Florfenicol pharmacokinetics in lactating cows after intravenous, intramuscular and intramammary administration

Pharmacokinetics of florfenicol 30% injectable solution was determined in lactating cows after intravenous, intramammary and intramuscular administration, Serum concentration-time data generated in the present study were analysed by non-compartmental methods based on statistical moment theory. Florfenicol half-life was 176 min, mean residence time 129 min, volume of distribution at steady-state 0.35 L/kg, and total body clearance 2.7 mL/min kg after intravenous administration at 20 mg/kg. The absorption after intramuscular administration appeared slow and the kinetic parameters and the serum concentration vs, time curve were characteristic of absorption rate-dependent elimination, The absorption after intramammary administration of florfenicol at 20 mg/kg was good (53.9%) and resulted in serum concentrations with apparent clinical significance, The intramammary administration resulted in serum florfenicol concentrations that were significantly higher than the respective serum concentrations following intravenous administration 4 h after administration and thereafter. Florfenicol absorption was faster from the mammary gland than from the muscle, The maximum serum concentrations (C-max) were 6.9 mu g/mL at 360 min after intramammary administration and 2.3 mu g/mL at 180 min after intramuscular administration, The bioavailability of florfenicol was 54% and 38% after intramammary and intramuscular administration, respectively, The C-max in milk was 5.4 mu g/mL at 180 min after intravenous and 1.6 mu g/mL at 600 min after intramuscular administratio