kg) + low‐dose DZP (1 mg/kg) significantly reduced SSSE duration and number of seizures. All control rats developed spontaneous recurrent seizures (SRS) 6–8 weeks after SSSE, whereas seizure freedom was noted in 2/10, 5/10, and 6/10 rats treated with BRV 200 mg/kg, 300 mg/kg, and BRV 10 mg/kg + DZP, respectively. BRV (10–300 mg/kg) showed a dose‐dependent trend toward reduction of SRS frequency, cumulative seizure time, and spike frequency, achieving statistical significance at 300 mg/kg. Combination of BRV (10 mg/kg) + DZP significantly reduced SRS frequency, cumulative seizure time, and spike frequency. In the 12‐month follow‐up study, BRV (0.3–10 mg/kg) + low‐dose DZP markedly reduced SRS frequency, cumulative seizure time, and spike frequency, achieving statistical significance at some doses. Early treatment of SSSE with BRV 10 mg/kg significantly reduced long‐term SRS frequency.

Significance

These findings support clinical evaluation of BRV for treatment of status epilepticus or acute repetitive seizures.

A randomized controlled trial of lacosamide versus sodium valproate in status epilepticus

OBJECTIVE

To compare the efficacy and safety of lacosamide (LCM) and sodium valproate (SVA) in lorazepam (LOR)-resistant status epilepticus (SE).

METHODS

Patients with LOR-resistant SE were randomized to intravenous LCM 400 mg at a rate of 60 mg/kg/min or SVA 30 mg/kg at a rate of 100 mg/min. The SE severity score (STESS), duration of SE and its etiology, and magnetic resonance imaging (MRI) findings were noted. Primary outcome was seizure cessation for 1 h, and secondary outcomes were 24 h seizure remission, in hospital death and severe adverse events (SAEs).

RESULTS

Sixty-six patients were included, and their median age was 40 (range 18-90) years. Thirty-three patients each received LCM and SVA. Their demographic, clinical, STESS, etiology, and MRI findings were not significantly different. One hour seizure remission was not significantly different between LCM and SVA groups (66.7% vs. 69.7%; p = 0.79). Twenty-four hour seizure freedom was higher in SVA (20, 66.6%) compared with LCM group (15, 45.5%), but this difference was not statistically significant. Death (10 vs. 12) and composite side effects (4 vs. 6) were also not significantly different in LCM and SVA groups. LCM was associated with hypotension and bradycardia (one patient), and SVA with liver dysfunction (six patients).

SIGNIFICANCE

In LOR-resistant SE patients, both LCM and SVA have comparable efficacy and safety. SVA resulted in slightly better 24 h seizure remission.

Intravenous lacosamide in clinical practice-Results from an independent registry

PURPOSE

This non-interventional study was conducted to evaluate the efficacy and tolerability of intravenous lacosamide (LCM-iv) under routine conditions in daily clinical practice as a prospective registry.

METHODS

Patients with any type of seizure or epilepsy syndrome were recruited in 16 neurological and neuropediatric centers in Germany if the treating physician decided to administer LCM-iv for any reason. Observation time per patient was 10 days with daily documentation of LCM-iv administration, type and frequency of seizures, currently used drugs and doses, and adverse events. Treatment efficacy, tolerability, and handling of LCM-iv were assessed using a five-step scale.

RESULTS

In 119 patients treating physicians classified epilepsies as focal in 66.1% and generalized in 17.4% (16.5% unclassifiable). Most common etiologies of seizures were tumors (36.1%) and cerebrovascular diseases (21.8%). Reasons for LCM-iv treatment included preparation for surgery (25.2%), convulsive (24.4%) and non-convulsive (18.5%) status epilepticus (SE), series of seizures (16.0%), gastrointestinal causes (5.9%), and acute seizures (4.2%). The median dose of LCM-iv was 300mg per day. In 45 of 64 patients (70.3%) with SE or series of seizures, epileptic activity ceased during observation time. Five patients showed abnormalities in ECG prior to the infusion and one patient afterwards, but during infusion no abnormalities were reported. Treating physicians rated efficacy and tolerability as very good or good in 77.6% and 93.1% of patients, respectively.

CONCLUSIONS

This large and independent multicenter registry on the use of LCM-iv in clinical practice demonstrates that LCM-iv is well-tolerated and highly efficacious when given in emergency situations, including patients experiencing SE. It is advisable to perform an electrocardiogram prior to LCM-iv administration.

Novel antiepileptic drug lacosamide exerts neuroprotective effects by decreasing glial activation in the hippocampus of a gerbil model of ischemic stroke

Lacosamide, which is a novel antiepileptic drug, has been reported to exert various additional therapeutic effects. The present study investigated the neuroprotective effects of lacosamide against transient cerebral ischemia-induced neuronal cell damage in the hippocampal cornu ammonis (CA)-1 region of a gerbil model. Neuronal Nuclei immunohistochemistry demonstrated that pre- and post-surgical treatment (5 min ischemia) with 25 mg/kg lacosamide protected CA1 pyramidal neurons in the lacosamide-treated-ischemia-operated group from ischemic injury 5 days post-ischemia, as compared with gerbils in the vehicle-treated-ischemia-operated group. Furthermore, treatment with 25 mg/kg lacosamide markedly attenuated the activation of astrocytes and microglia in the ischemic CA1 region at 5 days post-ischemia. The results of the present study suggested that pre- and post-surgical treatment of the gerbils with lacosamide was able to protect against transient cerebral ischemic injury-induced CA1 pyramidal neuronal cell death in the hippocampus. In addition, the neuroprotective effects of lacosamide may be associated with decreased activation of glial cells in the ischemic CA1 region.

Lacosamide modulates interictal spiking and high-frequency oscillations in a model of mesial temporal lobe epilepsy

OBJECTIVE

Nearly one third of patients presenting with mesial temporal lobe epilepsy (MTLE), the most prevalent lesion-related epileptic disorder in adulthood, do not respond to currently available antiepileptic medications. Thus, there is a need to identify and characterize new antiepileptic drugs. In this study, we used the pilocarpine model of MTLE to establish the effects of a third generation drug, lacosamide (LCM), on seizures, interictal spikes and high-frequency oscillations (HFOs, ripples: 80-200 Hz, fast ripples: 250-500 Hz).

METHODS

Sprague-Dawley rats (250-300 g) were injected with pilocarpine to induce a status epilepticus (SE) that was pharmacologically terminated after 1h. Eight pilocarpine-treated rats were then injected with LCM (30 mg/kg, i.p.) 4h after SE and daily for 14 days. Eight pilocarpine-treated rats were used as controls and treated with saline. Three days after SE, all rats were implanted with bipolar electrodes in the hippocampal CA3 region, entorhinal cortex (EC), dentate gyrus (DG) and subiculum and EEG-video monitored from day 4 to day 14 after SE.

RESULTS

LCM-treated animals showed lower rates of seizures (0.21 (± 0.11) seizures/day) than controls (2.6 (±0.57), p<0.05), and a longer latent period (LCM: 11 (± 1) days, controls: 6.25 (± 1), p<0.05). Rates of interictal spikes in LCM-treated rats were significantly lower than in controls in CA3 and subiculum (p<0.05). Rates of ripples and fast ripples associated with interictal spikes in CA3 and subiculum as well as rates of fast ripples occurring outside of interictal spikes in CA3 were also significantly lower in LCM-treated animals. In controls, interictal spikes and associated HFOs correlated to seizure clustering, while this was not the case for isolated HFOs.

SIGNIFICANCE

Our findings show that early treatment with LCM has powerful anti-ictogenic properties in the pilocarpine model of MTLE. These effects are accompanied by decreased rates of interictal spikes and associated HFOs. Isolated HFOs were also modulated by LCM, in a manner that appeared to be unrelated to its antiictogenic effects. These results thus suggest that distinct mechanisms may underlie interictal-associated and isolated HFOs in the pilocarpine model of MTLE.

Pharmacotherapy for Status Epilepticus

Status epilepticus (SE) represents the most severe form of epilepsy. It is one of the most common neurologic emergencies, with an incidence of up to 61 per 100,000 per year and an estimated mortality of 20 %. Clinically, tonic-clonic convulsive SE is divided into four subsequent stages: early, established, refractory, and super-refractory. Pharmacotherapy of status epilepticus, especially of its later stages, represents an "evidence-free zone," due to a lack of high-quality, controlled trials to inform clinical decisions. This comprehensive narrative review focuses on the pharmacotherapy of SE, presented according to the four-staged approach outlined above, and providing pharmacological properties and efficacy/safety data for each antiepileptic drug according to the strength of scientific evidence from the available literature. Data sources included MEDLINE and back-tracking of references in pertinent studies. Intravenous lorazepam or intramuscular midazolam effectively control early SE in approximately 63-73 % of patients. Despite a suboptimal safety profile, intravenous phenytoin or phenobarbital are widely used treatments for established SE; alternatives include valproate, levetiracetam, and lacosamide. Anesthetics are widely used in refractory and super-refractory SE, despite the current lack of trials in this field. Data on alternative treatments in the later stages are limited. Valproate and levetiracetam represent safe and effective alternatives to phenobarbital and phenytoin for treatment of established SE persisting despite first-line treatment with benzodiazepines. To date there are no class I data to support recommendations for most antiepileptic drugs for established, refractory, and super-refractory SE. Limiting the methodologic heterogeneity across studies is required and high-class randomized, controlled trials to inform clinicians about the best treatment in established and refractory status are needed.

Lacosamide as adjunctive therapy in refractory epilepsy in adults: a systematic review

PURPOSE

To review the evidence for efficacy and safety of lacosamide in adult patients with refractory epilepsy and refractory status epilepticus (RSE).

METHODS

A systematic literature search of MEDLINE, PubMed, EMBASE, IPA, Google and Google Scholar (through October 2014) was performed.

RESULTS

Fourteen studies assessing lacosamide in 3509 refractory epilepsy patients were included. In 3 RCTs, more patients had at least 50% reduction in seizure frequency with lacosamide compared to placebo with 38.3-41.1%, 38.1-41.2%, and 18.3-25.8%, in the 400 mg/day, 600 mg/day, and placebo groups, respectively. In non-comparative trials, 18-69% of patients achieved at least 50% reduction in seizure frequency, and 1.7-26.2% achieved seizure freedom. Non-responders were documented in two trials, with 26.2-34% having no response. Thirteen studies assessing lacosamide in 390 RSE patients were included. When assessing lacosamide's ability to terminate RSE, one comparative cohort study found no improvement in SE duration or seizure control with addition of lacosamide. Another study documented no difference compared to use of phenytoin. Eleven descriptive studies using lacosamide as add-on RSE therapy revealed seizure termination rates of 0-100% (median 64.7%). In all patients receiving lacosamide, dizziness (21.8%), vision disturbances (10.4%), drowsiness (7.4%), headache (7.0%), nausea (6.5%), and coordination problems (5.8%) were the most common adverse effects.

CONCLUSION

Based on evidence to date, adjunctive lacosamide is a treatment option to reduce seizure frequency in patients with refractory epilepsy and terminate seizures in patients with RSE. The safety information summary can be used to advise patients of potential adverse effects.

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

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

Synergism of lacosamide with established antiepileptic drugs in the 6-Hz seizure model in mice

PURPOSE

Lacosamide (LCM, Vimpat) is an anticonvulsant with a unique mode of action. This provides lacosamide with the potential to act additively or even synergistically with other antiepileptic drugs (AEDs). The objective of this study was to determine the presence of such interactions by isobolographic analysis.

METHODS

The anticonvulsant effect of LCM in combination with other AEDs including carbamazepine (CBZ), phenytoin (PHT), valproate (VPA), lamotrigine (LTG), topiramate (TPM), gabapentin (GBP), and levetiracetam (LEV) at fixed dose ratios of 1:3, 1:1, and 3:1, was evaluated in the 6-Hz-induced seizure model in mice. In addition, the impact of the combinations of LCM with the other AEDs on motor coordination was assessed in the rotarod test. Finally, AED concentrations were measured in blood and brain to evaluate potential pharmacokinetic drug interactions.

KEY FINDINGS

All studied AEDs produced dose-dependent anticonvulsant effects against 6-Hz-induced seizures. Combinations of LCM with CBZ, LTG, TPM, GBP, or LEV were synergistic. All other LCM/AED combinations displayed additive effects with a tendency toward synergism. Furthermore, no enhanced adverse effects were observed in the rotarod test by combining LCM with other AEDs. No pharmacokinetic interactions were seen on brain AED concentrations. Coadministration of LCM and TPM led to an increase in plasma levels of LCM, whereas the plasma concentration of PHT was increased by coadministration of LCM.

SIGNIFICANCE

The synergistic anticonvulsant interaction of LCM with various AEDs, without exacerbation of adverse motor effects, highlights promising properties of LCM as add-on therapy for drug refractory epilepsy.

Lacosamide treatment following status epilepticus attenuates neuronal cell loss and alterations in hippocampal neurogenesis in a rat electrical status epilepticus model

PURPOSE

The antiepileptic drug, lacosamide, exerts its therapeutic activity by enhancing slow inactivation of voltage-gated sodium channels. Because putative preventive or disease-modifying effects of drugs may affect epileptogenesis, intrinsic severity, and comorbidities, it is of particular interest to assess the effect of lacosamide on the development of epilepsy and associated cellular alterations.

METHODS

The effect of lacosamide was evaluated in an electrical rat status epilepticus (SE) model with a 24-day treatment phase following induction of SE. The impact of lacosamide on the development of spontaneous seizures based on continuous video-electroencephalography (EEG) monitoring, as well as the impact on neuronal cell loss and alterations in hippocampal neurogenesis, was assessed.

KEY FINDINGS

Neither low-dose nor high-dose lacosamide affected the development of spontaneous seizures. A dose-dependent neuroprotective effect of lacosamide with significant reduction of neuronal cell loss was observed in the hippocampal CA1 region, as well as in the piriform cortex. In addition, lacosamide attenuated the impact of SE on the rate of hippocampal cell neurogenesis. Moreover, lacosamide prevented a significant rise in the number of persistent basal dendrites.

SIGNIFICANCE

Our data do not support an antiepileptogenic effect of lacosamide. However, because lacosamide reduced SE-associated cellular alterations, it would be of interest to determine whether these effects indicate a putative disease-modifying effect of lacosamide in future studies.

Lacosamide as a new treatment option in status epilepticus

Status epilepticus is among the most common neurologic emergencies, with a mortality rate of up to 20%. The most important therapeutic goal is fast, effective, and well-tolerated cessation of status epilepticus. Intravenous phenytoin/fosphenytoin, phenobarbital, or valproate is the current standard treatment after failure of benzodiazepines. Lacosamide as a new antiepileptic drug has been available as an intravenous solution since 2009. To date, PubMed lists 19 studies (10 single case reports and 9 case series), reporting a total of 136 episodes of refractory status epilepticus (50% nonconvulsive status epilepticus, 31% focal status epilepticus, and 19% convulsive status epilepticus) treated with lacosamide. The most often used bolus dose was 200-400 mg over 3-5 min. The overall success rate was 56% (76/136). Adverse events (AEs) were reported in 25% (34/136) of patients: mild sedation in 25 cases, 1 patient with possible angioedema, 2 with allergic skin reaction, 4 with hypotension, and 1 with pruritus. One patient developed a third-degree atrioventricular (AV) block and paroxysmal asystole. Overall, the rate of AEs was low. Current evidence on the use of intravenous lacosamide in acute seizures and status epilepticus is restricted to retrospective case reports and case series (class IV). Further prospective studies to inform clinicians are necessary.

Comparative study of lacosamide and classical sodium channel blocking antiepileptic drugs on sodium channel slow inactivation

Many antiepileptic drugs (AEDs) exert their therapeutic activity by modifying the inactivation properties of voltage-gated sodium (Na(v) ) channels. Lacosamide is unique among AEDs in that it selectively enhances the slow inactivation component. Although numerous studies have investigated the effects of AEDs on Na(v) channel inactivation, a direct comparison of results cannot be made because of varying experimental conditions. In this study, the effects of different AEDs on Na(v) channel steady-state slow inactivation were investigated under identical experimental conditions using whole-cell patch-clamp in N1E-115 mouse neuroblastoma cells. All drugs were tested at 100 μM, and results were compared with those from time-matched control groups. Lacosamide significantly shifted the voltage dependence of Na(v) current (I(Na) ) slow inactivation toward more hyperpolarized potentials (by -33 ± 7 mV), whereas the maximal fraction of slow inactivated channels and the curve slope did not differ significantly. Neither SPM6953 (lacosamide inactive enantiomer), nor carbamazepine, nor zonisamide affected the voltage dependence of I(Na) slow inactivation, the maximal fraction of slow inactivated channels, or the curve slope. Phenytoin significantly increased the maximal fraction of slow inactivated channels (by 28% ± 9%) in a voltage-independent manner but did not affect the curve slope. Lamotrigine slightly increased the fraction of inactivated currents (by 15% ± 4%) and widened the range of the slow inactivation voltage dependence. Lamotrigine and rufinamide induced weak, but significant, shifts of I(Na) slow inactivation toward more depolarized potentials. The effects of lacosamide on Na(v) channel slow inactivation corroborate previous observations that lacosamide has a unique mode of action among AEDs that act on Na(v) channels.

Efficacy of intravenous lacosamide as an add-on treatment in refractory status epilepticus: a multicentric prospective study

OBJECTIVE

Treatment of status epilepticus (SE) has not changed in the last few decades, benzodiazepines plus phenytoin or valproate being the most common treatment. Once this first and second line treatment has failed SE is considered refractory (RSE). This study aimed to assess the efficacy and tolerability of intravenous (iv) lacosamide (LCM) in RSE.

METHOD

Patients with RSE who were treated with ivLCM in six Spanish centers were prospectively included. Efficacy was defined as cessation of seizures after starting ivLCM, with no need for any further antiepileptic drug. All patients had been unsuccessfully treated following the standard protocol (benzodiazepines plus phenytoin or valproate) before ivLCM was added.

RESULTS

Thirty-four patients were included, 52.9% men, with mean age of 60.15 years. In 58.9% of patients the etiology was symptomatic, and the most common type of SE was focal convulsive (82.4%). Mean initial bolus dose of LCM was 323.53mg. ivLCM was effective in more than half of patients (64.7%), with termination of SE before 12h in 50% of them. ivLCM was used as a fourth or later option in 76.5% of patients. No serious adverse events attributable to LCM were reported.

CONCLUSIONS

LCM might be a fast, effective and safe add-on treatment in RSE.

What is the evidence to use new intravenous AEDs in status epilepticus?

Current standard treatment of established status epilepticus after failure of benzodiazepines is intravenous phenytoin/fosphenytoin, phenobarbital, or valproate. Since 2006 two new antiseizure drugs have become available as intravenous formulation: levetiracetam (2006) and lacosamide (2008). Both drugs have been taken up very rapidly by the clinicians to treat acute seizures and status epilepticus, despite lack of evidence from randomized controlled trials. The favorable pharmacokinetic profile and the good tolerability, especially the lack of sedating effects of both drugs make them promising potential alternatives to the standard antiseizure drugs. Future randomized controlled trials are needed to inform clinicians better about the best choice of treatment in established status epilepticus. The experimental evidence as well as the current clinical experience with levetiracetam and lacosamide are summarized in this review.

Intravenous lacosamide in status epilepticus and seizure clusters

Status epilepticus (SE) and seizure clusters (SC) represent neurologic emergencies with a case fatality rate up to 34%, depending on cause and comorbidity. As SE becomes more refractory to treatment over time, appropriate medication is important. This study aimed to investigate efficacy and tolerability of intravenous (IV) lacosamide (LCM) in treatment of SC and SE. Data of patients with SE or SC who were treated with IV LCM between December 2009 and February 2011 in two Austrian centers were analyzed retrospectively. Clinical information was extracted from patients' charts. Forty-eight patients (26f/22m) aged median 62 years (range 17-95 years) were identified. Thirty-five percent of patients (17 of 48) had SC and 65% (31 of 48) had SE. SE was nonconvulsive in 10 (32%), convulsive in 11 (36%), and focal in 10 (32%) patients. SE was acute symptomatic in six (20%) and remote symptomatic in 11 (35%) patients. Fourteen (45%) had preexisting epilepsy. Median initial bolus dose was 200 mg (range 200-400 mg) in patients with SE and 200 mg in patients with SC. Maximum infusion rate was 60 mg/min. Cessation was observed in 42 patients (88%). Success rate in patients with SE receiving LCM as first or second drug was 100% (8 of 8), as third drug 81% (11 of 15), and as fourth or later drug 75% (6 of 8). There were no side effects observed except for pruritus and skin rash in two patients. These data support use of IV LCM as a potential alternative to standard antiepileptic drugs for acute treatment of seizure emergency situations, although randomized controlled studies are needed.