The anti-epileptic drug levetiracetam reverses the inhibition by negative allosteric modulators of neuronal GABA- and glycine-gated currents

Choosing the correct antiepileptic drugs: from animal studies to the clinic

Epilepsy is a chronic condition caused by an imbalance of normal excitatory and inhibitory forces in the brain. Antiepileptic drug therapy is directed primarily toward reducing excitability through blockage of voltage-gated Na(+) or Ca(2+) channels, or increasing inhibition through enhancement of gamma-aminobutyric acid currents. Prior to clinical studies, putative antiepileptic drugs are screened in animals (usually rodents). Maximal electrical shock, pentylenetetrazol, and kindling are typically used as nonmechanistic screens for antiseizure properties, and the rotorod test assesses acute toxicity. Whereas antiseizure drug screening has been successful in bringing drugs to the market and improving our understanding of the pathophysiology of seizures, it merits emphasis that the vast majority of drug screening occurs in mature male rodents and involves models of seizures, not epilepsy. Effective drugs in acute seizures may not be effective in chronic models of epilepsy. Seizure type, clinical and electroencephalographic phenotype, syndrome, and etiology are often quite different in children with epilepsy than in adults. Despite these age-related unique features, drugs used in children are generally the same as those in adults. As awareness of the unique features of seizures during development increases, more drug screening in the immature animal will likely occur.

Modifications of Antiepileptic Drugs for Improved Tolerability and Efficacy

Introduction

A large number of antiepileptic drugs (AEDs) are available today, but they may not be satisfactory regarding clinical efficacy, tolerance, toxicity or pharmacokinetic properties. The purpose of this review is to focus upon the rationale behind the chemical modifications of several recently marketed AEDs or drugs in development and to categorize them according to the main purposes for the improvements: better efficacy or tolerability accompanied by improved pharmacokinetic properties.

Material and Method

AEDs that have been chemically modified to new derivatives during the last years are reviewed based on recent publications and PubMed-searches.

Results and Discussion

Improvement in pharmacokinetic parameters may affect both tolerability and efficacy. Modifications to improve tolerability include various valproate analogues, divided into aliphatic amides, cyclic derivatives or amino acid conjugates. Furthermore, there are the carbamazepine analogues oxcarbazepine and eslicarbazepine, the felbamate analogues fluorofelbamate and carisbamate (RWJ 33369), and the lamotrigine analogue JZP-4. The levetiracetam analogues brivaracetam and seletracetam and the derivatives of gabapentin, pregabalin and XP13512, have improved selectivity compared to their parent compounds. Other new drugs have new mechanisms of action related to GABA and glutamate receptors; the glutamate antagonists like topiramate (talampanel and NS-1209), and GABAA receptor agonists, benzodiazepine or progesterone analogues (ELB-139 and ganaxolone).

Conclusion

Further challenges for development of new AEDs include investigations of target molecules affected by pathophysiological processes and detailed structure-activity relationships with focus on stereoselectivity. These potential drugs may become of importance in future drug therapy in epilepsy and other CNS disorders.

Modifications of antiepileptic drugs for improved tolerability and efficacy

INTRODUCTION

A large number of antiepileptic drugs (AEDs) are available today, but they may not be satisfactory regarding clinical efficacy, tolerance, toxicity or pharmacokinetic properties. The purpose of this review is to focus upon the rationale behind the chemical modifications of several recently marketed AEDs or drugs in development and to categorize them according to the main purposes for the improvements: better efficacy or tolerability accompanied by improved pharmacokinetic properties.

MATERIAL AND METHOD

AEDs that have been chemically modified to new derivatives during the last years are reviewed based on recent publications and PubMed-searches.

RESULTS AND DISCUSSION

Improvement in pharmacokinetic parameters may affect both tolerability and efficacy. Modifications to improve tolerability include various valproate analogues, divided into aliphatic amides, cyclic derivatives or amino acid conjugates. Furthermore, there are the carbamazepine analogues oxcarbazepine and eslicarbazepine, the felbamate analogues fluorofelbamate and carisbamate (RWJ 33369), and the lamotrigine analogue JZP-4. The levetiracetam analogues brivaracetam and seletracetam and the derivatives of gabapentin, pregabalin and XP13512, have improved selectivity compared to their parent compounds. Other new drugs have new mechanisms of action related to GABA and glutamate receptors; the glutamate antagonists like topiramate (talampanel and NS-1209), and GABA(A) receptor agonists, benzodiazepine or progesterone analogues (ELB-139 and ganaxolone).

CONCLUSION

Further challenges for development of new AEDs include investigations of target molecules affected by pathophysiological processes and detailed structure-activity relationships with focus on stereoselectivity. These potential drugs may become of importance in future drug therapy in epilepsy and other CNS disorders.

Levetiracetam has no acute effects on brain gamma-aminobutyric acid levels

OBJECTIVE

The mechanism of action of levetiracetam (LEV), an antiepileptic drug, is related to a novel binding site, SV2, but LEV acts on GABA-A receptors. The objective of the study described here was to determine if LEV modulates brain GABA in vivo.

METHODS

Concentrations of cerebral GABA and serum LEV were obtained in seven healthy individuals using 1H magnetic resonance spectroscopy at baseline and 3 and 6 hours following oral administration of 1 g of LEV.

RESULTS

Brain cerebral GABA acutely concentrations did not change from baseline.

CONCLUSION

The results indicate that LEV does not increase human cerebral GABA concentrations acutely in healthy individuals.

Levetiracetam in juvenile myoclonic epilepsy: long-term efficacy in newly diagnosed adolescents

The aim of this study was to evaluate the efficacy and tolerability of levetiracetam (LEV) monotherapy in juvenile myoclonic epilepsy (JME). The study group consisted of 32 patients with epilepsy (20 males, 12 females) with a mean age of 13 years 3 months (SD 7y 11mo) at seizure onset. LEV was administered as the first drug; all patients were followed up at 6 and 12 months. The dose that achieved seizure control ranged from 1000 to 2500mg/daily. At 6-month evaluation: 15 patients were seizure free; 14 patients were responders (>50% reduction in seizures); and three patients had marginal effects (<50% reduction of seizures). At 12-month evaluation: 29 patients were seizure free; three patients were responders. No patients reported adverse events. These data provide preliminary evidence that LEV may be effective for treating patients with newly diagnosed JME.

Clinical pharmacology and mechanism of action of zonisamide

Antiepileptic drugs (AEDs) suppress seizures by selectively modifying the excitability of neurons and blocking seizure firing with minimal disturbance of nonepileptic activity. All AEDs have been shown to work by at least one of 3 main mechanisms of action: through modulation of voltage-gated ion channels, enhancement of synaptic inhibition, and inhibition of synaptic excitation. Zonisamide is a novel AED that has a broad combination of complementary mechanisms of action, which may offer a clinical advantage over other antiepileptic agents. By altering the fast inactivation threshold of voltage-dependent sodium channels, zonisamide reduces sustained high-frequency repetitive firing of action potentials. Zonisamide also inhibits low-threshold T-type calcium channels in neurons, which may prevent the spread of seizure discharge across cells. In addition, zonisamide is a weak inhibitor of carbonic anhydrase. However, this mechanism is not believed to contribute to the antiepileptic activity of zonisamide. Although zonisamide also seems to alter dopamine, serotonin, and acetylcholine metabolism, it is not clear to what extent these effects on neurotransmitters are involved in the clinical actions of the drug. In addition to these actions, recent evidence suggests that zonisamide may exert neuroprotective actions, independent of its antiepileptic activity. These potential effects may be important in preventing neuronal damage caused by recurrent seizures. Therefore, it seems that the multiple pharmacological actions of zonisamide may contribute to the seizure reductions observed in a wide range of epilepsies and may help to preserve efficacy in individual patients despite possible changes in electrophysiological status.

Levetiracetam-responding paroxysmal nonkinesigenic dyskinesia

We report on a patient with 7-year history of short-lasting paroxysmal nonkinesigenic dyskinesia. The episodes occurred 100 to 125 times per day, lasted from 5 seconds to 3 minutes, and were not suppressed with sleeping, underlining the heterogeneity of phenomenology in paroxysmal dyskinesias. Neuroimaging studies showed calcifications in the basal ganglia, thalamus, brain stem, and subcortical and cerebellar regions. He was diagnosed with idiopathic hypoparathyroidism. After failure of valproate, he responded well to levetiracetam (1000 mg/d). This report revealed that intracerebral calcifications secondary to hypoparathyroidism could present as paroxysmal nonkinesigenic dyskinesia, and levetiracetam could be effective in this particular entity.

Brivaracetam is superior to levetiracetam in a rat model of post-hypoxic myoclonus

In the present study, we evaluated the anti-seizure and anti-myoclonic activity of levetiracetam and brivaracetam in an established rat model of cardiac arrest-induced post-hypoxic myoclonus. We found that brivaracetam (0.3 mg/kg, the minimal effective dose) was more potent than levetiracetam (3 mg/kg, the minimal effective dose) against post-hypoxic seizures. The anti-seizure activity of both compounds occurred 30 min following intraperitoneal (i.p.) administration and was maintained over the entire 150 min post-dose observation period. Both brivaracetam and levetiracetam significantly reduced auditory stimulated post-hypoxic myoclonus from a dose 0.3 mg/kg. At that dose, the anti-myoclonic activity of brivaracetam was already maximal whereas it continued to increase in a dose-relation manner with levetiracetam, suggesting that brivaracetam is a more potent agent. The onset and the duration of anti-myoclonic activity of both compounds were similar. These findings demonstrate that brivaracetam possesses more potent anti-seizure and anti-myoclonic activity than levetiracetam in an established rat model of cardiac arrest-induced post-hypoxic myoclonus.

Tuberous sclerosis successfully treated with levetiracetam monotherapy: 18 months of follow-up

CASE

We present the case of a boy with tuberous sclerosis who was referred for evaluation and treatment of his intractable epileptic seizures, having failed multiple anti-epileptic drug trials. He was subsequently treated with Levetiracetam that was gradually titrated to an effective dose, achieving full suppression of his seizures. Thereafter, his concomitant anti-epileptic drugs were gradually reduced and eventually discontinued. He remained on monotherapy with Levetiracetam, which continued to fully control his seizures. His EEG tracings before and after treatment are presented and compared, showing normalization of the latter.

CONCLUSION

Levetiracetam appears to be effective in treatment-resistant seizures which are symptomatic to tuberous sclerosis when used adjunctively as well as in monotherapy. This is the first report in the English literature regarding its use and efficacy in this condition.

Levetiracetam in the treatment of childhood epilepsy

Epilepsy is a common pediatric neurologic disorder that is difficult to manage in a substantial portion of children. Levetiracetam (LEV) is a novel antiepileptic drug (AED) that has recently been approved as add-on treatment for various seizure types in epilepsy populations that include children: for refractory partial seizures in epilepsy patients >/=4 years old, for myoclonic seizures in juvenile myoclonic epilepsy patients >/=12 years old, and for primary generalized tonic-clonic seizures in idiopathic generalized epilepsy patients (>/=6 years old with FDA approval; >/=12 years old with EMEA approval). A review of published pediatric studies indicates that the efficacy of LEV is best established for partial seizures; however, results from recent double-blind and open-label trials indicate that adjunctive LEV also controls generalized seizures - particularly myoclonic and generalized tonic-clonic - in children and adolescents with primary generalized epilepsy. LEV was well-tolerated in pediatric studies. The most common adverse events (AEs) reported were sedation related. Behavioral AEs were among the most commonly reported events in some trials; conversely, improvements in behavior and cognition were also frequently reported. LEV appears to be a safe and effective AED with unique characteristics that benefit the treatment of children with epilepsy.

Levetiracetam: the profile of a novel anticonvulsant drug-part I: preclinical data

The objective of this article was to review and summarize the available reports on the preclinical profile of the novel anticonvulsant drug levetiracetam (LEV). Therefore, a careful search was conducted in the MEDLINE database and combined with guidelines from regulatory agencies, proceedings of professional scientific meetings, and information provided by the manufacturers. This article provides detailed information on the anticonvulsant effects of LEV in various animal models of epilepsy and on its pharmacology in laboratory animals. The mechanism of action of LEV is reviewed, with special regard to its recently discovered binding site, the synaptic vesicle protein 2A. In general, LEV is shown to be a safe, broad-spectrum anticonvulsant drug with highly beneficial pharmacokinetic properties and a distinct mechanism of action. The clinical studies with LEV will be discussed in the second part of this review article to be published subsequently.

Influence of levetiracetam on the anticonvulsant efficacy of conventional antiepileptic drugs against audiogenic seizures in DBA/2 mice

Levetiracetam (LEV, [S]-alpha-ethyl-2-oxo-1-pyrrolidine acetamide) is a new antiepileptic that has been used as adjunctive therapy to treat patients with intractable epilepsy. Systemic administration of levetiracetam (2.5-30 mg/kg, intraperitoneally (i.p.)) was able to produce a dose-dependent decrease in DBA/2 audiogenic seizure severity score. In combination with conventional antiepileptic drugs, levetiracetam, 5mg/kg, i.p., which per se did not significantly affect the occurrence of audiogenic seizures in DBA/2 mice, potentiated the anticonvulsant activity of some antiepileptic drugs studied against sound-induced seizures in DBA/2 mice. The degree of potentiation induced by levetiracetam was greater, approximately twice, for carbamazepine, diazepam, felbamate, topiramate, gabapentin, and valproate, less for lamotrigine, phenobarbital and phenytoin. This increase was associated with a comparable impairment in motor activity; however, the therapeutic index of combined treatment of antiepileptic drugs with levetiracetam was more favourable than the combination with saline with the exception of lamotrigine, phenytoin and phenobarbital. Since levetiracetam did not significantly influence the total and free plasma and the brain levels of antiepileptics studied. In addition, levetiracetam did not significantly affect the hypothermic effects of the anticonvulsants tested. In conclusion, levetiracetam showed an additive anticonvulsant effect when administered in combination with some classical anticonvulsants, most notably carbamazepine, diazepam, felbamate, gabapentin, topiramate and valproate, implicating a possible therapeutic relevance of such drug combinations.

Levetiracetam for the treatment of hot flashes: a phase II study

GOALS OF WORK

The objectives of this pilot trial were to assess the potential efficacy and safety of levetiracetam for the treatment of hot flashes, a major cause of morbidity among breast cancer survivors.

PATIENTS AND METHODS

Women, aged 18 years or more, with a history of breast cancer or those who wished to avoid estrogen because of a perceived increased risk of breast cancer, who were experiencing bothersome hot flashes (more than or equal to 14 times per week, for more than or equal to 1 month before study entry), were included. During the baseline week, general demographic characteristics, hot flash information, and quality of life data were obtained. At the beginning of week 2, patients were started on levetiracetam for a total of 4 weeks. Information about hot flashes, quality of life, and toxicity were collected during these 4 weeks and compared with the baseline week.

MAIN RESULTS

After treatment with levetiracetam for 4 weeks (N = 19), mean hot flash scores (frequency times mean severity) were reduced by 57%, and mean hot flash frequencies were reduced by 53%, compared to the baseline week; both these reductions were greater than what would be expected with a placebo (20-25% reduction). There were significant improvements in abnormal sweating (p = 0.004), hot flash distress (p = 0.0002), and satisfaction of hot flash control (p = 0.0001), when comparing data from the fourth week of treatment to the baseline week. Twenty-nine percent of the subjects did not complete the study because of treatment-related adverse events, with the most frequently reported side effects being somnolence, fatigue, and dizziness, usually with mild to moderate intensity.

CONCLUSION

The results of this pilot trial suggest that levetiracetam might be an effective therapy for the treatment of hot flashes. Further data are needed to test this hypothesis, evaluating the efficacy and toxicity of this agent.

Efficacy and safety of levetiracetam in infants and young children with refractory epilepsy

The aim of this multicentric, retrospective, and uncontrolled study was to evaluate the efficacy and safety of levetiracetam (LEV) in 81 children younger than 4 years with refractory epilepsy. At an average follow-up period of 9 months, LEV administration was found to be effective in 30% of patients (responders showing more than a 50% decrease in seizure frequency) of whom 10 (12%) became seizure free. This efficacy was observed for focal (46%) as well as for generalized seizures (42%). In addition, in a group of 48 patients, we compared the initial efficacy (evaluated at an average of 3 months of follow-up) and the retention at a mean of 12 months of LEV, with regard to loss of efficacy (defined as the return to the baseline seizure frequency). Twenty-two patients (46%) were initial responders. After a minimum of 12 months of follow-up, 9 of 48 patients (19%) maintained the improvement, 4 (8%) of whom remained seizure free. A loss of efficacy was observed in 13 of the initial responders (59%). Maintained LEV efficacy was noted in patients with focal epilepsy and West syndrome. LEV was well tolerated. Adverse events were seen in 18 (34%) patients. The main side effects were drowsiness and nervousness. Adverse events were either tolerable or resolved in time with dosage reduction or discontinuation of the drug. We conclude that LEV is safe and effective for a wide range of epileptic seizures and epilepsy syndromes and, therefore, represents a valid therapeutic option in infants and young children affected by epilepsy.

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.

Potential of levetiracetam in mood disorders: a preliminary review

Levetiracetam is a newer antiepileptic agent that was first approved by the US FDA in 1999 as an adjunctive therapy for the treatment of refractory partial epilepsy in adults. Since then, it has been approved for a wider patient population, i.e. as adjunctive therapy for partial seizures in patients >4 years of age (worldwide) and as first-line monotherapy for partial seizures in patients >16 years of age (in Europe); and as adjunctive therapy for juvenile myoclonic seizures (in Europe and the US). It has a favourable pharmacokinetic profile and appears to act at a specific site in the CNS. Pharmacodynamic evidence indicates that levetiracetam indirectly facilitates GABAergic function, and an increasing body of evidence suggests an important role for GABA in the pathophysiology of mood disorders. Preclinical studies using animal models of depression, anxiety and mania provide evidence for levetiracetam as a mood stabiliser. Preliminary clinical evidence from case reports and open-label pilot studies indicates that the drug, both as add-on therapy and as monotherapy, has efficacy in a wide range of bipolar spectrum disorders. Most recently, a 31% remission rate was reported in patients with bipolar disorder who were in the depressed phase at baseline and who received levetiracetam as add-on therapy for 8 weeks in an open-label trial. While these results are encouraging, placebo-controlled data are needed to further clarify the role of levetiracetam in the treatment of mood disorders.

Retrospective analysis of the efficacy and tolerability of levetiracetam in patients with metastatic brain tumors

Seizures are a common complication of metastatic brain tumors (MBT), affecting approximately 27-50% of all patients during the course of their illness. Treatment of tumor-induced seizures is often inadequate with traditional antiepileptic drugs (AED) due to a variety of factors, including activation of glutamatergic NMDA receptors, alterations of neuronal input pathways, and tumor growth. Levetiracetam (LEV) is a 2nd generation non-enzyme inducing AED with a novel mechanism of action, binding to neuronal synaptic vesicle protein SV2A, that has been previously shown to reduce seizure activity in patients with primary brain tumors. Due to its unique mechanism of action, it has been postulated that LEV may also be effective in controlling seizures from MBT. A retrospective chart review was performed of all Neuro-Oncology Center patients with MBT who had received LEV for seizure control. Thirteen patients were reviewed with a median age of 55.1 years (range: 34-70). Six patients had breast cancer, five had lung cancer, and two had melanoma. LEV was used as an add-on AED in seven patients (54%) and as monotherapy in six patients (46%), with a median dose of 1,000 mg/day (range: 500-3,000). The baseline median seizure frequency was one ictal event every other day. After the addition of LEV, the median seizure frequency was reduced to 0 per week. The seizure frequency was reduced to less than 50% of the pre-LEV baseline in 100% of patients (P=0.0002, Sign test), with 10 patients (77%; confidence interval: 46-95%) noting complete seizure control. The most common adverse event was somnolence and headache, noted in 3 of 13 patients (23%). LEV was very effective and well tolerated in MBT patients with seizures and should be considered for add-on therapy or as a substitute AED for monotherapy.

Modulation of AMPA Receptors in Cultured Cortical Neurons Induced by the Antiepileptic Drug Levetiracetam

PURPOSE

The present study explores the hypothesis that the antiepileptic mechanism of action of levetiracetam (LEV) is related to effects on alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor channels in mouse cortical neurons in culture.

METHODS

The neurons were subjected to the whole-cell configuration of the patch-clamp recording technique and were 8-12 days old in culture.

RESULTS

Kainate elicited concentration-dependent (EC(50)= 80 microM) inward currents in all the patched cells. LEV (5-200 microM) itself did not induce inward or outward currents on all patched neurons, whereas it was effective on the kainate- and AMPA-induced current because it significantly decreased the amplitude of these currents. LEV was also able to significantly decrease the total membrane conductance during kainate perfusion, indicating that its effect was not dependent on the cellular voltage membrane potential. Further evidence that LEV modulated the ionotropic non-NMDA receptors came from the analysis of miniature excitatory postsynaptic currents (mEPSCs). In fact, LEV significantly decreased both the amplitude and the frequency of mEPSCs, as shown by the relative cumulative distributions.

CONCLUSIONS

These results reveal that AMPA receptors are modulated by LEV because a significant decrease in the kainate- and AMPA-induced currents and a decrease in amplitude and in frequency of mEPSCs have been observed in cortical neurons in culture. The described effect of LEV on AMPA receptors in cortical neurons is probably due to the etheromeric composition of the receptors and may be considered as a possible new antiepileptic mechanism of action.

Effect of levetiracetam on molecular regulation of hippocampal glutamate and GABA transporters in rats with chronic seizures induced by amygdalar FeCl3 injection

Enhancement of the glutamatergic excitatory synaptic transmission efficacy in the FeCl3 induced epilepsy model is associated with changes in the levels of glutamate and GABA transporter proteins. This study examined the effect of levetiracetam (LEV) on glutamate overflow and glutamate/GABA transporters expression in rats with epileptogenesis induced by the amygdalar injection of 1.0 microl of 100 mM FeCl3 (epileptic rat) and in control rats receiving amygdalar acidic saline injection (non-epileptic rat). In amygdalar acidic saline injected rats, 40 mM KCl-evoked glutamate overflow was significantly suppressed by both 32 and 100 microM LEV co-perfusion. In unilateral amygdalar FeCl3 injected rats, 32 microM LEV was ineffective, but the 100 microM LEV statistically suppressed glutamate overflow. Western blotting was employed to determine the hippocampal expression of glutamate/GABA transporters in epileptic or non-epileptic rats. The rats were treated for 14 days with 54 mg/kg LEV or vehicle intraperitoneally injection. Following 14 days of treatment, the ipsilateral hippocampus was removed for a Western blot analysis. In non-epileptic rats, the expression increased for all of the glutamate and GABA transporters (GLAST, GLT-1, EAAC-1, GAT-1 and GAT-3) while the glutamate transporter regulating protein (GTRAP3-18) decreased in comparison to those of normal rats that were treated with the vehicle. In epileptic rats receiving LEV, the EAAC-1 and GAT-3 levels increased while GTRAP3-18 (89%) decreased in comparison to those of the epileptic rats treated with the vehicle. GTRAP3-18 inhibitor regulates glutamate-binding affinity to EAAC-1. The anti-epileptic action of LEV may be partially due to a reduction of glutamate-induced excitotoxicity and an enhancement of the GABAergic inhibition as observed with the inhibitory effect on the 40 mM KCl-evoked glutamate overflow. These conclusions are supported by the increase in the expression of glial glutamate transporters (GLAST and GLT-1), and the increase in the expression of EAAC-1 and GAT-3 associated with a decrease in GTRAP3-18. The increased expression of EAAC-1 and the decreased expression of GTRAP3-18 in association with the up-regulation of GAT-3 due to such continual LEV administration was thus found to enhance GABA synthesis and reverse the transport of GABA both in non-epileptic and epileptic rats. The suppression of glutamate excitation and the enhancement of GABA inhibition in the rats with continual LEV administration is a result of the up-regulation of glutamate and GABA transporters with the down-regulation of GTRAP3-18. These observations together demonstrated the critical molecular mechanism of the anti-epileptic activity of LEV.

Anticonvulsants in sports: ethical considerations

OBJECTIVE

Antidoping codes in sport are intended to deter and sanction athletes using performance-enhancing agents while promoting an even playing field for all competitors. Although the World Anti-Doping Code (WADC) permits anticonvulsants in general, harmonization of antidoping permits an international sport federation (IF) to prohibit specific medications within that IF. The anticonvulsants levetiracetam, tiagabine, and lamotrigine may pose ethical dilemmas and could be considered violations of antidoping codes.

METHOD

This study is a literature review with analysis.

RESULTS

Lamotrigine, with antiglutamatergic and sodium channel properties, is FDA-approved for maintenance treatment of bipolar disorder, in addition to its use in the treatment of major depression, anxiety disorders, and schizophrenia. Tiagabine, a selective GABA reuptake inhibitor, has mood-stabilizing and anxiolytic properties. Levetiracetam, whose unique mechanism involves the modulators beta-carboline and zinc, has anxiolytic and mood-stabilizing properties. Anxiolytics, antidepressants, and antipsychotics are banned in archery; under strict liability, all three anticonvulsants violate WADC/IF for that specific sport and could result in disqualification unless therapeutic use exemptions (TUEs) are obtained. Ethical issues regarding the use of anticonvulsants by athletes and the need to obtain TUEs are addressed.

CONCLUSION

The WADC with harmonized IF policies are meant to prevent doping by athletes, but not appropriate medical treatment. When anticonvulsants have other psychotropic properties, ethical issues arise. Athletes should list all medications taken with diagnoses, obtain TUEs as indicated, and contact the appropriate IF or Olympic organization to determine the status of the proposed medication (banned, restricted, nonbanned). Further, clinicians should be knowledgeable regarding these issues when treating athletes.

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.

Influence of levetiracetame on ictal and postictal EEG in patients with partial seizures

To investigate the influence of levetiracetame (LEV) treatment on the interhemispheric seizure pattern propagation and postictal recovery of electroencephalography (EEG) background activity. Twenty-three adult patients (age > 16 years) with pharmacoresistant focal epilepsies presenting at the Epilepsy Center Erlangen for pre-surgical evaluation were enrolled in the study. Those eligible patients receiving only one antiepileptic drugs were recruited to the 48-h baseline phase and, after at least two seizures, were randomized to the 7-day treatment phase with either LEV (n = 11) or placebo (n = 12). All participants were submitted to continuous day-and-night video-EEG monitoring. The daily dose of LEV was 1000 mg (500 mg bid.) on the first treatment day and was increased to 2000 mg (1000 mg bid.) from the second day onward. The EEG changes relating to the time delay of the interhemispheric seizure pattern propagation and to the postictal recovery of the background activity were analysed by computerized video-EEG recording and compared using the non-parameter Mann-Whitney U-exact test (alpha = 0.05). A prolonged latency of the contralateral seizure pattern propagation was observed in the LEV group, whereas a more rapid propagation was observed in the placebo group (P = 0.009). Postictal generalized slowing of the background activity was recorded in 21 patients during the baseline phase. More rapid postictal recovery of the EEG background activity was observed in the LEV, but not in the placebo group (P = 0.03). This study demonstrated that LEV not only prevented the seizure pattern propagation but also helped the speedy recovery of the postictal background activity in the EEG.

Levetiracetam in three cases of progressive myoclonus epilepsy

We present three unrelated cases of genetically confirmed progressive myoclonic epilepsy of the Unverricht-Lundborg type who were treated with Levetiracetam as adjunctive therapy for their myoclonus. All cases responded with decrease of their myoclonus and improvement of quality of life. Two were able to return to or continue their employment. Patients tolerated the drug well without side effects reported. Levetiracetam appears to be a useful antimyoclonic agent in cases of progressive myoclonic epilepsy and should be considered for adjunctive therapy.

Effects of levetiracetam in lipid peroxidation level, nitrite-nitrate formation and antioxidant enzymatic activity in mice brain after pilocarpine-induced seizures

: Oxidative stress has been implicated in a large number of human degenerative diseases, including epilepsy. Levetiracetam (LEV) is a new antiepileptic agent with broad-spectrum effects on seizures and animal models of epilepsy. Recently, it was demonstrated that the mechanism of LEV differs from that of conventional antiepileptic drugs. Objectifying to investigate if LEV mechanism of action involves antioxidant properties, lipid peroxidation levels, nitrite-nitrate formation, catalase activity, and glutathione (GSH) content were measured in adult mice brain. The neurochemical analyses were carried out in hippocampus of animals pretreated with LEV (200 mg/kg, i.p.) 60 min before pilocarpine-induced seizures (400 mg/kg, s.c.). The administration of alone pilocarpine, 400 mg/kg, s.c. (P400) produced a significant increase of lipid peroxidation level in hippocampus. LEV pretreatment was able to counteract this increase, preserving the lipid peroxidation level in normal value. P400 administration also produced increase in the nitrite-nitrate formation and catalase activity in hippocampus, beyond a decrease in GSH levels. LEV administration before P400 prevented the P400-induced alteration in nitrite-nitrate levels and preserved normal values of catalase activity in hippocampus. Moreover, LEV administration prevented the P400-induced loss of GSH in this cerebral area. The present data suggest that the protective effects of LEV against pilocarpine-induced seizures can be mediated, at least in part, by reduction of lipid peroxidation and hippocampal oxidative stress.

Levetiracetam monotherapy for children and adolescents with benign rolandic seizures

To assess the efficacy, tolerability and safety of Levetiracetam (LEV) therapy, we identified 21 (15 male; 6 female) patients with a history of benign epilepsy with centrotemporal spikes (BECTS), with and without secondarily generalization in children and adolescents aged between 5.0 and 12.1 years. LEV was administered as a first drug (number of patients=9) or converted after previous treatment with other AEDs (number of patients=12). The patients were subdivided into two groups: "newly diagnosed" patients and "converted" patients. Patients were followed up for 12 months and all patients were able to continue on LEV treatment. At the end of follow-up (12 months), all patients were seizure free or showed a reduction of seizures >50%. LEV dosage ranged from 1000 to 2500mg/daily. Overall, 100% of patients completed the 12 months study, without any important side effect. Somnolence and irritability occurred in two (9.5%) patients. Our results support findings that LEV monotherapy is effective and well tolerated in children with BECTS. Prospective, large, long-term double-blind studies are needed to confirm these findings.

Mechanisms of action of antiepileptic drugs

The management of seizures in the patient with epilepsy relies heavily on antiepileptic drug (AED) therapy. Fortunately, for a large percentage of patients, AEDs provide excellent seizure control at doses that do not adversely affect normal function. At the molecular level, the majority of AEDs are thought to modify excitatory and inhibitory neurotransmission through effects on voltage-gated ion channels (e.g., sodium and calcium) and gamma-aminobutyric acid (GABA)(A) receptors, respectively. In addition to these effects, two of the "second-generation" AEDs have been found to limit glutamate-mediated excitatory neurotransmission (i.e., felbamate and topiramate). Not surprisingly, those AEDs with broad spectrum clinical activity are often found to exert an action at more than one molecular target. Emerging evidence suggests that receptor and voltage-gated subunits are modified by chronic seizures. Thus, attempts to understand the relationship between target and effect continue to provide important information about the neuropathology of the epileptic network and to facilitate the development of novel therapies for the treatment of refractory epilepsy.

Novel anticonvulsant drugs

Principles of complex mechanisms of action of anticonvulsants including latest reports concerning new antiepileptic drugs (AED) are considered. Different aspects of new anticonvulsant drugs (2nd generation) from preclinical and clinical testing, pharmacokinetics, and mono or combination therapy in children and adults are summarized. In the following condensed synopsis pharmacological and clinical characteristics of gabapentin (GBP), lamotrigine (LTG), levetiracetam (LEV), oxcarbazepine (OXC), pregabalin (PGB) and tiagabine (TGB) as well as topiramate (TPM) and zonisamide (ZNS) are discussed. In addition to the mechanisms of action, pharmacokinetics, interactions, indications and dosages as well as side effects are considered. Important data concerning the effect and tolerability of anticonvulsant drugs can be obtained from controlled studies. In comparison to drugs of the first generation (phenobarbital [PB], primidon [PRD], phenytoin [PHT], carbamazepine [CBZ] and valproic acid [VPA]) the potential for interactions and side effects due to enzyme induction or inhibition is reduced by most of the anticonvulsant drugs of the second generation. New anticonvulsant drugs increase the spectrum of treatment and represent further steps with regard to the optimization of an individual therapy of the epilepsies.

A double blind randomized placebo control trial of levetiracetam in tourette syndrome

The objective of this study was to investigate the effectiveness of levetiracetam for the treatment of tics in children with Tourette syndrome (TS). Levetiracetam, an atypical anticonvulsant, has been suggested in open-label protocols to be an effective tic-suppressing agent in individuals with TS. A double blind, randomized, placebo-controlled, cross-over trial was performed to investigate this medication in children with moderate to moderately-severe tics. Subjects received, in a randomized sequence, 4-weeks of levetiracetam (maximum dose 30 mg/kg/day) or placebo, with a 2-week intervening washout period between cycles. Primary outcome measures included two separate scales from the Yale Global Tic Severity Scale; the Total Tic score and the Total overall score. Measures were assessed at baseline, prior to randomization, on Day 28 (end of Phase 1), on Day 42 (baseline for second phase) and on Day 70 (end of Phase 2). Twenty-two subjects (21 boys and 1 girl) with TS, mean age 12.2 +/- 2.3 years, range 8 to 16 years, participated. A mild reduction in tics occurred during both the levetiracetam and placebo treatment phases. There was no significant difference between treatments and no evidence of sequence or cross-over effects. In conclusion, Levetiracetam is not more beneficial than placebo in suppressing tics in children with TS.

Levetiracetam is neuroprotective in murine models of closed head injury and subarachnoid hemorrhage

OBJECTIVES

Prophylactic treatment with antiepileptic drugs is common practice following subarachnoid hemorrhage (SAH) and traumatic brain injury. However, commonly used antiepileptic drugs have multiple drug interactions, require frequent monitoring of serum levels, and are associated with adverse effects that may prompt discontinuation. In the current study, we test the hypothesis that levetiracetam, an anticonvulsant with favorable interaction and adverse event profiles, is neuroprotective in clinically relevant models of SAH and closed head injury (CHI).

METHODS

A single intravenous dose of vehicle, low-dose (18 mg/kg), or high-dose (54 mg/kg) levetiracetam was administered intravenously followed CHI. Functional assessments were performed on a daily basis, and histological assessments performed at 24 hours. In a separate series of experiments, mice were randomized to receive intravenous administration of vehicle, low-dose, or high-dose levetiracetam every 12 hours for 3 days following SAH. Functional endpoints were assessed daily, followed by measurement of MCA luminal diameter on day 3.

RESULTS

A single dose of levetiracetam improved functional and histological outcomes after CHI. This effect appeared specific for levetiracetam and was not associated with fosphenytoin treatment. Treatment with levetiracetam also improved functional outcomes and reduced vasospasm following SAH.

CONCLUSION

Levetiracetam is neuroprotective in clinically relevant animal models of SAH and CHI. Levetiracetam may be a therapeutic alternative to phenytoin following acute brain injury in the clinical setting when seizure prophylaxis is indicated.

Efficacy and safety of levetiracetam in clinical practice: Results of the SKATE™ trial from Belgium and The Netherlands

OBJECTIVE

Aim of the study was to assess the efficacy and safety of levetiracetam as add-on treatment in patients with partial-onset epilepsy in clinical practice.

METHODS

In this observational, multi-centre study patients were treated with levetiracetam for 16 weeks. From a starting dose of 1000 mg/day, dose levels were adjusted at 2-weekly intervals in 1000-mg steps, to a maximum of 3000 mg/day, based on seizure control and tolerance. Analysis of efficacy was based on reduction in seizure frequency relative to baseline, 50% and 100% responder rates (for partial seizures and all seizure types combined) and percentage of patients using levetiracetam at the end of the study. Analysis of safety was based on occurrence of adverse events.

RESULTS

The present analysis concerns the results of patients recruited in Belgium and The Netherlands. Of the 251 patients included in the study, 86.9% completed 16 weeks of treatment. Reduction in frequency of partial-onset seizures was 62.2%, with 19.3% of the patients becoming seizure free and 56.6% having a reduction in seizure frequency of > or = 50%. These percentages were more or less the same when calculated for all seizure types combined. Tolerance of levetiracetam treatment was good, with most adverse events being only mild to moderate in severity, and only 10.0% of the adverse events leading to discontinuation from the study. Asthenia, somnolence, dizziness and headache were the most frequently reported adverse events.

CONCLUSION

Levetiracetam is effective and safe as add-on treatment for partial-onset seizures in clinical practice.

A new frontier in epilepsy: novel antiepileptogenic drugs

Epilepsy is a hetergenous syndrome characterized by recurrently and repeatedly occurring seizures. Although able to inhibit the epileptic seizures, the currently available antiepileptic drugs (AEDs) have no effects on epileptogenesis. Such AEDs should be classified as drugs against ictogenesis, which are transient events in ion and/or receptor-gated channels related with triggering to evoke seizures. Epileptogenesis involves long-term and histological/biochemical/physiological alterations formed in brain structures over a long period, ranging from months to years. This review focuses on the effects of AEDs on epileptogenesis and novel candidates of antiepileptogenic drugs using a genetically defined epilepsy model animal, the spontaneous epileptic rat (SER).

Efficacy and tolerability of levetiracetam in Parkinson disease patients with levodopa-induced dyskinesia

OBJECTIVES

This open-label study was performed to evaluate the efficacy and tolerability of levetiracetam for levodopa-induced dyskinesia and its effect on motor functioning and quality of life in Parkinson disease (PD) patients.

METHODS

PD patients with moderate to severe dyskinesia were enrolled in the study. PD medications were unchanged during the study, and levetiracetam was slowly titrated up to a maximum dosage of 3,000 mg/d over a 2-month period.

RESULTS

There were 9 patients with a mean age of 65 years and mean disease duration of 13 years. Forty-four percent of the subjects withdrew before the end of the study due to adverse events, primarily worsening of PD symptoms and sleepiness. Of the remaining 5 subjects, 1 subject continued levetiracetam after the study with mild improvement in dyskinesia and 4 discontinued levetiracetam due to worsening of PD symptoms and sleepiness.

CONCLUSIONS

Levetiracetam is not well tolerated in PD patients with levodopa-induced dyskinesia resulting in worsening of PD symptoms, intolerable somnolence, and worsening of dyskinesia in most patients.

In vivo characterisation of the small-conductance KCa (SK) channel activator 1-ethyl-2-benzimidazolinone (1-EBIO) as a potential anticonvulsant

Owing to their activation by increased intracellular Ca(2+) levels following burst firing, and the resultant hyperpolarisation and dampening of neuronal excitability, the small-conductance Ca(2+)-activated K(+) (SK(Ca)) channels have been proposed as a potential target for novel antiepileptic drugs. Indeed, the channel activator 1-ethyl-2-benzimidazolinone (1-EBIO) has been shown to reduce epileptiform activity in vitro. Accordingly, this study has investigated the therapeutic potential of 1-EBIO using a range of in vivo seizure models, and assessed the adverse effect liability with the rotarod and locomotor activity paradigms. To aid benchmarking of 1-EBIO's therapeutic and adverse effect potential, it was tested alongside two currently marketed antiepileptic drugs, phenytoin and levetiracetam. 1-EBIO was found to be effective at reducing seizure incidence in mice following maximal electroshock (ED(50) 36.0 mg/kg) as well as increasing the threshold to electrically- and pentylenetetrazole-induced seizures (TID(10)s 7.3 and 21.5 mg/kg, respectively). However, results from the mouse rotarod test revealed a strong adverse effect potential within the therapeutic dose range (ID(50) 35.6 mg/kg), implying a significantly inferior therapeutic index with respect to the comparator compounds. These results, therefore, support the in vitro data detailing 1-EBIO's reduction of epileptiform activity. However, the use of in vivo models has revealed a significant adverse effect potential within the therapeutic dose range. Nevertheless, given the multiplicity of SK(Ca) channel subunits and that 1-EBIO has been shown to enhance additional, non-SK(Ca) carried currents, these findings do not preclude the possibility that more selective enhancers of SK(Ca) function could prove to be effective as antiepileptic medications.

Levetiracetam Intravenous Infusion: A Randomized, Placebo-controlled Safety and Pharmacokinetic Study

PURPOSE

The primary objective of this placebo-controlled study was to evaluate the safety and tolerability of levetiracetam (LEV) administered intravenously (IV) at higher doses and/or at a faster infusion rate than proposed. The secondary objective was to assess LEV pharmacokinetics.

METHODS

Single ascending doses of LEV administered by IV infusion (2,000, 3,000, 4,000 mg over 15 min; 1,500, 2,000, 2,500 mg over 5 min) were evaluated in 48 healthy subjects in a randomized, single-blind, placebo-controlled study.

RESULTS

All randomized subjects completed the study. Adverse events reported after IV administration of LEV (<or=4,000 mg infused over 15 min and <or=2,500 mg infused over 5 min) were primarily related to the CNS (dizziness, 52.8%; somnolence, 33.3%; fatigue, 11.1%; headache, 8.3%) and were consistent with the established safety profile for the oral formulation. Safety profiles were similar for each dose level of LEV and for both IV infusion rates, with no clear relation noted between incidence of adverse events and IV dose level or infusion rate. The pharmacokinetics of LEV administered by IV infusion was comparable across all dose groups and infusion rates. Respective geometric means (coefficient of variation) for 4,000 mg administered over 15 min and 2,500 mg infused over 5 min were maximum plasma concentration, 145 (24.6%) and 94.3 (36.2%) mug/ml; area under the plasma concentration-time curve, 1,239 (19.2%) and 585 (9.6%) mug/h/ml; terminal half-life, 8.0 (14.5%) and 7.0 (12.7%) h.

CONCLUSIONS

LEV administered by IV infusion at dosages and/or infusion rates higher than those proposed was well tolerated in healthy subjects, and the pharmacokinetic profile was consistent with that for LEV administered orally.

Sodium- and magnesium-valproate in vivo modulate glutamatergic and GABAergic synapses in the medial prefrontal cortex

RATIONALE

Valproic acid (VPA) is a psychoactive drug currently used for the treatment of epilepsy. Recently it has been introduced in psychiatry for the treatment of bipolar disorders, aggression, impulsivity, and resistant schizophrenia, although the mechanism by which VPA acts on these psychiatric diseases remains still unknown.

OBJECTIVES

The aim of this study was to analyze the distinct effects of sodium-(Na-) and magnesium-valproate (Mg-VPA) in pyramidal neurons of the medial prefrontal cortex (mPFC) and their interactions with gamma-aminobutyric acid (GABA) and excitatory amino acid responses.

MATERIALS AND METHODS

In vivo electrophysiology and microiontophoresis techniques were used to attend these goals.

RESULTS

Both VPA salts decreased spontaneous neuronal firing activity in greater than 60% of recorded pyramidal neurons as well as potentiated GABA inhibitions. When injected at equal concentrations and currents, Mg-VPA blocked the excitatory responses induced by N-methyl-D-aspartate (NMDA) more frequently than Na-VPA. Both VPA salts equally blocked the excitatory responses of quisqualate and kainate.

CONCLUSIONS

These data suggest that VPA salts significantly modulate the activity of excitatory amino acid at mPFC pyramidal neurons and this mechanism should explain the therapeutic effects of valproate in psychiatric diseases involving NMDA, AMPA, and kainate receptors at the mPFC level.

Binding characteristics of levetiracetam to synaptic vesicle protein 2A (SV2A) in human brain and in CHO cells expressing the human recombinant protein

A specific binding site for the antiepileptic drug levetiracetam (2S-(oxo-1-pyrrolidinyl)butanamide, Keppra) in rat brain, referred to as the levetiracetam binding site, was discovered several years ago. More recently, this binding site has been identified as the synaptic vesicle protein 2A (SV2A), a protein present in synaptic vesicles [Lynch, B., Lambeng, N., Nocka, K., Kensel-Hammes, P., Bajjalieh, S.M., Matagne, A., Fuks, B., 2004. The synaptic vesicle protein SV2A is the binding site for the antiepileptic drug levetiracetam. Proc. Natl. Acad. Sci. USA, 101, 9861-9866.]. In this study, we characterized the binding properties of levetiracetam in post-mortem human brain and compared them to human SV2A expressed in Chinese hamster ovary (CHO) cells. The results showed that the binding properties of levetiracetam and [3H]ucb 30889, an analogue that was previously characterized as a suitable ligand for levetiracetam binding site/SV2A in rat brain [Gillard, M., Fuks, B., Michel, P., Vertongen, P., Massingham, R. Chatelain, P., 2003. Binding characteristics of [3H]ucb 30889 to levetiracetam binding sites in rat brain. Eur. J. Pharmacol. 478, 1-9.], are almost identical in human brain samples (cerebral cortex, hippocampus and cerebellum) and in CHO cell membranes expressing the human SV2A protein. Moreover, the results are also similar to those previously obtained in rat brain. [3H]ucb 30889 binding in human brain and to SV2A was saturable and reversible. At 4 degrees C, its binding kinetics were best fitted assuming a two-phase model in all tissues. The half-times of association for the fast component ranged between 1 to 2 min and represent 30% to 36% of the sites whereas the half-times for the slow component ranged from 20 to 29 min. In dissociation experiments, the half-times were from 2 to 4 min for the fast component (33% to 49% of the sites) and 20 to 41 min for the slow component. Saturation binding curves led to Kd values for [3H]ucb 30889 of 53+/-7, 55+/-9, 70+/-11 and 75+/-33 nM in human cerebral cortex, hippocampus, cerebellum and CHO cells expressing SV2A respectively. Bmax values around 3-4 pmol/mg protein were calculated in all brain regions. Some of the saturation curves displayed curvilinear Scatchard plots indicating the presence of high and low affinity binding sites. When this was the case, Kd values from 25 to 30 nM for the high affinity sites (24% to 34% of total sites) and from 200 to 275 nM for the low affinity sites were calculated. This was observed in all brain regions and in CHO cell membranes expressing the SV2A protein. It cannot be explained by putative binding of [3H]ucb 30889 to SV2B or C isoforms but may reflect different patterns of SV2A glycosylation or the formation of SV2A oligomers. Competition experiments were performed to determine the affinities for SV2A of a variety of compounds including levetiracetam, some of its analogues and other molecules known to interact with levetiracetam binding sites in rat brain such as bemegride, pentylenetetrazol and chlordiazepoxide. We found an excellent correlation between the affinities of these compounds measured in human brain, rat brain and CHO cells expressing human SV2A. In conclusion, we report for the first time that the binding characteristics of native levetiracetam binding sites/SV2A in human brain and rat brain share very similar properties with human recombinant SV2A expressed in CHO cells.

Catatonia induced by levetiracetam

Levetiracetam (Keppra) is a novel antiepileptic drug approved as adjunctive treatment for adults with partial onset seizures. Although the drug is generally well tolerated, behavioral side effects have been reported in variable frequency. Most behavioral problems are mild in nature (agitation, hostility, anxiety, emotional lability, apathy, depression) and quickly resolve with discontinuation of medication. However, serious psychiatric adverse events may also occur with rare cases of psychosis and suicidal behavior. We report here the case of a 43-year-old woman who developed symptoms compatible with catatonia after being exposed to levetiracetam for the treatment of epilepsy. To our knowledge, it is the first reported case of catatonia induced by levetiracetam. We review the difficulties that may be encountered in the differential diagnosis of medical catatonia.

Pharmacodynamic and Pharmacokinetic Characterization of Interactions between Levetiracetam and Numerous Antiepileptic Drugs in the Mouse Maximal Electroshock Seizure Model: An Isobolographic Analysis

PURPOSE

Approximately 30% of patients with epilepsy do not experience satisfactory seizure control with antiepileptic drug (AED) monotherapy and often require polytherapy. The potential usefulness of AED combinations, in terms of efficacy and adverse effects, is therefore of major importance. The present study sought to identify potentially useful AED combinations with levetiracetam (LEV) METHODS: With isobolographic analysis, the mouse maximal electroshock (MES)-induced seizure model was investigated with regard to the anticonvulsant effects of carbamazepine (CBZ), phenytoin, phenobarbital (PB), valproate, lamotrigine, topiramate (TPM), and oxcarbazepine (OXC), administered singly and in combination with LEV. Acute adverse effects were ascertained by use of the chimney test evaluating motor performance and the step-through passive-avoidance task assessing long-term memory. Brain AED concentrations were determined to ascertain any pharmacokinetic contribution to the observed antiseizure effect.

RESULTS

LEV in combination with TPM, at the fixed ratios of 1:2, 1:1, 2:1, and 4:1, was supraadditive (synergistic) in the MES test. Likewise, the combination of LEV with CBZ (at the fixed ratio of 16:1) and LEV with OXC (8:1 and 16:1) were supraadditive. In contrast, all other LEV/AED combinations displayed additivity. Furthermore, none of the investigated LEV/AED combinations altered motor performance and long-term memory. LEV brain concentrations were unaffected by concomitant AED administration, and LEV had no significant effect on brain concentrations of concomitant AEDs.

CONCLUSIONS

These preclinical data would suggest that LEV in combination with TPM is associated with beneficial anticonvulsant pharmacodynamic interactions. Similar, but less profound effects were seen with OXC and CBZ.

Antiepileptic drug discovery: lessons from the past and future challenges

Historically, most antiepileptic drugs (AEDs) have been discovered either by serendipity, or the screening of compounds using acute seizure models. However, an increasing understanding of the molecular mechanisms underlying epileptogenesis has led to more rational approaches to drug discovery, which have focused on either enhancing inhibitory gamma-amino butyric acid (GABA)-ergic, or antagonizing excitatory glutamatergic, neurotransmission. Unfortunately, AEDs generated using such strategies have poor efficacy and safety profiles, as they interfere with normal cell processes, while ignoring the complex underlying pathophysiology of epilepsy. Recently, however, the use of new epilepsy models has led to the discovery of levetiracetam, an AED with a truly unique mechanism of action, devoid of anticonvulsant activity in normal animals, but with potent seizure suppression in genetic and kindled chronic epilepsy models, and an unusually high safety margin. The recent identification of brivaracetam and seletracetam, which optimize this unique mechanism of action, may further improve the medical management of epilepsy. The experience with levetiracetam, brivaracetam and seletracetam reveals that new experimental epilepsy models can detect AEDs possessing a unique mechanism of action and thereby target the future challenge of providing clinicians novel additions to the current armamentarium of AEDs.

Levetiracetam selectively potentiates the acute neurotoxic effects of topiramate and carbamazepine in the rotarod test in mice

The effect of levetiracetam (LEV) on the acute neurotoxic profiles of various antiepileptic drugs (carbamazepine [CBZ], phenytoin [PHT], phenobarbital [PB], valproate [VPA], lamotrigine [LTG], topiramate [TPM], oxcarbazepine [OXC], and felbamate [FBM]) was evaluated in the rotarod test, allowing the determination of median toxic doses (TD50 values) with respect to impairment of motor coordination in mice. The TD50 of LEV administered singly was 1601 mg/kg. Whilst LEV at 150 mg/kg, being its TID50 (a dose increasing the electroconvulsive threshold by 50%), was without effect with regards to motor coordination impairment associated with PHT, PB, VPA, LTG, OXC, and FBM, it significantly enhanced that associated with CBZ and TPM co-administration. Thus LEV (150 mg/kg) significantly decreased the TD50 of CBZ from 53.6 to 37.3 mg/kg (P<0.01) and that of TPM from 423 to 246 mg/kg (P<0.01). In addition LEV (75 mg/kg) significantly decreased the TD50 of TPM from 423 to 278 (P<0.01). That concurrent measurement of total brain LEV, CBZ, and TPM concentrations showed that concentrations were not significantly different when AEDs were administered singly compared to when they were administered in combination would suggest that there is no pharmacokinetic interaction between these AEDs. Thus, the observed potentialization of the acute neurotoxic effects of CBZ and TPM by LEV is the consequence of a pharmacodynamic interaction. These data support both experimental and clinical published data advocating that LEV may interact with some AEDs by pharmacodynamic mechanisms.

Levetiracetam in the Treatment of Idiopathic Generalized Epilepsies

Since its introduction into clinical practice in 1999, levetiracetam, the S enantiomer of piracetam, has rapidly found a secure place, initially in the therapy of partial onset seizures and subsequently in the treatment of idiopathic generalized epilepsies (IGE). It has many of the properties of an "ideal" antiepileptic drug, including rapid absorption, linear pharmokinetics, and sparse drug interactions. Tolerabiliy is generally excellent in both adults and children, although tiredness is a common dose-limiting adverse effect. Occasionally the drug can precipitate behavioral abnormalities, especially in patients with learning disability. There is a wide safety margin in overdose. In common with most antiepileptic drugs its mode of action remains uncertain. Levetiracetam binds to a specific site in the brain, influences intracellular calcium currents and reverses negative allosteric modulators of GABA- and glycine-gated currents in vitro. Its effectiveness has been demonstrated in animal models of epilepsy and in clinical trials of partial onset and IGE. Treatment of IGEs may be straightforward, with many patients demonstrating an excellent and robust response to valproate monotherapy. However, there remains a significant minority of patients for whom valproate is unsuitable, including those who experience unacceptable adverse effects (e.g., weight gain or hair loss) and women of childbearing age in whom the teratogenic potential of valproate is unacceptable. Therapeutic response to lamotrigine in this group is often disappointing, and many clinicians now are turning to the choice of levetiracetam. Efficacy in generalized tonic-clonic seizures and myoclonus is usually apparent and some patients experience improvement in typical absences. Experience of combinations of levetiracetam with other antiepileptic drugs is limited in IGE and the responses are largely anecdotal. In our hands, patients with refractory IGEs may respond to combinations of levetiracetam with valproate, lamotrigine, and phenobarbital, and adverse effects when they occur are usually limited to tiredness. Levetiracetam does not interact with the oral contraceptive pill, simplifying treatment in women of childbearing age. Although animal data look encouraging, questions over levetiracetam's teratogenic potential and overall safety in pregnancy will remain for many years to come.

Long-lasting antiepileptic effects of levetiracetam against epileptic seizures in the spontaneously epileptic rat (SER): differentiation of levetiracetam from conventional antiepileptic drugs

PURPOSE

Some evidence suggests that levetiracetam (LEV) possesses antiepileptogenic characteristics. The purpose of this study was to investigate the time course of seizure protection by LEV compared with that of phenytoin (PHT), phenobarbital (PB), valproate (VPA), and carbamazepine (CBZ) in the spontaneously epileptic rat (SER). The SER is a double mutant (tm/tm, zi/zi) showing both tonic convulsions and absence-like seizures.

METHODS

The effect of single (40, 80, and 160 mg/kg, i.p.) and 5-day (80 mg/kg/day, i.p.) administration of LEV on tonic convulsions and absence-like seizures in SERs were studied. Tonic convulsions induced by blowing air onto the animal's head at 5-min intervals for 30 min and spontaneous absence-like seizures characterized by 5- to 7-Hz spike-wave-like complexes in the cortical and hippocampal EEG were recorded for 30 min. In the single-administration study, observations for seizure activity were performed once before and 3 times (45, 75, and 135 min) after drug administration. In the 5-day administration study, seizure observation was performed 4 times for 30 min (once before and 3 times after drug administration) during the 5-day drug-administration period, and continued once a day until 8 days after the final administration. The antiepileptic effects of 5-day administration of conventional AEDs (PHT, PB, VPA, and CBZ) were examined by using similar methods.

RESULTS

Tonic convulsions and absence-like seizures were inhibited by a single administration of LEV at 80 and 160 mg/kg, i.p., but not significantly at 40 mg/kg, i.p. When LEV was repeatedly administered at 80 mg/kg/day, i.p., for 5 days to SERs, the inhibitory effects on seizures increased with administration time. The number of tonic convulsions and absence-like seizures were significantly reduced to 39.1% and 38.4% compared with previous values, respectively, after 5-day LEV administration. Furthermore, significant inhibition of tonic convulsions was detected <or=3 days after the final administration, and significant inhibition of absence-like seizures was still observed 8 days after the final injection of LEV. This demonstrates long-lasting seizure protection by LEV after cessation of treatment. PHT, PB, VPA, and CBZ inhibited tonic convulsions more potently compared with LEV in SERs. The maximal antiseizure effects of these drugs were reached after the initial administration, with almost the same antiseizure effects observed through day 5, despite continued drug administration. Moreover, a long-lasting treatment effect was not observed with any of these drugs except for PHT and CBZ, both of which showed moderately prolonged antiseizure effects.

CONCLUSIONS

These results show that LEV is effective in the treatment of both convulsive and absence-like seizures in SERs after single- and multiple-dose administration. Interestingly, in the 5-day administration study, it was found that the antiepileptic effects for tonic convulsions and absence-like seizures were observed both during the drug-administration period and <or=8 days after the final administration of LEV. This long-lasting effect suggests that LEV may possess an antiepileptogenic effect that it does not share with PHT, PB, VPA, and CBZ.

Evaluation of levetiracetam effects on pilocarpine-induced seizures: Cholinergic muscarinic system involvement

Levetiracetam (LEV) is a new antiepileptic drug effective as adjunctive therapy for partial seizures. It displays a unique pharmacological profile against experimental models of seizures, including pilocarpine-induced seizures in rodents. Aiming to clarify if anticonvulsant activity of LEV occurs due to cholinergic alterations, adult male mice received LEV injections before cholinergic agonists' administration. Pretreatment with LEV (30-200 mg/kg, i.p.) increased the latencies of seizures, but decreased status epilepticus and death on the seizure model induced by pilocarpine, 400 mg/kg, s.c. (P400). LEV (LEV200, 200 mg/kg, i.p.) pretreatment also reduced the intensity of tremors induced by oxotremorine (0.5 mg/kg, i.p). [3H]-N-methylscopolamine-binding assays in mice hippocampus showed that LEV200 pretreatment reverts the downregulation on muscarinic acetylcholine receptors (mAChR), induced by P400 administration, bringing back these density values to control ones (0.9% NaCl, i.p.). However, subtype-specific-binding assays revealed that P400- and LEV-alone treatments result in M1 and M2 subtypes decrease, respectively. The agonist-like behavior of LEV on the inhibitory M2 mAChR subtype, observed in this work, could contribute to explain the reduction on oxotremorine-induced tremors and the delay on pilocarpine-induced seizures, by an increase in the attenuation of neuronal activity mediated by the M1 receptors.

Effects of anticonvulsants on soman-induced epileptiform activity in the guinea-pig in vitro hippocampus

Seizures arising from acetylcholinesterase inhibition are a feature of organophosphate anticholinesterase intoxication. Although benzodiazepines are effective against these seizures, alternative anticonvulsant drugs may possess greater efficacy and fewer side-effects. We have investigated in the guinea-pig hippocampal slice preparation the ability of a series of anticonvulsants to suppress epileptiform bursting induced by the irreversible organophosphate anticholinesterase, soman (100 nM). Carbamazepine (300 microM), phenytoin (100 microM), topiramate (100-300 microM) and retigabine (1-30 microM) reduced the frequency of bursting but only carbamazepine and phenytoin induced a concurrent reduction in burst duration. Felbamate (100-500 microM) and clomethiazole (100-300 microM) had no effect on burst frequency but decreased burst duration. Clozapine (3-30 microM) reduced the frequency but did not influence burst duration. Levetiracetam (100-300 microM) and gabapentin (100-300 microM) were without effect. These data suggest that several compounds, in particular clomethiazole, clozapine, felbamate, topiramate and retigabine, merit further evaluation as possible treatments for organophosphate poisoning.

Separation of Antiepileptogenic and Antiseizure Effects of Levetiracetam in the Spontaneously Epileptic Rat (SER)

PURPOSE

The long-lasting antiseizure effects of levetiracetam (LEV) have been observed in the spontaneously epileptic rat (SER) that expresses both tonic and absence-like seizures. Furthermore, the antiepileptogenic effects of LEV in addition to antiseizure effects have been reported in the amygdala-kindling model in rats. This suggests that the long-lasting seizure protection of LEV may be at least partly due to its antiepileptogenic effects. Therefore this study aimed to differentiate the antiseizure and potential antiepileptogenic effects of LEV by administering LEV continuously to SERs before the appearance of any seizure expression.

METHODS

LEV was administered to the SERs at 80 mg/kg/day (i.p.) from postnatal weeks 5 to 8. The period of observation for tonic convulsions was from postnatal week 5 to 13. Absence-like seizures were recorded by using conventional EEG in weeks 12 and 13.

RESULTS

After age 7-8 weeks, SERs exhibit spontaneous tonic convulsions. Development of tonic convulsions was significantly inhibited in the LEV group, compared with the control group, by the middle of week 9. A significant reduction of tonic convulsions also was observed in the LEV group until week 13 (5 weeks after termination of the administration). In week 12, the absence-like seizures were significantly lower in the LEV group, compared with the control group.

CONCLUSIONS

This study demonstrates a significant inhibition of seizures after prolonged treatment with LEV before the developmental expression of seizure activity in SERs. This effect is suggested to be due to an antiepileptogenic effect and not an antiseizure effect of LEV, because the half-life of the drug in plasma is short (2-3 h in rats) after single and long-term administration. Furthermore, the inhibition of seizure expression in SERs was still apparent 5 weeks after termination of LEV treatment. These results further suggest that LEV possesses not only antiseizure effects but also antiepileptogenic properties.

The relationship between the pharmacology of antiepileptic drugs and human gene variation: an overview

Individual differences in clinical responsiveness to antiepileptic drugs are due to a complex interaction between environmental factors and genetic variation. Considerable interest has arisen in exploiting advances in molecular genetics to improve drug therapy for epilepsy and many other diseases; however, practical application of pharmacogenetics has been difficult to realize. Attempts to define gene variants that are associated with therapeutic (or adverse) effects of antiepileptic drugs rely currently on the prior identification of candidate genes and the subsequent evaluation of the distribution of allelic variants between individuals who have a "good" versus a "poor" clinical response. Many factors can adversely affect interpretation of such data, and careful consideration must be given to the design of genetic association studies involving candidate genes. Candidate genes may be identified in a number of ways; however, for studies of drugs, application of knowledge derived from basic pharmacology can suggest focused and testable hypotheses that are based on the fundamental principles of drug action. Thus, studies of genetic variation as they relate to proteins involved in antiepileptic drug kinetics and dynamics will identify key polymorphisms in endogenous molecules that determine degrees of drug efficacy and toxicity. Delineation of these effects in the coming years will promote enhanced success in the treatment of epilepsy.

Use of levetiracetam to treat tics in children and adolescents with Tourette syndrome

Some drugs currently used to treat tics in pediatric patients have drawbacks, including the risk of side effects. New therapeutic options with better safety profiles are needed. Levetiracetam is an antiepileptic drug with atypical mechanisms of action that might be beneficial for this indication. We evaluated the effects of levetiracetam on motor and vocal tics, behavior, and school performance in children and adolescents with tics and Tourette syndrome (TS). Sixty patients, < or =18 years of age, with tics and TS were enrolled in this prospective, open-label study. The initial starting dose of levetiracetam was 250 mg/day. The dosage was titrated over 3 weeks to 1,000 to 2,000 mg/day. Clinical outcomes were assessed with the Clinical Global Impression Scale, Yale Global Tic Severity Scale, and Revised Conners' Parent Rating Scale. Behavior and school performance were also recorded. All 60 patients showed improvements based on all of the scales used, and 43 patients improved with regard to behavior and school performance. Levetiracetam was generally well tolerated. Three patients discontinued treatment because of exaggeration of preexisting behavioral problems. Levetiracetam may be useful in treating tics in children and adolescents. Given its established safety profile, levetiracetam is a candidate for evaluation in a well-controlled trial.