Flunarizine for treatment of partial seizures: results of a concentration-controlled trial

Real life retrospective study of cannabidiol therapy in alternating hemiplegia of childhood

BACKGROUND

Many alternating hemiplegia of childhood (AHC) patients have received Cannabidiol (CBD) but, to our knowledge, there are no published data available.

GOALS

Test the hypothesis that CBD has favorable effects on AHC spells.

METHODS

Retrospective review of available data of AHC patients who received CBD. Primary analysis: Clinical Global Impression Scale of Improvement (CGI-I) score for response of AHC spells to CBD with calculation of 95% confidence interval (CI) for rejection of the null hypothesis. Secondary analyses, performed to achieve an understanding of the effect of CBD as compared to flunarizine, were CGI-I scores of 1) epileptic seizures to CBD, 2) AHC spells to flunarizine, 3) epileptic seizures to flunarizine. Also, Mann-Whitney test was done for comparison of CGI-I scores of CBD and flunarizine to both AHC spells and seizures.

RESULTS

We studied 16 AHC patients seen at Duke University and University of Lyon. CI of CGI-I scores for AHC spells in response to CBD and to flunarizine, each separately, indicated a positive response to each of these two medications: neither overlapped with the null hypothesis score, 4, indicating significant positive responses with p < 0.05 for both. These two scores also did not differ (p = 0.84) suggesting similar efficacy of both: CBD score was 2 ± 1.1 with a 95% CI of 1.5-2.6 and flunarizine score was 2.3 ± 1.3 with a 95% CI of 1.7-3.1. In patients who had seizures, CI calculations indicated a positive effect of CBD on seizure CGI scores but not of flunarizine on seizure scores. CBD was well tolerated with no patients discontinuing it due to side effects and with some reporting positive behavioral changes.

CONCLUSION

Our study indicates a real-life positive effect of CBD on AHC type spells.

Alternating hemiplegia of childhood

Alternating hemiplegia of childhood (AHC) is characterized by recurrent episodes of hemiplegia which may alternate sides between attacks. The condition is associated with severe neurodevelopmental disorder presenting in early infancy, and may encompass a wide range of other paroxysmal manifestations (e.g., dystonia, nystagmus, dysautonomia) and pervasive neurological disabilities (e.g., developmental delay, learning disabilities, choreoathetosis, and ataxia). Epileptic seizures are particularly common among patients with AHC. Diagnosis is usually based on history and clinical grounds using the Aicardi criteria. Mutations in the ATP1A3 gene are implicated in the disease pathology of the condition, as well as several other neurodevelopmental disorders, suggesting AHC forms part of a spectrum of overlapping clinical syndromes rather than a distinct clinical entity per se. Management of patients with AHC includes the rapid induction of sleep during paroxysmal attacks and the avoidance of identified triggers. Pharmacotherapeutic treatments have a role in managing epileptic seizures, as well as in the prevention of paroxysmal attacks wherein flunarizine remains the treatment of choice.

Novel E815K knock-in mouse model of alternating hemiplegia of childhood

De novo mutations causing dysfunction of the ATP1A3 gene, which encodes the α3 subunit of Na⁺/K⁺-ATPase pump expressed in neurons, result in alternating hemiplegia of childhood (AHC). AHC manifests as paroxysmal episodes of hemiplegia, dystonia, behavioral abnormalities, and seizures. The first aim of this study was to characterize a novel knock-in mouse model (Atp1a3^E815K+/-, Matoub, Matb^+/-) containing the E815K mutation of the Atp1a3 gene recognized as causing the most severe and second most common phenotype of AHC with increased morbidity and mortality as compared to other mutations. The second aim was to investigate the effects of flunarizine, currently the most effective drug used in AHC, to further validate our model and to help address a question with significant clinical implications that has not been addressed in prior studies. Specifically, many E815K patients have clinical decompensation and catastrophic regression after discontinuing flunarizine therapy; however, it is not known whether this is congruent with the natural course of the disease and is a result of withdrawal from an acute beneficial effect, withdrawal from a long-term protective effect or from a detrimental effect of prior flunarizine exposure. Our behavioral and neurophysiological testing demonstrated that Matb^+/- mice express a phenotype that bears a strong resemblance to the E815K phenotype in AHC. In addition, these mice developed spontaneous seizures with high incidence of mortality and required fewer electrical stimulations to reach the kindled state as compared to wild-type littermates. Matb^+/- mice treated acutely with flunarizine had reduction in hemiplegic attacks as compared with vehicle-treated mice. After withdrawal of flunarizine, Matb^+/- mice that had received flunarizine did neither better nor worse, on behavioral tests, than those who had received vehicle. We conclude that: 1) Our mouse model containing the E815K mutation manifests clinical and neurophysiological features of the most severe form of AHC, 2) Flunarizine demonstrated acute anti-hemiplegic effects but not long-term beneficial or detrimental behavioral effects after it was stopped, and 3) The Matb^+/- mouse model can be used to investigate the underlying pathophysiology of ATP1A3 dysfunction and the efficacy of potential treatments for AHC.

Diagnosis and Treatment of Alternating Hemiplegia of Childhood

OPINION STATEMENT

The diagnosis and treatment of patients with Alternating Hemiplegia of Childhood (AHC) and related disorders should be provided by a multidisciplinary team experienced with the spectrum of presentations of this disease, with its related disorders, with its complex and fluctuating manifestations, and with cutting edge advances occurring in the field. Involvement in research to advance the understanding of this disease and partnership with international collaborators and family organizations are also important. An example of such an approach is that of The Duke AHC and Related Disorders Multi-Disciplinary Clinic and Program, which, in partnership with the Cure AHC Foundation, has developed and applied this approach to patients seen since early 2013. The program provides comprehensive care and education directly to AHC patients and their families and collaborates with referring physicians on the care of patients with AHC whether evaluated at Duke clinics or not. It also is involved in clinical and basic research and in collaborations with other International AHC Research Consortium (IAHCRC) partners. The clinic is staffed with physicians and experts from Neurology, Cardiology, Child Behavioral Health, Medical Genetics, Neurodevelopment, Neuropsychology, Nursing, Physical and Occupational Therapies, Psychiatry, Sleep Medicine, and Speech/Language Pathology. Patients are seen either for full comprehensive evaluations that last several days or for targeted evaluations with one or few appointments.

Analysis of interval-censored recurrent event processes subject to resolution

Interval-censored recurrent event data arise when the event of interest is not readily observed but the cumulative event count can be recorded at periodic assessment times. In some settings, chronic disease processes may resolve, and individuals will cease to be at risk of events at the time of disease resolution. We develop an expectation-maximization algorithm for fitting a dynamic mover-stayer model to interval-censored recurrent event data under a Markov model with a piecewise-constant baseline rate function given a latent process. The model is motivated by settings in which the event times and the resolution time of the disease process are unobserved. The likelihood and algorithm are shown to yield estimators with small empirical bias in simulation studies. Data are analyzed on the cumulative number of damaged joints in patients with psoriatic arthritis where individuals experience disease remission.

The expanding spectrum of neurological phenotypes in children with ATP1A3 mutations, Alternating Hemiplegia of Childhood, Rapid-onset Dystonia-Parkinsonism, CAPOS and beyond

BACKGROUND

ATP1A3 mutations have now been recognized in infants and children presenting with a diverse group of neurological phenotypes, including Rapid-onset Dystonia-Parkinsonism (RDP), Alternating Hemiplegia of Childhood (AHC), and most recently, Cerebellar ataxia, Areflexia, Pes cavus, Optic atrophy, and Sensorineural hearing loss (CAPOS) syndrome.

METHODS

Existing literature on ATP1A3-related disorders in the pediatric population were reviewed, with attention to clinical features and associated genotypes among those with RDP, AHC, or CAPOS syndrome phenotypes.

RESULTS

While classically defined phenotypes associated with AHC, RDP, and CAPOS syndromes are distinct, common elements among ATP1A3-related neurological disorders include characteristic episodic neurological symptoms and signs that vary in severity, duration, and frequency of occurrence. Affected children typically present in the context of an acute onset of paroxysmal, episodic neurological symptoms ranging from oculomotor abnormalities, hypotonia, paralysis, dystonia, ataxia, seizure-like episodes, or encephalopathy. Neurodevelopmental delays or persistence of dystonia, chorea, or ataxia after resolution of an initial episode are common, providing important clues for diagnosis.

CONCLUSIONS

The phenotypic spectrum of ATP1A3-related neurological disorders continues to expand beyond the distinct yet overlapping phenotypes in patients with AHC, RDP, and CAPOS syndromes. ATP1A3 mutation analysis is appropriate to consider in the diagnostic algorithm for any child presenting with episodic or fluctuating ataxia, weakness or dystonia whether they manifest persistence of neurological symptoms between episodes. Additional work is needed to better identify and classify affected patients and develop targeted treatment approaches.

A dynamic Mover-Stayer model for recurrent event processes subject to resolution

In studies of affective disorder, individuals are often observed to experience recurrent symptomatic exacerbations warranting hospitalization. Interest may lie in modeling the occurrence of such exacerbations over time and identifying associated risk factors. In some patients, recurrent exacerbations are temporally clustered following disease onset, but cease to occur after a period of time. We develop a dynamic Mover-Stayer model in which a canonical binary variable associated with each event indicates whether the underlying disease has resolved. An individual whose disease process has not resolved will experience events following a standard point process model governed by a latent intensity. When the disease process resolves, the complete data intensity becomes zero and no further event will occur. An expectation-maximization algorithm is described for parametric and semiparametric model fitting based on a discrete time dynamic Mover-Stayer model and a latent intensity-based model of the underlying point process.

Calcium antagonists as an add-on therapy for drug-resistant epilepsy

BACKGROUND

This is an updated version of the original Cochrane review published in The Cochrane Library 2001, Issue 4.Nearly a third of people with epilepsy do not have their seizures controlled with current treatments. Continuous attempts have been made to find new antiepileptic drugs based on increasing knowledge of the cellular and molecular biology involved in the genesis of epilepsy and seizures. Therefore, calcium antagonists that can alter the effects of calcium on brain cells have been investigated for their effect on epileptic seizures.

OBJECTIVES

To evaluate the effects of calcium antagonists when used as an add-on therapy for people with drug-resistant epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (29 January 2013), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 12), MEDLINE (1948 to 29 January 2013) and SCOPUS (all years to 29 January 2013).

SELECTION CRITERIA

Randomised placebo-controlled or active-controlled add-on trials of any calcium antagonist in people with drug-resistant epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors (MH and JP) independently selected trials for inclusion and extracted data. Outcomes investigated included 50% or greater reduction in seizure frequency, treatment withdrawal, adverse effects, cognition and quality of life. Analyses were by intention to treat.

MAIN RESULTS

Eleven trials were included with a total of 424 participants, one parallel-group and seven cross-over trials of flunarizine, two cross-over trials of nimodipine and one cross-over trial of nifedipine.For flunarizine, the risk ratio (RR) with 95% confidence interval (CI) for a 50% or greater reduction in seizure frequency in a single parallel trial was 1.53 (95% CI 0.59 to 3.96) indicating a non-significant advantage of flunarizine. We were unable to acquire data for this outcome from the other seven cross-over trials. The overall RR for treatment withdrawal of flunarizine was 7.11 (95% CI 1.73 to 29.30) indicating individuals were significantly more likely to have flunarizine withdrawn than placebo. No adverse effects were associated statistically with flunarizine.For nifedipine, we were unable to acquire the data we required for our specified outcomes.For nimodipine, we had data only from the first treatment period from one of the two cross-over trials (17 participants). The RR for a 50% or greater reduction in seizure frequency was 7.78 (99% CI 0.46 to 130.88) and for treatment withdrawal the RR was 2.25 (99% CI 0.25 to 20.38).

AUTHORS' CONCLUSIONS

Flunarizine may have a weak effect on seizure frequency but had a significant withdrawal rate, probably due to adverse effects, and should not be recommended for use as an add-on treatment. Similarly, there is no convincing evidence to support the use of nifedipine or nimodipine as add-on treatments for epilepsy.

The blood-brain barrier in migraine treatment

Salient aspects of the anatomy and function of the blood-barrier barrier (BBB) are reviewed in relation to migraine pathophysiology and treatment. The main function of the BBB is to limit the access of circulating substances to the neuropile. Smaller lipophilic substances have some access to the central nervous system by diffusion, whereas other substances can cross the BBB by carrier-mediated influx transport, receptor-mediated transcytosis and absorptive-mediated transcytosis. Studies of drugs relevant to migraine pathophysiology and treatment have been examined with the pressurized arteriography method. The drugs, given both luminally and abluminally, provide important notions regarding antimigraine site of action, probably abluminal to the BBB. The problems with the BBB in animal models designed to study the pathophysiology, acute treatment models and preventive treatments are discussed with special emphasize on the triptans and calcitonin gene-related peptide (CGRP). The human experimental headache model, especially the use of glycerol trinitrate (the nitric oxide model), and experiences with CGRP administrations utilize the systemic administration of the agonists with effects on other vascular beds also. We discuss how this can be related to genuine migraine attacks. Our view is that there exists no clear proof of breakdown or leakage of the BBB during migraine attacks, and that antimigraine drugs need to pass the BBB for efficacy.

Randomized exposure-controlled trials; impact of randomization and analysis strategies

AIMS

In the literature, five potential benefits of randomizing clinical trials on concentration levels, rather than dose, have been proposed: (i) statistical study power will increase; (ii) study power will be less sensitive to high variability in the pharmacokinetics (PK); (iii) the power of establishing an exposure-response relationship will be robust to correlations between PK and pharmacodynamics (PD); (iv) estimates of the exposure-response relationship are likely to be less biased; and (v) studies will provide a better control of exposure in situations with toxicity issues. The main aim of this study was to investigate if these five statements are valid when the trial results are evaluated using a model-based analysis.

METHODS

Quantitative relationships between drug dose, concentration, biomarker and clinical end-point were defined using pharmacometric models. Three randomization schemes for exposure-controlled trials, dose-controlled (RDCT), concentration-controlled (RCCT) and biomarker-controlled (RBCT), were simulated and analysed according to the models.

RESULTS

(i) The RCCT and RBCT had lower statistical power than RDCT in a model-based analysis; (ii) with a model-based analysis the power for an RDCT increased with increasing PK variability; (iii) the statistical power in a model-based analysis was robust to correlations between CL and EC(50) or E(max); (iv) under all conditions the bias was negligible (<3%); and (v) for studies with equal power RCCT could produce either more or fewer adverse events compared with an RDCT.

CONCLUSION

Alternative randomization schemes may not have the proposed advantages if a model-based analysis is employed.

Effects of flunarizine on spontaneous synaptic currents in rat neocortex

Flunarizine, a non-selective blocker of voltage-dependent Ca(2+) and Na(+) channels, is clinically effective against several neurological disorders, including epilepsy, migraine, and alternating hemiplegia of childhood. We examined the effects of flunarizine on spontaneous post-synaptic currents in acute brain slices maintained in vitro using patch-clamp electrophysiology. Flunarizine significantly attenuated the amplitude of spontaneous currents in pyramidal neurons from juvenile rat neocortex. Flunarizine had no effect on miniature spontaneous events recorded in the presence of tetrodotoxin, a blocker of voltage-dependent sodium channels. In high (9 mM) extracellular potassium, flunarizine reduced the amplitude and frequency of the spontaneous currents. Additionally, dimethyl sulfoxide, the solvent used in our experiments, reduced the amplitude of spontaneous currents, but only in high extracellular potassium. Our data suggest that the clinical activity of flunarizine may in part be a consequence of reducing spontaneous synaptic currents in the neocortex, especially under conditions of heightened neuronal activity.

Anticonvulsant profile of flunarizine and relation to Na(+) channel blocking effects

The present study will summarize our findings concerning the anticonvulsant properties of the Ca2+ channel blocker flunarizine in a variety of experimental models of epilepsy. Flunarizine exhibits anticonvulsant effects against tonic seizures induced by electroshock or various chemoconvulsants in mice, however, did not protect against pentylenetetrazol-induced clonic seizures. In the MES test, the efficacy of clinically established antiepileptics was increased by co-medication. In the rotarod test, a minimal "neurotoxic" dose (TD50) of 18.0 mg/kg intraperitoneally was determined. In models of complex partial seizures like the hippocampal stimulation and the amygdala kindling in rats, flunarizine showed only a moderate activity. Thus, it can be suggested that the anticonvulsant potency of flunarizine in various screening tests is lower than that of standard antiepileptics such as carbamazepine and phenytoin. Concerning the possible mode of action, whole-cell patch-clamp experiments with cultured neonatal rat cardiomyocytes showed that flunarizine depressed the fast inward Na+ current in a concentration- and frequency-dependent manner well comparable with the action of phenytoin. It is concluded that the use-dependent inhibition of voltage-dependent Na+ channels may essentially contribute to the anticonvulsant activity of flunarizine in models for generalized tonic-clonic seizures. The clinical efficacy as add-on therapy is critically discussed in view of the present data.

Measuring the efficacy of antiepileptic drugs

Clinical trials of new antiepileptic drugs (AEDs) include regulatory studies aimed at demonstrating efficacy and reasonable safety, post-marketing open-open label studies and longer term outcome studies. Regulatory trials involve a carefully selected population of patients and are conducted under rigorously standardised conditions. Data from such studies cannot often be translated into clinical practice. Pragmatic post-marketing studies using flexible dosing schedules allow clinicians to better judge the utility of the new drug in a wider population of patients with epilepsy and decide the most appropriate dosing schedules. This paper discusses some of the issues surrounding the measurement of efficacy of new AEDs in both pre- and post-marketing phases of their development. All of the newer AEDs are initially used in patients with refractory partial seizures as adjunctive treatment. These trials are generally parallel-group studies although cross-over designs have been employed. The use of placebo-control is uncontroversial in this type of study. Efficacy endpoints are generally manipulations of seizure frequency on study drug compared to control. Global outcome measures and health related quality of life scores can also be used to measure efficacy. As the standard AEDs are associated with a high rate of seizure remission in patients who receive them as monotherapy, demonstration of superior efficacy of a new agent in a comparative trial will require large numbers of patients in a design that takes into account the natural history of treated epilepsy. Comparing investigational agents to a standard AED in an 'active-control' study with demonstration of equivalent efficacy would seem to be an acceptable way of assessing efficacy of new AEDs in this population. Some regulators, however, do not accept equivalence as proof of efficacy and insist on demonstration of superiority compared to a control. The use of placebo alone in the control group is ethically dubious. Several innovative study designs have, therefore, been used to satisfy regulatory requirements, while maintaining patient safety including withdrawal to monotherapy using high versus low dose comparators. Observational outcome studies provide the best opportunity of exploring the long-term utility of individual AEDs. Such studies largely follow standard clinical practice and need considerable time and resources. They can, however, yield valuable information about the effectiveness of AEDs in everyday clinical practice. Data from regulatory trials should be complemented by postmarketing studies and longer term studies of outcome to help clinicians decide the best way of utilising new AEDs and establishing their role in the therapeutic armamentarium.

Selection effects in randomized trials with count data

Selection criteria are specified in clinical trials to define the study population from which the sample will be obtained. It is common for one of these criteria to be based on historical or baseline measurements of the clinical sign or symptom that will serve as the response variable in the trial. The effect of such selection criteria has been studied extensively for normally distributed responses, but less is known about the situation in which the response is a count or a possibly recurrent event. In this paper we examine the bias and relative efficiency of some common methods of analysis for count data in the presence of selection criteria. The investigation is carried out using asymptotic theory pertaining to misspecified models and by simulation. Applications involving data from an epilepsy trial and a study of transient myocardial ischaemia illustrate the effect of ignoring the selection mechanism.

Concentration-controlled or effect-controlled trials: useful alternatives to conventional dose-controlled trials?

Historically, dose-finding trials have been confirmatory in nature despite the fact that these trials represent an important and essential 'learning' phase in the drug development process. About 10 years ago 2 alternatives to the randomised dose-controlled trial (RDCT) were proposed as being more informative trial types. Controlling systemic drug exposure in order to improve efficiency of a trial forms the basis for the suggestion of a randomised concentration-controlled trial (RCCT). For the common instance where pharmacodynamic variability is larger than pharmacokinetic variability, the randomised effect-controlled trial (RECT), where patients are randomised to the effect of interest was suggested as even more informative. A survey of the literature shows that the RCCT has been sparsely applied and RECT not at all. For RCCT, the practical complications of carrying out the study seldom makes it the study type of choice. For RECT, the limited number of suitable situations for its application and the fact that the same effect is used for randomisation and analysis may explain the lack of applications. As a somewhat more favourable trial type, we suggest the randomised biomarker-controlled trial (RBCT), where patients are randomised to a certain value or range of a biomarker whereas the analysis is performed on another, clinically more relevant, effect. Although the RBCT has some attractive features, for example contributing to validation of a biomarker as a surrogate for clinical outcome, it is unlikely to be extensively used. Instead, the main shift from confirming to learning in dose-finding trials is coming from the incorporation of well-known learning components into the RDCT (e.g. sparse concentration measurements combined with population pharmacokinetic-pharmacodynamic, biomarker measurements and analysis of effect measures throughout the entire trial period).

Proof of efficacy trials: choosing the dose

It is apparent from current usage of antiepileptic drugs (AEDs) and from retrospective review of their drug development programmes, that the doses currently used in clinical practice differ from those which were used in clinical trials. This raises the question of how dose and titration schedules are selected in early development. An integral component of a drug development programme should be an assessment of dose response. The International Council on Harmonization of Technical Requirements for the Registration of Pharmaceuticals for Human Use [1994. Guidelines for industry: Dose-response information to support drug registration. ICH-E4. Federal Register] regulatory guidelines suggest that, at a minimum, three elements of dosing should be characterised: a maximum well tolerated dose, a minimum effective dose, and an appropriate rate of titration. Several specific designs can be utilised to assess dose response, which fall broadly into four categories, namely free titration, forced titration and dose escalation, parallel dose response, and dose reduction studies. In addition to these standard approaches, concentration-defined trials are an alternative in some circumstances and have been used with success in the development of newer AEDs. The designs chosen to address these elements are dependent upon the phase of development of the drug, and the severity of the disease, however, it is clear that conducting dose response studies earlier in the development programme may reduce the number of failed Phase 3 studies.

Calcium antagonists as an add-on therapy for drug-resistant epilepsy

BACKGROUND

As up to 30% of patients with epilepsy do not have their seizures controlled with current treatments, there have been continuous attempts to find new antiepileptic drugs based on increasing knowledge of cellular and molecular biology involved in the genesis of epilepsy and seizures. Calcium has been established to play a major role in seizure occurrence, thus, calcium antagonists that can alter the effects of calcium on brain cells have been investigated for effect on epileptic seizures.

OBJECTIVES

To evaluate the effects of calcium antagonists on seizures, side effects, quality of life and cognition, when used as an add-on therapy for patients with drug-resistant epilepsy.

SEARCH STRATEGY

We searched MEDLINE from 1966 to 2000 and the Cochrane Epilepsy Group trials register, the Cochrane Controlled Trials Register (The Cochrane Library Issue 1, 2001).

SELECTION CRITERIA

Randomized placebo-controlled add-on trials of any calcium antagonists in patients with drug-resistant epilepsy.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted data. Outcomes were: (a) 50% or greater reduction in seizure frequency; (b) treatment withdrawal (any reason); (c) side effects. For crossover trials, the first treatment period was treated as a parallel trial. Analyses were by intention to treat. Due to problems acquiring the data needed from crossover trials, overall results from these trials were summarised in tables.

MAIN RESULTS

Eleven trials were included. One parallel and seven crossover trials of flunarizine, two crossover trials of nimodipine and one crossover trial of nifedipine. For flunarizine, the odds ratio (OR) (95% Confidence Intervals (CIs)I) for a 50% or greater reduction in seizure frequency for the parallel trial was 1.64 (0.55, 4.94) indicating a non-significant advantage for flunarizine. We were unable to acquire data for this outcome from the seven crossover trials. The overall OR (95% CI) for treatment withdrawal for flunarizine was 5.83 (2.06, 16.45) indicating patients were significantly more likely to have flunarizine withdrawn than placebo. No side effects were statistically associated with flunarizine. For nifedipine we were unable to acquire the data we required from the two crossover trials for our specified outcomes. For the outcomes reported in the trials, nifedipine had no significant effect in seizures frequency. For nimodipine, we only had data from the first treatment period from one of the two crossover trials (17 subjects). The ORs (95% CIs) for a 50% or greater reduction in seizure frequency was 11.34 (1.00, 128.03) and for treatment withdrawal was 2.46 (0.22, 27.75).

REVIEWER'S CONCLUSIONS

Flunarizine may have a weak effect on seizure frequency, but had a significant withdrawal rate probably due to side effects, and should not be recommended for use as an add-on treatment. Similarly, there is no convincing evidence to support the use of nifedipine or nimodipine as add-on treatments for epilepsy.

The effects of verapamil and flunarizine on epileptiform activity induced by bicuculline and low Mg2+ in neocortical tissue of epileptic and primary non-epileptic patients

In human neocortical slices the specific L-type calcium channel blocker verapamil had been shown to be antiepileptic in the low Mg(2+)-model of epilepsy. The present investigation demonstrated: (1) verapamil exerted also an antiepileptic effect on epileptiform field potentials (EFP) induced by the GABAA-antagonist bicuculline. (2) The unspecific calcium channel modulator flunarizine, which in contrast to verapamil penetrates the blood-brain barrier, depressed EFP in the low Mg(2+)-model and in the bicuculline model. (3) There was no significant difference in the antiepileptic efficacy of verapamil and flunarizine in epileptic (epilepsy surgery) and primary non-epileptic (tumor surgery) neocortical slices.

Population pharmacodynamics: strategies for concentration-and effect-controlled clinical trials

OBJECTIVE

To explore and evaluate various strategies for drug concentration-and effect-controlled clinical trials, respectively, in the context of studies of population pharmacodynamics (concentration-effect relationships).

METHODS

The relative utility of drug concentration- and pharmacologic effect-controlled, randomized clinical trials with two or three concentration-effect measurements for each subject has been explored by computer simulation. The basis for these simulations was a sigmoid-Emax (maximum effect) pharmacodynamic model with Emax = 100%, EC50 (drug concentrations required to produce an effective intensity of 50%) = 10 concentration units, gamma = 2, and no hysteresis. Emax and gamma were held constant whereas EC50 was assumed to be log-normally distributed with a 26% coefficient of variation of the natural lognormalized data. A smaller random variability and variability due to measurement error also were incorporated in the simulations. To explore the implications of variable and unknown Emax and gamma values, the suitability of linear and log-linear interpolation procedures for two-point concentration-effect data in different regions of the sigmoid-Emax curve was compared.

RESULTS

Pharmacologic effect-controlled clinical trials with 300 hypothetical subjects and targeted effect intensities of 25% and 75% yielded very good estimates of drug concentrations required to produce effect intensities of 35%, 50%, and 65%, whereas concentration-controlled trials yielded much poorer estimates. Moreover, the concentration-controlled trials, despite optimum choice of targeted concentrations, yielded a large number of data points with poor information content (effect intensities of < 15% or > 85%). Determinations based on targeted effect intensities of 25% and 75% yielded better estimates of individual EC50 values than those targeted for 25% and 50% or 50% and 75% effect intensity. Results were not significantly improved by adding a third measurement (targeted to 50% effect) to the 25% and 75% effect design. Estimations of drug concentrations required to produce an effect intensity of 50%, based on log-linear interpolation of exact concentration-effect data at 25% and 75%, yielded exact results independent of gamma value (0.5-8.0) whereas linear interpolation produced large overestimates at gamma = 0.5 or 1.0 but satisfactory estimates at gamma > or = 2.0. Similar calculations for an effect intensity of 15% based on exact concentration-effect data at 5% and 25% yielded reasonably good estimates by both methods of interpolation over a wide range of gamma values. A review of the clinical literature showed that gamma values are usually 2 or higher.

CONCLUSIONS

Population pharmacodynamic studies of reversibly acting drugs without pharmacodynamic hysteresis or time dependency (e.g., tolerance) can be successfully conducted using a pharmacologic effect-controlled randomized clinical trial design with only two properly selected target effect intensities per subject.

Flunarizine of limited value in children with intractable epilepsy

Fourteen ambulatory children and adolescents with intractable epilepsy were studied in an open phase II study to investigate the pharmacokinetics and pharmacodynamics of flunarizine as an add-on treatment. Flunarizine was given in increasing doses starting with 0.1-0.3 mg/kg/day until effect was observed or a steady-state plasma concentration of 50-60 ng/ml was reached. Treatment was continued for 3 months at steady state. Pharmacokinetics were determined during the immediate posttreatment period. Positive antiepileptic effect (> or = 50% reduction in seizure frequency) was observed in 4 of 14 patients (29%; 95% CI: 52-5). Independently of antiepileptic effect, 10 of 14 parents (71.4%; 95% CI: 95-48) observed positive cognitive effects. In all patients treatment was withdrawn due to either lack of effect or weight gain. Flunarizine was rapidly absorbed; mean time of peak concentration (Tmax) was 2.7 hours (range: 1-8). The mean terminal half-life was 23.2 days (range: 7-48), the total plasma clearance of flunarizine per fraction of the dose absorbed (CLp/F) was 0.28 ml/min/kg (range: 0.07-042), and the volume of distribution of flunarizine per fraction of the dose absorbed (Vd/F) was 187 L/kg (range: 99-348). We conclude that flunarizine (0.1-0.3 mg/kg/day) seems to be of limited antiepileptic value in children with intractable epilepsy. The pharmacokinetic profile of flunarizine complicates its clinical use.