Determination of lamotrigine in human plasma by HPLC-PDA. Application to forensic samples

PURPOSE

Therapeutic drug monitoring of plasma lamotrigine (LTG) has customarily been carried out in order to prevent some its adverse effects. For forensic purposes, determination of LTG in plasma is an useful tool in cases of accidental overdose or suicidal attempts. Currently, there are several analytical methods available including some based on LC tandem mass spectrometry techniques, but simple and accessible LC-UV methods still can be useful for the purpose. Here we report on a new high-performance liquid chromatography method for the determination of lamotrigine in human plasma which has been developed and validated including selectivity, sensitivity, accuracy, precision and recovery studies.

METHODS

Lamotrigine and the internal standard chloramphenicol were extracted from plasma using liquid-liquid extraction using small volumes of buffer and ethylacetate. Detection was monitored at 305.7 and 276.0 nm for lamotrigine and chloramphenicol, respectively.

RESULTS

The method was linear concentration dependence within the range of 0.1-10 µg/ml, with a mean coefficient of correlation r = 0.993. The limit of detection (LOD) was 0.04 µg/ml and the limit of quantification (LOQ) was 0.1 µg/ml. Intra and interday precision values were lower than 9.0% at all concentrations studied. The intra and interday accuracy values ranged from - 7.6 to 10.1%. Recovery was found to be 98.9% or higher. The method here described was successfully applied to 11 postmortem blood samples received at the Forensic Sciences Institute of Santiago de Compostela (Spain).

CONCLUSION

A new HPLC method for the determination of lamotrigine in human plasma was developed and validated. A liquid-liquid extraction using small volumes of buffer and ethylacetate was optimized. The proposed method is suitable for forensic toxicological analysis.

Label-free SERS assay combined with multivariate spectral data analysis for lamotrigine quantification in human serum

Considering the need for a more time and cost-effective method for lamotrigine (LTG) detection in clinics we developed a fast and robust label-free assay based on surface-enhanced Raman scattering (SERS) for LTG quantification from human serum. The optimization and application of the developed assay is presented  showing the: (i) exploration of different methods for LTG separation from human serum; (ii) implementation of a molecular adsorption step on an ordered Au nanopillar SERS substrate; (iii) adaptation of a fast scanning of the SERS substrate, performed with a custom-built compact Raman spectrometer; and (iv) development of LTG quantification methods with univariate and multivariate spectral data analysis. Our results showed, for the first time, the SERS-based characterization of LTG and its label-free identification in human serum. We found that combining a miniaturized solid phase extraction, as sample pre-treatment with the SERS assay, and using a multivariate model is an optimal strategy for LTG quantification in human serum in a linear range from 9.5 to 75 μM, with LoD and LoQ of 3.2 μM and 9.5 μM, respectively, covering the suggested clinical therapeutic window. We also showed that the developed assay allowed for quantifying LTG from human serum in the presence of other drugs, thereby demonstrating the robustness of label-free SERS. The sensing approach and instrumentation can be further automated and integrated in devices that can advance the drug monitoring in real clinical settings.

Comparison of HPLC-DAD and UPLC-MS/MS in Monitoring Serum Concentration of Lamotrigine

Background:

Lamotrigine (LTG) is a broad-spectrum and first-line anti-epileptic drug. To monitor the serum levels of LTG in epileptic seizures patients, high-performance liquid chromatography with diode-array detection (HPLC-DAD) and ultra-performance liquid chromatography-- tandem mass spectrometry (UPLC-MS/MS) methods were established and compared.

Methods:

Imatinib was used as the internal standard (IS) for both methods. LTG and IS were detected at 246 nm by HPLC-DAD. In UPLC-MS/MS, LTG and IS positive ion were detected by multiple reaction monitoring (MRM), with m/z of 256/210.9 and 494/394.02, respectively. A total of 37 blood samples from epileptic patients were determined and studied by these two methods.

Results:

There was an acceptable linearity for the two methods. The concentration range of LTG was 0.59 ~ 22.20 mg/L by HPLC, and 0.28 ~ 23.97 mg/L by UPLC-MS/MS. The Pearson regression coefficient of Deming regression was 0.9653 (95% CI: 0.9332 to 0.9821). Bland–Altman method demonstrated that the concentration of LTG determined by UPLC-MS/MS was 8.3% higher than that determined by HPLC (limits of agreement, -32.0% to +48.6%).

Conclusion:

There was a significant correlation between the two methods. Both HPLC and UPLC- MS/MS can be used for routine clinical monitoring of LTG.

A LC-MS3 strategy to determine lamotrigine by Q-Q-trap tandem mass spectrometry coupled with triple stage fragmentation to enhance sensitivity and selectivity

A high-performance liquid chromatography tandem mass spectrometry cubed (HPLC/MS³) method was developed and validated to quantify lamotrigine in human plasma with carbamazepine as an internal standard. The HPLC/MS/MS system is composed of a Shimadzu UFLC XR high-performance liquid chromatograph coupled with a hybrid linear ion trap triple quadrupole mass spectrometer. Following simple protein precipitation with methanol, the separation of lamotrigine and carbamazepine was performed on an Agilent Poroshell 120 SB-C18 column (4.6 × 50 mm, 2.7 μm) using gradient elution with 0.1% formic acid in water (solvent I) and 0.1% formic acid in methanol (solvent II) at a flow rate of 0.8 mL min^-1. The total run time for each sample was 5 min. The method was validated for accuracy, precision, linearity, lower limit of quantification (LLOQ), selectivity, and other parameters. The LC/MS³ method was linear in the concentration range of 0.50-50.0 μg mL^-1 (R² ≥ 0.995). The LLOQ was 0.5 μg mL^-1, requiring only 30 μL of human plasma. Intra- and inter-day accuracies were <6.17% and precisions were <11.4% at all concentrations. The absolute recoveries (%) and matrix effect (%) for lamotrigine in human plasma were between 83.8 and 90.7. The developed and validated LC-MS³ assay was successfully applied to monitor the lamotrigine levels in human plasma after the administration of lamotrigine.

Lamotrigine-A Review of Analytical Methods Developed for Pharmaceutical Formulations and Biological Matrices

Lamotrigine owing to its excellent inhibitory property of neurotransmitter release especially glutamate is used in the treatment of epilepsy as a second-line antiepileptic drug. It differs from other antiepileptic drugs chemically and pharmacologically and is used as both monotherapy and adjunct therapy in the treatment of epilepsy. The present review focuses on two aspects (a) various analytical methods used in quantification of Lamotrigine in pharmaceutical formulations and (b) various analytical methods used to determine Lamotrigine in biological matrices. Here the various analytical methods are developed using different parameters and validation of employed methods is discussed. Estimated parameters like the linearity, LOD (Limit of detection) and LOQ (Limit of quantification) of validation are discussed for the individual method. The critical quality attributes like the wavelength of detection, mobile phase, columns, flow rate, retention time, and the sample preparation methods for the estimation of Lamotrigine by bioanalytical methods are also discussed.

Spectrophotometric determination of lamotrigine in plasma samples: Ultrasound-assisted emulsification-microextraction based on a hydrophobic deep eutectic solvent followed by back-extraction

In this study, sensitive detection of lamotrigine in human plasma samples was realized at a low cost approach through ultrasound-assisted emulsification-microextraction based on using a hydrophobic deep eutectic solvent followed by back-extraction (USAEME-DES-BE) method. After extraction, detection and quantification of lamotrigine were done by spectrophotometry in the UV region. The hydrophobicity of the deep eutectic solvent not only eliminates the need of the third solvent as an emulsifying agent but also helps to retrieve lamotrigine from the DES by back-extraction to another aqueous phase. The back extraction process allowed the drug to be measured in the UV region. Central composite design in combination with a desirability function approach was applied for the optimization of the USAEME-DES-BE procedure. Essential factors in the method efficiency were discussed, such as back-extraction solution, time of back-extraction, the ratio of DES components, pH, the volume of DES, salt concentration, and sonication time. The method exhibited a wide dynamic linear range from 0.5 to 10 µg mL^-1 and a limit of detection of 0.15 μg mL^-1. The established method was successfully applied to determine lamotrigine in human plasma samples with satisfactory relative recoveries.

Development, Characterization, and in-vivo Pharmacokinetic Study of Lamotrigine Solid Self-Nanoemulsifying Drug Delivery System

Purpose

This study aimed to prepare solid self-nanoemulsified drug delivery system (S-SNEDDS) of lamotrigine (LMG) for enhancing its dissolution and oral bioavailability (BA).

Methods

Nineteen liquid SNEDDS were prepared (R1-R19) using D-optimal design with different ratios of oil, surfactant (S), and cosurfactant (Cos). The formulations were characterized regarding robustness to dilution, droplet size, thermodynamic stability testing, self-emulsification time, in-vitro release in 0.1 N HCl and phosphate buffer (PB; pH 6.8). Design Expert^® 11 software was used to select the optimum formulations. Eight S-SNEDDS were prepared (S1-S8) using 2³ factorial design, and characterized by differential scanning calorimetry (DSC), powder x-ray diffraction (PXRD), and scanning electron microscopy (SEM). The optimum formulation was chosen regarding in-vitro drug released in 0.1 N HCl and PB, compared to pure LMG and commercial tablet (Lamictal^®). The BA of LMG from the optimized S-SNEDDS formulation was evaluated in rabbits compared to pure LMG and Lamictal^®.

Results

The optimized S-SNEDDS was S2, consisting of R9 adsorbed on Aeroperl^® 300 in a ratio of 1:1, with the best results regarding in-vitro drug released in 0.1 N HCl at 15 min (100%) compared to pure LMG (73.40%) and Lamictal^® (79.43%), and in-vitro drug released in PB at 45 min (100%) compared to pure LMG (30.46%) and Lamictal^® (92.08%). DSC, PXRD, and SEM indicated that LMG was molecularly dispersed within the solid nano-system. The BA of S2 was increased 2.03 and 1.605 folds compared to pure LMG, and Lamictal^®, respectively.

Conclusion

S2 is a promising S-SNEDDS formulation. It can be a potential carrier for improving dissolution, and BA of LMG.

Misdiagnosis of lamotrigine toxicity as posterior circulation transient ischemic attack or stroke

PURPOSE

Lamotrigine (LTG) is one of the most used antiseizure medications (ASMs). Titration is indicated for incomplete seizure control, but toxicity with vertigo, ataxia, and diplopia may ensue. Lamotrigine concentration would be the optimal diagnostic test. However, patients often receive a stroke evaluation when presenting to the emergency department (ED), leading to unnecessary cost and delayed management. We investigated the frequency of stroke evaluation for symptoms associated with LTG toxicity and attempted to identify factors leading to this expensive evaluation.

METHODS

We identified adult patients treated with LTG who presented to an emergency room with dizziness, ataxia, or diplopia and received a negative stroke evaluation, between 2003 and 2018. They were among 972 patients treated with LTG for epilepsy. We collected age at time of occurrence, symptoms presented, imaging studies performed, LTG dose and serum concentration, and the time the result was available. As a denominator, we also identified patients who developed clinical LTG toxicity during the same time period.

RESULTS

Thirteen patients with LTG toxicity had 16 negative stroke evaluations in the emergency room. Their mean age was 62 years (range: 43-79) as compared with 47 years for all patients treated with LTG (p < 0.0005). The mean daily LTG dose was 621 mg (range: 300-900 mg). A LTG serum concentration was requested on the day of evaluation in 7 instances, though the result was never available until at least the next day. In 4 instances, the LTG level was drawn 1-3 days after presentation. Five of the patients in this group were among 71 patients with clinical LTG toxicity and LTG concentration >20.

CONCLUSION

Emergency departments will frequently call a stroke alert for patients taking LTG and presenting with symptoms consistent with LTG toxicity, particularly in seniors at greater risk of stroke. This adds not only expense but also radiation and contrast exposure from computed tomography (CT) studies. We recommend that a rapid LTG assay be made available and always ordered in patients receiving LTG, avoiding the considerable expense of an unnecessary stroke evaluation.

Determination of lamotrigine in human plasma using liquid chromatography-tandem mass spectrometry

Aim

Lamotrigine (LTG) is a widely used anti‐epileptic drug that is administered to avoid seizures and to maintain seizure‐free status. However, several factors reportedly cause individual differences of plasma LTG levels, and the therapeutic target range of LTG varies between individuals. Thus, to optimize effective doses of LTG, we developed a rapid and simple method for determining plasma LTG concentrations.

Methods

Lamotrigine and the internal standard papaverine were extracted from human plasma using solid‐phase extraction. After filtration, 5‐μL aliquots of final samples were injected into the liquid chromatography‐tandem mass spectrometry instrument and LTG and internal standard were separated using a Cadenza CD‐C18 column (100 × 2 mm, 3 μm) with 0.1% formic acid in water/acetonitrile (2/1, v/v).

Results

The calibration curve was linear from 0.2 to 5.0 μg/mL, and assessments of recovery, intra‐ and inter‐day precision and accuracy, matrix effects, freeze and thaw stability, and long‐term stability demonstrated good reproducibility. Retention times of LTG and internal standard were 1.6 and 2.0 minutes, respectively, and the total run time was 3.5 minutes for each sample.

Conclusion

We developed a rapid and simple method for determining plasma LTG concentrations. The present novel system could be used to inform LTG dose adjustments for individual patients.

We developed a rapid and simple method for determining plasma concentrations of LTG showing good validation for a relatively wide range (0.2‐5.0 μg/mL). The present method can inform estimates of plasma concentrations of LTG to clinicians within 1 hour of sample collection.

Development and validation of an LC-MS/MS method for the determination of a novel thienoquinolin urea transporter inhibitor PU-48 in rat plasma and its application to a pharmacokinetic study

A specific, sensitive and stable high-performance liquid chromatographic-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantitative determination of methyl 3-amino-6-methoxythieno [2,3-b]quinoline-2-carboxylate (PU-48), a novel diuretic thienoquinolin urea transporter inhibitor in rat plasma. In this method, the chromatographic separation of PU-48 was achieved with a reversed-phase C18 column (100 × 2.1 mm, 3 μm) at 35°C. The mobile phase consisted of acetonitrile and water with 0.05% formic acid added with a gradient elution at flow rate of 0.3 mL/min. Samples were detected with the triple-quadrupole tandem mass spectrometer with multiple reaction monitoring mode via electrospray ionization source in positive mode. The retention time were 6.2 min for PU-48 and 7.2 min for megestrol acetate (internal standard, IS). The monitored ion transitions were mass-to-charge ratio (m/z) 289.1 → 229.2 for PU-48 and m/z 385.3 → 267.1 for the internal standard. The calibration curve for PU-48 was linear over the concentration range of 0.1-1000 ng/mL (r2 > 0.99), and the lower limit of quantitation was 0.1 ng/mL. The precision, accuracy and stability of the method were validated adequately. The developed and validated method was successfully applied to the pharmacokinetic study of PU-48 in rats.

Liquid chromatography tandem mass spectrometry method for the estimation of lamotrigine in human plasma: Application to a pharmacokinetic study

A reliable, selective and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the quantification of lamotrigine in human plasma using lamotrigine-¹³C3, d3 as an internal standard. Analyte and internal standard were extracted from human plasma by solid-phase extraction and detected in positive ion mode by tandem mass spectrometry with electrospray ionization (ESI) interface. Chromatographic separation was performed on a Chromolith^® SpeedROD; RP-18e column (50−4.6 mm i.d.) using acetonitrile: 5±0.1 mM ammonium formate solution (90:10, v/v) as the mobile phase at a flow rate of 0.500 mL/min. The calibration curves were linear over the range of 5.02–1226.47 ng/mL with the lower limit of quantitation validated at 5.02 ng/mL. The analytes were found stable in human plasma through three freeze (−20 °C)-thaw (ice-cold water bath) cycles and under storage on bench-top in ice-cold water bath for at least 6.8 h, and also in the mobile phase at 10 °C for at least 57 h. The method has shown good reproducibility, as the intra- and inter-day precisions were within 3.0%, while the accuracies were within ±6.0% of nominal values. The validated LC–MS/MS method was applied for the evaluation of pharmacokinetic and bioequivalence parameters of lamotrigine after an oral administration of 50 mg lamotrigine tablet to thirty-two healthy adult male volunteers.