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

Limited efficacy of levetiracetam on myoclonus of different etiologies

Levetiracetam is a relatively new antiepileptic drug, which has been reported to have promising antimyoclonic properties, especially in posthypoxic myoclonus, progressive myoclonic epilepsy (PME) and spinal myoclonus. Eight patients with intractable myoclonus of various etiologies were given levetiracetam as add-on therapy in an open-label trial. Physician and patient self-assessments were recorded over 1 year. Symptomatic improvement occurred only with posthypoxic myoclonus, which was rapid, dramatic and sustained. All other forms of myoclonus either did not improve or worsened (1 essential myoclonus, 2 myoclonus-dystonia, 2 PME, 2 mitochondrial disease). Levetiracetam has promising but selective antimyoclonic potential, which should be the subject of further study.

Interaction of topiramate with glycine receptor channels

Glycine receptor channels are pentameric ligand-gated ion channels that respond to the application of inhibitory neurotransmitters by opening of a chloride-selective central pore. Topiramate (TPM) is a broad-spectrum antiepileptic drug used as add-on or monotherapy for focal seizures. In the present study the interaction of TPM with glycine receptor channels was studied on outside-out patches from HEK293 cells expressing alpha1beta glycine receptor channels. The patch clamp techniques combined with ultra fast solution exchange enabled us to investigate the kinetics of receptor channels in presence of TPM. Our study showed no agonistic or potentiating effect for TPM on glycine receptor channels. However, in presence of 1 mM glycine + 1 mM TPM, the desensitization got faster and the peak current amplitude decreased. After the end of glycine + TPM pulses, off-currents occurred, suggestive for a specific channel block mechanism.

Drug Resistance in Epilepsy: Putative Neurobiologic and Clinical Mechanisms

Drug-resistant epilepsy with uncontrolled severe seizures despite state-of-the-art medical treatment continues to be a major clinical problem for up to one in three patients with epilepsy. Although drug resistance may emerge or remit in the course of epilepsy or its treatment, in most patients, drug resistance seems to be continuous and to occur de novo. Unfortunately, current antiepileptic drugs (AEDs) do not seem to prevent or to reverse drug resistance in most patients, but add-on therapy with novel AEDs is able to exert a modest seizure reduction in as many as 50% of patients in short-term clinical trials, and a few become seizure free during the trial. It is not known why and how epilepsy becomes drug resistant, while other patients with seemingly identical seizure types can achieve seizure control with medication. Several putative mechanisms underlying drug resistance in epilepsy have been identified in recent years. Based on experimental and clinical studies, two major neurobiologic theories have been put forward: (a) removal of AEDs from the epileptogenic tissue through excessive expression of multidrug transporters, and (b) reduced drug-target sensitivity in epileptogenic brain tissue. On the clinical side, genetic and clinical features and structural brain lesions have been associated with drug resistance in epilepsy. In this article, we review the laboratory and clinical evidence to date supporting the drug-transport and the drug-target hypotheses and provide directions for future research, to define more clearly the role of these hypotheses in the clinical spectrum of drug-resistant epilepsy.

Beta-carbolines induce apoptosis in cultured cerebellar granule neurons via the mitochondrial pathway

N-butyl-beta-carboline-3-carboxylate (betaCCB) is, together with 2-methyl-norharmanium and 2,9-dimethylnorharmanium ions, an endogenously occurring beta-carboline. Due to their structural similarities with the synthetic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), harman and norharman compounds have been proposed to be involved in the pathogenesis of Parkinson's disease. While also structurally related, betaCCB has received much less interest in that respect although we had previously demonstrated that it induces the apoptotic cell death of cultured cerebellar granule neurons (CGNs). Herein, we have investigated the molecular events leading to CGN apoptosis upon betaCCB treatment. We first demonstrated that betaCCB-induced apoptosis occurs in neurons only, most likely as a consequence of a specific neuronal uptake as shown using binding/uptake experiments. Then we observed that, in betaCCB-treated CGNs, caspases 9, 3 and 8 were successively activated, suggesting an activation of the mitochondrial pathway. Consistently, betaCCB also induced the release from the mitochondrial intermembrane space of two pro-apoptotic factors, i.e. cytochrome c and apotptosis inducing factor (AIF). Interestingly, no mitochondrial membrane depolarisation was associated with this release, suggesting a mitochondrial permeability transition pore-independent mechanism. The absence of any neuroprotective effect provided by two mPTP inhibitors, i.e. cyclosporine A and bongkrekic acid, further supported this hypothesis. Together, these results show that betaCCB is specifically taken up by neuronal cells where it triggers a specific permeabilization of the outer mitochondrial membrane and a subsequent apoptotic cell death.

Developmental Regulation of β-Carboline-Induced Inhibition of Glycine-Evoked Responses Depends on Glycine Receptor β Subunit Expression

In this work, we show that beta-carbolines, which are known negative allosteric modulators of GABA(A) receptors, inhibit glycine-induced currents of embryonic mouse spinal cord and hippocampal neurons. In both cell types, beta-carboline-induced inhibition of glycine receptor (GlyR)-mediated responses decreases with time in culture. Single-channel recordings show that the major conductance levels of GlyR unitary currents shifts from high levels (> or = 50 pS) in 2 to 3 days in vitro (DIV) neurons to low levels (<50 pS) in 11 to 14 DIV neurons, assessing the replacement of functional homomeric GlyR by heteromeric GlyR. In cultured spinal cord neurons, the disappearance of beta-carboline inhibition of glycine responses and high conductance levels is almost complete in mature neurons, whereas a weaker decrease in beta-carboline-evoked glycine response inhibition and high conductance level proportion is observed in hippocampal neurons. To confirm the hypothesis that the decreased sensitivity of GlyR to beta-carbolines depends on beta subunit expression, Chinese hamster ovary cells were permanently transfected either with GlyR alpha2 subunit alone or in combination with GlyR beta subunit. Single-channel recordings revealed that the major conductance levels shifted from high levels (> or = 50 pS) in GlyR-alpha2-transfected cells to low levels (<50 pS) in GlyR-alpha2+beta-containing cells. Consistently, both picrotoxin- and beta-carboline-induced inhibition of glycine-gated currents were significantly decreased in GlyR-alpha2+beta-transfected cells compared with GlyR-alpha2-containing cells. In summary, we demonstrate that the incorporation of beta subunits in GlyRs confers resistance not only to picrotoxin but also to beta-carboline-induced inhibition. Furthermore, we also provide evidence that hippocampal neurons undergo in vitro a partial maturation process of their GlyR-mediated responses.

Effects of levetiracetam on spike and wave discharges in WAG/Rij rats

Effects of the novel anti-epileptic drug levetiracetam (50 and 100 mg/kg) on spike and wave discharges (SWDs) of WAG/Rij rats were studied. Levetiracetam decreased the incidence, average duration, total duration and peak frequency of the SWDs. There was no difference between the two doses. These results agree with results obtained in Genetic Absence Epilepsy Rat from Strasbourg (GAERS). Furthermore, the decrease of the SWD peak frequency might support the suggestions that levetiracetam might have a GABAergic mechanism of action.

The antiepileptic drug levetiracetam decreases the inositol 1,4,5-trisphosphate-dependent [Ca2+]I increase induced by ATP and bradykinin in PC12 cells

The present study explores the hypothesis that the new anti-epileptic drug levetiracetam (LEV) could interfere with the inositol 1,4,5-trisphosphate (IP(3))-dependent release of intracellular Ca(2+) initiated by G(q)-coupled receptor activation, a process that plays a role in triggering and maintaining seizures. We assessed the effect of LEV on the amplitude of [Ca(2+)](i) response to bradykinin (BK) and ATP in single Fura-2/acetoxymethyl ester-loaded PC12 rat pheochromocytoma cells, which express very high levels of LEV binding sites. LEV dose-dependently reduced the [Ca(2+)](i) increase, elicited either by 1 microM BK or by 100 microM ATP (IC(50), 0.39 +/- 0.01 microM for BK and 0.20 +/- 0.01 microM for ATP; Hill coefficients, 1.33 +/- 0.04 for BK and 1.38 +/- 0.06 for ATP). Interestingly, although the discharge of ryanodine stores by a process of calcium-induced calcium release also took place as part of the [Ca(2+)](i) response to BK, LEV inhibitory effect was mainly exerted on the IP(3)-dependent stores. In fact, the drug was still effective after the pharmacological blockade of ryanodine receptors. Furthermore, LEV did not affect Ca(2+) stored in the intracellular deposits since it did not reduce the amplitude of [Ca(2+)](i) response either to thapsigargin or to ionomycin. In conclusion, LEV inhibits Ca(2+) release from the IP(3)-sensitive stores without reducing Ca(2+) storage into these deposits. Because of the relevant implications of IP(3)-dependent Ca(2+) release in neuron excitability and epileptogenesis, this novel effect of LEV could provide a useful insight into the mechanisms underlying its antiepileptic properties.

Benefit-Risk Assessment of Levetiracetam in the Treatment of Partial Seizures

Levetiracetam is a novel antiepileptic drug that has been demonstrated as being effective in the management of partial seizures. It is rapidly and completely absorbed after oral administration and it is predominantly eliminated as unchanged drug in the urine. Its metabolism is independent of the cytochrome P450 enzyme system, nor does it induce cytochrome P450 enzymes. As a result of its pharmacokinetic features, levetiracetam has not been demonstrated to interact with other drugs in either direction. In double-blind, placebo-controlled trials, all the levetiracetam dosages tested were effective, including 1000 mg/day, 2000 mg/day and 3000 mg/day. The ineffective dose is not known. Efficacy seemed to be maintained in long-term studies, with no evidence of tolerance. In major double-blind, placebo-controlled trials discontinuation rates because of adverse events were 6.9-10.9% for levetiracetam-treated patients (all doses) compared with 5.3-8.6% for placebo-treated patients. The most common adverse events that differed between treatment groups and placebo control groups were somnolence, asthenia, dizziness and, in the US study, infection. Since levetiracetam was marketed, behavioural effects have been reported, namely irritability, agitation, anger and aggressive behaviour. These adverse effects are more likely in learning disabled individuals, those with prior psychiatric history and those with symptomatic generalised epilepsy. Overall, the risk has been estimated at 12-15%. Laboratory parameters overall seem to be not significantly affected by levetiracetam, although slight trends to lower white and red blood cell counts were detected in the studies. No organ toxicity has been described so far, with patient exposures exceeding 500,000. In summary, levetiracetam exhibits a very favourable safety profile in patients with partial onset seizures. Whereas somnolence, asthenia and dizziness were the most prominent adverse effects in clinical trials, behavioural adverse effects have generally been the most common reason for drug discontinuation in clinical practice.

Levetiracetam in refractory epilepsy: a prospective observational study

This prospective open-label study used flexible dosing schedules of levetiracetam (LEV) in patients with refractory epilepsy attending a single centre to explore its effectiveness in everyday clinical practice. One hundred and fifty-six patients with uncontrolled localisation-related or idiopathic-generalised epilepsy were prescribed adjunctive LEV following a 3-month baseline. The primary end points were seizure freedom for at least 6 months, > or = 50% reduction (responder) or <50% reduction for 6 months, or discontinuation of LEV due to lack of efficacy, adverse effects or both. Overall, 40 (26%) patients became seizure free on adjunctive LEV, including 8 (40%) with idiopathic-generalised epilepsy. Twenty-five (63%) of the seizure-free patients took 1000 mg LEV per day or less. A further 33 (21%) patients were classified as responders. LEV was withdrawn in 46 (29%) patients (27 adverse effects, 8 lack of efficacy, 11 both). Intolerable sedation, reported by 20 (13%) patients, was the commonest complaint leading to treatment failure. Behavioural side effects led to LEV withdrawal in 7 (5%) patients. LEV is an effective adjunctive treatment for refractory idiopathic and localisation-related epilepsies. Many patients who responded optimally to LEV did so at 1000 mg per day or less.

Monotherapy treatment of bipolar disorder with levetiracetam

Bipolar patients with early-onset, comorbid substance abuse, rapid cycling, and mixed episodes are difficult to treat and frequently require rational polypharmacy. When polypharmacy is unsuccessful, the clinician must consider the off-label use of newer psychotropics. Levetiracetam is a novel anticonvulsant with antikindling, inhibitory, and neuroprotective properties that is effective in an animal model of mania. This case report describes a patient with treatment-resistant rapid cycling bipolar disorder who failed 15 psychotropics, individually or in various combinations (maximum of 6), but ultimately responded to levetiracetam monotherapy and remained without bipolar features during 1 year of maintenance treatment, excluding 1 week during which the patient was medicine noncompliant. Further, methylphenidate used to treat comorbid attention deficit disorder did not precipitate manic features. Levetiracetam should be further studied for its potential use in the treatment of bipolar disorders.

Comparative pharmacokinetics and metabolism of levetiracetam, a new anti-epileptic agent, in mouse, rat, rabbit and dog

1: The pharmacokinetics and metabolism of 14C-levetiracetam, a new anti-epileptic agent, in mouse, rat, rabbit and dog after a single oral dose were investigated. Moreover, the in vitro hydrolysis of levetiracetam to its major carboxylic metabolite by rat tissue homogenates was investigated to identify tissues involved in the production of the metabolite. Data are also presented on the induction of the enzyme(s) involved in levetiracetam hydrolysis in the rat. 2: Levetiracetam was rapidly and almost completely absorbed. The unchanged drug accounted for a very high percentage of plasma radioactivity. Levetiracetam did not bind to plasma proteins. Although brain radioactivity concentrations were lower than those of whole blood at early time points, brain-to-blood ratios increased over time. The predominant route of elimination of total 14C was excretion via urine, accounting for about 81, 93, 87 and 89% of the dose in the mouse, rat, rabbit and dog, respectively. Consequently, levetiracetam was poorly metabolized. It was submitted in vivo to hydrolysis and/or oxidation. Hydrolysis of the amide function of levetiracetam produced the corresponding acid. However, levetiracetam could also be oxidized at positions 3 and 4 of the 2-oxopyrrolidine ring. Finally, the compound and the corresponding acid metabolite could be oxidized at position 5 of the 2-oxopyrrolidine ring and then hydrolysed with the opening of the ring. 3: All the investigated rat tissues (liver, kidney, lung, brain, small intestine mucosa) had the potential to produce the acid metabolite. By contrast, the acid was undetectable following incubation of levetiracetam with buffer alone or heat-denaturated liver fractions. 4: No marked species or sex differences were observed in the absorption, disposition and metabolism of levetiracetam. 5:The hydrolysis of levetiracetam is carried out by an enzymatic process characterized by a broad tissue distribution. In the rat, the enzyme system hydrolysing levetiracetam is not induced by phenobarbital, at least under the experimental conditions used herein, whereas the enzyme system(s) involved in the other metabolic pathways is induced.

Levetiracetam influences human motor cortex excitability mainly by modulation of ion channel function—a TMS study

PURPOSE

Levetiracetam (LEV) is a new compound with anticonvulsive efficacy in focal and generalized epilepsies. Recent in vitro studies suggest LEV to act as a selective N-type-calcium-channel blocker.

METHODS

We used transcranial magnetic stimulation (TMS) in order to investigate if ion-channel blockade is relevant to the inhibitory CNS effects of LEV in vivo and if motor thresholds (MTs) are a valid TMS parameter to detect this mode of action. In a double blind, placebo-controlled, crossover study, the effects of single oral doses of 500 and 2000 mg LEV on motor thresholds, recruitment curves (REC), cortical induced silent period (CSP) and on intracortical inhibition (ICI) and facilitation (ICF) were studied in 10 healthy subjects.

RESULTS

A significant increase of motor thresholds was noticed after 2000 mg LEV as compared to placebo. The recruitment curve showed a trend towards motor evoked potential (MEP) amplitude reduction after LEV. LEV had no significant effect on CSP or on intracortical excitability as measured by inhibition and facilitation.

CONCLUSIONS

We conclude that the modulation of ion-channel function, reflected by motor threshold elevation and a trend towards recruitment curve suppression, is relevant to the inhibitory CNS effects of LEV in vivo, and therefore, may contribute to the anticonvulsive efficacy of LEV. GABAergic or glutamatergic mechanisms seem to be less important in vivo as measured by TMS.

New medication treatment options for bipolar disorders

OBJECTIVE

To assess new treatment options for bipolar disorders.

METHOD

Controlled studies of new treatments for bipolar disorders were identified by computerized searches and reviews of scientific meeting proceedings, and were compiled by drug category.

RESULTS

Two main categories of medications, newer anticonvulsants and newer antipsychotics, are yielding emerging new treatment options for bipolar disorders. Newer anticonvulsants have diverse psychotropic profiles, and although not generally effective for acute mania, may have utility for other aspects of bipolar disorders (e.g. lamotrigine for maintenance or acute bipolar depression), or for comorbid conditions (e.g. gabapentin for anxiety or pain, topiramate for obesity, bulimia, alcohol dependence, or migraine, and zonisamide for obesity). In contrast, newer antipsychotics generally appear effective for acute mania, and some may ultimately prove effective in acute depression (e.g. olanzapine combined with fluoxetine, quetiapine) and maintenance (e.g. olanzapine).

CONCLUSION

Emerging research is yielding new treatment options for bipolar disorders and comorbid conditions.

Mechanisms of action for the commonly used antiepileptic drugs: relevance to antiepileptic drug-associated neurobehavioral adverse effects

Antiepileptic drugs exert their anticonvulsant effects by interfering with brain processes that involve structures that are also involved in learning, memory, and emotional behavior. Thus, modulation of ion channels, neurotransmitters, second messengers, and other processes by antiepileptic drugs, although helpful in controlling seizures, can interfere with normal brain function in undesired ways. The specific mechanism(s) of action of an antiepileptic drug can increase the risk for particular types of adverse events. In this review, we examine the cognitive and behavioral effects of antiepileptic drugs in animal models. Although animal studies, in many respects, do not mimic clinical experience, the data suggest a connection between certain mechanisms of antiepileptic action and the occurrence of cognitive adverse effects. Specifically, antiepileptic drugs with traditional gamma-aminobutyric acid (GABA)ergic mechanisms have the most detrimental effects on cognitive function, possibly because they impair attention. Conversely, drugs with the predominant effects at Na+ channels appear to have minimal impact on cognition. Levetiracetam, with its nonconventional GABAergic and Ca2+ channel effects, has shown positive cognitive effects in animal studies. Antiglutamatergic drugs have the potential to be a double-edged sword: they can interfere with consolidation of learning and memory but can also provide neuroprotection in addition to their antiseizure effects.

Choosing antiepileptic drugs for developmentally normal children with specific epilepsy syndromes and behavioral disorders

Antiepileptic drugs are often used for the treatment of both epilepsy and a wide range of behavioral and psychiatric disorders. The treatment of patients with epilepsy has been the proving ground for antiepileptic drugs, not only with respect to their efficacy in the treatment of seizures but also for clarifying their dose-related and idiosyncratic adverse events. This information has been useful in treating patients with behavioral and psychiatric disorders. Indeed, the number of prescriptions written for many antiepileptic drugs for nonepileptic uses far exceeds those written for the same drugs for epilepsy. Because patients with chronic epilepsy have a higher incidence of axis I psychiatric disorders, physicians can choose an antiepileptic drug to treat both the epilepsy and psychiatric comorbidity in selected patients. Guided by the principles of evidence-based medicine as outlined by the American Academy of Neurology and the American Academy of Pediatrics, this article reviews the application of antiepileptic drugs for epilepsy and behavioral and psychiatric disorders in children.

Levetiracetam inhibits Na+-dependent Cl-/HCO3- exchange of adult hippocampal CA3 neurons from guinea-pigs

The novel anticonvulsant levetiracetam (LEV) was tested for effects on bioelectric activity and intracellular pH (pHi) regulation of hippocampal CA3 neurons from adult guinea-pigs. In 4-aminopyridine-treated slices, LEV (10-100 microm) reduced the frequency of action potentials and epileptiform bursts of CA3 neurons by 30-55%, while the shape of these potentials remained largely unchanged. Suppressive effects were reversed by an increase of pHi with trimethylamine (TMA). Using BCECF-AM-loaded slices, we found that LEV (10-50 microm) reversibly lowered neuronal steady-state pHi by 0.19 +/- 0.07 pH units in the presence of extracellular CO2/HCO3- buffer. In the nominal absence of extracellular CO2/HCO3- or in Na+-free CO2/HCO3(-)-buffered solution, LEV had no effect on steady-state pHi. Recovery of pHi subsequent to ammonium prepulses remained unchanged in the absence of CO2/HCO3- buffer, but was significantly reduced by LEV in the presence of CO2/HCO3- buffer. These findings show that LEV inhibits HCO3(-)-dependent acid extrusion, but has no effect on Na+/H+ exchange. LEV did not affect Na+-independent Cl-/HCO3- exchange because intracellular alkalosis upon withdrawal of extracellular Cl- remained unchanged. These data show that LEV at clinically relevant concentrations inhibits Na+-dependent Cl-/HCO3- exchange, lowers neuronal pHi, and thereby may contribute to its anticonvulsive activity.

Levetiracetam Interferes With the l-Dopa Priming Process in MPTP-Lesioned Drug-Naive Marmosets

OBJECTIVE

Levetiracetam (LEV; Keppra, UCB Pharma) has been shown to reduce established l-3,4 dihydroxyphenylalanine (l-dopa)-induced dyskinesia. This study investigated whether LEV can modify induction of dyskinesia by l-dopa or the process of priming.

METHODS

Drug-naive MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) -lesioned marmosets were treated for 21 days with l-dopa/LEV or l-dopa alone. Subsequently, the animals were left untreated for 1 week and then both groups were challenged with a single dose of l-dopa alone on day 29. Behavior was assessed by automated activity counts and by post hoc analysis of videotapes using validated rating scales.

RESULTS

LEV had no significant effect on the appearance of dyskinesia when administered de novo in combination with l-dopa. However, after a week of drug holiday, the 2 groups exhibited a different response to an acute l-dopa challenge. Thus, animals previously treated with l-dopa alone exhibited a similar level of dyskinesia to that seen on day 21 of the repeated treatment phase of the study. However, animals previously treated with l-dopa/LEV demonstrated significantly reduced dyskinesia compared with day 21 of the repeated treatment phase of the study.

CONCLUSIONS

LEV does not modify the onset of dyskinesia following de novo treatment with l-dopa. However, concomitant treatment with l-dopa/LEV reduces the level of dyskinesia induced by l-dopa following a drug holiday. Thus, prior treatment with LEV appears to modify the mechanisms responsible for the maintenance of l-dopa-induced dyskinesia.

The synaptic vesicle protein SV2A is the binding site for the antiepileptic drug levetiracetam

Here, we show that the synaptic vesicle protein SV2A is the brain binding site of levetiracetam (LEV), a new antiepileptic drug with a unique activity profile in animal models of seizure and epilepsy. The LEV-binding site is enriched in synaptic vesicles, and photoaffinity labeling of purified synaptic vesicles confirms that it has an apparent molecular mass of approximately 90 kDa. Brain membranes and purified synaptic vesicles from mice lacking SV2A do not bind a tritiated LEV derivative, indicating that SV2A is necessary for LEV binding. LEV and related compounds bind to SV2A expressed in fibroblasts, indicating that SV2A is sufficient for LEV binding. No binding was observed to the related isoforms SV2B and SV2C. Furthermore, there is a high degree of correlation between binding affinities of a series of LEV derivatives to SV2A in fibroblasts and to the LEV-binding site in brain. Finally, there is a strong correlation between the affinity of a compound for SV2A and its ability to protect against seizures in an audiogenic mouse animal model of epilepsy. These experimental results suggest that SV2A is the binding site of LEV in the brain and that LEV acts by modulating the function of SV2A, supporting previous indications that LEV possesses a mechanism of action distinct from that of other antiepileptic drugs. Further, these results indicate that proteins involved in vesicle exocytosis, and SV2 in particular, are promising targets for the development of new CNS drug therapies.

Effects of seven clinically important antiepileptic drugs on inhibitory glycine receptor currents in hippocampal neurons

Although potentiation of the inhibitory glycine receptor (GlyR) may contribute to the mechanism of action of antiepileptic drugs (AEDs), the effects of AEDs on GlyRs have not been investigated in detail in forebrain neurons. We examined the effects of seven clinically important AEDs on GlyR-mediated currents using whole-cell patch clamp recordings from cultured embryonic mouse hippocampal neurons. At high therapeutic concentrations, topiramate (in 24% of neurons) and pentobarbital reversibly decreased glycine currents to 89+/-6 % and 81+/-7 % of control, respectively. At or below therapeutic concentrations, carbamazepine, felbamate, gabapentin, phenytoin, and valproate had no effect on glycine currents, while at supratherapeutic concentrations these agents produced modest reversible inhibition. We conclude that GlyR potentiation does not contribute to the antiepileptic action of the seven AEDs examined.

Efficacy and safety of levetiracetam in pediatric migraine

BACKGROUND

Headache is a frequent occurrence among children and adolescents. Chronic headaches can be severe and disabling, and require prophylactic treatment; however, additional data on the use of prophylactic medications for migraine in children are needed.

OBJECTIVE

To review the efficacy and safety of levetiracetam (Keppra) in pediatric patients with a history of recurrent headache.

DESIGN/METHODS

Data from 19 pediatric patients were retrospectively reviewed. The initial dose of levetiracetam was usually 125 or 250 mg twice daily, but varied depending upon clinical judgment.

RESULTS

Charts of 9 girls and 10 boys (mean age, 11.9 years) were reviewed. A variety of medications, including triptans, had been used before initiating treatment with levetiracetam. Mean headache frequency before treatment was 6.3 per month (standard deviation [SD], 3.8; confidence interval [CI], 4.4 to 8.1). Duration of headaches ranged from 0.25 to 8 years. Migraine (63.2%) and migraine with aura (15.8%) were the most common types of headache reported. Most patients (89.5%) had headaches that were severe. After treatment, the mean headache frequency decreased to 1.7 per month (SD, 2.7; CI, 0.4 to 3.0), representing a reduction compared with baseline (P <.0001). Levetiracetam eliminated headaches in 10 patients (52.6%), and 7 patients (36.8%) had less severe and less frequent headaches. Levetiracetam did not have an effect on headaches in 2 patients (10.5%). Mean duration of treatment with levetiracetam was 4.1 months. Doses ranged from 125 to 750 mg twice daily. Sixteen patients (84.2%) reported no side effects on levetiracetam. One patient experienced asthenia/somnolence and dizziness, and irritable, hyperactive, and hostile behavior led to discontinuation of levetiracetam in another patient. A third patient experienced irritability and moodiness that attenuated after 1 month of treatment and did not require discontinuation.

CONCLUSIONS

In this small retrospective review, levetiracetam was found to be generally well tolerated and appears to be a promising candidate for additional evaluation in well-controlled clinical trials of pediatric patients with migraine.

Piracetam and TRH analogues antagonise inhibition by barbiturates, diazepam, melatonin and galanin of human erythrocyte D-glucose transport

1 Nootropic drugs increase glucose uptake into anaesthetised brain and into Alzheimer's diseased brain. Thyrotropin-releasing hormone, TRH, which has a chemical structure similar to nootropics increases cerebellar uptake of glucose in murine rolling ataxia. This paper shows that nootropic drugs like piracetam (2-oxo 1 pyrrolidine acetamide) and levetiracetam and neuropeptides like TRH antagonise the inhibition of glucose transport by barbiturates, diazepam, melatonin and endogenous neuropeptide galanin in human erythrocytes in vitro. 2 The potencies of nootropic drugs in opposing scopolamine-induced memory loss correlate with their potencies in antagonising pentobarbital inhibition of erythrocyte glucose transport in vitro (P<0.01). Less potent nootropics, D-levetiracetam and D-pyroglutamate, have higher antagonist Ki's against pentobarbital inhibition of glucose transport than more potent L-stereoisomers (P<0.001). 3 Piracetam and TRH have no direct effects on net glucose transport, but competitively antagonise hypnotic drug inhibition of glucose transport. Other nootropics, like aniracetam and levetiracetam, while antagonising pentobarbital action, also inhibit glucose transport. Analeptics like bemigride and methamphetamine are more potent inhibitors of glucose transport than antagonists of hypnotic action on glucose transport. 4 There are similarities between amino-acid sequences in human glucose transport protein isoform 1 (GLUT1) and the benzodiazepine-binding domains of GABAA (gamma amino butyric acid) receptor subunits. Mapped on a 3D template of GLUT1, these homologies suggest that the site of diazepam and piracetam interaction is a pocket outside the central hydrophilic pore region. 5 Nootropic pyrrolidone antagonism of hypnotic drug inhibition of glucose transport in vitro may be an analogue of TRH antagonism of galanin-induced narcosis.

Is the persistent sodium current a specific target of anti-absence drugs?

The persistent Na+ current (INaP) has been proposed as the putative target of the anti-absence antiepileptic drugs. Accordingly, the effect of reference anti-absence drugs ethosuximide (ESM) and valproate (VPA), and of the new antiepileptic drug levetiracetam (LEV), on INaP have been tested in CA1 hippocampal neurons and compared to the classic anticonvulsant phenytoin (PHT) and the neuroprotective agent riluzole (RIL). Whole-cell patch-clamp recordings of the slowly inactivating current, fully characterized as INaP, were performed with a standard voltage-step protocol on thin hippocampal slices prepared from rat brain. Both PHT (100 microM) and RIL (10 microM) strongly depressed INaP, whereas ESM (1 mM) induced a slight decrease of INaP and VPA (1 mM) had no effect. Likewise, 60-min perfusion with relevant concentrations of LEV (10, 32 or 100 microM) did not modify INaP. In conclusion, these data question the impact of INaP depression as an anti-absence mechanism, and also disclaim the involvement of INaP in the antiepileptic mechanism of LEV.

Emergent properties of CNS neuronal networks as targets for pharmacology: application to anticonvulsant drug action

CNS drugs may act by modifying the emergent properties of complex CNS neuronal networks. Emergent properties are network characteristics that are not predictably based on properties of individual member neurons. Neuronal membership within networks is controlled by several mechanisms, including burst firing, gap junctions, endogenous and exogenous neuroactive substances, extracellular ions, temperature, interneuron activity, astrocytic integration and external stimuli. The effects of many CNS drugs in vivo may critically involve actions on specific brain loci, but this selectivity may be absent when the same neurons are isolated from the network in vitro where emergent properties are lost. Audiogenic seizures (AGS) qualify as an emergent CNS property, since in AGS the acoustic stimulus evokes a non-linear output (motor convulsion), but the identical stimulus evokes minimal behavioral changes normally. The hierarchical neuronal network, subserving AGS in rodents is initiated in inferior colliculus (IC) and progresses to deep layers of superior colliculus (DLSC), pontine reticular formation (PRF) and periaqueductal gray (PAG) in genetic and ethanol withdrawal-induced AGS. In blocking AGS, certain anticonvulsants reduce IC neuronal firing, while other agents act primarily on neurons in other AGS network sites. However, the NMDA receptor channel blocker, MK-801, does not depress neuronal firing in any network site despite potently blocking AGS. Recent findings indicate that MK-801 actually enhances firing in substantia nigra reticulata (SNR) neurons in vivo but not in vitro. Thus, the MK-801-induced firing increases in SNR neurons observed in vivo may involve an indirect effect via disinhibition, involving an action on the emergent properties of this seizure network.

A novel approach to the psychopharmacologic treatment of insomnia in depression

BACKGROUND

Depressed patients who respond to anti-depressant drugs but have persisting insomnia can be hypothesized as having one foot on the bipolar spectrum. In this hypothesis, the insomnia would respond to augmentation of the anti-depressants with anti-kindling agents (i.e., anti-convulsant drugs for the purposes of this paper) in the same way that many anti-convulsants are effective in bipolar disorders as mood-stabilizers from above (anti-manic agents) or below (anti-depressants).

CASE REPORTS

Cases supporting this augmentation strategy are presented. The patients met DSM-IV criteria for recurrent major depression, depression with psychotic features, and depression NOS. There was no discernible history of mania or hypomania and all had insomnia that did not respond or partially responded to anti-depressant drugs singly or in combinations. All responded to the addition of anti-convulsant drugs.

DISCUSSION

This augmentation strategy seems to be an effective treatment for chronic insomnia in depression, but controlled studies are needed to quantify and qualify these effects. This strategy's effectiveness may be due to the anti-kindling or inhibitory effects of anti-convulsant drugs, which are often GABAergic. Since it is becoming clear that bipolar spectrum disorders are misdiagnosed as unipolar depression at an alarming rate, and since anti-depressants often have deleterious effects on the course of bipolar illness, perhaps most depressed patients should be protected with an anti-convulsant whenever they are started on an anti-depressant.

Levetiracetam treatment of idiopathic generalised epilepsy

Levetiracetam (LEV) is effective for treating localisation-related epilepsy, but it is uncertain whether it is effective for treating idiopathic generalised epilepsy. We compared 12-week baseline and LEV treatment periods for patients with generalised seizure types-myoclonic, tonic-clonic and absence seizures--who had failed other anticonvulsants. The majority of 55 patients (76%) had >50% seizure reduction with LEV therapy, 40% became seizure-free; 15% discontinued LEV due to adverse events, mostly sedation. This is preliminary evidence that LEV is effective for treating idiopathic generalised epilepsy.

Unidirectional Cross-tolerance from Levetiracetam to Carbamazepine in Amygdala-kindled Seizures

PURPOSE

Tolerance is a potential problem in long-term anticonvulsant therapy of epilepsy, bipolar disorder, and neuropathic pain. The present study was designed to determine whether cross-tolerance occurs between levetiracetam (LEV) and carbamazepine (CBZ) in amygdala-kindled rats.

METHODS

Male Sprague-Dawley rats were implanted with an electrode into the left amygdala. While kindling stimulation was started, animals received repeated treatment (i.p.) with saline (n = 7) or LEV (150 mg/kg, n = 8). Saline-injected rats were subsequently challenged with a single dose of 150 mg/kg LEV when full kindling developed (stage > or =4). Both groups of rats were then administered long-term CBZ (5 mg/kg) until rats developed complete tolerance. All CBZ-tolerant rats were subsequently re-exposed to LEV (150 mg/kg) for an additional 10 consecutive days.

RESULTS

Repeated LEV treatment significantly suppressed the increase in seizure stage, seizure duration, and afterdischarge duration induced by amygdala stimulation, markedly increasing the number of stimulations to achieve a kindling major motor seizure. The LEV challenge produced a more robust suppression of seizure stage in saline-injected rats compared with LEV-treated animals. CBZ treatment markedly suppressed fully kindled seizures in rats initially injected with saline, and then anticonvulsant tolerance rapidly developed after 3-4 days of repeated treatment. In contrast, rats that had initially received repeated LEV treatment did not show a response to treatment with CBZ (5 mg/kg). When CBZ-tolerant rats were subsequently exposed to LEV (150 mg/kg), noticeable anticonvulsant effects were observed; but these were gradually lost with increasing numbers of LEV exposures.

CONCLUSIONS

Whereas LEV shows potent antiepileptogenic and anticonvulsant effects in amygdala-kindled rats, its repeated treatment induces anticonvulsant tolerance and unidirectional cross-tolerance to CBZ. In contrast, anticonvulsant tolerance to CBZ does not transfer to LEV. The mechanistic implications of the present results for clinical therapeutics remain to be evaluated.

Levetiracetam: its use in partial-onset seizure

Levetiracetam is one of the newer antiepileptic drugs released within the past decade and is indicated for use as adjunctive therapy in adults with partial-onset seizures. It is a novel antiepileptic drug with a unique activity profile and is chemically unrelated to existing antiepileptic drugs. The mechanism of action of levetiracetam does not involve conventional modulation of any of the three main mechanisms underlying classical antiepileptic drug activity. Levetiracetam pharmacokinetics are linear and time invariant. In addition, levetiracetam has shown clinical efficacy in randomized controlled trials for treatment of partial-onset seizures. Levetiracetam also has favorable pharmacokinetic and safety profiles. The purpose of this article is to examine the drug profile of levetiracetam, based on information derived from its preclinical and clinical studies. Furthermore, this article seeks to highlight key characteristics of levetiracetam that clinicians should consider in order to deliver individualized care to patients with epilepsy.

Anxiolytic effects of the novel anti-epileptic drug levetiracetam in the elevated plus-maze test in the rat

There is clinical evidence of anxiolytic action of several anti-epileptic drugs. We evaluated the effects of levetiracetam (Keppra), a new generation anti-epileptic drug, in the plus-maze animal test for anxiolytic activity. Levetiracetam at 17 and 54 mg/kg intraperitoneally (i.p.) was without effect when tested in naive rats. A modified version of the test was subsequently used in which open-arm exploration was decreased by exposure of the rats to a four-open-arm maze 24 h prior to drug treatment and testing. Under these conditions of enhanced anxiety, levetiracetam, 5.4 to 54 mg/kg, dose-dependently increased open-arm exploration. Chlordiazepoxide 5 mg/kg had similar effects although buspirone 0.1 to 1.0 mg/kg was inactive. The results with levetiracetam substantiate similar findings of its anxiolytic actions against chlordiazepoxide withdrawal-induced anxiety in mice and in a modified Vogel test in rats and support a potential clinical use of this drug in anxiety states.

Localization and photoaffinity labelling of the levetiracetam binding site in rat brain and certain cell lines

Levetiracetam (2S-(2-oxo-1-pyrrolidinyl)butanamide, KEPPRA, a novel antiepileptic drug, has been shown to bind to a specific binding site located in the brain (Eur. J. Pharmacol. 286 (1995) 137). To identify the protein constituent of the levetiracetam binding site in situ, we synthesized the photoaffinity label [3H]ucb 30889 ((2S)-2-[4-(3-azidophenyl)-2-oxopyrrolidin-1-yl]butanamide), a levetiracetam analog with higher affinity for the levetiracetam binding site. This radioligand was used to map the levetiracetam binding site within the brain and to study its cellular and subcellular distribution. Autoradiography experiments using [3H]ucb 30889 in rat brain revealed a unique distribution profile that did not match that of classical receptors known to be involved in the generation of epileptic seizures. There was a high level of binding in the dentate gyrus, the superior colliculus, several thalamic nuclei, the molecular layer of the cerebellum and to a lesser extent in the cerebral cortex, the striatum and the hypothalamus. The levetiracetam binding site was restricted to neuronal cell types, undifferentiated PC12 cells and was highly enriched in synaptic vesicles. [3H]ucb 30889 was also used in photoaffinity labelling studies and shown to bind covalently to a membrane protein with a molecular weight of approximately 90 kDa.

Binding characteristics of [3H]ucb 30889 to levetiracetam binding sites in rat brain

Levetiracetam (2S-(2-oxo-1-pyrrolidinyl)butanamide, KEPPRA, a novel antiepileptic drug, has been shown to bind to a specific binding site located in brain (levetiracetam binding site [Eur. J. Pharmacol. 286 (1995) 137]). However, [3H]levetiracetam displayed only micromolar affinity for these sites making it an unsuitable probe for further characterization. The present study describes the binding properties of an analogue of levetiracetam: [3H]ucb 30889, (2S)-2-[4-(3-azidophenyl)-2-oxopyrrolidin-1-yl]butanamide. [3H]ucb 30889 binds reversibly to specific binding sites in rat brain. Kinetics at 4 degrees C were biphasic with half-times of association and dissociation of, respectively, 3 and 4 min for the fast component and 47 and 61 min for the slow component. [3H]ucb 30889 saturation binding curves were compatible with the labelling of a homogenous population of binding sites having a B(max) of 4496+/-790 fmol/mg protein (mean+/-S.D., n=5) and a K(d) of 62+/-20 nM (mean+/-S.D., n=5), a 20-fold increase in affinity compared to [3H]levetiracetam. Competition binding curves with ligands known to interact with levetiracetam binding sites and tissue distribution restricted to the brain indicated that [3H]ucb 30889 and [3H]levetiracetam bind to the same site. Although levetiracetam binding sites and GABA(A) (gamma-aminobutyric acid) receptors share some ligands such as pentobarbital and pentylenetetrazol, experiments performed with [35S]TBPS (tert-butyl-bicyclo[2.2.2]phosporothionate), a probe for the GABA(A) Cl(-) channel do not support the hypothesis that levetiracetam binding sites are part of the GABA(A) receptor complex. Preliminary autoradiography studies in rat brain revealed that [3H]ucb 30889 labels specific sites in all brain regions and that this binding is concentration-dependently displaced by levetiracetam.

Selection criteria for the clinical use of the newer antiepileptic drugs

In recent years, several new antiepileptic drugs (AEDs) have been licensed: felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, vigabatrin and zonisamide. These drugs have proven efficacy as add-on therapy in patients with difficult-to-treat partial epilepsy, as 20-50% of patients treated in add-on trials experienced a seizure reduction of >or=50%. Relatively few trials have been conducted to evaluate these drugs as monotherapy for patients with newly diagnosed epilepsy. In the monotherapy trials that have been conducted, the newer drugs were often as efficacious as conventional drugs, and their tolerability was often better. However, the methodology of these trials can be criticised. Because of the relative lack of robust data for the newer agents, the conventional drugs have thus far maintained their status as first-line monotherapy. However, when first-line monotherapy fails, an alternative drug has to be chosen from the available conventional and newer drugs. This article aims to give detailed background information on the newer AEDs in order to enable physicians to make a rational choice from the available drugs for individual patients. Data are provided for the different newer AEDs on mechanisms of action; efficacy in refractory partial epilepsy, newly diagnosed epilepsy in adults and generalised seizure types; adverse effects; pharmacokinetics; and use in special patient categories.

Benzodiazepines block alpha2-containing inhibitory glycine receptors in embryonic mouse hippocampal neurons

Inhibitory glycine receptors (GlyRs) in the mammalian cortex probably contribute to brain development and to maintaining tonic inhibition. Given their presence throughout the cortex, their modulation likely has important physiological consequences. Although benzodiazepines potentiate gamma-aminobutyric acidA receptors (GABAARs), they may also modulate GlyRs because binding studies initially suggested that they act at GlyRs. Furthermore, their diminished ability to potentiate neonatal GABAARs suggests that they may exert their beneficial clinical effects at another site in the developing brain. Therefore we examined the effect of benzodiazepines on whole cell currents mediated by GlyRs in cultured embryonic mouse hippocampal neurons. First, we determined the GlyR subunit composition in this preparation. Glycine, beta-alanine, and taurine activate strychnine-sensitive chloride currents in a dose-dependent manner. Maximal concentrations of the three agonists produce equal, nonadditive responses as expected of full agonists. The pharmacological properties of the GlyR currents including their pattern of modulation by picrotoxinin, picrotin, and tropisetron indicate that GlyRs consist of alpha2beta heteromers and alpha2 homomers. Reverse transcriptase polymerase chain reaction (RTPCR) studies confirmed the presence of alpha2 and beta subunits. Second, we found that micromolar concentrations of some benzodiazepines, including chlordiazepoxide and nitrazepam, inhibit GlyR currents. Nitrazepam inhibition of GlyRs is noncompetitive, is not voltage dependent, and does not reflect enhanced desensitization. Thus benzodiazepines allosterically inhibit alpha2-containing GlyRs in embryonic mouse hippocampal neurons via a "low"-affinity site.

Desynchronizing effect of levetiracetam on epileptiform responses in rat hippocampal slices

The effect of levetiracetam on neuronal hypersynchrony and hyperexcitability was examined using simultaneous extra- and intracellular recordings in rat brain slices perfused with a high K+/low Ca2+ (HKLC) fluid. These findings were compared to results obtained with carbamazepine, valproate and clonazepam. The HKLC milieu induces in hippocampal CA3 area, spontaneous interictal bursts and epileptiform responses. Levetiracetam decreased the number of population spikes per extracellular response but did not affect the number of action potentials per intracellular burst. This contrasts the effects of the reference antiepileptic drugs, which depressed both the extracellular and the intracellular bursts. These results indicate that levetiracetam is distinct from classical antiepileptic drugs by a relatively selective effect on collective neuronal responses, rather than on single neuron activity and suggests a potentially novel desynchronizing effect that probably contributes to its antiepileptic action.

Anxiolytic profile of the antiepileptic drug levetiracetam in the Vogel conflict test in the rat

The novel antiepileptic drug levetiracetam has been shown to reverse anxiogenic effects of benzodiazepine withdrawal in mice tested in an elevated plus-maze without altering the behaviour of normal mice in this model. This could suggest that the effect of levetiracetam is dependent upon the level of stress/anxiety of the animals. Levetiracetam was therefore further examined in another widely used animal model of anxiety, the Vogel conflict test. In the first experiment, water-deprived rats were submitted to a free drinking period (habituation) in a chamber equipped with a bottle of water. Twenty-four hours later, animals were returned to the same chamber but the licks to the water bottle were then punished with a foot shock (0.5 mA, 90 ms). In the second experiment, the procedure was modified by administering a foot shock at the end of the habituation period in order to induce a state of stress/anxiety (conditioned fear/ anticipatory anxiety) for subsequent testing. Levetiracetam (17 and 54 mg/kg) and chlordiazepoxide (5 mg/kg) were administered via the intraperitoneal route. The results indicated that in the first experiment only chlordiazepoxide showed a statistically significant anxiolytic effect. In contrast, in the second experiment, where the shock was given at the end of the habituation period, levetiracetam (54 mg/kg) revealed significant anxiolytic activity similar to chlordiazepoxide. This suggests that levetiracetam may have potential anxiolytic effects and may provide therapeutic benefits to individual with anxiety spectrum disorders.

Levetiracetam has no significant gamma-aminobutyric acid-related effect on paired-pulse interaction in the dentate gyrus of rats

Gamma-aminobutyric acid (GABA)ergic mechanisms of the novel antiepileptic drug, levetiracetam (Keppra), have been both favored and rejected. Since paired-pulse interaction is accepted in functionally assessing GABAergic mechanisms, we investigated whether levetiracetam affects the paired-pulse inhibition/facilitation of the field potentials, evoked in the dentate gyrus of urethane-anesthesized rats. This model revealed a strong paired-pulse inhibition at 20-ms interstimulus interval, a noteworthy paired-pulse facilitation at 80-ms interstimulus interval, and a moderate paired-pulse inhibition at 500-ms interstimulus interval. Bicuculline (3 mg/kg/h, i.v.) and baclofen (10 mg/kg, i.v.) markedly depressed paired-pulse inhibition at 20-ms interstimulus interval, while clonazepam (1 mg/kg, i.p.), diazepam (10 mg/kg, i.v.), and phenobarbital (40 mg/kg, i.v.) enhanced it. Bicuculline also depressed paired-pulse inhibition at 500-ms interstimulus interval. Bicuculline, baclofen, and diazepam reduced paired-pulse facilitation at 80-ms interstimulus interval. Distinct from these GABA(A) receptor- and GABA(B) receptor-related drugs, levetiracetam (17 and 540 mg/kg, i.v.) had no significant effect on either paired-pulse interaction in this model, a result not favoring any major role of GABAergic mechanisms in its antiseizure action.

Levetiracetam add-on for drug-resistant localization related (partial) epilepsy

BACKGROUND

The majority of patients with epilepsy have a good prognosis and their seizures are well controlled by a single antiepileptic drug. However, up to 30% develop refractory seizures, particularly those with partial seizures. In this review, we summarise the current evidence regarding a new antiepileptic drug, levetiracetam, when used as an add-on treatment for drug-resistant localization related (partial) epilepsy.

OBJECTIVES

To evaluate the effects of levetiracetam on seizures, side effects, quality of life and cognition, when used as an add-on treatment for patients with a drug-resistant localization related (partial) epilepsy.

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group trials register, the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2000). In addition, we contacted UCB SA (makers of levetiracetam) and experts in the field to seek any ongoing studies or unpublished studies.

SELECTION CRITERIA

Randomized placebo controlled add-on trials of levetiracetam in patients with a drug-resistant localization related (partial) epilepsy.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted relevant data. The following outcomes were assessed: (a) 50% or greater reduction in total seizure frequency; (b) treatment withdrawal (any reason); (c) side effects; (d) cognitive effects; (e) quality of life. Primary analyses were intention to treat. Sensitivity best and worst case analyses were also undertaken. Summary odds ratios (ORs) were estimated for each outcome. Dose response was evaluated in regression models.

MAIN RESULTS

Four trials (1023 patients) were included. All four trials had data for treatment withdrawal and side effect outcomes. Three trials (904 patients) had data for 50% or greater reduction in seizure frequency. Three trials (595 patients) had data for quality of life and cognitive outcomes. The overall Odds Ratio (OR) (95% Confidence Interval (CI)) for 50% or greater reduction in total seizure frequency outcome was 3.81 (2.78,5.22). Dose regression analysis shows clear evidence that levetiracetam reduces seizure frequency with an increase in efficacy with increasing dose of levetiracetam. Approximately 15% of patients taking 1000 mg and 20-30% of patients taking 3000 mg levetiracetam per day have a 50% or greater reduction in seizure frequency. Patients were not significantly more likely to have levetiracetam withdrawn, OR (95% CI) 1.25 (0.87,1.80). The following side effects were significantly associated with levetiracetam: dizziness 2.36 (1.21, 4.61) and infection 1.82 (1.05, 3.14) whereas accidental injury was significantly associated with placebo 0.55 (0.32, 0.93). Quality of life and cognitive effect outcomes suggest that levetiracetam has a positive effect on cognition and some aspects of quality of life.

REVIEWER'S CONCLUSIONS

Levetiracetam reduces seizure frequency when used as an add-on treatment for patients with a drug-resistant localization related (partial) epilepsy, and seems well tolerated. Minimum effective and maximum tolerated doses have not been identified. The trials reviewed were of 16-24 weeks duration and results cannot be used to confirm longer term effects. Our results cannot be extrapolated to monotherapy or to patients with other seizure types or epilepsy syndromes. Great care should also be taken with any attempt to apply these results to children.