Plasma Concentrations Of Carbamazepine Research Articles

Evaluation of Lipid Emulsion-Mediated Sequestration and Redistribution of the Highly Lipophilic Carbamazepine in the Plasma of Rats

Aim: The idea that intravenous lipid emulsion (ILE) may serve as a "reservoir" for lipophilic drugs has emerged in research as an intravascular "lipid sink" effect. Carbamazepine (CBZ) is a widely used anticonvulsant. This compound has a neutral and highly lipophilic structure and can easily cross body membranes. In this study, our hypothesis focused on the potential efficacy of ILE in modulating blood carbamazepine concentrations. Material and Methods: 22 adult Sprague-Dawley rats were divided into four groups. All groups received CBZ at a dose of 20 mg/kg orogastrically. The first group was the control group. In the second group (activated charcoal group), activated charcoal (AC) was administered orogastrically at a dose of 1 g/kg five minutes after orogastric administration of carbamazepine. The third group (lipid group) received ILE at a dose of 3 ml/kg/min at the fifth minute. The fourth group was the saline group, in which 16 ml/kg of 0.9% NaCl was infused at the fifth minute. Blood samples of 0.5 ml were collected at 0, 4, 8, and 24 hours. Plasma was separated by centrifugation (4000 rpm, 10 minutes) and stored at -80oC for determination of CBZ concentrations. An Agilent 6410B HP-1200 LC series (USA) liquid chromatography system was used for analysis. Quantitative analysis was performed in the multiple reaction mode with electrospray positive ionization (ES+). Results: At the 8th hour of orogastric CBZ administration, CBZ concentration was significantly lower in the activated charcoal group than in the lipid and saline groups (p: 0.021; p: 0.023; p<0.05, respectively). There was no significant difference in CBZ concentrations between the other groups at 8 hours (p>0.05). In the lipid group, the increase in CBZ plasma concentrations was statistically significant at 4 and 8 hours compared to 0 hours (p: 0.005; p: 0.005, respectively). Conclusion: In the lipid group, plasma CBZ concentrations increased at 4 and 8 hours in plasma samples from which lipids were separated by differential centrifugation. In the lipid group, no effects favoring drug-lipid sequestration on the plasma distribution of CBZ were observed.

Physiologically based pharmacokinetic modeling to predict maternal pharmacokinetics and fetal carbamazepine exposure during pregnancy

Carbamazepine is an antiepileptic drug commonly used in pregnant women, during which the physiological changes may affect its efficacy. The aim of this study was to establish a physiologically based pharmacokinetic (PBPK) model of carbamazepine and its active metabolite carbamazepine-10,11-epoxide, and simulate maternal and fetal pharmacokinetic changes of carbamazepine and carbamazepine-10,11-epoxide in different trimesters and propose dose adjustment. We established pregnancy PBPK models for carbamazepine and carbamazepine-10,11-epoxide in PK-Sim® and Mobi® and validated the models with observed data from clinical reports. The placental transfer parameters obtained using different methods were also imported into the model and compared with the observed data to establish and validate fetal pharmacokinetic curves. The simulated results showed that mean steady-state trough plasma concentration of carbamazepine decreased by 27, 43.1, and 52 % during the first, second, and third trimesters, respectively. Therefore, to achieve an optimum therapeutic concentration, administering at least 1.4, 1.8, and 2.1 times the baseline dose of carbamazepine in the first, second, and third trimesters, respectively can be used as a dose reference. In conclusion, this study established and validated a pregnancy PBPK model of carbamazepine and carbamazepine-10,11-epoxide to assess exposure in pregnant women and fetuses, which provided a reference for the dosage adjustment of carbamazepine during pregnancy.

An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure for the quantification of carbamazepine in human serum and plasma.

An isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) was developed and validated to accurately measure serum and plasma concentrations of carbamazepine. Quantitative nuclear magnetic resonance (qNMR) spectroscopy was used to determine the absolute content of the reference material, ensuring its traceability to SI units. The separation of carbamazepine from potential interferences, whether known or unknown, was achieved using a C18 column. A protein precipitation protocol followed by a high dilution step was established for sample preparation. Assay validation and determination of measurement uncertainty were performed in accordance with the guidelines of the Clinical and Laboratory Standards Institute, the International Conference on Harmonization (ICH), and the Guide to the Expression of Uncertainty in Measurement (GUM). In order to demonstrate equivalence to the already existing RMP a method comparison study was performed. The RMP was proven to be highly selective and specific with no evidence of a matrix effect, allowing for quantification of carbamazepine within the range of 0.800-18.0 μg/mL. Intermediate precision and repeatability (n=60 measurements) was found to be <1.6 % and <1.3 % over all concentration levels and independent from the matrix. The relative mean bias ranged from-0.1 to 0.6 % for native serum and from-0.3 to-0.1 % for Li-heparin plasma levels. The measurement uncertainties for single measurements and target value assignment were found to be <1.8 % and <1.3 %, respectively. Method comparison showed a good agreement between the Joint Committee of Traceability in Laboratory Medicine (JCTLM) listed RMP and the candidate RMP resulting in a Passing-Bablok regression equation with a slope of 1.01 and an intercept of-0.01. The bias in the patient cohort was found to be 0.9 %. We present a novel LC-MS/MS-based candidate RMP for carbamazepine in human serum and plasma which provides a traceable and reliable platform for the standardization of routine assays and evaluation of clinically relevant samples.

Comparing real-life carbamazepine exposure between innovator and generic formulation

Carbamazepine is an anticonvulsant largely used in the treatment of epilepsy. The use of generic antiepileptic drugs (AEDs) is controversial because of the eventual possibility to loss seizures control. The aim of our study was to compare the concentration over dose ratio of two products containing carbamazepine, the innovator (Tégrétol®-NOVARTIS) and the generic (Taver®-MEDOCHEMIE). It is a retrospective study (2009-2016) including 32 patients treated with carbamazepine. Patients were treated initially by innovator then switched to generic or vice versa. All patients have at least one level of carbamazepine plasma concentration (C0) with the innovator or the generic formulation. Monitoring of carabamazepine was made using immunoassay method (ARCHITECT-ABOTT®). The mean age of our patients was 28.4 years and ranged from 2 to 55 years. The sex ratio M/F was 1.46. The mean ratio C0/dose for the innovator group was 0.723 (min/max: 0.017/1.73), and the mean ratio C0/dose for the generic group was also 0.607 (min/max: 0.064/1.68). There was no statistically significant difference between both groups (P=0.16). Our results confirm the difference between the innovator and the generic formulation of carbamazepine. So, switching from innovator to generic seems to be safe and exposure to carbamazepine remains the same.

Interchangeability among carbamazepine formulations: the impact over epilepsy patients

The treatment of epilepsy is complex and a matter of concern is the interchangeability among different formulations available for antiepileptic drugs. To evaluate the effects of interchangeability among carbamazepine formulations on patients with epilepsy. This is a prospective cohort study that included adult outpatients diagnosed with epilepsy and under pharmacological treatment with carbamazepine. Before switching the brand/manufacturer, the “Interchangeable Pharmaceutical Product in the Treatment of Epilepsies” questionnaire was applied. The questionnaires “Adverse Events Profile” and Quality of Life in Epilepsy-31, so as the plasma carbamazepine concentrations, were evaluated before and after the brand/ manufacturer switch. Physical-chemical tests aiming to assess tablets quality were performed in accordance with the Brazilian Pharmacopoeia 5th edition. The study population was composed by 14 patients (mean age: 44.6 years), with 10 of females. From those interviewed, 10 had no knowledge about the three antiepileptic drugs formulations available. The frequency of adverse event “problems with skin” incresead (p=0.023) and “upset stomach” decreased (p=0.041) after the changeover. The adverse events profile was associated with only two quality of life domains: “energy/fatigue” (p=0.048) and “total score” (p=0.018). Divergent results between generic and reference formulations were observed in purity-water test (reference: 1.96%, generic: 4.84%) and dissolution test, in which the generic formulation presented 66.27 to 85.77% of carbamazepine dissolved after the third level. Conclusions: Objective differences before and after the brand/manufacturer switch were not observed, in spite of patients’ perceptions. Despite that, more studies in the field are necessary, especially on the interchangeability among generic antiepileptics, in order to better elucidate switching consequences on patients’ life.

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.

ABCB1 c.3435C>T and EPHX1 c.416A>G polymorphisms influence plasma carbamazepine concentration, metabolism, and pharmacoresistance in epileptic patients.

The gene polymorphisms of ABCB1, EPHX1, and SCN1A were found to influence carbamazepine (CBZ) metabolism and resistance in epilepsy patients, but the relevance remains controversial. To reveal the relationships among the gene polymorphisms of ABCB1, EPHX1, SCN1A and the metabolism and resistance of CBZ, the databases of PubMed, EMBASE, Cochrane Library, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals, China Biology medicine disc and Wan Fang were retrieved for suitable studies up to April 2021. 18 studies containing 3293 epilepsy patients were included. The result revealed the gene polymorphism of ABCB1 c.3435C>T is significantly associated with altered concentration-dose ratios of CBZ (CDRCBZ) (CC vs. CT, OR=0.25 (95% CI: 0.08-0.42), P=0.004), and EPHX c.416A>G gene polymorphism may also significantly adjusted the concentration-dose ratios of carbamazepine-10, 11-trans dihydrodiol (CDRCBZD) (AA vs. GG, OR=0.48 (95% CI: 0.01-0.96), P=0.045; AG vs. GG, OR=0.68 (95% CI: 0.16-1.20), P=0.010, respectively) and the ratio of CBZD:carbamazepine-10,11-epoxide (CBZE) (CDRCBZD:CDRCBZE) (AG vs GG, OR=0.83 (95% CI: 0.31-1.36), P=0.002). Furthermore, ABCB1 c.3435C>T polymorphism was also observed to be significantly influenced CBZ resistance (CC vs TT, OR=1.78 (95% CI: 1.17-2.72), P=0.008; CT vs TT, OR=1.60 (95% CI: 1.12-2.30), P=0.01; CC+CT vs TT, OR=1.61 (95% CI: 1.15-2.26), P=0.006, respectively). Therefore, CBZ metabolism and resistance in patients with epilepsy may be adjusted by the gene polymorphisms of ABCB1 c.3435C>T and EPHX1 c.416A>G which provides the further scientific basis for clinical individualized therapy of epilepsy. However, larger sample size studies are still needed to provide further conclusive evidence.

Effects of concurrent and staggered dosing of semi-solid enteral nutrients on pharmacokinetic behavior of antiepileptic drugs after oral administration in rats.

BackgroundThe use of enteral nutrients plays a highly important role in accurate nutrition management, but limited information is currently available on the cautionary points of semi-solid enteral nutrients.AimIn this study, we examined whether the pharmacokinetic profiles of sodium valproate (SVA), levetiracetam (LEV), and carbamazepine (CBZ) are affected by altering the dosing time of RACOL®-NF Semi Solid for Enteral Use (RASS), a prescribed semi-solid formula. We also investigated whether the pharmacokinetic interaction observed in this study can be avoided by staggered dosing of the chemical drug and semi-solid enteral nutrient.MethodsThe plasma concentration of SVA, LEV and CBZ after oral administration was measured by LC-MS/MS method.ResultsThere was no difference in pharmacokinetic characteristics of SVA and LEV when the dosing time of RASS was altered. On the other hand, the plasma concentration of CBZ after oral administration at all sampling points decreased with the extension of the dosing time of RASS, which was consistent with the Cmax and AUC. However, no significant difference was observed in the pharmacokinetic profiles or parameters of CBZ between the short-term and long-term RASS dosing groups by prolonging the administered interval of CBZ and RASS for 2 hr.ConclusionWe concluded that the pharmacokinetic profiles of CBZ, but not SVA and LEV, after its oral administration are affected by the dosing time of RASS, but staggered administration of CBZ and RASS prevented their interaction.

Relevance of NR1I2 variants on carbamazepine therapy in Mexican Mestizos with epilepsy at a tertiary-care hospital.

Aim: We evaluated the potential influence of genetic (CYP3A5, EPHX1, NR1I2, HNF4A, ABCC2, RALBP1, SCN1A, SCN2A and GABRA1) and nongenetic factors on carbamazepine (CBZ) response, adverse drug reactions and CBZ plasma concentrations in 126 MexicanMestizos (MM)with epilepsy. Subjects & methods: Patients were genotyped for 27 variants using TaqMan® assays. Results: CBZ response was associated with NR1I2 variants and lamotrigine cotreatment. CBZ-induced adverse drug reactions were related to antiepileptic polytherapy and SCN1A rs2298771/rs3812718 haplotype. CBZ plasma concentrations were influenced by NR1I2-rs2276707 and -rs3814058, and by phenytoin cotreatment. CBZ daily dose was also influenced by NR1I2-rs3814055 and EPHX1-rs1051740. Conclusion: Interindividual variability in CBZ treatment was partly explained by NR1I2, EPHX1 and SCN1A variants, as well as antiepileptic cotreatment in MMwith epilepsy.

Associations between CYP3A4, CYP3A5 and SCN1A polymorphisms and carbamazepine metabolism in epilepsy: A meta-analysis

Background and objectiveCYP3A4 (rs2242480), CYP3A5 (rs776746) and SCN1A (rs3812718 and rs2298771) gene polymorphisms were previously indicated to be associated with carbamazepine (CBZ) metabolism and resistance in epilepsy. However, previous studies regarding the effects of these polymorphisms still remain controversial. Therefore, we performed a meta-analysis to evaluate whether the four polymorphisms are associated with CBZ metabolism and resistance. MethodsThe PubMed, EMBASE, Cochrane library, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals Database, China Biology Medicine disc and Wan Fang Database were searched up to January 2021 for appropriate studies regarding the association of rs2242480, rs776746, rs3812718 and rs2234922 polymorphisms with CBZ metabolism and resistance. The meta-analysis was conducted by Review Manager 5.3 software. ResultsEighteen studies involving 2546 related epilepsy patients were included. We found that the G allele of CYP3A4 rs2242480 markedly decreased the plasma CBZ concentration in epilepsy. For CYP3A5 rs776746 polymorphism, the GG genotype (homozygote codominant model: GG vs. AA) and GG + GA genotype (dominant model: GG + GA vs. AA and recessive model: GG vs. GA + AA) were respectively found to be significantly associated with increased CBZ plasma concentration. Additionally, it was also found that the SCN1A rs3812718 A allele was significantly associated with decreased CBZ plasma concentration and increased CBZ resistance. However, no association was observed between SCN1A rs2298771 polymorphism and CBZ metabolism and resistance. ConclusionThe CYP3A4 rs2242480, CYP3A5 rs776746 and SCN1A rs3812718 polymorphisms may play important roles in CBZ metabolism and resistance, while SCN1A rs2298771 polymorphism is not associated with CBZ in epilepsy. These findings would improve the individualized therapy of epileptic patients in clinics.

Knowledge of epilepsy among German pharmacists

ProblemPharmacists can have a large impact on attitude, acceptance and adherence in patients with long-term conditions. They should be able to give appropriate advice. MethodsWe invited pharmacists in Mecklenburg-Vorpommern and Saxony, Germany, to complete a questionnaire mainly containing multiple-choice-questions. ResultsOverall, 238 pharmacists took part in the survey. 199 (84%) said they were insecure counselling people with epilepsy or had no experience at all. 205 (86%) rightly assumed a seizure can result in death. Concerning an acute seizure, administration of a rescue medication was considered as possible useful measure by 127 (53%) participants. Of the participants, 206 (87%) stated a physician should be consulted for every first afebrile seizure, 188 (79%) for every first febrile seizure. Exanthema as especially clinically relevant adverse drug event was rightly chosen for carbamazepine by 18 (8%) and for lamotrigine by 12 (5%) participants. 60 (25%) rightly chose liver toxicity for valproate. The increase of carbamazepine plasma concentration when adding erythromycin was chosen by 66 (28%) of pharmacists. 13 (5%) knew about the reduction of effectiveness of lamotrigine when adding hormonal contraceptives. For valproate, 201 (84%) stated that it is important to counsel patients concerning contraception. ConclusionPharmacists are insecure counselling people with epilepsy. Some of them would not suggest to seek medical advice for every first seizure. This can lead to reduced patient safety. The adverse drug events of valproate are well known, important adverse drug events and interactions of other anticonvulsants are less present to the pharmacists and should be regularly addressed in training courses.

Method Validation for the Determination of Carbamazepine in Spiked-saliva Using HPLC-UV for Therapeutic Drug Monitoring Application

Background:: Carbamazepine has been used in the treatment of bipolar disorder, both in acute mania and maintenance therapy, particularly in developing countries. Not only its interaction with various drugs and auto-inducer nature, but the narrow therapeutic range of carbamazepine also makes monitoring necessary to guarantee the adequacy of its safety and therapeutic concentration. To date, the most common biological specimen used for therapeutic drug monitoring (TDM) purposes is still plasma, but saliva can become an alternative biological matrix since its level in saliva strongly correlates with carbamazepine plasma concentration. Objective:: This study validated the bioanalytical method parameters used for carbamazepine in spiked-saliva in accordance with the Food and Drug Administration (FDA) criteria in the Guidance for Industry Bioanalytical Method Validation. Methods: HPLC-UV detector was employed at 285 nm λ with methanol: water: glacial acetic acid (65:34:1) as the mobile phase and C8 as the stationary phase (4.6x150 mm; 5 μm). Results:: The linearity test in a range of 0.0 - 5 μg/mL carbamazepine concentration resulted in a correlation coefficient of 0.999 with 0.20 μg/mL LoD, 0.30 μg/mL LLoQ, and 0.61 μg/mL LoQ. The coefficient of variation and 0iff in the selectivity, accuracy, and precision parameters remained below 20%, indicating fulfillment of the criteria for a bioanalytical method, while the average % recovery was more than 90%. Conclusion:: The currently-developed bioanalytical method has fulfilled the stipulated validation criteria to be used for determining carbamazepine concentration in spiked-saliva as an alternative method for relative bioequivalence studies or TDM application in a clinical setting.

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.

Effects of sinapic acid on hepatic cytochrome P450 3A2, 2C11, and intestinal P-glycoprotein on the pharmacokinetics of oral carbamazepine in rats: Potential food/herb-drug interaction

Dietary supplements, herbal medicines, and other foods may affect the pharmacokinetics and/or pharmacodynamics of carbamazepine (CBZ), which may possibly lead to potential drug–drug/herb–drug interactions, as CBZ has a narrow therapeutic window. Sinapic acid (SA) is a bioactive phytoconstituent used as a dietary supplement for the treatment of epilepsy. This study determined the effects of SA on the pharmacokinetics of CBZ and proposed a possible interaction mechanism in twenty-four male wistar rats (180–210 g). A single CBZ dose (80 mg/kg) was administered orally to rats with or without SA pretreatment (20 mg/kg p.o. per day for 7 days, n = 6). The CBZ concentration in plasma samples was determined by using a sensitive reversed-phase high-performance liquid chromatography assay. The pharmacokinetic parameters were calculated by using non-compartmental analysis. Significance was determined through Dunnett’s multiple comparison test or one-way analysis of variance as appropriate; p < 0.05 were considered significant. The change in the pharmacokinetic parameters (Cmax, Tmax, AUC0-t, AUC0-∞, T½, and kel) of CBZ was evaluated after the administration of CBZ alone or after CBZ co-administration with SA pretreatment. The plasma concentration of CBZ was higher after SA pretreatment than that without pretreatment. The pharmacokinetics of orally administered CBZ were found to be significantly altered (p < 0.05) in rats pretreated with SA compared to those in rats administered CBZ alone. The increases in the Cmax, AUC0−t, T1/2, and MRT of CBZ were 29.79%, 57.18%, 77.18%, and 58.31%, respectively, whereas the kel and apparent oral CL/F were significantly reduced (p < 0.05) in rats pretreated with SA compared to those in rats not pretreated with SA (43.87% and 42.50%, respectively). However, no significant change was observed in the Tmax of CBZ in rats pretreated with SA compared to that in rats that did not receive pretreatment. The enhancement in Cmax, AUC0−t, T1/2, and MRT and the reduction in Kel and CL/F values resulted from the significant inhibition of CYP3 A2, the CYP2C11-mediated metabolism of CBZ in the liver, and the inhibition of intestinal P-glycoprotein/MDR1, which enhanced the rate of CBZ absorption. Further studies are required to determine the clinical relevance of these observations.

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.

Correlations between UGT2B7∗2 gene polymorphisms and plasma concentrations of carbamazepine and valproic acid in epilepsy patients

PurposeThe study aims to detect the polymorphisms in uridine diphosphate glucuronyl transferase (UGT) 2B7∗2 and investigate the corresponding effects on the blood concentrations of valproic acid (VPA) and carbamazepine (CBZ). MethodsA chemiluminescence immunoassay analyzer was used to detect the plasma concentrations of VPA or CBZ in patients. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to analyze UGT2B7∗2 gene polymorphisms. ResultsA total of 117 patients were enrolled under the VPA group, out of which 84 patients were aged 6years or older. Comparison of the blood concentrations of VPA showed significant differences among patients with the three standard genotypes (mutant, heterozygous, and wild-type) based on one-way ANOVA (F=4.386, p=0.016). In addition, comparison of the blood concentrations among the three genotypes in the CBZ group (78 patients) showed no significant differences based on analysis using ANOVA (F=0.897, p=0.412). ConclusionThe UGT2B7∗2 gene polymorphisms significantly affect the standard blood concentrations of VPA, but not CBZ.

DEVELOPMENT AND VALIDATION OF CARBAMAZEPINE PLASMA CONCENTRATIONS MEASUREMENT AND ITS APPLICATION ON EPILEPSY PATIENTS

Objective: To develop and validate high-performance liquid chromatography with photodiode array (HPLC-PDA) detector as a method for measuring carbamazepine plasma concentrations in epilepsy patients treated with monotherapy or polytherapy.Methods: Carbamazepine was extracted from epilepsy patients’ plasma through liquid-liquid extraction, using protein precipitation with chloroform. Analysis was performed using HPLC with Inertsil DS-4 C18 (4.6x150 mm), 5 μm particle size column. The optimal condition for separation was established in a mobile phase consisting of acetonitrile: water (50:50) at a flow rate of 1.0 ml/min, detected by PDA detector at 220 nm. Propylparaben was used as the internal standard. The retention time was 3.5 min.Results: Linearity was obtained over a concentration range of 0.5-16 μg/ml with r = 0.999. The method showed good intra-and inter-day precision and accuracy of more than 90% difference (% diff) and 95% relative standard deviation (RSD). Lower limit of quantification (LOQ) was 0.5 μg/ml and lower limit of detection (LOD) was 0.2 μg/ml with 100% accuracy and more than 90% precision. Recovery test was nearly 100%. Stability of carbamazepine plasma concentration in 3 epilepsy patients was measured on the first and third month of treatment, ranging between 83.5 to 98.7%. When used to compare carbamazepine as a monotherapy versus polytherapy, the method showed good selectivity.Conclusion: The present HPLC method was valid for measuring carbamazepine plasma concentrations in epilepsy patients treated with monotherapy or polytherapy. This method meets the standard in the EMEA guideline in terms of linearity, precision, and accuracy, also selectivity in epilepsy patients treated with polytherapy.

Mass Spectrometric Characterization of Circulating Covalent Protein Adducts Derived from Epoxide Metabolites of Carbamazepine in Patients.

Carbamazepine (CBZ) is an effective antiepileptic drug that has been associated with hypersensitivity reactions. The pathogenesis of those reactions is incompletely understood but is postulated to involve a complex interplay between the drug's metabolism, genetic variation in human leukocyte antigens, and adverse activation of the immune system. Multiple T-cell activation mechanisms have been hypothesized including activation by drug-peptide conjugates derived from proteins haptenated by reactive metabolites. However, definitive evidence of the drug-protein adducts in patients has been lacking. In this study, mass spectrometry was used to characterize protein modifications by microsomally-generated metabolites of CBZ and in patients taking CBZ therapy. CBZ 10,11-epoxide (CBZE), a major electrophilic plasma metabolite of CBZ, formed adducts with glutathione-S-transferase pi (GSTP; Cys47) and human serum albumin (HSA; His146 and His338, but not Cys34) in vitro via notably divergent side-chain selectivity. Both proteins were adducted at the same residues by undefined monoxygenated metabolites ([O]CBZ) when they were incubated with human liver microsomes, NADPH and CBZ. There was also evidence for formation of a CBZ adduct at His146 and His338 of HSA derived via dehydration from an intermediate arene oxide adduct. Glutathione trapping of reactive metabolites confirmed microsomal production of CBZE and indicated simultaneous production of arene oxides. In 15 patients prescribed CBZ therapy, [O]CBZ-modified HSA (His146) was detected in all subjects. The relative amount of adduct was moderately positively correlated with plasma concentrations of CBZ (r2 = 0.44, p = 0.002) and CBZE (r2 = 0.35, p = 0.006). Our results have provided the first chemical evidence for microsomal production of [O]CBZ species that are able to escape the microsomal domain to react covalently with soluble proteins. This study has also demonstrated the presence of circulating [O]CBZ-modified HSA in patients without hypersensitivity reactions who were receiving standard CBZ therapy. The implications of those circulating adducts for susceptibility to CBZ hypersensitivity merit further immunological investigation in hypersensitive patients.

Immediate-release versus controlled-release carbamazepine in the treatment of epilepsy.

Carbamazepine (CBZ) is a commonly used drug for epilepsy that is associated with troublesome adverse events including dizziness, double vision, drowsiness, poor co-ordination and unsteadiness. These adverse events often occur during peaks in drug plasma concentration. These adverse events may limit the daily dose of CBZ that can be tolerated and reduce the chances of seizure control in patients who require high doses. A controlled-release formulation of CBZ delivers the same dose over a longer period of time when compared to a standard immediate-release formulation, thereby reducing post-dose peaks in CBZ plasma concentration and potentially reducing adverse events.This is an updated version of the original Cochrane review published in Issue 12, 2014. To determine the efficacy of immediate-release CBZ (IR CBZ) versus controlled-release CBZ (CR CBZ) in patients diagnosed with epilepsy.The following review questions were investigated.(1) For newly diagnosed patients commencing CBZ, how do IR and CR formulations compare for efficacy and tolerability?(2) For patients on established treatment with IR CBZ but experiencing unacceptable adverse events, what is the effect on seizure control and the tolerability of a switch to a CR formulation versus remaining on the IR formulation? We searched the Cochrane Epilepsy Group Specialized Register, CENTRAL, and MEDLINE (Ovid) from inception to 30 August 2016. Randomised controlled trials comparing IR CBZ to CR CBZ in patients commencing monotherapy and patients presently treated with IR CBZ but experiencing unacceptable adverse events.Primary outcome measures included measures of seizure frequency, incidence of adverse events, proportion of patients with treatment failure and quality of life measures. Two review authors independently assessed trials for inclusion, extracted the data and recorded relevant information on a standardised data extraction form. We used the Cochrane risk of bias tool to assess the methodological quality of included studies.The heterogeneity of the included trials with respect to the reporting of outcomes resulted in only a narrative, descriptive analysis being possible for both the categorical and time-to-event data. Ten trials (296 participants) fulfilled the criteria for inclusion in this review. Only one study had a low risk of bias. Two studies had a high risk of bias and the rest of the studies were rated as unclear risk of bias. One trial included patients with newly diagnosed epilepsy and nine included patients on treatment with IR CBZ.Eight trials reported heterogeneous measures of seizure frequency with conflicting results. A statistically significant difference was observed in only one trial, with patients prescribed CR CBZ experiencing fewer seizures than patients prescribed IR CBZ.Nine trials reported measures of adverse events. There was a trend in favour of CR CBZ with four trials reporting a statistically significant reduction in adverse events compared to IR CBZ. A further two trials reported fewer adverse events with CR CBZ but the reduction was not statistically significant. One trial found no difference in adverse events, and another trial reported more adverse events in the CR CBZ group than the IR CBZ group, although the increase was not statistically significant. For this update no new eligible studies were identified and the conclusions drawn from the initial review remain unchanged.At present, data from trials do not confirm or refute an advantage for CR CBZ over IR CBZ for seizure frequency or adverse events in patients with newly diagnosed epilepsy.For trials involving epilepsy patients already prescribed IR CBZ, no conclusions can be drawn concerning the superiority of CR CBZ with respect to seizure frequency.There is a trend for CR CBZ to be associated with fewer adverse events when compared to IR CBZ. A change to CR CBZ may therefore be a worthwhile strategy in patients with acceptable seizure control on IR CBZ but experiencing unacceptable adverse events. The included trials were of small size and of poor methodological quality limiting the validity of this conclusion.Randomised controlled trials comparing CR CBZ to IR CBZ and using clinically relevant outcomes are required to inform the choice of CBZ preparation for patients with newly diagnosed epilepsy.

Pharmacokinetic interaction of brivaracetam on carbamazepine in adult patients with epilepsy, with and without valproate co-administration

ObjectiveThis Phase I, open-label, dose-escalation study investigated the effects of steady-state brivaracetam on the pharmacokinetics of carbamazepine in patients with epilepsy, with and without valproate co-administration. Valproate and brivaracetam inhibit epoxide hydrolase and increase carbamazepine epoxide levels. MethodsAdult patients with epilepsy being chronically treated with carbamazepine alone (n=9) or with carbamazepine and valproate (n=9) received brivaracetam during successive 1-week periods at doses of 50mg, 100mg, 200mg, and 100mg twice daily (bid). Doses of carbamazepine and valproate must have been stable for at least 3 months. Trough plasma concentrations of carbamazepine, carbamazepine epoxide, and diol metabolites were determined on Days 1, 8, 15, 22, and 29, and at the end of study visit (ESV, 2–3weeks later). ResultsEighteen patients with median (range) age of 45 (20–62) years and body weight of 74 (59–124) kg were enrolled and completed the study. In patients treated with carbamazepine alone, brivaracetam dose-dependently increased mean trough levels of carbamazepine epoxide from 1.38μg/mL on Day 1 pre-dose to 2.16μg/mL (+57%) on Day 8 (50mg bid), 2.72μg/mL (+97%) on Day 15 (100mg bid), 3.02μg/mL (+119%) on Day 22 (200mg bid), 2.67μg/mL (+94%) on Day 29 (100mg bid), and 1.22μg/mL (−12%) at ESV, respectively. In patients on carbamazepine and valproate, carbamazepine epoxide increased from 1.98μg/mL at baseline to 2.72μg/mL (+37%), 3.70μg/mL (+87%), 4.43μg/mL (+124%), 3.11μg/mL (+57%), and 1.94μg/mL (−2%), respectively. There was no trend for change in carbamazepine, carbamazepine diol or valproate levels. Brivaracetam levels increased linearly with dose. Brivaracetam was well tolerated. ConclusionsCarbamazepine epoxide plasma concentrations were approximately doubled by brivaracetam 100 or 200mg bid. Data are consistent with a dose-dependent and reversible inhibition of epoxide hydrolase by brivaracetam. Carbamazepine epoxide was approximately 0.7μg/mL higher in presence of valproate. There is no need to limit brivaracetam dosing when used concomitantly with carbamazepine.