Plasma Levels Of Carbamazepine Research Articles

The association of ABCB1 gene polymorphism with clinical response to carbamazepine monotherapy in patients with epilepsy.

Epilepsy is a common neurological disease but around 30% of patients fail to respond to antiepileptic drug (AED) treatment. Genetic variation of the ATP-binding cassette subfamily B, member 1 (ABCB1) gene, a drug efflux transporter may infer treatment resistance by decreasing gastrointestinal absorption and preventing AED entry into the brain. This study examined the impact of ABCB1 genetic variants on carbamazepine responsiveness. Genomic DNA was extracted from whole blood of 104 epileptic patients. Genotyping of 3 ABCB1 variants (c.C3435T, c.G2677T/A and c.C1236T) was undertaken using validated TaqMan allelic discrimination assays. Plasma carbamazepine levels were measured at 3 and 6months following the initial dose using high-performance liquid chromatography (HPLC) alongside clinical outcomes evaluation. Nonresponse to carbamazepine (CBZ) was associated significantly with the ABCB1 variants c.C3435T, c.G2677T/A, c.C1236T and TTT, TTC haplotypes (P < 0.05). There was no significant association between variants and plasma CBZ level (P > 0.05). Our results showed that variant alleles of the ABCB1 gene and TTT, TTC haplotypes were significantly associated with CBZ resistance without affecting the plasma level of carbamazepine. The findings of this study may help to predict patient's response to treatment ultimately it will improve the personalized and evidence based treatment choice of patients with epilepsy.

Distribution pattern of UGT1A6 and UGT2B7 gene polymorphism and its impact on the pharmacokinetics of valproic acid and carbamazepine: Prospective genetic association study conducted in Pakistani patients with epilepsy

BackgroundEthnic variation is one of the important factors in clinical practice that may affect the pharmacokinetics of drugs. The present study aims to determine the distribution pattern of UGT1A6 and UGT2B7 gene polymorphism and its possible impact on the metabolism of valproic acid (VPA) and carbamazepine (CBZ) in patients with epilepsy from Khyber Pakhtunkhwa region of Pakistan. Methods: After the enrollment of targeted patients, blood was collected for genotype analysis through Sanger sequencing. Plasma concentrations of VPA and CBZ were determined by reversed-phase high-performance liquid chromatography (HPLC) at the follow-up visit of third month from the initiation of therapy. The drug plasma levels were correlated with different genotypes of UGT1A6 and UGT2B7 to determine the impact of genetic polymorphism on the drug metabolism. Results: Of the total 178 epileptic patients, 120 subjects were prescribed VPA monotherapy while 58 subjects were given CBZ monotherapy. The mean age of the subjects was recorded as 26.1 ± 13.5 years with a predominance of the male gender. Generalized tonic-clonic (GTC) was the most prevalent type of seizure (82%) followed by partial seizure. Genotype analysis revealed that the frequency of homozygous and heterozygous variants of the targeted UGT genes were exceptionally high in the Khyber Pakhtunkhwa population compared to the ethnic groups of other countries. In UGT1A6-A552C and UGT1A6-A541G, AC and AG were the most prevalent genotypes with respective frequencies of 43.2% and 41.1% whereas, in UGT2B7-T161C and UGT2B7-G211T, TC and GG were the most prevalent genotypes with respective frequencies of 42.7% and 99.4%. In the VPA-treated group, the homozygous and heterozygous variants of UGT1A6-A552C and UGT1A6-A541G were significantly associated with lower drug plasma concentrations (p < 0.05). However, none of the genotypes of UGT2B7-T161C revealed any significant association with VPA plasma concentration (p greater than 0.05). In the CBZ-treated group, UGT gene polymorphisms were not recognized to cause alteration in the drug plasma concentrations (p greater than 0.05). Conclusion: The genetic polymorphisms of UGT1A6, but not UGT2B7 significantly affected the plasma levels of valproic acid. The chosen SNPs did not reveal a role in determining the plasma levels of carbamazepine.

Cytotoxicity Activity of Graviola Fruit Extract with Carbamazepine and Valproic Acid Show Antagonistic and Indifferent Effects.

Graviola is a tropical fruit with medicinal properties, used for treating various diseases such as inflammation, diabetes, and cancer. Histone deacetylase inhibitors (HDACIs), including carbamazepine (CBZ) and valproic acid (VPA), have been proven strong inhibitors against cancer cell growth. This study investigated the effect of Graviola fruit extract (GFE) on CBZ in healthy rat plasma using high-performance liquid chromatography (HPLC). In addition, the effect of GFE in combination with CBZ and VPA on two human cancer cell lines (PC3 and MCF-7) was explored. The CBZ levels were analyzed using a simple validated HPLC method. The linearity was achieved at a 0.9998 coefficient of determination over a range of 75-5000 ng/mL CBZ. The MTT assay was used to quantify the percentage of viable cells. The maximum plasma concentration (Cmax) and area under the curve (AUC) for CBZ alone were 4,631 ng/mL and 49,225 ng. h/mL, respectively. However, in the presence of GFE, the values reduced significantly to 2,994 ng/mL and 26,587 ng. h/mL, while the p-value was <0.05. The 3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay results for VPA showed a weak cytotoxicity activity on PC3 and MCF-7 cell lines. A simple and validated HPLC method was used to determine CBZ levels in rats' plasma. The plasma CBZ levels (Cmax) were significantly reduced in the presence of GFE, indicating the importance of drug-herb interactions. For in vitro studies, two human cancer cell lines, MCF-7 (breast cancer cells) and PC3 (prostate cancer cells), were used to screen the cytotoxicity activity of GFE, CBZ, and VPA. We observed an antagonism effect for GFE and CBZ combination in both cell lines with FIC values > 4. On the contrary, the combination of GFE and VPA showed an additive or indifferent effect.

Influence of EPHX1 c.337T>C and UGT2B7*2 genetic polymorphisms on the requirement of carbamazepine maintenance dose in persons with epilepsy (PWE) of Southern part of India: a cross-sectional genetic association study.

Carbamazepine (CBZ) is a first-line antiseizure drug used for focal onset seizures. It exhibits inter-individual variability in plasma carbamazepine levels and there are both genetic and non-genetic factors having arole in the requirement of CBZ maintenance dose. The aim was to study the influence of EPHX1 c.337T>C and UGT2B7*2 genetic polymorphisms on CBZ maintenance dose requirement in persons with epilepsy. Persons with epilepsy (PWE) of both gender of age 15-65 years on carbamazepine monotherapy who had been taking same maintenance dose for one year were eligible. Five milliliter of venous blood was collected in 10%EDTA under aseptic precautions. After centrifugation, the cellular component was used for DNA extraction and genotyping. For three genotypes of EPHX1 c.337T>C and UGT2B7*2, the differences in mean carbamazepine dose were analyzed using Analysis of Variance (ANOVA). An unpaired t-test was used to draw a comparison between thegenotypes and CBZ maintenance dose requirement fordominant and recessive models of EPHX1 c.337T>C andUGT2B7*2. A value of p<0.05 was considered to be statistically significant. For UGT2B7*2 (rs 7439366), CT required a higher dose (CT 626mg/day and TT 523mg/day) but not found tobesignificant (p-value 0.167). PWE carrying CT genotypeofEPHX1 c.337T>C had 62mg higher dose when compared to homozygous mutant CC (590mg/day for CT and 528mg/day for CC) but p-value was not found to be significant (p-value 0.835). The results of our study done in 115 PWE showed there was a lack of association between SNPs of EPHX1 c.337T>C, UGT2B7*2 and CBZ maintenance dose requirement in Southern part of India and this finding has tobe confirmed in a larger sample size.

Multidrug Resistance-1 C3435T Polymorphism and Carbamazepine Plasma Level in Indonesian Temporal Lobe Epilepsy Patients.

Temporal lobe epilepsy (TLE) has the highest probability of becoming resistant. One of the causes was Polymorphism in multidrug resistant-1 (MDR1) C3435T. In Dr. Cipto Mangunkusumo Hospital, potential drug-resistant epilepsy prevalence was 84.51%; 66.6% of them used carbamazepine (CBZ) as antiseizure medication. This comparative cross-sectional study aimed to investigate MDR1 C3435T polymorphism and CBZ plasma level (plCBZ) in Indonesian TLE patients. TLE patient was selected consecutively; divided into drug-responsive (DRV) and drugresistant (DRE) groups. Healthy subjects were included as a control for the gene polymorphism comparison. MDR1 was identified using the restriction fragment length polymorphism PCR technique; C allele at 159 and 57bp while T allele at 216bp. High-performance liquid chromatography was used to determine plCBZ. There were 86 subjects; 61 in the study group and 25 controls. The genotype distribution between them was 0.58 vs 0.42, x2=0.54, p=0.000. In the study group, CBZ within therapeutic doses (dCBZ) had outreached the therapeutic plCBZ and found similar in all genotypes. DRE criteria were found in 37 subjects. Distribution of C and T in DRV was 0.63 vs 0.37, x2=10.4; and DRE 0.55 vs 0.45 x2=6.17 (p=0.019). In Tukey's multiple comparison post hoc test, CT in DRV had significantly lower dCBZ (330,36 ± 174,91 mg) and plCBZ (7.15 ± 2.64 mcg/mL) compared to all genotypes in DRE. Whereas mean dCBZ was around 800mg and plCBZ outreached the toxic level; TT was the highest. The genotype MDR1 distribution was similar in the normal population and DRE. Therapeutic plCBZ was achieved using the low dose. CT genotype responds to lower dCBZ, while TT genotype outreached the highest toxic plCBZ.

Genetic polymorphisms of microsomal epoxide hydrolase and UDP-glucuronosyltransferase (UGT) and its effects on plasma carbamazepine levels and metabolic ratio in persons with epilepsy of South India: A cross-sectional genetic association study.

Carbamazepine (CBZ), an anti-seizure drug, is widely prescribed for the management of focal seizures. At a given therapeutic dose, CBZ exhibits marked interindividual variation in the plasma CBZ levels. The aim wasto study the influence of EPHX1 c.337 T>C and UGT2B7*2 genetic polymorphisms on plasma carbamazepine (CBZ) levels in persons with epilepsy (PWE) from South India. 115 PWE belong to South India origin who are on carbamazepine monotherapy were recruited. Genotyping of the two variants weredone using RT-PCR method. PWE who had seizure freedom for one year and their last dose which was not changed for one year duration were included and their plasma levels of CBZ and its active metabolite CBZ 10,11 epoxide were analysed by reverse phase HPLC. In EPHX1 c. 337 (T>C) polymorphism, the PWE carrying CC had lower plasma CBZ levels when compared to CT genotype (2.45 μg/ml vs 3.15 μg/ml. In UGT2B7*2, PWE carrying homozygous mutant TT had higher levels when compared with CT (3.09 μg/ml vs 2.74 μg/ml) genotype but found no statistical significance. Mutant genotype of EPHX1 (CC) had higher metabolic ratio compared to TT genotype (1.33 vs 1.17) but not found to be statistically significant. Mutant genotype of UGT2B7*2 (TT) was found to be having lower metabolic ratio when compared with CC genotype (1.18 vs 1.35; p value =0.08). PWE carrying EPHX1 c.337 T>C (rs1051740) and UGT2B7*2 (rs7439366) genetic polymorphisms did not affect the plasma CBZ levels and metabolic ratio of PWE of South Indian origin. However, this finding should be confirmed in a larger sample size which may help in optimization and personalized CBZ therapy in South Indians.

Liquid Enteral Nutrients Alter the Pharmacokinetics of Orally Administered Carbamazepine in Rats.

The interaction between enteral nutrients (ENs) and drugs co-administered through a nasogastric (NG) tube reportedly affects the absorption and resultant plasma concentrations of the respective drugs. However, the gastrointestinal absorption of carbamazepine (CBZ), an antiepileptic drug, co-administered with liquid ENs through an NG tube has not been clarified. In this study, we measured the recovery rate (%) of CBZ (Tegretol® powder) passed through an NG tube when co-administered with distilled water or ENs (F2α®, Racol® NF, Ensure Liquid®, and Renalen® LP) of different compositions, frequently used in Japan. We also measured the plasma CBZ level in 26 rats after oral co-administration of CBZ with liquid ENs. The CBZ recovery rate was close to 100% in rats of all EN groups after passage through the NG tube. Furthermore, CBZ area under the plasma concentration-time curve from time zero to 9 h (AUC0→9h) of the Ensure liquid® group decreased compared with that of control group (P < 0.05) and Renalen® LP group (P < 0.01). However, the AUC0→9h of CBZ remained unchanged when co-administered with Ensure liquid® 2 h after initial CBZ administration. In conclusion, the co-administration of CBZ with Ensure Liquid® caused a reduction in the absorption of CBZ from the gastrointestinal tract, without adsorption on the NG tube. The administration of Ensure Liquid® 2 h after CBZ is a way to prevent a decrease in plasma CBZ concentration. Our findings suggest that carefully monitoring the plasma levels of CBZ is necessary in co-administation with Ensure liquid® to prevent the unintended effects of the interaction between CBZ and liquid EN.

Detection of Carbamazepine Level among Patients Visiting Psychiatric and Pediatric Services of a Tertiary Hospital in Eastern Nepal

Background: Carbamazepine plasma level is directly related to dose, therapeutic effect, and toxicity. We aimed to observe its plasma level and relationship with dose among psychiatric and pediatric patients.&#x0D; Methods: This observational study was performed in the Therapeutic Drug Monitoring Laboratory of a university hospital for a period of 1.5 years. Twenty-six consenting patients visiting either psychiatric or pediatric service and taking carbamazepine same dose for &gt; 8 days (i.e. &gt; 6 half-lives) were enrolled. The primary outcome was plasma carbamazepine level as determined by a High-Performance Liquid Chromatography machine. The secondary outcome included its correlation with dose assessed by the Spearman rho’s correlation coefficient.&#x0D; Results: The mean dose received by the patients was 13.31 ± 5.39 mg/kg/day in pediatrics and 8.33 ± 2.29 mg/kg/day in psychiatry. The plasma levels [median (IQR)] were 10.01 (6.27, 13.35) mg/L and 10.53 (5.17, 15.19) mg/L respectively in pediatric and psychiatric patients. Thirteen patients (50%) had therapeutic, 10 (36.46%) had above therapeutic, and 3 (11.54%) had subtherapeutic plasma level. Neurocysticercosis (23.1%) in pediatrics and partial seizure (69%) in psychiatry were the most common diagnosis. Symptom-control was achieved in 19 (73.1%) patients. The plasma carbamazepine level did not correlate with dose either in pediatric patients (p = 0.42) or in psychiatry patients (p = 0.63). &#x0D; Conclusion: The plasma carbamazepine levels [median (IQR)] in pediatric and psychiatric patients were 10.01 (6.27, 13.35) mg/L and 10.53 (5.17, 15.19) mg/L respectively. The plasma level was normal in half of the recruited patients and did not correlate with dose.

Herb-drug interaction of gastrodiae rhizoma on carbamazepine: A pharmacokinetic study in rats

ObjectiveGastrodiae Rhizoma (GR), is a traditional Chinese Medicine that has been used for neurological disorders, including epilepsy. Epilepsy patients may be treated with adjunctive therapy of GR with antiepileptic drugs (AEDs). In particular, carbamazepine (CBZ) is of high potential to interact with concurrent treatment of Chinese Medicine. This study was to investigate the herb-drug interactions of GR and CBZ, an AED, through pharmacokinetic approach in rats. MethodsWe adopted a high-performance liquid chromatography (HPLC) system to quantify the plasma level of CBZ and its metabolite (carbamazepine-10, 11-epoxide, CBZE). The method was validated as per instructions under United States Food and Drug Administration (USFDA) guidance. For the herb-drug interaction study, rats were randomly divided into four different treatment groups: single-dose CBZ treatment, single-dose CBZ/GR treatment, 2-week course of CBZ treatment and 2-week course of CBZ/GR treatment. ResultsOur results demonstrated the auto-induction of CBZ metabolization when comparing single-dose with 2-week course of CBZ treatment. Pharmacokinetic interactions were noted in concomitant use of GR with CBZ by comparing two single-dose treatments (CBZ versus CBZ/GR). Our data showed that GR increased the mean residence time (MRT0-t) and the time taken to reach the maximum concentration (Tmax) of CBZ in single-dose of CBZ/GR treatment. The maximum drug concentration (Cmax) of CBZ was reduced in single-dose CBZ/GR treatment. When comparing the 2-week course of CBZ treatment with the 2-week course of CBZ/GR treatment, the MRT0-t and half-life of CBZ were increased. The AUC0-t, the Cmax and the half-life of CBZE were increased. ConclusionCBZ/GR treatment may reduce the auto-induction of CBZ over 2 weeks. While the reduction of auto-induction could enhance the therapeutic effects of CBZ, it could also lead to an increase in neurological side effects and non-neurological adverse effects. Our results provided preclinical evidence of herb-drug interaction, which may have implications for epilepsy patients treated with GR.

Factors Influencing Plasma Concentrations of Phenytoin, Phenobarbitone, Carbamazepine and Sodium Valproate in Epileptic Patients Attending a Tertiary Care Hospital

Objective: The traditional anti-epileptic drugs like phenytoin, sodium valproate and carbamazepine continue to be used widely in the low to middle income countries due to their time tested efficacy and low costs. The factors which affect the AED concentrations in non-toxicity indications has not been reported so far. Hence, we studied the factors that could influence the plasma concentrations of these AEDs. Methods: This is a retrospective record based study and a short term prosepective study. Requisition forms of epileptic patients referred for TDM 2012-2014 were compared with the AED concentrations reported. Epileptic patients who were referred during May-June 2015 for TDM were evaluated for their seizure history and anthropometic measurements for calculation of extracellular volume (VECW) and compared with the AED concentrations. Results: Out of the 170 requisitions for TDM, 68.2% were monotherapy and 31.8% received two or more antiepileptic drugs. In 44% of patients, the plasma concentrations of the AED correlated with clinical response. In our study the plasma level of carbamazepine was found to be reduced by phenytoin, sodium valproate concentration was reduced by carbamazepine and phenytoin levels were reduced by sodium valproate. In male, phenytoin levels were significantly lower than in female, Phenytoin decreased carbamazepine levels significantly in female. Carbamazepine significantly decreased sodium valproate concentrations in females. Carbamazepine dose adjusted for weight and VECW was found to show a trend of correlation to the blood levels, Conclusion: TDM for AEDs is an indispensable investigation that guides the clinicians to tailor dose of drugs in individual patients. Factors such as age, gender, concomitant drugs in general and VECW in patients on carbamazepine needs to be considered while interpreting AED plasma concentrations for monitoring therapy.

Influence of cytochrome P450 3A5 (CYP3A5) genetic polymorphism on dose-adjusted plasma levels of carbamazepine in epileptic patients in South Indian population.

AIM:The aim of the study was to compare the dose-adjusted plasma levels of carbamazepine (CBZ) among expressers and nonexpressers of cytochrome P450 3A5 (CYP3A5)* 3 genotypes.SUBJECTS AND METHODS:The study was carried out in 100 epileptic patients who were on CBZ monotherapy. Steady-state plasma CBZ levels were measured using reverse-phase high-performance liquid chromatography method, and genotyping of CYP3A5 was done using real-time polymerase chain reaction method.RESULTS:Patients inheriting CYP3A5*3/*3 variant (nonexpressers) had an increased plasma concentration of CBZ (4.86 μg/ml) when compared to patients inheriting either CYP3A5*1/*1 or CYP3A5*1/*3 (expressers) (4.3 μg/ml, P = 0.004). Nonexpressers had significantly increased plasma concentrations of CBZ when adjusted for dose and weight when compared to expressers (P < 0.002 and P < 0.001, respectively). The frequency of adverse reactions in expressers and nonexpressers was 12% and 9%, respectively.CONCLUSION:There is a significant influence of CYP3A5*3 genetic polymorphism (6986A>G) on dose-adjusted plasma levels of CBZ in epileptic patients in the South Indian population.

Epilepsy control with carbamazepine monotherapy from a genetic perspective

BackgroundEthnicity variation is one of the main factors that may affect drug response in clinical practice. As MTHFR gene affects different transcriptome and proteome which affect the clinical response of drugs. Purpose of the current study was to observe possible variations in plasma levels of carbamazepine monotherapy and seizures’ control in Pakhtun population of Khyber Pakhtunkhwa (KP) in the context of MTHFR (C677T and A1298C) gene polymorphisms.MethodsBlood was collected from the epileptic patients treated with carbamazepine monotherapy for the first time following respective oral doses on its steady state concentration after 3 h of morning dose at 3rd and 6th month of the therapy. Plasma carbamazepine levels were determined using reverse phase high performance liquid chromatography after method validation. MTHFR (C677T, AA298C) gene was genotyped. Patients were followed on 3rd and 6th month of the therapy for monitoring of response to carbamazepine therapy.ResultsFollowing for 3rd and 6th month of duration of carbamazepine therapy, poor seizure controlled patients were more likely noticed in heterozygous variants (677CT and 1298 AC) of MTHFR gene (P < 0.05). There was no significant (P > 0.05) difference in the dose and plasma level of carbamazepine among different genotypes of MTHFR (C677T and A1298C) gene. Similarly, the difference in dose and plasma level of carbamazepine was not significant (P > 0.05) in the responder and non-responder people with epilepsy.ConclusionOur study suggests that heterozygous variants of MTHFR (C677T and A1298C) gene are associated with poor seizure control in Pakhtun population of KP despite the fact that plasma level of carbamazepine were found within the therapeutic range.

The possible effect of SCN1A and SCN2A genetic variants on carbamazepine response among Khyber Pakhtunkhwa epileptic patients, Pakistan.

PurposeSCN1A (3184 A>G) and SCN2A (56G>A) gene encodes α subunit of the neuronal voltage-gated sodium channel, which is a target for carbamazepine (CBZ). Recent studies have demonstrated that polymorphism of SCN1A (3184 A>G) and SCN2A (56G>A) was associated with use of CBZ. However, it has not been determined whether the polymorphism affects CBZ or other antiepileptic drug responsiveness. The aim of the study was to establish whether the SCN1A (3184 A>G) and SCN2A (56G>A) polymorphisms of the SCN1A and SCN2A genes affect responsiveness to CBZ.MethodsSCN1A (3184 A>G) and SCN2A (56G>A) gene polymorphisms were genotyped in 93 Khyber Pakhtunkhwa epileptic patients treated with CBZ. The association between CBZ responsiveness and the polymorphism was estimated by adjusting for clinical factors affecting the outcome of therapy. The number of seizure episodes was documented at baseline, and the therapy of each of the 93 patients was followed up. The plasma level of CBZ was determined using reverse-phase high-performance liquid chromatography. SCN1A and SCN2A genes were genotyped using RFLP. Data were analyzed using Graph Pad Prism 6.ResultsMean age of the patients was 18.6±9.3 at the 3rd month and 18.7±9.5 at the 6th month. The baseline dose of CBZ was 468±19.8 mg/d and titrated at the rate of 48±1.4 and 4.0±0.2 mg/d. The difference in plasma level of CBZ was significant (P=0.004) between 3rd and 6th month among different genotypes of SCN1A gene in nonresponder and responder patients. At the 3rd month of the therapy, the poor responders were more likely (P=0.003 and P=0.01) to have variants (3184AG and 3184GG) of SCN1A gene. Similarly, poor responsders were more likely (P=0.0007 and P=0.001) to have variant genotypes (56GA, 56AA) of SCN2A gene at the 3rd month of the therapy.ConclusionThis study demonstrated a significant association between the SCN1A (3184 AG and GG) and SCN2A (56GA and AA) genotype with CBZ-nonresponsive epilepsy.

Quinine and carbenoxolone enhance the anticonvulsant activity of some classical antiepileptic drugs

ObjectiveQuinine (QUIN) and carbenoxolone (CNX) elicit anticonvulsant effects typically characterized by the reduction of the epileptiform activity as well as changes in behavioral parameters related to seizures. Therefore, the aim of this study was to analyze the effects of these molecules on the anticonvulsant activity of some classical antiepileptic drugs.MethodsMale Wistar rats were used. Valproate (VPA), phenytoin (PHT), or carbamazepine (CBZ) was administered at sub-therapeutic doses for intraperitoneal via. Subsequently, animals were administered with a single dose of QUIN or CNX. The anticonvulsant activity was evaluated with the maximal electroshock (MES) test and pentylenetetrazole (PTZ) administration. Additionally, the plasma levels of CBZ were determined using an HPLC method.ResultsAll the control rats presented generalized tonic–clonic seizures after the MES test or the administration of PTZ. For the MES test, all of the antiepileptic drugs increased their anticonvulsant activity when were co-administered with QUIN. For the PTZ test, only the combination CBZ plus QUIN significantly increased the percentage of protection against the generalized tonic–clonic seizures. The co-administration of CBZ plus QUIN resulted in an augmented concentration of CBZ in plasma.DiscussionThe present study shows that QUIN and CNX enhance the anticonvulsant activity of some classical antiepileptic drugs. However, only the combination CBZ/QUIN had significant effects on both MES and PTZ models. Such anticonvulsant activity could be attributed to increased levels of CBZ in plasma. We propose that these molecules could improve the pharmacological actions of antiepileptic drugs administered at sub-therapeutic doses.

Measurement and Comparison of Carbamazepine Plasma Levels for Assessment of Compliance, Safety and Toxicity

Carbamazepine is one of the most frequently prescribed antiepileptic drugs and influence of genetic differences, sex, age and race on the plasma levels of carbamazepine and its metabolites is well known. The objective of this study was to assess and compare the compliance, safety and toxicity in different age and gender groups of Chinese epileptic patients on the basis of therapeutic drug monitoring results of carbamazepine, since Han-Chinese are at higher risk of developing serious and fatal adverse effects when exposed to carbamazepine. The therapeutic drug monitoring results of carbamazepine in epileptic patients, obtained with validated methods were complied, evaluated and compared for compliance, safety and toxicity in different age and gender groups of Chinese epileptic patients. The therapeutic drug monitoring results of males and females were separately compiled and thereafter each gender group was further divided into children, adults and elderly as different age group. All age groups in both gender groups were evaluated for therapeutic, sub-therapeutic and toxic ranges. It was found that 45% of samples of total samples had sub-therapeutic levels and 55% of all samples had carbamazepine levels in therapeutic range, and none of gender and age group found in toxic range. Compared to males, female samples were more in number of sub-therapeutic levels. Populations of children males and children females were having more samples in sub-therapeutic levels as compared to adult and elderly males and females, respectively. However, it needs further evaluation. The findings of present study revealed that majority of patients were in sub- therapeutic levels. It is suggested that regularly therapeutic drug monitoring of carbamazepine should be performed and dose of carbamazepine in epileptic patients should be adjusted only after therapeutic drug monitoring results in order to assess the compliance, optimize the efficacy, safety and minimize the toxicity.

SCN1A and SCN1B gene polymorphisms and their association with plasma concentrations of carbamazepine and carbamazepine 10, 11 epoxide in Iranian epileptic patients.

From a genetic point of view, epilepsy is a polygenic multifactorial syndrome. The SCN1A and B genes belong to a family of genes that provide instructions for making sodium channels. Understanding the relevance of SCN1A and SCN1B gene polymorphisms to plasma concentration of carbamazepine (CBZ) and 'its active metabolite carbamazepine 10, 11 epoxide (CBZE), may shed more light on inter-individual variations in response to CBZ. In this cross-sectional study, genotype distribution and allele frequency of six non-synonymous exonic single nucleotide polymorphisms (SNPs) of the SCN1A and B genes were selected and determined using PCR-RFLP in 70 epileptic patients treated with CBZ for at least 6 months. The patients had no hepatic or renal diseases and received no medications known to have a major interaction with CBZ. Serum concentrations of CBZ and CBZE were measured using High-Performance Liquid Chromatography (HPLC). The AA, AG and GG alleles of SCN1A were found in 23, 37 and 10 patients, respectively. There were no statistically significant differences in the mean (± standard deviation) of plasma concentrations of CBZ (P=0.8) and CBZE (P=0.1) among these 3 groups. Likewise, there was no statistically significant relationship between SCN1A polymorphisms and CBZ concentration/dose ratio (P=0.7). A significant association was found between CBZ plasma level and CBZ concentration/dose with CBZ daily dose. All patients had the same genotype of SCN1B gene(CC). and no statistical analysis was performed. No significant association between SCN1A gene polymorphisms and plasma levels of CBZ and CBZE were found[u1].

Oxidative Status in Epileptic Children Using Carbamazepine.

Background:There is an increasing attention towards the relationship between oxidative stress and epilepsy. The effect of antiepileptic drugs on oxidant status is of major interest. Antiepileptic drugs can increase levels of free radicals, which consequently might lead to seizures. Carbamazepine (CBZ) is an antiepileptic drug commonly used in childhood and adolescence.Objectives:Therefore we aimed to investigate the effects of CBZ on total antioxidant status, total oxidant stress, and oxidative stress index.Patients and Methods:The study included 40 epileptic patients and 31 healthy children between 4 and 12 years of age. Serum CBZ level, total antioxidant capacity and total oxidant status were measured. Oxidative stress index was also calculated both in controls and patients.Results:In the epileptic group, decreased levels of total antioxidant capacity, increased total oxidative stress and oxidative stress index levels were found. Positive correlation between plasma CBZ levels and total oxidant status was observed.Conclusions:Antioxidant action could not be playing any role in antiepileptic effect of CBZ. Furthermore, increased oxidative stress induced by CBZ could be the cause of CBZ-induced seizures. Therefore combining CBZ with antioxidants could be beneficial.

Polymorphic Variants of SCN1A and EPHX1 Influence Plasma Carbamazepine Concentration, Metabolism and Pharmacoresistance in a Population of Kosovar Albanian Epileptic Patients.

AimThe present study aimed to evaluate the effects of gene variants in key genes influencing pharmacokinetic and pharmacodynamic of carbamazepine (CBZ) on the response in patients with epilepsy.Materials & MethodsFive SNPs in two candidate genes influencing CBZ transport and metabolism, namely ABCB1 or EPHX1, and CBZ response SCN1A (sodium channel) were genotyped in 145 epileptic patients treated with CBZ as monotherapy and 100 age and sex matched healthy controls. Plasma concentrations of CBZ, carbamazepine-10,11-epoxide (CBZE) and carbamazepine-10,11-trans dihydrodiol (CBZD) were determined by HPLC-UV-DAD and adjusted for CBZ dosage/kg of body weight.ResultsThe presence of the SCN1A IVS5-91G>A variant allele is associated with increased epilepsy susceptibility. Furthermore, carriers of the SCN1A IVS5-91G>A variant or of EPHX1 c.337T>C variant presented significantly lower levels of plasma CBZ compared to carriers of the common alleles (0.71±0.28 vs 1.11±0.69 μg/mL per mg/Kg for SCN1A IVS5-91 AA vs GG and 0.76±0.16 vs 0.94±0.49 μg/mL per mg/Kg for EPHX1 c.337 CC vs TT; P<0.05 for both). Carriers of the EPHX1 c.416A>G showed a reduced microsomal epoxide hydrolase activity as reflected by a significantly decreased ratio of CBZD to CBZ (0.13±0.08 to 0.26±0.17, p<0.05) also of CBZD to CBZE (1.74±1.06 to 3.08±2.90; P<0.05) and CDRCBZD (0.13±0.08 vs 0.24±0.19 μg/mL per mg/Kg; P<0.05). ABCB1 3455C>T SNP and SCN1A 3148A>G variants were not associated with significant changes in CBZ pharmacokinetic. Patients resistant to CBZ treatment showed increased dosage of CBZ (657±285 vs 489±231 mg/day; P<0.001) but also increased plasma levels of CBZ (9.84±4.37 vs 7.41±3.43 μg/mL; P<0.001) compared to patients responsive to CBZ treatment. CBZ resistance was not related to any of the SNPs investigated.ConclusionsThe SCN1A IVS5-91G>A SNP is associated with susceptibility to epilepsy. SNPs in EPHX1 gene are influencing CBZ metabolism and disposition. CBZ plasma levels are not an indicator of resistance to the therapy.

P14 – 2314: Carbamazepine overdosage despite low residual plasma concentration?

Introduction Carbamazepine (CBZ) is an anti-epileptic drug and the rapid-release oral suspension (OS) is regularly used in the pediatric population. Case description We present a 4.5-year-old boy with temporal epilepsy since the age of 12 months. Treatment by valproic acid was inefficient, and levetiracetam was complicated by behavioral troubles. Therefore, CBZ OS twice a day was introduced. After 8 months without seizures despite low residual plasma dosage of 2.3 mg/l (normal 4–10 mg/l), seizures reappeared and treatment dose was increased. Nevertheless, after increase to 15 mg/kg/day with plasma level Discussion The patient described in this case report presented partial seizures controlled by extended-release CBZ. Despite high-dose CBZ the patient had a residual plasma level in the lower therapeutic range suggesting rapid metabolism. In addition, the patient experienced symptoms of CBZ overdosage 2 hours after administration of rapid-release oral suspension, but not with CBZ tablets, and despite infratherapeutic basal plasma level, compatible with the hypothesis of very rapid metabolism. Indeed, peak CBZ plasma concentrations are observed 2 hours after the administration of oral suspension, 12 hours after tablets and 24 hours after extended-release CBZ tablets. Conclusion In contrast to CBZ oral solution, CBZ tablets at the same dose might be efficient for seizure control. In addition, symptoms of CBZ overdosage might be observed despite low residual CBZ plasma level during OS treatment as the consequence of very rapid metabolisation. Nevertheless, there is currently no extended-release formulation available for small children and patients with swallow difficulties.

Relationships between pharmacokinetic parameters of carbamazepine and therapeutic response in patients with bipolar disease.

This study aimed to assess the relationship between plasma levels of carbamazepine and its active metabolite 10,11-epoxide-carbamazepine, and the therapeutic response in patients with bipolar disease. Thirteen patients were kept on a fixed individual dose of carbamazepine for 19 weeks under psychiatric care. Steady-state plasma concentrations of carbamazepine and its metabolite 10,11-epoxide-carbamazepine were measured at weeks 4, 12, and 20 by HPLC essay. Simultaneously, the psychopathologic state was assessed using the Brief Psychiatric rating scale (BPRS). Upon correlational analysis, mean BPRS scores did not correlate with the plasma levels of carbamazepine, whereas both mean plasma levels of 10, 11-epoxide-carbamazepine concentrations and 10,11-epoxide-carbamazepine to plasma carbamazepine ratio were closely correlated with mean values of BPRS scores (r = 0.80, p =10(-4), r= -0.89, p =10(-3) respectively). Optimum therapeutic response was observed among patients who had a plasma metabolite level of 1.4 μg/mL and a plasma carbamazepine concentrations of 7 μg/mL simultaneously. These results suggest that both plasma carbamazepine and 10,11-epoxide-carbamazepine levels must be fixed to achieve optimum therapeutic response. In order to reach these conditions, inhibitor drugs (such as valproic acid) or inductor drugs (such as phenobarbital) of epoxyde-hydrolase might be coadministered with the carbamazepine in order to adapt the plasma level of 10,11-epoxide-carbamazepine.