Safety and efficacy of oxcarbazepine: results of randomized, double-blind trials

Effect of clinical features on antiseizure medication doses in patients with newly diagnosed epilepsy

Objective

We evaluate the effect of distinct clinical features on anti-seizure medication (ASM) doses in seizure-free and not seizure-free patients aged ≥16 years with new-onset epilepsy.

Materials and methods

This study included 459 patients with a validated diagnosis of epilepsy. The most prescribed ASMs were oxcarbazepine (OXC; n = 307), followed by valproic acid (VPA; n = 115), carbamazepine (CBZ; n = 81), and lamotrigine (LTG; n = 67). The seizure freedom rate with their first or subsequent ASM was 88.0%. A retrospective analysis of patient records was performed to determine any association between doses of ASMs and patient characteristics.

Results

The median OXC dose in seizure-free patients aged >60 years was 600 mg compared to 900 mg in younger patients. When controlling for age but not in an unadjusted model, the median dose of OXC was lower (300 mg, p = 0.018) for seizure-free patients compared to non-seizure-free patients, and the median dose of OXC was also 300 mg lower among older patients aged >60 years (p < 0.001). The median OXC doses for men aged ≤60 years were 300 mg higher than for women aged >60 years (900 mg vs. 600 mg, p = 0.021). The median dose of VPA was 400 mg higher in men than in women (p < 0.001) and 400 mg higher in not seizure-free patients compared to seizure-free patients only when adjusting for sex (p < 0.001). Higher median doses for CBZ were registered with FAS compared with FBTCS (difference in median doses of 200 mg; p = 0.017).

Conclusion

Significant OXC dose differences were detected between age groups, whereas VPA dosing was different in men and women. Moreover, CBZ doses were dependent on some seizure types. These data allow for the individualization of the initial target dosing based on key clinical characteristics.

Pharmacotherapeutic management of trigeminal neuropathic pain: an update

INTRODUCTION

Guidelines recommend a number of pharmacotherapeutic options used as monotherapy or in combination with others for treating the pain of trigeminal neuropathy.

AREAS COVERED

The authors examine the pharmacotherapeutic options for treating trigeminal neuralgia and supporting evidence in the literature. Guidelines reported the most effective treatment for trigeminal neuropathy, in particular trigeminal neuralgia, appears to be carbamazepine or oxcabazepine, but side effects can be treatment limiting. Lamotrigine and gabapentin are also recommended in guidance. In real-world clinical practice, baclofen, cannabinoids, eslicarbazepine, levetiracetam, brivaracetam, lidocaine, misoprostol, opioids, phenytoin, fosphenytoin, pimozide, sodium valproate, sumatriptan, tizanidine, tocainide, tricyclic antidepressants, and vixotrigine are sometimes used, either as monotherapy or in combination. The relatively small patient population has limited the number of large-scale studies and there is limited evidence on which to base prescribing choices.

EXPERT OPINION

While there is no optimal pharmacotherapy for treating trigeminal neuropathy, advancements in our understanding of the underlying mechanisms of this condition and drug development indicate promise for NaV inhibitors, despite the fact that not all patients respond to them and they may have potentially treatment-limiting side effects. Nevertheless, better understanding of NaV channels may be important avenues for future drug development for trigeminal neuropathy.

Effects of genetic polymorphism of drug-metabolizing enzymes on the plasma concentrations of antiepileptic drugs in Chinese population

As a chronic brain disease, epilepsy affects ~50 million people worldwide. The traditional antiepileptic drugs (AEDs) are widely applied but showing various problems. Although the new AEDs have partially solved the problems of traditional AEDs, the current clinical application of traditional AEDs are not completely replaced by new drugs, particularly due to the large individual differences in drug plasma concentrations and narrow therapeutic windows among patients. Therefore, it is still clinically important to continue to treat patients using traditional AEDs with individualized therapeutic plans. To date, our understanding of the molecular and genetic mechanisms regulating plasma concentrations of AEDs has advanced rapidly, expanding the knowledge on the effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of AEDs. It is increasingly imperative to summarize and conceptualize the clinical significance of recent studies on individualized therapeutic regimens. In this review, we extensively summarize the critical effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of several commonly used AEDs as well as the clinical significance of testing genotypes related to drug metabolism on individualized drug dosage. Our review provides solid experimental evidence and clinical guidance for the therapeutic applications of these AEDs.

Chronic oxcarbazepine intoxication in a patient with primary antiphospholipid syndrome on maintenance haemodialysis

WHAT IS KNOWN AND OBJECTIVE

Oxcarbazepine (OXC) is an antiepileptic drug. Patients suffering from chronic kidney disease with an estimated glomerular filtration rate below 30 ml/min/1.73 m² require dose adjustments for OXC.

CASE SUMMARY

A 31-year-old man was admitted with a history of diplopia, ataxia and dizziness attacks that had disappeared after a regular haemodialysis sessions for three months. Medical history was remarkable for primary antiphospholipid syndrome (APS). However, no signs of new-onset APS-related neurological involvement were present. Then, it was revealed that the patient had been using 2400 mg/day of OXC for four months, despite the prescription of half of this dose. Serum OXC level was 50 mcg/ml (reference: 3-35 mcg/ml) before a regular haemodialysis session. All symptoms disappeared in a few days after reducing to 1200 mg/day and never recurred.

WHAT IS NEW AND CONCLUSION

We reported a chronic OXC intoxication in a patient on maintenance haemodialysis. To the best of our knowledge, it is the first chronic OXC intoxication case in the literature. It could be related to episodic removal of OXC and its metabolites via haemodialysis. Consequently, dose modification of drugs is a pivotal point in haemodialysis patients. Chronic drug intoxications must be kept in mind in haemodialysis patients with unexplained symptoms.

SCN8A Encephalopathy: Case Report and Literature Review

Epileptic encephalopathy is a condition resulting from extreme forms of intractable childhood epilepsy. The disease can cause severe delays in cognitive, sensory, and motor function development, in addition to being fatal in some cases. Missense mutations of SCN8A, which encodes Nav1.6, one of the main voltage-gated sodium channel subunits in neurons and muscles, have been linked to early infantile SCN8A encephalopathy. Herein, we report the case of a 5-month-old girl with SCN8A encephalopathy with a novel missense mutation. Apart from intractable seizures and autistic phenotypes, the results of blood and biochemical tests, electroencephalogram (EEG) results, and brain magnetic resonance imaging (MRI) results were all normal. As the phenotypes caused by these mutations cannot be identified by any clinical, neuroimaging, or electrophysiological features, genetic sequencing should be considered to identify the underlying genetic causes. Although phenytoin is recommended as a last-resort treatment for SCN8A encephalopathy, the administration of the oxcarbazepine, instead of phenytoin, mitigated this patient's intractable seizures.

Trigeminal neuralgia: An overview from pathophysiology to pharmacological treatments

The trigeminal nerve (V) is the fifth and largest of all cranial nerves, and it is responsible for detecting sensory stimuli that arise from the craniofacial area. The nerve is divided into three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3); their cell bodies are located in the trigeminal ganglia and they make connections with second-order neurons in the trigeminal brainstem sensory nuclear complex. Ascending projections via the trigeminothalamic tract transmit information to the thalamus and other brain regions responsible for interpreting sensory information. One of the most common forms of craniofacial pain is trigeminal neuralgia. Trigeminal neuralgia is characterized by sudden, brief, and excruciating facial pain attacks in one or more of the V branches, leading to a severe reduction in the quality of life of affected patients. Trigeminal neuralgia etiology can be classified into idiopathic, classic, and secondary. Classic trigeminal neuralgia is associated with neurovascular compression in the trigeminal root entry zone, which can lead to demyelination and a dysregulation of voltage-gated sodium channel expression in the membrane. These alterations may be responsible for pain attacks in trigeminal neuralgia patients. The antiepileptic drugs carbamazepine and oxcarbazepine are the first-line pharmacological treatment for trigeminal neuralgia. Their mechanism of action is a modulation of voltage-gated sodium channels, leading to a decrease in neuronal activity. Although carbamazepine and oxcarbazepine are the first-line treatment, other drugs may be useful for pain control in trigeminal neuralgia. Among them, the anticonvulsants gabapentin, pregabalin, lamotrigine and phenytoin, baclofen, and botulinum toxin type A can be coadministered with carbamazepine or oxcarbazepine for a synergistic approach. New pharmacological alternatives are being explored such as the active metabolite of oxcarbazepine, eslicarbazepine, and the new Nav1.7 blocker vixotrigine. The pharmacological profiles of these drugs are addressed in this review.

Advances in diagnosis, classification, pathophysiology, and management of trigeminal neuralgia

Trigeminal neuralgia is a very painful neurological condition with severe, stimulus-evoked, short-lasting stabbing pain attacks in the face. The past decade has offered new insights into trigeminal neuralgia symptomatology, pathophysiology, and treatment, leading to a change in the classification of the condition. An accurate diagnosis is crucial because neuroimaging interpretation and clinical management differ among the various forms of facial pain. MRI using specific sequences should be a part of the diagnostic workup to detect a possible neurovascular contact and exclude secondary causes. Demonstration of a neurovascular contact should not be used to confirm a diagnosis but rather to facilitate surgical decision making. Carbamazepine and oxcarbazepine are drugs of first choice for long-term treatment, whereas microvascular decompression is the first-line surgery in medically refractory patients. Advances in neuroimaging techniques and animal models will provide further insight into the causes of trigeminal neuralgia and its pathophysiology. Development of more efficacious treatment options is highly warranted.

Accurate and simple determination of oxcarbazepine in human plasma and urine samples using switchable-hydrophilicity solvent in GC-MS

This work presents a sensitive and rapid analytical method for the determination of oxcarbazepine in human plasma and urine samples. A vortex-assisted switchable hydrophilicity solvent-based liquid phase microextraction (VA-SHS-LPME) was used to preconcentrate oxcarbazepine from the samples before the determination by gas chromatography mass spectrometry. The switchable hydrophilicity solvent was synthesized by protonating N,N-dimethylbenzylamine with carbon dioxide to make it totally miscible with an equivalent volume of water. Parameters of the VA-SHS-LPME method including volume of switchable hydrophilicity solvent, concentration/volume of sodium hydroxide and vortex period were systematically optimized. Under the optimum conditions, good linearity ranging from 27.03 to 353.47 μg/kg was obtained for the analyte. Limit of detection and quantitation values were found to be 6.2 and 21 μg/kg (mass base), respectively. The relative standard deviation was calculated as 6.9% for six replicate measurements of the lowest concentration of the calibration plot. Satisfactory recovery results were calculated in the range of 97-100% for human plasma and urine samples spiked at five different concentrations.

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.

Update on Trigeminal Neuralgia

PURPOSE OF REVIEW

To review current treatments for trigeminal neuralgia, with an emphasis on determining which patients may benefit from neurosurgical procedures.

RECENT FINDINGS

A detailed history is the most helpful tool for diagnosing trigeminal neuralgia (TN) and predicting response to neurosurgical treatments. Patients with classic trigeminal neuralgia will describe severe, unilateral, intermittent facial pain that is triggered by innocuous sensory stimuli. In most cases, pain is caused by compression of the trigeminal nerve by a blood vessel near the brainstem. Magnetic resonance imaging is necessary to rule out TN secondary to multiple sclerosis or tumor. Modern high-resolution T2 images may demonstrate neurovascular contact, particularly when analyzed by a neurosurgeon with expertise in TN. Initial management involves a trial of medication, usually carbamazepine or oxcarbazepine. Microvascular decompression (MVD) is safe and effective surgery, for patients with classic TN related to neurovascular compression. For patients with TN secondary to multiple sclerosis, and for patients who are otherwise poor candidates for MVD, neurosurgical options include percutaneous trigeminal rhizotomy and radiosurgery. Neurosurgical procedures are less effective in relieving atypical facial pain. In the clinical evaluation of a patient with facial pain, it is important to distinguish classic trigeminal neuralgia from atypical facial pain. A patient with classic trigeminal neuralgia would benefit from neurosurgical consultation. The advent of high-resolution MRI and MRA sequences now allows a neurosurgeon to detect when neurovascular compression is likely, and select the optimal procedure for treatment.

Recent advances in understanding/managing trigeminal neuralgia

Despite recent advances in understanding and treating trigeminal neuralgia, its management remains a considerable challenge. Better classification of different types of facial pain and the identification of prognostic factors for different treatment options lead the way toward better quality of life for the individual patient. Although the principles of treating trigeminal neuralgia remain basically the same, antiepileptic drugs, muscle relaxants, and neuroleptic agents are widely used medical treatment options. They were not originally developed for treating trigeminal neuralgia. Carbamazepine was studied in adequate placebo-controlled clinical trials in the 1960s and is still considered the most effective drug. Among emerging treatment options currently under clinical investigation are local botulinum neurotoxin type A injections and a novel sodium channel blocker (CNV1014802) that selectively blocks the Na _v1.7 sodium channel. Non-pharmacological treatment options are non-invasive electrical stimulation with either transcranial direct-current stimulation or repetitive transcranial magnetic stimulation which both require further evaluation in regard to applicability. Surgical options remain a valid choice for patients not responding to medical treatment and include Gasserian ganglion percutaneous techniques, gamma knife surgery, and microvascular decompression. There is continual effort to improve these techniques and predict the outcome for better patient selection.

Trigeminal neuralgia secondary to multiple sclerosis: from the clinical picture to the treatment options

BACKGROUND

Trigeminal neuralgia is one of the most characteristic and difficult to treat neuropathic pain conditions in patients with multiple sclerosis. The present narrative review addresses the current evidence on diagnostic tests and treatment of trigeminal neuralgia secondary to multiple sclerosis.

METHODS

We searched for relevant papers within PubMed, EMBASE and the Cochrane Database of Systematic Reviews, taking into account publications up to December 2018.

RESULTS

Trigeminal neuralgia secondary to multiple sclerosis manifests with facial paroxysmal pain triggered by typical manoeuvres; neurophysiological investigations and MRI support the diagnosis, providing the definite evidence of trigeminal pathway damage. A dedicated MRI is required to identify pontine demyelinating plaques. In many patients with multiple sclerosis, neuroimaging and surgical evidence suggests that neurovascular compression might act in concert with the pontine plaque through a double-crush mechanism. Although no placebo-controlled trials have been conducted in these patients, according to expert opinion the first-line therapy for trigeminal neuralgia secondary to multiple sclerosis relies on sodium-channel blockers, i.e. carbamazepine and oxcarbazepine. The sedative and motor side effects of these drugs frequently warrant an early consideration for neurosurgery. Surgical procedures include Gasserian ganglion percutaneous techniques, gamma knife radiosurgery and microvascular decompression in the posterior fossa.

CONCLUSIONS

The relatively poor tolerability of the centrally-acting drugs carbamazepine and oxcarbazepine highlights the need to develop new selective and better-tolerated sodium-channel blockers. Prospective studies based on more advanced neuroimaging techniques should focus on how trigeminal anatomical abnormalities may be able to predict the efficacy of microvascular decompression.

Current and Innovative Pharmacological Options to Treat Typical and Atypical Trigeminal Neuralgia

Trigeminal neuralgia is a representative neuropathic facial pain condition, characterised by unilateral paroxysmal pain in the distribution territory of one or more divisions of the trigeminal nerve, triggered by innocuous stimuli. A subgroup of patients with trigeminal neuralgia [TN (previously defined as atypical TN)] also suffer from concomitant continuous pain, i.e. a background pain between the paroxysmal attacks. The aim of this review is to provide current, evidence-based, knowledge about the pharmacological treatment of typical and atypical TN, with a specific focus on drugs in development. We searched for relevant papers within PubMed, EMBASE, the Cochrane Database of Systematic Reviews and the Clinical Trials database (ClinicalTrials.gov), taking into account publications up to February 2018. Two authors independently selected studies for inclusions, data extraction, and bias assessment. Carbamazepine and oxcarbazepine are the first-choice drugs for paroxysmal pain. When sodium channel blockers cannot reach full dosage because of side effects, an add-on treatment with lamotrigine or baclofen should be considered. In patients with atypical TN, both gabapentin and antidepressants are expected to be efficacious and should be tried as an add-on to oxcarbazepine or carbamazepine. Although carbamazepine and oxcarbazepine are effective in virtually the totality of patients, they are responsible for side effects causing withdrawal from treatment in an important percentage of cases. A new, better tolerated, Nav1.7 selective state-dependent, sodium channel blocker (vixotrigine) is under development. Future trials testing the effect of combination therapy in patients with TN are needed, especially in patients with concomitant continuous pain and in TN secondary to multiple sclerosis.

Pharmacological treatment of trigeminal neuralgia

INTRODUCTION

Unique among the different neuropathic pain conditions, trigeminal neuralgia frequently has an excellent response to some selected drugs, which, on the other hand, often entail disabling side effects. Physicians should be therefore acquainted with the management of these drugs and the few alternative options. Areas covered: This article, based on a systematic literature review, describes the pharmacological options, and indicates the future perspectives for treating trigeminal neuralgia. The article therefore provides current, evidence-based knowledge about the pharmacological treatment of trigeminal neuralgia, and suggests a practical approach to the various drugs, including starting dose, titration and side effects. Expert commentary: Carbamazepine and oxcarbazepine are the reference standard drugs for treating patients with trigeminal neuralgia. They are effective in most patients. The undesired effects however cause withdrawal from treatment or a dosage reduction to an insufficient level in many patients. Sodium channel blockers selective for the sodium channel 1.7 (Nav1.7) receptor, currently under development, might be an alternative, better-tolerated pharmacological option in the next future.

Trigeminal neuralgia--a coherent cross-specialty management program

BACKGROUND

Optimal management of patients with classical trigeminal neuralgia (TN) requires specific treatment programs and close collaboration between medical, radiological and surgical specialties. Organization of such treatment programs has never been described before. With this paper we aim to describe the implementation and feasibility of an accelerated cross-speciality management program, to describe the collaboration between the involved specialties and to report the patient flow during the first 2 years after implementation. Finally, we aim to stimulate discussions about optimal management of TN.

METHODS

Based on collaboration between neurologists, neuroradiologists and neurosurgeons a standardized program for TN was implemented in May 2012 at the Danish Headache Center (DHC). First out-patient visit and subsequent 3.0 Tesla MRI scan was booked in an accelerated manner. The MRI scan was performed according to a special TN protocol developed for this program. Patients initially referred to neurosurgery were re-directed to DHC for pre-surgical evaluation of diagnosis and optimization of medical treatment. Follow-up was 2 years with fixed visits where medical treatment and indication for neurosurgery was continuously evaluated. Scientific data was collected in a structured and prospective manner.

RESULTS

From May 2012 to April 2014, 130 patients entered the accelerated program. Waiting time for the first out-patient visit was 42 days. Ninety-four percent of the patients had a MRI performed according to the special protocol after a mean of 37 days. Within 2 years follow-up 35% of the patients were referred to neurosurgery after a median time of 65 days. Five scientific papers describing demographics, clinical characteristics and neuroanatomical abnormalities were published.

CONCLUSION

The described cross-speciality management program proved to be feasible and to have acceptable waiting times for referral and highly specialized work-up of TN patients in a public tertiary referral centre for headache and facial pain. Early high quality MRI ensured correct diagnosis and that the neurosurgeons had a standardized basis before decision-making on impending surgery. The program ensured that referral of the subgroup of patients in need for surgery was standardized, ensured continuous evaluation of the need for adjustments in pharmacological management and formed the basis for scientific research.

Update on neuropathic pain treatment for trigeminal neuralgia. The pharmacological and surgical options

Trigeminal neuralgia is a syndrome of unilateral, paroxysmal, stabbing facial pain, originating from the trigeminal nerve. Careful history of typical symptoms is crucial for diagnosis. Most cases are caused by vascular compression of the trigeminal root adjacent to the pons leading to focal demyelination and ephaptic axonal transmission. Brain imaging is required to exclude secondary causes. Many medical and surgical treatments are available. Most patients respond well to pharmacotherapy; carbamazepine and oxcarbazepine are first line therapy, while lamotrigine and baclofen are considered second line treatments. Other drugs such as topiramate, levetiracetam, gabapentin, pregabalin, and botulinum toxin-A are alternative treatments. Surgical options are available if medications are no longer effective or tolerated. Microvascular decompression, gamma knife radiosurgery, and percutaneous rhizotomies are most promising surgical alternatives. This paper reviews the medical and surgical therapeutic options for the treatment of trigeminal neuralgia, based on available evidence and guidelines.

Efficacy of low to moderate doses of oxcarbazepine in adult patients with newly diagnosed partial epilepsy

PURPOSE

The objective of this study was to explore the efficacy of low dose of oxcarbazepine (OXC) in adult patients with newly diagnosed partial epilepsy in an actual clinical setting. The associated factors influencing the poor control of seizures were also evaluated.

METHODS

The epilepsy database (2010-2014) from the Epilepsy Clinic of West China Hospital was retrospectively reviewed.

RESULTS

A total of 102 adult patients with newly diagnosed, previously untreated partial epilepsy initially treated with OXC were included, and divided into good response group (64) and poor response group (38) according to whether they were seizure-free for at least 12 months. There were 27 (26.5%) patients becoming seizure-free with OXC 600 mg/day monotherapy. The remaining 75 patients had doses of either increasing OXC to 900 mg/day (n = 59) or the addition of another antiepileptic drug (AED) (n = 16), with another 20 (19.6%) and six (5.9%) patients becoming seizure-free, respectively (P = 0.788). In addition, two (2.0%) and nine (8.8%) patients became seizure-free with OXC > 900 mg/day monotherapy and OXC ≥ 900 mg/day combination therapy, respectively. Multivariate binary logistic regression analysis revealed that the time from onset of epilepsy to treatment initiation is significantly associated with seizure control (P = 0.02).

CONCLUSION

Our results indicated that OXC at low to moderate doses is effective for the treatment of Chinese adult patients with newly diagnosed, previously untreated partial epilepsy, and a longer time interval from the onset of epilepsy to the start of treatment significantly predicts poor seizure control.

Advances in diagnosis and treatment of trigeminal neuralgia

Various drugs and surgical procedures have been utilized for the treatment of trigeminal neuralgia (TN). Despite numerous available approaches, the results are not completely satisfying. The need for more contemporaneous drugs to control the pain attacks is a common experience. Moreover, a number of patients become drug resistant, needing a surgical procedure to treat the neuralgia. Nonetheless, pain recurrence after one or more surgical operations is also frequently seen. These facts reflect the lack of the precise understanding of the TN pathogenesis. Classically, it has been related to a neurovascular compression at the trigeminal nerve root entry-zone in the prepontine cistern. However, it has been evidenced that in the pain onset and recurrence, various neurophysiological mechanisms other than the neurovascular conflict are involved. Recently, the introduction of new magnetic resonance techniques, such as voxel-based morphometry, diffusion tensor imaging, three-dimensional time-of-flight magnetic resonance angiography, and fluid attenuated inversion recovery sequences, has provided new insight about the TN pathogenesis. Some of these new sequences have also been used to better preoperatively evidence the neurovascular conflict in the surgical planning of microvascular decompression. Moreover, the endoscopy (during microvascular decompression) and the intraoperative computed tomography with integrated neuronavigation (during percutaneous procedures) have been recently introduced in the challenging cases. In the last few years, efforts have been made in order to better define the optimal target when performing the gamma knife radiosurgery. Moreover, some authors have also evidenced that neurostimulation might represent an opportunity in TN refractory to other surgical treatments. The aim of this work was to review the recent literature about the pathogenesis, diagnosis, and medical and surgical treatments, and discuss the significant advances in all these fields.

Natural history and outcome of 200 outpatients with classical trigeminal neuralgia treated with carbamazepine or oxcarbazepine in a tertiary centre for neuropathic pain

BACKGROUND

The guidelines on trigeminal neuralgia management that have been agreed and jointly published by the American Academy of Neurology and the European Federation of Neurological Societies recommend carbamazepine (CBZ) and oxcarbazepine (OXC) as the first-choice medical treatments in patients with trigeminal neuralgia (TN). The aim of this retrospective study was to analyze the natural history of classical trigeminal neuralgia in a large cohort of patients, focusing on drug responsiveness, side effects related to CBZ and OXC, and changes in pain characteristics during the course of disease.

FINDINGS

We selected the last 100 consecutive patients with typical TN who began treatment with CBZ and the last 100 with OXC. All had MRI scans and a complete neurophysiological study of trigeminal reflexes. Among them, 22 were excluded on the basis of neuroradiological or neurophysiological investigations, to avoid the inclusion of patients with possible secondary TN. The initial number of responders was 98% with CBZ with a median dose of 600 mg (range 200-1200), and of 94% with OXC, with a median dose of 1200 mg (range 600-1800). In a mean period of 8.6 months, 27% of responders to CBZ incurred in undesired effects to a level that caused interruption of treatment or a dosage reduction to an unsatisfactory level. In a mean period of 13 months, the same occurred to 18% of responders to OXC. Among patients who had a good initial response, only 3 patients with CBZ and 2 with OXC developed late resistance. During the course of disease, paroxysms worsened in intensity in 3% of patients, and paroxysms duration increased in 2%. We did not observe the onset of a clinically manifest sensory deficit at any time in any patient.

CONCLUSIONS

Unlike common notion, in our large patient sample the worsening of pain with time and the development of late resistance only occurred in a very small minority of patients. CBZ and OXC were confirmed to be efficacious in a large majority of patients, but the side effects caused withdrawal from treatment in an important percentage of patients. These results suggest the opportunity to develop a better tolerated drug.

Symptomatic treatment and management of multiple sclerosis

The range of symptoms which occur in multiple sclerosis (MS) can have disabling functional consequences for patients and lead to significant reductions in their quality of life. MS symptoms can also interact with each other, making their management challenging. Clinical trials aimed at identifying symptomatic therapies have generally been poorly designed and have tended to be underpowered. Therefore, the evidence base for the management of MS symptoms with pharmacologic therapies is not strong and tends to rely upon open-label studies, case reports, and clinical trials with small numbers of patients and poorly validated clinical outcome measures. Recently, there has been a growing interest in the management of MS symptoms with pharmacologic treatments, and better-designed, randomized, double-blind, controlled trials have been reported. This chapter will describe the evidence base predominantly behind the various pharmacologic approaches to the management of MS symptoms, which in most, if not all, cases, requires multidisciplinary input. Drugs routinely recommended for individual symptoms and new therapies, which are currently in the development pipeline, will be reviewed. More interventional therapies related to symptoms that are refractory to pharmacotherapy will also be discussed, where relevant.

Trigeminal neuralgia and persistent idiopathic facial pain

Trigeminal neuralgia (TN) and persistent idiopathic facial pain (PIFP) are two of the most puzzling orofacial pain conditions and affected patients are often very difficult to treat. TN is characterized by paroxysms of brief but severe pain followed by asymptomatic periods without pain. In some patients a constant dull background pain may persist. This constant dull pain sometimes makes the distinction from PIFP difficult. PIFP is defined as continuous facial pain, typically localized in a circumscribed area of the face, which is not accompanied by any neurological or other lesion identified by clinical examination or clinical investigations. The pain usually does not stay within the usual anatomic boundaries of the trigeminal nerve distribution and is a diagnosis of exclusion. Epidemiologic evidence on TN, and even more so on PIFP, is quite scarce, but generally both conditions are considered to be rare diseases. The etiology and underlying pathophysiology of TN, and more so PIFP, remain unknown. Treatment is based on only few randomized controlled clinical trials and insufficiently evaluated surgical procedures.

Treating pain in multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an inflammatory, demyelinating, central nervous system disease that frequently causes pain.

AREAS COVERED

This article reviews the current literature and describes the therapeutic options for treating MS-related pain. The reader will be provided with current, evidence-based knowledge about the treatment of MS-related pain, and the review will take a practical approach to the various drugs for treating pain, including starting dose, titration and side effects.

EXPERT OPINION

Only cannabinoids have been assessed in randomized, controlled trials. Because of the concern regarding the risk of abuse and psychiatric adverse events, published guidelines as well as expert recommendations suggest using them as second-line therapy only. Hence, current treatment should be based on the general principles for treating peripheral neuropathic pain, taking into account drug-induced adverse effects.

Treatment options in trigeminal neuralgia

The incidence of trigeminal neuralgia (TN) is 4.3 per 100,000 persons per year, with a slightly higher incidence for women (5.9/100,000) compared with men (3.4/100,000). There is a lack of certainty regarding the aetiology and pathophysiology of TN. The treatment of TN can be very challenging despite the numerous options patients and physicians can choose from. This multitude of treatment options poses the question as to which treatment fits which patient best. The preferred medical treatment for TN consists of anticonvulsant drugs, muscle relaxants and neuroleptic agents. Large-scale placebo-controlled clinical trials are scarce. For patients refractory to medical therapy, Gasserian ganglion percutaneous techniques, gamma knife surgery and microvascular decompression are the most promising invasive treatment options.

Carbamazepine but not valproate induces CYP2A6 activity in smokers with mental illness

BACKGROUND

Antiepileptic drugs (AED) are being increasingly used in the management of serious mental illness, but their effects on nicotine metabolism have not been studied.

METHODS

This study investigated the effects of three AEDs (carbamazepine, oxcarbazepine, and valproic acid) on nicotine and nicotine metabolite levels in 149 smokers with schizophrenia and bipolar disorder who participated in an afternoon blood draw for nicotine, cotinine, and 3'-hydroxycotinine (3HC). The ratio of 3HC to cotinine was calculated as a marker of CYP2A6 metabolic activity. Among the participants, 8 smokers were taking carbamazepine, 6 were taking oxcarbazepine, and 40 were taking valproic acid.

RESULTS

The 3HC/cotinine ratio was significantly higher in individuals taking carbamazepine or oxcarbazepine (combined, n = 14) versus those not taking either (mean 0.993 versus 0.503; P < 0.001). The cotinine/cigarette per day ratio was significantly lower in individuals taking carbamazepine or oxcarbazepine. The 3HC/cotinine ratios were also significantly higher in the subgroup of individuals taking carbamazepine (n = 8) versus those not taking it. There were no significant differences in nicotine or cotinine levels or 3HC/cotinine ratios in individuals taking valproic acid versus those not taking it. We conducted backward stepwise linear regression models to identify predictors of the log transformed 3HC/cotinine ratios. Taking carbamazepine and number of cigarettes smoked per day were significant determinants of log 3HC/cotinine.

CONCLUSIONS

Carbamazepine likely induces hepatic metabolism via CYP2A6 and is associated with increased 3HC/cotinine ratios.

IMPACT

Increased nicotine metabolism in individuals using AED has implications for increased smoking behavior and exposure to more tobacco toxins, which warrants further study.

Update on trigeminal neuralgia

Trigeminal neuralgia leads to paroxysms of short-lasting but very severe pain. Between attacks, patients are usually asymptomatic, but a constant dull background pain may persist in some cases. The incidence of trigeminal neuralgia is 4.3 per 100,000 persons per year, with a slightly higher incidence for women (5.9 per 100,000) compared with men (3.4 per 100,000). There is a lack of certainty regarding the etiology and pathophysiology of trigeminal neuralgia. There are a wide range of medical and surgical treatments available. The preferred medical treatment for trigeminal neuralgia consists of anticonvulsant drugs, muscle relaxants and neuroleptic agents. Large-scaled placebo-controlled clinical trials are scarce. For patients refractory to medical therapy, Gasserian ganglion percutaneous techniques, gamma-knife surgery and microvascular decompression are the most promising invasive treatment options. Continuous scientific research works towards a better understanding of trigeminal neuralgia and has accomplished a greater insight into the underlying pathophysiological mechanisms.

AAN-EFNS guidelines on trigeminal neuralgia management

Several issues regarding diagnosis, pharmacological treatment, and surgical treatment of trigeminal neuralgia (TN) are still unsettled. The American Academy of Neurology and the European Federation of Neurological Societies launched a joint Task Force to prepare general guidelines for the management of this condition. After systematic review of the literature the Task Force came to a series of evidence-based recommendations. In patients with TN MRI may be considered to identify patients with structural causes. The presence of trigeminal sensory deficits, bilateral involvement, and abnormal trigeminal reflexes should be considered useful to disclose symptomatic TN, whereas younger age of onset, involvement of the first division, unresponsiveness to treatment and abnormal trigeminal evoked potentials are not useful in distinguishing symptomatic from classic TN. Carbamazepine (stronger evidence) or oxcarbazepine (better tolerability) should be offered as first-line treatment for pain control. For patients with TN refractory to medical therapy early surgical therapy may be considered. Gasserian ganglion percutaneous techniques, gamma knife and microvascular decompression may be considered. Microvascular decompression may be considered over other surgical techniques to provide the longest duration of pain freedom. The role of surgery versus pharmacotherapy in the management of TN in patients with multiple sclerosis remains uncertain.

Current management of pain associated with multiple sclerosis

While pain is a common problem in patients with multiple sclerosis (MS), it is not frequently mentioned by patients and a more direct approach is required in order to obtain information about pain from patients. Many patients with MS experience more than one pain syndrome; combinations of dysaesthesia, headaches and/or back or muscle and joint pain are frequent. For each pain syndrome a clear diagnosis and therapeutic concept needs to be established. Pain in MS can be classified into four diagnostically and therapeutically relevant categories: (i) neuropathic pain due to MS (pain directly related to MS); (ii) pain indirectly related to MS; (iii) MS treatment-related pain; and (iv) pain unrelated to MS. Painful paroxysmal symptoms such as trigeminal neuralgia (TN), or painful tonic spasms are treated with antiepileptics as first choice, e.g. carbamazepine, oxcarbazepine, lamotrigine, gabapentin, pregabalin, etc. Painful 'burning' dysaesthesias, the most frequent chronic pain syndrome, are treated with TCAs such as amitriptyline, or antiepileptics such as gabapentin, pregabalin, lamotrigine, etc. Combinations of drugs with different modes of action can be particularly useful for reducing adverse effects. While escalation therapy may require opioids, there are encouraging results from studies regarding cannabinoids, but their future role in the treatment of MS-related pain has still to be determined. Pain related to spasticity often improves with adequate physiotherapy. Drug treatment includes antispastic agents such as baclofen or tizanidine and in patients with phasic spasticity, gabapentin or levetiracetam are administered. In patients with severe spasticity, botulinum toxin injections or intrathecal baclofen merit consideration. While physiotherapy may ameliorate malposition-induced joint and muscle pain, additional drug treatment with paracetamol (acetaminophen) or NSAIDs may be useful. Moreover, painful pressure lesions should be avoided by using optimally adjusted aids. Treatment-related pain associated with MS can occur with subcutaneous injections of interferon-beta or glatiramer acetate, and may be reduced by optimizing the injection technique and by local cooling. Systemic (particularly 'flu-like') adverse effects of interferons, e.g. myalgias, can be reduced by administering paracetamol, ibuprofen or naproxen. A potential increase in the frequency of pre-existing headaches after starting treatment with interferons may require optimization of headache attack therapy or even prophylactic treatment. Pain unrelated to MS, such as back pain or headache, is common in patients with MS and may deteriorate as a result of the disease. In summary, a careful analysis of each pain syndrome will allow the design of the appropriate treatment plan using various medical and nonmedical options (multimodal therapy), and will thus help to improve the quality of life (QOL) of the patients.

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.

The cognitive effects of oxcarbazepine versus carbamazepine or valproate in newly diagnosed children with partial seizures

OBJECTIVE

To investigate the effect of oxcarbazepine against standard antiepileptic drug therapy (carbamazepine and valproate) on cognitive function in children and adolescents (aged 6 to <17 years) with newly diagnosed partial seizures.

METHODS

A multicentre, open-label, randomised, active-control, three-arm, parallel-group, 6-month study. The primary cognitive variable, the Computerized Visual Searching Task (CVST), assessed mental information processing speed and attention. Secondary variables included additional tests assessing psychomotor speed, alertness, memory and learning, and non-verbal intelligence.

RESULTS

Of 112 patients randomised, 99 completed the study. The dropout rate was 11.6%; 13 patients discontinued due to adverse events (n=5) or unsatisfactory therapeutic effect (n=8). Mean CVST time decreased in all groups, indicating an improvement of mental processing speed and no cognitive impairment in any treatment group. No statistically significant difference was observed between oxcarbazepine and combined carbamazepine/valproate. Analysis of secondary variables did not show statistically significant differences between oxcarbazepine, carbamazepine and valproate. Analysis of intelligence test results showed that the number of correct answers increased at end point in all groups. The percentage of patients remaining seizure free throughout treatment was comparable across all groups (oxcarbazepine 58%; carbamazepine 46%; valproate 54%; carbamazepine/valproate 50%). The most common adverse events were fatigue and headache for oxcarbazepine, fatigue and rash for carbamazepine, and headache, increased appetite and alopecia for valproate.

CONCLUSION

Oxcarbazepine treatment over 6 months does not display any differential effects on cognitive function and intelligence in children and adolescents with newly diagnosed partial seizures relative to standard antiepileptic drug therapy. No impairment in cognitive function was observed in any treatment group over a 6-month period.

Safety and efficacy of anticonvulsants in elderly patients with psychiatric disorders: oxcarbazepine, topiramate and gabapentin

Few controlled studies are available to guide the clinician in treating potentially assaultive elderly individuals with psychiatric disorders. Safety concerns limit the use of benzodiazepines and antipsychotic medications in the elderly individual, making anticonvulsants an attractive alternative. This paper reviews three specific anticonvulsants for this purpose: gabapentin, oxcarbazepine and topiramate, describing safety and efficacy in elderly patients with severe agitation from psychosis or dementia. Gabapentin, renally excreted, with a half-life of 6.5-10.5 h, may cause ataxia. Oxcarbazapine, hepatically reduced, may cause hyponatremia, and topiramate may cause significant cognitive impairment. Nonetheless, these are important medications to consider in the treatment of agitation.

EFNS guidelines on pharmacological treatment of neuropathic pain

Neuropathic pain treatment remains unsatisfactory despite a substantial increase in the number of trials. This EFNS Task Force aimed at evaluating the existing evidence about the pharmacological treatment of neuropathic pain. Studies were identified using first the Cochrane Database then Medline. Trials were classified according to the aetiological condition. All class I and II controlled trials (according to EFNS classification of evidence) were assessed, but lower-class studies were considered in conditions that had no top level studies. Only treatments feasible in an outpatient setting were evaluated. Effects on pain symptoms/signs, quality of life and comorbidities were particularly searched for. Most of the randomized controlled trials included patients with postherpetic neuralgia (PHN) and painful polyneuropathies (PPN) mainly caused by diabetes. These trials provide level A evidence for the efficacy of tricyclic antidepressants, gabapentin, pregabalin and opioids, with a large number of class I trials, followed by topical lidocaine (in PHN) and the newer antidepressants venlafaxine and duloxetine (in PPN). A small number of controlled trials were performed in central pain, trigeminal neuralgia, other peripheral neuropathic pain states and multiple-aetiology neuropathic pains. The main peripheral pain conditions respond similarly well to tricyclic antidepressants, gabapentin, and pregabalin, but some conditions, such as HIV-associated polyneuropathy, are more refractory. There are too few studies on central pain, combination therapy, and head-to-head comparison. For future trials, we recommend to assess quality of life and pain symptoms or signs with standardized tools.

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 oxcarbazepine to treat a pediatric patient with resistant complex regional pain syndrome

We describe a 12-year-old patient with severe, protracted complex regional pain syndrome type I. His pain did not respond to gabapentin, amitriptyline, physical therapy, opioids, or nonsteroidal drugs. Sympathetic or regional block was not attempted because of persistent bacteremia and severe local sepsis. His pain responded dramatically to the addition of oxcarbazepine, with rapid improvement in his symptoms and functional status. We suggest that oxcarbazepine might be a useful adjunct in the treatment of gabapentin-resistant complex regional pain syndrome type I in children and should be considered.

PERSPECTIVE

Oxcarbazepine's antinociceptive effect is mediated via sodium channel inhibition in neuropathic models and by inhibition of substance P and prostaglandins in anti-inflammatory models. The efficacy of oxcarbazepine in this patient might be attributable to these mechanisms or possibly to synergism with either gabapentin or the anti-inflammatory effects produced by amitriptyline.

Oxcarbazepine: clinical experience with hospitalized psychiatric patients

BACKGROUND

Oxcarbazepine (10-keto-carbamazepine) appears to be better tolerated and simpler to use than carbamazepine. It has antimanic effects but, as its potential clinical usefulness and tolerability in broad samples of psychiatric patients remain to be tested, we reviewed both the pharmacology of oxcarbazepine and our early experience with this new agent among psychiatric inpatients.

METHODS

We reviewed medical records of all inpatients given oxcarbazepine in the first 15 months of its use at McLean Hospital. Data analyzed included dosing, presenting illnesses, other medications, clinical changes, and adverse effects.

RESULTS

Oxcarbazepine was given to 56 inpatients (1.3% of admissions; 31 women, 25 men) presenting with depression (n = 23), mania (n = 19), or psychosis (n = 14). The discharge daily dose for the 43 patients (76%) taking oxcarbazepine was 831 mg/day, 34% higher in men than women, and fell by 9 mg/year-of-age. Oxcarbazepine was the only putative mood-stabilizing agent given at discharge in 19 of 43 cases (44%). It was discontinued in 20% of patients for apparent inefficacy, and 4% for adverse effects. Changes in CGI and GAF scores were similarly high across illnesses, and unrelated to days of use of oxcarbazepine or its dose.

CONCLUSIONS

Oxcarbazepine was well tolerated and simpler to use clinically than its precursor carbamazepine. This agent should be studied in controlled trials to test its efficacy in specific types of major psychiatric disorders, and particularly for long-term maintenance treatment in bipolar disorder.

Frontiers in Neuropharmacotherapy Part I: Alzheimer’s Disease and Epilepsy

Cholinesterase inhibitors, and particularly donepezil, are the standard of care in the management of Alzheimer’s disease. Newer agents, such as rivastigmine, galantamine, and metrifonate, provide therapeutic alternatives but have advantages and disadvantages compared with donepezil. Clinical studies and continued research of the pathophysiology of Alzheimer’s disease help define the role of both the newer agents and the original cholinesterase inhibitor, tacrine. Therapies with other mechanisms of action, such as estrogen and nonsteroidal anti-inflammatory drugs (NSAIDs), are also being actively investigated for their effects on cognition. Since 1993, 8 new antiepileptic drugs have been approved by the FDA, including felbamate, gabapentin, lamotrigine, topiramate, tiagabine, and 3 recently introduced agents, oxcarbazepine, levetiracetam, and zonisamide. These second-generation agents are generally more tolerable and have fewer drug interactions than traditional antiepileptics, and some provide alternative mechanisms that may be beneficial in the management of refractory epileptic disorders. However, until clinical experience with the newer antiepileptics accumulates and well-designed comparative trials are conducted, a review of individual studies of the safety and efficacy of the newer agents helps provide the basis for treatment decisions. New information regarding traditional therapies, including new formulations and updated treatment guidelines, also assist clinicians in optimizing antiepileptic therapy.

Effects of oxcarbazepine on sodium concentration and water handling

Oxcarbazepine, a keto-analogue of carbamazepine, was recently approved in the United States for the treatment of seizures of partial onset. Some patients treated with oxcarbazepine showed the development of hyponatremia, which in most instances was asymptomatic. Understanding the mechanisms by which oxcarbazepine can lead to a reduction of serum sodium levels could have therapeutic implications for the few patients in whom symptomatic hyponatremia develops. In this study, we evaluated sodium and water handling in patients with epilepsy and in healthy subjects titrated over 3 weeks to a maximum daily oxcarbazepine dose of 2,400mg. All subjects were evaluated in a hospital setting after an overnight fast and after an acute water-load test performed before oxcarbazepine exposure and after maintenance on the medication for 3 weeks. Before oxcarbazepine exposure, the percentage of water load excreted was normal as both groups excreted more than 80% of the administered water load. After the intake of oxcarbazepine, the water load resulted in a reduction of the serum sodium and free water clearance without a concomitant increase in the arginine vasopressin serum levels. Most subjects in both groups failed to excrete 80% or more of the water load, suggesting that the effect of oxcarbazepine is physiological. We found that, after the water load, serum sodium and free water clearance were diminished in both groups without a concomitant increase in the arginine vasopressin serum levels. These findings indicate that oxcarbazepine-induced hyponatremia is not attributable to the syndrome of inappropriate secretion of antidiuretic hormone. Possible mechanisms include a direct effect of oxcarbazepine on the renal collecting tubules or an enhancement of their responsiveness to circulating antidiuretic hormone.

Appropriate use of medications for seizures. Guiding principles on the path of efficacy

Selection of medication for treatment of seizures requires careful consideration and a multifactorial, individualized evaluation. First and foremost, the choice of a particular AED should be based on its efficacy against the seizure type or types or epilepsy syndrome being treated. Other factors, such as concomitant medical conditions, may also play a role in the type or dosage of medication prescribed. (For example, dosages of topiramate and levetiracetam should be adjusted in patients with renal impairment, and dosages of tiagabine should be adjusted in patients with liver dysfunction.) Other guidelines, discussed in detail in this article, can be applied irrespective of the particular drug chosen. Because the presence of epilepsy can have a significant bearing on quality of life, the decision to discontinue treatment should be made in congruence with the patient's needs, wishes, and commitments.

Oxcarbazepine in the treatment of epilepsy

Oxcarbazepine is a new antiepileptic drug (AED) that has been registered in more than 50 countries worldwide since 1990 and recently received approval in the United States and the European Union. Oxcarbazepine is a keto analog of carbamazepine and has a more favorable pharmacokinetic profile. It is rapidly absorbed after oral administration and undergoes rapid and almost complete reductive metabolism to form the pharmacologically active 10-monohydroxy derivative. Oxcarbazepine exhibits linear pharmacokinetics, no autoinduction, and minimal interaction with other AEDs. Ten controlled trials demonstrated that oxcarbazepine is safe and efficacious in the treatment of partial seizures across a wide range of ages (children to adults), situations (recent onset to treatment-resistant epilepsy), and uses (monotherapy and adjunctive therapy). The most common treatment-emergent adverse events are related to the central nervous system. Treatment-emergent hyponatremia (defined as serum sodium level < 125 mEq/L) occurred in 3% of patients treated with oxcarbazepine in clinical trials. According to the efficacy and safety profile established in the controlled trials, oxcarbazepine represents an important new treatment option indicated for monotherapy and adjunctive therapy in adults with partial seizures and as adjunctive therapy in children aged 4 years or older with partial seizures. Although structurally similar to carbamazepine, significant differences exist in the pharmacokinetics, drug interaction potential, adverse-effect profile, and dosage and titration between these two agents, and they should be considered distinct therapeutic agents.

Oxcarbazepine, an antiepileptic agent

BACKGROUND

Epilepsy is a common neurologic condition. Many of the currently approved pharmacologic agents for its treatment are associated with numerous adverse drug reactions and drug interactions.

OBJECTIVE

This review describes the pharmacology and therapeutic use of oxcarbazepine, an analogue of the well-known antiepileptic agent carbamazepine.

METHODS

Articles for review were identified through a search of MEDLINE, International Pharmaceutical Abstracts, and EMBASE for the years 1980 through 2000. The terms used individually and in combination were oxcarbazepine, carbamazepine, epilepsy, and seizures.

RESULTS

Oxcarbazepine and its primary metabolite have been effective in animal models of epilepsy that generally predict efficacy in generalized tonic-clonic seizures and partial seizures in humans. The exact mechanism of action of oxcarbazepine is unknown, although as with carbamazepine, it is believed to involve blockade of voltage-gated sodium channels. The pharmacokinetic profile of oxcarbazepine is less complicated than that of carbamazepine, with less metabolism by the cytochrome P450 system, no production of an epoxide metabolite, and lower plasma protein binding. The clinical efficacy and tolerability of oxcarbazepine have been demonstrated in trials in adults, children, and the elderly. In a double-blind, randomized, crossover trial in adults, oxcarbazepine 300 mg was associated with a decrease in the mean frequency of tonic seizures (21.4 vs 30.5 seizures during steady-state periods) and tonic-clonic seizures (8.2 vs 10.4) compared with carbamazepine 200 mg (P = 0.05). A multinational, multicenter, double-blind, placebo-controlled, randomized, 28-week trial assessed the efficacy and tolerability of oxcarbazepine at doses of 600, 1200, and 2400 mg as adjunctive therapy in patients with uncontrolled partial seizures. All 3 oxcarbazepine groups demonstrated a reduction in seizure frequency per 28-day period compared with placebo (600 mg, 26% reduction; 1200 mg, 40% reduction; 2400 mg, 50% reduction; placebo, 7.6% reduction; all, P < 0.001). A trial in children assessed the efficacy and toxicity of oxcarbazepine (median dose, 31.4 mg/kg/d) as adjunctive therapy for partial seizures. Patients receiving oxcarbazepine experienced a 35% reduction in seizure frequency, compared with a 9% reduction in the placebo group (P < 0.001). The most common adverse effects associated with oxcarbazepine are related to the central nervous system (eg, dizziness, headache, diplopia, and ataxia) and the gastrointestinal system (eg, nausea and vomiting). Compared with carbamazepine, there is an increased risk of hyponatremia with oxcarbazepine. The frequency and severity of drug interactions are less with oxcarbazepine than with carbamazepine or other antiepileptic agents.

CONCLUSIONS

Oxcarbazepine may be considered an appropriate alternative to carbamazepine for the treatment of partial seizures in patients who are unable to tolerate carbamazepine. Its use in nonseizure disorders remains to be examined in large-scale clinical trials, and pharmacoeconomic comparisons of oxcarbazepine with other antiepileptic agents, particularly carbamazepine, are needed.