Comparison of oxcarbazepine efficacy and MHD concentrations relative to age and BMI: Associations among ABCB1, ABCC2, UGT2B7, and SCN2A polymorphisms

Pharmacogenetics and Oxcarbazepine in Children and Adolescents: Beyond HLA-B*15:02

Background: Oxcarbazepine is thought to be better-tolerated and less susceptible to drug-drug interactions than its predecessor, carbamazepine. Genetic testing for HLA-B*15:02 is recommended in specific populations to identify those at high risk of severe hypersensitivity reactions; however, other pharmacologic and pharmacogenetic factors that can impact drug disposition may be involved. Methods: We present a case of an 8-year-old boy treated with oxcarbazepine who developed drug reaction with eosinophilia and systemic symptoms (DRESS) with Stevens-Johnsons syndrome overlap and was negative for HLA-B*15:02. We review the extant literature related to oxcarbazepine disposition, and potential pharmacogenetic variants in aldoketoreductase 1C (AKR1C)2-4 that may contribute to this risk. Results: Genetic variability in oxcarbazepine disposition pathways may contribute to tolerability and toxicity, including the development of hypersensitivity reactions. Conclusions: While preemptive genetic testing for HLA-B*15:02 in individuals of Asian ancestry is recommended to prevent severe hypersensitivity reactions to oxcarbazepine, oxcarbazepine concentrations and AKR1C variation may contribute to the risk of severe adverse reactions. We provide recommendations for future study to elucidate whether these individual factors are important for reducing the risk of severe adverse events.

Therapeutic monitoring of anti-seizure medications in low- and middle-income countries: a systematic review

Background

The treatment gap for epilepsy is large in low- and middle-income countries (LMICs) and the effectiveness and safety of the available anti-seizure medication (ASMs) is not fully understood. We systematically reviewed available evidence on therapeutic drug monitoring (TDM) of ASM in LMIC.

Methods

We searched four main databases (PubMed, Psych-Info, CINAHL and Embase) up to 31 st December 2020, with eligible articles screened using a PRISMA checklist and a set of exclusion and inclusion criteria. Full texts were examined to evaluate the extent and practice of TDM in LMICs. Analyses were performed using Stata 13 and descriptive statistics were used to pool median distribution of TDM across studies.

Results

Of the 6,309 articles identified in the initial search, 65 (1.0%) met the eligibility criteria. TDM of ASMs was mostly done to assess toxicity (42.8%), but rarely to monitor adherence (9.0%). TDM differed by economic status and infrastructural status with majority of the studies coming from Europe (53.8%) and upper-middle-income countries (87.6%). First generation ASMs (82.3%) were more likely to be monitored than second generation ASMs (17.6%) and carbamazepine was the most frequently monitored drug. Fluorescence Polarization Immunoassay (FPIA) was the most common technique used for TDM (41.5%) followed by High-Performance Liquid Chromatography (HPLC) (16.9%). In addition, FPIA was the cheapest method of TDM based on approximated costs ($1000, TDx system). Assay validation and quality control were reported variably, and reference ranges used during TDM of ASMs were relatively uniform.

Conclusions

TDM is mostly done to evaluate ASM toxicity, but rarely for other reasons such as evaluating adherence or assessing clinical efficacy. There is a need for more investment in comprehensive and targeted TDM in LMICs when initiating treatment, switching therapies, adding or removing ASM and evaluating treatment response and safety of both first generation and second generation ASMs.

Population pharmacokinetics of oxcarbazepine active metabolite in Chinese children with epilepsy

Oxcarbazepine (OXC) is an antiepileptic drug whose efficacy is largely attributed to its monohydroxy derivative metabolite (MHD). Nevertheless, there exists significant inter-individual variability in both the pharmacokinetics and therapeutic response of this drug. The objective of this study is to explore the impact of patients' characteristics and genetic variants on MHD clearance in a population pharmacokinetic (PPK) model of Chinese pediatric patients with epilepsy. The PPK model was developed using a nonlinear mixed effects modeling method based on 231 MHD plasma concentrations obtained from 185 children with epilepsy. The one-compartment model and combined residual model were established to describe the pharmacokinetics of MHD. Forward addition and backward elimination were employed to evaluate the impact of covariates on the model parameters. The model was evaluated using goodness-of-fit, bootstrap, visual predictive checks, and normalized prediction distribution errors. In the two final PPK models, age, estimated glomerular filtration rate (eGFR), and a combined genotype of six variants (rs1045642, rs2032582, rs7668282, rs2396185, rs2304016, rs1128503) were found to significantly reduce inter-individual variability for MHD clearance. The inter-individual clearance equals to 1.38 × (Age/4.74)0.29 × (eGFR/128.66)0.25 × eθABCB-UGT-SCN-INSR for genetic variants included model and 1.30 × (Age/4.74)0.30 × (eGFR/128.66)0.23 for model without genetic variants. The precision of all parameters was deemed acceptable, and the model exhibited good predictability while remaining stable and effective.    Conclusion: Age, eGFR, and genotype may play a significant role in MHD clearance in children with epilepsy. The developed PPK models hold potential utility in facilitating oxcarbazepine dose adjustment in pediatric patients. What is Known: • The adjustment of the oxcarbazepine regimen remains difficult due to the considerable inter- and intra-individual variability of oxcarbazepine pharmacokinetics. • Body weight and co-administration with enzyme-inducing antiepileptic drugs emerge as the most influential factors contributing to the pharmacokinetics of MHD. What is New: • A positive correlation was observed between eGFR and the clearance of MHD in pediatric patients with epilepsy. • We explored the influence of genetic polymorphisms on MHD clearance and identified a combined genotype (ABCB-UGT-SCN-INSR) that exhibited a significant association with MHD concentration.

Impact of ABCC2 1249G>A and -24C>T Polymorphisms on Lacosamide Efficacy and Plasma Concentrations in Uygur Pediatric Patients With Epilepsy in China

PURPOSE

We aimed to evaluate the effect of the ABCC2 1249G>A (rs2273697) and -24C>T (rs717620) polymorphisms on lacosamide (LCM) plasma concentrations and the efficacy of LCM in Uygur pediatric patients with epilepsy.

METHODS

We analyzed 231 pediatric patients with epilepsy, among which 166 were considered to be LCM responsive. For drug assays, 2-3 mL of venous blood was collected from each patient just before the morning LCM dose was administered (approximately 12 hours after the evening dose, steady-state LCM concentrations). The remaining samples after routine therapeutic drug monitoring were used for genotyping analysis. The χ 2 test and Fisher exact test were utilized for comparative analysis of the allelic and genotypic distribution of ABCC2 polymorphisms between the LCM-resistant and LCM-responsive groups. The Student t test or Mann-Whitney U test was conducted to analyze differences in plasma LCM concentration among pediatric patients with epilepsy with different genotypes.

RESULTS

Patients with the ABCC2 1249G>A GA genotype (0.7 ± 0.3 mcg/mL per kg/mg) and AA genotype (0.5 ± 0.3 mcg/mL per kg/mg) showed significantly ( P < 0.001) lower LCM concentration-to-dose (CD) ratios than patients with the GG genotype (1.0 ± 0.4 mcg/mL per kg/mg). Moreover, patients with the ABCC2 -24C>T CT genotype (0.6 ± 0.2 mcg/mL per kg/mg) and TT genotype (0.6 ± 0.3 mcg/mL per kg/mg) presented a significantly ( P < 0.001) lower LCM CD ratio than patients with the CC genotype (1.1 ± 0.4 mcg/mL per kg/mg).

CONCLUSIONS

The ABCC2 1249G>A (rs2273697) and ABCC2 -24C>T (rs717620) polymorphisms can affect plasma LCM concentrations and treatment efficacy among a population of Uygur pediatric patients with epilepsy, causing these patients to become resistant to LCM. In clinical practice, ABCC2 polymorphisms should be identified before LCM treatment, and then, the dosage should be adjusted for pediatric patients with epilepsy accordingly.

Type 2 Diabetes Risk and Lipid Metabolism Related to the Pleiotropic Effects of an ABCB1 Variant: A Chinese Family-Based Cohort Study

The single nucleotide polymorphism (SNP) rs4148727 in ABCB1 (encoding p-glycoprotein) is associated with lipid levels; however, its association with type 2 diabetes (T2DM) and its the genetic correlation with lipid profiles and T2DM are unclear. We included 2300 participants from 593 families. A generalized estimating equations (GEE) model and Cox regression models were used to estimate the SNP’s effects on T2DM and lipid profiles. The participation of the SNP in T2DM pathogenesis through lipid-associated pathways was tested using mediation analysis. The G allele of the SNP was related to a 32% (6–64%, p = 0.015) increase in T2DM risk. It was also associated with a 10% (1–20%, p = 0.029), 17% (3–32%, p = 0.015), and 4% (1–7%, p = 0.015) increment in total cholesterol (TC), triglyceride (TG), and apolipoprotein A (Apo-A) concentrations, respectively. According to the mediation analysis, only TG (6.9%) and Apo-B (4.0%) had slight but significant mediation effects on the total impact of the SNP on T2DM. The pleiotropic effects of the ABCB1 variant on T2DM and lipids likely act via different pathways. The biological mechanisms should be verified in a future study.

Analysis of influencing factors on monohydroxylated derivative of oxcarbazepine plasma concentration in children with epilepsy

PURPOSE

This study aimed to investigate the factors affecting the plasma concentration of monohydroxylated derivative (MHD) of oxcarbazepine (OXC) in children with epilepsy.

METHODS

We recruited 125 children with epilepsy who received OXC monotherapy. Among them, 16 single nucleotide polymorphisms were detected by MassARRAY genotyping technology to evaluate the influence of related factors on the plasma concentration of OXC monotherapy. MHD is the main active metabolite of OXC, and its plasma concentration was measured by high-performance liquid chromatography (HPLC).

RESULTS

Bivariate correlation analysis revealed that concentration-dose ratio (CDR) increased with weight, and the corresponding maintenance dose decreased with weight (r=0.317, P=0.001 for CDR; r=-0.285, P=0.000 for OXC maintenance dose). The duration of seizure was found to be associated with CDR (0.90 ± 0.36 vs 0.74 ± 0.26 μg·kg/mg/mL for ≥6 years vs <1 year, P=0.028; 0.90 ± 0.36 vs 0.64 ± 0.21 μg·kg/mg/mL for ≥6 years vs 1-3 years, P=0.004; 0.90 ± 0.36 vs 0.69 ± 0.18 μg·kg/mg/mL for ≥6 years vs 3-6 years, P=0.031). The CDR of patients with ABCB1 rs1045642 mutation homozygous GG type is higher than heterozygous AG type (0.79 ± 0.30 vs 0.68 ± 0.20 μg·kg/mg/mL for AG vs GG, P=0.032).

CONCLUSION

This study clarified the association of weight, duration of seizure, and gene polymorphisms of ABCB1 rs1045642 with MHD plasma concentration in children with epilepsy.

Association between G2677T/A polymorphism in ABCB1 gene and the risk of drug resistance epilepsy: An updated systematic review and meta-analysis

PURPOSE

Epilepsy is a common serious brain condition characterized by the abnormal electrical activity of neurons. In most cases, epileptic patients respond to antiepileptic drugs. Approximately, one-third of patients prove medically intractable. The ABCB1 gene is a superfamily of ATP-binding cassette (ABC) transporters that encode a drug-transport protein, lead to cells and organs protects and eliminates toxic agents. We performed this meta-analysis to assess the association between G2677T/A in the ABCB1 gene and the risk of drug resistance in epileptic patients.

METHODS

Two online libraries (PubMed and Scopus) were used to identify studies that report the relationship between G2677T/A polymorphism in the MDR1 gene and the risk of antiepileptic drug resistance. The meta-analysis was performed using Review Manager 5.3 software. The pooled odds ratios and 95 % confidence intervals (CIs) were calculated using a random or fixed effects model according to the heterogeneity between studies.

RESULTS

A total of 33 eligible studies were included in this meta-analysis which 4192 patients were drug-resistant and 5079 patients were drug-responsive. As a result, a significant association was observed in overall population for the genetic model GG+GA vs AA (OR with 95 % CI = 0,56 [0.34,0.93]; P = 0.02). The subgroup ethnicity analysis showed a significant decrease in the risk of AEDs resistance in the Caucasian population.

CONCLUSION

In conclusion, our analysis demonstrates that G2677T/A polymorphism in the ABCB1 gene decreases the risk of drug resistance. More studies are needed in the different ethnic groups to clarify the role of polymorphism in AEDs resistance.

Impact of ABCB1 Polymorphisms on Lacosamide Serum Concentrations in Uygur Pediatric Patients With Epilepsy in China

BACKGROUND

P-glycoprotein, encoded by ABCB1 (or MDR1), may contribute to drug resistance in epilepsy by limiting gastrointestinal absorption and brain access to antiseizure medications. The study aimed to evaluate the impact of ABCB1 polymorphisms on lacosamide (LCM) serum concentrations in Uygur pediatric patients with epilepsy.

METHODS

The serum concentrations of LCM were determined by ultrahigh performance liquid chromatography, and the ABCB1 polymorphism was analyzed through polymerase chain reaction-fluorescence staining in situ hybridization. The χ2 test and the Fisher exact test were used to analyze the allelic and genotypic distributions of ABCB1 polymorphisms between the drug-resistant and drug-responsive patient groups. Differences in steady-state and dose-corrected LCM serum concentrations between different genotypes were analyzed using the one-way analysis of variance and the Mann-Whitney test.

RESULTS

A total of 131 Uygur children with epilepsy were analyzed, and of them, 41 demonstrated drug resistance. The frequency of the GT genotype of ABCB1 G2677T/A was significantly higher in the drug-resistant group than that in the drug-responsive group (P < 0.05, OR = 1.966, 95% CI, 1.060-3.647). Patients with the G2677T/A-AT genotype had a statistically significantly lower concentration-to-dose (CD) value than patients with the G2677T/A-GG genotype (mean: 0.6 ± 0.2 versus 0.8 ± 0.5 mcg/mL per mg/kg, P < 0.001). Significantly lower LCM serum concentrations were observed in ABCB1 C3435T CT and TT genotype carriers than those in the CC carriers (P = 0.008 and P = 0.002), and a significantly lower LCM CD value was observed in ABCB1 C3435T CT genotype carriers than that in the CC carriers (P = 0.042).

CONCLUSIONS

ABCB1 G2677T/A and C3435T polymorphisms may affect LCM serum concentrations and treatment efficacy in Uygur pediatric patients with epilepsy, leading to drug resistance in pediatric patients.

Pharmacogenetics of Drug-Resistant Epilepsy (Review of Literature)

Pharmacogenomic studies in epilepsy are justified by the high prevalence rate of this disease and the high cost of its treatment, frequent drug resistance, different response to the drug, the possibility of using reliable methods to assess the control of seizures and side effects of antiepileptic drugs. Candidate genes encode proteins involved in pharmacokinetic processes (drug transporters, metabolizing enzymes), pharmacodynamic processes (receptors, ion channels, enzymes, regulatory proteins, secondary messengers) and drug hypersensitivity (immune factors). This article provides an overview of the literature on the influence of genetic factors on treatment in epilepsy.

Pharmacogenomics variants are associated with BMI differences between individuals with bipolar and other psychiatric disorders

Aim: Regardless of the plethora of next-generation sequencing studies in the field of pharmacogenomics (PGx), the potential effect of covariate variables on PGx response within deeply phenotyped cohorts remains unexplored. Materials & methods: We explored with advanced statistical methods the potential influence of BMI, as a covariate variable, on PGx response in a Greek cohort with psychiatric disorders. Results: Nine PGx variants within UGT1A6, SLC22A4, GSTP1, CYP4B1, CES1, SLC29A3 and DPYD were associated with altered BMI in different psychiatric disorder groups. Carriers of rs2070959 (UGT1A6), rs199861210 (SLC29A3) and rs2297595 (DPYD) were also characterized by significant changes in the mean BMI, depending on the presence of psychiatric disorders. Conclusion: Specific PGx variants are significantly associated with BMI in a Greek cohort with psychiatric disorders.

Therapeutic monitoring of anti-seizure medications in low- and middle-income countries: a systematic review

Background: The treatment gap for epilepsy is large in low- and middle-income countries (LMICs) and the effectiveness and safety of the available anti-seizure medication (ASMs) is not fully understood. We conducted a systematic review to evaluate the extent of therapeutic drug monitoring (TDM) of ASM in LMIC, including purposes and methods used during monitoring. Methods: A search was conducted on four main databases (PubMed, Psych-Info, CINAHL and Embase), with eligible articles screened using a PRISMA checklist and a set of exclusion and inclusion criteria. Full texts were examined to evaluate the extent and practice of TDM in LMICs. Descriptive statistics were used to pool median distribution of TDM across studies. Results: Of the 6,309 articles identified in the initial search, 65 (1.0%) met the eligibility criteria. TDM of ASMs was mostly done to assess toxicity (42.8%), but rarely to monitor adherence (9.0%). TDM differed by economic status and infrastructural status with majority of the studies coming from Europe (53.8%) and upper-middle-income countries (87.6%). First generation ASMs (82.3%) were more likely to be monitored than second generation ASMs (17.6%) and carbamazepine was the most frequently monitored drug. Fluorescence Polarization Immunoassay (FPIA) was the most common technique used for TDM (41.5%) followed by High-Performance Liquid Chromatography (HPLC) (16.9%). In addition, FPIA was the cheapest method of TDM based on approximated costs ($1000, TDx system). Assay validation and quality control were reported variably, and reference ranges used during TDM of ASMs were relatively uniform. Conclusions: TDM is mostly done to evaluate ASM toxicity, but rarely for other reasons such as evaluating adherence or assessing clinical efficacy. There is a need for more investment in comprehensive TDM in LMICs that incorporates dose titration of ASM using pharmacokinetics and pharmacodynamics modelling, for both first generation and second generation ASMs.

Identification of human uridine diphosphate-glucuronosyltransferase isoforms responsible for the glucuronidation of 10,11-dihydro-10-hydroxy-carbazepine

OBJECTIVES

To determine the kinetics of the formation of 10,11-dihydro-10-hydroxy-carbazepine (MHD)-O-glucuronide in human liver microsomes (HLMs), human intestine microsomes (HIMs), human kidney microsomes (HKMs) and recombinant human UDP-glucuronosyltransferase (UGTs), and identify the primary UGT isoforms catalyzing the glucuronidation of MHD.

METHODS

The kinetics of the glucuronidation of MHD was determined in HLMs, HIMs as well as HKMs. Screening assays with 13 recombinant human UGTs, inhibition studies and correlation analysis were performed to identify the main UGTs involved in the glucuronidation of MHD.

KEY FINDINGS

MHD-O-glucuronide was formed in HLMs, HIMs as well as HKMs, HLMs showed the highest intrinsic clearance of MHD. Among 13 recombinant human UGTs, UGT2B7 and UGT1A9 were identified to be the principal UGT isoforms mediating the glucuronidation of MHD, while UGT1A4 played a partial role. In addition, inhibition studies and correlation analysis further confirmed that UGT2B7 and UGT1A9 participated in the formation of MHD-O-glucuronide.

CONCLUSIONS

MHD could be metabolized by UGTs in the liver, intestine and kidney, and the hepatic glucuronidation was the critical metabolic pathway. UGT2B7 and UGT1A9 were the primary UGT isoforms mediating the formation of MHD-O-glucuronide in the liver.

Developing a gene panel for pharmacoresistant epilepsy: a review of epilepsy pharmacogenetics

Evaluating genes involved in the pharmacodynamics and pharmacokinetics of epilepsy drugs is critical to better understand pharmacoresistant epilepsy. We reviewed the pharmacogenetics literature on six antiseizure medicines (carbamazepine, perampanel, lamotrigine, levetiracetam, sodium valproate and zonisamide) and compared the genes found with those present on epilepsy gene panels using a functional annotation pathway analysis. Little overlap was found between the two gene lists; pharmacogenetic genes are mainly involved in detoxification processes, while epilepsy panel genes are involved in cell signaling and gene expression. Our work provides support for a specific pharmacoresistant epilepsy gene panel to assist antiseizure medicine selection, enabling personalized approaches to treatment. Future efforts will seek to include this panel in genomic analyses of pharmacoresistant patients, to determine clinical utility and patient treatment responses.

Pharmacogenetics of Carbamazepine and Valproate: Focus on Polymorphisms of Drug Metabolizing Enzymes and Transporters

Pharmacogenomics can identify polymorphisms in genes involved in drug pharmacokinetics and pharmacodynamics determining differences in efficacy and safety and causing inter-individual variability in drug response. Therefore, pharmacogenomics can help clinicians in optimizing therapy based on patient's genotype, also in psychiatric and neurological settings. However, pharmacogenetic screenings for psychotropic drugs are not routinely employed in diagnosis and monitoring of patients treated with mood stabilizers, such as carbamazepine and valproate, because their benefit in clinical practice is still controversial. In this review, we summarize the current knowledge on pharmacogenetic biomarkers of these anticonvulsant drugs.

ABCB1, ABCG2, ABCC1, ABCC2, and ABCC3 drug transporter polymorphisms and their impact on drug bioavailability: what is our current understanding?

INTRODUCTION

Interindividual differences in drug response are a frequent clinical challenge partly due to variation in pharmacokinetics. ATP-binding cassette (ABC) transporters are crucial determinants of drug disposition. They are subject of gene regulation and drug-interaction; however, it is still under debate to which extend genetic variants in these transporters contribute to interindividual variability of a wide range of drugs.

AREAS COVERED

This review discusses the current literature on the impact of genetic variants in ABCB1, ABCG2 as well as ABCC1, ABCC2, and ABCC3 on pharmacokinetics and drug response. The aim was to evaluate if results from recent studies would increase the evidence for potential clinically relevant pharmacogenetic effects.

EXPERT OPINION

Although enormous efforts have been made to investigate effects of ABC transporter genotypes on drug pharmacokinetics and response, the majority of studies showed only weak if any associations. Despite few unique results, studies mostly failed to confirm earlier findings or still remained inconsistent. The impact of genetic variants on drug bioavailability is only minor and other factors regulating the transporter expression and function seem to be more critical. In our opinion, the findings on the so far investigated genetic variants in ABC efflux transporters are not suitable as predictive biomarkers.

Possible interplay between the theories of pharmacoresistant epilepsy

Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.

Association of xenobiotic receptor polymorphisms with carbamazepine response in epilepsy patients

PURPOSE

Drug-resistant epilepsy is a problem worldwide. Xenobiotic receptors may play a significant role in the establishment of resistance to antiepileptic agents. Previous studies have confirmed that the metabolism and efficacy of carbamazepine (CBZ) can be influenced by xenobiotic receptors, especially pregnane X receptor (PXR), constitutive androstane receptor (CAR), and aryl hydrocarbon receptor (AHR). Therefore, this study intends to elucidate the pharmacogenomic associations of polymorphisms of these xenobiotic receptors with the CBZ response in epilepsy patients, and these genetic data may be useful for the treatment of clinical prophylaxis and individualized treatment of intractable epilepsy.

METHODS

Adult patients with epilepsy who were on CBZ-based monotherapy and combination therapy (n = 257) were genotyped, and the patients were divided into drug-responsive and drug-resistant groups according to the International League Against Epilepsy criteria. We sought to tag single-nucleotide polymorphisms (SNPs) of PXR, CAR and AHR that principally represent alleles associated with drug resistance risk; in addition, a gene interaction analysis reference panel was constructed for SNP-based imputation.

RESULTS

No significant effects of PXR or AHR polymorphisms were observed. However, an interaction between the CAR rs2502815 variant and CBZ response was observed: in CBZ-based monotherapy and combination therapy patients, the GG genotype of the CAR rs2502815 variant (vs. wild-type homozygous) was independently associated with CBZ response after adjusting for variables [odds ratio (OR) = 0.389, 95% confidence interval (CI) 0.203-0.743, p = 0.004]. The results of the haplotype and gene interaction case-control analyses of the CBZ response were negative. Our results provide clinical data regarding the genetic possibilities of drug responses related to CAR variation in epilepsy patients.

CONCLUSION

This study is the first to indicate a potentially relevant interaction between the CAR rs2502815 polymorphism and the CBZ response in epilepsy patients.

Development and validation of an innovative UPLC method to quantify lacosamide, oxcarbazepine, and lamotrigine in the serum of children with epilepsy in China

This study has developed and validated a novel UPLC method to quantify lacosamide (LCM), oxcarbazepine (OXC), and lamotrigine (LTG) in children with epilepsy in Xinjiang, China. Phenytoin sodium was used as the internal standard. The mobile phase contained ammonium dihydrogen phosphate solution (10 mmol/L, pH = 4.0) and methanol (55:45, v/v). The flow rate, injection volume, column temperature, and detection wavelength were 0.2 mL/min, 2 μL, 30°C, and 240 nm, respectively. The method was linear within 0.5-40, 2.5-80, and 2.5-40 μg/mL for LCM, 10-hydroxycarbazepine (MHD), and LTG, respectively (r²  ≥ 0.998). The intra- and inter-day precision as measured by the relative standard deviation values was between 1.36 and 4.50, 0.54 and 1.91, and 0.58 and 1.56%. Recovery ranged from 96.58 to 106.22%. All serum samples could be maintained for up to 3 h at ambient temperature, 24 h at 4°C, 30 days at -30°C, and after successive freeze-thaw cycles (24 h per cycle) in the absence of significant degradation.

Lack of Association of Generic Brittle Status with Genetics and Physiologic Measures in Patients with Epilepsy

PURPOSE

A patient was denoted to be generic brittle (GB) if they had a negative opinion about generics (e.g. prior history of a switch problem) or took the innovator brand of their most problematic anti-epileptic drug (AED) when generic was available. The aim of this hypothesis-generating study was to assess possible genetic and physiologic differences between GB and not GB patients with epilepsy.

METHODS

Patients (n = 148) with epilepsy were previously characterized as being either GB or not GB. Blood was collected from each subject for genotyping and physiologic testing. Genotyping for 24 single nucleotide polymorphisms (SNPs) and two copy number variants (CNVs) was performed across 12 genes in each patient. Forty-four physiologic tests were conducted in each patient. Chi square analysis was performed to assess for associations between genotyping results and GB status, as well as between physiologic test results and GB status.

RESULTS

No SNP or CNV discriminated GB status in genetic analysis (genotype or allele frequency). Physiologic test results in this study were not associated with GB status.

CONCLUSIONS

Questions from neurologists and patients about generics is frequently based on applicability of generic drug standards to individual subjects. However, findings here in patients with epilepsy did not uncover genetic or physiologic reasons that explained which patients were GB and which were not GB.

Genetic variations associated with pharmacoresistant epilepsy (Review)

Epilepsy is a common, serious neurological disorder worldwide. Although this disease can be successfully treated in most cases, not all patients respond favorably to medical treatments, which can lead to pharmacoresistant epilepsy. Drug-resistant epilepsy can be caused by a number of mechanisms that may involve environmental and genetic factors, as well as disease- and drug-related factors. In recent years, numerous studies have demonstrated that genetic variation is involved in the drug resistance of epilepsy, especially genetic variations found in drug resistance-related genes, including the voltage-dependent sodium and potassium channels genes, and the metabolizer of endogenous and xenobiotic substances genes. The present review aimed to highlight the genetic variants that are involved in the regulation of drug resistance in epilepsy; a comprehensive understanding of the role of genetic variation in drug resistance will help us develop improved strategies to regulate drug resistance efficiently and determine the pathophysiological processes that underlie this common human neurological disease.