Pharmacokinetics of Tylvalosin Following Intravenous or Oral Administration at Different Doses in Broiler Chickens.

Tylvalosin is a macrolide antimicrobial with antibacterial activity against Gram-positive bacteria, some Gram-negative organisms, and mycoplasma. It is used to treat respiratory and enteric bacterial infections in swine and poultry. In this study, we aimed to investigate the pharmacokinetic changes in tylvalosin following its intravenous or oral administration at doses of 5, 10, and 25 mg/kg in broiler chickens. Forty-eight broiler chickens were included in the study. The plasma concentrations of tylvalosin were measured by using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and its pharmacokinetic parameters were evaluated by using both non-compartmental and compartmental analyses. The linear mixed-effects model revealed no dose proportionality within the 5-25 mg/kg range for either administration route. Based on pharmacokinetic data from a single oral dose, this study simulated a multiple-dose regimen of tylvalosin (25 mg/kg), demonstrating that a 6-hour dosing interval reaches a steady state after the fourth dose. Furthermore, the results show that the absolute bioavailability of tylvalosin after oral administration in chickens was relatively low, with values of 5.92%, 3.56%, and 3.04% for the doses of 5, 10, and 25 mg/kg, respectively. Further studies are required to significantly improve the oral bioavailability of tylvalosin and similar compounds through formulation optimization.