Oxcarbazepine in the treatment of epilepsy

Population pharmacokinetics of oxcarbazepine active metabolite in Chinese children with epilepsy

Oxcarbazepine (OXC) is an antiepileptic drug whose efficacy is largely attributed to its monohydroxy derivative metabolite (MHD). Nevertheless, there exists significant inter-individual variability in both the pharmacokinetics and therapeutic response of this drug. The objective of this study is to explore the impact of patients' characteristics and genetic variants on MHD clearance in a population pharmacokinetic (PPK) model of Chinese pediatric patients with epilepsy. The PPK model was developed using a nonlinear mixed effects modeling method based on 231 MHD plasma concentrations obtained from 185 children with epilepsy. The one-compartment model and combined residual model were established to describe the pharmacokinetics of MHD. Forward addition and backward elimination were employed to evaluate the impact of covariates on the model parameters. The model was evaluated using goodness-of-fit, bootstrap, visual predictive checks, and normalized prediction distribution errors. In the two final PPK models, age, estimated glomerular filtration rate (eGFR), and a combined genotype of six variants (rs1045642, rs2032582, rs7668282, rs2396185, rs2304016, rs1128503) were found to significantly reduce inter-individual variability for MHD clearance. The inter-individual clearance equals to 1.38 × (Age/4.74)0.29 × (eGFR/128.66)0.25 × eθABCB-UGT-SCN-INSR for genetic variants included model and 1.30 × (Age/4.74)0.30 × (eGFR/128.66)0.23 for model without genetic variants. The precision of all parameters was deemed acceptable, and the model exhibited good predictability while remaining stable and effective.    Conclusion: Age, eGFR, and genotype may play a significant role in MHD clearance in children with epilepsy. The developed PPK models hold potential utility in facilitating oxcarbazepine dose adjustment in pediatric patients. What is Known: • The adjustment of the oxcarbazepine regimen remains difficult due to the considerable inter- and intra-individual variability of oxcarbazepine pharmacokinetics. • Body weight and co-administration with enzyme-inducing antiepileptic drugs emerge as the most influential factors contributing to the pharmacokinetics of MHD. What is New: • A positive correlation was observed between eGFR and the clearance of MHD in pediatric patients with epilepsy. • We explored the influence of genetic polymorphisms on MHD clearance and identified a combined genotype (ABCB-UGT-SCN-INSR) that exhibited a significant association with MHD concentration.

Iron-Catalyzed Wacker-type Oxidation of Olefins at Room Temperature with 1,3-Diketones or Neocuproine as Ligands*

Herein, we describe a convenient and general method for the oxidation of olefins to ketones using either tris(dibenzoylmethanato)iron(III) [Fe(dbm)₃ ] or a combination of iron(II) chloride and neocuproine (2,9-dimethyl-1,10-phenanthroline) as catalysts and phenylsilane (PhSiH₃ ) as additive. All reactions proceed efficiently at room temperature using air as sole oxidant. This transformation has been applied to a variety of substrates, is operationally simple, proceeds under mild reaction conditions, and shows a high functional-group tolerance. The ketones are formed smoothly in up to 97 % yield and with 100 % regioselectivity, while the corresponding alcohols were observed as by-products. Labeling experiments showed that an incorporated hydrogen atom originates from the phenylsilane. The oxygen atom of the ketone as well as of the alcohol derives from the ambient atmosphere.

Population pharmacokinetic model development and its relationship with adverse events of oxcarbazepine in adult patients with epilepsy

This study aimed to develop a pharmacokinetic (PK) model of oxcarbazepine (OXC) and analyse the relationship between monohydroxylated derivative (MHD), an active metabolite of OXC, and the adverse events of OXC. We obtained 711 OXC samples from 618 patients with epilepsy who were enrolled in the Epilepsy Registry Cohort of Seoul National University Hospital from February 2011 to January 2014. The plasma PK model was developed using a nonlinear mixed-effect modelling method with NONMEM (ver 7.3). A one-compartment model with a first-order absorption model and proportional residual error adequately described the MHD concentration–time profiles. The only covariate incorporated for CL/F and V/F was body weight. Of the 447 patients analysed, 28 (6.26%) had dose-related adverse events (DRAEs), which were dizziness, somnolence, headache, and diplopia. For DRAE occurrence, the cut-off values of the MHD trough and AUC were 12.27 mg/L (specificity 0.570, sensitivity 0.643) and 698.5 mg h/L (specificity, sensitivity 0.571), respectively. Multivariate analysis showed the sole dizziness symptom was significantly associated with both the MHD trough and the AUC (p = 0.013, p = 0.038, respectively). We newly developed a population PK model using sparse sampling data from patients with epilepsy, and the model better reflects the actual clinical situation.

Cenobamate tablets as a treatment for focal-onset seizures in adults

Introduction: Despite the introduction of numerous new antiseizure medications (ASMs) still about one-third of epilepsies remain drug-resistant. Therefore, new compounds with advanced efficacy are urgently needed. Cenobamate (CNB) is a new ASM that has been recently introduced in the United States for the treatment of adults with focal-onset seizures. The approval in Europe is under way.Areas covered: This review covers the pharmacological profile of CNB, the proof-of-concept trial, the two double-blind, placebo-controlled phase 2 trials investigating adjunct CNB in adults with focal-onset seizures, one open-label safety trial, and a variety of published abstract material that provided additional post hoc data.Expert opinion: In two placebo-controlled randomized multicenter phase 2 trials adjunct CNB showed unusually high efficacy with rates of seizure-free people with epilepsy (PWE) partially beyond 20%. However, during the clinical program cases of drug-related reactions with eosinophilia and systemic symptoms (DRESS syndrome) occurred. Therefore, an open-label safety study was performed in more than 1300 PWE with particularly slower titration schedules which did not add more cases with similar reactions. Taking into consideration the promising efficacy and the safety experience from the open-label trial, CNB applied according to the meanwhile recommended titration strategy, might offer a new prospect.

Prenatal exposure to oxcarbazepine increases hippocampal apoptosis in rat offspring

This study assessed apoptosis in the offspring of rats exposed to oxcarbazepine (OXC) from day 7 to 15 of gestation. Three groups of pregnant Wistar rats were used: 1) Control, treated with saline solution; 2) treated with 100 mg/kg OXC; 3) treated with 100 mg/kg of carbamazepine (CBZ, as a positive control for apoptosis); the route of administration was intragastric. Apoptosis was detected at three postnatal ages using the TUNEL technique in the CA1, and CA3 regions of the hippocampus and in the dentate gyrus (DG); neurogenesis was assessed in the DG using an antibody against doublecortin. The litter characteristics were recorded. OXC increased apoptosis in all regions (p < 0.01) at the three ages evaluated. Lamination disruption occurred in CA1 and CA3 due to the neuron absence and to ectopic neurons; there were also malformations in the dorsal lamina of the DG in 38% and 25% of the pups born from rats treated with OXC and CBZ respectively. CBZ also increased apoptosis. No clear effect on neurogenesis in the DG was observed. The size of the litter was smaller (p < 0.01) in the experimental groups. Nineteen-day OXC fetuses had low weight (p < 0.01), but 21 and 30 postnatal days old CBZ and OXC pups were overweight (p < 0.01). The results demonstrate that OXC administered during gestation is pro-apoptotic, alters the cytoarchitecture of the hippocampus, reduces litter size, and probably influences postnatal weight. We provide evidence of the proapoptotic effect of CBZ when administered early in gestation.

Epilepsy Disease and Nose-to-Brain Delivery of Polymeric Nanoparticles: An Overview

Epilepsy is the fourth most common global neurological problem, which can be considered a spectrum disorder because of its various causes, seizure types, its ability to vary in severity and the impact from person to person, as well as its range of co-existing conditions. The approaches to drug therapy of epilepsy are directed at the control of symptoms by chronic administration of antiepileptic drugs (AEDs). These AEDs are administered orally or intravenously but alternative routes of administration are needed to overcome some important limits. Intranasal (IN) administration represents an attractive route because it is possible to reach the brain bypassing the blood brain barrier while the drug avoids first-pass metabolism. It is possible to obtain an increase in patient compliance for the easy and non-invasive route of administration. This route, however, has some drawbacks such as mucociliary clearance and the small volume that can be administered, in fact, only drugs that are efficacious at low doses can be considered. The drug also needs excellent aqueous solubility or must be able to be formulated using solubilizing agents. The use of nanomedicine formulations able to encapsulate active molecules represents a good strategy to overcome several limitations of this route and of conventional drugs. The aim of this review is to discuss the innovative application of nanomedicine for epilepsy treatment using nose-to-brain delivery with particular attention focused on polymeric nanoparticles to load drugs.

Comparison of oxcarbazepine efficacy and MHD concentrations relative to age and BMI: Associations among ABCB1, ABCC2, UGT2B7, and SCN2A polymorphisms

Genetic polymorphisms are related to the concentration and efficacy of oxcarbazepine (OXC). 10-Hydroxycarbazepine (MHD) is the major pharmacologically active metabolite of OXC, and it exerts an antiepileptic effect. This study aimed to explore the connection between the MHD concentration and genes such as ATP-binding cassette B1 (ABCB1), ATP-binding cassette C2 (ABCC2), UDP-glucuronosyltransferase-2B7 and sodium voltage-gated channel alpha subunit 2 (SCN2A), which participate in the antiepileptic function of OXC.Total 218 Chinese epileptic patients, were stratified into different groups according to their age, body mass index (BMI) and OXC efficacy. The genotypes of 7 single nucleotide polymorphisms in all subjects were determined by polymerase chain reaction-improved multiple ligase detection reaction assay. The MHD plasma concentration was detected by high-performance liquid chromatography and then standardized through dosage and body weight.In general, the ABCC2 rs2273697 mutant (P = .026) required a significantly higher standardized MHD concentration. For age groups, carriers of the ABCC2 rs2273697 mutant showed a significantly higher standardized MHD concentration than noncarriers in the juvenile group (P = .033). In terms of BMI, a significantly higher standardized MHD concentration was found in the ABCB1 rs2032582 mutant of the normal weight group (P = .026). The SCN2A rs17183814 mutant required a significantly higher OXC maintenance (P = .014) in the low-weight group, while lower OXC maintenance dose (P = .044) and higher standardized MHD concentration (P = .007) in the overweight group.The ABCC2 rs2273697 polymorphism was significantly associated with MHD plasma concentration in the whole patient cohort and in patients stratified by different ages, this finding provides potential theoretical guidance for the rational and safe clinical use of OXC.

Patient Survival After Acute Voluntary Poisoning With a Huge Dose of Oxcarbazepine and Olanzapine

INTRODUCTION

Oxcarbazepine is a carbamazepine pre-drug with less drug interactions. Its adverse effects, including hyponatremia, somnolence and ataxia, are dose dependent. Olanzapine is an atypical antipsychotic drug most commonly used to manage psychoses and symptoms of irritability and aggressive behavior. Main side effects include extrapyramidal and anticholinergic symptoms, weight gain, and hyperglycemia.

CASE REPORT

In this manuscript a case of oxcarbazepine and olanzapine intoxication is discussed. A 45-year-old woman, previously diagnosed with bipolar disorder and chronic alcoholism, was presented two hours after ingestion of 30,000mg of oxcarbazepine and 140 mg of olanzapine, combined with alcohol. She was immediately treated with gastric lavage and administration of activated charcoal. During her hospitalization she was hemodynamically and respiratory stable with no neurological signs and symptoms except for somnolence. Another side effect was hyponatremia. She was discharged from our department in stable clinical condition after being evaluated by a psychiatrist.

CONCLUSION

Early approach is crucial for the management of drug intoxication. Late symptoms can be avoided through close monitoring of vital signs, mental status and laboratory values. Psychiatric consultation is essential for a better long-term outcome.

Development and validation of a reversed-phase HPLC method for licarbazepine monitoring in serum of patients under oxcarbazepine treatment

Licarbazepine is the pharmacologically active metabolite of oxcarbazepine, a drug indicated for the treatment of partial seizures and bipolar disorders. Several HPLC methods have been developed thus far but there is lack of control for interferences from antipsychotic drugs. The aim of the present study was to develop a simple, low-cost and reliable HPLC-UV method for the determination of licarbazepine in human serum in the presence of co-administered antiepileptic, antipsychotic and commonly prescribed drugs. Sample preparation consisted of a single protein precipitation step with methanol. Separation lasted ~9 min on a reversed-phase C₁₈ column using a mobile phase composed of 50 mm sodium-dihydrogen-phosphate-monohydrate/acetonitrile (70:30, v/v) delivered isocratically at 0.9 mL/min and 30°C. Wavelength was 210 nm and calibration curve was linear with r² 0.998 over the range 0.2-50.0 μg/mL. Coefficient of variation was <5.03% and bias <-4.92%. Recovery ranged from 99.49 to 104.52% and the limit of detection was 0.0182 μg/mL. No interferences from the matrix or from antiepileptic, antipsychotic and commonly prescribed drugs were observed. The method was applied to serum samples of patients under oxcarbazepine treatment and proved to be a useful tool for the therapeutic drug monitoring of licarbazepine during monotherapy or adjunctive treatment of seizures or affective disorders.

Newer anti-epileptic drugs

NEED AND PURPOSE OF REVIEW

A number of newer anti-epileptic drugs have been developed in the last few years to improve the treatment outcomes in epilepsy. In this review, we discuss the use of newer anti-epileptic drugs in children.

METHODS USED FOR LOCATING, SELECTING, EXTRACTING AND SYNTHESIZING DATA

MEDLINE search (1966-2013) was performed using terms newer anti-epileptic drugs, Oxcarbazepine, vigabatrin, topiramate, zonisamide, levetiracetam, lacosamide, rufinamide, stiripentol, retigabine, eslicarbazepine, brivaracetam, ganaxolone and perampanel for reports on use in children. Review articles, practice parameters, guidelines, systematic reviews, meta-analyses, randomized controlled trials, cohort studies, and case series were included. The main data extracted included indications, efficacy and adverse effects in children.

MAIN CONCLUSIONS

Oxcarbazepine is established as effective initial monotherapy for children with partial-onset seizures. Vigabatrin is the drug of choice for infantile spasms associated with tuberous sclerosis. Lamotrigine, levetiracetam and lacosamide are good add-on drugs for patients with partial seizures. Lamotrigine may be considered as monotherapy in adolescent females with idiopathic generalized epilepsy. Levetiracetam is a good option as monotherapy for females with juvenile myoclonic epilepsy. Topiramate is a good add-on drug in patients with epileptic encephalopathies such as Lennox-Gastaut syndrome and myoclonic astatic epilepsy.

The safety and tolerability of newer antiepileptic drugs in children and adolescents

Childhood epilepsy continues to be intractable in more than 25% of patients diagnosed with epilepsy. The introduction of new anti-epileptic drugs (AEDs) provides more options for treatment of children with epilepsy. We review the safety and tolerability of seven new AEDs (levetiracetam, lamotrigine, oxcarbazepine, rufinamide, topiramate, vigabatrin and zonisamide) focusing on their side effect profiles and safety in children and adolescents. Many considerations that are specific for children such as the impact of AEDs on the developing brain are not addressed during the development of new AEDs. They are usually approved as adjunctive therapies based upon clinical trials involving adult patients with partial epilepsy. However, 2 of the AEDs reviewed here (rufinamide and vigabatrin) have FDA approval in the U.S. for specific Pediatric epilepsy syndromes, which are discussed below. The Pediatrician or Neurologists decision on the use of a new AED is an evolutionary process largely dependent on the patient characteristics, personal/peer experiences and literature about efficacy and safety profiles of these medications. Evidence based guidelines are limited due to a lack of randomized controlled trials involving pediatric patients for many of these new AEDs.

Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring

Epilepsy is a chronic disease occurring in approximately 1.0% of the world's population. About 30% of the epileptic patients treated with availably antiepileptic drugs (AEDs) continue to have seizures and are considered therapy-resistant or refractory patients. The ultimate goal for the use of AEDs is complete cessation of seizures without side effects. Because of a narrow therapeutic index of AEDs, a complete understanding of its clinical pharmacokinetics is essential for understanding of the pharmacodynamics of these drugs. These drug concentrations in biological fluids serve as surrogate markers and can be used to guide or target drug dosing. Because early studies demonstrated clinical and/or electroencephalographic correlations with serum concentrations of several AEDs, It has been almost 50 years since clinicians started using plasma concentrations of AEDs to optimize pharmacotherapy in patients with epilepsy. Therefore, validated analytical method for concentrations of AEDs in biological fluids is a necessity in order to explore pharmacokinetics, bioequivalence and TDM in various clinical situations. There are hundreds of published articles on the analysis of specific AEDs by a wide variety of analytical methods in biological samples have appears over the past decade. This review intends to provide an updated, concise overview on the modern method development for monitoring AEDs for pharmacokinetic studies, bioequivalence and therapeutic drug monitoring.

The safety and tolerability of newer antiepileptic drugs in children and adolescents

The newer antiepileptic drugs (AEDs) provide more therapeutic options and overall improved safety and tolerability for patients. To provide the best care, physicians must be familiar with the latest tolerability and safety data. This is particularly true in children, given there are relatively fewer studies examining the effects of AEDs in children compared with adults. Since we now have significant paediatric literature on each of these agents, we provide a comprehensive and current literature review of the newer AEDs, focusing on safety and tolerability data in children and adolescents. Because the safety profiles in children differ from those in adults, familiarity with this literature is important for child neurologists and other paediatric caregivers. We have organized the data by organ system for each AED for easier reference.

New antiepileptic drugs in pediatric epilepsy

New antiepileptic drugs (AEDs), introduced since 1993, provide more diverse options in the treatment of epilepsy. Despite the equivalent efficacy and better tolerability of these drugs, more than 25% of patients remain refractory to treatment. Moreover, the issues for pediatric patients are different from those for adults, and have not been addressed in the development and application of the new AEDs. Recently published evidence-based treatment guidelines have helped physicians to choose the most reasonable AED, although they cannot fully endorse new AEDs because of the lack of well-designed, randomized controlled trials. We review the mechanisms of action, pharmacokinetic properties, adverse reactions, efficacy, and tolerability of eight new AEDs (felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, vigabatrin, and zonisamide), focusing on currently available treatment guidelines and expert opinions regarding pediatric epilepsy.

New developments for the pharmacological treatment of alcohol withdrawal syndrome. A focus on non-benzodiazepine GABAergic medications

Alcohol withdrawal syndrome (AWS) can be a life-threatening condition affecting some alcohol-dependent patients who abruptly discontinue or decrease their alcohol consumption. The main objectives of the clinical management of AWS include: to decrease the severity of symptoms, prevent more severe withdrawal clinical manifestations and facilitate entry of the patient into a treatment program in order to attempt to achieve and maintain long-term abstinence from alcohol. At present, benzodiazepines represent the drugs of choice in the treatment of AWS. However, in line with the possible side effects and addictive properties related to benzodiazepine use, there is growing evidence to suggest that non-benzodiazepine GABAergic compounds represent promising medications in the treatment of alcohol-dependent patients. This review focuses on research into non-benzodiazepine GABAergic medications for the treatment of AWS. Among them, carbamazepine, gabapentin and valproic acid are the most studied. The studies on carbamazepine seem to be the most compelling. Preliminary data have also suggested the possible utility of baclofen and topiramate, although further evidence is needed. The promising results in terms of both safety and efficacy are reported. However, we also note the need of more methodologically controlled studies on a greater number of patients, involving more complicated forms of AWS.

Oxcarbazepine for the treatment of binge eating disorder: a case series

We present a case series of nine obese outpatients with a diagnosis of binge eating disorder who were treated with a flexible dose of the anticonvulsant oxcarbazepine. The drug has not previously been used to treat this disorder. Five patients dropped out at various points of the study, giving only fragmented data. Where data were available, all patients reported side effects (n=7) and some showed a reduction (n=4) or no change (n=3) in binge episode frequency. Some patients lost weight over the study period (n=3; range, 3-5 kg); others showed no change (n=2) or an increase in weight (n=3; range, 1.8-2.9 kg). Our results were inconsistent, but the drug was effective for some patients who showed marked impulsivity in eating behaviours and depressive symptoms.

Metabolic effects of AEDs: impact on body weight, lipids and glucose metabolism

Epilepsy is a chronic disorder often requiring years of treatment. Accordingly, adverse effects of epilepsy and its treatment can impact general health for many decades. The psychological consequences of epilepsy are well documented, although the metabolic consequences of the treatment of epilepsy have only recently received attention. Antiepileptic drugs (AEDs) are well known to alter weight, causing either weight gain or weight loss. The mechanism by which this occurs remains to be fully understood, although there appears to be an effect on lipid and glucose metabolism. This chapter examines current data available on the adverse effects of individual AEDs on somatic weight, serum lipid profile, and glucose metabolism. These issues are of importance to neurologists caring for patients with epilepsy.

Simultaneous quantitative analysis of oxcarbazepine and 10,11-dihydro-10-hydroxycarbamazepine in human plasma by liquid chromatography–electrospray tandem mass spectrometry

A fast and sensitive method to quantify oxcarbazepine (OXC) and its active metabolite, 10,11-dihydro-10-hydroxycarbamazepine (MHD) in human plasma using HPLC-MS/MS has been developed. The method involved liquid-liquid extraction (LLE), with diethyl ether-diclhoromethane (60:40v/v) using deuterade carbamazepine (d10-carbamazepine) as internal standard (IS). The analytes and IS were separated using an isocratic mobile phase (acetonitrile/water (50:50v/v)+20 mM acetic acid) on the analytical column Phenomenex Luna C18 5 microm (150 mm x 4.6 mm) at room temperature. Detection was performed by a Micromass Quatro LC mass spectrometer in the reaction monitoring mode using positive electrospray ionization (ESI+). The MS-MS ion transition monitored were m/z 253>208 for OXC, m/z 255>194 for MHD and m/z 247>204 for IS. Over the range 20-5250 ng/ml for OXC and 40-10,500 ng/ml for MHD, the calibration curves were defined by the following equations: y = 0.00568 + 0.00296x -5.70e - 8x(2) and y = 0.00749 + 0.00178x - 5.70e - 8x(2) for OXC and MHD, respectively. All coefficient of determination (r(2)) were close to unity (0.9986-0.9994). The lower limits of quantification obtained as a result of the LLE procedure was 20 ng/ml for OXC and 40 ng/ml for MHD. The statistical evaluation of the developed method was conducted by examining within-batch and between-batch precision data, which were within the required limits. The suitability of the assay for pharmacokinetics studies was determined by measuring OXC and MHD concentration after administration of a single 10 ml of OXC oral suspension (6%) in plasma human of healthy volunteers.

Uncontrolled headache induced by oxcarbazepine

Headache induced by acute exposure to a specific drug constitutes an idiosyncratic side effect. Metabolic imbalance appears as the leading aetiology, among several other hypotheses. Either primary headaches show a higher susceptibility to this idiosyncratic reaction or a drug-induced primary headache evolves in intensity and duration, becoming uncontrolled until the complete discontinuation of the drug in consideration. The goal of this study is to describe three patients diagnosed with migraine and epilepsy (both under control) who evolved into status migrainosus after the introduction of oxcarbazepine (OXC), as part of a switch off from carbamazepine (CBZ). Twenty-four to seventy-two hours following the switch, all patients developed intractable headache, despite the use of different symptomatic drugs. Complete recovery of the headache symptoms occurred only after OXC was discontinued. We discuss the potential mechanisms associated to OXC and status migrainosus, drug-induced headaches and uncontrolled headaches.

Parent drug and/or metabolite? Which of them is most appropriate to establish bioequivalence of two oral oxcarbazepine formulations in healthy volunteers?

The bioequivalence of two 600-mg oxcarbazepine oral formulations (Aurene, Ivax Argentina, [test]; and Trileptal, Novartis Laboratories, [reference]) were assessed through the simultaneous determination of oxcarbazepine and the active metabolite 10,11-dyhydro-10-hydroxy-carbamazepine derivative (MHD). 12 healthy male volunteers received a single oral dose of 600 mg of each formulation, in a balanced, randomized, paired, crossover design, with a 7-day wash out period. Oxcarbazepine and MHD concentrations were established at 0.5,1, 1.5, 2, 3, 4, 6, 8, 24 and 48 h post dose by high performance liquid chromatography (HPLC). The regression coefficient determined for oxcarbazepine calibration curves was 0.9933 +/- 0.0236; and for MHD, was 0.9897 +/- 0.0017. The working range for both oxcarbazepine and its metabolite was from 0.1 to 10.0 microg/ml. The quantification limit was 0.1 microg/ml. The 90% confidence interval (CI) geometric mean for oxcarbazepine C(max), AUC(0-48 h) and AUC(0-infinity) ratios (test : reference) were 74.1-146.2%, 85.6-171.5% and 89.6-169.8%, respectively, and the 90% CI geometric mean for MHD C(max), AUC(0-48 h) and AUC(0-infinity) ratios (test : reference) were 84.0-122.3, 93.2-117.9 and 96.5-116.7, respectively. These results established the bioequivalence of two oxcarbazepine formulations from MHD kinetic data used in 12 healthy volunteers, while it was not possible to establish bioequivalence with oxcarbazepine. MHD quantification is preferred to that of the oxcarbazepine in order to assess bioequivalence, as the metabolite is responsible for the antiepileptic activity, presents linear kinetics in the therapeutic range, has lower intra-individual variability and higher plasma levels and half life than the parent drug.

Leptin and insulin homeostasis in epilepsy: relation to weight adverse conditions

During managing patients with epilepsy, there is a great risk of weight changes, particularly weight gain with some antiepileptic medications. Weight gain is not only a cosmetic problem that leads to non-compliance to medications but also increases the risk for atherosclerosis and its related complications. The mechanisms underlying weight gain in epilepsy are multiple and controversial and have been attributed to the effect of epilepsy and more commonly the effect of antiepileptic medications on the central and peripheral mechanisms regulating weight homeostasis including the two main homeostatic hormones, leptin, a protein product of obesity gene secreted by adipocytes and insulin, a protein product of pancreatic beta-cells. Increased blood levels of leptin and insulin due to leptin and insulin resistance is observed in patients with epilepsy. Leptin forms an important link between weight gain, insulin resistance, epilepsy and atherosclerosis. The knowledge of the novel roles of leptin in patients with epilepsy will help identification of early markers for the related adverse weight changes, thus allowing proper characterization of suitable antiepileptic medication as initial step during management and follow up of patients.

High and low dosage oxcarbazepine versus naltrexone for the prevention of relapse in alcohol-dependent patients

INTRODUCTION

Oxcarbazepine (OXC) reduces high-voltage-activated calcium currents, thus reducing glutamatergic transmission at corticostriatal synapses. This effect on NMDA glutamatergic transmission may play a role against the increased glutamatergic transmission determined by alcohol withdrawal. To investigate the efficacy and safety of OXC in relapse prevention we compared OXC at different dosages with Naltrexone (NAL) in a 90 days randomised open-label trial. Craving and psychiatric symptoms improvements were the secondary endpoints.

METHODS

Eighty-four detoxified alcohol dependent subjects currently meeting clinical criteria for alcohol dependence were randomised into three groups: 27 patients received 50 mg of naltrexone, 29 received 1500-1800 mg of oxcarbazepine (OXC high), 28 patients 600-900 mg of oxcarbazepine (OXC low). Craving (VAS; OCDS) and withdrawal (AWRS) rating scales were applied; psychiatric symptoms were evaluated through the SCL-90-R.

RESULTS

A significantly larger number of subjects remained alcohol free in the OXC high group (58.6%) with respect to both the OXC low (42.8%) and the NAL groups (40.7%). Comparing the OCDS total scores at the end of the treatment, the improvement was significantly greater for the NAL group with respect to the OXC low group. The reduction of the Hostility-Aggression subscore of the SCL-90-R was significantly greater in the OXC high group than that of the other groups. Dual diagnosis patients had a better outcome when treated with OXC high.

DISCUSSION

OXC at a dosage of 1500-1800 mg/day might be beneficial in terms of alcohol relapse prevention. The low dosage formulation did not show the same trend, but it still remain in the same range as NAL. The mechanism involved in the efficacy of oxcarbazepine in relapse prevention could be less related to craving and more connected to the treatment of the comorbid psychiatric symptomatology and the alcohol protracted withdrawal syndrome.

A validated stability indicating LC method for oxcarbazepine

The present paper describes the development of a stability indicating reversed phase liquid chromatographic (RPLC) method for oxcarbazepine in the presence of its impurities and degradation products generated from forced decomposition studies. The drug substance was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The degradation of oxcarbazepine was observed under base hydrolysis. The drug was found to be stable to other stress conditions attempted. Successful separation of the drug from the synthetic impurities and degradation product formed under stress conditions was achieved on a C18 column using mixture of aqueous 0.02 M potassium dihydrogen phosphate-acetonitrile-methanol (45:35:20, v/v/v) as mobile phase. The developed HPLC method was validated with respect to linearity, accuracy, precision, specificity and robustness. The developed HPLC method to determine the related substances and assay determination of oxcarbazepine can be used to evaluate the quality of regular production samples. It can be also used to test the stability samples of oxcarbazepine.

Long-term safety and tolerability of oxcarbazepine in painful diabetic neuropathy

BACKGROUND

Painful diabetic neuropathy is a common complication of diabetes and often resistant to treatment with standard analgesics. Treatment of diabetic neuropathy with antiepileptic drugs may provide pain relief.

AIM

To evaluate the long-term safety and tolerability of oxcarbazepine in two studies investigating the treatment of diabetic neuropathy.

OBJECTIVES

Patients with diabetes and a history of neuropathic pain were included. Study 1 was a multicenter, open-label study comprising a screening and 12-month treatment phase. Study 2 was a multicenter, open-label extension to a double-blind, randomized study. Oxcarbazepine was initiated at 300 mg/day and titrated over 4 weeks to tolerability or a maximum dose of 900 mg b.i.d. Safety was assessed by monitoring adverse events (AEs), serious AEs (SAEs), hematology, blood chemistry, urinalysis values, and vital signs.

RESULTS

Adverse events were most frequently reported in the nervous and gastrointestinal systems; 20.5% and 21.6% of patients withdrew because of AEs in study 1 and study 2, respectively. SAEs were reported in 13.7% and 14.4% of patients in study 1 and study 2, respectively.

CONCLUSIONS

Long-term treatment with oxcarbazepine is generally well tolerated in patients with painful diabetic neuropathy. Rapid titration of oxcarbazepine may be responsible for discontinuations resulting from AEs during early stages of treatment.

Oxcarbazepine in the treatment of bipolar disorder: a review

OBJECTIVE

To review the data on the efficacy of oxcarbazepine (OXC) in bipolar disorder (BD) and to provide recommendations for clinicians on the use of this medication in treating BD.

METHOD

Using the terms oxcarbazepine and bipolar disorder, oxcarbazepine and mania, or oxcarbazepine and bipolar depression, we conducted a computer-aided search of MEDLINE for the years 1950 to 2005.

RESULTS

Case reports, retrospective chart reviews, open prospective studies, and double-blind studies reported the efficacy and effectiveness of OXC in treating BD. The data indicate that OXC has efficacy in treating acute mania and may be a useful add-on in treating acute bipolar depression and in BD prophylaxis. OXC is generally well-tolerated.

CONCLUSION

We recommend using OXC as monotherapy or as add-on therapy in refractory mania, but we recommend it be used predominantly as an add-on treatment for other phases of BD in patients who have not improved with well-established treatments or in patients who have difficulty tolerating adequate dosages.

New Anticonvulsants—New Adverse Effects

Ongoing refinements in pharmacology continue to provide new medications for the treatment of seizure disorders and other neurologic conditions. The authors present the cases of two children who developed relatively uncommon adverse effects to new anticonvulsant medications, including metabolic acidosis with topiramate and hyponatremia with oxcarbazepine. In one of our two patients, intraoperative acidosis related to topiramate was noted. Appropriate investigation with documentation of normal serum lactate resulted in the exclusion of other potentially serious causes of acidosis and in the identification of topiramate as the causative agent. In our second patient, hyponatremia and status epilepticus resulted from therapy with oxcarbazepine. Prompt recognition of hyponatremia, fluid restriction, and cessation of oxcarbazepine therapy resulted in prompt correction of the hyponatremia. We review previous reports of these adverse effects with topiramate and oxcarbazepine, describe the pathophysiology of these metabolic alterations, provide treatment strategies, and make suggestions for monitoring patients during therapy with these anticonvulsant medications.

A Pilot Study of Oxcarbazepine Versus Acamprosate in Alcohol-Dependent Patients

OBJECTIVES

This pilot study has been designed to collect preliminary data on the use of a new antiepileptic drug in the management of alcoholic patients. Oxcarbazepine (OXC) blocks voltage-sensitive sodium channels. Its metabolite reduces high-voltage-activated calcium currents in striatal and cortical neurons, thus reducing glutamatergic transmission at corticostriatal synapses. This reduction is of interest in the treatment of alcohol dependence, as acamprosate (ACP) modulates NMDA receptors, resulting in an inhibition of glutamatergic transmission. Furthermore, OXC has revealed a mood-stabilizing effect in bipolar affective disorders. We have compared OXC with ACP in relapse prevention in recently withdrawn alcohol-dependent patients.

METHODS

We investigated the efficacy and safety of OXC (vs ACP) by conducting a 24-week randomized, parallel-group, open-label, clinical trial on 30 acutely detoxified alcoholic patients. Survival analyses (Kaplan-Meier) were performed to look for evidence of a longer "survival" of patients receiving OXC. We assessed time to first severe relapse and additional secondary endpoints.

RESULTS

After withdrawal, time to severe relapse and time to first consumption of any ethanol by OXC patients were not longer than for ACP patients. Abstinent patients in both study groups showed a significantly lower obsessive compulsive drinking scale-German version (OCDS-G) than relapsed patients. No undesired effects occurred when OXC patients consumed alcohol.

CONCLUSION

Our findings indicate that it could be worthwhile to test relapse prevention using OXC in an adequate sample. While the current sample size clearly limits further conclusions from this pilot study, it is noteworthy that OXC is well tolerated, even when alcohol is on board. Thus, in medication-based relapse prevention, OXC could be a promising alternative for alcoholic patients unable to benefit from ACP or naltrexone or those who have affective liability. OXC certainly merits a larger placebo-controlled trial.

Oxcarbazepine reduces seizure frequency in a high proportion of patients with both newly diagnosed and refractory partial seizures in clinical practice

The antiepileptic efficacy and tolerability of oxcarbazepine, used both as monotherapy and adjunctive therapy, were observed for 1 year in 202 adult patients, aged 17-83 years, with newly diagnosed or refractory partial epilepsy in clinical practice in Italy. At first observation, the seizure free rate was 72.2% in newly diagnosed patients given monotherapy, 40% in patients in whom oxcarbazepine replaced another monotherapy and 10.3% in patients given oxcarbazepine as adjunctive therapy. At least 50% reduction in seizure frequency was achieved in 90.7, 72 and 57%, respectively. Efficacy increased with the duration of treatment (p < 0.0001). In the 160 completers the seizure free rate was 61.3% with monotherapy and 28% with adjunctive therapy. 16.3% of patients reported adverse effects, mainly sedation and sleepiness; 5% discontinued oxcarbazepine because of adverse events. OXC is an effective and well-tolerated antiepileptic agent for the long-term treatment of partial epilepsy in adults.

Use of microbore LC-MS/MS for the quantification of oxcarbazepine and its active metabolite in rat brain microdialysis samples

A microbore LC-MS/MS method is developed and validated for the quantification of the anti-epileptic drug oxcarbazepine (OXC) and its active metabolite 10,11-dihydro-10-hydroxycarbamazepine (MHD) in rat brain microdialysates, together with the internal standard for microdialysis probe calibration, 2-methyl-5H-dibenz(b,f)azepine-5-carboxamide (m-CBZ). The benefits of gradient versus isocratic separation are shown, next to the improved sensitivity resulting from the addition of 0.1% formic acid to the mobile phase. The coupling of microdialysis with ESI-MS requires sample desalting for which column switching was applied. Using weighed regression to calculate the calibration curves (1-1000 ng/mL), the assay was validated in terms of linearity, accuracy and precision, yielding a sensitive (limit of quantification is 1 ng/mL) and selective method for quantification of OXC, MHD and m-CBZ. By applying this method, we were able to determine the extracellular concentrations of OXC and MHD during at least 4h after intraperitoneal (i.p.) administration of 10 mg/kg OXC.

Lack of pharmacokinetic interaction between oxcarbazepine and lamotrigine

Epilepsy and bipolar disorder are commonly treated by combination drug therapy, such as lamotrigine and oxcarbazepine. To ensure the safety of this combination, information on pharmacokinetics and tolerability must be available. The objective of study was to evaluate the pharmacokinetics and tolerability of coadministered lamotrigine and oxcarbazepine in healthy subjects. This randomized, single-blind, parallel-group study comprised three cohorts: lamotrigine (200 mg daily) plus oxcarbazepine (600 mg twice daily), lamotrigine (200 mg daily) plus placebo, and oxcarbazepine (600 mg twice daily) plus placebo. Serial blood samples were collected at steady state to determine serum concentrations of lamotrigine and plasma concentrations of oxcarbazepine and its active metabolite 10-monohydroxy metabolite (MHD). Pharmacokinetic parameters were determined by noncompartmental methods. Tolerability was monitored through adverse event reports, clinical laboratory results, vital signs, and electrocardiograms. A total of 47 male volunteers received study drugs. At steady state, lamotrigine AUC((0-24)) and C(max) were not significantly affected by oxcarbazepine co-therapy, nor were MHD AUC((0-12)) and C(max) significantly affected by lamotrigine co-therapy. The most common adverse events, headache, dizziness, nausea, and somnolence, occurred more frequently during lamotrigine and oxcarbazepine combination therapy than during the monotherapy. No significant changes in clinical laboratory parameters, vital signs, or electrocardiograms were reported. In conclusion, the combination of lamotrigine and oxcarbazepine does not require dose adjustments based on pharmacokinetic data. However, it is important to recognize that the combination therapy was associated with more frequent adverse events.

Oxcarbazepine monotherapy in benign childhood epilepsy with centrotemporal spikes: a clinical and cognitive evaluation

We report on 70 patients (aged 5.2-11.6 years) newly diagnosed with benign childhood epilepsy with centrotemporal spikes (BECTS) who were assigned to oxcarbazepine (OXC) monotherapy. All of them underwent clinical and electroencephalographic examination at baseline and at 3- to 6-month intervals during the study. Psychometric assessment was performed at baseline and after 18 months of treatment with the WISC-III, Illinois Test of Psychomotor Abilities, DSM-IV, and Bender-Santucci test. The Mann-Whitney U test was used to describe differences in the frequency of abnormal findings: (1) at initial evaluation, comparing patients with a matched group of 45 healthy controls, and (2) after 18 months of OXC monotherapy, as an individual follow-up in the patient group. Cognitive assessment at baseline revealed mild learning disabilities in 9% of patients and 7% of controls; all participants had a normal intelligence quotient. During the follow-up, sustained cessation of seizures under medication was observed in 53% of patients; an additional 21% had some relapse but were subsequently rendered seizure free, 21% experienced a >50% improvement, and 5% showed no improvement. Normalization of interictal epileptiform activity was observed in 58% of patients, 35% showed an improvement in the grade of electroencephalographic pathology, and 7% manifested no change at all. The initial mildly weak scores in isolated cognitive domains did not deteriorate, and even improved in some cases, during the course of the study, with concomitant electroencephalographic improvement or normalization and effective seizure control. The results of this study suggest that OXC is effective in preventing seizures and normalizing electroencephalograms and seems to preserve cognitive functions and behavioral abilities as long-term monotherapy in children with typical BECTS.

10-Hydroxycarbazepine Serum Concentration-to-Oxcarbazepine Dose Ratio

This study was done to evaluate the association between patient age and the concomitant use of enzyme-inducing antiepileptic drugs (AEDs) and oxcarbazepine (OXC) concentration-to-dose ratio (CDR) by a multivariate analysis. The influence of patient age and concomitant AEDs on the trough steady-state serum concentration of 10-hydroxycarbazepine (OHC) normalized to 1 mg/kg body weight of OXC or concentration-to-dose ratio (OHC-OXC-CDR) was assessed by analysis of covariance. Samples were collected from 106 patients (90% outpatients), aged 1-80, who were receiving OXC either alone (n = 41) or in combination with other AEDs (n = 65). The average OHC-OXC CDR was 0.70 +/- 0.26 (mean +/- SD). Analysis of covariance showed that patient age was influential (P < 0.001) and that there was a difference between the noninducers group (OXC or OXC + lamotrigine, topiramate, or valproate) and the inducers group (OXC + phenobarbital or phenytoin) (P < 0.001). The OHC-OXC CDR increased with age (r = 0.14, P < 0.001) and was approximately 48% lower in children aged 6 or less than in patients over 45, and approximately 32% lower in the inducers group than in patients receiving OXC alone. The correlation between OHC-OXC CDR and the age of the patients concerned with OXC alone was r = 0.48, P < 0.001. In the noninducers group the OHC-OXC CDR was 0.59 +/- 0.24 in patients aged 11 or less (n = 16), and 0.81 +/- 0.23 in patients over 11 years (n = 62). In the inducers group it was 0.25 +/- 0.11 in patients aged 11 or less (n = 3) and 0.57 +/- 0.18 in patients over the age of 11 (n = 25). The OHC-OXC CDR increased with patient age and decreased in the presence of enzyme-inducing AEDs in epileptic patients chronically treated with OXC. These influences may be clinically relevant, and, therefore, patient age and the presence of inducers should be considered in estimating either compliance or the OXC dose needed to achieve a desired OHC concentration.

Severe overdosage with the antiepileptic drug oxcarbazepine

Few published human data are available concerning the acute toxicity of the new antiepileptic drug oxcarbazepine of which the metabolite 10- monohydroxy derivate (MHD) is the pharmacologically effective compound. Two hours after a documented overdosage of more than 100 tablets oxcarbazepine, the serum level of the parent compound was 10-fold higher than the therapeutic dosage (31.6 mg l(-1)). However, the concentration of MHD, which peaked 7 h after intake, was only twofold higher (59.0 mg l(-1)). No life-threatening situations occurred and the patient fully recovered. The fact that oxcarbazepine is a prodrug and that the formation of the active MHD metabolite is a rate-limiting process may contribute to the relative low toxicity of the drug in overdose.

Clinical pharmacokinetics of oxcarbazepine

Oxcarbazepine is an antiepileptic drug with a chemical structure similar to carbamazepine, but with different metabolism. Oxcarbazepine is rapidly reduced to 10,11-dihydro-10-hydroxy-carbazepine (monohydroxy derivative, MHD), the clinically relevant metabolite of oxcarbazepine. MHD has (S)-(+)- and the (R)-(-)-enantiomer, but the pharmacokinetics of the racemate are usually reported. The bioavailability of the oral formulation of oxcarbazepine is high (>95%). It is rapidly absorbed after oral administration, reaching peak concentrations within about 1-3 hours after a single dose, whereas the peak of MHD occurs within 4-12 hours. At steady state, the peak of MHD occurs about 2-4 hours after drug intake. The plasma protein binding of MHD is about 40%. Cerebrospinal fluid concentrations of MHD are in the same range as unbound plasma concentrations of MHD. Oxcarbazepine can be transferred significantly through the placenta in humans. Oxcarbazepine and MHD exhibit linear pharmaco-kinetics and no autoinduction occurs. Elimination half-lives in healthy volunteers are 1-5 hours for oxcarbazepine and 7-20 hours for MHD. Longer and shorter elimination half-lives have been reported in elderly volunteers and children, respectively. Mild to moderate hepatic impairment does not appear to affect MHD pharmacokinetics. Renal impairment affects the pharmacokinetics of oxcarbazepine and MHD. The interaction potential of oxcarbazepine is relatively low. However, enzyme-inducing antiepileptic drugs such as phenytoin, phenobarbital or carbamazepine can reduce slightly the concentrations of MHD. Verapamil may moderately decrease MHD concentrations, but this effect is probably without clinical relevance. The influence of oxcarbazepine on other antiepileptic drugs is not clinically relevant in most cases. However, oxcarbazepine appears to increase concentrations of phenytoin and to decrease trough concentrations of lamotrigine and topiramate. Oxcarbazepine lowers concentrations of ethinylestra-diol and levonorgestrel, and women treated with oxcarbazepine should consider additional contraceptive measures. Due to the absent or lower enzyme-inducing effect of oxcarbazepine, switching from carbamazepine to oxcarbazepine can result in increased serum concentrations of comedication, sometimes associated with adverse effects. The effect of oxcarbazepine appears to be related to dose and to serum concentrations of MHD. In general, daily fluctuations of MHD concentration are relatively slight, smaller than would be expected from the elimination half-life of MHD. However, relatively high fluctuations can be observed in individual patients. Therapeutic monitoring may help to decide whether adverse effects are dependent on MHD concentrations. A mean therapeutic range of 15-35 mg/L for MHD seems to be appropriate. However, more systematic studies exploring the concentration-effect relationship are required.