Tiamulin distribution in pigs: A pharmacokinetic study of plasma and oral fluid levels with tissues residues detection following intramuscular administration.

This study aimed to determine tiamulin depletion in the oral fluids (pooled and individual), plasma, and tissues of pigs following intramuscular (i.m.) administration. The correlation and pharmacokinetic parameters of tiamulin in individual oral fluids and plasma were established. Tiamulin concentrations in all matrices were determined by an ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method. The results obtained showed that tiamulin persisted in oral fluids at high concentrations and could be detected for up to 10 days after treatment. Furthermore, the analysis revealed the absence of tiamulin in plasma and muscle, with concentrations below the lower limit of quantification (< 1 µg/kg/µg/L) on the final day of the experiment (10 days). The presence of drug residues was detected in the liver (mean concentration 5.63 µg/kg ± 1.67 µg/kg) and in the kidneys (mean concentration 3.37 µg/kg ± 1.04 µg/kg) after 10 days of the experiment. The maximum concentrations (Cmax) of tiamulin, with values of 2205 ± 621 µg/L and 692 ± 111 µg/L in individual oral fluid and in plasma, were reached (tmax) at 2.00 and 3.50 h, respectively. The correlation between oral fluid and plasma was very strong at 1, 2, and 4 h. The concentrations in pooled oral fluid were much higher than in individual oral fluid, plasma and tissues.