Oxcarbazepine. A review of its pharmacology and therapeutic potential in epilepsy, trigeminal neuralgia and affective disorders

A 5-Year Study of Antiseizure Medications (ASMs) Monitoring in Patients with Neuropsychiatric Disorders in an Italian Clinical Center

Despite receiving appropriate antiseizure medications (ASMs), a relevant percentage of neuropsychiatric patients do not benefit from this approach, and one reason is subtherapeutic ASMs plasma concentration (C(p)) due to improper drug adherence, interindividual pharmacokinetic differences, or metabolic interactions among different drugs. For these reasons, therapeutic drug monitoring (TDM) by measuring ASMs C(p) is an effective tool that improves pharmacological therapies in clinical practice. Based on these premises, in the present real-world study, we analyzed the C(p) of the most used ASMs in diverse medical conditions, which were assayed during the years 2018-2022 at the University Hospital of Pisa, including about 24,000 samples. This population was largely heterogeneous, and our database did not contain clinical information about the patients. The most used ASMs were Valproate (VPA: 54.5%) and Levetiracetam (LEV: 18.6%), followed by Oxcarbazepine (OxCBZ: 8.3%) and Carbamazepine (CBZ: 7.2%), whereas the associations LEV/VPA, Ethosuximide (ESM)/VPA, and CBZ/VPA were the most frequently proposed. In about 2/3 of assays, ASMs C(p) was in range, except for VPA, which was underdosed in almost half of the samples. Importantly, toxic levels of ASMs C(p) were found very rarely. For VPA, there was a decrease of mean C(p) across ages, from adolescents to older patients, while the C(p) of LEV, CBZ, OxCBZ, and Topiramate (TPM) showed a slight tendency to increase. When we compared females and males, we found that for VPA, the average age was higher for females, whereas women taking Lamotrigine (LTG) and OxCBZ were younger than men. Then, comparing ASMs used in neurologic and psychiatric disorders, based on the request form, it emerged that the mean C(p) of CBZ, OxCBZ, and LTG on samples collected in the Psychiatric Unit was lower compared to the Neurology and Child Neuropsychiatry Units. Finally, the ASMs subjected to multiple dosing starting from an initial subtherapeutic C(p) increased their level at different time points within a year, reaching the reference range for some of them. In conclusion, the present study suggests that TDM is widely applied to monitor ASMs C(p), finding many of them within the reference range, as a demonstration of its utility in clinical practice.

Antiepileptic drugs for treating seizures in people with brain tumours

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To compare the efficacy and tolerability of antiepileptic drugs (AEDs) taken as monotherapy or add‐on therapy for seizures in people with brain tumours.

Simulation and Machine Learning Methods for Ion-Channel Structure Determination, Mechanistic Studies and Drug Design

Ion channels are expressed in almost all living cells, controlling the in-and-out communications, making them ideal drug targets, especially for central nervous system diseases. However, owing to their dynamic nature and the presence of a membrane environment, ion channels remain difficult targets for the past decades. Recent advancement in cryo-electron microscopy and computational methods has shed light on this issue. An explosion in high-resolution ion channel structures paved way for structure-based rational drug design and the state-of-the-art simulation and machine learning techniques dramatically improved the efficiency and effectiveness of computer-aided drug design. Here we present an overview of how simulation and machine learning-based methods fundamentally changed the ion channel-related drug design at different levels, as well as the emerging trends in the field.

Antiepileptic drug monotherapy for epilepsy: a network meta-analysis of individual participant data

BACKGROUND

This is an updated version of the original Cochrane Review published in 2017. Epilepsy is a common neurological condition with a worldwide prevalence of around 1%. Approximately 60% to 70% of people with epilepsy will achieve a longer-term remission from seizures, and most achieve that remission shortly after starting antiepileptic drug treatment. Most people with epilepsy are treated with a single antiepileptic drug (monotherapy) and current guidelines from the National Institute for Health and Care Excellence (NICE) in the United Kingdom for adults and children recommend carbamazepine or lamotrigine as first-line treatment for focal onset seizures and sodium valproate for generalised onset seizures; however, a range of other antiepileptic drug (AED) treatments are available, and evidence is needed regarding their comparative effectiveness in order to inform treatment choices.

OBJECTIVES

To compare the time to treatment failure, remission and first seizure of 12 AEDs (carbamazepine, phenytoin, sodium valproate, phenobarbitone, oxcarbazepine, lamotrigine, gabapentin, topiramate, eventrate, zonisamide, eslicarbazepine acetate, lacosamide) currently used as monotherapy in children and adults with focal onset seizures (simple focal, complex focal or secondary generalised) or generalised tonic-clonic seizures with or without other generalised seizure types (absence, myoclonus).

SEARCH METHODS

For the latest update, we searched the following databases on 12 April 2021: the Cochrane Register of Studies (CRS Web), which includes PubMed, Embase, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform (ICTRP), the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Epilepsy Group Specialised Register and MEDLINE (Ovid, 1946 to April 09, 2021). We handsearched relevant journals and contacted pharmaceutical companies, original trial investigators and experts in the field.

SELECTION CRITERIA

We included randomised controlled trials of a monotherapy design in adults or children with focal onset seizures or generalised onset tonic-clonic seizures (with or without other generalised seizure types).

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) and network meta-analysis (NMA) review. Our primary outcome was 'time to treatment failure', and our secondary outcomes were 'time to achieve 12-month remission', 'time to achieve six-month remission', and 'time to first seizure post-randomisation'. We performed frequentist NMA to combine direct evidence with indirect evidence across the treatment network of 12 drugs. We investigated inconsistency between direct 'pairwise' estimates and NMA results via node splitting. Results are presented as hazard ratios (HRs) with 95% confidence intervals (CIs) and we assessed the certainty of the evidence using the CiNeMA approach, based on the GRADE framework. We have also provided a narrative summary of the most commonly reported adverse events.

MAIN RESULTS

IPD were provided for at least one outcome of this review for 14,789 out of a total of 22,049 eligible participants (67% of total data) from 39 out of the 89 eligible trials (43% of total trials). We could not include IPD from the remaining 50 trials in analysis for a variety of reasons, such as being unable to contact an author or sponsor to request data, data being lost or no longer available, cost and resources required to prepare data being prohibitive, or local authority or country-specific restrictions. No IPD were available from a single trial of eslicarbazepine acetate, so this AED could not be included in the NMA. Network meta-analysis showed high-certainty evidence that for our primary outcome, 'time to treatment failure', for individuals with focal seizures; lamotrigine performs better than most other treatments in terms of treatment failure for any reason and due to adverse events, including the other first-line treatment carbamazepine; HRs (95% CIs) for treatment failure for any reason for lamotrigine versus: eventrate 1.01 (0.88 to 1.20), zonisamide 1.18 (0.96 to 1.44), lacosamide 1.19 (0.90 to 1.58), carbamazepine 1.26 (1.10 to 1.44), oxcarbazepine 1.30 (1.02 to 1.66), sodium valproate 1.35 (1.09 to 1.69), phenytoin 1.44 (1.11 to 1.85), topiramate 1.50 (1.23 to 1.81), gabapentin 1.53 (1.26 to 1.85), phenobarbitone 1.97 (1.45 to 2.67). No significant difference between lamotrigine and eventrate was shown for any treatment failure outcome, and both AEDs seemed to perform better than all other AEDs. For people with generalised onset seizures, evidence was more limited and of moderate certainty; no other treatment performed better than first-line treatment sodium valproate, but there were no differences between sodium valproate, lamotrigine or eventrate in terms of treatment failure; HRs (95% CIs) for treatment failure for any reason for sodium valproate versus: lamotrigine 1.06 (0.81 to 1.37), eventrate 1.13 (0.89 to 1.42), gabapentin 1.13 (0.61 to 2.11), phenytoin 1.17 (0.80 to 1.73), oxcarbazepine 1.24 (0.72 to 2.14), topiramate 1.37 (1.06 to 1.77), carbamazepine 1.52 (1.18 to 1.96), phenobarbitone 2.13 (1.20 to 3.79), lacosamide 2.64 (1.14 to 6.09). Network meta-analysis also showed high-certainty evidence that for secondary remission outcomes, few notable differences were shown for either seizure type; for individuals with focal seizures, carbamazepine performed better than gabapentin (12-month remission) and sodium valproate (six-month remission). No differences between lamotrigine and any AED were shown for individuals with focal seizures, or between sodium valproate and other AEDs for individuals with generalised onset seizures. Network meta-analysis also showed high- to moderate-certainty evidence that, for 'time to first seizure,' in general, the earliest licensed treatments (phenytoin and phenobarbitone) performed better than the other treatments for individuals with focal seizures; phenobarbitone performed better than both first-line treatments carbamazepine and lamotrigine. There were no notable differences between the newer drugs (oxcarbazepine, topiramate, gabapentin, eventrate, zonisamide and lacosamide) for either seizure type. Generally, direct evidence (where available) and network meta-analysis estimates were numerically similar and consistent with confidence intervals of effect sizes overlapping. There was no important indication of inconsistency between direct and network meta-analysis results. The most commonly reported adverse events across all drugs were drowsiness/fatigue, headache or migraine, gastrointestinal disturbances, dizziness/faintness and rash or skin disorders; however, reporting of adverse events was highly variable across AEDs and across studies.

AUTHORS' CONCLUSIONS

High-certainty evidence demonstrates that for people with focal onset seizures, current first-line treatment options carbamazepine and lamotrigine, as well as newer drug eventrate, show the best profile in terms of treatment failure and seizure control as first-line treatments. For people with generalised tonic-clonic seizures (with or without other seizure types), current first-line treatment sodium valproate has the best profile compared to all other treatments, but lamotrigine and eventrate would be the most suitable alternative first-line treatments, particularly for those for whom sodium valproate may not be an appropriate treatment option. Further evidence from randomised controlled trials recruiting individuals with generalised tonic-clonic seizures (with or without other seizure types) is needed.

Drug Delivery Challenges in Brain Disorders across the Blood-Brain Barrier: Novel Methods and Future Considerations for Improved Therapy

Due to the physiological and structural properties of the blood-brain barrier (BBB), the delivery of drugs to the brain poses a unique challenge in patients with central nervous system (CNS) disorders. Several strategies have been investigated to circumvent the barrier for CNS therapeutics such as in epilepsy, stroke, brain cancer and traumatic brain injury. In this review, we summarize current and novel routes of drug interventions, discuss pharmacokinetics and pharmacodynamics at the neurovascular interface, and propose additional factors that may influence drug delivery. At present, both technological and mechanistic tools are devised to assist in overcoming the BBB for more efficient and improved drug bioavailability in the treatment of clinically devastating brain disorders.

Biologically active metabolites in drug discovery

Biologically active metabolites are a valuable resource for development of drug candidates and lead structures for drug design. This digest highlights a selection of biologically active metabolites that have been used as new chemical entities for development or as lead structures for drug design.

Simultaneous quantification of oxcarbazepine and its active metabolite in spiked human plasma using ultra performance liquid chromatography-MS/MS

Aim: Clinical monitoring of oxcarbazepine (OXC) and its metabolite licarbazepine (MHD) in biological matrix requires a sensitive and validated analytical method. The aim of this study is to develop and validate an optimized ultra performance liquid chromatography-MS/MS based bioanalytical method for the simultaneous estimation of OXC and its metabolite MHD in human plasma, using deuterated internal standard method. Materials & methods: A reverse phase ultra performance liquid chromatography analysis and mass spectrometric detection was performed using electrospray ionization in positive ion mode as interface, multiple reaction monitoring as mode of acquisition. Results & conclusion: The linearity range was 10-4011 ng/ml for OXC and 40-16061 ng/ml for MHD. The kinetic parameters were calculated and compared for bioequivalence. This method fulfilled the validation guidelines, could be employed for determining bioavailability and in new formulation development studies.

Oxcarbazepine for Behavioral Disorders after Brain Injury: Factors Influencing Efficacy

Carbamazepine and oxcarbazepine are used for behavioral disorders following organic diseases. After severe acquired brain injury, patients may develop frontal symptoms. In our neurological rehabilitation routine, oxcarbazepine is used for better safety over carbamazepine, although its efficacy is not clarified. We aimed to improve knowledge on this use of oxcarbazepine, by probing clinical factors associated with response. We retrospectively examined the clinical records of our patients, collecting clinical variables and outcomes of efficacy, both clinician-rated and caregiver/self-rated. We described the distribution of clinical variables and examined their associations via logistic regressions. Patients in our cohort were predominantly pediatric, with frontal lobe damage and irritable/reactive. With an oxcarbazepine median dose of 975 mg, almost half of patients improved. We found several clinical factors associated with clinician-rated efficacy: absence of frontal damage and absence of irritability/reactivity symptoms; clinical factors associated with caregivers/patients-rated efficacy were: higher DRS score at baseline and higher patient age. In this retrospective study, we observed that oxcarbazepine was differentially efficacious in patients with specific characteristics. Our study could not examine drug therapy separately from neuropsychological therapy, nor the influence of dose. Our associative results should be verified experimentally, also assessing causality and establishing dose-related efficacy and safety.

Pharmacogenomic Biomarkers and Their Applications in Psychiatry

Realizing the promise of precision medicine in psychiatry is a laudable and beneficial endeavor, since it should markedly reduce morbidity and mortality and, in effect, alleviate the economic and social burden of psychiatric disorders. This review aims to summarize important issues on pharmacogenomics in psychiatry that have laid the foundation towards personalized pharmacotherapy and, in a broader sense, precision medicine. We present major pharmacogenomic biomarkers and their applications in a variety of psychiatric disorders, such as depression, attention-deficit/hyperactivity disorder (ADHD), narcolepsy, schizophrenia, and bipolar disorder. In addition, we extend the scope into epilepsy, since antiepileptic drugs are widely used to treat psychiatric disorders, although epilepsy is conventionally considered to be a neurological disorder.

Oxcarbazepine add-on for drug-resistant focal epilepsy

BACKGROUND

Epilepsy is a common neurological disorder. In approximately 30% of epilepsy cases, seizures are uncontrolled by one antiepileptic drug (AED). These people require treatment with a combination of multiple AEDs and are described as having drug-resistant epilepsy. Oxcarbazepine is a keto-analogue of carbamazepine, an established AED, and can be used as an add-on treatment for drug-resistant epilepsy.

OBJECTIVES

To assess the efficacy and tolerability of oxcarbazepine as an add-on treatment for people with drug-resistant focal epilepsy.

SEARCH METHODS

The following databases were searched on 24 September 2018: Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL); Medline (Ovid) 1946 to 21 September 2018; ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). Originally, we also searched SCOPUS as a substitute for Embase, but this is no longer necessary, because randomised and quasi-randomised controlled trials in Embase are now included in CENTRAL.

SELECTION CRITERIA

Randomised controlled trials with parallel-group or cross-over design, recruiting people of any age with drug-resistant focal epilepsy. We accepted any level of blinding and trials could be placebo- or active-controlled.

DATA COLLECTION AND ANALYSIS

In accordance with the methodological procedures expected by the Cochrane Collaboration, two review authors independently assessed trial eligibility before extracting data and assessing risk of bias. We assessed the primary outcomes: median percentage seizure reduction per 28 days; 50% or greater reduction in seizure frequency; and adverse effects including ataxia, hyponatraemia, and somnolence. We assessed the secondary outcomes: seizure freedom; treatment withdrawal; cognitive effects; and quality of life. We used an intention-to-treat population for all primary analyses. We present results as risk ratios (RR) with 95% confidence intervals (CI), with the exception of adverse effects which we present with 99% CI.

MAIN RESULTS

We identified six eligible studies, involving 1593 participants. We judged that three studies were at unclear risk of bias and three were at high risk of bias. Bias mainly arose from lack of methodological details and from high attrition rates. Participants were aged 1 month to 65 years, with a diagnosis of drug-resistant focal epilepsy. All studies were either placebo- or alternative-dose-controlled with parallel-group design. The treatment period varied from 9 days to 26 weeks. The median percentage seizure reduction per 28 days (3 studies; moderate-certainty evidence) ranged from 26% to 83.3% for participants randomised to experimental oxcarbazepine compared to 7.6% to 28.7% for participants randomised to control treatment. Oxcarbazepine may increase the responder rate for 50% or greater reduction in seizure frequency compared to control treatment (RR 1.80, 95% CI 1.27 to 2.56; random-effects model; 6 studies; low-certainty evidence). For seizure freedom, the RR was 2.86 (95% CI 1.19 to 6.87; random-effects model; 5 studies; low-certainty evidence), suggesting an advantageous effectiveness of oxcarbazepine over control treatment. Treatment with oxcarbazepine was associated with an increased treatment withdrawal rate compared to control (RR 1.75, 95% CI 1.44 to 2.13; fixed-effect model; 6 studies; moderate-certainty evidence). The largest oxcarbazepine dose used, 2400 mg/d, was associated with a higher treatment withdrawal rate (RR 2.38, 95% CI 1.92 to 2.94; fixed-effect model; 2 studies) compared to control, than 1200 mg/d (RR 1.54, 95% CI 1.21 to 1.95; fixed-effect model; 3 studies) or 600 mg/d oxcarbazepine (RR 0.79, 95% CI 0.55 to 1.15; fixed-effect model; 1 study). Treatment with oxcarbazepine was associated with an increased incidence of multiple adverse effects including: ataxia (RR 2.54, 99% CI 0.86 to 7.54; random-effects model; 5 studies; moderate-certainty evidence); and somnolence (RR 2.03, 99% CI 1.17 to 3.54; random-effects model; 6 studies; low-certainty evidence). Hyponatraemia occurred more frequently with oxcarbazepine treatment but not significantly so (RR 2.53, 99% CI 0.27 to 23.85; fixed-effect model; 6 studies; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Oxcarbazepine might be effective at reducing seizure frequency when used as an add-on for drug-resistant focal epilepsy. The efficacy outcomes - 50% or greater seizure reduction and seizure freedom - were derived from low-certainty evidence. We are, therefore, uncertain whether the estimated effect size is representative of the true effect. In contrast, the evidence for median percentage seizure reduction and treatment withdrawal were of moderate certainty: thus, we are fairly certain of the effect estimates' reliability. Overall, we are unsure of the true efficacy of oxcarbazepine, but have concerns about its tolerability.

Oxcarbazepine-Induced Cutaneous Reaction in a Female of Mexican Ancestry

Objectives: To report an oxcarbazepine (OXC)-induced cutaneous reaction in a female of Mexican ancestry. Case Summary: A 60-year-old female of Mexican ancestry presented to clinic with a diffuse morbilliform rash, with erythema and eruptions of papules/pustules concentrated on her neck and torso. The rash appeared 1 week following the initiation of OXC for trigeminal neuralgia. Initially, the correlation between the reaction and initiation of OXC was not recognized by the provider. OXC was continued for a total of 4 weeks and several medical encounters transpired in the interim. Supportive therapy, in the form of oral antihistamines and oral/topical corticosteroids, failed to resolve the rash. A clinical pharmacist prompted the discontinuation of OXC due to suspicion that it incited the adverse reaction. Oral corticosteroid therapy was initiated and tapered over 2 weeks, with rash dissipation occurring in 1 month. Discussion: The association of OXC with the cutaneous eruption was classified as "probable" based on the Naranjo Scale. While financial resources were not available to perform genetic testing, it may be possible that the genetic status of this patient lent itself to greater potential for cutaneous reactions with OXC. Further research is needed to determine whether pharmacogenetic variables affiliated with pre-Columbian lineage may predispose individuals to specific adverse drug reactions. Conclusion: As regional genotypes disperse globally, it is imperative that clinicians are cognizant of risks regarding genetically implicated adverse drug reactions. While information is limited for certain ethnicities, it is essential that providers diligently monitor all populations for reactions characteristic to specific medications.

Pharmacokinetic considerations for anti-epileptic drugs in children

INTRODUCTION

Epilepsy is a chronic and debilitating neurological disease, with a peak of incidence in the first years of life. Today, the vast armamentarium of antiepileptic drugs (AEDs) available make even more challenging to select the most appropriate AED and establish the most effective dosing regimen. In fact, AEDs pharmacokinetics is under the influence of important age-related factors which cannot be ignored. Areas covered: Physiological changes occurring during development age (different body composition, immature metabolic patterns, reduced renal activity) can significantly modify the pharmacokinetic profile of AEDs (adsorption, volume of distribution, half-life, clearance), leading to an altered treatment response. We reviewed the main pharmacokinetic characteristics of AEDs used in children, focusing on age-related factors which are of relevance when treating this patient population. Expert opinion: To deal with this pharmacokinetic variability, physicians have at their disposal two tools: 1) therapeutic drug concentration monitoring, which may help to set the optimal therapeutic regimen for each patient and to monitor eventual fluctuation, and 2) the use of extended-release drug formulations, when available. In the next future, the development of 'ad-hoc' electronic dashboard systems will represent relevant decision-support tools making the AED therapy even more individualized and precise, especially in children.

Oxcarbazepine versus phenytoin monotherapy for epilepsy: an individual participant data review

BACKGROUND

This is an updated version of the Cochrane Review previously published in 2013. This review is one in a series of Cochrane Reviews investigating pair-wise monotherapy comparisons.Epilepsy is a common neurological condition in which abnormal electrical discharges from the brain cause recurrent unprovoked seizures. It is believed that with effective drug treatment, up to 70% of individuals with active epilepsy have the potential to become seizure-free and go into long-term remission shortly after starting drug therapy with a single antiepileptic drug in monotherapy.Worldwide, phenytoin is a commonly used antiepileptic drug. It is important to know how newer drugs, such as oxcarbazepine, compare with commonly used standard treatments.

OBJECTIVES

To review the time to treatment failure, remission and first seizure with oxcarbazepine compared to phenytoin, when used as monotherapy in people with focal onset seizures or generalised tonic-clonic seizures (with or without other generalised seizure types).

SEARCH METHODS

We searched the following databases on 20 August 2018: the Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid, 1946 to 20 August 2018), ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We handsearched relevant journals and contacted pharmaceutical companies, original trial investigators and experts in the field.

SELECTION CRITERIA

We included randomised controlled trials comparing monotherapy with either oxcarbazepine or phenytoin in children or adults with focal onset seizures or generalised onset tonic-clonic seizures.

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) review. Our primary outcome was time to treatment failure and our secondary outcomes were time to first seizure post-randomisation, time to six-month and 12-month remission, and incidence of adverse events. We used Cox proportional hazards regression models to obtain trial-specific estimates of hazard ratios (HRs) with 95% confidence intervals (CIs), using the generic inverse variance method to obtain the overall pooled HR and 95% CI.

MAIN RESULTS

Individual participant data were available for 480 out of a total of 517 participants (93%), from two out of three included trials. For remission outcomes, a HR of less than one indicated an advantage for phenytoin; and for first seizure and treatment failure outcomes, a HR of less than one indicated an advantage for oxcarbazepine.The results for time to treatment failure for any reason related to treatment showed a potential advantage of oxcarbazepine over phenytoin, but this was not statistically significant (pooled HR adjusted for epilepsy type: 0.78 95% CI 0.53 to 1.14, 476 participants, two trials, moderate-quality evidence). Our analysis showed that treatment failure due to adverse events occurred later on with oxcarbazepine than phenytoin (pooled HR for all participants: 0.22 (95% CI 0.10 to 0.51, 480 participants, two trials, high-quality evidence). Our analysis of time to treatment failure due to lack of efficacy showed no clear difference between the drugs (pooled HR for all participants: 1.17 (95% CI 0.31 to 4.35), 480 participants, two trials, moderate-quality evidence).We found no clear or statistically significant differences between drugs for any of the secondary outcomes of the review: time to first seizure post-randomisation (pooled HR adjusted for epilepsy type: 0.97 95% CI 0.75 to 1.26, 468 participants, two trials, moderate-quality evidence); time to 12-month remission (pooled HR adjusted for epilepsy type 1.04 95% CI 0.77 to 1.41, 468 participants, two trials, moderate-quality evidence) and time to six-month remission (pooled HR adjusted for epilepsy type: 1.06 95% CI 0.82 to 1.36, 468 participants, two trials, moderate-quality evidence).The most common adverse events reported in more than 10% of participants on either drug were somnolence (28% of total participants, with similar rates for both drugs), headache (15% of total participants, with similar rates for both drugs), dizziness (14.5% of total participants, reported by slightly more participants on phenytoin (18%) than oxcarbazepine (11%)) and gum hyperplasia (reported by substantially more participants on phenytoin (18%) than oxcarbazepine (2%)).The results of this review are applicable mainly to individuals with focal onset seizures; 70% of included individuals experienced seizures of this type at baseline. The two studies included in IPD meta-analysis were generally of good methodological quality but the design of the studies may have biased the results for the secondary outcomes (time to first seizure post-randomisation, time to six-month and 12-month remission) as seizure recurrence data were not collected following treatment failure or withdrawal from the study. In addition, misclassification of epilepsy type may have impacted on results, particularly for individuals with generalised onset seizures.

AUTHORS' CONCLUSIONS

High-quality evidence provided by this review indicates that treatment failure due to adverse events occurs significantly later with oxcarbazepine than phenytoin. For individuals with focal onset seizures, moderate-quality evidence suggests that oxcarbazepine may be superior to phenytoin in terms of treatment failure for any reason, seizure recurrence and seizure remission. Therefore, oxcarbazepine may be a preferable alternative treatment than phenytoin, particularly for individuals with focal onset seizures. The evidence in this review which relates to individuals with generalised onset seizures is of low quality and does not inform current treatment policy.We recommend that future trials should be designed to the highest quality possible with regards to choice of population, classification of seizure type, duration of follow-up (including continued follow-up after failure or withdrawal of randomised treatment), choice of outcomes and analysis, and presentation of results.

Antiepileptic drug monotherapy for epilepsy: a network meta-analysis of individual participant data

BACKGROUND

Epilepsy is a common neurological condition with a worldwide prevalence of around 1%. Approximately 60% to 70% of people with epilepsy will achieve a longer-term remission from seizures, and most achieve that remission shortly after starting antiepileptic drug treatment. Most people with epilepsy are treated with a single antiepileptic drug (monotherapy) and current guidelines from the National Institute for Health and Care Excellence (NICE) in the United Kingdom for adults and children recommend carbamazepine or lamotrigine as first-line treatment for partial onset seizures and sodium valproate for generalised onset seizures; however a range of other antiepileptic drug (AED) treatments are available, and evidence is needed regarding their comparative effectiveness in order to inform treatment choices.

OBJECTIVES

To compare the time to withdrawal of allocated treatment, remission and first seizure of 10 AEDs (carbamazepine, phenytoin, sodium valproate, phenobarbitone, oxcarbazepine, lamotrigine, gabapentin, topiramate, levetiracetam, zonisamide) currently used as monotherapy in children and adults with partial onset seizures (simple partial, complex partial or secondary generalised) or generalised tonic-clonic seizures with or without other generalised seizure types (absence, myoclonus).

SEARCH METHODS

We searched the following databases: Cochrane Epilepsy's Specialised Register, CENTRAL, MEDLINE and SCOPUS, and two clinical trials registers. We handsearched relevant journals and contacted pharmaceutical companies, original trial investigators, and experts in the field. The date of the most recent search was 27 July 2016.

SELECTION CRITERIA

We included randomised controlled trials of a monotherapy design in adults or children with partial onset seizures or generalised onset tonic-clonic seizures (with or without other generalised seizure types).

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) review and network meta-analysis. Our primary outcome was 'time to withdrawal of allocated treatment', and our secondary outcomes were 'time to achieve 12-month remission', 'time to achieve six-month remission', 'time to first seizure post-randomisation', and 'occurrence of adverse events'. We presented all time-to-event outcomes as Cox proportional hazard ratios (HRs) with 95% confidence intervals (CIs). We performed pairwise meta-analysis of head-to-head comparisons between drugs within trials to obtain 'direct' treatment effect estimates and we performed frequentist network meta-analysis to combine direct evidence with indirect evidence across the treatment network of 10 drugs. We investigated inconsistency between direct estimates and network meta-analysis via node splitting. Due to variability in methods and detail of reporting adverse events, we have not performed an analysis. We have provided a narrative summary of the most commonly reported adverse events.

MAIN RESULTS

IPD was provided for at least one outcome of this review for 12,391 out of a total of 17,961 eligible participants (69% of total data) from 36 out of the 77 eligible trials (47% of total trials). We could not include IPD from the remaining 41 trials in analysis for a variety of reasons, such as being unable to contact an author or sponsor to request data, data being lost or no longer available, cost and resources required to prepare data being prohibitive, or local authority or country-specific restrictions.We were able to calculate direct treatment effect estimates for between half and two thirds of comparisons across the outcomes of the review, however for many of the comparisons, data were contributed by only a single trial or by a small number of participants, so confidence intervals of estimates were wide.Network meta-analysis showed that for the primary outcome 'Time to withdrawal of allocated treatment,' for individuals with partial seizures; levetiracetam performed (statistically) significantly better than current first-line treatment carbamazepine and other current first-line treatment lamotrigine performed better than all other treatments (aside from levetiracetam); carbamazepine performed significantly better than gabapentin and phenobarbitone (high-quality evidence). For individuals with generalised onset seizures, first-line treatment sodium valproate performed significantly better than carbamazepine, topiramate and phenobarbitone (moderate- to high-quality evidence). Furthermore, for both partial and generalised onset seizures, the earliest licenced treatment, phenobarbitone seems to perform worse than all other treatments (moderate- to high-quality evidence).Network meta-analysis also showed that for secondary outcomes 'Time to 12-month remission of seizures' and 'Time to six-month remission of seizures,' few notable differences were shown for either partial or generalised seizure types (moderate- to high-quality evidence). For secondary outcome 'Time to first seizure,' for individuals with partial seizures; phenobarbitone performed significantly better than both current first-line treatments carbamazepine and lamotrigine; carbamazepine performed significantly better than sodium valproate, gabapentin and lamotrigine. Phenytoin also performed significantly better than lamotrigine (high-quality evidence). In general, the earliest licenced treatments (phenytoin and phenobarbitone) performed better than the other treatments for both seizure types (moderate- to high-quality evidence).Generally, direct evidence and network meta-analysis estimates (direct plus indirect evidence) were numerically similar and consistent with confidence intervals of effect sizes overlapping.The most commonly reported adverse events across all drugs were drowsiness/fatigue, headache or migraine, gastrointestinal disturbances, dizziness/faintness and rash or skin disorders.

AUTHORS' CONCLUSIONS

Overall, the high-quality evidence provided by this review supports current guidance (e.g. NICE) that carbamazepine and lamotrigine are suitable first-line treatments for individuals with partial onset seizures and also demonstrates that levetiracetam may be a suitable alternative. High-quality evidence from this review also supports the use of sodium valproate as the first-line treatment for individuals with generalised tonic-clonic seizures (with or without other generalised seizure types) and also demonstrates that lamotrigine and levetiracetam would be suitable alternatives to either of these first-line treatments, particularly for those of childbearing potential, for whom sodium valproate may not be an appropriate treatment option due to teratogenicity.

Old Friends With New Faces: Are Sodium Channel Blockers the Future of Adjunct Pain Medication Management?

Providers are being asked to decrease the emphasis and overutilization of long-term opioid therapy, but many are left without proper guidance on appropriate utilization of nonopioid therapies. Furthermore, therapeutic options are quite limited and many providers lack confidence in distinguishing available alternatives. When first-line therapy has failed in a patient, there is an apparent lack of knowledge on how to proceed with choosing subsequent therapy. To choose among alternative agents, an understanding of pharmacology, pharmacokinetics, and efficacy in targeting various pain conditions is necessary. This article focuses on the use of the carboxamide class of sodium channel blockers (carbamazepine, oxcarbazepine, eslicarbazepine) for adjunct pain medication management including research updates in pharmacology, pharmacokinetics, and current evidence for pain along with promising areas of research. It is an evidence update for clinical use of sodium channel blockers, clarifies misconceptions regarding their use, and highlights emerging research for improved pain targets that justifies additional study. We performed a complete review of the literature using the search terms, "oxcarbazepine," "carbamazepine," and "eslicarbazepine" in conjunction with "pharmacokinetics," "adverse effects," "pharmacology," "voltage-gated sodium channel subtype," "neuropathic pain," "inflammatory pain," "metabolism," "epoxide metabolite formation," "drug interactions," "CYP450 interactions," "pain phenotype," and "chronic pain management." Databases searched included PubMed and Google Scholar. Package inserts were used for drug structure illustration, adverse reactions, and bioavailability. Pharmacology and pharmacokinetic data were taken from randomized controlled trials evaluating this area as well as in vitro published results. For validity, only peer-reviewed literature was included. Evidence for sodium channel blockers in chronic pain management was limited. This review focuses on highlighting the data available for the use of sodium channel blockers for certain pain syndromes as well as underutilized potential. Emerging literature on sodium channel subtypes and their connection to neuropathic, inflammatory, and mechanical pain transmission is elucidated. The authors also scrutinize literature surrounding the pharmacokinetics of oxcarbazepine and eslicarbazepine to provide clearer guidance to the significance of any drug interactions and refute assumptions made on the basis of structural similarity to carbamazepine and its known undesirable drug interactions. Side effect profiles are outlined and compared, emphasizing the differences between agents. Sodium channel blocker doses used in certain pain syndromes are outlined with a call for further research to better understand their place in chronic pain management. Identification of sodium channel subtypes with links to specific pain conditions and the ability to target them hints at the potential for truly individualized therapy. Sodium channel inhibitors are underutilized on the basis of available evidence, and emerging research has identified this area as promising for additional clinical trials to better guide clinical practice.

PERSPECTIVE

This article provides a review of the pharmacology, evidence for pain management, and pharmacokinetics of oxcarbazepine, carbamazepine, and eslicarbazepine. There is a disparity in evidence using sodium channel blockers for pain and this article highlights the potential that is currently underutilized. The authors believe this will catalyze interest for further studies.

Antiepileptic drug monotherapy for epilepsy: a network meta-analysis of individual participant data

BACKGROUND

Epilepsy is a common neurological condition with a worldwide prevalence of around 1%. Approximately 60% to 70% of people with epilepsy will achieve a longer-term remission from seizures, and most achieve that remission shortly after starting antiepileptic drug treatment. Most people with epilepsy are treated with a single antiepileptic drug (monotherapy) and current guidelines from the National Institute for Health and Care Excellence (NICE) in the United Kingdom for adults and children recommend carbamazepine or lamotrigine as first-line treatment for partial onset seizures and sodium valproate for generalised onset seizures; however a range of other antiepileptic drug (AED) treatments are available, and evidence is needed regarding their comparative effectiveness in order to inform treatment choices.

OBJECTIVES

To compare the time to withdrawal of allocated treatment, remission and first seizure of 10 AEDs (carbamazepine, phenytoin, sodium valproate, phenobarbitone, oxcarbazepine, lamotrigine, gabapentin, topiramate, levetiracetam, zonisamide) currently used as monotherapy in children and adults with partial onset seizures (simple partial, complex partial or secondary generalised) or generalised tonic-clonic seizures with or without other generalised seizure types (absence, myoclonus).

SEARCH METHODS

We searched the following databases: Cochrane Epilepsy's Specialised Register, CENTRAL, MEDLINE and SCOPUS, and two clinical trials registers. We handsearched relevant journals and contacted pharmaceutical companies, original trial investigators, and experts in the field. The date of the most recent search was 27 July 2016.

SELECTION CRITERIA

We included randomised controlled trials of a monotherapy design in adults or children with partial onset seizures or generalised onset tonic-clonic seizures (with or without other generalised seizure types).

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) review and network meta-analysis. Our primary outcome was 'time to withdrawal of allocated treatment', and our secondary outcomes were 'time to achieve 12-month remission', 'time to achieve six-month remission', 'time to first seizure post-randomisation', and 'occurrence of adverse events'. We presented all time-to-event outcomes as Cox proportional hazard ratios (HRs) with 95% confidence intervals (CIs). We performed pairwise meta-analysis of head-to-head comparisons between drugs within trials to obtain 'direct' treatment effect estimates and we performed frequentist network meta-analysis to combine direct evidence with indirect evidence across the treatment network of 10 drugs. We investigated inconsistency between direct estimates and network meta-analysis via node splitting. Due to variability in methods and detail of reporting adverse events, we have not performed an analysis. We have provided a narrative summary of the most commonly reported adverse events.

MAIN RESULTS

IPD was provided for at least one outcome of this review for 12,391 out of a total of 17,961 eligible participants (69% of total data) from 36 out of the 77 eligible trials (47% of total trials). We could not include IPD from the remaining 41 trials in analysis for a variety of reasons, such as being unable to contact an author or sponsor to request data, data being lost or no longer available, cost and resources required to prepare data being prohibitive, or local authority or country-specific restrictions.We were able to calculate direct treatment effect estimates for between half and two thirds of comparisons across the outcomes of the review, however for many of the comparisons, data were contributed by only a single trial or by a small number of participants, so confidence intervals of estimates were wide.Network meta-analysis showed that for the primary outcome 'Time to withdrawal of allocated treatment,' for individuals with partial seizures; levetiracetam performed (statistically) significantly better than both current first-line treatments carbamazepine and lamotrigine; lamotrigine performed better than all other treatments (aside from levetiracetam), and carbamazepine performed significantly better than gabapentin and phenobarbitone (high-quality evidence). For individuals with generalised onset seizures, first-line treatment sodium valproate performed significantly better than carbamazepine, topiramate and phenobarbitone (moderate- to high-quality evidence). Furthermore, for both partial and generalised onset seizures, the earliest licenced treatment, phenobarbitone seems to perform worse than all other treatments (moderate- to high-quality evidence).Network meta-analysis also showed that for secondary outcomes 'Time to 12-month remission of seizures' and 'Time to six-month remission of seizures,' few notable differences were shown for either partial or generalised seizure types (moderate- to high-quality evidence). For secondary outcome 'Time to first seizure,' for individuals with partial seizures; phenobarbitone performed significantly better than both current first-line treatments carbamazepine and lamotrigine; carbamazepine performed significantly better than sodium valproate, gabapentin and lamotrigine. Phenytoin also performed significantly better than lamotrigine (high-quality evidence). In general, the earliest licenced treatments (phenytoin and phenobarbitone) performed better than the other treatments for both seizure types (moderate- to high-quality evidence).Generally, direct evidence and network meta-analysis estimates (direct plus indirect evidence) were numerically similar and consistent with confidence intervals of effect sizes overlapping.The most commonly reported adverse events across all drugs were drowsiness/fatigue, headache or migraine, gastrointestinal disturbances, dizziness/faintness and rash or skin disorders.

AUTHORS' CONCLUSIONS

Overall, the high-quality evidence provided by this review supports current guidance (e.g. NICE) that carbamazepine and lamotrigine are suitable first-line treatments for individuals with partial onset seizures and also demonstrates that levetiracetam may be a suitable alternative. High-quality evidence from this review also supports the use of sodium valproate as the first-line treatment for individuals with generalised tonic-clonic seizures (with or without other generalised seizure types) and also demonstrates that lamotrigine and levetiracetam would be suitable alternatives to either of these first-line treatments, particularly for those of childbearing potential, for whom sodium valproate may not be an appropriate treatment option due to teratogenicity.

WITHDRAWN: Oxcarbazepine add-on for drug-resistant partial epilepsy

BACKGROUND

Most people with epilepsy have a good prognosis and their seizures can be well controlled with the use of a single antiepileptic drug, but up to 30% develop refractory epilepsy, especially those with partial seizures. In this review we summarize the current evidence regarding oxcarbazepine when used as an add-on treatment for drug-resistant partial epilepsy.

OBJECTIVES

To evaluate the effects of oxcarbazepine when used as an add-on treatment for drug-resistant partial epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group's Specialized Register (28 March 2006), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2006), MEDLINE (1966 to March 2006). No language restrictions were imposed. We checked the reference lists of retrieved studies for additional reports of relevant studies. We also contacted Novartis (manufacturers of oxcarbazepine) and experts in the field.

SELECTION CRITERIA

Randomized, placebo-controlled, double-blinded, add-on trials of oxcarbazepine in patients with drug-resistant partial epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and extracted the relevant data. The following outcomes were assessed : (a) 50% or greater reduction in seizure frequency; (b) treatment withdrawal (any reason); (c) side effects. Primary analyses were intention-to-treat. Summary odds ratios were estimated for each outcome.

MAIN RESULTS

Two trials were included representing 961 randomized patients.Overall Odds Ratio (OR) (95% Confidence Interval (CIs)) for 50% or greater reduction in seizure frequency compared to placebo 2.96 (2.20, 4.00).Treatment withdrawal OR (95% CIs) compared to placebo 2.17 (1.59, 2.97).Side effects: OR (99% CIs) compared to placebo, ataxia 2.93 (1.72, 4.99); dizziness 3.05 (1.99, 4.67); fatigue 1.80 (1.02, 3.19); nausea 2.88 (1.77, 4.69); somnolence 2.55 (1.84, 3.55); diplopia 4.32 (2.65, 7.04), were significantly associated with oxcarbazepine.

AUTHORS' CONCLUSIONS

Oxcarbazepine has efficacy as an add-on treatment in patients with drug-resistant partial epilepsy, both in adults and children. However, trials reviewed were of relatively short duration, and provide no evidence about the long-term effects of oxcarbazepine. Results cannot be extrapolated to monotherapy or to patients with other epilepsy types.

Effects of pharmacological treatments on hippocampal NCAM1 and ERK2 expression in epileptic rats with cognitive dysfunction

The present study aimed to investigate the effects of various pharmacological agents on the hippocampal expression of neural cell adhesion molecule 1 (NCAM1) and extracellular signal-regulated kinase 2 (ERK2) in epileptic rats with cognitive dysfunction. The experiments were conducted using 120 Wistar rats: 20 controls and 100 with pilocarpine-induced status epilepticus (SE). The SE rats were randomly assigned to 5 groups (n=20/group) that received daily treatments for 1 month with one of the following: (i) saline (no effect on epilepsy); (ii) carbamazepine (an anticonvulsant); (iii) oxcarbazepine (an anticonvulsant); (iv) aniracetam (a nootropic); or (v) donepezil (an acetylcholinesterase inhibitor). Spatial learning and memory were assessed using a Morris Water Maze (MWM). Hippocampal tissue was assessed for NCAM1 and ERK2 messenger RNA (mRNA) expression by reverse transcription polymerase chain reaction, and protein expression by immunochemistry. The results revealed that SE rats had significantly poorer MWM performances compared with controls (P<0.01). Performance in SE rats was improved with donepezil treatment (P<0.01), but declined with carbamazepine (P<0.01). Compared with controls, saline-treated SE rats exhibited increased hippocampal NCAM1 mRNA expression (P<0.01). Among SE rats, NCAM1 mRNA expression was highest in those treated with donepezil, followed by aniracetam-, saline-, oxcarbazepine- and carbamazepine-treated rats. Compared to controls, saline-treated SE rats exhibited decreased hippocampal ERK2 mRNA expression (P<0.01). Among SE rats, ERK2 mRNA expression was highest in those treated with donepezil, followed by aniracetam, saline, oxcarbazepine and carbamazepine. NCAM1 and ERK2 protein expression levels were parallel to those of the mRNA. In saline-treated SE rats, hippocampal ERK2 expression was decreased and NCAM1 expression was increased; thus, these two molecules may be involved in the impairment of spatial memory. Carbamazepine augmented this impairment, whereas donepezil was found to ameliorate the dysfunction associated with epilepsy. In conclusion, ERK2 and NCAM1 have significant roles in impairment of spatial memory in SE rats. Carbamazepine may increase this impairment, while donepezil may decrease this impairment.

Oxcarbazepine extended-release formulation in epilepsy

Oxcarbazepine (OXC) is a 10-keto-analogue of carbamazepine, which was developed and labeled as a follow-up antiepileptic drug, that was intended to overcome some of the pharmacological drawbacks of carbamazepine with similar efficacy. The main advantage is the nonoxidative metabolic pathway that allows a lower enzyme-induction profile and fewer drug interactions. OXC is rapidly and extensively reduced by cytosolic hepatic enzymes to its monohydroxylated derivative (MHD), thus OXC may be regarded as a prodrug with MHD representing the active antiepileptic agent. The immediate-release (IR) formulation of OXC (Trileptal(®), Timox(®)) has an almost complete bioavailibilty. It is rapidly absorbed and reaches peak concentrations after 1-3 h. MHD peak concentrations are measured within 4-12 h. Elimination half-life in healthy subjects is 1-5 h for OXC and 7-20 h for MHD. The OXC plasma concentration peak may have been responsible for side effects, such as dizziness, vertigo, coordination problems or blurred vision, which appeared more often with this formulation in individual cases than with the formulation available prior to 2000, or with another formulation that has been distributed in Scandinavian countries. Both possibilities offer a profile approaching the characteristics of an extended-release (ER) formulation. ER OXC was labeled in Germany in 2008 (Apydan(®) extent, Desitin Arzneimittel GmbH, Hamburg, Germany). Under steady-state conditions, Phase I studies show bioequivalence between IR and ER OXC. With ER OXC, OXC plasma peak concentrations and both OXC and MHD peak-trough fluctuations are markedly reduced. In clinical trials, comparisons between IR OXC twice daily versus ER OXC once daily failed to show significant differences; efficacy tended to be better with IR OXC, whereas OXC ER showed insignificant tolerability advantages. Another study is currently ongoing to compare the tolerability of both formulations under twice-daily administration conditions in patients with difficult-to-treat epilepsies who require a dosage increase of OXC and who are randomized to IR or ER OXC.

Palladacycle-catalyzed cascade reaction of bicyclic alkenes with alkynyl imines: synthesis of polycyclic 5H-benzo[b]azepines

A new methodology to prepare a six–seven membered ring [4,5,0] heterobicyclic system has been developed via a palladacycle-catalyzed cascade reaction of bicyclic alkenes and alkynyl imines.

Complementation of biotransformations with chemical C-H oxidation: copper-catalyzed oxidation of tertiary amines in complex pharmaceuticals

The isolation, quantitation, and characterization of drug metabolites in biological fluids remain challenging. Rapid access to oxidized drugs could facilitate metabolite identification and enable early pharmacology and toxicity studies. Herein, we compared biotransformations to classical and new chemical C-H oxidation methods using oxcarbazepine, naproxen, and an early compound hit (phthalazine 1). These studies illustrated the low preparative efficacy of biotransformations and the inability of chemical methods to oxidize complex pharmaceuticals. We also disclose an aerobic catalytic protocole (CuI/air) to oxidize tertiary amines and benzylic CH's in drugs. The reaction tolerates a broad range of functionalities and displays a high level of chemoselectivity, which is not generally explained by the strength of the C-H bonds but by the individual structural chemotype. This study represents a first step toward establishing a chemical toolkit (chemotransformations) that can selectively oxidize C-H bonds in complex pharmaceuticals and rapidly deliver drug metabolites.

Titrimetric and spectrophotometric assay of oxcarbazepine in pharmaceuticals using N-bromosuccinimide and bromopyrogallol red

Titrimetric and spectrophotometric methods are described for the determination of oxcarbazepine (OXC) in bulk drug and in tablets. The methods use N-bromosuccinimide (NBS) and bromopyrogallol red (BPR) as reagents. In titrimetry (method A), an acidified solution of OXC is titrated directly with NBS using methyl orange as indicator. Spectrophotometry (method B) involves the addition of known excess of NBS to an acidified solution of OXC followed by the determination of the unreacted NBS by reacting with BPR and measuring the absorbance of the unreacted dye at 460 nm. Titrimetry allows the determination of 6–18 mg of OXC and follows a reaction stoichiometry of 1 : 1 (OXC : NBS), whereas spectrophotometry is applicable over the concentration range of 0.8–8.0 μg mL⁻¹. Method B with a calculated molar absorptivity of 2.52 × 10⁴ L mol⁻¹ cm⁻¹ is the most sensitive spectrophotometric method ever developed for OXC. The optical characteristics such as limits of detection (LOD), quantification (LOQ), and Sandell's sensitivity values are also reported for the spectrophotometric method. The accuracy and precision of the methods were studied on intraday and interday basis. The methods described could usefully be applied to routine quality control of tablets containing OXC. No interference was observed from common pharmaceutical adjuvants. Statistical comparison of the results with a reference method shows an excellent agreement and indicates no significant difference in accuracy and precision. The reliability of the methods was further ascertained by recovery studies in standard addition procedure.

Newer Anticonvulsant Drugs in Neuropathic Pain and Bipolar Disorder

Older anticonvulsants have been used to manage both chronic pain and bipolar disorders. As the armamentarium of anticonvulsants increases, the role of the newer agents for pain or mood disorders is uncertain. This paper summarizes the clinical data available with gabapentin, lamotrigine, oxcarbazepine, tiagabine and topiramate for bipolar disorder and lamotrigine, oxcarbazepine, tiagabine and topiramate for neuropathic pain.

Evaluation of bone turnover in epileptic children using oxcarbazepine

This study evaluated the effects of oxcarbazepine monotherapy on bone turnover in prepubertal and pubertal children. Thirty-four newly diagnosed pediatric patients with normal bone mineral density, serum biochemical markers of bone formation, and hormonal markers participated. Levels of 25-hydroxyvitamin D were significantly decreased after therapy compared with baseline values. Levels of gamma-glutamyl transferase, phosphorus, alkaline phosphatase, osteocalcin, parathyroid hormone, and calcitonin had increased. However, only changes in osteocalcin and gamma-glutamyl transferase levels were statistically significant compared with baseline values. Drug-induced osteopenia was evident in 3 patients with z scores of bone-mineral density less than -2.0, whereas these patients had z scores of less than -1.5 before treatment. Although 18 months of oxcarbazepine treatment exerted slightly adverse effects on bone metabolism, the effect seems insignificant in children with normal bone-mineral density. Although alterations in bone metabolism do not always suffice to explain the decrease in bone-mineral metabolism, we think that patients with osteopenia before the initiation of oxcarbazepine therapy should be followed carefully, especially in long-term treatment.

The effectiveness of anticonvulsants in psychiatric disorders

Anticonvulsant drugs are widely used in psychiatric indications. These include mainly alcohol and benzodiazepine withdrawal syndromes, panic and anxiety disorders, dementia, schizophrenia, affective disorders, bipolar affective disorders in particular, and, to some extent, personality disorders, A further area in which neurology and psychiatry overlap is pain conditions, in which some anticonvulsants, and also typical psychiatric medications such as antidepressants, are helpful. From the beginning of their psychiatric use, anticonvulsants have also been used to ameliorate specific symptoms of psychiatric disorders independently of their causality and underlying illness, eg, aggression, and, more recently, cognitive impairment, as seen in affective disorders and schizophrenia. With new anticonvulsants currently under development, it is likely that their use in psychiatry will further increase, and that psychiatrists need to learn about their differential efficacy and safety profiles to the same extent as do neurologists.

Oxcarbazepine monotherapy in carbamazepine-unresponsive trigeminal neuralgia

The objective of this prospective open-label study was to evaluate the efficacy and tolerability of oxcarbazepine in trigeminal neuralgia (TN) unresponsive to treatment with the standard antiepileptic drug, carbamazepine. Thirty-five patients with idiopathic TN, who underwent treatment with oxcarbazepine monotherapy for at least 12 weeks, were studied. Pain was assessed using mean pain frequency, responder rate, pain-free patients and clinical global impression. The mean maintenance dose was 773.7 mg/day. There was a significant decrease in the mean of the main scores following 12 weeks of treatment (p<0.05) compared with baseline. Oxcarbazepine was effective from the first month of treatment. There was a significant reduction in pain frequency, leading to improvements in patient satisfaction. In general, oxcarbazepine was well tolerated. Oxcarbazepine appears to be an important alternative therapeutic approach for patients affected by TN. This study adds to the existing literature arriving at the same findings.

Interference by carbamazepine and oxcarbazepine with serum- and urine-screening assays for tricyclic antidepressants

OBJECTIVE

The purpose of this work was to evaluate the potential cross-reactivity of 2 antiepileptic medications containing 3-ringed structures, namely, carbamazepine and oxcarbazepine, with screening assays for tricyclic antidepressants.

METHODS

A cross-sectional study of 52 patients between 3 and 19 years of age who had been prescribed either carbamazepine or oxcarbazepine was conducted. A serum fluorescence-polarized immunoassay and a urine enzyme-linked immunoassay were used. The serum carbamazepine or oxcarbazepine level was measured. Gas chromatography/mass spectrometry, a confirmatory test for tricyclic antidepressant detection, was subsequently performed on the serum specimen.

RESULTS

A linear dependency on medication level was observed with the serum fluorescence-polarized immunoassay assay. This relationship was stronger for carbamazepine (4.2 microg/L tricyclic antidepressant detected per microgram/liter of carbamazepine) than for oxcarbazepine (0.7 microg/L tricyclic antidepressant detected per milligram/liter). At higher carbamazepine levels (8.0-11.6 mg/L), 12 of 13 patients had a positive serum fluorescence-polarized immunoassay result; at lower levels (0.1-7.9 mg/L), only 1 of 20 had a positive result. None of the patients who were receiving oxcarbazepine showed significant tricyclic antidepressant activity on either assay.

CONCLUSIONS

Carbamazepine interferes at a statistically significant level with serum fluorescence-polarized immunoassay assay and in a dose-dependent fashion. Neither carbamazepine nor oxcarbazepine exhibit significant tricyclic antidepressant activity on urine enzyme-linked immunoassay assay.

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.

Anti-convulsants and anti-depressants

Damage to a nerve should only lead to sensory loss. While this is common, the incidence of spontaneous pain, allodynia and hyperalgesia indicate marked changes in the nervous system that are possible compensations for the loss of normal function that arises from the sensory loss. Neuropathic pain arises from changes in the damaged nerve which then alter function in the spinal cord and the brain and lead to plasticity in areas adjacent to those directly influenced by the neuropathy. The peripheral changes drive central compensations so that the mechanisms involved are multiple and located at a number of sites. Nerve damage increases the excitability of both the damaged and undamaged nerve fibres, neuromas and the cell bodies in the dorsal root ganglion. These peripheral changes are substrates for the ongoing pain and the efficacy of excitability blockers such as carbamazepine, lamotrigine and mexiletine, all anti-convulsants. A better understanding of ion channels at the sites of injury has shown important roles of particular sodium, potassium and calcium channels in the genesis of neuropathic pain. Within the spinal cord, increases in the activity of calcium channels and the receptors for glutamate, especially the N-methyl-D-aspartate (NMDA) receptor, trigger wind-up and central hyperexcitability. Increases in transmitter release, neuronal excitability and receptive field size result from the damage to the peripheral nerves. Ketamine and gabapentin/pregabalin, again with anti-convulsant activity, may interact with these mechanisms. Ketamine acts on central spinal mechanisms of excitability whereas gabapentin acts on a subunit of calcium channels that is responsible for the release of pain transmitters into the spinal cord. In addition to these spinal mechanisms of hyperexcitability, spinal cells participate in a spinal-supraspinal loop that involves parts of the brain involved in affective responses to pain but also engages descending excitatory and inhibitory systems that use the monoamines. These pathways become more active after nerve injury and are the site of action of anti-depressants. This chapter reviews the evidence and mechanisms of drugs, both anti-depressants and anti-convulsants, that are believed to be effective in pain control, with a major emphasis on the neuropathic state.

Development and validation of a high performance liquid chromatographic method for the determination of oxcarbazepine and its main metabolites in human plasma and cerebrospinal fluid and its application to pharmacokinetic study

An isocratic reversed-phase HPLC-UV procedure for the determination of oxcarbazepine and its main metabolites 10-hydroxy-10,11-dihydrocarbamazepine and 10,11-dihydroxy-trans-10,11-dihydrocarbamazepine in human plasma and cerebrospinal fluid has been developed and validated. After addition of bromazepam as internal standard, the analytes were isolated from plasma and cerebrospinal fluid by liquid-liquid extraction. Separation was achieved on a X-TERRA C18 column using a mobile phase composed of 20 mM KH(2)PO(4), acetonitrile, and n-octylamine (76:24:0.05, v/v/v) at 40 degrees C and detected at 237 nm. The described assay was validated in terms of linearity, accuracy, precision, recovery and lower limit of quantification according to the FDA validation guidelines. Calibration curves were linear with a coefficient of variation (r) greater than 0.998. Accuracy ranged from 92.3% to 106.0% and precision was between 2.3% and 8.2%. The method has been applied to plasma and cerebrospinal fluid samples obtained from patients treated with oxcarbazepine, both in monotherapy and adjunctive therapy.