Differences in side effects between a conventional carbamazepine preparation and a slow-release preparation of carbamazepine

Extended-release drug formulations for the treatment of epilepsy

INTRODUCTION

Extended-release (ER) preparations are either available or have been tested for several antiepileptic drugs (AEDs). Indeed, they may be helpful in improving efficacy, tolerability, adherence, compared to the corresponding immediate release (IR) preparations available. The use of ER preparations has been advocated in women of childbearing age and is - depending on the drug - especially helpful in patients who are treated in combination with enzyme inducing AEDs as well as in children.

AREAS COVERED

Clinical and pharmacokinetic studies on ER formulations of AEDs were identified by a PubMed literature research. Further references were added from the authors' personal knowledge and from the reference lists of the identified studies. Reviews and expert commentaries were included, where necessary.

EXPERT OPINION

Unfortunately, studies providing direct comparisons of ER and IR formulations of a given drug are only available for a handful of drugs. ER preparations are especially helpful in drugs with a short elimination half-life and concentration-depending efficacy and tolerability.

Immediate-release versus controlled-release carbamazepine in the treatment of epilepsy

BACKGROUND

Carbamazepine (CBZ) is a commonly used drug for epilepsy that is associated with troublesome adverse events including dizziness, double vision, drowsiness, poor co-ordination and unsteadiness. These adverse events often occur during peaks in drug plasma concentration. These adverse events may limit the daily dose of CBZ that can be tolerated and reduce the chances of seizure control in patients who require high doses. A controlled-release formulation of CBZ delivers the same dose over a longer period of time when compared to a standard immediate-release formulation, thereby reducing post-dose peaks in CBZ plasma concentration and potentially reducing adverse events.This is an updated version of the original Cochrane review published in Issue 12, 2014.

OBJECTIVES

To determine the efficacy of immediate-release CBZ (IR CBZ) versus controlled-release CBZ (CR CBZ) in patients diagnosed with epilepsy.The following review questions were investigated.(1) For newly diagnosed patients commencing CBZ, how do IR and CR formulations compare for efficacy and tolerability?(2) For patients on established treatment with IR CBZ but experiencing unacceptable adverse events, what is the effect on seizure control and the tolerability of a switch to a CR formulation versus remaining on the IR formulation?

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register, CENTRAL, and MEDLINE (Ovid) from inception to 30 August 2016.

SELECTION CRITERIA

Randomised controlled trials comparing IR CBZ to CR CBZ in patients commencing monotherapy and patients presently treated with IR CBZ but experiencing unacceptable adverse events.Primary outcome measures included measures of seizure frequency, incidence of adverse events, proportion of patients with treatment failure and quality of life measures.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, extracted the data and recorded relevant information on a standardised data extraction form. We used the Cochrane risk of bias tool to assess the methodological quality of included studies.The heterogeneity of the included trials with respect to the reporting of outcomes resulted in only a narrative, descriptive analysis being possible for both the categorical and time-to-event data.

MAIN RESULTS

Ten trials (296 participants) fulfilled the criteria for inclusion in this review. Only one study had a low risk of bias. Two studies had a high risk of bias and the rest of the studies were rated as unclear risk of bias. One trial included patients with newly diagnosed epilepsy and nine included patients on treatment with IR CBZ.Eight trials reported heterogeneous measures of seizure frequency with conflicting results. A statistically significant difference was observed in only one trial, with patients prescribed CR CBZ experiencing fewer seizures than patients prescribed IR CBZ.Nine trials reported measures of adverse events. There was a trend in favour of CR CBZ with four trials reporting a statistically significant reduction in adverse events compared to IR CBZ. A further two trials reported fewer adverse events with CR CBZ but the reduction was not statistically significant. One trial found no difference in adverse events, and another trial reported more adverse events in the CR CBZ group than the IR CBZ group, although the increase was not statistically significant.

AUTHORS' CONCLUSIONS

For this update no new eligible studies were identified and the conclusions drawn from the initial review remain unchanged.At present, data from trials do not confirm or refute an advantage for CR CBZ over IR CBZ for seizure frequency or adverse events in patients with newly diagnosed epilepsy.For trials involving epilepsy patients already prescribed IR CBZ, no conclusions can be drawn concerning the superiority of CR CBZ with respect to seizure frequency.There is a trend for CR CBZ to be associated with fewer adverse events when compared to IR CBZ. A change to CR CBZ may therefore be a worthwhile strategy in patients with acceptable seizure control on IR CBZ but experiencing unacceptable adverse events. The included trials were of small size and of poor methodological quality limiting the validity of this conclusion.Randomised controlled trials comparing CR CBZ to IR CBZ and using clinically relevant outcomes are required to inform the choice of CBZ preparation for patients with newly diagnosed epilepsy.

Immediate-release versus controlled-release carbamazepine in the treatment of epilepsy

BACKGROUND

Epilepsy is defined as the tendency to spontaneous, excessive neuronal discharge manifesting as seizures. It is a common disorder with an incidence of 50 per 100,000 per year and a prevalence of 0.5% to 1% in the developed world (Hauser 1993).Carbamazepine (CBZ) is a widely used antiepileptic drug that is associated with a number of troublesome adverse events including dizziness, double vision and unsteadiness. These often occur during peaks in drug plasma concentration. The occurrence of such adverse events may limit the daily dose that can be tolerated and reduce the chances of seizure control for patients requiring higher doses (Vojvodic 2002). A controlled-release formulation of carbamazepine delivers the same dose over a longer period of time when compared to a standard formulation, thereby reducing post-dose peaks and potentially reducing adverse events associated with peak plasma levels.

OBJECTIVES

To determine the efficacy of immediate-release CBZ (IR CBZ) versus controlled-release CBZ (CR CBZ) in patients diagnosed with epilepsy.The following review questions were investigated.(1) For newly diagnosed patients commencing CBZ, how do IR and CR formulations compare for efficacy and tolerability?(2) For patients on established treatment with IR CBZ but experiencing unacceptable adverse events, what is the effect on seizure control and the tolerability of a switch to a CR formulation versus remaining on the IR formulation?

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (10 November 2014), Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO) 11 November 2014, and MEDLINE (Ovid, 1946 to 11 November 2014).

SELECTION CRITERIA

Randomised controlled trials comparing IR CBZ to CR CBZ in patients commencing monotherapy and patients presently treated with IR CBZ but experiencing unacceptable adverse events.Primary outcome measures include seizure frequency, incidence of adverse events, proportion of patients with treatment failure and quality of life measures.

DATA COLLECTION AND ANALYSIS

The methodological quality of each study was assessed with respect to study design, type of control, method and concealment of allocation, blinding and completeness of follow up, and the presence of blinding for assessment of non-fatal outcomes. We did not make use of an overall quality score.Two review authors (GP, MS) independently extracted the data and recorded relevant information on a standardised data extraction form. The trials were assessed for inclusion.The heterogeneity of the included trials resulted in only a narrative, descriptive analysis being possible for both the categorical and time-to-event data.

MAIN RESULTS

Ten trials fulfilled the criteria for inclusion in this review. One trial included patients with newly diagnosed epilepsy and nine included patients on treatment with IR CBZ.Eight trials reported heterogeneous measures of seizure frequency with conflicting results. A statistically significant difference was observed in only one trial, with patients prescribed CR CBZ experiencing fewer seizures than patients prescribed IR CBZ.Nine trials reported measures of adverse events. There was a trend in favour of CR CBZ with four trials reporting a statistically significant reduction in adverse events compared to IR CBZ. A further two trials reported fewer adverse events with CR CBZ but the reduction was not statistically significant. One trial found no difference, with a further trial reporting increased adverse events in the CR CBZ group although the increase was not statistically significant.

AUTHORS' CONCLUSIONS

At present, data from trials do not confirm or refute an advantage for CR CBZ over IR CBZ for seizure frequency or adverse events in patients with newly diagnosed epilepsy.For trials involving epilepsy patients already prescribed IR CBZ, no conclusions can be drawn concerning the superiority of CR CBZ with respect to seizure frequency.There is a trend for CR CBZ to be associated with fewer adverse events when compared to IR CBZ. A change to CR CBZ may therefore be a worthwhile strategy in patients with acceptable seizure control on IR CBZ but experiencing unacceptable adverse events. The included trials were of small size, had poor methodological quality and possessed a high risk of bias, limiting the validity of this conclusion.Randomised controlled trials comparing CR CBZ to IR CBZ and using clinically relevant outcomes are required to inform the choice of CBZ preparation for patients with newly diagnosed epilepsy.

Immediate-release versus controlled-release carbamazepine in the treatment of epilepsy

BACKGROUND

Epilepsy is defined as the tendency to spontaneous, excessive neuronal discharge manifesting as seizures. It is a common disorder with an incidence of 50 per 100,000 per year and a prevalence of 0.5% to 1% (Hauser 1993) in the developed world.Carbamazepine (CBZ) is a widely used antiepileptic drug that is associated with a number of troublesome adverse events including dizziness, double vision and unsteadiness. These often occur during peaks in plasma concentration. The occurrence of such adverse events may limit the daily dose that can be tolerated and reduce the chances of seizure control for patients requiring higher doses (Vojvodic 2002). A controlled-release formulation of carbamazepine delivers the same dose over a longer period of time when compared to a standard formulation, thereby reducing post-dose peaks and potentially reducing adverse events associated with peak plasma levels.

OBJECTIVES

To determine the efficacy of immediate-release CBZ (IR CBZ) versus controlled-release CBZ (CR CBZ) in patients diagnosed with epilepsy. The following hypotheses were tested.(1) For newly diagnosed patients commencing CBZ, how do immediate-release and controlled-release formulations compare for efficacy and tolerability?(2) For patients on established treatment with immediate-release CBZ but experiencing unacceptable adverse events, what is the effect on seizure control and tolerability of a switch to a controlled-release formulation versus remaining on the immediate-release formulation?

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialised Register (5 September 2013), Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 8, 2013) in The Cochrane Library and MEDLINE (1946 to 5 September 2013).

SELECTION CRITERIA

Randomised controlled trials comparing IR CBZ to CR CBZ in patients commencing monotherapy and patients presently treated with IR CBZ but experiencing unacceptable adverse events.Primary outcome measures include seizure frequency, incidence of adverse events, proportion with treatment failure and quality of life measures.

DATA COLLECTION AND ANALYSIS

The methodological quality of each study was assessed with respect to study design, type of control, method and the concealment of allocation, blinding and completeness of follow up, and the presence of blinding for assessment of non-fatal outcomes. We did not make use of an overall quality score.Two review authors (GP, MS) independently extracted the data and recorded relevant information on a standardised data extraction form. Results were assessed for inclusion.The heterogeneity of the included trials resulted in only a narrative, descriptive analysis being possible for both the categorical and time-to-event data.

MAIN RESULTS

Ten trials fulfilled the criteria for inclusion in this review. One trial included patients with newly diagnosed epilepsy and nine included patients on treatment with IR CBZ.Eight trials reported heterogeneous measures of seizure frequency with conflicting results. A statistically significant difference was observed in only one trial, with patients prescribed CR CBZ experiencing fewer seizures than patients prescribed IR CBZ.Nine trials reported measures of adverse events. There was a trend in favour of CR CBZ with four trials reporting a statistically significant reduction in adverse events compared to IR CBZ. A further two trials reported fewer adverse events with CR CBZ but the reduction was not statistically significant. One trial found no difference, with a further trial reporting increased adverse events in the CR CBZ group although not statistically significant.

AUTHORS' CONCLUSIONS

At present, data from trials do not confirm or refute an advantage for CR CBZ over IR CBZ for seizure frequency or adverse events in patients with newly diagnosed epilepsy.For trials involving epilepsy patients already prescribed IR CBZ, no conclusions can be drawn concerning the superiority of CR CBZ with respect to seizure frequency.There is a trend for CR CBZ to be associated with fewer adverse events when compared to IR CBZ. A change to CR CBZ may therefore be a worthwhile strategy in patients with acceptable seizure control on IR CBZ but experiencing unacceptable adverse events. The included trials were of small size, poor methodological quality and possessed a high risk of bias, limiting the validity of this conclusion.Randomised controlled trials comparing CR CBZ to IR CBZ and using clinically relevant outcomes are required to inform the choice of CBZ preparation for patients with newly diagnosed epilepsy.

Immediate-release versus controlled-release carbamazepine in the treatment of epilepsy

BACKGROUND

Epilepsy is defined as the tendency to spontaneous, excessive neuronal discharge, manifesting as seizures. It is a common disorder with an incidence of 50 per 100,000 per year and a prevalence of 0.5% to 1% (Hauser 1993) in the developed world.Carbamazepine is a commonly used antiepileptic drug that is associated with a number of troublesome adverse events including dizziness, double vision and unsteadiness. These often occur during peaks in plasma concentration. The occurrence of such adverse events may limit the daily dose that can be tolerated and reduce the chances of seizure control for patients requiring higher doses (Vojvodic 2002). A controlled-release formulation of carbamazepine delivers the same dose over a longer period of time when compared to a standard formulation, thereby reducing post-dose peaks and potentially reducing adverse events associated with peak plasma levels.

OBJECTIVES

To determine the efficacy of immediate-release carbamazepine (IR CBZ) versus controlled-release carbamazepine (CR CBZ) in patients with newly diagnosed epilepsy.To determine the efficacy of switching to CR CBZ in patients treated with IR CBZ but experiencing unacceptable adverse events.

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group Specialised Register (25 September 2009), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 4), and MEDLINE (1950 to September week 3, 2009).

SELECTION CRITERIA

Randomised controlled trials comparing IR CBZ to CR CBZ in patients commencing monotherapy and patients presently treated with IR CBZ but experiencing unacceptable adverse events.Primary outcome measures include seizure frequency, incidence of adverse events, proportions with treatment failure and quality of life measures.

DATA COLLECTION AND ANALYSIS

The methodological quality of each study was assessed with respect to study design, type of control, method and concealment of allocation, blinding and completeness of follow up, and the presence of blinding for assessment of non-fatal outcomes. We did not make use of an overall quality score.Two review authors (GP, MS) independently extracted the data and recorded relevant information on a standardised data extraction form. Results were assessed for inclusion.The heterogeneity of the included trials resulted in only a narrative, descriptive analysis being possible for both categorical and time-to-event data.

MAIN RESULTS

Ten trials fulfilled the criteria for inclusion in this review. One trial included patients with newly diagnosed epilepsy and nine included patients on treatment with IR CBZ.Eight trials reported heterogeneous measures of seizure frequency with conflicting results. A statistically significant difference was observed in only one trial, with patients prescribed CR CBZ experiencing fewer seizures than patients prescribed IR CBZ.Nine trials reported measures of adverse events. There was a trend in favour of CR CBZ with four trials reporting a statistically significant reduction in adverse events compared to IR CBZ. A further two trials reported fewer adverse events with CR CBZ, not statistically significant. One trial found no difference, with a further trial reporting increased adverse events in the CR CBZ although not statistically significant.

AUTHORS' CONCLUSIONS

At present, data from trials do not confirm or refute an advantage for CR CBZ over IR CBZ for seizure frequency or adverse events in patients with newly diagnosed epilepsy.For trials involving epilepsy patients already prescribed IR CBZ, no conclusions can be drawn concerning superiority of CR CBZ with respect to seizure frequency.There is a trend for CR CBZ to be associated with fewer adverse events when compared to IR CBZ. A change to CR CBZ may therefore be a worthwhile strategy in patients with acceptable seizure control on IR CBZ but experiencing unacceptable adverse events. The included trials were of small size, poor methodological quality and possessed a high risk of bias, limiting the validity of this conclusion.Randomised controlled trials comparing CR CBZ to IR CBZ and using clinically relevant outcomes are required to inform the choice of CBZ preparation for patients with newly diagnosed epilepsy.

Levetiracetam extended release and levetiracetam immediate release as adjunctive treatment for partial-onset seizures: an indirect comparison of treatment-emergent adverse events using meta-analytic techniques

The safety profiles of once-daily adjunctive levetiracetam (LEV) extended release (XR) (1000mg/day) and adjunctive LEV immediate release (IR) (500mg twice daily) were compared using data from three randomized, placebo (PBO)-controlled phase III clinical trials in patients with partial-onset seizures. MedDRA 9.0 treatment-emergent adverse events (TEAEs) were indirectly compared using meta-analytic techniques, including calculation of risk difference (RD) and mixed-effects analysis. Statistical significance was set at 10% alpha risk, the normative value for these analyses. Data from 555 patients older than 16 (204 LEV IR, 70 LEV XR, 281 PBO) were analyzed. Following adjustment for incidence of placebo TEAEs, LEV XR showed statistically significantly lower rates of TEAEs than LEV IR across nervous system disorders (RD=-18%, P=0.03), psychiatric disorders (RD=-11%, P=0.08), and metabolism and nutrition disorders (RD=-3%, P=0.08). Among nervous system disorders, the RD for headache favored LEV XR (RD=-11%, P=0.08). These results suggest that adjunctive LEV XR may be associated with a lower incidence of nervous system, psychiatric, and nutritional and metabolic TEAEs as compared with LEV IR. However, this difference was observed at a broad scale and not at a specific TEAE level except for headache.

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.

Quality of life in seizure-free patients with epilepsy on monotherapy

Epilepsy is a multifaceted chronic disorder which has diverse and complex effects on the well-being of the patient. Although it is evident that seizure type and frequency play a critical role in the quality of life (QOL) of patients with epilepsy, it is less clear what the major determinants are that influence QOL in seizure-free patients receiving monotherapy. The aim of this study was to evaluate demographic, clinical, and socioeconomic factors influencing the QOL of seizure-free patients receiving monotherapy. All participants were patients from four medical centers who had epilepsy, were on monotherapy, and had been seizure-free for at least 1 year. Responders completed three questionnaires on demographic and clinical information, QOL, and antiepileptic drug (AED) side effects during routine follow-up visits in the epilepsy clinics. We present the data of 103 patients: 59 females (57.3%), mean age 37.75+/-13.66 years. Treatment side effects and unemployment (p<0.0001, p=0.037, respectively) were significant predictors for poor overall QOL, whereas age, gender, education, family status, comorbidity, seizure type, age of seizure onset, and epilepsy duration did not significantly affect overall QOL. There was no significant difference in side effects and QOL between patients receiving older versus newer AEDs. Ninety-four (92.2%) patients reported experiencing at least one side effect of AEDs when queried about specific symptoms, while only 11 (10.7%) patients replied affirmatively when asked whether they experienced "any" side effects. The most common side effects involved the central nervous system. In conclusion, this study reveals that the most significant factor influencing the QOL in seizure-free patients on monotherapy is AED side effects. QOL is a crucial component in the clinical care of patients with epilepsy, and physicians should take the time to ask specific questions on side effects of AEDs.

Every-12-hour administration of extended-release divalproex in patients with epilepsy: impact on plasma valproic acid concentrations

Extended-release divalproex sodium (divalproex-ER) biopharmaceutics after every-12-hour (q12h) administration was compared with that of once-daily divalproex-ER and conventional divalproex given every 6 hours (q6h) in a multiple-dose (14-day), randomized, three-period crossover design study in 24 patients with epilepsy concomitantly receiving enzyme-inducing antiepileptic medication(s). Plasma valproic acid (VPA) minimum concentration (Cmin) for divalproex-ER q12h was higher than the once-daily divalproex-ER Cmin (P=0.043). Once-daily divalproex-ER Cmin values were not different from those for divalproex q6h, suggesting that adequate trough steady-state concentrations are maintained with once daily dosing, despite enzyme-inducing comedication. The degree of peak-trough fluctuation (DFL, calculated as (Cmax-Cmin)/Cavg) in VPA concentration was less with both q12h (35.2% less) and once-daily (16.9% less) divalproex-ER regimens compared with q6h divalproex (P0.024). The DFL for divalproex-ER dosed as a q12h regimen was 22% less than that for once-daily divalproex-ER (P=0.02). The DFL in VPA concentration with divalproex-ER can be minimized with once-daily administration and more so with q12h administration, compared with conventional enteric-coated divalproex taken q6h.

Patterns of care, outcomes, and direct health plan costs of antiepileptic therapy: a pharmacoeconomic analysis of the available carbamazepine formulations

BACKGROUND

Although generic formulations of immediate-release carbamazepine (IR-CBZ) are available, extended-release delivery systems may offer important advantages, including the convenience of less-frequent administration and smaller peak-to-trough serum carbamazepine (CBZ) fluctuations.

OBJECTIVE

The aim of this study was to compare the patterns of pharmacotherapy, rates of adverse events, and the utilization costs among patients treated with the available CBZ formulations (ie, generic and branded IR-CBZ, and extended-release CBZ (ER-CBZ) capsules [Carbatrol, Shire US Inc., Wayne, Pennsylvania] and tablets [Tegretol-XR, Novartis Pharmaccuticals Corporation, East Hanover, New Jersey]).

METHODS

Data were retrieved from the PharMetrics patient-centric database (which contains integrated claims data for almost 36 million unique patients from 61 US health plans) for patients who were diagnosed with epilepsy and initiated CBZ between July 1999 and June 2001. Patient demographic and clinical characteristics, adverse events, discontinuations, CBZ therapy switches, and utilization and costs for related care subsequent to treatment initiation were recorded. Annual rates of adverse events and discontinuations were calculated, and the risks of these events were compared across treatment groups.

RESULTS

Data were gathered for 1737 patients. The branded CBZ group was demographically and clinically different than the other groups (ie, migraine and cerebral palsy prevalence) and therefore was excluded from event-risk analyses. Results of the proportional hazards regression analysis indicated that Tegretol-XR patients were more likely to experience common central nervous system (CNS)-related adverse events relative to Carbatrol (hazard ratio, 1.67; P = 0.043). A lower percentage of subjects switched off ER-CBZ relative to IR-CBZ (Carbatrol, 5.2%; Tegretol-XR, 5.7%; generic IR-CBZ, 13.0%; branded IR-CBZ, 16.7%). Differences in mean payments for epilepsy-related health care services at 1 year among Carbatrol, Tegretol-XR, and branded or generic CBZ did not reach statistical significance.

CONCLUSIONS

Among the available CBZ formulations, Carbatrol was associated with a lower incidence of common CNS adverse events. ER-CBZ formulations were also associated with reduced likelihood of therapy discontinuation or switching CBZ medications, relative to patients taking generic IR-CBZ, in this retrospective data analysis.

Assessment of adverse events and quality of life in epilepsy: design of a new community-based trial

Improving health-related quality of life (HRQOL) has become recognized as an essential component of treating patients with epilepsy. In recent years, several rating scales have been developed that focus on both common adverse effects and various aspects of HRQOL that are more relevant to this patient population. Increasingly, such assessments are being incorporated into clinical trials, as it becomes clear that improvements in overall quality of life are an important feature of drug therapy. Here we present the design of a large, community-based trial evaluating the effects of switching from immediate-release carbamazepine to twice-daily, beaded, extended-release carbamazepine (Carbatrol). As this trial involves switching formulations of the same compound, we expect to find only small differences in efficacy but significant differences in tolerability and quality-of-life measures. To identify appropriate instruments that could measure these factors, here we review several epilepsy-specific scales used to monitor adverse events and HRQOL and discuss their potential utility in the context of the proposed trial.

Improved CNS tolerability following conversion from immediate- to extended-release carbamazepine

OBJECTIVES

Tolerability of 'narrow therapeutic ratio' (NTR) antiepileptic drugs may improve with uniform drug delivery. We determined whether conversion from immediate-release carbamazepine (IR-CBZ) to extended-release carbamazepine (ER-CBZ) decreased the incidence of CNS side-effects associated with drug concentration oscillations.

METHODS

We compared CNS side effects and seizure frequency for patients with partial-onset seizures (n = 61) treated with IR-CBZ for > or =1 year with conversion to ER-CBZ for > or =1 year. We compared tolerability findings with absorption variability of the formulations.

RESULTS

Incidence of CNS side-effects decreased from 49% during IR-CBZ treatment to 20% following conversion to ER-CBZ. Patients also had improved tolerability of high doses (> or =1200 mg/day) during ER-CBZ treatment. Pharmacokinetic analysis showed absorption and drug concentration were much more variable for the immediate-release formulation.

CONCLUSIONS

This study suggests that ER-CBZ formulations, with smoother drug delivery and less variable absorption, provide improved CNS tolerability compared with immediate-release formulations.

Health-related quality of life in senior adults with epilepsy: what we know from randomized clinical trials and suggestions for future research

OBJECTIVE

The goal of this work was to review the randomized controlled trial (RCT) literature on antiepileptic medication effects on health-related quality of life in seniors with epilepsy.

METHODS

Studies published from 1998 to June 2002 were identified by searching through Medline and the Cochrane Clinical Trials Register. Pre-1998 RCTs identified by Baker et al. [Epilepsia 41 (2003) 1357] were also examined for relevance to the present review. Studies were reviewed if they included a RCT design and included epilepsy patients over the age of 60.

RESULTS

A total of 85 clinical trials were reviewed. Of the 85 studies reviewed only 37 RCT studies included patients over the age of 60. However, formal quality-of-life outcome assessment was not performed in any of the RCTs that included senior adults, and only six studies provided formal quantitative analyses of AED effects in the form of adverse events incidence and participant withdrawal rates. For the most part, early study withdrawal rates were substantial for seniors and adverse events were very common. Two studies reporting on the cognitive and behavioral effects of study AEDs indicated only modest impact when AED monotherapy was kept at therapeutic levels.

CONCLUSIONS

Despite growing appreciation for quality-of-life, issues in the management of epilepsy little current empirical guidance is available for elderly with epilepsy. There exists virtually no information on elderly patient preferences and goals for epilepsy treatment outcomes, and available data primarily concerns younger adults. Despite some encouraging preliminary evidence from this review suggesting that conservative AED treatment may have a more favorable quality of life-related outcome, more conclusive statements await further systematic investigation.

Future prospects for the drug treatment of epilepsy

Great progress has been made in the last 150 years in the pharmacological management of epilepsy, and, despite the increasing number of technological advances available, antiepileptic drugs (AEDs) remain the mainstay of treatment for the vast majority of patients with epilepsy. This review looks at possible avenues of development in the drug treatment of epilepsy. The strengths and weaknesses of those AEDs which are currently licensed are examined, and ways in which their use may be improved are discussed (e.g. rational combinations, use of new formulations). Potentially new targets that may allow the development of effective treatments are highlighted (neuroimmunological manipulation, decreasing inherent drug resistance mechanisms, and modification of adenosine neurotransmission), and a summary of the most promising AEDs currently in development is provided [e.g. carabersat, ganaxolone, harkoseride, MDL 27192, safinamide (NW 1015), pregabalin, retigabine, talampanel, valrocemide, losigamone and BIA 2093].

Visual and auditory evoked potentials during long-term vigabatrin treatment in children and adolescents with epilepsy

OBJECTIVES

The aim of the study was to estimate the effects of Vigabatrin (VGB) as add-on therapy on visual (VEP) and brain-stem (BAEP) evoked potentials.

METHOD

The investigation covered 100 epileptic patients from 8 to 18 years of age. The treatment included therapy with carbamazepine (CBZ) or valproate acid (VPA) using slow release formulations of these AEDs. Combination therapy was administered using add-on VGB in the recommended dose 57.4+/-26.5 mg/kg body mass/day. VEP and BAEP evoked potentials were recorded by means of Multiliner (Toennies, Germany). The obtained values were compared with age matched control group.

RESULTS

Compared to control groups, significant differences in epileptic groups emerged in latencies of the peak III, V along with the interpeak intervals I-III of BAEP. Also VEP studies showed the reduction of N75/P100 and P100/N145 amplitudes.

CONCLUSIONS

Adding VGB did not significantly increase the percentage of pathological abnormalities observed from EPs. Our electrophysiological studies demonstrate abnormalities in EPs parameters due to subclinical toxicity induced by AEDs. Major alterations produced bitherapy of VPA-SR + VGB and minor SR formulations of CBZ or VPA.

Quality-of-life and behavioral outcome measures in randomized controlled trials of antiepileptic drugs: a systematic review of methodology and reporting standards

PURPOSE

To review the methodology and use of quality-of-life and behavioral measures used in randomized controlled trials (RCTs) of antiepileptic drugs in patients with epilepsy.

METHODS

Trial reports were found by searching a previously developed comprehensive database of epilepsy RCTs and searching through journals by hand. Inclusion and exclusion criteria were applied, and methodological and quality-of-life and behavioral measure data were extracted.

RESULTS

There were 52 different measures used in 46 trials, with the Profile of Mood States, the Minnesota Multiphasic Personality Inventory, and the Washington Psychosocial Seizure Inventory being applied the most frequently. Overall, evidence of the reliability, validity, and sensitivity of measures used in populations of people with epilepsy was sparse. There was also little information on the clinical interpretation of the results.

CONCLUSION

Our results highlight a consistent failure to apply quality-of-life and behavioral measures in RCTs in a systematic way. We found repeated evidence of researchers' failure to review the use of previous measures and selection of measures without evidence of their appropriateness for use in a population with epilepsy. We recommend the use of quality-of-life and behavioral measures in RCTs with proven psychometric properties in a population with epilepsy.

Circadian carbamazepine toxicity

Owing to marked fluctuations in plasma concentrations, circadian CNS toxicity (maximum in the early afternoon) occurred in a 69-year-old female patient being treated with an instant-release formulation of carbamazepine (CBZ). The neurologic syndrome was reversible after administration of the same daily dose as sustained-release formulation. This case illustrates the importance of correct timing of blood sampling to detect drug-induced toxicity and of use of sustained-release formulations in antiepileptic therapy with CBZ.

Double dummy comparison between once and twice daily dosing with modified-release carbamazepine in epileptic patients

1. Fourteen patients with refractory epilepsy on a twice daily regimen of modified-release carbamazepine (CBZ-MR. Tegretol Retard. Ciba Pharmaceuticals) completed a balanced, double-blind, double dummy, random order, crossover comparison of 8 weeks treatment with once (o.d.) and twice daily (b.d.) dosing. In order to obtain a profile of serum CBZ concentrations over 24 h on once daily dosing, patients were randomised to taking it in the morning (o.d. a.m.) or evening (o.d. p.m.) for 4 weeks. Each treatment was taken with a placebo of the other and total tablet numbers were matched. Blood sampling was undertaken 0, 2, 4, 6, 8, 10, 12 and 24 h after the morning tablets at the end of each 4 week treatment period. 2. Overall, trough serum drug concentrations (Cmin) were lower with once daily dosing (Cmin: b.d. 7.5 mg l-1, o.d. 6.5 mg l-1, P < 0.05, 95% CI of the difference -1.3 to -0.1), but no significant differences were found in average (Cav) or peak (Cmax) concentrations, AUC values or fluctuations in CBZ concentrations. 3. Pharmacokinetic parameters for CBZ 10.11 epoxide, the active metabolite of CBZ did not differ significantly between the dosage schedules. 4. Seizure control was similar during once and twice daily dosing with CBZ-MR (median seizures/month (range): b.d. 1 (0-14.5), o.d. 0.5 (0-11), NS, 95% CI of the difference -1.8 to + 0.25). 5. There were no differences in psychomotor performance between the treatment periods. 6. More patients (n = 11) preferred treatment (P < 0.05) with once daily than twice daily dosing (n = 3) with CBZ-MR. 7. Once daily dosing with CBZ-MR should be possible in the majority of patients receiving the drug as monotherapy.

Comparative bioavailability of carbamazepine from two slow-release preparations

In order to compare the multiple-dose bioavailability of carbamazepine (CBZ) from 2 slow-release preparations, Neurotol slow and Tegretol Retard, a single-blind, randomized, cross-over study was carried out. 21 adult patients with epilepsy were enrolled in the study. At the end of both 2-week treatment periods, a blood sample series was drawn after the administration of the morning CBZ dose. The serum concentrations of CBZ, CBZ-10,11-epoxide (CBZE) and 10,11-dihydro-10,11-trans-dihydroxy-CBZ (CBZD) were measured using HPLC. The mean bioavailability of CBZ from Neurotol slow was 11% (P = 0.002) higher than from Tegretol Retard. Owing to the better bioavailability, the peak (Cmax), lowest (Cmin) and mean (Css) concentrations of CBZ were also significantly higher during Neurotol slow treatment. Fluctuation of serum CBZ concentrations (Cmax-Cmin/Css, ADCss/AUC0-12h) did not differ significantly between the 2 treatments; neither did tmax. Similar results were obtained with CBZE and CBZD. There were more epileptic seizures on Tegretol Retard than on Neurotol slow, but the difference was not statistically significant. We conclude that there are significant differences in the bioavailability of CBZ from these 2 slow-release preparations.

Pharmacokinetic evaluation of sustained release formulations of antiepileptic drugs. Clinical implications

Epilepsy is a chronic disease that requires long term therapy, and most of the established antiepileptic drugs (the exception is phenobarbital) must be administered several times daily. This results in compliance problems and fluctuations in plasma concentrations which may lead to subtherapeutic and potentially toxic levels. Development of sustained release formulations of the existing antiepileptic agents may improve antiepileptic therapy. At present, only the following 4 major drugs are used for the treatment of epilepsy: phenobarbital, phenytoin, carbamazepine and valproic acid. Of these, only the latter 2 are suitable candidates for sustained release formulations. This review, therefore, focuses on the evaluation and clinical implications of sustained release formulations of valproic acid and carbamazepine.

Monotherapy with conventional and controlled-release carbamazepine: a double-blind, double-dummy comparison in epileptic patients

1. Twenty-one epileptic patients completed a double-blind, double-dummy, random order, crossover comparison of conventional carbamazepine (CBZ, Tegretol, Ciba-Geigy) with a new controlled-release formulation (CBZ-CR, Tegretol Retard). All participants were stabilised on maximally tolerated doses of CBZ as monotherapy (one twice daily, twelve three times daily, eight four times daily). Each preparation was taken with a matched placebo of the other for 4 weeks. 2. Peak serum CBZ concentrations (mean +/- s.e. mean) were lower (CBZ 11.4 +/- 0.4 mg l-1; CBZ-CR 10.4 +/- 0.5 mg l-1; P less than 0.01) and times to peak longer (CBZ 3.6 +/- 0.5 h, CBZ-CR 5.2 +/- 0.7 h, P less than 0.01) during CBZ-CR treatment. Mean CBZ concentrations, however, were also slightly reduced with the new formulation (CBZ 9.9 +/- 0.3 mg l-1; CBZ-CR 9.1 +/- 0.5 mg l-1, P less than 0.05) and this was associated with greater seizure frequency (CBZ 2.8 +/- 1.2, CBZ-CR 3.8 +/- 0.9; P less than 0.05) during the CBZ-CR treatment phase. 3. Diurnal fluctuations (CBZ 41 +/- 3%, CBZ-CR 28 +/- 2%, P less than 0.01) and variations (CBZ 53 +/- 5%, CBZ-CR 33 +/- 3%; P less than 0.01) in serum CBZ concentration were substantially less with CBZ-CR and were similar to those calculated during a 6 or 8 hourly dosage interval with conventional CBZ (fluctuation 33 +/- 3%, variation 42 +/- 5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple-dose pharmacokinetic study with a slow-release carbamazepine preparation

The pharmacokinetics, clinical efficacy and side effects of carbamazepine (CBZ) in the steady-state condition were studied using a slow-release preparation (SR), Neurotol Slow, and a conventional preparation (C), Tegretol. Eighteen adult epileptic patients under CBZ therapy were evaluated in this single-blind, randomized cross-over study. The previous daily CBZ dose was kept unchanged and divided into 2 daily doses during two 2 week study periods. At the end of each period blood samples were drawn at frequent intervals for 12 h after the administration of the morning CBZ dose. Serum concentrations of unchanged CBZ and its main metabolite, carbamazepine-10,11-epoxide (CBZE), were determined by HPLC. Peak concentrations of CBZ and CBZE were significantly lower, and the time-lapse before CBZ reached its peak was significantly longer during SR treatment. The fluctuations in serum CBZ and CBZE were significantly lower during SR treatment. There was no significant difference in bioavailability between the 2 preparations. The number of epileptic seizures was 31 during SR and 57 during C treatment. Side effects were more common during C treatment. The occurrence of dizziness was significantly lower with SR treatment than with C treatment. We conclude that greater stability in serum CBZ and CBZE concentrations can be obtained by using an SR of CBZ, without reducing the bioavailability of the drug.