Pharmacokinetics of florfenicol and its metabolite florfenicol amine in the plasma, urine, and feces of fattening male donkeys following single oral administration.

Florfenicol (FF) is a commonly used antibacterial agent in animals. We investigated the pharmacokinetics of FF and its metabolite florfenicol amine (FFA) in donkeys. Donkeys were administered FF (30 mg/kg bodyweight, p.o.). Pharmacokinetic parameters were calculated using a non-compartmental model. The FF (FFA) pharmacokinetics parameters were characterized by along elimination half-life () of 5.92 h (15.95 h), plasma peak concentration () of 0.13 μg/mL (0.08 μg/mL), and the time taken to reach () of 0.68 h (0.72 h). The area under plasma concentration-time curve and mean residence time of FF (FFA) in plasma were 1.31 μg·mL·h (0.47 μg·mL·h) and 10.37 h (18.40 h), respectively. The of FF and FFA in urine was 21.93 and 40.26 h, and the maximum excretion rate was 10.56 and 4.03 μg/h reached at 25.60 and 32.20 h, respectively. The respective values in feces were 0.02 and 0.01 μg·h reached at 33.40 h. The amount of FF and FFA recovered in feces was 0.52 and 0.22 μg, respectively. In conclusion, FF (FFA) is rapidly absorbed and slowly eliminated after a single oral administration to donkeys. Compared to FF, FFA was more slowly eliminated. FF (FFA) is mostly excreted through urine.