Effects of levetiracetam on nocturnal sleep and daytime vigilance in healthy volunteers

PURPOSE: Individuals with epilepsy commonly report daytime sleepiness, attributed to sleep disruption (frequent arousals, awakenings, and stage shifts) induced by ictal and interictal activity or antiepileptic drugs (AEDs) or both. To study the effect of levetiracetam (LEV) on sleep, at full doses but without the interference of epilepsy, we investigated the sleep architecture and daytime vigilance in healthy adults after 3 weeks of treatment. METHODS: The study was of a double-blind crossover design with random allocation of multiple doses of two different treatments (randomly first LEV 相似文献   

Selective blockade of N-type calcium channels by levetiracetam

PURPOSE: We investigated the effect of the new antiepileptic drug (AED) levetiracetam (LEV) on different types of high-voltage-activated (HVA) Ca2+ channels in freshly isolated CA1 hippocampal neurons of rats. METHODS: Patch-clamp recordings of HVA Ca2+ channel activity were obtained from isolated hippocampal CA1 neurons. LEV was applied by gravity flow from a pipette placed near the cell, and solution changes were made by electromicrovalves. Ca2+ channel blockers were used for separation of the channel subtypes. RESULTS: The currents were measured in controls and after application of 1-200 microM LEV. LEV irreversibly inhibited the HVA calcium current by approximately 18% on the average. With a prepulse stimulation protocol, which can eliminate direct inhibition of Ca2+ channels by G proteins, we found that G proteins were not involved in the pathways underlying the LEV inhibitory effect. This suggested that the inhibitory effect arises from a direct action of LEV on the channel molecule. The blocking mechanism of LEV was not related to changes in steady-state activation or inactivation of Ca2+ channels. LEV also did not influence the rundown of the HVA Ca2+ current during experimental protocols lasting approximately 10 min. Finally, LEV at the highest concentration used (200 microM) did not influence the activity of L-, P- or Q-type Ca2+ channels in CA1 neurons, while selectively influencing the activity of N-type calcium channels. The maximal effect on these channels separated from other channel types was approximately 37%. CONCLUSIONS: Our results provide evidence that LEV selectively inhibits N-type Ca2+ channels of CA1 pyramidal hippocampal neurons. These data suggest the existence of a subtype of N-type channels sensitive to LEV, which might be involved in the molecular basis of its antiepileptic action.     

Anticonvulsive and antiepileptogenic effects of levetiracetam in the audiogenic kindling model

Purpose: To study anticonvulsive and antiepileptogenic effects of singe levetiracetam (LEV) administration in the model of audiogenic kindling.
Methods: Rats of Krushinsky-Molodkina (KM) strain genetically susceptible to severe audiogenic seizures received one intraperitoneal injection of saline, low (6 mg/kg) or high (50 mg/kg) dose of LEV before or after audiogenic kindling. One hour postinjection, an audiogenic seizure was induced to assess anticonvulsive effect of LEV in nonkindled and kindled rats. To examine antiepileptogenic activity of LEV, nonkindled rats injected with the drug or saline were kindled with repeated sound stimulations. Audiogenic kindling development manifested in an appearance and progressive prolongation of an additional seizure phase, post-tonic–clonus. The latency and duration of audiogenic seizures and the duration of every seizure phase (running, tonic, post-tonic–clonic) were measured.
Results: One hour posttreatment, LEV dose-dependently lengthened the latency and reduced the duration of audiogenic seizures in both nonkindled and kindled rats. The seizure shortening resulted from selective suppression of tonic and kindled post-tonic–clonic phases. The dose of 50 mg/kg completely blocked tonic and clonic convulsions 1 h postinjection. The anticonvulsive effect of LEV was more pronounced in kindled than in nonkindled rats. Single LEV injection in the dose of 50 mg/kg prior audiogenic kindling significantly suppressed subsequent kindling progression indicating profound antiepileptogenic potency of the drug.
Conclusions: The present study shows that LEV exerts both short-lasting anticonvulsive effect on audiogenic seizures and very long-lasting antiepileptogenic effect on audiogenic kindling. Remarkably, a single injection of LEV is enough to significantly suppress kindling progression in KM rats.     

Proepileptic phenotype of SV2A-deficient mice is associated with reduced anticonvulsant efficacy of levetiracetam

Purpose:   Synaptic vesicle protein 2A (SV2A) constitutes a distinct binding site for an antiepileptic drug levetiracetam (Keppra). In the present study we characterized SV2A (+/−) heterozygous mice in several seizure models and tested if the anticonvulsant efficacy of levetiracetam is reduced in these mice.
Methods:   Seizure thresholds of male SV2A (+/−) mice and their wild-type littermates were assessed in pilocarpine (i.p.), kainic acid (s.c.), pentylenetetrazol (i.v.), 6-Hz and maximal electroshock models. Kindling development was compared in amygdala and corneal kindling models. Ex vivo binding of levetiracetam to SV2A was also performed.
Results:   Long-term electroencephalography (EEG) monitoring and behavioral observations of SV2A (+/−) mice did not reveal any spontaneous seizure activity. However, a reduced seizure threshold of SV2A (+/−) mice was observed in pilocarpine, kainic acid, pentylenetetrazol, and 6-Hz models, but not in maximal electroshock seizure model. Accelerated epileptogenesis development was also demonstrated in amygdala and corneal kindling models. Anticonvulsant efficacy of levetiracetam, defined as its ability to increase seizure threshold for 6 Hz electrical stimulation, was significantly reduced (approx. 50%) in the SV2A (+/−) mice, consistently with reduced binding to SV2A in these mice. In contrast, valproate produced the same anticonvulsant effect in both SV2A (+/+) and SV2A (+/−) mice.
Discussion: The present results evidence that SV2A is involved in mediation of the in vivo anticonvulsant activity of levetiracetam, in accordance with its previously proposed mechanism of action. Furthermore, the present data also indicate that even partial SV2A deficiency may lead to increased seizure vulnerability and accelerated epileptogenesis.     

Benefit of combination therapy in epilepsy: a review of the preclinical evidence with levetiracetam

Levetiracetam (Keppra) is an antiepileptic drug (AED) characterized by a novel mechanism of action, unique profile of activity in seizure models, and broad-spectrum clinical efficacy. The present report critically reviews several preclinical studies focused on combination therapy with levetiracetam and other anticonvulsants in various seizure and epilepsy models. Administration of levetiracetam together with many different clinically used AEDs or other anticonvulsants generally enhances their protective activity and, among existing AEDs, this was particularly prevalent with valproate. The protective activity of other AEDs was also enhanced by levetiracetam, which seems to be a universal finding that is independent of seizure model or drug combination studied. However, particularly strong enhancement was observed when levetiracetam was combined with agents either enhancing GABAergic or reducing glutamatergic neurotransmission. Importantly, these combinations were not associated with exacerbation of side effects or pharmacokinetic interactions. Based on the available preclinical data, it appears that combination treatment with levetiracetam and other anticonvulsants provides additional therapeutic benefit that may be attributed to its novel and distinct mechanism of action. Moreover, combinations of levetiracetam with clinically used AEDs that enhance GABAergic inhibition may be considered for rational polytherapy, which is often necessary in drug-resistant patients.     

The risk of paradoxical levetiracetam effect is increased in mentally retarded patients

Purpose: Incidental paradoxical antiepileptic effect of levetiracetam has been described. The aim of the present study was to identify the epilepsy patients at risk.
Methods: We performed a retrospective analysis in 207 patients treated with levetiracetam. This entailed evaluation of patient notes and patient interviews. A paradoxical effect was defined as an increased seizure frequency or the experience of more severe seizures including generalized tonic–clonic seizures (GTCS) within 1 month after starting levetiracetam (LEV).
Results: Thirty patients (14%) experienced a paradoxical effect. Eight of them (4%) developed de novo GTCS. We could not demonstrate any association between the paradoxical effect of levetiracetam and type of epilepsy or the antiepileptic comedication used. However we found that the paradoxical effect developed preferentially (p < 0.001) in mentally retarded patients.
Conclusion: Because there is an increased risk of worsening epilepsy when starting levetiracetam treatment of mentally retarded epileptic patients, there is a need for caution and close observation during the first weeks of therapy.     

Differential effects of levetiracetam, carbamazepine, and lamotrigine on reproductive endocrine function in adults

Animal studies have shown endocrine changes after levetiracetam treatment. The present study investigated reproductive and sexual function in patients with epilepsy (aged 18–45) treated with levetiracetam (LEV: 30 men/26 women), carbamazepine (CBZ: 63 men/30 women), or lamotrigine (LTG: 37 men/40 women) monotherapy and in healthy controls (36 men/44 women). In women, no endocrine changes were observed during LEV treatment, whereas steroid hormone-binding globulin levels were greater and progesterone levels lower in women using CBZ. Dehydroepiandrosterone sulfate levels were higher and androstenedione levels lower in LTG-treated women. Arizona Sexual Experience Scale scores, which were significantly lower in females using LTG or LEV, suggesting they have better sexual function than CBZ users and controls. In men, no drug-specific hormonal pattern was observed after LEV treatment. Male patients in all treatment groups had lower androstenedione and free testosterone. Those using CBZ had lower free androgen indices and dehydroepiandrosterone sulfate levels, and higher steroid hormone-binding globulin, follicle-stimulating hormone, and luteinizing hormone levels. Arizona Sexual Experience Scale scores for men were similar in all groups. In conclusion, LEV treatment apparently has no drug-specific sexual or endocrine side effects in men or women in this age group.     

Intracellular calcium increase in epileptiform activity: modulation by levetiracetam and lamotrigine

PURPOSE: Alterations in neuronal calcium (Ca2+) homeostasis are believed to play an essential role in the generation and propagation of epileptiform events. Levetiracetam (LEV) and lamotrigine (LTG), novel antiepileptic drugs (AEDs), were tested on epileptiform events and the corresponding elevations in intracellular Ca2+ concentration ([Ca2+]i) recorded from rat neocortical slices. METHODS: Electrophysiological recordings were performed from single pyramidal neurons from a slice preparation. Spontaneous epileptiform events consisting of long-lasting, repetitive paroxysmal depolarization shifts (PDSs) and interictal spike activity were induced by reducing the magnesium concentration from the solution and by adding bicuculline and 4-aminopyridine. Simultaneously, microfluorimetric measurements of [Ca2+]i were performed. Optical imaging with Ca2+ indicators revealed a close correlation between Ca2+ transients and epileptiform events. RESULTS: Both LEV and LTG were able to reduce both amplitude and duration of PDSs, as well as the concomitant elevation in [Ca2+]i, in a dose-dependent fashion. Whole-cell patch-clamp recordings from isolated neocortical neurons revealed that LEV significantly reduced N-, and partially P/Q-type high-voltage-activated (HVA) Ca2+ currents, whereas sodium currents were unaffected. Interestingly, the inhibitory effects of LEV were mimicked and occluded by LTG or by a combination of omega-conotoxin GVIA and omega-agatoxin IVA, selective blockers of N- and P/Q-type HVA channels, respectively, suggesting a common site of action for these AEDs. CONCLUSIONS: These results demonstrate that large, transient elevations in neuronal [Ca2+]i correlate to epileptiform discharges. The antagonistic effects of LEV and LTG on [Ca2+]i overload might represent the basis for their anticonvulsant efficacy and could preserve neuronal viability.     

Maternal exposure to the antiepileptic drug vigabatrin affects postnatal development in the rat

Abstract The objective was to investigate, in the rat, the effects of maternal exposure to vigabatrin (VGB) on the postnatal motor-cognitive behaviour of the offspring. We used an experimental evaluator-blind, placebo-controlled study in the rat. Ten pregnant rats were divided into five groups and treated with different doses of VGB (250, 500, 750, 1000 mg/kg/day) or placebo from gestation day (GD) 6 to GD10. After delivery, 56 pups (40 pups prenatally exposed to VGB and 16 pups exposed to placebo) were evaluated for motor-cognitive behaviour throughout postpartum day 40. At the end of testing sessions the animals were sacrificed and brain tissues processed for biochemical analysis of GABA levels. Body weight of pups and young rats whose mothers were treated with a dose of 750 mg/kg/day were significantly lower both at birth and during the whole postnatal life with respect to the control groups. Young rats of this group exhibited impaired performance in both the open-field and water maze tasks. Brain GABA contents were dramatically increased in this group of rats. No other significant nutritional, biochemical or behavioural changes were observed after treatments with doses of VGB lower than 750 mg/kg/day. The exposure to a dose of 1000 mg/kg caused abortion. Maternal exposure to VGB at relatively high doses (750 mg/kg/day) is likely to cause some important changes of the nutritional status during the pre- and postnatal life. Thus, the biochemical and cognitive abnormalities observed in this study could be related to some disturbances of brain development induced by malnutrition and/or to a disturbance of neuronal programming of the gabaergic system.     

Efficacy and tolerability of levetiracetam 3000 mg/d in patients with refractory partial seizures: a multicenter, double-blind, responder-selected study evaluating monotherapy. European Levetiracetam Study Group

PURPOSE: To evaluate the efficacy and tolerability of levetiracetam (LEV) monotherapy in selected patients with refractory partial seizures. METHODS: In this multicenter, double-blind, placebo-controlled, parallel-group, responder-selected study, patients were randomized (2:1 ratio) to receive oral LEV 1500 mg twice daily or placebo during a 12-week add-on phase. Treatment responders (patients with a reduction in partial seizure frequency of 50% or more compared with baseline) entered a monotherapy phase that included a maximum 12-week down-titration period and 12 weeks of monotherapy at 1500 mg twice daily. In both phases, responder rate, seizure frequency, and adverse events were analyzed. RESULTS: A total of 286 patients (placebo, n = 105; LEV, n = 181) entered the add-on phase, and 86 patients (placebo, n = 17; LEV, n = 69) were eligible for the monotherapy phase. Thirty-six of 181 patients (19.9%) who received LEV completed the entire study compared with only 10 of 105 patients (9.5%) in the placebo group (p = 0.029). The odds of completing the study on LEV were 2.36 times (95% confidence interval, 1.08, 5.57) higher than on placebo. The responder rate during the add-on phase was significantly higher in the LEV group compared with the placebo group (42.1% vs. 16.7%, respectively; p < 0.001). In the LEV monotherapy group, the median percent reduction in partial seizure frequency compared with baseline was 73.8% (p = 0.037), with a responder rate of 59.2%. Nine patients (18.4%) remained seizure-free on LEV monotherapy. CONCLUSIONS: Conversion to LEV monotherapy (1500 mg twice daily) is effective and well tolerated in patients with refractory partial seizures who responded to 3000 mg/d LEV as add-on therapy.     

Use of levetiracetam in a population of patients aged 65 years and older: a subset analysis of the KEEPER trial

Levetiracetam (Keppra) was evaluated in a subset of patients aged >/=65 years (n=78) enrolled in a large (n=1030) open-label, phase IV trial (the KEEPER trial). A 4-week dose adjustment was followed by a 12-week evaluation period. An overall median reduction in partial seizures of 80.1% (n=65) was observed. Overall, 76.9% of patients were >/=50% responders, 56.9% were >/=75% responders, and 40.0% were 100% responders. Levetiracetam was well tolerated, with 42.3% of patients reporting one or more adverse events. A total of 15 patients (19.2%) experienced an adverse event that led to discontinuation. Somnolence (n=13,16.7%) and dizziness (n=7,9.0%) were the most commonly reported adverse events. Despite the limitations of the open-label study design, these data provide information regarding the use of levetiracetam as add-on therapy for the treatment of partial-onset seizures in patients >/=65 years of age, including those requiring concomitant medications.     

Pharmacokinetics of levetiracetam and its enantiomer (R)-alpha-ethyl-2-oxo-pyrrolidine acetamide in dogs

PURPOSE: The new antiepileptic drug, levetiracetam (LEV, ucb LO59), is a chiral molecule with one asymmetric carbon atom whose anticonvulsant activity is highly enantioselective. The purpose of this study was to evaluate and compare the pharmacokinetics (PK) of LEV [(S)-alpha-ethyl-2-oxo-pyrrolidine acetamide] and its enantiomer (R)-alpha-ethyl-2-oxo-pyrrolidine acetamide (REV) after i.v. administration to dogs. This is the first time that the pharmacokinetics of both enantiomers has been evaluated. METHODS: Optically pure LEV and REV were synthesized, and 20 mg/kg of individual enantiomers was administered intravenously to six dogs. Plasma and urine samples were collected until 24 h, and the concentrations of LEV and REV were determined by an enantioselective assay. The levels of 2-pyrrolidone-N-butyric acid, an acid metabolite of LEV and REV, were determined by high-performance liquid chromatography (HPLC). The data were used for PK analysis of LEV and REV. RESULTS: LEV and REV had similar mean +/- SD values for clearance; 1.5 +/- 0.3 ml/min/kg and volume of distribution; 0.5 +/- 0.1 L/kg. The half-life (t1/2) and mean residence time (MRT) of REV (t1/2, 4.3 +/- 0.8 h, and MRT, 6.0 +/- 1.1 h) were, however, significantly longer than those of LEV (t1/2, 3.6 +/- 0.8 h, and MRT, 5.0 +/- 1.2 h). The renal clearance and fraction excreted unchanged for LEV and REV were significantly different. CONCLUSIONS: In addition to the enantioselective pharmacodynamics, alpha-ethyl-2-oxo-pyrrolidine acetamide has enantioselective PK. The enantioselectivity was observed in renal clearance. Because REV has more favorable PK in dogs than LEV, the higher antiepileptic potency of LEV is more likely due to intrinsic pharmacodynamic activity rather than to enantioselective PK.     

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.     

Efficacy and safety of add-on levetiracetam in refractory childhood epilepsy

Purpose: The purpose of the present study was to evaluate the efficacy and safety of levetiracetam (LEV) in refractory epileptic children. Methods: The study group included 61 outpatients (7 generalized, 48 localization-related, 3 undetermined, 3 unclassified) aged between 16 months and 18 years. LEV was given twice daily at a total dose of 10 mg/kg/day. The final mean dose was 50.7 mg/kg/day. The mean number of prior anti-epileptic drugs was 5.2. The entire treatment period was more than 6 months after LEV administration. Results: Fifteen children (24.6%) became seizure-free for 6 months after starting LEV, and 18 (29.5%) had a seizure reduction of more than 50% for the entire 6 months. The response rate was 33/61 (54.1%). Responders included 2/3 of patients (66.7%) with epilepsy with continuous spikes and waves during slow sleep and 13/19 (68.4%) with frontal lobe epilepsy. The effective dosage of LEV in the responders demonstrated a wide range (mean, 46.1 mg/kg/day; range, 19.4–59.1 mg/kg/day), and showed bimodal distribution. Adverse events occurred in only two patients who did not require LEV discontinuation. Conclusion: LEV represents an important addition to the treatments available for refractory epileptic children.     

Effect of 21-day exposure of phenobarbital, carbamazepine and phenytoin on P-glycoprotein expression and activity in the rat brain

Overexpression of P-glycoprotein may be involved in multidrug resistance of epilepsy, but the mechanisms are not clear. The aim of the studies was to investigate whether chronic exposure of antiepileptic drugs (AEDs) increased P-glycoprotein (P-gp) function and expression in brain of rats. Three drugs phenobarbital (PB), phenytion (PHT) and carbamazepine (CBZ) were orally given to rats twice a day for successive 21 days, P-gp activity in brain was assessed using the brain-to-plasma concentration ratios of rhodamine 123 (Rho 123) at 1 h following intravenous administration of 0.2 mg/kg. Immunohistochemistry was also used to analyze P-gp localization in rat brain regions. P-gp levels in the brain regions were further evaluated using western blot. The results showed 21-day exposure of AEDs resulted in significant decrease of tissue-to-plasma concentration ratios of Rho 123 in cerebral cortex and hippocampus without affecting their concentrations in plasma. Immunohistochemistry result showed that up-regulation of the P-gp mainly occurred in capillary endothelial vessels. Western blot result suggested that the protein level of P-gp in cortex and hippocampus of rats exposed to drugs was significantly higher than that of control rats. The P-gp levels were associated with P-gp activity in corresponding rats. All the results verified the hypothesis that chronic exposure of AEDs may increase P-gp function and level in brain of rats.