Overview of the safety of newer antiepileptic drugs

Pharmacologic Treatment Tools: Systemic Medications and Toxins, Opportunities, and Pitfalls

Treatment of pathologic muscle overactivity associated with upper motor neuron syndrome can be multifaceted. One of the initial decisions to be made when formulating an overarching treatment plan is selecting a combination of strategies that is most applicable. Strategies may include physical interventions, such as stretching or splinting modalities, or surgery, whereas pharmacotherapeutic strategies encompass oral/systemic medications as well as agents, such as toxins and alcohols, used for focal chemodenervation. This article reviews the oral/systemic therapies as well as toxins that are used focally. Although medication can also be administered via intrathecal pumps, this treatment approach is discussed elsewhere.

A Novel Strategy Combining Array-CGH, Whole-exome Sequencing and In Utero Electroporation in Rodents to Identify Causative Genes for Brain Malformations

Birth defects that involve the cerebral cortex - also known as malformations of cortical development (MCD) - are important causes of intellectual disability and account for 20-40% of drug-resistant epilepsy in childhood. High-resolution brain imaging has facilitated in vivo identification of a large group of MCD phenotypes. Despite the advances in brain imaging, genomic analysis and generation of animal models, a straightforward workflow to systematically prioritize candidate genes and to test functional effects of putative mutations is missing. To overcome this problem, an experimental strategy enabling the identification of novel causative genes for MCD was developed and validated. This strategy is based on identifying candidate genomic regions or genes via array-CGH or whole-exome sequencing and characterizing the effects of their inactivation or of overexpression of specific mutations in developing rodent brains via in utero electroporation. This approach led to the identification of the C6orf70 gene, encoding for a putative vesicular protein, to the pathogenesis of periventricular nodular heterotopia, a MCD caused by defective neuronal migration.

Determination of Lamotrigine in Pharmaceutical Preparations by Adsorptive Stripping Voltammetry Using Screen Printed Electrodes

This paper describes a procedure that has been optimized for the determination of lamotrigine by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV) using carbon screen-printed electrodes (CSPE) and mercury coated carbon screen-printed electrodes. Selection of the experimental parameters was made using experimental design methodology. The detection limit found was 5.0 x 10^-6 M and 2.0 x 10^-6 M for the non modified and Hg modified CSPE, respectively. In terms of reproducibility, the precision of the above mentioned methods was calculated in %RSD values at 9.83% for CSPE and 2.73% for Hg-CSPE. The Hg-coated CSPEs developed in this work were successfully applied in the determination of lamotrigine in pharmaceutical preparations.

The ketogenic diet in children with epilepsy

Children with epilepsy, especially those facing intractable seizures, experience a great impact on the quality of their lives. Effective treatment is essential, and although new anti-epileptic drugs have shown an improved profile of action, still a substantial number of children look for more efficacious ways of treatment that are far away from potential toxicity and ineffectiveness. The ketogenic diet is a dietary therapy for epileptic children based on manipulation of metabolism principles and brain energetics. This regimen aims to produce a controlled ketonaemia through excessive dietary fat intake, little carbohydrates and adequate (for growth) protein. The present paper is a review of previous and current papers regarding the proposed mechanisms of the ketogenic diet’s action, and the efficacy of the regimen on epileptic children. Unfortunately, a few small studies in sample size and duration tried to evaluate the potential risks of this regimen and their results were rather inconclusive. Further research needs to be done in order for the exact mechanism of the ketogenic diet to be clarified which will help to improve the diet’s application, especially for vulnerable epileptic children as far as their growth is concerned.

Optimization of solid-phase microextraction procedures for the determination of tricyclic antidepressants and anticonvulsants in plasma samples by liquid chromatography

Simple, sensitive, and reproducible off-line solid-phase microextraction and liquid chromatography (SPME/LC) methods are described for the determination of seven anticonvulsants and tricyclic antidepressants in human plasma. Factorial design and simplex methodology were applied in the optimization of the SPME procedure for tricyclic antidepressants analyses. Important factors in the SPME efficiency are discussed, such as the fiber coatings (both lab-made and commercial), extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The development of the lab-made fiber coatings, namely, octadecylsilane, aminosilane, and polyurethane, are further described and applied to anticonvulsants analyses. The investigated plasmatic range for the evaluated anticonvulsants, using CW-TPR fiber, were the following: phenylethylmalonamide (3.00-40.0 microg mL(-1)), phenobarbital (5.00-40.0 microg mL(-1)), primidone (3.00-40.0 microg mL(-1)), carbamazepine and carbamazepine-epoxide (2.00-24.0 microg mL(-1)), phenytoin (2.00-40.0 microg mL(-1)), and lamotrigine (0.50-12.0 microg mL(-1)). The antidepressants' linear plasmatic concentration ranged from 75.0 to 500 ng mL(-1) for imipramine, amitriptyline, and desipramine, and from 50.0 to 500 ng mL(-1) for nortriptyline, being in all cases, the limit of quantification represented by the lowest value. The precision (interassays) for all investigated drugs in plasma sample spiked with different concentrations of each analyte and submitted to the described procedures were lower than 15%. The off-line SPME/LC methodologies developed allow anticonvulsants and antidepressants analyses from therapeutic to toxic levels for therapeutic drug monitoring.

Augmentation strategies in clozapine-resistant schizophrenia

The introduction of antipsychotics in the 1950s revolutionised the treatment of schizophrenia, but it soon became apparent that a substantial number of patients demonstrated a suboptimal response to these antipsychotics. Clozapine proved to be beneficial in patients whose symptoms were treatment resistant, but it too had limitations, with as many as 40-70% of those treated with clozapine demonstrating inadequate response to this drug as well. The availability of other 'atypical' antipsychotics offers options, but clozapine appears to remain the most effective option in treatment-resistant schizophrenia. This, of course, raises the question of what to do when clozapine is only partially effective. To address the issue of treatment in patients who have demonstrated a suboptimal response to clozapine, efforts have focused on a variety of augmentation strategies, including numerous medications and electroconvulsive therapy. The current body of evidence consists largely of data from smaller open trials and case series/reports, although data from a limited number of controlled studies are now available. Not surprisingly, the evidence drawn from the former is more supportive of augmentation strategies, although the controlled trials are not without positive findings. The available information is certainly not so overwhelming as to endorse any single augmentation approach. Indeed, it argues for more controlled data and cautions us regarding the cost-benefit ratio in adopting this strategy. Over and above the added adverse effects of another treatment, there is evidence to indicate that actual clinical worsening can occur. Without compelling evidence, clinicians must resort to guiding principles. The potential benefits of augmentation cannot be ruled out, but it should be approached with caution and in a systematic fashion. Factors compromising clozapine response should first be ruled out, and any augmentation trials should be guided by existing evidence and a treatment plan that incorporates a clear understanding of target symptoms. A means of evaluating outcome effectively needs to be in place, and the trial should be circumscribed to prevent needless polypharmacy. A priori, an endpoint needs to be established and the trial discontinued unless results firmly support added benefits.

The safety and effectiveness of newer antiepileptics: a comparative postmarketing cohort study

Clinical trials for the newer antiepileptic drugs (AEDs) have provided inconclusive information to evaluate comparative risk benefit. The authors use data from postmarketing observational cohort studies to compare the failure of treatment with lamotrigine, vigabatrin, and gabapentin in patients with refractory epilepsy. The Drug Safety Research Unit has conducted prescription event monitoring (PEM) studies for lamotrigine, vigabatrin, and gabapentin to monitor their safety when used in primary care. The primary outcome of this study was time to treatment failure in patients who had been prescribed the drug after the start of the PEM study. Patients on gabapentin had reduced time to treatment failure compared to those on the other 2 drugs. The age- and sex-adjusted hazard ratio of failure was 1.53 (95% confidence interval [CI] = 1.38-1.70) for gabapentin compared to lamotrigine and 1.19 (95% CI = 1.10-1.30) for vigabatrin compared to lamotrigine. The observed differences between the 3 study drugs might be confounded by a higher proportion of patients treated with gabapentin having refractory epilepsy, a shorter duration of the gabapentin PEM study, and a lower relative dose of gabapentin (approved at the time of the PEM study). The current study provides information about the routine usage of newer AEDs, which complements evidence from clinical trials regarding the efficacy and safety of these AEDs. Although this study showed differences on times to treatment failure between lamotrigine, vigabatrin, and gabapentin, the results are only useful when considered together with results from other studies seeking to answer the same questions.

Strategies for optimizing antiepileptic drug therapy in elderly people

The elderly take more antiepileptic drugs (AEDs) than all other adults. This extensive use directly correlates with an increased prevalence of epilepsy in a growing population of older people, as well as other neuropsychiatric conditions such as neuropathic pain and behavioral disorders associated with dementia and for which AEDs are administered. The agents account for nearly 10% of all adverse drug reactions in the elderly and are the fourth leading cause of adverse drug reactions in nursing home residents. Numerous factors associated with advanced age contribute to the high frequency of untoward drug effects in this population; however, strategies are available to ensure optimal outcomes.

Vagus nerve stimulation and the ketogenic diet

Antiepileptic drugs are the primary form of treatment for patients with epilepsy. In the United States, hundreds of thousands of people do not achieve seizure control, or have significant side effects, or both. Only a minority of patients with intractable epilepsy are candidates for traditional epilepsy surgery. Vagus nerve stimulation is now the second most common treatment for epilepsy in the United States. Additionally, the ketogenic diet has established itself as a valid treatment. This article discusses the history, mechanism of action, patient selection, efficacy, initiation, complications, and advantages of vagus nerve stimulation and the ketogenic diet.

Gabapentin-induced hypersensitivity syndrome

Hypersensitivity syndrome is a rare but potentially fatal reaction to some pharmacologic agents, including some antiepileptic drugs. Typically, the syndrome presents with fever, rash, tender lymphadenopathy, hepatitis, and eosinophilia. We report a novel case of clinical hypersensitivity syndrome secondary to gabapentin. A patient developed altered mental status, fever, diffuse macular rash, and an enlarged spleen. This constellation of symptoms and signs began 9 days after gabapentin therapy was begun. Quick resolution was noted after gabapentin was discontinued. To our knowledge, there are no reports of hypersensitivity syndrome to gabapentin.

Anticonvulsant properties of N-salicyloyltryptamine in mice

A new tryptamine analogue, N-salicyloyltryptamine (STP), a potential central nervous system (CNS) depressant, was tested in the pentylenetetrazol (PTZ) and maximal electroshock (MES) models of epilepsy in mice. When administered concurrently, STP (100 mg/kg ip) significantly reduced the number of animals that exhibited PTZ-induced seizures and eliminated the extensor reflex of maximal electric-induced seizures test in 50% of the experimental animals. In addition, it showed protection in the PTZ test by diminishing the death rate.

New antiepileptic drugs and preparations

Epilepsy affects 1.2% to 4.4% of the general population. Given the clinical profile of the newer antiepileptic agents, it is likely their usage will increase in the coming years, thus increasing the emergency physician's exposure to these medications and their side effects. Several of these side effects can have high morbidity, such as the aplastic anemia and hepatotoxicity caused by felbamate, and the Stevens-Johnson syndrome associated with lamotrigine. Overdoses of these medications also could increase, as will our knowledge of recognizing and managing them. The clinical spectrum of the newer medications is the treatment of partial seizures. None of the newer medications can be orally loaded nor are they available in an i.v. preparation. Serum drug levels are not available in most institutions and are not routinely measured in the ED. The new preparations of phenytoin, diazepam, and valporic acid add increased efficiency in drug administration, providing a new method for prehospital treatment of seizures and a more tolerable means of administration in the ED.

Adverse effects of antiepileptic drugs

Because the efficacies of antiepileptic drugs (AEDs) are often equivalent, selection of an AED is often determined by adverse effects. Differences in methods for labeling adverse effects and in the adverse effect terms themselves, variations in the populations studied, and inconsistent classifications of adverse effects make it difficult to know how to use information on adverse effects to choose an AED. Effort is underway to develop more extensive and internationally acceptable descriptive terms for adverse effects. Comparison of adverse effects in patients taking AEDs with adverse events in control groups is helpful; however, data from controlled studies are often lacking for most AEDs. Because of these limitations, the clinician must adopt a preventative and early detection approach based on some general principles. This review outlines factors to consider for avoiding and detecting AED adverse effects. The occurrence of weight change with AEDs is reviewed extensively, serving to illustrate how the principle factors can be used to avoid and manage adverse effects and where there is need for better studies of the short- and long-term adverse effects of AEDs.

Potential interaction between ritonavir and carbamazepine

Ritonavir (RTV), a protease inhibitor, and carbamazepine (CBZ), an anticonvulsant, were administered concurrently to a patient who had human immunodeficiency virus infection and epilepsy. The combination resulted in elevated serum concentrations of CBZ, with accompanying vomiting, vertigo, and transient liver dysfunction. After discontinuing RTV and reducing the dosage of CBZ, the serum concentration of CBZ returned to the optimal range, symptoms subsided, and liver function returned to baseline. Carbamazepine is metabolized in the liver to a large extent by the cytochrome P450 (CYP) system, especially CYP3A4, 2C8, and 1A2, whereas RTV is metabolized primarily by CYP3A and is a potent inhibitor of this enzyme. Careful clinical monitoring may help prevent adverse drug interactions when these drugs are administered concurrently.

Relationship between EEG and positron emission tomography abnormalities in clinical epilepsy

Positron emission tomography (PET) is a relatively noninvasive neuroimaging method by means of which a large variety of human brain functions can be assessed. Localized neurochemical abnormalities detected by PET were found in patients with partial epilepsy and suggested the use of this modality for localizing epileptogenic regions of the brain. The clinical usefulness of PET is determined by its sensitivity and specificity for identifying epileptogenic areas as defined by ictal surface and intracranial EEG recordings. The findings obtained from comparative EEG and glucose PET data are reviewed with special emphasis on patients undergoing presurgical evaluation because of medically intractable temporal and extratemporal lobe epilepsy. The utility of glucose PET studies for identifying regions of seizure onset is presented, and the limited specificity of glucose metabolic abnormalities for the detection of various EEG patterns in clinical epilepsy is discussed. The authors review the available intracranial EEG and PET comparisons using [11C]flumazenil (FMZ) PET, a tracer for the assessment of tau-amino-butyric acid/benzodiazepine receptor function. They also summarize their experience with [11C]flumazenil PET in identifying cortical regions that show various ictal and interictal cortical EEG abnormalities in patients with extratemporal seizure origin. Finally, the authors demonstrate that further development of new PET tracers, such as alpha-[11C]methyl-L-tryptophan, is feasible and clinically useful and may increase the number of patients in whom PET studies can replace invasive EEG monitoring.

Depression in epilepsy: etiology, phenomenology, and treatment

A history of depression or depressive symptomatology has been reported in up to two-thirds of patients with medically intractable epilepsy, whereas community studies have demonstrated affective disorder only in a quarter of these patients. Depression has been reported peri- and interictally. However, differentiation may be difficult in patients with frequent seizures. Most authors have found no correlation between depression and epilepsy variables. However, complex partial seizures, especially of temporal lobe origin, appear to be etiologic factors, particularly in men with left-sided foci. Depression is also more common in patients treated with polytherapy especially with barbiturates, phenytoin, and vigabatrin. Depression has also been described de novo after temporal lobectomy. Psychosocial factors also play a part, but underlying risk factors (e.g., genetic, endocrine and metabolic) may explain the increased rates of depression in people with epilepsy compared to those with other neurologic and chronic medical conditions. The depression appears to be endogenous. Patients tend to exhibit fewer neurotic traits and more psychotic symptoms such as paranoia, delusions, and persecutory auditory hallucinations. Treatment approaches include psychotherapy, rationalization of antiepileptic drug medication, antidepressant treatment, and ECT. The tricyclic and related antidepressants appear to be epileptogenic, especially in people at high risk (personal or family history of seizures, abnormal pretreatment EEG, brain damage, alcohol or substance abuse/withdrawal and concurrent use of CNS-active medication). Seizures tend to occur early in treatment or after dose increments, especially if rapidly titrated. There is little evidence that the newer antidepressants, e.g., selective serotonin reuptake inhibitors, moclobemide, venlafaxine, or nefazodone are more epileptogenic than placebo.

New antiepileptic drugs: comparison of key clinical trials

PURPOSE

Data accrued from clinical trials of five new antiepileptic drugs (AEDs) are compared for efficacy in reducing seizures and self-reported adverse events as a basis of selection among new AEDs. Drawbacks to use of these data also are demonstrated.

METHODS

A review of double-blind, placebo-controlled clinical trials of a new AED or placebo added to a standard AED provided data on reduction of complex partial seizures (CPSs). Success is > or =50% fewer CPSs with a new AED or placebo; Overall Improvement is the success rate with drug minus the success rate with placebo. Adverse events were tabulated from product-labeling lists of COSTART items (incidence, > or =5%). The Summary Complaint score is the total number of reports of individual events for each AED.

RESULTS

Efficacy data demonstrate differences in Overall Improvement rates among five new AEDs and placebos (p = 0.001). However, rates of response to placebo also differed significantly among trials (p = 0.01). Adverse events predominantly affect central nervous system, psychiatric, and general body systems. However, patients in the placebo control groups did not consistently report adverse effects. Summary Complaint scores differ among the five new AEDs, but variability in use of COSTART terms nullifies comparisons.

CONCLUSIONS

Comparisons of data for five new AEDs provide information for selection among treatments when a second drug is needed to improve control of CPSs. However, significant differences among the control groups and other problems make comparisons between trials problematic. The final choice should be based on the need of the individual patient for superior seizure control versus minimal adverse effects.

Hypersensitivity reaction in a child due to lamotrigine

Lamotrigine is an anticonvulsant with a broad spectrum of activity that has been approved in the United States for use in adults with either partial or generalized seizures. This drug is being widely prescribed by pediatricians and neurologists because it is effective in children with idiopathic, resistant, generalized seizures and does not impair cognition. As with other anticonvulsants, a hypersensitivity syndrome has been described. Anticonvulsant hypersensitivity syndrome consists of the hallmark features of fever, rash, and lymphadenopathy. We report the first case of hypersensitivity syndrome in a child due to lamotrigine in which we believe the coadministration of valproic acid increased the duration of the reaction. Our patient had a high spiking fever, generalized morbilliform eruption, facial edema, lymphadenopathy, eosinophilia, atypical lymphocytosis, and an elevation in his liver function tests. The syndrome resolved with the discontinuation of the medication. Anticonvulsant hypersensitivity syndrome may occur with the administration of lamotrigine. Variable presentations may be seen, as hypersensitivity syndromes may be multisystem in nature. The prompt recognition of the signs and symptoms of this condition allows an accurate diagnosis so that the drug may be discontinued and other anticonvulsant treatment options instituted.

Imaging epileptogenic tubers in children with tuberous sclerosis complex using alpha-[11C]methyl-L-tryptophan positron emission tomography

Several reports have indicated that cortical resection is effective in alleviating intractable epilepsy in children with tuberous sclerosis complex (TSC). Because of the multitude of cortical lesions, however, identifying the epileptogenic tuber(s) is difficult and often requires invasive intracranial electroencephalographic (EEG) monitoring. As increased concentrations of serotonin and serotonin-immunoreactive processes have been reported in resected human epileptic cortex, we used alpha-[11C]methyl-L-tryptophan ([11C]AMT) positron emission tomography (PET) to test the hypothesis that serotonin synthesis is increased interictally in epileptogenic tubers in patients with TSC. Nine children with TSC and epilepsy, aged 1 to 9 years (mean, 4 years 1 month), were studied. All children underwent scalp video-EEG monitoring, PET scans of glucose metabolism and serotonin synthesis, and EEG monitoring during both PET studies. [11C]AMT scans were coregistered with magnetic resonance imaging and with glucose metabolism scans. Whereas glucose metabolism PET showed multifocal cortical hypometabolism corresponding to the locations of tubers in all 9 children, [11C]AMT uptake was increased in one tuber (n=3), two tubers (n=3), three tubers (n=1), and four tubers (n=1) in 8 of the 9 children. All other tubers showed decreased [11C]AMT uptake. Ictal EEG data available in 8 children showed seizure onset corresponding to foci of increased [11C]AMT uptake in 4 children (including 2 with intracranial EEG recordings). In 2 children, ictal EEG was nonlocalizing, and in 1 child there was discordance between the region of increased [11C]AMT uptake and the region of ictal onset on EEG. The only child whose [11C]AMT scan showed no regions of increased uptake had a left frontal seizure focus on EEG; however, at the time of his [11C]AMT PET scan, his seizures had come under control. [11C]AMT PET may be a powerful tool in differentiating between epileptogenic and nonepileptogenic tubers in patients with TSC.

Electrophysiological effects of felbamate

Felbamate is a broad spectrum antiepileptic drug recently introduced into clinical practice for controlling seizures in patients affected by Lennox-Gastaut epilepsy, complex partial seizures or otherwise intractable epilepsies. However, the cellular mechanisms by which the drug exerts its anticonvulsant actions are not fully understood. The aim of the present article is to outline the possible mechanisms of action of felbamate as suggested by findings obtained with electrophysiological approaches.

New drugs for epilepsy

Seizure freedom with no side-effects is the aim of treatment, and new antiepileptic drugs have not lived up to expectations; only a few patients with chronic epilepsy have been rendered seizure-free. These treatments have side-effects but their safety profile may be better than older alternatives, although chronic effects have not yet been established. This article reviews newly marketed antiepileptic drugs. It concentrates on shortcomings of current antiepileptic treatment and on the way drugs are developed. A new approach to treatment is long overdue. The development of rational antiepileptic treatments should be strongly encouraged. More clinically relevant paradigms need to be developed and incorporated into clinical trial programmes as these are presently biased in their designs towards regulatory issues.