Cognitive and neurodevelopmental effects of antiepileptic drugs

This article primarily represents the contributions of two young investigators to the understanding of the neuropsychological consequences of epilepsy and its treatment. The authors have reviewed two key areas of importance: the complex relationship between cognitive dysfunction and epilepsy and the risks of cognitive dysfunction in children as a consequence of in utero exposure to antiepileptic drug treatment. The work of two young investigators is presented and future research needs are outlined.     

Placental passage of antiepileptic drugs at delivery and neonatal outcomes

Children of women treated with antiepileptic drugs (AEDs) are at increased risk of adverse outcomes detectable in the neonatal period, which may be associated with the amount of AEDs in the fetal circulation. Placental passage of AEDs can be measured by calculating the ratio of umbilical cord to maternal AED concentrations collected at delivery. The aims of this study were to determine the umbilical cord concentrations and umbilical‐to‐maternal ratios for AEDs, and whether higher cord concentrations are associated with increased risk of neonatal complications. AED cord and maternal blood concentrations from 70 mother–newborn dyads and neonatal complications were recorded. Logistic regressions were performed to determine the association between AED concentrations and complications. Mean umbilical‐to‐maternal ratios for total concentrations ranged from 0.79 for carbamazepine to 1.20 for valproic acid, and mean umbilical‐to‐maternal ratios for free concentrations ranged from 0.86 for valproic acid to 1.42 for carbamazepine, indicating complete placental passage. Neither umbilical cord concentrations nor umbilical‐to‐maternal ratios were associated with adverse neonatal outcomes. Additional investigations are warranted to delineate the relationship between quantified fetal AED exposure and neonatal complications.     

Fracture risk associated with use of antiepileptic drugs

PURPOSE: To assess fracture risk associated with different antiepileptic drugs (AEDs). An increased fracture risk has been reported in patients with epilepsy. Classical AEDs have been associated with decreased bone mineral density. The effects of newer AEDs are unknown. METHODS: We undertook a population-based pharmacoepidemiologic case-control study with any fracture as outcome and use of AEDs as exposure variables (124,655 fracture cases and 373,962 controls). RESULTS: All AEDs were associated with an increased fracture risk in an unadjusted analysis. After adjustment for prior fracture, use (ever) of corticosteroids, comorbidity, social variables, and diagnosis of epilepsy, carbamazepine [CBZ; odds ratio (OR), 1.18; 95% confidence interval (CI), 1.10-1.26], [and oxcarbazepine (OXC; 1.14, 1.03-1.26)], clonazepam (CZP; 1.27, 1.15-1.41), phenobarbital (PB; 1.79, 1.64-1.95), and valproate (VPA; 1.15, 1.05-1.26) were statistically significantly associated with risk of any fracture. Ethosuximide (0.75, 0.37-1.52), lamotrigine (1.04, 0.91-1.19), phenytoin (1.20, 1.00-1.43), primidone (1.18, 0.95-1.48), tiagabine (0.75, 0.40-1.41), topiramate (1.39, 0.99-1.96), and vigabatrin (0.93, 0.70-1.22) were not statistically significantly associated with fracture risk after adjustment for confounders. The relative increase was modest and in the same range for the significant and nonsignificant results. CBZ, PB, OXC, and VPA displayed a dose-response relation. Fracture risk was more increased by liver-inducing AEDs (OR, 1.38; 95% CI, 1.31-1.45) than by noninducing AEDs (1.19; 95% CI, 1.11-1.27). CONCLUSIONS: A very limited increased fracture risk is present in users of CBZ, CZP, OXC, PB, and VPA. A limited significant increase cannot be excluded for the other AEDs because of the statistical power.     

Exposure to antiepileptic drugs and the risk of hip fracture: a case-control study

Purpose: To investigate whether the use of antiepileptic drugs (AEDs) increases the risk of hip fracture. Methods: We performed a case‐control study using data from the Funen County (population 2004: 475,000) hip fracture register. Cases (n = 7,557) were all patients admitted to county hospitals with a hip fracture during the period 1996–2004. Controls (n = 27,575) were frequency matched by age and gender. Information on use of AEDs, other drugs, and hospital contacts was available from local registers. Odds ratios (ORs) with 95% confidence intervals (CI) for hip fracture were estimated by unconditional logistic regression. Results: Fracture risk was increased with ever use of any AED (OR: 1.31; 95% CI: 1.16–1.48). The risk was also increased with use of only enzyme inducing (OR: 1.31; 95% CI: 1.14–1.51), but not with use of only noninducing AEDs (OR: 1.03; 95% CI: 0.77–1.37). Current (OR: 1.92; 95% CI: 1.58–2.33) and recent use, as well as high daily (OR: 1.50; 95% CI: 1.24–1.82) and cumulative dose increased fracture risk, but long treatment duration or previous use did not. The risk was modified by the presence of an epilepsy diagnosis. Conclusion: Use of AEDs modestly increases the risk of hip fracture. The risk increase is probably associated to a higher degree with a dose dependent effect on CNS with current and recent use, than with an effect on bone tissue.     

Body dimensions of infants exposed to antiepileptic drugs in utero: observations spanning 25 years

PURPOSE: To investigate the influence of maternal antiepileptic drug (AED) treatment on pregnancy duration, birth weight, body length, head circumference, and intrauterine growth in infants exposed in utero to antiepileptic drugs in Sweden between 1973-1997, with 963 singleton infants. METHODS: Data collected from (a) 1973-1981 (record linkage between a hospital discharge register and a medical birth register); (b) 1984-1995 (prospectively collected information in one defined catchment area with two delivery hospitals); and (c) 1995-1997 (medical birth register data). Observed numbers of infants below a defined size for body measurements compared with expected numbers calculated from all births in Sweden after stratification for year of birth, maternal age, parity, and education or smoking habits in early pregnancy. Standard deviation scores estimated with same stratification procedures. RESULTS: Fraction of monotherapy exposures increased from approximately 40% to approximately 90% from 1973 to 1997. Significantly increased numbers of infants with small body measurements found in exposed group. Negative influence on body dimensions decreased over time. More marked effects found in infants exposed to polytherapy. In monotherapy, only infants exposed to carbamazepine consistently showed reduction in body dimensions. Significant effect on gestational age in girls and on number of small for gestational age (<2 SD) in boys. CONCLUSIONS: Polytherapy with antiepileptic drugs and negative influence on body dimensions decreased. In monotherapy, only carbamazepine has a negative influence on body dimensions in this study.     

Prospective study on the withdrawal and reinstitution of antiepileptic drugs among seizure-free patients in west China

This study explored the relapse rates and risk factors for seizure recurrence after discontinuing antiepileptic drug (AED) therapy among seizure-free patients in west China, and explored whether to reinstitute AED immediately after a single seizure after AED withdrawal. Patients with epilepsy who were seizure-free for at least 2 years and decided to gradually stop AED therapy were followed up every 3 months for seizure relapse. Patients who experienced their first seizure after drug withdrawal were divided into two groups according to their willingness to reinstitute AED therapy, and were followed up until their second seizure. In the mean 29.35 months of follow-up, 37 patients (37/162, 22.8%) suffered at least one seizure after withdrawal. The cumulative probability of seizure recurrence was 16% at 12 months and 20.2% at 24 months. AED response time >1 year and multiple types of seizure were identified as risk factors for seizure recurrence. Eight patients (8/32, 25%) suffered a second seizure within 1 year after the first whether or not they reinstituted AED immediately. There were no significant demographic or clinical differences between patients who reinstituted AED therapy and those who did not. The epilepsy recurrence rate after AED withdrawal is relatively low, with a relatively slow tapering process. Patients with long AED response times and/or multiple types of seizures have a higher risk of seizure recurrence. The first seizure after drug withdrawal is not an indication for immediate AED reinstitution, but may be recommended after a second seizure.     

Self-discontinuation of antiepileptic medication in pregnancy: detection by hair analysis

PURPOSE: Concerns over teratogenicity of antiepileptic drugs (AEDs) during pregnancy must be balanced against the risks of seizures to the mother and developing fetus. Pharmacokinetic changes and vomiting may alter drug levels, but more important may be the patient's decision to stop medication before or during pregnancy. Compliance assessment traditionally relies either on self-reporting or on AED plasma level monitoring; neither provides reliable information on drug-taking behaviour over an extended interval (e.g., before, during, and after pregnancy). METHODS: We have used hair analysis to assess AED-taking behavior in pregnant women compared with nonpregnant female controls. Twenty-six pregnant women [mean age, 27.5 +/- 6.7 (SD) years] and 13 nonpregnant female epilepsy outpatients (mean age, 31.9 +/- 8.3 years) were studied. Carbamazepine (CBZ) or lamotrigine (LTG) concentrations were measured in 1-cm hair segments, and the within-subject variance in segmental hair concentrations of these drugs was calculated for each group. The variances of each group were then compared by using a variance ratio test. RESULTS: The variance of AED concentration in hair differed significantly between the pregnant and nonpregnant groups [variance ratio, 1.59 (p < 0.01)]. Four (15%) of the 26 pregnant patients had little or no AED in their proximal hair segments compared with more distal segments, apparently having discontinued their medication during pregnancy. Only one of these later disclosed having stopped her medication. One pregnant woman whose hair profile was similar to controls died suddenly at 30 weeks of gestation. CONCLUSIONS: This study confirms the perception that pregnant women with epilepsy frequently stop or greatly reduce their prescribed medication, usually without reference or acknowledgement to their clinician.     

Assessment of CNS effects of antiepileptic drugs by using quantitative EEG measures

PURPOSE: Antiepileptic drugs (AEDs) can be associated with adverse neurologic effects including cognitive dysfunction. Objective methods for recognizing AED effects on the brain could be valuable for long-term management. We compared quantitative EEG measures and cognitive tests in a group of patients beginning or ending AED therapy. METHODS: Subjects included 20 patients beginning AED therapy (AEDon), 12 patients stopping AED therapy (AEDoff), 33 patient controls receiving stable AED therapy (AEDco), and 73 healthy controls (Nco). All subjects underwent structured EEG recording and a cognitive test battery before change in AED dose and again 12-16 weeks later, >or=4 weeks after the last dose change. Four occipital EEG measures (peak frequency, median frequency, relative theta and delta power) were analyzed. Cognitive test changes were scored by using test-retest regression equations based on the Nco subjects. Wilcoxon tests were used for two-group comparisons. RESULTS: AEDons had a significant decrease, and AEDoffs, a significant increase in the peak frequency of the EEG rhythm, as compared with controls. Results for median frequency and theta power were similar. Change in the EEG peak frequency correlated with an aggregate cognitive change measure (r2= 0.71; p < 0.001), individual cognitive measures, and subjective complaints. Of the combined AEDon/AEDoff patients, 58% exceeded the 95% confidence interval for test-retest change in EEG peak frequency. CONCLUSIONS: Quantitative measures derived from the occipital EEG are sensitive to AEDs and correlate with AED-related cognitive effects and subjective complaints. Although this correlation does not indicate a direct relation, quantified EEG may be a practical measure of AED impact on the brain.     

抗癫痫药物对癫痫患者甲状腺激素水平影响的研究

目的 研究癫痫患者甲状腺激素水平和抗癫痫药物对其影响以及与疗效之间的关系。方法 测定已确诊的45例未服用过抗癫痫药物的癫痫患者血清甲状腺激素水平并与30例健康对照组进行比较。再经卡马西平、苯妥英钠、丙戊酸钠三种抗癫痫药物分组单药治疗3个月、6个月、年后观察甲状腺激素水平的变化及与疗效之间的关系。结果 未服用抗癫痫药物的新诊断癫痫患者游离甲状腺素（FT4）水平显著低于健康对照组,经苯妥英钠、卡马西平分别治疗3个月、6个月、1年后T4、FT4、FT3显著低于治疗前水平,TSH无显著性变化。经丙戊酸钠治疗后的不同时间段各甲状腺激素水平与治疗前比较无显著性差异（P＞0．05）。甲状腺激素水平的变化与化疗效之间似无相关性。结论 癫痫的反复发作虽未经抗癫痫药物治疗已存在FT4水平的降低。苯妥英钠、卡马西平可明显造成癫痫患者的亚临床甲状腺功能降低（T4、FT4、FT3下降）,丙戊酸钠对患者甲状腺激素水平无显著影响。甲状腺激素水平的变化与疗效之间无相关性。     

Availability of antiepileptic drugs across Europe

Europe consists of 53 countries with widely different economic conditions and different political, educational, and health care systems. This study was aimed at determining the availability of antiepileptic drugs (AEDs) across Europe. An electronic questionnaire was submitted to all 43 European chapters of the International League Against Epilepsy (ILAE). Outcome measures were availability of older, newer, and newest AEDs, generic products, indications, reimbursement rules, and reasons for lack of availability of AEDs. Countries were divided according to economic status as defined by the World Bank. Thirty‐four chapters (79%) provided data. There were large differences in AED availability across countries, especially between high‐income countries and the other countries. The newest AEDs were not available in any of the 12 non–high‐income countries. Availability was higher in countries with public reimbursement systems. Reimbursement policies ranged from full reimbursement for all AEDs to complete lack of reimbursement. Main hurdles for poor access to AEDs included lack of regulatory approval, high prices and reimbursement restrictions. The availability of AEDs differs across European countries, with many hurdles hampering access to epilepsy medicines, particularly to new medications. These findings raise major concerns on the quality of epilepsy care in many countries.     

Motor and mental development of infants exposed to antiepileptic drugs in utero

We prospectively evaluated the mental (MeDQ) and motor (MoDQ) developmental quotients of 395 (67.5% of the eligible) infants of mothers with epilepsy (IME) (mean age: 15 months) enrolled in the Kerala Registry of Epilepsy and Pregnancy between 1998 and 2004. The same developmental pediatricians, blinded to antiepileptic drug (AED) exposure, evaluated the children using the Indian adaptation of the Bayley Scale of Infant Development: Their mean MeDQ was 89.1+/-29.9 and mean MoDQ was 90.7+/-26.9. The MeDQ and MoDQ were impaired (<84) for 150 (37.6%) and 133 (33.5%) IME, respectively. Maternal age, type of epilepsy, seizure frequency, or use of folic acid did not correlate with the mean MeDQ or MoDQ. Maternal education was significantly correlated with the MoDQ, but not with the MeDQ, of the infants. Infants not exposed to AEDs (n=32) had a higher MeDQ (mean: 92.3, 95% CI: 81.4-103.2) and MoDQ (mean 94.7; 95% CI 84.9-104.5) than those exposed to AEDs (MeDQ--mean: 88.6, 95% CI: 85.5-91.6; MoDQ--mean: 90.0, 95% CI: 87.3-92.8). Those exposed to polytherapy had significantly lower developmental quotients than those exposed to monotherapy. Cumulative AED scores during pregnancy had an inverse relationship with developmental quotients. On multiple regression analysis, polytherapy was a stronger predictor of lower developmental quotients than dosage. Compared with carbamazepine monotherapy, valproate monotherapy was associated with significantly lower MeDQ and MoDQ in IME (93.1 and 95 vs 86.9 and 86.1), but the differences between other AEDs were not significant for IME exposed to valproate monotherapy. A limitation of the study is that the influence of maternal intelligence on developmental quotients was not evaluated.     

Factors determining response to antiepileptic drugs in randomized controlled trials. A systematic review and meta-analysis

Purpose: Because of the lack of head‐to‐head adjunctive‐therapy trials of antiepileptic drugs (AEDs) in refractory partial epilepsy, meta‐analyses of placebo‐controlled randomized controlled trials (RCTs) represent a potentially important source of evidence to guide treatment decisions. However, such indirect comparisons raise various methodologic issues that may hamper their relevance. Methods: All RCTs in adult refractory partial epilepsy were analyzed to assess whether efficacy outcomes are influenced by: characteristics of patients and trials ; use of last observation carried forward (LOCF) analysis; evaluation period (entire period versus maintenance period); and year of publication. A meta‐analysis of these AEDs was then performed taking these factors into consideration. Key Findings: Sixty‐three RCTs evaluating 20 AEDs were included. The following variables influenced efficacy estimates: (1) responder rates correlated positively with duration of the entire treatment period (p = 0.038); (2) response to placebo was significantly greater in the maintenance period than in the entire treatment period (p = 0.005); (3) responder rates increased over the years both for AEDs (p < 0.001) and for placebo (p = 0.001); (4) LOCF analysis overestimated responder rates for AEDs (p < 0.001) and for placebo (p = 0.001) compared with completer‐based analysis, and the overestimation correlated positively with withdrawal rates (p < 0.001). A meta‐analysis of available data showed large differences in efficacy ranking in relation to dose selection and type of analysis, but these were mostly nonsignificant due to statistical power limitations. Significance: Several methodologic issues hamper the relevance of indirect comparisons of AEDs in the adjunctive‐therapy of refractory partial epilepsy. Some of these issues could be overcome by improved standardization in the reporting of efficacy outcomes.     

The ABCC2 c.-24C > T polymorphism increases the risk of resistance to antiepileptic drugs: A meta-analysis

Several studies examined a possible link between multidrug resistance-associated protein 2 (ABCC2) gene variants and the risk of resistance to antiepileptic drugs (AEDs) in epilepsy, but the results were contradictory. In this study, a meta-analysis was conducted to assess the relevance of ABCC2 common variants (c.-24C > T, c.1249G > A, c.3972C > T) with the response risk of AEDs. We searched Embase, PubMed, the Cochrane Library and CNKI databases for case-control studies published through May 2016 that evaluated the role of ABCC2 gene variants in pharmacoresistance to AEDs. Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated to assess the strength of associations between the ABCC2 c.-24C > T, c.1249G > A and c.3972C > T variants and the risk of resistance to AEDs using an allele frequency model, dominant model and recessive model. Subgroup analyses were performed by ethnicity and the definition of drug-resistance. A total of 13 published studies involving 4300 patients (2261 patients with drug-resistant epilepsy and 2039 controls with drug-responsive epilepsy) met the selection criteria. We observed that the variant c.-24C > T was associated with a significantly increased risk of AED resistance (TT + CT vs CC: OR = 1.24, 95%CI = 1.06–1.46, p = 0.009; TT vs CT + CC: OR = 1.90, 95%CI = 1.31–2.76, p = 0.0008; T vs C: OR = 1.27, 95%CI = 1.11–1.46, p = 0.0006). However, we identified no significant association of the ABCC2 c.1249G > A, c.3972C > T variants and haplotypes with the response to anticonvulsant drug in the overall population. In summary, these observations suggest that the ABCC2 c.-24C > T polymorphism is a likely risk factor for resistance to AEDs.     

Efficacy and tolerability of antiepileptic drugs in an Omani epileptic population

OBJECTIVE: The aim of this hospital-based study is to get an insight into the efficacy and tolerability of antiepileptic drugs (AED) in Omani epileptic patients. PATIENTS AND METHODS: All Omani patients (aged 14 years and above) suffering from epileptic seizures for at least 2 years and followed-up by board-certified neurologists in Sultan Qaboos University Hospital (SQUH) were evaluated. The treatment retention rate since first visit at SQUH and over the last 2 years was used as primary efficacy measure of AED therapy. Change in seizure-frequency and side effect profiles were also assessed. RESULTS: In this population of 203 confirmed epileptic patients, generalized tonic-clonic (40%) and partial seizures (39%) were most commonly observed, idiopathic/cryptogenic origin (81%) being the most frequent encountered origin. Sixty one percent of the patients were controlled with an AED in monotherapy and overall 34% of patients could be successfully maintained on monotherapy during the whole follow-up period at SQUH (median 6 years). The treatment retention rates for carbamazepine (CBZ) at a daily dose of 400-600 mg, sodium valproate (VPA) at a daily dose of 500-1000 mg, and phenytoin (PHT) at a daily dose of 300 mg, in monotherapy over the total follow-up period was 51, 50, and 21%, respectively. In contrast, over the last 2 years these rates were highest for VPA (91%) followed by CBZ (83%) and PHT (73%). Adverse drug reactions were recorded in 67% of patients, and were most commonly encountered with VPA. CONCLUSIONS: Despite a higher adverse effect profile for VPA, long-term treatment with CBZ and VPA appeared to be equally effective in terms of treatment retention rates and seizure control.