Role of valproate across the ages. Treatment of epilepsy in children

Efficacy and safety of phenytoin and levetiracetam for acute symptomatic seizures in children with acute encephalitis syndrome: an open label, randomised controlled trial

INTRODUCTION

Seizures represent a significant comorbidity in children with acute encephalitis syndrome (AES). Despite this, there is a notable absence of randomized controlled trials (RCTs) directly comparing antiseizure medications (ASMs) in children with AES.

MATERIALS AND METHODS

This RCT aimed to assess the efficacy and safety of phenytoin and levetiracetam in controlling seizures among children with AES. Both ASMs were administered with a loading followed by maintenance dose. After a 12-week period, children exhibiting a normal electroencephalogram and no seizure recurrence underwent tapering and discontinuation of ASM. Clinical follow-up occurred daily for the first week, and subsequently at 4, 12, and 24 weeks, evaluating seizure recurrence, incidence of status epilepticus, cognition, behavior, functional status, ASM acquisition cost, and adverse effects.

RESULTS

A total of 100 children (50 in each group) were enrolled. Within the first week, 5 and 3 children in the phenytoin and levetiracetam groups expired. Up to 1 week or death (whichever occurred earliest), 46 (92 %) and 44 (88 %) children remained seizure-free. Intention-to-treat analysis for both best and worst-case scenarios showed insignificant differences (p=0.52 and 1.0). No children experienced seizure recurrence after 1 week in either group. The number of patients with breakthrough status epilepticus, need for mechanical ventilation, duration of hospital stay, presence of epileptiform abnormalities in repeat electroencephalogram at 12 weeks, functional outcomes at 1, 12, and 24 weeks, as well as cognition and behavioral profiles at 24 weeks, were comparable in both groups (p>0.05 for all). However, the incidence of treatment-emergent adverse events (TEAEs) causally related to study medications was significantly higher in the phenytoin group (p=0.04).

CONCLUSION

Levetiracetam and phenytoin are comparable in efficacy in terms of achieving clinical seizure control in children with acute encephalitis syndrome, although levetiracetam group demonstrated fewer adverse effects.

Slipped capital femoral epiphysis in a 5-year-old boy with cerebral palsy on valproic acid and levetiracetam for epilepsy: a case report

This study presents a rare case of unilateral slipped capital femoral epiphysis treated surgically in a 5-year-old boy with cerebral palsy who was born at 27 weeks' gestation and developed grade III intraventricular haemorrhage and periventricular leucomalacia and was on antiepileptic drugs, including valproic acid and levetiracetam for >3 years. The patient had no history of endocrine, renal, and significant familial diseases.

Unconditioned and conditioned anxiolytic effects of Sodium Valproate on flavor neophobia and fear conditioning

In three experiments with rats, we analyzed the potential anxiolytic effects of sodium valproate, an anticonvulsant drug that has shown additional pharmacodynamic effects in animal models, including anxiolytic action. Since previous results have revealed that injecting valproate before allowing animals to consume a novel flavor solution resulted in an attenuation of neophobia, we predicted a similar effect when the novel flavor is presented on a drug-free trial in the presence of a context previously associated with the drug. In line with this hypothesis, in our first experiment we observed a reduction in neophobia to a novel flavor for those animals tested in the presence of the context associated with Sodium Valproate. However, a control group that received the drug before being allowed access to the novel flavor showed a significant reduction in consumption. Experiment 2 revealed that the unconditioned effects of the drug include a deleterious effect on the animals' locomotor activity that probably interferes with drinking behavior. Finally, in a third experiment, we directly tested the potential anxiolytic properties of sodium valproate by injecting the drug before implementing a fear conditioning procedure. These findings are explained in terms of the unconditioned anxiolytic action of the drug and the formation of an association between the context and the effects of the drug that evokes a conditioned response reminiscent of such anxiolytic effect.

Irritability and its relationship with psychosocial symptoms and quality of life in adolescents with epilepsy receiving levetiracetam therapy: A case-control study

BACKGROUND

Levetiracetam, a widely used anticonvulsant drug in children and adolescents, has been associated with irritability, psychosocial symptoms, and low quality of life, which are also influenced by other epilepsy variables.

PURPOSE

The objective of this study was to investigate the level of treatment-related irritability in adolescents receiving levetiracetam, and to evaluate the relationship between irritability levels and psychosocial symptoms, and quality of life.

METHODS

A cross-sectional, case-control study was conducted. Consecutive adolescent patients with epilepsy aged 11-17 years with partial or generalized seizures, treated with either levetiracetam or valproic acid for at least 6 months, and healthy controls were recruited. The Affective Reactivity Index parent report and self-report, Strengths and Difficulties Questionnaire, and Pediatric Quality of Life Inventory-Psychosocial subscale were utilized to assess irritability, psychosocial symptoms, and functioning.

RESULTS

A total of 120 participants were analyzed; 33 patients in the LEV group, 45 patients in the VPA group, and 42 healthy controls. Both self and parent report irritability levels of the LEV group were found to be significantly higher than those of healthy controls. The irritability levels of the LEV and VPA groups were not statistically different, but still the LEV group had higher irritability levels on both scales. In the LEV group, irritability was positively correlated with behavioral, emotional, and attention/hyperactivity problems, and also negatively correlated with psychosocial quality of life.

CONCLUSION

Adolescents with epilepsy using LEV have a high level of irritability and this is associated with some psychosocial symptoms and poor quality of life.

Vestibular function in children with generalized epilepsy and treated with valproate

BACKGROUND

Studies that evaluated vestibular function with epilepsy are fewer than auditory studies. We assessed vestibular function in children with epilepsy in inter-ictal period.

RESEARCH DESIGN AND METHODS

This cross-sectional study included 35 children with generalized epilepsy (boys=15; girls=20; mean age=11.20±1.21yrs; epilepsy duration=3.54±1.80yrs) and treated with valproate (VPA) and 24 healthy children as controls (mean age=12.42±2.80yrs). Vestibular evaluation was conducted using videonystagmography (VNG) and cervical vestibular evoked myogenic potentials (cVEMPs).

RESULTS

Dizziness was the vestibular symptom in 22.86% of cases. Vestibular dysfunctions (VDs) were found in 65.71%. Manifestations of peripheral VD (65.71%) included unilateral caloric weakness and reduced cVEMPs amplitudes. Manifestations of central VD (28.57%) included oculomotor abnormalities, positional nystagmus with normal calorics, and prolonged cVEMPs latencies. Significant correlations were found between VDs and duration of epilepsy and its treatment [r=-0.368, P=0.01] and VPA dose [r=-0.286, P=0.02] and level [r=-0.355, P=0.01]. Logistic regression analysis showed that duration of epilepsy and its treatment [OR=3.55 (95% CI=2.54-6.50), P=0.001] were independently associated with VDs.

CONCLUSIONS

VDs are common in children with epilepsy. Dizziness was a common symptom. Bilateral peripheral VD was more common than central VD, suggesting an adverse effect of VPA. However, epilepsy cannot be excluded as a cause of central VD.

Cognitive and Behavioral Comorbidities: An Unwanted Effect of Antiepileptic Drugs in Children

Epilepsy is one of the most common neurological disorders and, despite optimally chosen and dosed antiepileptic drugs (AEDs), approximately 20%-30% of patients will continue to have seizures. Behavior and cognition are negatively impacted by seizures, but AEDs are also a major contributor to behavioral and cognitive deficits. However, the cognitive and behavioral effect of AEDs in children is insufficiently emphasized in the literature. This review summarizes the cognitive and behavioral effects of AEDs in the pediatric population with the objective of helping pediatricians and pediatric neurologists to select the AEDs with the best profile for their individual patient's needs.

The importance of assessing behaviour and cognition in antiepileptic drug trials in children and adolescents

It has long been recognised that uncontrolled childhood epilepsy is detrimental to cognition and behaviour, impacting on a patient's ability to succeed academically. Patients who experience more frequent and serious seizures are at greater risk for cognitive decline, emphasising the need for more effective epilepsy treatments to bring seizures under control. That said, although more effective antiepileptic drugs (AEDs) have the potential to limit the impact of uncontrolled seizures on cognitive and behavioural function, recently it has been acknowledged that deficits in these functions may be caused by AEDs themselves. The cognitive and behavioural effects of older-generation AEDs have been determined largely from AE reporting rather than from specific assessment. Recently, clinical trials of newer-generation AEDs, such as topiramate, levetiracetam and perampanel, have included standardised neuropsychological tests as outcome measures to assess their impact on cognition and behaviour in children and adolescents. However, to understand how we may limit the cognitive and behavioural side effects of AEDs, it is necessary for us to gain a fuller, more accurate, characterisation of their true impact. Such insight will depend on sophisticated and standardised approaches to the design of AED clinical trials. This review provides a general overview of our current understanding of the impact of both epilepsy and AEDs on cognition and behaviour, before focusing on the AEDs for which more detailed assessment, using standardised cognitive and behavioural measures, has been undertaken. We will then go on to discuss the key elements in the design of future AED clinical trials to address current unmet needs.

23Na magic-angle spinning and double-rotation NMR study of solid forms of sodium valproate

Sodium valproate is a pharmaceutical with applications in the treatment of epilepsy, bipolar disorder, and other ailments. Sodium valproate can exist in many hydrated and acid-stabilized forms in the solid state, and it can be difficult to obtain precise structural information about many of these. Here, we present a 13C and 23Na solid-state NMR study of several forms of sodium valproate, only one of which has been previously structurally characterized by single-crystal X-ray diffraction. 23Na magic-angle spinning (MAS), double-rotation (DOR), and multiple-quantum magic-angle spinning (MQMAS) NMR spectra are shown to provide useful information on the number of molecules in the asymmetric unit, the local coordination geometry of the sodium cations, and the presence of amorphous phases. Two previously identified forms are shown to be highly similar, or identical, according to the 23Na NMR data. The utility of carrying out both DOR and MQMAS NMR experiments to identify all crystallographically unique sites is demonstrated. 13C cross-polarization MAS NMR spectra also provide complementary information on the number of molecules in the asymmetric unit and the crystallinity of the sample.

Efficacy and safety of intravenous valproate for status epilepticus: a systematic review

INTRODUCTION

The effectiveness of valproate (VPA) in the treatment of focal and generalized epilepsies is well established. The drug has a wide spectrum of action, good tolerability, and has been available as an injectable formulation since 1993. Despite the lack of class A evidence, it has been used extensively in various forms of status epilepticus (SE).

AIM

Our aim was to present a systematic review of data from randomized and non-randomized controlled trials to evaluate the efficacy and safety of intravenous VPA for the treatment of SE.

METHODS

Data sources included MEDLINE, back tracing of references in pertinent studies, and contact with the manufacturer of VPA (Sanofi-Aventis).

RESULTS

Overall, the search strategy yielded 433 results (425 MEDLINE, seven congress abstracts, one unpublished study); after excluding duplicate publications and case reports, 30 studies were identified (the earliest was published in 1993, the most recent in 2012); ten were controlled (six randomized controlled trials, four non-randomized controlled studies), and 20 uncontrolled trials (eight prospective observational studies, 12 retrospective case series). The cumulative literature describes the experiences of 860 patients with various forms of SE treated with intravenous VPA. The overall response rate to abrogate SE was 70.9% (601/848; 95% confidence interval [CI] 67.8-73.9). Response rates to intravenous VPA were better in children than in adults and did not differ between the SE types. The most commonly reported effective doses were between 15 and 45 mg/kg in bolus (6 mg/kg/min) followed by 1-3 mg/kg/h infusion. Safety studies of intravenous VPA administration in patients with SE showed a low incidence of adverse events overall (<10%), mainly dizziness, thrombocytopenia, and mild hypotension, which was independent of infusion rates. Of note, good cardiovascular and respiratory tolerability was observed in these studies, even at high doses and fast infusion rates (up to 30 mg/kg at 10 mg/kg/min), despite multiple morbidities or other antiepileptic drugs. The most serious concern relates to the possibility of acute encephalopathy, sometimes related to hepatic abnormalities or hyperammonemia.

CONCLUSIONS

The published experience is consistent with VPA being a safe and effective therapeutic option for patients with established SE who have previously failed conventional first-line treatment with benzodiazepines, but high-quality randomized controlled trials are needed to inform clinicians on its comparative effectiveness in SE.

Pattern of adverse events of antiepileptic drugs: results of the aESCAPE study in Poland

INTRODUCTION

The Adverse Event Scale in Patients With Epilepsy (aESCAPE) European study (NCT00394927) explored and analyzed adverse events (AEs) and reasons for modifying treatment in patients treated with newer and older antiepileptic drugs (AEDs) used in monotherapy or polytherapy. The present analysis concerns the results of patients recruited in Poland.

MATERIAL AND METHODS

Multicentre, international, observational, cross-sectional study investigating AEs in patients with epilepsy (aged ≥ 4 years), on stable AED treatment with one or two AED(s) for ≥ 3 months, using standardized questionnaires completed by a physician during a single study visit.

RESULTS

Out of 309 patients, 24.6% were treated exclusively with newer AED(s) in monotherapy or in combination, while 75.4% were treated with older AED(s) or a combination of older and newer AED(s). 60.8% were on monotherapy, and 39.9% on polytherapy. In general, 73.8% of patients reported ≥ 1 AE(s). There were no significant differences in the frequency of reported AEs in compared groups. The most common were disturbances in cognitive function (40.5%), psychological problems (36.2%), and sedation (32.7%). Some AEs were found to be more specific for particular types and treatment regimens. Changes in treatment or dose during the study visit occurred in 22.3% of the patients, mainly due to lack of efficacy (10.7%), AEs (5.2%) or absence of seizures (4.5%).

CONCLUSIONS

A detailed structured interview revealed high frequency of AEs in patients treated with AEDs. The main reasons for treatment modifications at the study visit were lack of efficacy, adverse events and absence of seizures.

Metabolic and endocrine effects of valproic acid chronic treatment

Treatment of epileptic patients with valproic acid (VPA) may be associated with substantial weight changes that may increase morbidity and impair adherence to the treatment regimen. VPA-induced weight gain seems to be associated with many metabolic disturbances; the most frequent are hyperinsulinemia and insulin resistance, hyperleptinemia and leptin resistance. Patients who gain weight during VPA therapy can develop dyslipidemia and metabolic syndrome that are associated with long-term vascular complications such as hypertension and atherosclerosis. Moreover, an elevation in the levels of uric acid and homocysteine, together with oxidative stress, may contribute to atherosclerotic risk in patients under long-term therapy with VPA. The aim of this review is to discuss the metabolic and endocrine effects of VPA chronic treatment in patients with epilepsy.

HDAC inhibitors dysregulate neural stem cell activity in the postnatal mouse brain

The mammalian central nervous system (CNS) undergoes significant expansion postnatally, producing astrocytes, oligodendrocytes and inhibitory neurons to modulate the activity of neural circuits. This is coincident in humans with the emergence of pediatric epilepsy, a condition commonly treated with valproate/valproic acid (VPA), a potent inhibitor of histone deacetylases (HDACs). The sequential activity of specific HDACs, however, may be essential for the differentiation of distinct subpopulations of neurons and glia. Here, we show that different subsets of CNS neural stem cells (NSCs) and progenitors switch expression of HDAC1 and HDAC2 as they commit to a neurogenic lineage in the subventricular zone (SVZ) and dentate gyrus (DG). The administration of VPA for only one week from P7-P14, combined with sequential injections of thymidine analogs reveals that VPA stimulates a significant and differential decrease in the production and differentiation of progeny of NSCs in the DG, rostral migratory stream (RMS), and olfactory bulb (OB). Cross-fostering VPA-treated mice revealed, however, that a postnatal failure to thrive induced by VPA treatment had a greater effect on DG neurogenesis than VPA action directly. By one month after VPA, OB interneuron genesis was significantly and differentially reduced in both periglomerular and granule neurons. Using neurosphere assays to test if VPA directly regulates NSC activity, we found that short term treatment with VPA in vivo reduced neurosphere numbers and size, a phenotype that was also obtained in neurospheres from control mice treated with VPA and an alternative HDAC inhibitor, Trichostatin A (TSA) at 0 and 3 days in vitro (DIV). Collectively, these data show that clinically used HDAC inhibitors like VPA and TSA can perturb postnatal neurogenesis; and their use should be carefully considered, especially in individuals whose brains are actively undergoing key postnatal time windows of development.

Gender differences in risk-taking behaviour in youth with epilepsy: a Norwegian population-based study

OBJECTIVES

It is well known that behavioural problems and psychiatric disorders occur with greater prevalence in children and adolescents with epilepsy. Youth with epilepsy (YWE) may also be more susceptible to risk-taking behaviour, but this has seldom been studied. The aim of this study was to explore risk-taking behaviour in YWE.

MATERIAL AND METHODS

In this study, 19,995 young people (age range: 13-19 years) participated and completed an extensive questionnaire, including The Strengths and Difficulties Questionnaire self-report. A variable, risk-taking behaviour, was identified, including daily consumption of alcohol, substance abuse or having committed a criminal offence such as being in a fight with a weapon, committing a burglary or using threats to obtain money.

RESULTS

Two hundred and forty-seven youths reported currently having, or having had, epilepsy (lifetime prevalence: 1.2%). Of these, 8.3% reported daily alcohol consumption (1.0% in controls; P<0.001), 12.4% had tried illegal substances (5.5% of controls; P<0.001), and 19.7% had committed criminal offences (8.5% in controls; P<0.001). A gender difference was found: girls with epilepsy did not exhibit risk-taking behaviour more frequently than controls, but having epilepsy was a risk factor for such behaviour in boys (OR: 3.2).

CONCLUSION

Boys with epilepsy exhibit risk-taking behaviour more frequently than controls. Other risk factors for this behaviour were living with a single parent, low family income and psychiatric symptoms. This behavioural association should be addressed as it probably contributes to the negative social outcomes that frequently occur in the adult epilepsy population.

Pharmacokinetics and clinical application of intravenous valproate in Thai epileptic children

Roles of intravenous administration of valproate in status epilepticus and serial seizures are documented in adults and children. Pharmacokinetic parameters are necessary to predict the optimum therapeutic level after administration. A cross-sectional study to determine the pharmacokinetic parameters and safety of intravenous valproate for future application was conducted in Thai children from January to December 2008. There were eleven children, age-range 1-15 years (mean age 9.5 years) enrolled. Valproate of 15-20 mg/kg was administrated intravenously at the rate of 3 mg/kg/min, followed by 6 mg/kg every 6 h. Valproate level was determined prior to the initial dose and at ½, 1, 2, 4, 5, and 6 h postdose. Complete blood count, serum ammonia, and liver function tests were collected prior to the initial dose and at 6 h. Median loading dose was 19 mg/kg (range 15-20.5 mg/kg). Median maximum concentration at 30 min after infusion was 98.8 mcg/mL (range 67-161 mcg/mL). Median volume of distribution was 0.20 L/kg (range 0.15-0.53 L/kg). Median half-life was 9.5 h (range 4.4-24.2 h). Median clearance was 0.02 L/h/kg (range 0.01-0.05 L/h/kg). Six hours after initial dose, eight children did not have recurrent seizure. One child had brief seizure at 20 min after initial dose. Seizure recurred in two children at 4th and 5th hour. Asymptomatic transient elevation of serum ammonia was observed in two children. Volume of distribution of 0.20 L/kg could be applied for initial intravenous administration with a favorable efficacy.

Identifying genomic and developmental causes of adverse drug reactions in children

Adverse drug reactions are a concern for all clinicians who utilize medications to treat adults and children; however, the frequency of adult and pediatric adverse drug reactions is likely to be under-reported. In this age of genomics and personalized medicine, identifying genetic variation that results in differences in drug biotransformation and response has contributed to significant advances in the utilization of several commonly used medications in adults. In order to better understand the variability of drug response in children however, we must not only consider differences in genotype, but also variation in gene expression during growth and development, namely ontogeny. In this article, recommendations for systematically approaching pharmacogenomic studies in children are discussed, and several examples of studies that investigate the genomic and developmental contribution to adverse drug reactions in children are reviewed.

Dysfunction of executive and related processes in childhood absence epilepsy

The nature and extent of the neuropsychological difficulties associated with childhood absence epilepsy (CAE) remain unclear. Because aberrant thalamocortical rhythms have been implicated in the pathogenesis of CAE, it was hypothesized that children with CAE would show greater difficulties in neuropsychological domains that are thought to be subserved by basal ganglia-thalamocortical circuits. Multivariate analysis of variance was used to compare the neuropsychological functioning of 16 children with CAE with that of 14 children with type 1 diabetes mellitus and 15 healthy children. The CAE group did not perform differently from the other groups on measures of intellectual functioning, memory, academic achievement, fine motor speed, or processing speed. In contrast, significant differences were found in problem solving, letter fluency, complex motor control, attention/behavioral inhibition, and psychosocial functioning. These results suggest that children with CAE show difficulties in neuropsychological functions thought to be subserved by the same regions implicated in the pathogenesis of the disorder.

Supporting the recommended paediatric dosing regimen for rufinamide in Lennox-Gastaut syndrome using clinical trial simulation

Rufinamide was approved for the treatment of seizures associated with Lennox-Gastaut syndrome (LGS) as adjunctive therapy in patients aged 4 years and older. Rufinamide pharmacokinetics (PK) has been established on pooled data from several clinical studies in epilepsy, including one in LGS patients. Demographic covariates and drug-drug interactions with several antiepileptic drugs have been explored using population PK modelling. Two types of drug-drug interactions models were developed and compared. The PK analysis demonstrated that the coadministration of valproate decreases rufinamide clearance, requiring potential dose adjustment. To explore rufinamide exposure under different dosing regimens in LGS patients, clinical trial simulations were performed. The objective of the simulations was to select the doses giving an exposure shown to be safe and efficacious in larger populations. The concentrations simulated in a subgroup of patients with body weight less than 30 kg presented a larger inter-individual variability than in other patients. Additional simulations demonstrated that this increased variability was due partly to greater valproate concentrations in some of the children treated with rufinamide. Simulations of the rufinamide exposure under different maximum daily dose in presence and in absence of valproate co-administration were used to establish the dosing recommendation. The simulations support the proposal of a lower maximum daily rufinamide dose for patients under 30 kg receiving both drugs: the dose of 600 mg/day was proposed as a maximum daily dose in children also receiving valproate concomitantly, whereas in absence of valproate, the maximum daily dose is 1000 mg/day.

Conversion from valproic acid onto topiramate in adolescents and adults with epilepsy

OBJECTIVE

To explore efficacy and tolerability outcomes of topiramate (TPM) in patients with epilepsy transitioning from valproic acid (VPA) because of insufficient efficacy and/or tolerability onto TPM.

METHODS

Multicenter, open label, single arm, non-interventional study examining patients (> or =12 years) with epilepsy, transitioning onto TPM from baseline mono-or combination therapy with VPA. TPM was added onto the existing antiepileptic drug (AED) treatment and started at a dose of 25 mg once daily. The dose was titrated up with 25 mg/day increments, once every 1-2 weeks, until a final dose between 50-200 mg/day was reached. Based on clinical judgment, the treating physician decided whether or not and when the existing AED treatment especially with VPA could be withdrawn. Documented were type and frequency of seizures, TPM dose, quality of life (QOLIE-10 questionnaire), subjective perception of improvement, and adverse events (AE).

RESULTS

One hundred and forty-seven patients (59% women, mean age 41 years) switched from baseline VPA treatment onto TPM because of insufficient efficacy (61%) and/or poor tolerability (81%). Average duration of follow-up was 20.3 weeks with an overall discontinuation rate of 16.3% of patients, mainly because of AE (in 8.2% of 147 patients). At study endpoint, the intended shift to TPM monotherapy was achieved in 70% of patients at a median dose of 150 mg/day. A seizure reduction of > or =50% was achieved in 75% of patients in the last scheduled period (week 8-20), and 51% of patients entering that period remained seizure-free. Quality of life improved significantly as compared with baseline for all domains of QOLIE-10 (P < 0.001). Most frequent AEs were weight decrease (4.8%), paraesthesia and fatigue (4.1% each), speech disorder and headaches (2.7% each).

CONCLUSIONS

In patients with epilepsy not satisfactorily treated with VPA, conversion to TPM was associated with improved seizure control as well as improvement in several aspects of quality of life.

Oral valproic acid for epilepsy--long-term experience in therapy and side effects

Valproic acid (VPA) is considered to be a drug of first choice and one of the most frequently-prescribed antiepileptic drugs worldwide for the therapy of generalized and focal epilepsies, including special epileptic. It is a broad-spectrum antiepileptic drug and is usually well tolerated. Rarely, serious complications may occur in some patients, including hemorrhagic pancreatitis, coagulopathies, bone marrow suppression, VPA-induced hepatotoxicity and encephalopathy, but there is still a lack of knowledge about the incidence and occurrence of these special side effects. Additionally, the consequences for VPA therapy and indication are more or less unclear. By literature review and own data this review addresses some of the challenges of VPA therapy and its side effects, which are not unique to epilepsy in childhood.

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.

Safety of rapid intravenous valproate infusion in pediatric patients

In order to investigate the safety of rapidly infused intravenous valproate in children with seizures, the drug was administered to 18 patients (age range, 1-16 years) at doses ranging from 7.5 to 41.5 mg/kg and rates of 1.5 to 11 mg/kg per minute. Forty-eight intravenous valproate doses were administered during 19 hospital admissions (range, 1-16 doses per admission). Only one adverse event was reported; a 9-year-old male experienced burning at the infusion site while receiving 660 mg intravenous valproate at 6 mg/kg per minute. The patient tolerated three subsequent infusions (one of 330 mg and two of 165 mg) at the same rate with no further discomfort. Electrocardiogram results, available for 18 admissions, revealed no arrhythmias, bradycardias, or hypotensive episodes. No abnormal laboratory results were reported. Rapid intravenous valproate infusion appears to be safe in pediatric patients.