Pharmacokinetics of florfenicol in turkey plasma, lung tissue, and pulmonary epithelial lining fluid after single oral bolus or continuous administration in the drinking water

Florfenicol (FF) is registered for treatment of bovine and swine respiratory diseases. Although, turkeys often suffer from bacterial respiratory tract infections, there is no registered formulation based on FF for poultry available in Europe. The aim of this study was to evaluate the pharmacokinetic behavior of FF in turkeys in plasma, lung tissue, and pulmonary epithelial lining fluid (PELF). The concentration and pharmacokinetic characteristics of FF in plasma, lung tissue, and PELF in turkeys were determined, either after a single oral bolus (30 mg/kg body weight, BW) or during and after continuous drinking water medication (30 mg/kg BW/d for 5 d). Plasma, lung tissue, and PELF samples were collected at different intervals after administration, and FF was quantified by liquid chromatographytandem mass spectrometry. After single bolus administration, FF was rapidly absorbed in plasma (the time to maximum concentration, t(max), was 1.02 h) and distributed to the respiratory tract (mean t(max) = 1.00 h). The mean t(1/2el) in plasma and lung tissue was similar, around 6 h, whereas it was slightly higher in PELF, namely, 8.7 hours. After oral bolus dosing, the mean maximum concentration in plasma was twice as high as in the lung tissue, 4.26 mu g/mL and 2.64 mu g/g, respectively, while in PELF it was much lower, 0.39 mu g/mL. During continuous drinking water medication, lung FF concentrations were slightly higher than plasma concentrations, with lung/plasma ratios of 2.01 and 1.27 after 24 h and 72 h, respectively. FF was not detected in PELF during continuous drinking water medication.