The influence of the site of drug administration on florfenicol pharmacokinetics in turkeys

Florfenicol is a broad-spectrum antibacterial drug used in the treatment of farm animals, including poultry. This drug is poorly soluble in water, therefore, administration in drinking water may lead to high variability of concentrations in treated individuals. The use of injection preparations, however, requires individual administration and may have a negative effect on the quality of the carcass. In addition, the renal portal system in birds may reduce the bioavailability of the drug administered in the caudofemoral region of the body. The aim of this study was to compare the pharmacokinetics of florfenicol in turkeys after a single intravenous, intramuscular, and subcutaneous administration at a dose of 15 mg/kg body weight. Additionally, to evaluate the effect of renal portal system on drug kinetics, the intramuscular administration was divided into pectoral and caudofemoral administration. The study showed that the area under the concentration-time curve (AUC) was similar regardless of the route of administration. The mean values for clearance and volume of distribution were 0.33 L/kg/h and 0.92 L/kg, respectively. The mean residence time (MRT) was 2.87 h for an intravenous bolus, while for the extravascular administrations it was approx. 5.5 h. The elimination half-life was approx. 4 h regardless of the route of administration. The maximum plasma concentration did not differ statistically between intramuscular (approx. 6.8 mg/L) and subcutaneous (8.2 mg/L) administrations, while the time to appear for this concentration was the longest for caudofemoral administration (1.5 h). The bioavailability was 88.64% for subcutaneous administration, 77.95% for pectoral administration and 85.30% for caudofemoral administration. Overall, all 3 routes of extravascular administration allowed for efficient drug absorption. There was no evidence of an influence of the renal portal system on the kinetic parameters of the drug administered to the lower extremities of the body.