Standard approach to antiepileptic drug treatment in the United States

Identification of a G-Protein-Independent Activator of GIRK Channels

G-protein-gated inwardly rectifying K⁺ (GIRK) channels are essential effectors of inhibitory neurotransmission in the brain. GIRK channels have been implicated in diseases with abnormal neuronal excitability, including epilepsy and addiction. GIRK channels are tetramers composed of either the same subunit (e.g., homotetramers) or different subunits (e.g., heterotetramers). Compounds that specifically target subsets of GIRK channels in vivo are lacking. Previous studies have shown that alcohol directly activates GIRK channels through a hydrophobic pocket located in the cytoplasmic domain of the channel. Here, we report the identification and functional characterization of a GIRK1-selective activator, termed GiGA1, that targets the alcohol pocket. GiGA1 activates GIRK1/GIRK2 both in vitro and in vivo and, in turn, mitigates the effects of a convulsant in an acute epilepsy mouse model. These results shed light on the structure-based development of subunit-specific GIRK modulators that could provide potential treatments for brain disorders.

The Use of Psychotropic Medication for People with Severe Disabilities and Challenging Behavior: Current Status and Future Directions

People with severe disabilities who engage in challenging behavior are often prescribed psychotropic medication as a form of intervention. Although the goal of the medication is to reduce challenging behavior, limited empirical evidence is available to support the use of psychotropic intervention for people with severe disabilities. However, across a range of drug classes basic research suggests that many psychotropic medications selectively affect dimensions of behavior that could be of benefit in reducing challenging behavior. Currently, researchers cannot demonstrate whether most drugs prescribed to reduce challenging behavior are effective or predict when adverse side effects will emerge from their use. In this article we review the basic literature on behavioral pharmacology and integrate those findings with existing applied research to update JASH readers regarding the status of psychotropic medication. From this review, we present a set of suggestions that include: (a) improving research practices, (b) increasing the diversity of individuals involved in decision-making processes regarding medication use, and (c) developing consumer-friendly strategies for monitoring drug effects.

[Therapeutic Drug Monitoring of Valproic Acid in Children: A Prospective Study of The Effect of The Compliance and The Economic Level on the Trough Plasmatic Concentrations and Epileptic Seizures]

INTRODUCTION

Valproic acid (VA) is a widely used antiepileptic drug. Because of its pharmacokinetic variability and the influence of intrinsic and extrinsic factors such as the treatment compliance, VA therapeutic drug monitoring (TDM) is recommended in children. The aim of this study is to evaluate the effect of treatment compliance and the economic level on VA tough plasmatic concentration (TPC) and epileptic rhythm in children.

MATERIAL AND METHODS

A one-year prospective study (August 2008-August 2009) concerning children (age≤5 years) regularly treated by VA who had a VA TDM. So, 276 plasmatic samples from 238 children were collected. The children were divided in two groups as following: the group 1 (G1) presenting a good compliance and a reliable questioning and the group 2 (G2) presenting a bad compliance and a non reliable questioning. We evaluated the interindividual variability by correlating the TPC to the dose. Then, we divided the hole group in function of their economic levels (low-medium-high).

RESULTS

Sex ratio male/female was 1.3. Median age was 5 years+/-3,9. The mean TPC was 62 µg/mL [0.12-131 µg/mL]. VA TPC were in the therapeutic range (TR) in 62%. Adverse drug reactions were noted in 4.2% of the children. G1 represented 70% of the children and G2, 30%. The TPC were in the TR in 67% of G1 and 51% of G2 (p=0.02). There was a significant difference between the TPC in G1 and G2 (p=0.02).There was no significative difference in the TPC in function of the economic levels. There was no correlation between TPC and the administered doses. The epileptic seizures were more spaced in children with therapeutic TPC than those with TPC in the TR (p=0.002) and in G1 than in G2 (p=0.03).

CONCLUSIONS

Compliance should be appropriate in order to optimize the TDM rule. A good compliance and a therapeutic TPC allow a better control of epileptic seizures.

Antiepileptic drugs prescription utilization behavior and direct costs of treatment in a national hospital of India

Background and Objectives:

The present study evaluated the direct costs of active epilepsy and looked at the pattern of drug prescription and utilization in epileptic patients visiting the neuroscience centre of a national hospital of India.

Materials and Methods:

A total of 134 epileptic patients were studied over a period of 4 months. Patients demography, commonly prescribed antiepileptic drugs (AEDs), socioeconomic status, direct costs, response ratio (RR) for newer drugs, and quality of life (QOLIE-10) was evaluated.

Results and Discussion:

We found a higher percentage of male patients (67.9%) as compared with females. Most of the patients were in the age group 11–30 years and majority of them (39.6%) belonged to lower middle group. A higher percentage (68.7) of drugs was prescribed as polytherapy. Higher monthly cost was observed for some of the newer AEDs including the lamotrigine, levetiracetam, and lacosamide as compared with older drugs. Among the newer drugs, clobazam had the lowest cost. RR was calculated for 12 patients out of which 8 had a RR < –0.50. The QOL domains, following conventional or newer drugs, were not much affected.

Conclusion:

The study indicates an increasing trend toward clinical usage of newer AEDs, increasing trend of poly-therapy with significant escalations in the cost of therapy.

Depression symptoms as a function of duration of intractable or controlled epilepsy

We examined if depression symptoms in patients with intractable (IE) or controlled epilepsy (CE) differ and how long after onset of epilepsy these effects would be most pronounced. The NDDI-E was administered to all outpatients (n=358) seen in a comprehensive epilepsy program clinic over a two-year period. Patients who met inclusion criteria (n=223) completed a total of 431 NDDI-E surveys over this time. Patients with a diagnosis of IE (n=72) or CE (n=151) were compared as a function of time since their epilepsy onset, segmented into 10-year epochs. Depression symptoms were higher in patients with IE compared to CE at 10-<20 years and did not differ at other time points. This study reveals differences in depression symptoms as a function of duration of epilepsy. Attending to the dynamic nature of depression symptoms in different epochs of epilepsy may be an important treatment target in patients with epilepsy.

Treatment options for refractory and difficult to treat seizures: focus on vigabatrin

Complex partial seizures are often refractory to current pharmacological therapies. These difficult to treat seizures are typically managed using multiple antiepileptic drugs (AEDs). AEDs as a group are frequently associated with significant adverse drug effects, multiple drug interactions, and numerous potential clinical complications due to their individual pharmacokinetic profiles and unique drug properties. Recently, the approval of vigabatrin by the US Food and Drug Administration has necessitated that clinicians re-evaluate these risk-benefit relationships and determine where the drug fits within the treatment scheme for the management of complex partial seizures. This review will facilitate that re-evaluation through a brief review of AEDs used in the treatment of complex partial seizures, followed by a focused discussion on vigabatrin.

Monitoring gene changes during antiepileptic drug therapy to widen the safety window and reduce pharmacoresistance

A novel and potentially effective way to decrease pharmacoresistance is to widen an antiepileptic drug's (AED) safety window by altering its efficacy-toxicity relationship to reduce the frequency or eliminate the occurrence of drug-induced toxicities. The first step in this process is to identify specific AED toxicities that are common, objective, reliable to assess, and exhibit both interpatient and interdrug variability. Next, one or more of the fundamental sources of biological variability (e.g., DNA, RNA, proteins, or metabolites) is selected for study. By identifying a relationship between variations in these fundamental sources and specific AED toxicities, one aims to identify pathways underlying the genesis of the toxicity (mechanisms) or biomarkers related to elevated risk for AED toxicity (predictors). These types of studies have many methodological challenges. However, if properly conducted, the resulting data could be used to design interventions that directly block the toxicity mechanisms or preselect individuals who are at high risk of developing these toxicities. Both approaches would conceivably widen the safety window of efficacious AEDs and reduce the incidence of pharmacoresistance. This article describes a general framework for this approach and provides an example of the methodology using differential gene expression measured using RNA-based microarray technology in children experiencing VPA-associated weight gain.

Extended-release formulations in epilepsy

In the past years, the extended-release antiepileptic drug formulations have been developed and then approved for the treatment of many types of epilepsy. Among these extended-release formulations of antiepileptic drugs, the main drugs are valproic acid, carbamazepine, and phenytoin. This review analyzes the chemical and structural characteristics of the extended-release formulations of these 3 antiepileptic drugs, analyzing their bioequivalence and the studies about their clinical use. The results of these studies are encouraging and suggest a good tolerability and efficacy of these extended-release formulations, although larger studies are needed.

Analysis of antiepileptic drugs in biological fluids by means of electrokinetic chromatography

An overview of the electrokinetic chromatographic methods for the analysis of antiepileptic drug levels in biological samples is presented. In particular, micellar electrokinetic capillary chromatography is a very suitable method for the determination of these drugs, because it allows a rapid, selective, and accurate analysis. In addition to the electrokinetic chromatographic studies on the determination of antiepileptic drugs, some information regarding sample pretreatment will also be reported: this is a critical step when the analysis of biological fluids is concerned. The electrokinetic chromatographic methods for the determination of recent antiepileptic drugs (e.g., lamotrigine, levetiracetam) and classical anticonvulsants (e.g., carbamazepine, phenytoin, ethosuximide, valproic acid) will be discussed in depth, and their pharmacological profiles will be briefly described as well.

Extended-release formulations: simplifying strategies in the management of antiepileptic drug therapy

Advances in our understanding, diagnosis, and treatment of seizure disorders have transformed the management of epilepsy. As the number of antiepileptic drugs and their formulations increase, so do the expectations of therapy. Once limited to attaining complete control of seizures, epilepsy management now strives to enable patients to lead lifestyles consistent with their own capabilities. Extended-release antiepileptic drug formulations can help achieve the primary treatment goals for many patients with epilepsy: preventing occurrence of seizures and preventing or reducing side effects. The dosing flexibility and consistency of serum levels (without marked peak-to-trough fluctuations) conferred by extended-release formulations help achieve these goals. These same attributes of extended-release formulations may also improve compliance, quality of life, and patient satisfaction with treatment.

Therapeutics in pediatric epilepsy, Part 1: The new antiepileptic drugs and the ketogenic diet

Epilepsy is one of the most common and challenging neurologic disorders affecting children. Although various modalities exist to treat pediatric-onset seizures, seizures in 25% of children who are diagnosed as having epilepsy remain refractory to available therapies. Of the 8 new antiepileptic drugs (AEDs) (felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, and zonisamide), all but 2 (zonisamide and levetiracetam) have received Food and Drug Administration approval for adjunctive use in the pediatric population. However, most of the new AEDs used in adults have also been used in children, beyond the AEDs' approved indications. The ultimate goal of patient management is to choose the therapeutic option that provides the best chance of improving the patient's quality of life. Issues that relate to treatment choice include the likelihood of seizure recurrence, type and severity of seizures, available AED efficacies and toxicities, need for hematologic monitoring, ease of dosing, underlying medical conditions, medication interactions, urgency of initiating therapy, and cost. In this review, we discuss these issues for each of the 8 new AEDs; we also discuss the ketogenic diet and briefly review the older AEDs. Knowledge of the available AEDs will enable the practitioner to choose the best drug or drugs for individual patients.

Drug utilization pattern of anti-epileptic drugs: a pharmacoepidemiologic study in Oman

PURPOSE

To get an insight into the type and aetiology of epileptic seizures; to describe the drug utilization pattern of anti-epileptic drugs (AEDs) for the treatment of various forms of epileptic seizures in this tertiary referral centre in Oman; and to compare our drug utilization pattern with that from other countries. In addition, the tolerability of AEDs and the use of therapeutic drug monitoring (TDM) were evaluated.

METHODS

In a 6-month study, all epileptic patients aged 14 and above who were prescribed an AED were considered for analysis. Demographic data, type and aetiology of epileptic seizures, AED data, tests performed and adverse drug reaction (ADR) data were collected.

RESULTS

A total of 1039 prescriptions originated from 488 epileptic patients. The age ranged from 14 to 77 years (median, 24 years). Generalized tonic-clonic seizures (51%) of idiopathic/cryptogenic origin (83%) were the most common type and aetiology of epileptic seizures, respectively. An average of 1.34 AEDs per patient was prescribed with 78% of patients being on monotherapy. Sodium valproate (49%) was the most frequently prescribed AED, followed by carbamazepine (44%), phenytoin (12%) and lamotrigine (11%). Ten patients suffered an ADR and phenobarbital followed by carbamazepine were most commonly the subject of TDM.

CONCLUSIONS

Unlike the results in most other studies, generalized seizures represented the majority of epileptic seizures. The selection of the AEDs corresponded well with their known efficacy profiles for specific epileptic seizure types. Monotherapy was the type of therapy most frequently used, and sodium valproate and carbamazepine were the most commonly used AEDs.

Topiramate monotherapy for childhood absence seizures: an open label pilot study

This open-label, single-site, pilot study evaluated the therapeutic usefulness of topiramate in five children with typical absence seizures defined as loss of awareness associated with 3 Hz spike-wave activity on 24 hour ambulatory electroencephalogram (EEG). The children were previously untreated or treated unsuccessfully using other antiepileptic medication. Topiramate was initiated at a dose of 1 mg x kg (-1)day (-1), titrated twice weekly in 1 mg x kg (-1)day (-1)increments to 12 mg x kg (-1)day (-1)or individual maximally tolerated dose. Response was assessed after 6 weeks with ambulatory EEG monitoring and patient/parent record of seizure counts. All children completed the study. One previously untreated child became seizure-free on 5 mg x kg (-1)day(-1) topiramate, with no residual spike-wave activity at the final visit. In two patients, the frequency of seizures decreased in the early phases of titration, but rose to baseline levels as the topiramate dose was increased. With a reduction in dose to 6 mg x kg (-1)day (-1), seizure control improved, with substantial reductions in spike-wave activity. Seizure counts were not improved in the two remaining patients. Transient mood changes were noted in two patients. No child was withdrawn secondary to adverse effects. The results suggest that topiramate may be effective in childhood absence epilepsy. Controlled studies are now required to identify the clinically optimal dose.

A sensitive gas chromatographic/mass spectrometric method for the resolution and quantification of ethosuximide enantiomers in biological fluids

A modified specific, sensitive and reproducible chiral gas chromatographic (GC) method for the resolution and quantification of ethosuximide enantiomers in urine and plasma was developed. The samples were extracted by liquid-liquid extraction, using diethylether and the enantiomers were separated and quantified on a chiral gas chromatographic column (25QC2 / CYDEX- beta 0.25). The method involved the use of GC/MS instrumentation for the acquisition of data in the electron impact selective-ion monitoring mode, collecting ions characteristic of both ethosuximide and alpha, alpha - dimethyl - beta - methylsuccinimide, the internal standard and of mass-to-charge ratio (m/z) exactly equal to 55 and 70 units. The limit of quantitation of the method was 2.5 microg/ml for both urine and plasma with both enantiomers. The method proved to be linear, precise and reproducible in the 5-300 microg/ml concentration range for urine samples and in the 10-250 microg/ml concentration range for plasma samples. Future research work envisaged the application of this method in pharmacokinetic and pharmacodynamic studies.

The novel anticonvulsant BIA 2-093 inhibits transmitter release during opening of voltage-gated sodium channels: a comparison with carbamazepine and oxcarbazepine

(S)-(-)-10-acetoxy-10,11-dihydro-5H-dibenz/b,f/azepine-5-carboxamide (BIA 2-093) is endowed with high anticonvulsant activity and shares with carbamazepine (CBZ) and oxcarbazepine (OXC) the capability to inhibit voltage-gated sodium channels (VGSC). The present study was aimed to compare the effects of BIA 2-093, CBZ and OXC on the release of glutamate, aspartate, gamma-aminobutyric acid (GABA) and dopamine from striatal slices induced by the VGSC opener veratrine. The release of glutamate, aspartate, GABA and aspartate by veratrine from rat striatal slices was a concentration and time dependent process. All the three dibenzazepine carboxamide derivatives, BIA 2-093, CBZ and OXC inhibited in a concentration dependent manner (from 30 to 300 microM) the veratrine-induced release of glutamate, aspartate, GABA and dopamine. CBZ, OXC and BIA 2-093 were endowed with similar potencies in inhibiting veratrine-induced transmitter release. It is concluded that BIA 2-093, CBZ and OXC inhibit veratrine-induced transmitter release, which is in agreement with their capability to block VGSC. This property may be of importance for the anticonvulsant effects of BIA 2-093.

Oxcarbazepine in the treatment of epilepsy

Oxcarbazepine is a new antiepileptic drug (AED) that has been registered in more than 50 countries worldwide since 1990 and recently received approval in the United States and the European Union. Oxcarbazepine is a keto analog of carbamazepine and has a more favorable pharmacokinetic profile. It is rapidly absorbed after oral administration and undergoes rapid and almost complete reductive metabolism to form the pharmacologically active 10-monohydroxy derivative. Oxcarbazepine exhibits linear pharmacokinetics, no autoinduction, and minimal interaction with other AEDs. Ten controlled trials demonstrated that oxcarbazepine is safe and efficacious in the treatment of partial seizures across a wide range of ages (children to adults), situations (recent onset to treatment-resistant epilepsy), and uses (monotherapy and adjunctive therapy). The most common treatment-emergent adverse events are related to the central nervous system. Treatment-emergent hyponatremia (defined as serum sodium level < 125 mEq/L) occurred in 3% of patients treated with oxcarbazepine in clinical trials. According to the efficacy and safety profile established in the controlled trials, oxcarbazepine represents an important new treatment option indicated for monotherapy and adjunctive therapy in adults with partial seizures and as adjunctive therapy in children aged 4 years or older with partial seizures. Although structurally similar to carbamazepine, significant differences exist in the pharmacokinetics, drug interaction potential, adverse-effect profile, and dosage and titration between these two agents, and they should be considered distinct therapeutic agents.

Vagus nerve stimulation and the ketogenic diet

Antiepileptic drugs are the primary form of treatment for patients with epilepsy. In the United States, hundreds of thousands of people do not achieve seizure control, or have significant side effects, or both. Only a minority of patients with intractable epilepsy are candidates for traditional epilepsy surgery. Vagus nerve stimulation is now the second most common treatment for epilepsy in the United States. Additionally, the ketogenic diet has established itself as a valid treatment. This article discusses the history, mechanism of action, patient selection, efficacy, initiation, complications, and advantages of vagus nerve stimulation and the ketogenic diet.

Idiosyncratic reactions: new methods of identifying high-risk patients

This article describes the mechanisms of idiosyncratic drug reactions (IDRs) and provides an analysis of potential methods for identifying patients at high risk for antiepileptic idiosyncratic drug reactions. IDRs may be caused by toxic metabolites, either directly or indirectly (by way of an immunologic response or a free radical-mediated process). Four methods to potentially identify patients at high risk for AED IDRs are discussed: development of an "at-risk" clinical profile for a particular AED: identification of biomarkers that measure the formation of a toxic metabolite by a previously unrecognized bioactivation pathway for a particular AED; identification of biomarkers indicating deficient detoxification abilities [e.g., deficient free radical scavenging enzyme activities or low calculated oxidative protection (COP) ratios 1 and 2]; and identification of at-risk genetic markers. Clinical profiles for patients receiving valproic acid (VPA), felbamate (FBM), and lamotrigine (LTG) and who are at risk for development of AED IDRs are presented. Patients with VPA IDRs have deficient erythrocyte glutathione peroxidase activity, low plasma selenium concentrations, low COP1 ratios, and low COP2 ratios compared with age-matched controls. Patients with FBM-associated aplastic anemia have deficient erythrocyte glutathione peroxidase, superoxide dismutase (SOD), and glutathione reductase activities compared with age-matched controls. Use of at-risk clinical profiles (for VPA, FBM, and LTG) and measurement of erythrocyte glutathione peroxidase activity, erythrocyte SOD activity, and calculation of COP1 and COP2 ratios (for VPA and FBM) are inexpensive, simple methods of identifying high-risk patients for IDRs. Research is needed to further characterize the mechanism of IDRs, to investigate the clinical utility of free radical-scavenging enzyme activity measurement and calculation of COP ratios for other AED IDRs, and to develop additional methods of identifying patients at high risk for AED IDRs.

New antiepileptic drugs and preparations

Epilepsy affects 1.2% to 4.4% of the general population. Given the clinical profile of the newer antiepileptic agents, it is likely their usage will increase in the coming years, thus increasing the emergency physician's exposure to these medications and their side effects. Several of these side effects can have high morbidity, such as the aplastic anemia and hepatotoxicity caused by felbamate, and the Stevens-Johnson syndrome associated with lamotrigine. Overdoses of these medications also could increase, as will our knowledge of recognizing and managing them. The clinical spectrum of the newer medications is the treatment of partial seizures. None of the newer medications can be orally loaded nor are they available in an i.v. preparation. Serum drug levels are not available in most institutions and are not routinely measured in the ED. The new preparations of phenytoin, diazepam, and valporic acid add increased efficiency in drug administration, providing a new method for prehospital treatment of seizures and a more tolerable means of administration in the ED.

Acute behavioral and EEG effects of NW-1015 on electrically-induced afterdischarge in conscious monkeys

NW-1015 is a novel Na+ and Ca2+ channel blocker with broad spectrum anticonvulsant activity and an excellent safety margin. As the compound also shows sigma-1 receptor ligand properties it was deemed important to determine whether it possesses anticonvulsant properties in primates without causing behavioral and EEG abnormalities. Thus, the effects of NW-1015 on limbic electrically-induced afterdischarge (AD) were evaluated in four cynomolgus monkeys, and its activity compared to a single effective dose of phenytoin (PHT). The four male cynomolgus monkeys were chronically implanted for EEG recordings, from cortex and limbic structures. AD was induced in limbic areas by electrical stimulation. The effects of NW-1015 on the duration and the behavioral component of the AD were randomly tested at doses from 25 to 75 mg/kg and compared with the effects of PHT 50 mg/kg. Similarly to PHT, 50 mg/kg of NW-1015 significantly shortened the EEG AD and almost abolished AD elicited behavioral seizure. Only the behavioral effects of AD were reduced after administration of 25 mg/kg p.o. NW-1015 did not cause EEG or interictal behavioral alterations at doses up to 75 mg/kg p.o. These data further confirm the broad-spectrum anticonvulsant activity and a good safety profile of NW-1015 even in a primate model of complex partial seizures and suggest that its affinity for sigma-1 receptors is behaviorally irrelevant.

Validating a decision support system for anti-epileptic drug treatment. Part I: initiating anti-epileptic drug treatment

In this contribution the validation of a prototype decision support system that implements a model of expertise for initiating anti-epileptic drug treatment is described. Since domain experts were of the opinion that prescribing was a rather straightforward process we used only one expert neurologist for knowledge elicitation. To determine the correctness of the system we intended to compare the contents of the system's prescriptions with the majority decision of three neurologists. Because of a large variation in prescribing a majority decision could not be obtained in many cases. Even a Delphi procedure did not yield a majority decision in a large number of cases. Therefore a consensus meeting was organised to discuss cases where discrepancies remained. In the process the participating neurologists formulated prescription guidelines. These guidelines were used as a reference to determine the correctness of the prescriptions of both the system and of the neurologists. The acceptability of all prescriptions for each case was rated by the two neurologists who did not write a prescription for that case. From both comparisons it could be concluded that the system was at least as good in prescribing as individual neurologists.

Validating a decision support system for anti-epileptic drug treatment. Part II: adjusting anti-epileptic drug treatment

A model of expertise for monitoring antiepileptic drug treatment was implemented in a decision support system. We validated the advice of the system regarding treatment decisions at first follow-up with 265 paper cases based on patient records. The reference for comparison is based on the opinions of neurologists. We found considerable variation among the decisions of five neurologists. It could be shown that the system agreed with (groups of) neurologists at least as often as individual neurologists did. The correctness of the system was consistently higher than that of each of the neurologists, when the majority decision of the remaining neurologists constituted the standard.

Metabolism of carbamazepine by CYP3A6: a model for in vitro drug interactions studies

Carbamazepine (CBZ) is widely used in the treatment of epilepsy. The drug is principally metabolized by CYPs to 10, 11-epoxy carbamazepine (CBZ-E) but this metabolite more toxic than the parent drug, does possess anticonvulsant properties. In humans, CYP3A4, CYP2C8 and CYP1A2 have been shown to be implicated in CBZ biotransformation. Our purpose was to establish an experimental model to determine the interaction of CBZ with other antiepileptic drugs. We first identified the CYP isoforms that metabolized CBZ in rabbit. We used liver microsomes from rabbit treated with various compounds known to induce principally some CYPs subfamilies. Having tested all the compounds we demonstrated that only the animals treated with CYP3A inducers were able to metabolize CBZ strongly. The CBZ biotransformation was inhibited by anti CYP3A antibodies. All the CYP3A subfamily substrates specifically decrease CBZ-E formation. In our experiment we did not observe any inhibition with CYP2C substrate. These data provide evidence that in rabbit the CYP3A subfamily is primarily involved in CBZ metabolism. Using this model we investigated the interaction of CBZ with phenobarbital, phenytoin, ethosuccimide, primidone, progabide, vigabatrin and lamotrigine.

Profile of antiepileptic pharmacotherapy in a tertiary referral center in South India: a pharmacoepidemiologic and pharmacoeconomic study

PURPOSE

To study the current pharmacotherapy practices of epilepsy and its economics in a developing country by correlating the epidemiology and economics of antiepileptic drug (AED) treatment in general epilepsy care and comprehensive epilepsy care.

METHODS

We compared the AED-use profiles, efficacy, and tolerability at entry and at last follow-up for 972 patients seen at a comprehensive epilepsy care program in South India from 1993 to 1995. The relative cost was expressed as the average percentage of the per capita gross national product (GNP/capita) each individual spent for AED treatment.

RESULTS

At entry, 562 (57.8%) subjects were receiving polytherapy; at last follow-up, 743 (76.4%) patients were receiving monotherapy, an increase of 34.3% in the use of monotherapy. One or more adverse drug reactions were reported by 28.6% of patients at entry and by 19.8% at last follow-up. The proportion of patients who were seizure free increased from 29.0 to 44.8%. Carbamazepine (CBZ) was the most frequently used AED, followed by diphenylhydantoin (DPH), valproate (VPA), and phenobarbitone (PB). The relative cost (% GNP/capita) for standard AEDs were as follows: PB, 4.4%; DPH, 7.1%; CBZ, 16.8%; and VPA, 29.5%. The average annual cost of AED treatment per patient in U.S. dollars was $64.32 at entry and $47.73 at last follow-up. Reduction in polytherapy resulted in the net annual saving of $16,128 ($16.59 per patient, or 5.4% GNP/capita).

CONCLUSIONS

The more frequent use of relatively expensive drugs like CBZ and VPA and the use of polytherapy-still quite prevalent in developing countries-has escalated the cost of AED therapy. Although in recent years AEDs have become more available in developing regions, primary and secondary care physicians have not been adequately educated about the current trends in the pharmacotherapy of epilepsy.

Induction of hepatic CYP2B in foetal and neonatal rats after maternal administration of phenobarbital

We examined hepatic cytochrome P450 (CYP) induction in rat foetuses and neonates by phenobarbital administered through placenta or breast feeding. In an intraperitoneal study, phenobarbital was administered intraperitoneally to mother rats once a day for 7 consecutive days before delivery. The livers were removed from foetuses, neonates, and mothers just before and 5 and 10 days after delivery. In oral administration study, water containing phenobarbital was given orally ad libitum from day 13 of pregnancy to 3 weeks after delivery (end of lactation). The livers were removed from neonates and mothers just before and one week after delactation. Phenobarbital administered intraperitoneally increased both the activity and the protein expression of CYP2B in 5-day-old neonates, even though the administration ended before delivery. This increase had disappeared in 10-day-old neonates. In mother rats, phenobarbital increased CYP2B just before and 5 days after delivery, while no increase was detected 10 days after delivery. Phenobarbital administered orally also increased both the activity and the protein expression of CYP2B of neonates and mothers during lactation and this increase also disappeared 1 week after delactation. Neither activity nor protein expression of CYP3A were induced in perinates at any age examined in either administration route. In mother rats, increase in CYP3A was found only just before delivery in the peritoneal administration study. Our results suggest that phenobarbital administered through placenta or breast milk transiently induces hepatic CYP2B in newborn rats but that the influence of phenobarbital does not last long.

Therapeutic strategies against epilepsy in Mediterranean countries: a report from an international collaborative survey

A collaborative survey was performed to compare prescribing strategies for the treatment of epilepsy in Mediterranean countries, based on analysis of 500 questionnaires compiled by physicians in 14 different countries. For partial seizures, carbamazepine was the drug of choice in most countries, whereas the second choice of drug differed widely. For primarily generalized tonic-clonic seizures, valproic acid was usually preferred, but other drugs used widely in some countries included phenobarbital, phenytoin and carbamazepine. Lamotrigine was the most popular second-line drug for primarily generalized tonic-clonic seizures in the European countries. In patients where the initial drug failed, switching to an alternative monotherapy was usually the preferred strategy, but advocates of early use of combination therapy exceeded 30% in the respondents of seven countries. Most respondents, in all countries except Turkey, did not prescribe drugs to prevent recurrence of febrile seizures; however, intermittent prophylaxis with a benzodiazepine was advocated by a considerable number of physicians, and continuous prophylaxis was prescribed by a significant minority of respondents in France, Syria and Tunisia. New drugs were rarely used as first-line treatment due to high cost and inadequate experience. Overall, this survey indicates that there is a wide variability in therapeutic practices between and within countries. This information may be useful for the implementation of national educational activities and for the design of pragmatic trials aimed at comparing different therapeutic strategies.

Aggravation of generalized epilepsies

Generalized epilepsies are treatable with a number of antiepileptic drugs (AEDs) that are effective in different seizure types and epilepsy syndromes. The mechanisms of action of these AEDs are incompletely understood but include inhibition of low-threshold calcium currents and of voltage-gated sodium channels and facilitation of GABA(A) receptor currents. The mechanisms of aggravation are also unknown but could include elevation of brain GABA, blockade of voltage-gated sodium channels, and idiosyncratic toxicity reactions. Anecdotal reports suggest that aggravation of generalized epilepsy can occur with virtually all AEDs. The best-documented examples are aggravation of absences by carbamazepine and aggravation of symptomatic generalized epilepsies by vigabatrin. Therefore, the physician must be constantly aware of the problem of aggravation of seizures by AEDs. With careful diagnosis of the epileptic syndrome and an awareness of the problem, aggravation of seizures can be minimized.

Standards of laboratory practice: antiepileptic drug monitoring

Discussion and development of standards for appropriate monitoring led to the following key recommendations for ordering, sampling, and analyzing antiepileptic drugs: Monitoring should usually be done on trough specimens after steady-state has been reached and always with an appropriate medical indication; non-steady-state concentrations may be indicated in selected situations. Monitoring of free phenytoin and free valproic acid is indicated in specific situations and should be done in serum. The metabolite of primidone, phenobarbital, should be measured concurrently with parent drug, but the active metabolite of carbamazepine does not need to be monitored unless the patient is exhibiting an unusual toxic response that cannot be otherwise explained. Assays used for antiepileptic drug monitoring should display a long-term CV of &lt;10% and preferably &lt;5%. Subtherapeutic and supratherapeutic drug concentrations should be investigated on a regular basis as part of a quality assurance process.

Biochemical basis of sodium valproate hepatotoxicity and renal tubular disorder: time dependence of peroxidative injury

Mice fed with sodium valproate for 7, 14 and 21 days were evaluated for hepatotoxicity and renal tubular disorder. The drug was administered as an aqueous solution with an increasing concentration up to five days gradually reaching up to 0.71% w/v, which persisted throughout the study period. Mice fed with sodium valproate for 7, 14 and 21 days showed, marked hepatic injury and renal tubular disorder, evidenced by increased levels of malondialdehyde as a measure of lipid peroxidation. Administration of sodium valproate affected the glutathione contents both in liver and kidney tissue at all the three time points. However, this reduction in glutathione concentration was more pronounced in kidney when compared to control group. These results support the hypothesis that lipid peroxidation mediates the effect of sodium valproate on liver and kidney. Furthermore, the valproate induced toxicity is time related and the increase in lipid peroxide levels and depletion of glutathione occur time dependent even if the dose is clinically appropriate.

Overview of the safety of newer antiepileptic drugs

Standard antiepileptic drugs (AEDs) are associated with a wide variety of acute and chronic adverse events and with many interactions with each other and with non-AEDs that complicate patient management. The safety and interaction profiles of the newer AEDs have also been intensively studied. Safety data are available for six of the newer AEDs, lamotrigine (LTG), vigabatrin (VGB), gabapentin (GBP), tiagabine (TGB), felbamate (FBM), and topiramate (TPM). The potential for the most recently developed AEDs for producing rare idiosyncratic reactions cannot be ascertained until additional patient exposures have been reported from careful postmarketing surveillance.

Anticonvulsant drug effects on spontaneous thalamocortical rhythms in vitro: phenytoin, carbamazepine, and phenobarbital

When perfused with a medium containing no added Mg2+, rodent thalamocortical brain slices generate spontaneous generalized thalamocortical discharges of several types. Two of these discharges, termed simple and complex thalamocortical burst complexes (sTBCs and cTBCs), are physiologically and pharmacologically similar to the spike-wave discharges of generalized absence epilepsy and to the discharges underlying generalized tonic-clonic seizures, respectively. In a further characterization of the pharmacology of generalized thalamocortical discharges recorded in rodent thalamocortical slices, the actions of anticonvulsants effective in control of partial and generalized tonic-clonic seizures, but not generalized absence seizures, were studied on these rhythms. The effects of phenytoin, carbamazepine, and phenobarbital were tested against sTBCs and cTBCs recorded in vitro in rodent thalamocortical slices. When applied in clinically relevant concentrations, phenytoin and carbamazepine were very effective in reducing or blocking cTBCs. These drugs were much less effective in controlling sTBCs. Phenobarbital was effective in controlling both sTBCs and cTBCs, but the level of block was greater for cTBCs. Therefore, it appears that sTBCs and cTBCs are quite distinct in their relative sensitivity to anticonvulsant drugs, and this differential sensitivity parallels the relative effectiveness of these drugs in controlling generalized absence and generalized tonic-clonic seizures.

Anticonvulsant drug effects on spontaneous thalamocortical rhythms in vitro: ethosuximide, trimethadione, and dimethadione

Spontaneous generalized epileptiform discharges were elicited in rodent thalamocortical slices by perfusion with a medium containing no added Mg2+. In multiple-channel extracellular field potential recordings in thalamus and cortex, several distinct types of discharges were recorded, with two principal variants bearing marked similarity to spike-wave and generalized tonic-clonic seizure discharges recorded in patients with generalized seizure disorders. These discharges were termed sTBCs and cTBCs, respectively, for simple and complex thalamocortical burst complexes. The sensitivity of these discharges to the generalized absence anticonvulsants ethosuximide, trimethadione and dimethadione (the active metabolite of trimethadione) was studied. sTBCs were reduced or blocked by ethosuximide and dimethadione, when these drugs were applied in clinically relevant concentrations. The order of effectiveness of these agents was dimethadione > or = ethosuximide >> trimethadione. This paralleled the relative efficacy of these drugs in blocking T current in thalamic neurons. cTBCs were unaffected or exacerbated by these drugs. Structural control drugs including succinimide, the behaviorally inactive ring base of ethosuximide, and alpha, alpha-dimethyl-beta-methylsuccinimide, a convulsant succinimide, were inactive or exacerbated either sTBCs or cTBCs, respectively. These spontaneous generalized thalamocortical discharges in rodent thalamocortical slices may represent a potentially valuable in vitro model of generalized seizure discharges, with marked pharmacological and physiological similarities to various forms of clinical epileptic seizure activity.

Anticonvulsant drug effects on spontaneous thalamocortical rhythms in vitro: valproic acid, clonazepam, and alpha-methyl-alpha-phenylsuccinimide

Spontaneous thalamocortical epileptiform activity was elicited in rodent thalamocortical slices by a medium containing no added Mg2+. Multiple varieties of activity were generated in these slices, including simple thalamocortical burst complex (sTBC) activity that resembled the spike-wave discharges of generalized absence epilepsy, and complex thalamocortical burst complex (cTBC) activity that resembled generalized tonic-clonic seizure discharges. In a further pharmacological characterization of this activity, the effects of the broad-spectrum anticonvulsants valproic acid, alpha-methyl-alpha-phenylsuccinimide (the active metabolite of methsuximide) and clonazepam were studied. All three drugs were found to be effective in controlling both sTBC and cTBC activity when applied in clinically relevant concentration ranges. The effectiveness of valproic acid against spontaneous rhythms in vitro was not due to augmentation of GABAergic inhibition. No effect of valproic acid on GABA-activated chloride currents was evident in patch-clamp recordings of acutely isolated thalamic or cortical neurons. The equivalent general clinical and experimental spectrum of action of broadly effective anticonvulsants provided an additional correlation between the clinical efficacy of anticonvulsant drugs and their effects against epileptiform discharges in rodent thalamocortical slices. This further validates spontaneous generalized low-Mg2+ thalamocortical activity as a potentially valuable in vitro model of the primary generalized epilepsies, in which the cellular mechanisms underlying generation and control of these seizure discharges can be studied.

Lamotrigine-induced rash in children

Of 68 children treated with lamotrigine, a new antiepileptic medication, five developed a rash. One child developed Stevens-Johnson syndrome on lamotrigine monotherapy. Of the five patients with the rash, three were admitted to the hospital (two to the intensive care unit). All recovered completely, but one child had a recurrence of the rash within 30 minutes of reexposure to lamotrigine after 6 months.

The management of epilepsy in the 1990s. Acquisitions, uncertainties and priorities for future research

The pharmacological treatment of epilepsy has made considerable progress during the last decade, due to improved knowledge of the clinical pharmacology of individual drugs, acquisition of new information on the factors affecting response and need for drug treatment, and development of promising new agents. Once a clinical diagnosis of epilepsy has been made (which generally requires the occurrence of more than one seizure), treatment should be started with a single drug selected on the basis of seizure type and tolerability profile. Although there are important regional differences in prescribing patterns and individual circumstances may dictate alternative choices, carbamazepine is generally regarded as the preferred treatment for partial seizures (with or without secondary generalisation) while valproic acid (sodium valproate) is usually the first choice in most forms of generalised epilepsies. To achieve therapeutic success, the daily dosage must be tailored to meet individual needs, and there is suggestive evidence that in some patients the dosage prescribed initially may be unnecessarily large. Plasma antiepileptic drug concentrations may aid in the individualization of dosage, but should not be regarded as a substitute for careful monitoring of clinical response. Although overall about 70% of patients can be completely controlled, response rate is influenced by a number of factors, the most important of which are seizure type and syndromic form. The importance of a correct syndromic classification for rational drug selection has been poorly assessed and represents a major area for future research. Patients who do not respond to the highest tolerated dose of the initially prescribed drug may be switched to monotherapy with an alternative agent or may be given add-on treatment with a second drug. Appropriate prospective trials are required to assess the merits of either strategy. If add-on therapy is selected and the patient becomes seizure free, it may be possible to discontinue the drug prescribed initially and reinstitute monotherapy. Only a minority of patients are likely to require multiple drug therapy, and it remains to be established whether specific drug combinations are more effective than others. Until further information becomes available, the new agents should be reserved for patients failing to respond to the conventional treatments of first choice. Patients whose seizures cannot be controlled by available drugs should be reassessed, and polytherapy should be maintained only when there is clear evidence that benefits outweigh possible adverse effects. In many patients who have been seizure free for at least 2 years it may be possible to gradually discontinue all medications.(ABSTRACT TRUNCATED AT 400 WORDS)