Liquid chromatographic assay based on microextraction by packed sorbent for therapeutic drug monitoring of carbamazepine, lamotrigine, oxcarbazepine, phenobarbital, phenytoin and the active metabolites carbamazepine-10,11-epoxide and licarbazepine

Preparation of a β-cyclodextrin grafted magnetic biochar for efficient extraction of four antiepileptic drugs in plasma samples

Simultaneous monitoring of plasma concentration levels of multiple antiepileptic drugs (AEDs) is essential for dose adjustment in comprehensive epilepsy treatment, necessitating a sensitive technique for accurate extraction and determination of AEDs. Herein, a magnetic solid-phase extraction (MSPE) technique on the basis of modified biochar (BC) is investigated to extract four AEDs from plasma, in conjunction with high performance liquid chromatography. BC derived from Zizyphus jujuba seed shells was activated by phosphoric acid (PBC) and magnetized via coprecipitation to produce MPBC. The MPBCCD obtained after modification with β-cyclodextrin (CD) was characterized and evaluated for adsorption. It exhibited fast adsorption kinetics based on second-order kinetics and satisfactory adsorption capacity for AEDs. Then it was employed as the MSPE adsorbent and the influencing parameters were optimized. The enrichment factor was 18.75. The validation analysis revealed a favorable linearity that ranged from 0.04 to 20 μg·mL-1 along with a low limit of detection of 6.85 to 10.19 ng·mL-1. The recovery of the AEDs ranged from 78.7 to 109.2 %, with relative standard deviations below 6.7 %. Using quantum chemistry theory calculations and experimental results analysis, the adsorption mechanism was investigated. It disclosed that the suggested strategy built upon MPBCCD was appropriate for the assessment of AEDs in plasma and expanded the usage of BC as the environmentally favorable matrix for the analysis of biological samples.

Titania-based fabric phase sorptive extraction approach for the determination of antiepileptic drugs, levetiracetam and lamotrigine in urine samples using high-performance liquid chromatography-photo diode array detection

A new fabric phase sorptive extraction (FPSE) based separation and enrichment method was developed for sensitive determination of two antiepileptic drug molecules, Levetiracetam (LEV) and Lamotrigine (LTG). The analysis of these drug molecules was performed with high-performance liquid chromatography equipped with photodiode array detector (HPLC-PDA) after FPSE. HPLC analysis was carried out by using phenyl hexyl column, under isocratic conditions with the mobile phase composed of pH 3.0 buffer-acetonitrile (77:23 v: v). All parameters affecting the separation and enrichment process were studied and optimized step by step. The linear working range of the developed method was calculated in the range of 10.0-1000.0 ng mL-1 for both the drug molecules (LEV and LTG). The limits of detection of the method (LODs) were calculated as 2.72 and 3.64 ng mL-1, respectively. The relative standard deviation (%RSD) values of the developed method as an indicator of precision were varied between 4.0 and 7.3. The accuracy of the optimized FPSE method was determined by the recovery tests utilizing spiked samples and results were assessed in the range from 94.6 to 106.3%. This is the first application of sol-gel Titania polycaprolactone-polydimethylsiloxane-polycaprolactone (Ti-PCAP-PDMS-PCAP) based FPSE membrane in the determination of antiepileptic drug molecules.

Greenness assessment of microextraction techniques in therapeutic drug monitoring

Aim: In this study, we evaluated the greenness and whiteness scores for microextraction techniques used in therapeutic drug monitoring. Additionally, the cons and pros of each evaluated method and their impacts on the provided scores are also discussed. Materials & methods: The Analytical Greenness Sample Preparation metric tool and white analytical chemistry principles are used for related published works (2007-2023). Results & conclusion: This study provided valuable insights for developing methods based on microextraction techniques with a balance in greenness and whiteness areas. Some methods based on a specific technique recorded higher scores, making them suitable candidates as green analytical approaches, and some others achieved high scores both in green and white areas with a satisfactory balance between principles.

UHPLC-MS/MS for plasma lamotrigine analysis and comparison with a homogenous enzyme immunoassay

Aims: To develop and validate a UHPLC-MS/MS method for lamotrigine (LTG) analysis in human plasma and evaluate its agreement with a homogenous enzyme immunoassay (HEIA). Materials & methods: The UHPLC-MS/MS method was developed and validated according to the USFDA/EMA guidelines. A Bland-Altman plot was used to evaluate the agreement between UHPLC-MS/MS and HEIA. Results: Samples were pretreated with one-step protein precipitation and separated in 2.6 min. The intra- and inter-day bias and imprecisions were -15.8 to 15.0% and less than 11.17%, respectively. The recovery and matrix factor were 98.30 to 111.97%. The mean overestimation of UHPLC-MS/MS compared with HEIA was 21.57%. Conclusion: A rapid, sensitive and robust UHPLC-MS/MS method for plasma LTG analysis was developed and validated and was a 21.57% overestimation compared with HEIA.

Simple HPLC-UV Method for Therapeutic Drug Monitoring of 12 Antiepileptic Drugs and Their Main Metabolites in Human Plasma

The objective of the present report was to develop and validate a simple, selective, and reproducible high-performance liquid chromatography method with UV detection suitable for routine therapeutic drug monitoring of the most commonly used antiepileptic drugs and some of their metabolites. Simple precipitation of plasma proteins with acetonitrile was used for sample preparation. 10,11-dihydrocarbamazepine was used as an internal standard. Chromatographic separation of the analytes was achieved by gradient elution on a Phenyl-Hexyl column at 40 °C, using methanol and potassium phosphate buffer (25 mM; pH 5.1) as a mobile phase. The method was validated according to the FDA guidelines for bioanalytical method validation. It showed to be selective, accurate, precise, and linear over the concentration ranges of 1-50 mg/L for phenobarbital, phenytoin, levetiracetam, rufinamide, zonisamide, and lacosamide; 0.5-50 mg/L for lamotrigine, primidone, carbamazepine and 10-monohydroxycarbazepine; 0.2-10 mg/L for carbamazepine metabolites: 10,11-trans-dihydroxy-10,11-dihydrocarbamazepine and carbamazepine-10,11-epoxide; 0.1-10 mg/L for oxcarbazepine; 2-100 mg/L for felbamate and 3-150 mg/L for ethosuximide. The suitability of the validated method for routine therapeutic drug monitoring was confirmed by quantification of the analytes in plasma samples from patients with epilepsy on combination antiepileptic therapy.

Lamotrigine Extraction and Quantification by UPLC-DAD in Plasma from Patients with Bipolar Disorder

A sensitive and efficient analytical process for detecting lamotrigine in acidic solution based in ultra-high-performance liquid chromatography-diode array detector (UPLC-DAD) was developed; the stationary phase used was a C8, 150 × 4.6 mm, 2.6 µm. The mobile phase consisted of acetonitrile/acidified water (0.01% H₃PO₄ and 0.005% triethylamine, pH 2.4) (25 : 75 v/v). Limits of detection and quantification were 0.02 µg/mL and 0.05 µg/mL, respectively. The working interval for the evaluation of the method ranged from 0.05 to 12 µg/mL, and the linear fit of the experimental data has a value of r2≥0.98. Before quantifying lamotrigine in plasma of patients with bipolar disorder, lamotrigine was released from plasma proteins with a 0.2 M sodium hydroxide solution, and then proteins were removed by precipitation with acetonitrile. Afterward, the lamotrigine base was dissolved in ethyl acetate. This extract was reconstituted in potassium phosphate solution (pH 2.4) to obtain more than 98% of lamotrigine protonated in N₂, which was detected and quantified as indicated above. The absolute percentage of lamotrigine recovery is  ≥80% for all tested concentration levels. The accuracy and precision of the method have %CV values <4% for the lamotrigine levels of 3, 6, and 9 µg/mL. The correlation coefficient for the used concentration range is 0.99. The analytical method is precise and sensitive to measure lamotrigine levels expected in plasma of BD patients and these levels were in the therapeutic dose range.

Development of magnetic molecularly imprinted polymers with double templates for the rapid and selective determination of carbamazepine and lamotrigine in serum

A dual-template magnetic molecularly imprinted polymer (Dt-MMIP) with a specific recognition capability for carbamazepine (CBZ) and lamotrigine (LTG) was synthesized using methacrylic acid as a functional monomer, and ethylene glycol dimethylmethacrylate as a cross-linking agent. A magnetic non-molecularly imprinted polymer without templates (MNIP) was also prepared using the same procedure. The prepared polymers were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy and adsorption experiments. Results indicated that both Dt-MMIPs and MNIPs were microspherical nanoparticles, and the surface of the Dt-MMIP was rougher than that of the MNIP. In addition, the prepared Dt-MMIPs possessed a higher adsorption capacity and better selectivity for CBZ and LTG than the MNIPs. The maximum static adsorption capacities of Dt-MMIP for CBZ and LTG were 249.5 and 647.9 μg g^-1, respectively, whereas those of MNIP were 75.8 and 379.8 μg g^-1, respectively. The obtained Dt-MMIPs were applied as a magnetic solid-phase extraction sorbent for the rapid and selective extraction of CBZ and LTG in rat serum samples, and determination was performed by high-performance liquid chromatography with UV detection (HPLC-UV). The developed method of dispersive SPE based on Dt-MMIPs coupled to HPLC-UV has good rapidity and selectivity, and application prospects in serum.

Simultaneous quantification of oxcarbazepine and its active metabolite in spiked human plasma using ultra performance liquid chromatography-MS/MS

Aim: Clinical monitoring of oxcarbazepine (OXC) and its metabolite licarbazepine (MHD) in biological matrix requires a sensitive and validated analytical method. The aim of this study is to develop and validate an optimized ultra performance liquid chromatography-MS/MS based bioanalytical method for the simultaneous estimation of OXC and its metabolite MHD in human plasma, using deuterated internal standard method. Materials & methods: A reverse phase ultra performance liquid chromatography analysis and mass spectrometric detection was performed using electrospray ionization in positive ion mode as interface, multiple reaction monitoring as mode of acquisition. Results & conclusion: The linearity range was 10-4011 ng/ml for OXC and 40-16061 ng/ml for MHD. The kinetic parameters were calculated and compared for bioequivalence. This method fulfilled the validation guidelines, could be employed for determining bioavailability and in new formulation development studies.

pH-induced homogeneous liquid-liquid microextraction method based on new switchable deep eutectic solvent for the extraction of three antiepileptic drugs from breast milk

Aim: A pH-induced homogeneous liquid-liquid microextraction (HLLME) using a new switchable deep eutectic solvent has been used for the extraction of three antiepileptic drugs from breast milk samples. Methodology: This method is based on phase separation by changing pH. An ammonia solution and a phosphocholine chloride: hexanoic acid: p-aminophenol deep eutectic solvents were used as the phase separation agent and extraction solvent, respectively. Results: Significant factors were studied and the detection limits and enrichment factors were in the ranges of 0.009-0.19 ng ml^-1 and 182-212 for the analytes, respectively. Also, linear ranges were wide (0.63-500 ng ml^-1) and the method precision was acceptable. Conclusion: The introduced method was successfully applied for the determination of the analyte concentrations in breast milk samples.

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.

Review of Chromatographic Methods Coupled with Modern Detection Techniques Applied in the Therapeutic Drugs Monitoring (TDM)

Therapeutic drug monitoring (TDM) is a tool used to integrate pharmacokinetic and pharmacodynamics knowledge to optimize and personalize various drug therapies. The optimization of drug dosing may improve treatment outcomes, reduce toxicity, and reduce the risk of developing drug resistance. To adequately implement TDM, accurate and precise analytical procedures are required. In clinical practice, blood is the most commonly used matrix for TDM; however, less invasive samples, such as dried blood spots or non-invasive saliva samples, are increasingly being used. The choice of sample preparation method, type of column packing, mobile phase composition, and detection method is important to ensure accurate drug measurement and to avoid interference from matrix effects and drug metabolites. Most of the reported procedures used liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) techniques due to its high selectivity and sensitivity. High-performance chromatography with ultraviolet detection (HPLC-UV) methods are also used when a simpler and more cost-effective methodology is desired for clinical monitoring. The application of high-performance chromatography with fluorescence detection (HPLC-FLD) with and without derivatization processes and high-performance chromatography with electrochemical detection (HPLC-ED) techniques for the analysis of various drugs in biological samples for TDM have been described less often. Before chromatographic analysis, samples were pretreated by various procedures-most often by protein precipitation, liquid-liquid extraction, and solid-phase extraction, rarely by microextraction by packed sorbent, dispersive liquid-liquid microextraction. The aim of this article is to review the recent literature (2010-2020) regarding the use of liquid chromatography with various detection techniques for TDM.

Electromembrane extraction as a new approach for determination of free concentration of phenytoin in plasma using capillary electrophoresis

PURPOSE

Electromembrane extraction is a new membrane-based extraction method in which charged compounds are extracted by an electric field. So far, this method has been used to extract and isolate a variety of acidic and basic drugs from various samples, including blood and plasma. However, in this procedure, it is not yet clear whether only unbound fraction of a drug is extracted or the total drug. The aim of this study is to reveal the nature of drug extraction in the presence of plasma proteins.

METHODS

To determine the nature of the extraction, the electromembrane extraction was performed from plasma solutions of phenytoin with concentrations 0.03 and 1.0 μg/mL, then the result was compared with the values obtained from the electromembrane extraction of ultrafiltrate of the same solutions (free concentration) and protein-free ultrafiltrate of plasma with final concentration of 0.03 and 1.0 μg/mL (total concentration). For this purpose, EME followed by capillary electrophoresis coupled with diode array detection was optimized and validated.

RESULTS

The results showed that the electromembrane extraction method was only able to extract the unbound fraction of phenytoin from plasma samples. The method was validated over a concentration range of 0.03-4 μg/mL. The inter and intra-assay precisions were less than 6.7%. The phenytoin protein binding was also determined to be in agreement with the literature data and confirms the validity of this method.

CONCLUSION

This sensitive and quick EME approach for determining the free concentration of a phenytoin, can be a good alternative to classic methods for therapeutic drug monitoring and pharmacokinetic studies.

Current trends on microextraction by packed sorbent – fundamentals, application fields, innovative improvements and future applications

MEPS, the acronym of microextraction by packed sorbent, is a simple, fast and user- and environmentally-friendly miniaturization of the popular solid-phase extraction technique (SPE).

Development and full validation of an innovative HPLC-diode array detection technique to simultaneously quantify lacosamide, levetiracetam and zonisamide in human plasma

Aim: To implement pharmacokinetic drug monitoring and individualize the posology of new antiepileptic drugs, the first HPLC-diode array detection method was developed and validated to simultaneously quantify lacosamide, levetiracetam and zonisamide in human plasma. Materials & methods: Preceded by a reproducible liquid–liquid extraction, chromatographic separation was achieved by using a C18 column of 5 cm length and a mobile phase of water/acetonitrile. Full validation was performed according to international guidelines. Results: The method was linear within 0.5–30, 2.5–40.0 and 0.5–50.0 μg ml-1 for lacosamide, levetiracetam and zonisamide, respectively (r2 ≥ 0.998), accurate (-12.411–8.303%), precise (≤8.875%). Conclusion: This innovative HPLC-diode array detection method was successfully employed in clinical practice and is expected to empower epileptic patients with a personalized pharmacotherapy service.

[Formula: see text]

Simultaneous Determination of Carbamazepine and Carbamazepine-10,11-epoxide in Different Biological Matrices by LC-MS/MS

An uncomplicated, sensitive liquid chromatography linked to mass spectrometry (LC/MS) for evaluation of carbamazepine and carbamazepine-10,11-epoxide (its metabolite) in human plasma, human saliva, rat plasma, and rabbit plasma was developed. Analyses were conducted on a Zorbax SB-C18, 100 mm × 3 mm ID, 3.5 μm column, at a column temperature of 40 ºC. The mobile phase was comprised of 0.1% formic acid in water and methanol in a 35 : 65 (v/v) ratio, with a flow rate of 0.4 mL/min. Lacosamide was utilized as internal standard. Under these chromatographic conditions, the retention times of lacosamide, carbamazepine-10,11-epoxide, and carbamazepine were 1.4 min, 1.6 min, and 2.2 min, respectively. The quantification of the analytes was performed using multiple reaction monitoring, with the use of a triple quadrupole mass spectrometer with electrospray positive ionization. The monitored ions were m/z 194 derived from m/z 237 for carbamazepine, m/z 180 derived from m/z 253 for carbamazepine-10,11-epoxide, and m/z 108 derived from m/z 251 for lacosamide. The samples were prepared by protein precipitation from 0.2 mL of plasma/saliva using 0.6 mL of internal standard solution in methanol. Calibration curves were constructed over the ranges 1.1–17.6 µg/mL and 0.23–5.47 µg/mL for carbamazepine and carbamazepine-epoxide, respectively. The coefficients of determination obtained by using a weighted (1/x) linear regression were greater than 0.994. The reported LC-MS/MS method was applied to preclinical pharmacokinetic studies and therapeutic drug monitoring.

Development and application of an ex vivo fosphenytoin nasal bioconversion/permeability evaluation method

There is an increasing interest in the intranasal delivery of central nervous system-active drugs due to the existence of a direct nose-to-brain connection. However, poor solubility limits the amount of drug that can be administered within an aqueous solution. In the present work, the objectives were to develop an ex vivo bioconversion/permeability evaluation method and to study the ex vivo bioconversion of the hydrophilic phosphate ester prodrug fosphenytoin (FOS) to the active drug phenytoin (PHT) and their comparative nasal permeation. Bioconversion/permeability studies were performed in excised porcine nasal mucosa mounted in Ussing chambers. The physical integrity of the tissues was evaluated by measurement of the transepithelial electrical resistance (TEER). The simultaneous quantitative assay of FOS, PHT and its major metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) was developed and validated according to international guidelines using a liquid chromatography analytical method. The FOS bioconversion rate and PHT and FOS apparent permeability coefficients (Papp) were determined at different time points. FOS bioconversion was also qualitatively investigated in human nasal mucus. The developed liquid chromatography method combines a fast and inexpensive sample preparation with inactivation of the enzymatic metabolism of the prodrug during sample manipulation and storage. It was linear, precise, accurate, and presented a high analyte recovery. FOS was converted ex vivo to PHT but the metabolite HPPH was not detected. The bioconversion rate increased with FOS concentration and with time, which suggests a diffusion-limited process. FOS was also converted to its active drug by human nasal mucus. A novel mathematical data analysis method was developed to reduce the bias introduced by variable mucosal TEER in the permeability results. At comparable FOS and PHT concentrations the ln(Papp(PHT)) of both compounds showed little difference, which indicates that the use of a hydrophilic and charged prodrug did not hinder overall drug permeation. At the highest tested FOS concentration it was possible to quantify FOS in the receiver chambers, meaning that at a sufficiently high concentration the FOS permeation rate overcame its bioconversion rate. The ln(Papp(PHT)) tended to similar equilibrium values as the assay progressed, but with higher FOS concentrations that equilibrium was attained faster. Acidic pH reduced the permeability of both PHT and FOS. The developed bioconversion/permeability evaluation method will constitute an important tool to select the most promising formulations before proceeding to in vivo studies. Importantly, it allowed the demonstration of phosphatase activity and FOS bioconversion in nasal mucosa, as well as the prodrug's nasal permeation potential. Furthermore, this study demonstrates the possibility of formulating phosphate prodrugs of poorly soluble central nervous system-active drugs as a strategy to increase the solubilized drug doses administered through the nasal route.