Pharmacokinetics of tulathromycin in edible tissues of healthy and experimentally infected pigs with Actinobacillus pleuropneumoniae

The aim of this study was the comparison of the tissue pharmacokinetics of tulathromycin in healthy pigs and pigs experimentally infected with Actinobacillus pleuropneumoniae (App). Tulathromycin was given to 24 healthy and 24 infected pigs by intramuscular injection at a single dosage of 2.5mgkg(-1) body weight (b.w.). Pigs were euthanised at each group and then samples of liver, kidney, muscle, injection site and skin with fat were taken at scheduled time points. Drug concentrations were determined by LC-MS/MS. In this study, higher values of the area under the concentration-time curves (AUC) were calculated in all tissue samples taken from infected than healthy pigs. In pigs with App the AUCs of liver, kidney, muscle, skin with fat and injection site were 1111, 1973, 235, 181 and 2931mgkg(-1) h, while in pigs without inflammation they were 509, 1295, 151, 111 and 1587mgkg(-1) h, respectively. Maximum drug tissue concentrations (C-max) in infected animals were 2370, 6650, 2016, 666 and 83870 mu gkg(-1), while in healthy pigs they were 1483, 6677, 1733, 509 and 55006 mu gkg(-1), respectively. The eliminations half-times (T-1/2) were respectively longer in all tissue samples taken from infected animals (from 157.3 to 187.3h) than in healthy ones (from 138.6 to 161.2h). The tulathromycin tissue concentrations were significantly higher (p<0.05) in all tissue samples of the infected pigs compared with the healthy animals at 360h (from 0.0014 to 0.0280) and at 792h (from 0.0007 to 0.0242) after drug administration. The results suggest that the tissue pharmacokinetic properties and residue depletion of tulathromycin can be influenced by the disease state of animals.