The influence of Actinobacillus pleuropneumoniae infection on tulathromycin pharmacokinetics and lung tissue disposition in pigs

A tulathromycin concentration and pharmacokinetic parameters in plasma and lung tissue from healthy pigs and Actinobacillus pleuropneumoniae (App)-infected pigs were compared. Tulathromycin was administered intramuscularly (i.m.) to all pigs at a single dose of 2.5mg/kg. Blood and lung tissue samples were collected during 33days postdrug application. Tulathromycin concentration in plasma and lung was determined by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) method. The mean maximum plasma concentration (C-max) in healthy pigs was 586 +/- 71ng/mL, reached by 0.5h, while the mean value for C-max of tulathromycin in infected pigs was 386 +/- 97ng/mL after 0.5h. The mean maximum tulathromycin concentration in lung of healthy group was calculated as 3412 +/- 748ng/g, detected at 12h, while in pigs with App, the highest concentration in lung was 3337 +/- 937ng/g, determined at 48h postdosing. The higher plasma and lung concentrations in pigs with no pulmonary inflammation were observed at the first time points sampling after tulathromycin administration, but slower elimination with elimination half-life t(1/2el)=126h in plasma and t(1/2el)=165h in lung, as well as longer drug persistent in infected pigs, was found.