Efficacy of felbamate monotherapy in patients undergoing presurgical evaluation of partial seizures

Iron-Catalyzed Reaction of Urea with Alcohols and Amines: A Safe Alternative for the Synthesis of Primary Carbamates

A general study of the iron-catalyzed reaction of urea with nucleophiles is here presented. The carbamoylation of alcohols allows for the synthesis of N-unsubstituted (primary) carbamates, including present drugs (Felbamate and Meprobamate), without the necessity to apply phosgene and related derivatives. Using amines as nucleophiles gave rise to the respective mono- and disubstituted ureas via selective transamidation reaction. These atom-economical transformations provide a direct and selective access to valuable compounds from cheap and readily available urea using a simple Lewis-acidic iron(II) catalyst.

Chemical analysis of the Chinese liquor Luzhoulaojiao by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Luzhoulaojiao liquor is a type of Chinese liquor that dates back hundreds of years, but whose precise chemical composition remains unknown. This paper describes the screening of the liquor and the identification of its compounds using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOF-MS). Samples were prepared by both liquid-liquid extraction and solid-phase microextraction, which facilitated the detection of thousands of compounds in the liquor, thus demonstrating the superior performance of the proposed method over those reported in previous studies. A total of 320 compounds were common to all 18 types of Luzhoulaojiao liquor studied here, and 13 abundant and potentially bioactive compounds were further quantified. The results indicated that the high-performance method presented here is well suited for the detection and identification of compounds in liquors. This study also contributes to enriching our knowledge of the contents of Chinese liquors.

Felbamate as an add-on therapy for refractory epilepsy

BACKGROUND

This review is an update of a previously published review in The Cochrane Database of Systematic Reviews (Issue 1, 2011) on 'Felbamate as an add-on therapy for refractory epilepsy'. Epilepsy is a chronic and disabling neurologic disorder, affecting approximately 1% of the population. Up to 30% of people with epilepsy have seizures that are resistant to currently available drugs. Felbamate is one of the second-generation antiepileptic drugs and its effects as an add-on therapy to standard drugs are assessed in this review.

OBJECTIVES

To evaluate the efficacy and tolerability of felbamate versus placebo when used as an add-on treatment for people with refractory partial-onset epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (24 July 2013), the Cochrane Central Register of Controlled Trials (CENTRAL 2013, Issue 6), and PubMed (24 July 2013). This search was run for the original review on 20 May 2010. There were no language and time restrictions. We reviewed the reference lists of retrieved studies to search for additional reports of relevant studies. We also contacted the manufacturers of felbamate and experts in the field for information about any unpublished or ongoing studies.

SELECTION CRITERIA

Randomized placebo-controlled add-on studies of people of any age with refractory partial-onset seizures. The studies could be double-blind, single-blind or unblinded and could be of parallel or crossover design.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion and extracted information. We resolved disagreements by discussion. If disagreements persisted, the third review author arbitrated. We assessed the following outcomes: 50% or greater reduction in seizure frequency; absolute or percentage reduction in seizure frequency; treatment withdrawal; adverse effects; quality of life.

MAIN RESULTS

Three randomised controlled trials with a total of 153 participants were included. The first was a parallel design, the second had a two-period crossover design, and the third had a three-period crossover design. One study was at unclear risk of bias for random sequence generation and allocation concealment. And in the same study, there was no description of how to blind outcome assessment, performance blinding was for participants, might not be for doctors. Two studies were at high risk of bias for incomplete outcome data. Due to significant methodological heterogeneity, clinical heterogeneity and differences in outcome measures, it was not possible to perform a meta-analysis of the results. None of the three studies reported 50% or greater reduction in seizure frequency. Only one study reported absolute and percentage reduction in seizure frequency compared to placebo, P values were 0.046 and 0.018, respectively. Adverse effects rates were higher during the felbamate period than the placebo period, particularly headache, nausea and dizziness.

AUTHORS' CONCLUSIONS

In view of the methodological deficiencies, limited number of individual studies and differences in outcome measure, we have found no reliable evidence to support the use of felbamate as an add-on therapy in patients with refractory partial-onset epilepsy. A large-scale, randomised controlled trial conducted over a longer period of time is required to inform clinical practice.Since the last version of this review no new studies have been found.

Felbamate as an add-on therapy for refractory epilepsy

BACKGROUND

Epilepsy is a chronic and disabling neurologic disorder, affecting approximately one per cent of the population. Up to 30% of people with epilepsy have seizures that are resistant to currently available drugs. Felbamate is one of the second generation antiepileptic drugs and its effects as an add-on therapy to standard drugs are assessed in this review.

OBJECTIVES

To evaluate the efficacy and tolerability of felbamate versus placebo when used as an add-on treatment for people with refractory partial-onset epilepsy.

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group Specialized Register (6 December 2010), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 6 December 2010), and PubMed (6 December 2010). There were no language restrictions. We reviewed the reference lists of retrieved studies to search for additional reports of relevant studies. We also contacted the manufacturers of felbamate and experts in the field for information about any unpublished or ongoing studies.

SELECTION CRITERIA

Randomized placebo-controlled add-on studies of people of any age with refractory partial-onset seizures. The studies could be double-blind, single-blind or unblinded and could be of parallel or crossover design.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion and extracted information. Disagreements were resolved by discussion. If disagreements persisted, the third review author arbitrated. The following outcomes were assessed: 50% or greater reduction in seizure frequency; absolute or percentage reduction in seizure frequency; treatment withdrawal; adverse effects; quality of life.

MAIN RESULTS

Three randomized controlled trials were included. The first was a parallel design, the second was a two-period crossover design, and the third was a three-period crossover design. Due to significant methodological heterogeneity, clinical heterogeneity and differences in outcome measures, it was not possible to perform a meta-analysis of the results. None of the three studies reported 50% or greater reduction in seizure frequency. Only one study reported absolute and percentage reduction in seizure frequency compared to placebo, P values were 0.046 and 0.018, respectively. Adverse effects rates were higher during the felbamate period than the placebo period, particularly headache, nausea and dizziness.

AUTHORS' CONCLUSIONS

In view of the methodological deficiencies, limited number of individual studies and differences in outcome measure, we have found no reliable evidence to support the use of felbamate as an add-on therapy in patients with refractory partial-onset epilepsy. A large scale, randomized controlled trial conducted over a greater period of time is required to inform clinical practice.

Psychotropic effects of antiepileptic drugs

Antiepileptic drugs are important psychotropic agents that are commonly used to treat psychiatric disorders. The behavioral effects of antiepileptic drugs may differ between epilepsy and psychiatric patient populations. Randomized, double-blind, controlled data on the psychotropic efficacy of antiepileptic drugs are limited mainly to bipolar disorder.

Efficacy of felbamate in the treatment of intractable pediatric epilepsy

The antiepileptic drug felbamate has demonstrated efficacy against a variety of seizure types in the pediatric population, particularly seizures associated with Lennox-Gastaut syndrome. Postmarketing experience, however, revealed serious idiosyncratic adverse effects not observed during clinical trials, including aplastic anemia and liver failure. As a result, many physicians have been hesitant to prescribe felbamate. This retrospective study evaluated the efficacy of felbamate in a pediatric population with intractable epilepsy. Of 38 patients, 22 had Lennox-Gastaut syndrome (58%); 6 had myoclonic-astatic epilepsy of Doose (16%); 5 had symptomatic generalized epilepsy, not otherwise specified (13%); and 5 had symptomatic localization-related epilepsy (13%). Most patients had multiple seizure types and had been tried on a variety of antiepileptic medications. With felbamate treatment, 6 patients (16%) became seizure free, including 4 of the 6 patients with myoclonic-astatic epilepsy of Doose; 24 patients (63%) had a greater than 50% reduction in seizure frequency. In this population felbamate appeared to be safe, with minimal adverse effects. The study is limited by the small number of patients and by its retrospective nature, but nonetheless adds to the evidence that felbamate is an important antiepileptic drug for medically refractory epilepsy in children and is well tolerated with few adverse effects.

Designing clinical trials to assess antiepileptic drugs as monotherapy : difficulties and solutions

Designing monotherapy trials in epilepsy is fraught with many hurdles, including diagnostic and classification difficulties, sparse information regarding the natural history of the disorder, and ethical objections to the use of placebo or a suboptimal comparator in a condition where the consequences of therapeutic failure can be serious. These issues are further complicated by regulatory differences between the US and the EU.In the US, the FDA considers that evidence of efficacy requires demonstration of superiority to a comparator. Because available antiepileptic drugs possess relatively high efficacy, in most settings it is unrealistic to expect that a new treatment will be superior to a standard treatment used at optimized dosages. To circumvent this problem, trial designs have been developed whereby patients in the control group are assigned to receive a suboptimal comparator and are required to exit from the trial if seizure deterioration occurs. This allows demonstration of a between-group difference in efficacy endpoints, such as time to exit or time to first seizure. Although these trials have come under increasing criticism because of ethical concerns, extensive information is now available on the outcome of patients with chronic epilepsy randomized to suboptimal treatment in similarly designed conversion to monotherapy trials. This has allowed the construction of a dataset of historical controls against which response to a fully active treatment can be compared. A number of studies using this novel approach are now in progress.In the EU, in addition to requiring data on conversion to monotherapy in refractory patients, the European Medicines Agency stipulates that a monotherapy indication in newly diagnosed epilepsy can only be granted if a candidate drug has shown at least a similar benefit/risk balance compared with an acknowledged standard at its optimal use during an assessment period of no less than 1 year. This has led to the implementation of noninferiority trials, one of which has been completed and which led to approval of the monotherapy indication for levetiracetam in the EU. Noninferiority trials provide valuable data in a setting that most closely resembles routine clinical practice, but their interpretation can be complicated by uncertainties on assay sensitivity.Major evidence gaps in the treatment of epilepsy still remain and it is hoped that these will be addressed in the near future. High quality monotherapy trials are particularly needed to assess the comparative efficacy of older and newer drugs in less common epilepsy syndromes, including most generalized epilepsies, and to investigate the different treatment options in populations homogeneous not only in terms of syndromic classification, but also in terms of underlying aetiology and associated phenotypes.

Advancements in the Treatment of Epilepsy

Diagnostic tools and treatment options for epilepsy have expanded in recent years. Imaging techniques once confined to research laboratories are now routinely used for clinical purposes. Medications that were unavailable a few years ago are now first-line agents. Patients with refractory seizures push for earlier surgical intervention, consider treatment with medical devices, and actively seek nonpharmacologic alternatives. We review some of these recent advances in the management of epilepsy.

Felbamate: Consensus of current clinical experience

An expert panel convened to evaluate data and review current clinical practices regarding the novel antiepileptic drug (AED) felbamate. Felbamate has demonstrated efficacy against a variety of refractory seizures types, including seizures associated with Lennox-Gastaut syndrome, but postmarketing experience revealed serious idiosyncratic adverse effects that were not observed during clinical trials. Although felbamate is not indicated as first-line antiepileptic therapy, its utility in treating seizures that are refractory to other AEDs is undisputed, as shown by the number of patients who continue to use it. New exposures to felbamate number approximately 3200-4200 patients annually, and it is estimated that over the past 10 years, approximately 35,000 new starts have occurred. Recommendations by the American Academy of Neurology and a review of felbamate literature were evaluated in conjunction with the clinical experience of the expert panel to determine current medical opinion and practice regarding felbamate. The past 10 years of clinical experience have demonstrated that when used in accordance with existing recommendations and close clinical monitoring, felbamate is an effective treatment for some patients with seizures refractory to other AEDs. This review of clinical data and discussion of the current understanding of the risk:benefit of felbamate therapy supports its use as an important therapeutic option for some patients with refractory epilepsy.

Using New Antiepileptic Drugs As Monotherapy

Since 1993, with the advent of felbamate, physicians have been blessed with the addition of eight new antiepileptic medications for the treatment of epilepsy. Increasing evidence is accumulating that these drugs are effective as monotherapy agents. The use of monotherapy minimizes side effects, and newer drugs have fewer interactions than many of the older antiepileptic medications with comparable efficacy. Using the newer antiepileptic agents in monotherapy, even as an initial therapy would appear to be an appropriate clinical decision.

Review of new antiepileptic drugs as initial therapy

The new onset of epilepsy usually leads to initiation of treatment with antiepileptic drugs (AEDs). Selection of the appropriate drug in this clinical situation is usually based on several factors, including efficacy for the suspected epilepsy type, tolerability, acute and long-term idiosyncratic side effects, pharmacokinetic interactions, possibility of rapid titration, formulation, and expense. Over the last several years, the choices for treatment in newly diagnosed epilepsy have increased because a number of new AEDs have been approved for use in monotherapy. This article reviews randomized, controlled studies that have evaluated the use of new AEDs in monotherapy.

Monotherapy trials: endpoints

Monotherapy antiepileptic drug (AED) trials can optimally provide information concerning efficacy and tolerability of one drug compared with placebo, as well as to different doses or rates of administration. Commonly, a drug is compared with one or more other drugs. The outcome measures will be dictated by the questions being asked. In most comparative studies, the single overall result that best defines success or failure is time of continuation on drug as expressed in a life table. Discontinuation before planned completion of the study implies insufficient efficacy or unacceptable adverse effects. A statistically significant difference between treatments provides important support for recommending the drug or dose with the best outcome. The criteria for continuation/discontinuation are defined in the design based on the expected outcome. The outcome of primary importance is efficacy in prevention of seizures or a decrease in severity. Complete control for the duration of the study is the ultimate goal but in some populations may not be possible. The number of subjects entering remission gives further information about long term outcome. Time to first (nth) seizure provides similar evidence of efficacy. Seizure rates allow comparisons of subjects retained for different lengths of time in the trial. Differences in seizure severity may be of clinical importance and multiple efforts have been made to develop instruments to accurately measure this outcome. Adverse effects of the drugs are the second major outcome. These can be expressed as incidence and/or prevalence. The presence and frequency of side effects will depend on how the study is designed and whether these effects are specifically sought by the investigators. Serious systemic safety outcomes are monitored, but the relative infrequency of occurrence and number of subjects in the trials usually do not provide enough power to detect statistically significant differences except for rash. Tolerability is more easily documented but is difficult to access accurately in the absence of placebo controls. Frequency, severity and persistence are measurable. Specific unwanted types of drug effects can be specifically studied using detailed neuropsychological test batteries. Some information concerning pharmacokinetic properties may be obtained but are better assessed in other types of trials. A final important outcome is the effect of drug therapy on quality of life. Although a favorable finding in this outcome is most desirable, the measures used are much less precise than those for efficacy and adverse effects.

Monotherapy trials: presurgical studies

Presurgical evaluation of patients with refractory partial seizures provides a unique opportunity to perform a placebo-controlled, monotherapy trial. Some patients undergoing presurgical evaluations must have all of their antiepileptic drugs (AEDs) tapered in order to induce seizures and therefore such patients are possible candidates for a placebo-controlled monotherapy trial. Often, EEG monitoring is continued throughout the trial period, thus patients either receiving placebo or whose seizures do not completely respond to the active drug are still evaluated to determine whether or not surgery is feasible, supporting the validity of a trial in this setting. In addition, all patients are, in general, eligible to receive the study drug after the blinded period of the trial, and can therefore be assured of the possible therapeutic benefits of the study. Presurgical inpatients studies have been carried out using felbamate, gabapentin and oxcarbazepine. All patients randomised in these trials were refractory to previous treatment and the studies themselves were short-term and placebo-controlled. These presurgical studies are designed to elucidate AED activity and show statistically significant differences between active and control treatments during short-term therapy, and are therefore of use in fulfilling regulatory requirements. However, these measures of efficacy are distinctly different from those determined during chronic treatment and are therefore not necessarily predictive of clinical usefulness.

Monotherapy trials in antiepileptic drugs: are modified "presurgical studies" a way out of the dilemma?

Monotherapy trials in epilepsy are confronted with a dilemma: either they are in conflict with ethical requirements, or they are scientifically not meaningful. Monotherapy trials, which are performed as controlled studies randomizing patients to ineffective (pseudo)placebo treatment, are incompatible with the Helsinki Declaration. On the other hand, equivalence or noninferiority studies using an active-control design do not permit valid conclusions on the efficacy of the test drug. Therefore, they do not fulfill scientific requirements for trials on new drugs. As an alternative approach, a monotherapy trial design for epilepsy patients undergoing presurgical evaluation was outlined. During presurgical evaluation, antiepileptic drugs are routinely tapered down for seizure recording. This situation is used for a placebo-controlled short-term monotherapy trial. Four trials according to this design have been completed so far. Recently, several points of concern have been raised against this design, especially for matters of ethics and external validity. In the present article, these objections are outlined and discussed. In the proposed modification the randomization and the titration of the test drug or control begins prior to the presurgical investigations. The advantages are: the test drug does not have to be titrated quickly, pure monotherapy conditions are achieved, and the subjects do not have to experience more seizures than are required for the presurgical evaluation.

Assessment of ganaxolone's anticonvulsant activity using a randomized, double-blind, presurgical trial design. Ganaxolone Presurgical Study Group

PURPOSE

A double-blind, randomized, placebo-controlled clinical trial to examine the safety, tolerability, and antiepileptic activity of ganaxolone in patients after withdrawal from other antiepileptic drugs during presurgical evaluations was performed.

METHODS

Fifty-two eligible patients were withdrawn from antiepileptic drugs and randomized to receive ganaxolone (24 patients) or placebo (28 patients) for up to 8 days. Ganaxolone was administered at a dose of 1500 mg/d on day 1 and 1875 mg/d on days 2 to 8. Dosing occurred three times per day: immediately after breakfast, lunch, and dinner.

RESULTS

The primary measure of antiepileptic activity was duration of treatment before withdrawal from the trial. Kaplan-Meier curves depicted a clear separation between treatment groups, with 50% of the ganaxolone-treated patients completing the entire study, compared with 25% of patients treated with placebo. Intent-to-treat survival analyses revealed a trend toward efficacy with ganaxolone (p = 0.0795, log rank test). Covariate analyses revealed a significant treatment effect on survival time in men (p = 0.03). Post-hoc chi2 probe analyses focusing on patients who completed the entire study revealed a significant difference (p = 0.04) between treatment groups. The tolerability of ganaxolone was similar to that of placebo, with adverse events being reported by 79% of patients in the ganaxolone group and 68% of patients in the placebo group.

CONCLUSIONS

Ganaxolone monotherapy was well tolerated for the duration of this clinical trial, and the results provide preliminary evidence that ganaxolone does have antiepileptic activity.

Oxcarbazepine monotherapy for partial-onset seizures: a multicenter, double-blind, clinical trial

OBJECTIVE

To evaluate the safety and efficacy of oxcarbazepine (OXC) 2,400 mg/day versus OXC 300 mg/day monotherapy in patients with medically refractory partial epilepsy.

BACKGROUND

OXC is primarily metabolized by reductase enzymes and, consequently, has a low propensity to inhibit or induce oxidative enzymes and a minimal potential for drug-drug interactions. The efficacy of OXC as monotherapy was shown in several comparative trials in patients with newly diagnosed epilepsy and in hospitalized patients undergoing evaluation for epilepsy surgery.

METHODS

A multicenter, double-blind, randomized, parallel-group trial design was chosen to assess the antiepileptic efficacy of OXC as monotherapy in a refractory epilepsy patient population. Outpatients aged 12 years or older with inadequately controlled partial seizures, with or without secondarily generalized seizures, were enrolled. Patients finished the trial by completing the double-blind phase or by meeting one of four predefined exit criteria: a twofold increase in partial seizure frequency in any 28-day period relative to baseline; a twofold increase in the highest consecutive 2-day partial seizure frequency relative to baseline; occurrence of a single generalized seizure if none occurred during the 6 months prior to randomization; or prolongation or worsening of generalized seizure duration or frequency requiring intervention. Adverse events (AEs), vital signs, and clinical laboratory tests were evaluated.

RESULTS

The percentage of patients meeting one of the exit criteria was significantly lower (p < 0.0001) for the OXC 2400 mg/day group (14/34; 41%) than the OXC 300 mg/day group (42/45; 93%). In addition, there was a significant difference in time to exit in favor of the OXC 2400 mg/day group (p = 0.0001). In the intent-to-treat analysis, 12% of patients in the OXC 2400 mg/day group were seizure-free compared with none in the 300 mg/day group. OXC was well-tolerated, with dizziness, fatigue, somnolence, and nausea being the most frequent AEs. Most of these AEs were transient and rated as mild to moderate in intensity.

CONCLUSION

OXC is safe and effective in the treatment of patients with partial epilepsy previously receiving treatment with other antiepileptic drugs. The results of this trial are consistent with previous monotherapy trials with OXC.

Managing pediatric epilepsy syndromes with new antiepileptic drugs

The management of epilepsy in the pediatric patient requires careful evaluation, classification, and pharmacologic treatment. Despite best efforts on the part of clinicians, approximately 25% of children remain refractory to appropriate medical therapies. The development of an improved classification system and the emergence of several new antiepileptic drugs have enabled some progress in this area, specifically in children with disorders such as Lennox-Gastaut syndrome and infantile spasms, which are notoriously difficult to control. However, limited data are available that define the optimal use of new antiepileptic agents in pediatric patients. To most effectively treat children with epilepsy syndromes, further research must be completed to validate the positive effects described in case reports, open-label clinical trials, and early controlled clinical trials.

Complex Partial Seizures in Adults

Many disorders can mimic complex partial seizure (CPS), and clinicians must be careful to make an accurate diagnosis. Complex partial seizures must be distinguished from generalized-onset seizures (such as absence seizures), which require a different treatment regimen. Treatment of CPS should begin with monotherapy with a standard antiepileptic drug (AED), such as phenytoin or carbamazepine. Increasing evidence indicates that the newer AEDs, such as lamotrigine, topiramate, and possibly gabapentin, are effective as monotherapy. These AEDs may prove to be as effective as the standard AEDs but with fewer adverse effects. All the newer AEDs have significant efficacy when used as add-on treatments, and they may have fewer adverse effects than standard AEDs used in combination. Surgery for epilepsy should be considered in any patient in whom adequate trials of AEDs have failed. The vagus nerve stimulator, a new nonpharmacologic treatment, is a reasonable option in patients in whom AED treatment has failed. Randomized clinical trials comparing older and newer AEDs in the treatment of CPS are needed.

Oxcarbazepine: double-blind, randomized, placebo-control, monotherapy trial for partial seizures

OBJECTIVE

To evaluate the efficacy and safety of oxcarbazepine in a placebo-control trial.

METHODS

A multicenter, double-blind, randomized, placebo-control, two-arm parallel group, monotherapy design was used to compare oxcarbazepine administered 1,200 mg twice daily to placebo in hospitalized patients with refractory partial seizures, including simple and complex partial seizures and partial seizures evolving to secondarily generalized seizures. Patients exited the trial after completing the 10-day double-blind treatment phase or after experiencing four partial seizures, two new-onset secondarily generalized seizures, serial seizures, or status epilepticus, whichever came first.

RESULTS

Analysis of the primary efficacy variable--time to meeting one of the exit criteria--showed a statistically significant effect in favor of oxcarbazepine (p = 0.0001). The secondary efficacy variables--percentage of patients who met one of the exit criteria (p = 0.0001) and total partial seizure frequency per 9 days during the double-blind treatment (p = 0.0001)--were also statistically significant in favor of oxcarbazepine.

CONCLUSION

These results demonstrate that oxcarbazepine given as monotherapy is effective and safe for the treatment of partial seizures in this paradigm.

Felbamate in refractory partial epilepsy

This open-label study was performed to evaluate efficacy and safety of Felbamate (FBM) add-on therapy in drug-refractory partial epilepsy. We evaluated 36 patients (12 males) aged 11-68 years (mean 29.8) in which FBM was titrated gradually from 300 mg/day to a mean total maintenance daily dose of 1936 mg. Patients were monitored according to clinical practice and performed regularly laboratory tests. Mean follow-up of FBM therapy was 10 months (range 2-27). In this study, 5% of patients resulted to be seizure-free, 11% showed a seizure reduction more than 75%, 23% decreased their seizure frequency between 50% and 75% (P = 0.0001). The adverse events which were reported more frequently were: nausea, vomiting, anorexia and weight loss. Even if the patients sample is small FBM proves its efficacy in partial epilepsy, showing a relatively well tolerated profile.

Monotherapy trials with the new antiepileptic drugs: study designs, practical relevance and ethical implications

Traditional randomized clinical trials for the monotherapy assessment of antiepileptic drugs (AED) involve allocation of newly diagnosed patients to long-term treatment with different AEDs in order to determine remission rates and side effect profile. Apart from being time-consuming, however, these trials are unlikely to show significant differences in seizure control between the various drugs, which may lead some regulatory agencies to argue that remission rates could be related to the natural history of the disease rather than to efficacy of the administered drugs. To circumvent this problem, a number of innovative designs for the monotherapy assessment of new AEDs have been developed in recent years. They all share the common feature of being aimed at demonstrating a difference in response rate over a short treatment period between a high dosage of a new AED and some form of suboptimal treatment (placebo or low-dose active control). Patients allocated to suboptimal treatment show unacceptable seizure control more rapidly than patients on high-dose active treatment and therefore they exit the trial at a faster rate: evidence of antiepileptic activity is therefore based on demonstration of differences in rate of deterioration rather than improvement. These trials are conducted with titration schedules, dosages and durations of treatment which are totally unrelated to optimal use of the same AEDs in routine clinical practice. No comparative data with an established reference agent are provided, and allocation of patients to suboptimal treatment raises serious ethical concerns. For these reasons, justification for the continued implementation of these trials is questionable. Randomized long-term comparative trials should be considered the gold-standard for the monotherapy assessment of new AEDs. A review of the literature, however, reveals that long-term trials with new AEDs completed to date had significant shortcomings in their design, including excessively rigid or inappropriate dosing schedules, enrollment of patients with heterogeneous seizure disorders, low statistical power and insufficient duration of follow-up. Because these studies are usually aimed at addressing regulatory requirements, the information obtained cannot be meaningfully applied to routine clinical practice. Large longer-term randomized comparative trials using more pragmatic approaches are highly needed to determine the real value of first-line therapy with new AEDs in patients with well defined seizure disorders.

Evaluation of drug treatment outcome in epilepsy: a clinical perspective

This article provides a comprehensive discussion of clinical outcome measures used in trials aimed at assessing the efficacy and safety of antiepileptic drugs. For efficacy, assessment still relies on careful documentation of changes in ictal activity as determined by seizure counts based on patients recall, direct clinical observation and (for absence seizures) EEG monitoring. In selected cases, assessment of seizure severity may also be indicated. The precise choice of outcome measures is largely dependent upon the specific trial design. In short-term regulatory trials, parameters such as time to nth seizure after randomization (or after achievement of target dosage) may be used as an index of antiepileptic efficacy, but the clinical relevance of such measures is questionable. In add-on trials in refractory patients, changes, in seizure counts and proportion of patients achieving 50%, 75% and 100% reduction in seizure frequency may be appropriate. For long-term monotherapy trials in newly diagnosed patients, proportion of patients achieving prolonged remission (1-year or longer) usually represents the most clinically meaningful efficacy outcome. Retention of patients on the allocated treatment over time is also a valuable measure, but it should be regarded as a composite endpoint because decision to continue treatment is dependent on both efficacy and tolerability. At present, there is no universally accepted method for evaluating side effects, particularly those which can not be documented objectively. Spontaneous reports of symptoms or use of specific checklists have advantages and disadvantages. Studies aimed at ensuring greater standardization in safety assessment should be encouraged, especially with respect to need of obtaining quantitative estimates, and information on both prevalence and incidence of side effects should be reported in all trials.

Felbamate in therapy-resistant epilepsy: an Italian experience. Felbamate Italian Study Group

We evaluated the use of felbamate in 379 adults and children with refractory epilepsies in an open-label, compassionate clinical use setting. Prior to the termination of the program, because of reports of aplastic anemia, 351 patients had completed 2 months of treatment with felbamate at a dose of 2400-3600 mg/day for adults or 30-45 mg/kg/day for children. Of the 246 patients who had a diagnosis of therapy-refractory localization-related epilepsy with or without secondary generalization, 52% (126/246) achieved a seizure reduction of 50% or more, including 10% (25/246) who became seizure free. There was no difference in response rate between adults and children. Of the 80 patients who had a diagnosis of Lennox-Gastaut syndrome (LGS), 60% (48/80) achieved a seizure reduction of 50% or more, including 6% (5/80) who became seizure free. Of the 25 patients with a diagnosis of generalized epilepsy (other than LGS) or undetermined epilepsy whether focal or generalized, 60% (15/25) achieved a seizure reduction of 50% or more, including 12% (3/24) who became seizure free. The results of this uncontrolled study suggest that felbamate could be useful in patients with epilepsies which are refractory to other antiepileptic drugs after careful risk-benefit assessment and consideration of all circumstances involved.