The relationship of depression to antiepileptic drug adherence and quality of life in epilepsy

We sought to examine the impact of depression upon antiepileptic drug (AED) adherence in patients with epilepsy. We administered the Center for Epidemiologic Studies Depression Scale (CES-D), Neurological Disorders Depression Inventory for Epilepsy (NDDI-E), Seizure Severity Questionnaire (SSQ), and Quality of Life in Epilepsy-10 (QOLIE-10) and measured AED adherence by utilizing the medication possession ratio (MPR) in adult patients with epilepsy identified through a pharmacy claims database. From a sampling frame of over 10,000 patients identified in claims, 2750 were randomly selected and contacted directly by mail to participate in the cross-sectional survey. A total of 465 eligible patients completed a survey. Survey data were combined with administrative claims data for analysis. We conducted a path analysis to assess the relationships between depression, adherence, seizure severity, and quality of life (QOL). Patients with depression scored significantly worse on measures of seizure severity (p = .003), QOL (p < .001), and adherence (p = .001). On path analysis, depression and QOL and seizure severity and QOL were related, but only the NDDI-E scores had a significant relationship with medication adherence (p = .001). Depression as measured by the NDDI-E was correlated with an increased risk of AED nonadherence. Depression or seizure severity adversely impacted QOL. These results demonstrate yet another important reason to screen for depression in epilepsy.     

难治性癫痫患者脑组织中耐药蛋白表达与卡马西平浓度的相关性

目的 通过对难治性癫痫患者脑组织中P-糖蛋白、肺耐药相关蛋白表达与卡马西平浓度的比较及相关性研究,探讨难治性癫痫耐药的机制.方法 选取2007年至2009年间于宣武医院功能神经外科行癫痫致痫灶切除术治疗且术前服用卡马西平半年以上的26例药物难治性癫痫患者的脑组织标本(其中局灶性皮质发育不良ⅠblO例、Ⅱa4例、Ⅱb2例,神经节细胞胶质瘤6例,胚胎发育不良性神经上皮瘤4例).应用Envision二步法进行免疫组织化学标记,观察两种耐药蛋白在脑组织中的表达部位和表达强度.应用Western blot法进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳,对两种耐药蛋白在脑组织病灶区域和病灶周围区域的表达分别进行定量分析.应用荧光偏振免疫分析法对病灶区域和病灶周围区域的卡马西平浓度进行测定.结果 P-糖蛋白在局灶性皮质发育不良Ⅱ型和难治性癫痫相关脑肿瘤病例的病灶区域表达(μg/ml)均高于病灶周围区域(分别是2.593±0.829和1.711±0.292,t=-2.201,P=0.028;1.352±0.445和1.179±0.593,t=2.698,P=0.028).肺耐药相关蛋白在局灶性皮质发育不良Ⅱ型和难治性癫痫相关脑肿瘤病例的病灶区域表达(μg/ml)亦均高于病灶周围区域(分别是1.567±0.092和0.775±0.101,t=-2.516,P=0.024;1.091±0.239和0.825±0.297,t =3.997,P=0.003).卡马西平在难治性癫痫相关脑肿瘤病灶区域平均浓度(μg/ml)低于病灶周围区域(0.848±0.726和0.948±0.785,t=-3.056,P=0.014),在病灶区域卡马西平浓度低于病灶周围区域的8例中,病灶区域P-糖蛋白和肺耐药相关蛋白同时升高.但是P-糖蛋白、肺耐药相关蛋白表达量与难治性癫痫患者脑组织卡马西平浓度无显著的等级相关性.结论 耐药蛋白参与了难治性癫痫耐药的过程,同时提示癫痫的耐药是一个复杂的过程,不同病变可能有不同的机制参与了耐药过程.     

Pharmacokinetic interaction study between the new antiepileptic and CNS drug RWJ-333369 and carbamazepine in healthy adults

PURPOSE: To characterize the possible pharmacokinetic interaction between the new antiepileptic and CNS drug RWJ-333369 and carbamazepine (CBZ) following multiple dosing in healthy subjects. METHODS: In an 8-week, open-label, sequential design study, 24 healthy adults received multiple-dose RWJ-333369 alone (5 days 250 mg q12h; 5 days 500 mg q12h), then after a 4-day washout, multiple-dose CBZ alone (3 days 100 mg q12h; 3 days 200 mg q12h; 22 days 300 mg q12h), and then combination of CBZ (300 mg q12h), and RWJ-333369 (5 days 250 mg q12h; 5 days 500 mg q12h). RESULTS: At steady-state following multiple dosing, RWJ-333369 peak plasma concentration (C(max)) and area under the concentration-time-curve within the dosing interval (AUCss) increased in proportion to dose. The C(max) and AUCss of CBZ were similar when given alone or concomitantly with RWJ-333369. The 90% confidence intervals for the ratio of CBZ C(max) and AUCss with/without RWJ-333369 were: 94-104% and 95-104%, respectively (well within the equivalence range of 80-125%). When RWJ-333369 was administered with CBZ, its mean (SD) oral clearance increased from 3.2 L/h to 4.9 L/h and consequently its mean half-life was shortened from 10.4 (1.9) h to 7.4 (1.2) h, and mean AUCss and C(max) were reduced by 37% and 30%, respectively. CONCLUSIONS: There was no effect of multiple-dose RWJ-333369 on CBZ pharmacokinetics. CBZ induced RWJ-333369 clearance, resulting in shortened half-life and decreased exposure (AUCss) and C(max). Concomitant administration of RWJ-333369 with CBZ was generally safe and tolerated.     

An interaction study between the new antiepileptic and CNS drug carisbamate (RWJ-333369) and lamotrigine and valproic acid

PURPOSE: To characterize possible pharmacokinetic interactions between the new antiepileptic drug carisbamate (RWJ-333369) and valproic acid (VPA) or lamotrigine (LTG) following multiple dosing in healthy subjects. METHODS: Two open-label, sequential-design studies were conducted in 24 healthy adults. In Study 1, subjects received carisbamate alone (5 days 250 mg q12h; 5 days 500 mg q12h), then VPA alone (7 days 300 mg q12h; 7 days 500 mg q12h), and then a combination of VPA (500 mg q12h) and carisbamate (5 days 250 mg q12h; 5 days 500 mg q12h). In Study 2, subjects received carisbamate alone as in Study 1, then LTG alone (14 days 25 mg q12h; 14 days 50 mg q12h), and then combination of LTG (50 mg q12h) and carisbamate (3 days 250 mg q12h; 14 days 500 mg q12h). RESULTS: Coadministration of VPA or LTG had minimal effect on carisbamate mean C(max) and AUC(ss) values. Mean VPA-C(max) and AUC(ss) values were approximately 15% lower when given concomitantly with carisbamate. However, the 90% confidence intervals (CIs) for the C(max) and AUC(ss) ratio with/without carisbamate were within the 80-125% equivalence range, C(max) 82-89%; AUC(ss) 81-88%. Mean LTG C(max) and AUC(ss) values were approximately 20% lower when given concomitantly with carisbamate. The 90% CIs with and without carisbamate for LTG C(max) and AUC(ss) were 79-86% and 75-81%, respectively. This modest change is not considered clinically significant. CONCLUSIONS: There were no clinically significant interactions between carisbamate and VPA or LTG. Concomitant administration of carisbamate with VPA or LTG was generally safe and well tolerated.     

Evaluation of the relationship between C677T variants of methylenetetrahydrofolate reductase gene and hyperhomocysteinemia in children receiving antiepileptic drug therapy

Homocysteine (Hcy) is a sulfur-containing amino acid involved in methionine metabolism. Elevated plasma Hcy concentration is a possible risk factor for vascular disease. Folate and vitamin B-12 are vitamins that are necessary for remethylization of Hcy to methionine. The methylenetetrahydrofolate reductase (MTHFR) is the key enzyme in remethylation of Hcy to methionine and supplies the required 5-methyltetrahydrofolate as the methyl donor for this reaction. It is well known that some antiepileptic drugs (AED) can lead to hyperhomocysteinemia by affecting the levels of folate and vitamin B-12. The C677T variant of MTHFR gene can also lead to hyperhomocysteinemia particularly when serum folate level is decreased. In this study, we investigated the levels of serum folate, vitamin B-12 and Hcy in epileptic patients receiving carbamazepine (CBZ) or valproic acid (VPA) as monotherapy, and we also evaluated the probable contribution of the C677T variant of MTHFR gene in hyperhomocysteinemia. A total of 93 patients with idiopathic epilepsy receiving CBZ or VPA as monotherapy were included in this study. CBZ and VPA groups consisted of 29 and 64 patients, respectively. The control group comprised 62 healthy children. We measured serum folate, vitamin B-12 and Hcy levels in each group. We found that mean serum folate level was statistically lower and mean Hcy level was higher in epileptic patients receiving CBZ or VPA when compared with those of controls'. We also determined the C677T variants of MTHFR gene (as normal, heterozygote or homozygote) in epileptic patients. We compared the variant groups for serum folate, vitamin B-12 and Hcy levels and found no significant differences among them. In conclusion, C677T variants of MTHFR gene have no contribution in hyperhomocysteinemia in epileptic patients receiving CBZ or VPA.     

Assessing risk to benefit ratio in antiepileptic drug therapy

Assessment of risk to benefit ratio in patients with epilepsy is crucial in determining the need for treatment, the choice of drugs and the use of monitoring tools such as laboratory tests and other investigations. Active epilepsy per se carries significant risks in terms of increased mortality, susceptibility to psychopathology and physical injury, and reduced quality of life as a result of restricted lifestyle, stigma and prejudice. By preventing the occurrence of seizures, antiepileptic drugs (AEDs) attenuate or eliminate altogether seizure-related risks, but other risks may arise due to the side effects of the drugs, all of which have a relatively narrow therapeutic index. While there are no major differences in the degree of efficacy between AEDs which are effective in any given seizure type, side effect profiles differ considerably from one agent to another and represent a major factor in determining choice of treatment. Assessment of risk to benefit ratio should also take into consideration patient-specific factors such as type and severity of the epilepsy, age, sex, childbearing potential, medical and drug history, associated disease, use of concomitant medication (including the contraceptive pill) and the prospected patient's compliance. In some benign epilepsy syndromes, such as idiopathic partial epilepsy with centro-temporal spikes, the risk of side effects from AEDs may outweigh potential benefits in terms of seizure control, and treatment is generally not indicated. At the opposite end of the spectrum, the serious morbidity and mortality associated with severe epileptic encephalopathies, such as the Lennox-Gastaut syndrome, justifies aggressive treatment even with drugs associated with a relatively high risk of life threatening side effects such as felbamate. The present article will provide an overview of specific risks associated with epilepsy and with the various drugs used for its treatment, and will attempt to evaluate the complex balance between these risks and therapeutic benefits in different categories of patients.     

Association between antiepileptic drug dose and long-term response in patients with refractory epilepsy

Seizures in patients with medically refractory epilepsy remain a substantial clinical challenge, not least because of the dearth of evidence-based guidelines as to which antiepileptic drug (AED) regimens are the most effective, and what doses of these drugs to employ. We sought to determine whether there were regions in the dosage range of commonly used AEDs that were associated with superior efficacy in patients with refractory epilepsy. We retrospectively analyzed treatment records from 164 institutionalized, developmentally disabled patients with refractory epilepsy, averaging 17 years of followup per patient. We determined the change in seizure frequency in within-patient comparisons during treatment with the most commonly used combinations of 12 AEDs, and then analyzed the response to treatment by quartile of the dose range for monotherapy with carbamazepine (CBZ), lamotrigine (LTG), valproate (VPA), or phenytoin (PHT), and the combination LTG/VPA. We found that of the 26 most frequently used AED regimens, only LTG/VPA yielded superior efficacy, similar to an earlier study. For the monotherapies, patients who were treated in the lowest quartile of the dose range had significantly better long-term reduction in seizure frequency compared to those treated in the 2nd and 3rd quartiles of the dose range. Patients with paired exposures to CBZ in both the lowest quartile and a higher quartile of dose range experienced an increase in seizure frequency at higher doses, while patients treated with LTG/VPA showed improved response with escalation of LTG dosage. We conclude that in this population of patients with refractory epilepsy, LTG/VPA was the most effective AED combination. The best response to AEDs used in monotherapy was observed at low dosage. This suggests that routine exposure to maximally tolerated AED doses may not be necessary to identify those patients with drug-resistant seizures who will have a beneficial response to therapy. Rather, responders to a given AED regimen may be identified with exposure to low AED doses, with careful evaluation of the response to subsequent titration to identify non-responders or those with exacerbation of seizure frequency at higher doses.     

Mechanisms of antiepileptic drug resistance

PURPOSE OF REVIEW: The present review considers new developments in the study and our understanding of resistance to treatment with antiepileptic drugs in epilepsy. RECENT FINDINGS: Studies suggest that mechanisms of resistance to drug treatment that operate in other diseases may also be relevant in human and animal drug-resistant epilepsy. Immunohistochemical and molecular genetic data show that there is overexpression of a number of genes and proteins that mediate nonspecific resistance to drug treatment. In particular, there is upregulation of P-glycoprotein and multidrug resistance-associated proteins 1 and 2. These proteins appear to be expressed in cerebral parenchymal cell populations that do not normally do so. Work in animal models suggests that these proteins are able to reduce the local concentration of antiepileptic drugs. Although these proteins are therefore good candidates for mediators of drug resistance, there is still limited proof that they are functionally important in human drug-resistant epilepsy. SUMMARY: Careful attention needs to be given to the identification and confirmation of the practical importance of mechanisms postulated to underlie drug resistance in human epilepsy. If certain mechanisms are shown to be involved, then new therapeutic options for drug-resistant human epilepsy may be forthcoming.     

Mechanisms of antiepileptic drug action

Animal seizure models, in vitro preparations of cell cultures and tissue slices, and an unravelling of some of the basic mechanisms underlying epileptogenesis and epilepsy have furthered the understanding of mechanisms of action of antiepileptic drugs at the cellular and subcellular levels. Nevertheless, the mechanism of action of most antiepileptic drugs in clinical use is incompletely understood. Multiple physiologic mechanisms are altered by antiepileptic drugs. Some of these drugs, such as phenytoin and carbamazepine, decrease sustained repetitive firing and post-tetanic potentiation through their blocking effects on the sodium channel. Benzodiazepines and barbiturates enhance GABA-mediated inhibition. Many antiepileptic drugs inhibit calcium influx and calcium-mediated secondary effects at supratherapeutic concentrations. Newer drugs that inhibit excitatory receptors or enhance various forms of inhibition are presently under investigation.     

Place of antiepileptic drug combinations

Over almost 3 millennia, epilepsy was often treated with combinations of agents that were believed at the time of their use to have antiepileptic properties. Bromide, the first really effective remedy for epilepsy, became available in the latter half of the 19th century. After that time, even if some of the previously available agents were employed simultaneously with bromide, there was what amounted to de facto drug monotherapy until other efficacious antiepileptic drugs began to appear from 1912 onwards. Thereafter, antiepileptic drug combinations were widely used until 20 years ago, when pharmacokinetic principles and plasma drug concentration monitoring began to be applied to the treatment of epilepsy. It then soon became clear that skilfully optimized antiepileptic drug monotherapy usually provided satisfactory control of epileptic seizures. Unfortunately, some antiepileptic drug monotherapy failures still occurred. Consequently, with growing knowledge of the molecular mechanisms underlying antiepileptic drug action, and recognition of the apparent success of antiepileptic drug combinations during the clinical trial testing of new antiepileptic agents in monotherapy-resistant patients, the possibilities of rationally-based antiepileptic drug combinations have begun to be considered again. The effectiveness of such combinations and their optimal pattern of use in clinical practice remain to be established.     

Interictal EEG prediction of response to antiepileptic drug monotherapy

Forty-eight patients had sleep-deprived EEGs prior to antiepileptic drug monotherapy. The majority were seizure-free after one year, or had more than 50% reduction in seizure frequency. Among those with normal EEGs 50% were seizure-free, while 75% with diffuse slowing, 44% with focal abnormality, and 83% with generalized epileptiform discharges were fully controlled. Freedom from seizures was achieved in 13% taking phenobarbital, 50% taking phenytoin, 63% taking carbamazepine, and 100% taking valproate. The sleep-deprived interictal EEG should be an integral part of initial assessment and drug selection in patients with clinical histories of convulsive seizure.     

Mucocutaneous eruptions due to antiepileptic drug therapy in children.

Three children with bullous erythema multiforme and 1 with toxic epidermal necrolysis associated with antiepileptic drug therapy are described. One patient is unique because of seven mucocutaneous eruptions caused by three classes of antiepileptic drugs. Lymphocyte stimulation by antiepileptic drugs could not be demonstrated in the 2 patients in whom appropriate studies were performed, and no precipitating antibodies to antiepileptic drugs were found. Observation of four diagnostic and therapeutic principles, which are illustrated by the course of our patients, may reduce the incidence of life-threatening mucocutaneous eruptions and simplify the long-term management of individuals in whom such reactions occur.     

Aspects of antiepileptic drug therapy in children

During the past 10 years, better results in the treatment of epilepsy have been obtained through the application of pharmacokinetic data to drug therapy of epilepsy. However, pediatric drug therapy is complicated by the continuous change in body weight and body composition with the growth and development, especially during infancy. Younger children require a higher dose per kilogram of body weight than older children in order to achieve comparable plasma concentrations. Plasma levels and seizure control were investigated in a prospective randomized study when phenytoin, carbamazepine (CBZ) or sodium valproate (VPA) was given as a single drug to pediatric patients with several types of epileptic seizures. Studies on newly referred, previously untreated children suggest that both partial and generalized tonic-clonic seizures can be prevented by each of the three drugs. No significant differences in clinical efficacy were found among the three drugs, when optimum plasma concentration ranges were maintained with blood level monitoring. Clonazepam (CZP) may be effective in partial seizures. However, as a wide range of plasma levels was associated with complete freedom from seizures, it was not possible to define a therapeutic range for CZP. Any patient who receives multiple-drug therapy is at risk to develop a drug-drug interaction. Simultaneous administration of VPA was associated with a raised plasma level of carbamazepine-10,11-epoxide (CBZ-E), a major metabolite of CBZ, relative to the CBZ dose, whereas the plasma CBZ level remained unaltered. High plasma concentration of CBZ-E may be responsible for side effects in some patients. Drug-protein binding interactions are another source of side effects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinically important drug interactions in epilepsy: interactions between antiepileptic drugs and other drugs

Antiepileptic drugs (AEDs) are commonly prescribed for long periods, up to a lifetime, and many patients will require treatment with other agents for the management of concomitant or intercurrent conditions. When two or more drugs are prescribed together, clinically important interactions can occur. Among old-generation AEDs, carbamazepine, phenytoin, phenobarbital, and primidone are potent inducers of hepatic enzymes, and decrease the plasma concentration of many psychotropic, immunosuppressant, antineoplastic, antimicrobial, and cardiovascular drugs, as well as oral contraceptive steroids. Most new generation AEDs do not have clinically important enzyme inducing effects. Other drugs can affect the pharmacokinetics of AEDs; examples include the stimulation of lamotrigine metabolism by oral contraceptive steroids and the inhibition of carbamazepine metabolism by certain macrolide antibiotics, antifungals, verapamil, diltiazem, and isoniazid. Careful monitoring of clinical response is recommended whenever a drug is added or removed from a patient's AED regimen.