Development and validation of UPLC-MS/MS method for pharmacokinetics and tissue distribution of Tylvalosin and its bioactive metabolites in swine

Tylvalosin (acetylisovaleryltylosin), a breakthrough semi-synthetic derivative of tylosin engineered to address pharmacokinetic limitations and bacterial resistance, exhibits dual therapeutic efficacy against porcine reproductive and PRRSV-associated pneumonia and mycoplasma infections in swine. Limited research has yet to investigate pharmacokinetic profiles of tylvalosin and its metabolites. This study, therefore, aims to pioneer a robust UPLC-MS/MS method for simultaneous quantification of tylvalosin and its key bioactive metabolites, desmycosin 3-acetate and tylosin 3-acetate, in swine plasma and tissues, and to investigate the pharmacokinetic properties of different tylvalosin formulations. A robust UPLC-MS/MS method was developed and validated, showing excellent performance with good linearity, low deviation, high accuracy, minimal carry-over and matrix effects, as well as favorable stability under various conditions. Pharmacokinetic analysis following intravenous (i.v.) or intragastric administration in swine revealed that formulation I outperformed other formulations, exhibiting the highest bioavailability ( F , 57.32%), the longest elimination half-life ( t 1/2 , 7.93 h), and a delayed time to maximum plasma concentration ( t max , 3.14 h). Dose-normalized metabolites exposures were also significantly higher for formulation I compared to other formulations. Critically, tylvalosin and its metabolites preferentially accumulated in pulmonary and lymphatic tissues at 48 h post-administration, indicating rapid absorption, swift metabolism, and slow elimination. The findings confirm the optimized therapeutic potential of tylvalosin, particularly formulation I, supported by its favorable pharmacokinetic profile and tissue distribution. This study establishes a new standard for veterinary PK-PD research and provides a PK evidence-based formulation optimization approaches to enhance treatment efficacy.