Fluralaner, a novel ectoparasiticide for use in cattle: development and validation of a UFLC-MS/MS method for the assessment of its plasma pharmacokinetic behaviour

Abstract

Fluralaner is a novel isoxazoline compound used to control ectoparasites in domestic animals. Since resistance to widely used drug families is increasing, fluralaner is being developed as a pharmacological alternative for ectoparasite control in cattle. However, no validated UFLC–MS/MS method has yet been described for its detection and quantification in bovine plasma, which is essential to characterise its pharmacokinetic behaviour and to optimise pharmaceutical formulations under development. This study aimed to develop and validate a reliable UFLC-MS/MS method for the quantification of fluralaner in bovine plasma. The method was comprehensively validated in terms of linearity, precision (repeatability and reproducibility), accuracy, specificity, limit of detection (LOD), limit of quantification (LOQ), stability, recovery, and matrix effect (ME), using rigorous experimental procedures and statistical analyses. The LOD was established at 10 ng/mL, highlighting the method’s high sensitivity. Absolute recovery ranged from 87% to 133%, and relative standard deviation (RSD%) ranged from 2% to 9% for intra-assay and from 5% to 10% for inter-assay, indicating excellent precision. Furthermore, both recovery (70%–133%) and precision (RSD%≤10%) were within acceptable analytical limits. The method also demonstrated good linearity, accuracy, robustness, and low measurement uncertainty, supporting its suitability for fluralaner determination in bovine plasma. Given its strong performance in the validation process, this method provides a critical tool for future pharmacokinetic and tissue studies of fluralaner in cattle.