Validated LC-MS/MS Assays for Novel Triazolyl-Oxazolidinones with Anticonvulsant Activities and Their Potential Applications in Stability and Pharmacokinetic Studies

Background: We recently synthesized a novel series of triazolyl-oxazolidinones (PH066, PH139, PH162, and PH166) that exhibited significant in vivo anticonvulsant activity in rat models of electrically- and chemically-induced seizures. Objectives: The objectives of the current study were to develop and validate analytical UPLC-MS/MS assays for quantitative determination of these novel compounds in plasma and tissue samples obtained from pharmacokinetic studies to support and/or explain the reported in vivo effects in rats, as well as to study the stability of these compounds in the solid state. Methods: Sensitive, selective, precise, and accurate UPLC-MS/MS methods were developed using a UPLC BEH C18 column for analyte separation. The mobile phase consisted of water with 0.1% formic acid and acetonitrile with 0.1% formic acid in different ratios depending on the analyte of interest. Quantitative determination was performed using the multiple-reaction monitoring scanning mode. The methods were utilized to determine the concentration of the four compounds in plasma and tissue samples obtained at different time points after intraperitoneal (IP) injection of 100 mg/kg of each compound to rats. The stability of the compounds was investigated under forced degradation conditions. Results: The developed methods were specific for each of the analytes and were found to be linear in the concentration range of 5–30 μg/mL in plasma and 0.5–25 μg/g in tissue samples. The intra-day and inter-day precision and accuracies were within the acceptable range for the four compounds. The methods were applied to quantify these compounds in the plasma and various tissue samples obtained from rats after IP administration of 100 mg/kg of each compound. The maximum plasma concentrations were 14.6, 9.20, 14.5, and 18.1 μg/mL, and those of brain were 2.6, 0.22, 1.9, and 2.8 μg/g for PH066, PH139, PH162, and PH166, respectively. The compounds degraded under forced degradation conditions to various degradation products. Conclusions: The developed methods were selective, linear, accurate, and precise and are suitable for quantitation of the four compounds in plasma and tissue samples obtained during pharmacokinetic investigations, as well as for detecting and quantifying their degradation products.