Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring

Role of Chalcogenides in Sensitive Therapeutic Drug Monitoring Using Laser Desorption and Ionization

This study investigates the applicability of six transition metal dichalcogenides to efficient therapeutic drug monitoring of ten antiepileptic drugs using laser desorption/ionization-mass spectrometry. We found that molybdenum ditelluride and tungsten ditelluride are suitable for the sensitive quantification of therapeutic drugs. The contribution of tellurium to the enhanced efficiency of laser desorption ionization was validated through theoretical calculations utilizing an integrated model that incorporates transition-metal dichalcogenides and antiepileptic drugs. The results of our theoretical calculations suggest that the relatively low surface electron density for the tellurium-containing transition metal dichalcogenides induces stronger Coulombic interactions, which results in enhanced laser desorption and ionization efficiency. To demonstrate applicability, up to 120 patient samples were analyzed to determine drug concentrations, and the results were compared with those of immunoassay and liquid chromatography-tandem mass spectrometry. Agreements among these methods were statistically evaluated using the Passing-Bablok regression and Bland-Altman analysis. Furthermore, our method has been shown to be applicable to the simultaneous detection and multiplexed quantification of antiepileptic drugs.

Bioequivalence Study of Two Tablet Formulations of Clonazepam 2 mg: A Randomized, Open-Label, Crossover Study in Healthy Mexican Volunteers Under Fasting Conditions

INTRODUCTION

The prevalence of neurological disorders is high among the Mexican population. Clonazepam is primarily indicated to treat panic disorders, certain kinds of epilepsy such as status epilepticus, childhood motor seizures (petit mal absence, Lennox-Gastaut syndrome, and infantile spasms), anxiety, and muscle spasm. This study was performed to compare bioequivalence between two oral tablet formulations of clonazepam 2 mg in healthy Mexican volunteers under fasting conditions.

METHODS

This phase I, randomized, open-label, two-treatment, crossover study included 30 healthy volunteers. Subjects were randomly assigned to either test or reference formulation of clonazepam 2 mg. Each study period was separated by 21-day washout period. Blood samples were collected at pre-dose and up to 72 h after drug administration. Clonazepam concentrations were determined using a validated ultra-flow liquid chromatography-tandem mass spectrometric method. Pharmacokinetic parameters were determined using a non-compartmental method. Two formulations were considered bioequivalent if geometric mean ratios (test/reference) were between 80% and 125%. Safety was evaluated by recording adverse events.

RESULTS

Pharmacokinetic parameters were comparable between test and reference formulations. The mean maximum plasma concentration (Cmax) was ≈ 13 ng/mL, area under the plasma concentration-time curve from time 0 to last measurable concentration (AUC0-t) was ≈ 360 ng h/mL, time to reach maximum plasma concentration (Tmax) was ≈ 3 h, and elimination half-life (t1/2) was ≈ 43 h. Geometric mean ratios (90% confidence interval) of Cmax (99.2-115.3%), AUC0-t (100.6-110.6%), and AUC0-∞ (98.5-111.6%) were within the bioequivalence range. Seven non-serious adverse events (mostly asymptomatic hypotension) were recorded.

CONCLUSION

The test and reference formulations of clonazepam 2 mg were bioequivalent and well tolerated in healthy Mexican volunteers under fasting conditions.

PROTOCOL AUTHORIZATION NUMBER

213301410B0051 (Approved on April 13, 2021).

Preparation of a New Solid-Phase Microextraction Fiber Based on Molecularly Imprinted Polymers for Monitoring of Phenobarbital in Urine Samples

A simple solid-phase microextraction technique using molecularly imprinted polymers (MIP-SPME) was prepared to monitor phenobarbital in urine samples. In this technique, the fiber was prepared via insertion of the modified stainless-steel wire in the reaction solution including 3-aminopropyltriethoxysilane and tetraethyl orthosilicate in the presence of an acidic catalyst (acetic acid). The fabricated MIP-SPME fiber was utilized to selectively extract phenobarbital from urine samples and prepare it for detection through high-performance liquid chromatography with ultraviolet detection. The synthesized MIPs were characterized by several techniques such as Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and thermal gravimetric analysis. The effects of various influencing factors on the extraction yield of phenobarbital were considered and optimized. The conditions that yielded the maximum extraction efficiency were as follows: pH of 5, 25 min extraction time, 500 rpm stirring rate, 15 min desorption time and using methanol as elution solvent. Within the range of concentrations of 0.02 to 100 μg mL-1, the method had linear characteristics, with a suitable coefficient of determination (0.9983). We determined limits of detection and limits of quantification to be 9.88 and 32.9 ng mL-1, respectively. The repeatability and reproducibility of the prepared fibers were 4.6 and 6.5%, respectively.

Functionalized monolithic columns: Recent advancements and their applications for high-efficiency separation and enrichment in food and medicine

The chromatographic column is the core of a high-performance liquid chromatography (HPLC) system, and must have excellent separation efficiency and selectivity. Therefore, functional modification materials for monolithic columns have been rapidly developed. This study is a systematic review of the recently reported functionalized monolithic columns. In particular, the study reviews the types of functional monomers under different modification conditions, as well as the separation and detection techniques combined with chromatography, and their development prospects. In addition, the applications of functionalized monolithic columns in food analysis, biomedicine, and the analysis of active ingredient of Chinese herbal medicines in recent years are also discussed. Also reviewed are the functionalized monolithic columns for qualitative and quantitative analysis. It provided a reference for further development and application of organic polymer monolithic columns.

Electromembrane extraction of tramadol from exhaled breath condensate and its liquid chromatographic analysis

Tramadol has extracted from the exhaled breath condensate (EBC) samples through the supported liquid membrane consisting of 2-nitrophenyl octyl ether impregnated in the hollow fiber wall, and the lumen of the hollow fiber was filled with 20 μL of an acceptor phase. Under the optimum conditions of the electromembrane extraction, i.e. the stirring speed of 750 rpm, extraction time of 20 min, acceptor pH at 1.0, donor phase pH at 6.0, and an applied voltage of 170 V across the supported liquid membrane, a preconcentration factor of 128-fold with a extraction recovery of 64% was achieved. Acceptable linearity was obtained in the tramadol concentration range of 5-1000 ng mL^-1 (R² = 0.9999) with a limit of detection of 1.5 ng mL^-1 and a limit of quantitation of 5 ng mL^-1. The relative standard deviations for the intra-day and inter-day replications were obtained between 0.4% and 2.5%. The validated technique was successfully used to determine tramadol in real EBC samples.

Intranasal delivery of phenytoin-loaded nanoparticles to the brain suppresses pentylenetetrazol-induced generalized tonic clonic seizures in an epilepsy mouse model

In this work we describe the preparation and characterization of lecithin-chitosan nanoparticles (L₁₀C_i⁺), and investigate their ability to deliver the anti-epileptic drug phenytoin (PHT) to mouse brain following intranasal (IN) administration. L₁₀C_i⁺ were retained in the nasal cavity compared to PHT in PEG200 solution (PHT/PEG), which suffered immediate nasal drainage. PHT was detected in the brain after 5 min of IN administration reaching a maximum of 11.84 ± 2.31 %ID g^-1 after 48 hours. L₁₀C_i⁺ were associated with a higher brain/plasma ratio (C_b/p) compared to the experimental control comprising free PHT injected via the intraperitoneal route (PHT-IP) across all tested time points. Additionally, L₁₀C_i⁺ led to lower PHT accumulation in the liver and spleen compared to PHT-IP, which is vital for lowering the systemic side effects of PHT. The relatively high drug targeting efficiency (DTE%) of 315.46% and the drug targeting percentage (DTP%) of 68.29%, combined with the increasing anterior-to-posterior gradient of PHT in the brain confirmed the direct nose-to-brain transport of PHT from L₁₀C_i⁺. Electroencephalogram (EEG) analysis was used to monitor seizure progression. L₁₀C_i⁺ resulted in a complete seizure suppression after 4 hours of administration, and this inhibition persisted even with an 8-fold reduction of the encapsulated dose compared to the required PHT-IP dose to achieve a similar inhibitory effect due to systemic loss. The presented findings confirm the possibility of using L₁₀C_i⁺ as a non-invasive delivery system of PHT for the management of epilepsy using reduced doses of PHT.

Pharmacokinetic Drug-Drug Interactions among Antiepileptic Drugs, Including CBD, Drugs Used to Treat COVID-19 and Nutrients

Anti-epileptic drugs (AEDs) are an important group of drugs of several generations, ranging from the oldest phenobarbital (1912) to the most recent cenobamate (2019). Cannabidiol (CBD) is increasingly used to treat epilepsy. The outbreak of the SARS-CoV-2 pandemic in 2019 created new challenges in the effective treatment of epilepsy in COVID-19 patients. The purpose of this review is to present data from the last few years on drug–drug interactions among of AEDs, as well as AEDs with other drugs, nutrients and food. Literature data was collected mainly in PubMed, as well as google base. The most important pharmacokinetic parameters of the chosen 29 AEDs, mechanism of action and clinical application, as well as their biotransformation, are presented. We pay a special attention to the new potential interactions of the applied first-generation AEDs (carbamazepine, oxcarbazepine, phenytoin, phenobarbital and primidone), on decreased concentration of some medications (atazanavir and remdesivir), or their compositions (darunavir/cobicistat and lopinavir/ritonavir) used in the treatment of COVID-19 patients. CBD interactions with AEDs are clearly defined. In addition, nutrients, as well as diet, cause changes in pharmacokinetics of some AEDs. The understanding of the pharmacokinetic interactions of the AEDs seems to be important in effective management of epilepsy.

Ultrasound-assisted electromembrane extraction of clonazepam from plasma and determination using capillary electrophoresis

In this work, ultrasound-assisted electromembrane extraction (UA-EME) coupled with capillary electrophoresis (CE) and diode array detection (DAD) was developed for the determination of clonazepam from plasma samples. A comparative study was carried out between conventional EME and UA-EME methods to investigate the influence of the ultrasound waves on the extraction efficiency. The central composite design was used for the optimization of the variables affecting these methods to achieve the best extraction efficiency. Under optimal extraction conditions, the UA-EME provided better extraction recovery in a shorter time (58% in 13 min) than the EME method (42% in 30 min). Ultrasound reduces the extraction time and increased recovery by reducing the thickness of the barrier layer. In addition, this method provided a higher pre-concentration factor (203) and a lower limit of detection (3 ng mL^-1) with good repeatability (RSDs were less than 10.11%).

High performance liquid chromatography: A versatile tool for assaying antiepileptic drugs in biological matrices

Epilepsy is a recurrent long-term illness occurring in approximately 1.0% of the world's population. There are currently about 29 approved antiepileptic drugs for the management of epilepsy. Due to narrow therapeutic indices of most antiepileptic drugs, clinical pharmacokinetic characteristics and therapeutic drug monitoring of these drugs are imperative. The objectives of this review were to identify common chromatographic principles, requirements and/or conditions for high-performance liquid chromatography as applied to assay of antiepileptic drugs in biological matrices. The review was conducted using 66 peer reviewed articles (1990 to 2020) from 29 journals that were sought via PubMed, Science Direct and Google Scholar. In all, 29 antiepileptic drugs were assayed from 6 different biological matrices. Forty-three of the reviewed articles estimated the concentration of only one antiepileptic drug, whilst 23 articles focused on simultaneous determination of two or more antiepileptic drugs. Thirty-four, 20, and 14 articles reported using liquid-liquid extraction, protein precipitation, or solid phase extraction for sample clean up, respectively. The ratio of reversed-phase to normal phase, LC-UV to LC-MS and isocratic elution to gradient elution were 61:3, 43:7 and 55:11, respectively. With the exception of one article the reported recoveries ranged from 60.3% to 109.6%. It is noteworthy, that, the performance metrics of high-performance liquid chromatography are better compared to other assays of antiepileptic drugs in biological matrices. This review describes the relevant liquid chromatographic method conditions over the past 30 years for the analysis of this class of drugs, which provides a basis for further method development and optimization.

New Methods Used in Pharmacokinetics and Therapeutic Monitoring of the First and Newer Generations of Antiepileptic Drugs (AEDs)

The review presents data from the last few years on bioanalytical methods used in therapeutic drug monitoring (TDM) of the 1st-3rd generation and the newest antiepileptic drug (AEDs) cenobamate in patients with various forms of seizures. Chemical classification, structure, mechanism of action, pharmacokinetic data and therapeutic ranges for total and free fractions and interactions were collected. The primary data on bioanalytical methods for AEDs determination included biological matrices, sample preparation, dried blood spot (DBS) analysis, column resolution, detection method, validation parameters, and clinical utility. In conclusion, the most frequently described method used in AED analysis is the LC-based technique (HPLC, UHPLC, USLC) combined with highly sensitive mass detection or fluorescence detection. However, less sensitive UV is also used. Capillary electrophoresis and gas chromatography have been rarely applied. Besides the precipitation of proteins or LLE, an automatic SPE is often a sample preparation method. Derivatization was also indicated to improve sensitivity and automate the analysis. The usefulness of the methods for TDM was also highlighted.

Current Perspective and Developments in Electrochemical Sensors Modified with Nanomaterials for Environmental and Pharmaceutical Analysis

Background:

Over the past few decades, environmental pollution has appeared to be one of the most crucial global problems. The widespread intensification of numerous hazardous pollutants in the environment need the modern researchers to develop viable, reproducible and cost-effective determination tools for the reliable environmental analysis. The beneficial, as well as perilous, biological compounds are receiving growing interest due to their variable composition which produces advantageous and toxic impacts on human and the environment. Several conventional analytical methods have been established for the pharmaceutical and environmental analysis. However, certain drawbacks limited their practices in the modern rapidly growing era of science and technology. The development of electrochemical sensors has emerged as more beneficial and promising tool as against other traditional analytical approaches, in terms of simplicity, cost-effectiveness, sensitivity, stability and reliability. Nonetheless, the over potential and low anodic/cathodic current response are both considered as bottlenecks for the determination of electroactive entities exploiting electrochemical sensors. Interestingly, these problems can be easily resolved by modifying the electrodes with a variety of conductive materials, especially nanostructures.

Objective:

This review covers different electrochemical methods, reported in the literature, for the environmental and pharmaceutical analysis through simple and cost-effective nanostructures-based sensors. The electrochemical techniques with different modes and the modification of electrodes with highly conductive and prolific polymeric and nanostructured materials used for the determination of different environmental and pharmaceutical samples are the main prominence of this review. Various kinds of nanomaterials, e.g. metal, metal oxide and their composites, have been synthesized for the fabrication of sensitive electrodes.

Conclusion:

Nanostructures played a pivotal role in the modification of electrodes, which substantially enhanced the capability and sensitivity of electrochemical sensors. The proper modification of electrodes has materialized the swift detection of electroactive compounds at very low limits and offered the feasible determination procedure without any kind of signal fluctuation and over potential. In crux, due to their enhanced surface area and excellent catalytic properties, nanomaterials recently appeared as the most promising candidates in the field of electrode modification and significantly impacted the detection protocols for various environmental pollutants, viz. pesticides, metal ions and drugs.

A simple and cost-effective HPLC-UV method for the detection of levetiracetam in plasma/serum of patients with epilepsy

A simple, fast and cost-effective method was developed and validated for the determination of levetiracetam (LEV) in plasma/serum of patients using high performance liquid chromatography (HPLC) with ultraviolet detection. The stability of LEV plasma/serum samples over time and in different blood collection tubes was evaluated. Serum/plasma samples were deproteinized by methanol spiked with the internal standard, gabapentin. HPLC was carried out on a Venusil XBP C₁₈ , 250 × 4.6 mm, 5 μm column, at a flow rate of 1.0 mL/min and with mobile phase consisting of 50 mm potassium dihydrogen phosphate-acetonitrile at a pH of 5.5. The UV detector was set at 205 nm and 10 μL was injected. Total runtime was 15 min. Calibration curves were linear (correlation coefficient = 0.999) over a concentration range of 1-60 μg/mL. Relative standard deviation values for both the inter-day and intra-day precision and accuracy were <5% for the concentration range. The influence of different collection tubes and the effect of time on the stability of LEV was investigated. These factors may cause inaccuracies owing to drug-protein binding and interference in the matrix. This method is simple, fast, cost-effective, reliable and accurate with minimal sample preparation for daily routine use in therapeutic drug monitoring.

Effect of piperine on pharmacokinetics of sodium valproate in plasma samples of rats using gas chromatography-mass spectrometry method

Piperine (PIP) is used as anticonvulsant in traditional Chinese medicine. Co-administration of low-dose sodium valproate with PIP has been regarded to have potential anticonvulsant activity.

Determination of valproic acid in human plasma using dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection

OBJECTIVES

Dispersive liquid-liquid microextraction coupled with gas chromatography (GC)-flame ionization detector was developed for the determination of valproic acid (VPA) in human plasma.

MATERIALS AND METHODS

Using a syringe, a mixture of suitable extraction solvent (40 µl chloroform) and disperser (1 ml acetone) was quickly added to 10 ml of diluted plasma sample containing VPA (pH, 1.0; concentration of NaCl, 4% (w/v)), resulting in a cloudy solution. After centrifugation (6000 rpm for 6 min), an aliquot (1 µl) of the sedimented organic phase was removed using a 1-µl GC microsyringe and injected into the GC system for analysis. One variable at a time optimization method was used to study various parameters affecting the extraction efficiency of target analyte. Then, the developed method was fully validated for its accuracy, precision, recovery, stability, and robustness.

RESULTS

Under the optimum extraction conditions, good linearity range was obtained for the calibration graph, with correlation coefficient higher than 0.998. Limit of detection and lower limit of quantitation were 3.2 and 6 μg/ml, respectively. The relative standard deviations of intra and inter-day analysis of examined compound were less than 11.5%. The relative recoveries were found in the range of 97 to 107.5%. Finally, the validated method was successfully applied to the analysis of VPA in patient sample.

CONCLUSION

The presented method has acceptable levels of precision, accuracy and relative recovery and could be used for therapeutic drug monitoring of VPA in human plasma.

On the Slow Diffusion of Point-of-Care Systems in Therapeutic Drug Monitoring

Recent advancements in point-of-care (PoC) technologies show great transformative promises for personalized preventative and predictive medicine. However, fields like therapeutic drug monitoring (TDM), that first allowed for personalized treatment of patients' disease, still lag behind in the widespread application of PoC devices for monitoring of patients. Surprisingly, very few applications in commonly monitored drugs, such as anti-epileptics, are paving the way for a PoC approach to patient therapy monitoring compared to other fields like intensive care cardiac markers monitoring, glycemic controls in diabetes, or bench-top hematological parameters analysis at the local drug store. Such delay in the development of portable fast clinically effective drug monitoring devices is in our opinion due more to an inertial drag on the pervasiveness of these new devices into the clinical field than a lack of technical capability. At the same time, some very promising technologies failed in the clinical practice for inadequate understanding of the outcome parameters necessary for a relevant technological breakthrough that has superior clinical performance. We hope, by over-viewing both TDM practice and its yet unmet needs and latest advancement in micro- and nanotechnology applications to PoC clinical devices, to help bridging the two communities, the one exploiting analytical technologies and the one mastering the most advanced techniques, into translating existing and forthcoming technologies in effective devices.

Chiral chromatographic resolution of antiepileptic drugs and their metabolites: a challenge from the optimization to the application

A large number of the antiepileptic drugs (AEDs) presently available for clinical practice are chiral compounds while others, although achiral, may originate pharmacologically active chiral metabolites in vivo. The well-known implications of chirality in pharmacokinetics and pharmacodynamics demand the investigation of pharmacological properties for a racemic mixture and each enantiomer. To achieve these objectives, appropriate chiral analytical methods must be available. This article provides the first review of the current state of the art in chiral chromatographic methods available for quantifying enantiomers of AEDs in distinct matrices. Particular attention is paid to the methodological aspects and optimization strategies that successfully allow enantiomeric chromatographic separation of chiral AEDs and/or metabolites. Furthermore, the relevance of these methods in supporting the discovery and development of chiral AEDs is emphasized. In parallel and whenever available, the principal validation parameters are herein considered and related to the stage of drug discovery and development. In an attempt to optimize anticonvulsant activity and simultaneously diminish toxic effects, many pharmaceutical companies have started to manufacture single enantiomers. Therefore, chiral chromatographic techniques will be essential and the information herein compiled can be used as a framework for developing them.

Optimization and validation of bioanalytical SPE – HPLC method for the simultaneous determination of carbamazepine and its main metabolite, carbamazepine-10, 11-epoxide, in plasma

Carbamazepine is widely used as an antiepileptic drug in the treatment of partial and generalized tonic-clonic seizures. Carbamazepine 10,11-epoxide is the most important metabolite of carbamazepine, because it is a pharmacologically active compound with anticonvulsant properties. According to that, the routine analysis of carbamazepine 10,11-epoxide along with carbamazepine may provide optimal therapeutic monitoring of carbamazepine treatment. The aim of this study was to optimize and validate a simple and reliable solid - phase extraction method followed by RP-HPLC for the simultaneous determination of plasma levels of carbamazepine and carbamazepine-10,11-epoxide, in order to assure the implementation of the method for therapeutic monitoring. The extraction of the analytes from the plasma samples was performed by means of a solid-phase extraction procedure. The separation was carried out on a reversed-phase column using isocratic elution with acetonitrile and water (35:65, v/v) as a mobile phase. The temperature was 30°C and UV detection was set at 220 nm. The extraction yield values were more than 98% for all analytes, measured at four concentration levels of the linear concentration range. The method displayed excellent selectivity, sensitivity, linearity, precision and accuracy. Stability studies indicate that stock solutions and plasma samples were stabile under different storage conditions at least during the observed period. The method was successfully applied to determine the carbamazepine and carbamazepine-10,11-epoxide in plasma of epileptic patients treated with carbamazepine as monotherapy and in polytherapy. In conclusion, the proposed method is suitable for application in therapeutic drug monitoring of epileptic patients undergoing treatment with carbamazepine.