Felbamate in refractory partial epilepsy

Impact of Antiseizure Medications on Appetite and Weight in Children

There are numerous potential factors that may affect growth in children with epilepsy, and these must be evaluated in any child with appetite and weight concerns. Antiseizure medications (ASMs) have potential adverse effects, and many may affect appetite, thus impacting normal growth and weight gain. The aim of this review is to focus on the impact of both epilepsy and ASMs on appetite and weight in children. We systematically reviewed studies using Medline assessing the impact of ASMs on appetite and weight in children. Eligible studies included randomized controlled trials and open-label studies (open-label extension and interventional) that targeted or included the pediatric population (0-18 years of age). Each study was classified using the American Academy of Neurology (AAN) Classification of Evidence for Therapeutic Studies, and the level of evidence for impact on appetite and weight in children was graded. ASMs associated with decreased appetite and/or weight loss include fenfluramine, topiramate, zonisamide, felbamate, rufinamide, stiripentol, cannabidiol, brivaracetam and ethosuximide; ASMs with minimal impact on weight and appetite in children include oxcarbazepine, eslicarbazepine, lamotrigine, levetiracetam, lacosamide, carbamazepine, vigabatrin and clobazam. The ASM most robustly associated with increased appetite and/or weight gain is valproic acid; however, both pregabalin and perampanel may also lead to modest weight gain or increased appetite in children. Certain ASMs may impact both appetite and weight, which may lead to increased morbidity of the underlying disease and impaired adherence to the treatment regimen.

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.

Pharmacotherapy of focal epilepsy in children: a systematic review of approved agents

BACKGROUND

Partial-onset seizures contribute the bulk of seizure burden in childhood epilepsy. The therapeutic decision making involves consideration of factors specific to drug, patient and socioeconomic situation.

OBJECTIVES

This paper systematically reviews the available efficacy/effectiveness evidence for various anti-epileptic drugs (AED) as monotherapy and adjunctive therapy for partial-onset seizures in children.

DATA SOURCES

Relevant randomized clinical trials (RCTs) were identified by a structured PubMed search, supplemented by an additional hand search of reference lists and authors' files.

STUDY APPRAISAL AND SYNTHESIS METHODS

Eligible studies were reviewed and data extracted into tables. Included RCTs were classified based on accepted published criteria.

OUTCOMES

Only efficacy and effectiveness outcome measures were evaluated since there is little scientifically rigorous comprehensive AED adverse effects data.

RESULTS

Oxcarbazepine is the only AED with Class I evidence for efficacy/effectiveness as initial monotherapy for partial-onset seizures in children. Carbamazepine, clobazam, lamotrigine, phenobarbital, phenytoin, topiramate, valproate, vigabatrin and zonisamide have, at best, Class III efficacy/effectiveness evidence for monotherapy of partial-onset seizures in children. For adjunctive therapy, gabapentin, lamotrigine, levetiracetam, oxcarbazepine and topiramate have Class I efficacy/effectiveness evidence for treatment of pediatric partial-onset seizures.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

This efficacy/effectiveness analysis must not be used in isolation when selecting therapy. AED selection for a specific child needs to integrate a drug's efficacy/effectiveness data with its safety and tolerability profile, pharmacokinetic properties, available formulations, and patient specific characteristics. It is critical that physicians and patients incorporate all these relevant variables when choosing AED therapy.

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

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

[Treatment of epilepsy with third-line antiepileptic drugs: felbamate, tiagabine, and sulthiame]

BACKGROUND

We retrospectively analysed the anticonvulsant efficacy of add-on treatment with felbamate (FBM), tiagabine (TGB), or sulthiame (STM) in patients with intractable focal and/or secondarily generalised seizures.

RESULTS

Forty-one patients (25 men, 16 women, mean age 29 years, mean duration of epilepsy 25 years) were treated with FBM. In nine patients (21.9%) seizure frequency was reduced by more than 50% (mean FBM dosage 3211 mg), and 13 patients (31.7%) reported side effects. Fifty-three patients (26 men, 27 women, mean age 38 years, mean duration of epilepsy 24 years) were treated with TGB. In seven patients (13.2%) seizure frequency was reduced by more than 50% (mean TGB dosage 32.9 mg), and 28 patients (52.8%) reported side effects. Twenty-eight patients (14 men, 14 women, mean age 32.6 years, mean duration of epilepsy 24.9 years) were treated with STM. In five patients (17.8%) seizure frequency was reduced by more than 50% (mean STM dosage 275 mg), and four patients (14.2%) reported side effects.

CONCLUSION

Third-line antiepileptic drugs, especially FBM and STM, are fairly well tolerated and contribute to seizure control.

Management of dental patients with seizure disorders

Dental practitioners from time to time must treat patients with epilepsy or similar seizure disorders. This article describes the various classification for epilepsy, explains how such disorders are evaluated and diagnosed, discusses management methods, and addresses related issues for special populations, such as pregnant women and elderly. In addition, the article offers information about what special steps dentists should take in treating such epileptic patients and others vulnerable to seizures and in preparing offices and staff for the possibility that a patient will have a seizure in the office. In general, a patient with severe, poorly controlled epilepsy should be treated in a hospital. Otherwise, a well-controlled patient should easily be treated in the office.

Mechanisms of idiosyncratic drug reactions: the case of felbamate

Idiosyncratic drug reactions (IDR) are a specific type of drug toxicity characterized by their delayed onset, low incidence and reactive metabolite formation with little, if any, correlation between pharmacokinetics or pharmacodynamics and the toxicological outcome. As the name implies, IDR are unpredictable and often result in the post marketing failure of otherwise useful therapies. Examples of drugs, which have failed as a result of IDR in recent years, include trovafloxacin, zileuton, troglitazone, tolcapone and felbamate. To date there exists no pre-clinical model to predict these adverse drug reactions and a mechanistic understanding of these toxicities remains limited. In an attempt to better understand this class of drug toxicities and gain mechanistic insight, we have studied the IDR associated with a model compound, felbamate. Our studies with felbamate are consistent with the theory that compounds which cause IDR undergo bioactivation to a highly reactive electrophilic metabolite that is capable of forming covalent protein adducts in vivo. In additon, our data suggest that under normal physiological conditions glutathione plays a protective role in preventing IDR during felbamate therapy, further emphasizing a correlation between reactive metabolite formation and a toxic outcome. Clinical studies with felbamate have been able to demonstrate an association between reactive metabolite formation and a clinically relevant toxicity; however, additional research is required to more fully understand the link between reactive metabolite formation and the events which elicit toxicity. Going forward, it seems reasonable that screening for reactive metabolite formation in early drug discovery may be an important tool in eliminating the post-marketing failure of otherwise useful therapies.

The long-term use of felbamate in children with severe refractory epilepsy

The aim of the study was to assess the efficacy and safety of felbamate (FBM) as add-on therapy in pediatric patients with severe uncontrolled seizures during a 3-year follow-up. Thirty-six patients were enrolled between February 1994 and February 1997. Patients suffered from partial epilepsy (n=13), Lennox-Gastaut syndrome (LGS) (n=9), infantile spasms (IS) n=8 or other forms of generalized epilepsy (n=6). FBM was titrated weekly from 15 up to 45 mg/kg. By February 1995, all patients had hematological and biochemical monitoring prior to FBM therapy and every 15 days during the study. The results achieved at different treatment durations were analyzed. Overall efficacy measured as > or =50% reduction in seizure frequency varied during follow-up: 69% at 3 months, progressively decreasing to 66% at 6 months, to 47% at 1 year and 41% of the initial cohort at the end of the study. Most frequent side effects were anorexia, weight loss, urinary retention, somnolence, nervousness and insomnia. FBM controlled a broad spectrum of otherwise refractory seizures. Best results were obtained against simple partial seizures with or without secondary generalization, tonic and atonic seizures. A substantial improvement in seizure control was maintained in one-third of the patients for at least 3 years.

Pharmacologic management of epilepsy in the elderly

OBJECTIVE

To review the epidemiology and pharmacologic management of epilepsy in elderly patients.

DATA SOURCES

Controlled trials, case studies, and review articles identified via MEDLINE using the search terms epilepsy, seizures, elderly, phenobarbital, primidone, phenytoin, carbamazepine, valproic acid, felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, and zonisamide. Recently published standard textbooks on epilepsy were also consulted.

DATA SYNTHESIS

Epilepsy is a common neurologic disorder in the elderly. Cerebrovascular and neurodegenerative diseases are the most common causes of new-onset seizures in these patients. Alterations in protein binding, distribution, elimination, and increased sensitivity to the pharmacodynamic effects of antiepileptic drugs (AEDs) are relatively frequent, and these factors should be assessed at the initiation, and during adjustment, of treatment. Drug-drug interactions are also an important issue in elderly patients, because multiple drug use is common and AEDs are susceptible to many interactions. In addition to understanding age-related changes in the pharmacokinetics and pharmacodynamics of AEDs, clinicians should know the common seizure types in the elderly and the spectrum of AED activity for these seizure types. AEDs with activity against both partial-onset and generalized seizures include felbamate, lamotrigine, levetiracetam, topiramate, valproic acid, and zonisamide. Other AEDs discussed in this review (carbamazepine, gabapentin, phenobarbital, phenytoin, primidone, and tiagabine) are most useful for partial-onset seizures.

CONCLUSION

The provision of safe and effective drug therapy to elderly patients requires an understanding of the unique age-related changes' in the pharmacokinetics and pharmacodynamics of AEDs as well as an appreciation of common seizure types and the drugs that are effective for the specific types seen in the elderly.

New antiepileptic drugs and non-pharmacological treatments

Many new drugs and therapies can now be offered to patients with epilepsy. The problem is that we do not know just how much better these new and more expensive therapies are compared with the old ones, nor do we know the full range of side-effects. This review focuses on the major clinical studies that have been published in the past year with emphasis on information as to tolerability and efficacy, especially when there is some information comparing different drugs or therapies. The topics include vigabatrin, lamotrigine, gabapentin, felbamate, topiramate, tiagabine, oxcarbazepine, levetiracetam, vagus nerve stimulation and the ketogenic diet. It is encouraging that some of the newly published double-blinded placebo-controlled studies now include children and the elderly, patient groups that have previously been neglected.