Eficácia e segurança do Felbamato comparado a medicamentos disponíveis no SUS para o tratamento da epilepsia refratária em crianças e adultos: revisão rápida de evidências / Effectiveness and safety of Felbamate compared to drugs available in SUS for the treatment of refractory epilepsy in children and adults: rapid evidence review

Tecnologia: Felbamato. Indicação: Tratamento de epilepsia refratária. Pergunta: O Felbamato é mais eficaz e seguro comparado a anticonvulsivantes disponíveis no Sistema Único de Saúde (SUS) em pacientes com epilepsia refratária? Métodos: Revisão rápida de evidências (overview) de revisões sistemáticas, com levantamento bibliográfico realizado na base de dados PUBMED, utilizando estratégia estruturada de busca. A qualidade metodológica das revisões sistemáticas foi avaliada com AMSTAR-2 (Assessing the Methodological Quality of Systematic Reviews). Resultados: Foram selecionadas 2 revisões sistemáticas, que atendiam aos critérios de inclusão. Conclusão: O felbamato não demonstrou ser uma opção mais benéfica que os demais medicamentos disponíveis no SUS no tratamento de epilepsia refratária a medicamentos. Salienta-se que a maior parte das evidências eram de baixa certeza

Technology: Felbamate. Indication: Treatment of refractory epilepsy. Question: Is felbamate more effective and safer compared to anticonvulsants available in Brazilian Public Health System in patients with refractory epilepsy? Methods: A rapid review of evidence (overview) of systematic reviews, with bibliographic survey carried out in the PUBMED database, using a structured search strategy. The methodological quality of systematic reviews was assessed using AMSTAR-2 (Assessing the Methodological Quality of Systematic Reviews). Results: Two systematic reviews that met the inclusion criteria were selected. Conclusion: Felbamate did not prove to be a more beneficial option than the other drugs available in the Brazilian Public Health System in the treatment of drug-refractory epilepsy. It should be noted that most of the evidence was of low certainty

Felbamate for pediatric epilepsy-should we keep on using it as the last resort?

Introduction: Concerns regarding felbamate adverse effects restrict its widespread use in children with drug-resistant epilepsy. We aimed to examine the efficacy and safety of felbamate in those children and identify the ones who may benefit most from its use. Methods: We retrospectively reviewed the medical files of all patients who were treated with felbamate in a tertiary pediatric epilepsy clinic between 2009-2021. Drug efficacy was determined at the first 3 months of treatment and thereafter. Therapeutic response and adverse reactions were monitored throughout the course of treatment. Results: Our study included 75 children (age 8.9 ± 3.7 years), of whom 53 were treated with felbamate for seizures, 16 for electrical status epilepticus during sleep and 6 for both. The median follow-up time was 16 months (range 1-129 months). The most common cause for epilepsy was genetic (29%). The median number of previous anti-seizure medications was six [4-8]. A therapeutic response ≥50% was documented in 37 (51%) patients, and a complete response in 9 (12%). Nineteen patients (25%) sustained adverse reactions, including three cases of elevated liver enzymes and one case of neutropenia with normal bone marrow aspiration. In all cases, treatment could be continued. All children with intractable epilepsy following herpes encephalitis showed a response to felbamate. Conclusion: Felbamate is an efficacious and safe anti-seizure medication in the pediatric population.

Felbamate as an oral add-on therapy in six dogs with presumptive idiopathic epilepsy and generalized seizures resistant to drug therapy.

Background: Idiopathic or genetic epilepsy commonly affects dogs; affected dogs are often refractory to anti-seizure drug therapy. Felbamate is an anti-seizure drug with established pharmacokinetic and safety data for dogs, but little published evidence of efficacy for managing generalized seizures in this species. Aim: The purpose of this retrospective case series was to evaluate the clinical efficacy and tolerability of oral felbamate in six presumptive epileptic dogs experiencing generalized seizures. Methods: Medical records from six dogs with presumptive idiopathic/genetic epilepsy manifesting as generalized seizure activity, for which oral felbamate was used as an add-on treatment, were reviewed. The number of seizures recorded for the 3-month period immediately before instituting felbamate was recorded for each dog. Short-term (3 months) and long-term (6 months or greater) seizure frequency post-felbamate therapy was recorded for each dog and compared with baseline. Results: Overall, dogs experienced a reduction (82%) in seizures after adding felbamate in the short term, with 5/6 dogs (83%) classified as responders (50% or greater reduction in seizures) and 3/6 dogs (50%) attaining seizure-free status. Mean and median long-term follow-up times were 13 and 11 months, respectively (range: 6 to 23 months). Four of the 6 dogs (67%) remained drug responders at final follow-up, with an average seizure reduction of 98%, 2 of which remained seizure-free at 8 and 21 months. Two dogs (33%) experienced increased seizure activity during long-term follow-up (12 and 23 months) and were considered non-responders. The non-responder dogs had an average long-term seizure reduction of 33%. No dog experienced any obvious adverse effects associated with felbamate administration. However, one dog not included in the analysis because of insufficient (<3 month) post-felbamate follow-up, was weaned off felbamate because of suspected hepatotoxicity. Conclusion: Our small case series suggests that oral felbamate might show promise as an add-on drug for epileptic dogs experiencing generalized seizures resistant to drug therapy. These results warrant a more controlled, prospective investigation into felbamate as a therapeutic agent for canine epilepsy.

Assessment of metabolic activation of felbamate in chimeric mice with humanized liver in combination with in vitro metabolic assays.

Felbamate (FBM) is an antiepileptic drug that has minimal toxicity in preclinical toxicological species but has a serious idiosyncratic drug toxicity (IDT) in humans. The formation of reactive metabolites is common among most drugs associated with IDT, and 2-phenylpropenal (2-PP) is believed to be the cause of IDT by FBM. It is important to consider the species difference in susceptibility to IDT between experimental animals and humans. In the present study, we used an in vitro and in vivo model system to reveal species difference in IDT of FBM. Human cytochrome P450 (CYP) and carboxylesterase (CES) expressing microsomes were used to clarify the isozymes involved in the metabolism of FBM. The remaining amount of FBM was significantly reduced in incubation with microsomes expressing human CYP2C8, 2C9, 2E1, and CES1c isozymes. Chimeric mice with humanized liver are expected to predict IDT in humans. Therefore, metabolite profiles in chimeric mice with humanized liver were investigated after administration of FBM. Metabolites after glutathione (GSH) conjugation of 2-phenylpropenal (2-PP), which is the reactive metabolite responsible for FBM-induced IDT, were detected in chimeric mice plasma and liver homogenate. Mass spectrometry imaging (MSI) visualizes distribution of FBM and endogenous GSH, and GSH levels in human hepatocyte were decreased after administration of FBM. In this study, we identified CYP and CES isozymes involved in the metabolism of FBM and confirmed reactive metabolite formation and subsequent decrease in GSH using humanized animal model. These results would provide useful information for the susceptibility to IDT between experimental animals and humans.

Short-term and long-term efficacy and safety of antiseizure medications in Lennox Gastaut syndrome: A network meta-analysis.

PURPOSE: To assess the short-term and long-term comparative efficacy and safety of ASMs for Lennox-Gastaut syndrome (LGS). METHODS: Following a systematic literature search, randomized controlled trial (RCT) and open-label extension (OLE) studies on LGS comparing ASMs with placebo or other ASMs were included. ≥50% reduction in drop seizure frequency from baseline and occurrence of treatment-emergent adverse events (TEAEs) were the primary efficacy and safety outcomes. For short-term outcomes, a network meta-analysis (NMA) reporting odds ratio (OR) with 95% confidence intervals (CIs) and hierarchy of competing interventions [surface under the cumulative ranking curve(SUCRA)] was done. Long-term outcomes were reported as proportion with 95% CIs using the random-effects model. RESULTS: Fifteen studies including 1263 participants with LGS (aged 2-54years) receiving any of six ASMs [cannabidiol (CBD), clobazam (CLB), felbamate (FLB), lamotrigine (LTG), rufinamide (RFM), topiramate (TPM)] or placebo were included. High-dose CLB (1.0 mg/kg/day; CLB_H) [OR: 4.9; 95% CI: 2.3-10.8] was significantly associated with ≥50% reduction in drop seizure frequency as compared with placebo, and achieved the highest-ranking probability (0.89) based on SUCRA values (although there was an overlap between confidence intervals of effect sizes of CLB, RFM and CBD), while high-dose CBD (20 mg/kg/day; CBD_H) [OR: 3.8; 95% CI:1.6-9.0] had significantly higher odds for occurrence of any TEAEs and had the highest-ranking probability (0.85). Furthermore, the long-term treatment with CLB [78%; 95% CI: 70-85%] was associated with a significantly higher proportion of patients with reduction in drop-seizures, and long-term use of CBD [96%; 95% CI: 95-98%] was associated with a higher frequency of TEAEs. CONCLUSION: The study findings suggest that CLB_H, CBD and RFM are the most efficacious and safest in terms of both short and long-term outcomes with CLB_H probably leading the hierarchy. Future head-to-head trials comparing these ASMs are needed.

The ups and downs of alkyl-carbamates in epilepsy therapy: How does cenobamate differ?

Since 1955, several alkyl-carbamates have been developed for the treatment of anxiety and epilepsy, including meprobamate, flupirtine, felbamate, retigabine, carisbamate, and cenobamate. They have each enjoyed varying levels of success as antiseizure drugs; however, they have all been plagued by the emergence of serious and sometimes life-threatening adverse events. In this review, we compare and contrast their predominant molecular mechanisms of action, their antiseizure profile, and where possible, their clinical efficacy. The preclinical, clinical, and mechanistic profile of the prototypical γ-aminobutyric acidergic (GABAergic) modulator phenobarbital is included for comparison. Like phenobarbital, all of the clinically approved alkyl-carbamates share an ability to enhance inhibitory neurotransmission through modulation of the GABAA receptor, although the specific mechanism of interaction differs among the different drugs discussed. In addition, several alkyl-carbamates have been shown to interact with voltage-gated ion channels. Flupirtine and retigabine share an ability to activate K+ currents mediated by KCNQ (Kv7) K+ channels, and felbamate, carisbamate, and cenobamate have been shown to block Na+ channels. In contrast to other alkyl-carbamates, cenobamate seems to be unique in its ability to preferentially attenuate the persistent rather than transient Na+ current. Results from recent randomized controlled clinical trials with cenobamate suggest that this newest antiseizure alkyl-carbamate possesses a degree of efficacy not witnessed since felbamate was approved in 1993. Given that ceno-bamate's mechanistic profile is unique among the alkyl-carbamates, it is not clear whether this impressive efficacy reflects an as yet undescribed mechanism of action or whether it possesses a unique synergy between its actions at the GABAA receptor and on persistent Na+ currents. The high efficacy of cenobamate is, however, tempered by the risk of serious rash and low tolerability at higher doses, meaning that further safety studies and clinical experience are needed to determine the true clinical value of cenobamate.

Felbamate produces antidepressant-like actions in the chronic unpredictable mild stress and chronic social defeat stress models of depression.

Felbamate is an anticonvulsant used in the treatment of epilepsy. In this study, we investigated the antidepressant-like actions of felbamate in mice. The effects of felbamate were first assessed using the forced swimming test (FST) and tail suspension test (TST), and then investigated in the chronic unpredictable mild stress (CUMS) and chronic social defeat stress (CSDS) models of depression. The changes in the hippocampal brain-derived neurotrophic factor (BDNF) signaling cascade after chronic stress and felbamate treatment were also examined. It was found that felbamate exhibited antidepressant-like activities in the FST and TST without affecting the locomotor activity of mice. Felbamate was also effective in both the CUMS and CSDS models of depression. Moreover, felbamate administration fully restored the decreased hippocampal BDNF signaling pathway in both the CUMS-stressed and CSDS-stressed mice. Collectively, felbamate has antidepressant-like actions in mice involving the hippocampal BDNF system.

The effects of felbamate on appetitive and aversive instrumental learning in adult rats.

Antiepileptic medications are the frontline treatment for seizure conditions but are not without cognitive side effects. Previously, our laboratory reported learning deficits in phenytoin-, carbamazepine-, and valproate-treated rats. In the present experiment, the effects of felbamate (FBM) have been compared to water-treated controls (controls) using the same instrumental training tasks employed here. Rats treated with FBM displayed a deficit in acquiring a tone-signaled avoidance response, relative to controls, but this was true only if they had no prior appetitive experience. Terminal avoidance behavior was equivalent to healthy controls. In contrast, the FBM-treated rats showed enhanced acquisition of the avoidance response relative to controls when given the benefit of prior experience in the appetitive condition. Relative to animals treated with phenytoin, carbamazepine, or valproate, FBM-treated rats showed the lowest overall pattern of deficits using these instrumental learning tasks. While FBM treatment has been severely restricted because of rather low risks of serious medical side effects, we suggest that the risks are not substantially higher than those shown to exist for phenytoin, carbamazepine, or valproate. As psychologists, we further suggest that negative cognitive deficits associated with these various drugs, along with their quality-of-life costs, are of relevance in the design of treatment strategies for individuals with seizure disorders.

Effects of antiepileptic drugs on mitochondrial functions, morphology, kinetics, biogenesis, and survival.

OBJECTIVES: Antiepileptic drugs (AEDs) exhibit adverse and beneficial effects on mitochondria, which have a strong impact on the treatment of patients with a mitochondrial disorder (MID) with epilepsy (mitochondrial epilepsy). This review aims at summarizing and discussing recent findings concerning the effect of AEDs on mitochondrial functions and the clinical consequences with regard to therapy of mitochondrial epilepsy and of MIDs in general. METHODS: Literature review. RESULTS: AEDs may interfere with the respiratory chain, with non-respiratory chain enzymes, carrier proteins, or mitochondrial biogenesis, with carrier proteins, membrane-bound channels or receptors and the membrane potential, with anti-oxidative defense mechanisms, with morphology, dynamics and survival of mitochondria, and with the mtDNA. There are AEDs of which adverse effects outweigh beneficial effects, such as valproic acid, carbamazepine, phenytoin, or phenobarbital and there are AEDs in which beneficial effects dominate over mitochondrial toxic effects, such as lamotrigine, levetiracetam, gabapentin, or zonisamide. However, from most AEDs only little is known about their interference with mitochondria. CONCLUSIONS: Mitochondrial epilepsy might be initially treated with AEDs with low mitochondrial toxic potential. Only in case mitochondrial epilepsy is refractory to these AEDs, AEDs with higher mitochondrial toxic potential might be tried. In patients carrying POLG1 mutations AEDs with high mitochondrial toxic potential are contraindicated.

Evaluating the safety and efficacy of felbamate in the context of a black box warning: A single center experience.

INTRODUCTION: Felbamate was approved in 1993 to treat partial seizures with and without secondary generalization in adults and in Lennox-Gastaut Syndrome in children. Its use was later restricted when rare but fatal cases of aplastic anemia and hepatic failure were identified. METHODS: This single center analysis retrospectively evaluated the safety and efficacy of felbamate in a cohort of children, adolescents, and adults with epilepsy. RESULTS: A chart review identified 103 patients taking felbamate. The range of felbamate dose was 300-4500 mg (mean: 1800 ± 900 mg). The duration of therapy ranged from 1 month to 20 years (mean duration: 35 ± 45 months). Eighteen (17.5%) subjects experienced adverse events including insomnia, nausea, vomiting, decreased appetite, weight loss, gastric discomfort, diarrhea, mood and behavioral problems, high blood pressure, headache, and elevated liver enzymes. Out of these, 6 (5.9%) patients discontinued the therapy. No hepatic failure or agranulocytosis was observed. Fifty-nine (57.72%) patients achieved ≥ 50% reduction in seizure frequency, and 30 (29.12%) patients achieved seizure freedom. CONCLUSIONS: These findings suggest that felbamate is safe, well tolerated, and effective in treatment of various types of epilepsy syndromes.

Successful Treatment of Electrographic Status Epilepticus of Sleep With Felbamate in a Patient With SLC9A6 Mutation.

BACKGROUND: Mutations of SLC9A6 may cause an X-linked clinical syndrome first described by Christianson in 1999 in which affected males exhibited profound intellectual disability, autism, drug-resistant epilepsy, ophthalmoplegia, mild craniofacial dysmorphism, microcephaly, and ataxia. METHODS: We describe a child with an SLC9A6 mutation and an electroencephalographic pattern consistent with electrographic status epilepticus of sleep. RESULTS: Our patient's electrographic status epilepticus of sleep resolved after treatment with felbamate. Following treatment, he remained seizure-free but did not make significant or lasting gains in language. CONCLUSION: Our report extends the clinical epilepsy phenotype in children with SLC9A6 mutations to include electrographic status epilepticus of sleep. In addition, felbamate was an effective treatment for electrographic status epilepticus of sleep in our patient.

Isobolographic analysis of the mechanisms of action of anticonvulsants from a combination effect.

The nature of the pharmacodynamic interactions of drugs is influenced by the drugs׳ mechanisms of action. It has been hypothesized that drugs with different mechanisms are likely to interact synergistically, whereas those with similar mechanisms seem to produce additive interactions. In this review, we describe an extensive investigation of the published literature on drug combinations of anticonvulsants, the nature of the interaction of which has been evaluated by type I and II isobolographic analyses and the subthreshold method. The molecular targets of antiepileptic drugs (AEDs) include Na(+) and Ca(2+) channels, GABA type-A receptor, and glutamate receptors such as NMDA and AMPA/kainate receptors. The results of this review indicate that the nature of interactions evaluated by type I isobolographic analyses but not by the two other methods seems to be consistent with the above hypothesis. Type I isobolographic analyses may be used not only for evaluating drug combinations but also for predicting the targets of new drugs.

Efficacy and safety of felbamate in children with refractory epilepsy.

BACKGROUND: Despite the introduction of multiple new antiepileptic drugs in the past two decades, many patients with epilepsy continue to experience uncontrolled seizures or significant side effects. AIM: To present our experience with felbamate therapy in children with drug-resistant epilepsy. METHODS: We retrospectively reviewed the medical charts and video-EEG recordings of all patients receiving felbamate until May 2012. Efficacy was determined according to seizure frequency during the week prior to treatment initiation and the week after the maximal dosage of felbamate was reached. RESULTS: Fifty patients (34 boys) aged 4 months to 17 years (mean--5.5 years) were identified. Nearly third of the patients had Lennox-Gastaut syndrome. Mean epilepsy duration was 3.4 years (range--1 month to 13 years). The mean number of previous antiepileptic drugs was 7.5. The mean duration of follow-up was 1.1 years. Seizure frequency decreased by at least 50% in 29 (58%) patients. Side effects were reported in 22 (44%) patients, none of them included aplastic anemia or liver failure. In the responder group, the maximal dose of felbamate was lower and the patients were older compared to non-responders. CONCLUSIONS: Despite current recommendations, felbamate is initiated following multiple AEDs. Based on its efficacy and safety data, earlier initiation of felbamate is recommended in children with refractory epilepsy.

Electroclinical features and long-term outcome of cryptogenic epilepsy in children with Down syndrome.

OBJECTIVE: To describe the electroclinical features and the long-term outcomes of epilepsy in a large cohort of males and females with Down syndrome who developed epilepsy in childhood. STUDY DESIGN: Subjects with Down syndrome and cryptogenic epilepsy with onset in childhood were identified retrospectively from the databases of 16 Italian epilepsy centers over a 40-year period. For each subject, age at onset of seizures, seizure semiology and frequency, electroencephalography characteristics, treatment with antiepileptic drugs, and long-term clinical and electroencephalography outcomes were analyzed. RESULTS: A total of 104 subjects (64 males [61.5%], 40 females [38.5%]) were identified. Seizure onset occurred within 1 year of birth in 54 subjects (51.9%), between 1 and 12 years in 42 subjects (40.4%), and after 12 years in 8 subjects (7.7%). Males had a younger age of seizure onset than females. Of the 104 subjects, 51 (49.0%) had infantile spasms (IS), 35 (33.7%) had partial seizures (PS), and 18 (17.3%) had generalized seizures (GS). Febrile seizures were recorded in 5 (4.8%) subjects. Intractable seizures were observed in 23 (22.1%) subjects, including 5 (9.8%) with IS, 8 (44.4%) with PS, and 10 (31.3%) with GS. CONCLUSION: Cryptogenic epilepsy in Down syndrome may develop during the first year of life in the form of IS or, successively, as PS or GS. Electroclinical features of IS resemble those of idiopathic West syndrome, with a favorable response to treatment with adrenocorticotropic hormone seen. Patients experiencing PS and GS may be resistant to therapy with antiepileptic drugs.

Indirect comparison of clobazam and other therapies for Lennox-Gastaut syndrome.

OBJECTIVE: In the absence of head-to-head trials, it is not feasible to make direct comparisons of antiepileptic therapies for the treatment of Lennox-Gastaut syndrome (LGS). We conducted indirect comparisons of the relative efficacies of clobazam, felbamate, lamotrigine, topiramate, and rufinamide as adjunctive treatments for LGS. METHODS: Clinical studies of LGS patients were identified in a 2009 Cochrane review and by electronic database search. Five randomized controlled trials were included in this systematic review, which reports findings from indirect comparisons between clobazam and other approved adjunctive LGS therapies (felbamate, lamotrigine, topiramate, rufinamide) in the United States and Europe. As outcomes were not uniformly reported across studies, the primary efficacy endpoint from each trial was transformed into Cohen's d effect size, to facilitate indirect comparisons. Typical interpretations of Cohen's d results are as follows: d < 0.2, change not detectable; 0.2 ≤ d < 0.5, small change; 0.5 ≤ d < 0.8, moderate change; and 0.8 ≤ d, large change. RESULTS: High-dosage clobazam (1.0 mg/kg/day) was found to have the strongest treatment effect vs placebo (effect size 0.80), with moderate effects (effect sizes >0.50) for medium-dosage clobazam (0.5 mg/kg/day) and rufinamide. Felbamate, lamotrigine, and topiramate had low effect sizes. Indirect comparisons of numbers of total seizures and tonic-atonic seizures ('drop attacks') demonstrated superiority of both clobazam dosages over all comparators. CONCLUSIONS: High- and medium-dosage clobazam was estimated to be more efficacious than other LGS treatments. Our analysis relied on published data and could not draw on direct head-to-head data of clobazam with alternatives. Further comparative research is ongoing to assess the usefulness of clobazam for LGS.

Suivi thérapeutique pharmacologique du felbamate.

Felbamate is a derivative of meprobamate used in second-line partial epilepsy and in the Lennox-Gastaut syndrome. Felbamate is well absorbed and has linear kinetics: Cmax and AUC increasing linearly with dose. The metabolism takes place in the liver. Metabolites represent 40 to 60% of excretion and are eliminated via the urine. The half-life is between 15 and 23 hours. Clearance is dependent on renal function. There is a concentration - efficacy and concentration - toxicity relationship. These arguments are in favour of a TDM but the therapeutic range is not clearly established. Potentially fatal side effects can be caused by felbamate (aplastic anemia, acute liver failure), which limits its use because they are dose-independant.