A Rapid LC-MS-MS Method for the Quantitation of Antiepileptic Drugs in Urine

Simultaneous quantification of 11 antiepileptic drugs using limited isotope-labeled internal standards in LC-MS/MS: An accuracy assessment

This study aims to establish an LC-MS/MS method to simultaneously analyze 11 antiepileptic drugs with a particular focus on maintaining accuracy while reducing the number of isotope-labeled internal standards employed for cost-effectiveness. By applying a water/acetonitrile gradient elution containing 0.1 % formic acid and 2 mM ammonium formate as the mobile phase, optimal sensitivity for the target drugs could be obtained in positive ESI mode in LC-MS/MS. After optimizing various extraction techniques, extraction with 70 % acetonitrile was selected as it provided good recoveries (>93 %) for all targets without matrix effects. Accuracies within 3 % were achieved from the combination of six internal standards, while accuracies of 5 % and 10 % were obtained by reducing the number of internal standards to four and two, respectively, for more economical analysis. The accuracy of the established method was maintained in hyperglycemia, hyperlipidemia, and hyperalbuminemia sera, suggesting that it can be successfully applied to individual serum samples with various properties.

Quantification of levetiracetam in plasma and urine and its application to a pharmacokinetic study of traumatic brain injury patients

Background: Levetiracetam is an antiepileptic drug used to prevent or treat seizure in patients with severe traumatic brain injury. This study aimed to develop and validate methodology suitable for measuring levetiracetam concentrations in human plasma and urine. Methods: Plasma or urine (10 μl) samples were spiked with [²H₆]-levetiracetam and processed using an acetonitrile precipitation. ESI-LC-MS/MS was employed for analyte detection. Results: The levetiracetam calibration was linear from 0.1 to 50 mg/l in a combined matrix of plasma and urine. Intra- and inter-assay imprecision and accuracy in plasma were <7.7 and 109%, and in urine were <7.9 and 108%, respectively. Conclusion: The validated method was applied to a pharmacokinetic study of levetiracetam in critically ill patients with severe traumatic brain injury.

Development and Validation of a Highly Sensitive and Rapid LC-MS3 Strategy to Determine Oxcarbazepine and Its Active Metabolite in the Serum of Patients with Epilepsy and Its Application in Therapeutic Drug Monitoring

A sensitive and rapid bioanalytical method based on the LC-triple-stage fragmentation (LC-MS³) strategy on a hybrid triple quadrupole-linear ion trap mass spectrometer in combination with protein precipitation extraction for sample pretreatment has been developed and validated for the simultaneous determination of the antiepileptic drug oxcarbazepine (OXC) and its main active metabolite (MHD) in human serum. The separation was performed on a Waters XBridge BEH C18 column (2.5 µm, 2.1 × 50 mm) in isocratic elution with 0.1% formic acid in water and methanol (50:50, v:v) as the mobile phase. The run time for each sample was 2.0 min. The calibration curves ranging from 25 to 1600 ng/mL for OXC and from 0.5 to 32 μg/mL for MHD showed correlation coefficients (r) better than 0.99. All of the validation data, such as precision, accuracy and other parameters, fit the requirements of the current bioanalytical method validation guidelines. The LC-MS³ method for quantitation of OXC and MHD was compared with the LC-MRM based method. Passing–Bablok regression coefficients and Bland–Altman plots showed that the developed LC–MS³ method is a reliable method for quantitative analysis of OXC and MHD. The proposed LC-MS³ method was successfully applied to determine the serum concentrations of OXC and MHD to support a clinical study.

Simultaneous determination of plasma lamotrigine, lamotrigine N2-glucuronide and lamotrigine N2-oxide by UHPLC-MS/MS in epileptic patients

The plasma concentration of lamotrigine (LTG) and its metabolites has great interindividual variability. An UHPLC-MS/MS method for simultaneous determination of LTG and lamotrigine N2-glucuronide (LTG N2-GLUC), lamotrigine N2-oxide was developed, validated, and applied in 58 plasma samples. The ion transition was m/z 256.0 > 144.9 for LTG, 432.1 > 256.0 for LTG N2-GLUC, 272.2 > 241.9 for LTG N2-oxide, and 259.1 > 144.8 for LTG-¹³C₃ (internal standard). The flow rate was 0.4 mL/min with a run time of 3 min. The calibration range was 0.025-2 mg/L for LTG and LTG N2-GLUC, and 0.000625-0.05 mg/L for LTG N2-oxide. For all analytes, the intra-day and inter-day bias and imprecision were -11.7-5.7 % and less than 14.3 %, and the internal standard normalized recovery and matrix factor were 91.7-101.5 % and 98.1-110.1 % with CV < 13. 7%. Ten- and twenty-fold dilution with blank plasma did not affect the analysis. All analytes were stable in plasma at room temperature for 8 h, at -80 °C for 80 days, and after 3 freeze-thaw cycles. The LTG N2-GLUC/LTG ratio was 0.44 in LTG monotherapy group. The ratio was reduced to 0.17 when co-administrated with valproic acid, while elevated to 0.82 when co-administrated with enzyme inducer. In conclusion, this method is suitable for simultaneous determination of LTG, LTG N2-GLUC and LTG N2-oxide in human plasma.

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.