Biomonitoring Livestock Antiparasitic Residues: Development of Fast Mass Spectrometric Methods for the Quantification of Ivermectin, Albendazole, and their Metabolites in Sheep Plasma and Feces

Antiparasitic substances are extensively used in livestock farming against common parasitic infections. Improper utilization of these medicines often leads to the development of antiparasitic resistance and the detection of residues across the food chain, posing significant challenges to animal health, food safety, and public health. The objective of this study was to monitor antiparasitics' pharmacokinetics after the administration of ivermectin and albendazole in farm sheep. To achieve this goal, a fast LC-ESI-MS/MS method was developed and validated for the simultaneous quantification of ivermectin, albendazole, and their metabolites in sheep plasma. Concurrently, a probe electrospray tandem mass spectrometry ultrafast method was also developed for the real-time monitoring of albendazole and its metabolites in plasma. In addition, the liquid chromatography methodology was extended and validated for the detection of ivermectin in sheep feces, offering a non-invasive alternative to tissue and biofluids analysis. The detection capability values estimated for the techniques developed herein for the studied compounds and their metabolites in plasma ranged from 0.1 to 50.2 ng/mL, while the respective values for ivermectin in feces ranged between 5.0 and 26.9 ng/g. Recoveries fluctuated from 64% to 119%, proving the competence of the methods. The application of these methods in sheep samples, after the administration of the antiparasitic substances, effectively indicated the distribution of their concentrations, although in some cases, the individual animal effect seemed to interplay with the expected results. Also, these methods can contribute to the adjustment of the farm animal antiparasitic protocols, promoting the most effective utilization of the respective drugs while minimizing the risk of developing antiparasitic resistance. In a broader context, they may aid the advancement of veterinary medicine, offering practical solutions for monitoring the drug residues in farm animals and the derived products, and mitigating the risks associated with the extensive and uncontrolled utilization of antiparasitic drugs.