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 a dministration, 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 b ody clearance 2.7 mL/min kg after intravenous administration at 20 mg/ kg. The absorption after intramuscular administration appeared slow an d the kinetic parameters and the serum concentration vs, time curve we re characteristic of absorption rate-dependent elimination, The absorp tion after intramammary administration of florfenicol at 20 mg/kg was good (53.9%) and resulted in serum concentrations with apparent clinic al significance, The intramammary administration resulted in serum flo rfenicol concentrations that were significantly higher than the respec tive serum concentrations following intravenous administration 4 h aft er administration and thereafter. Florfenicol absorption was faster fr om the mammary gland than from the muscle, The maximum serum concentra tions (C-max) were 6.9 mu g/mL at 360 min after intramammary administr ation and 2.3 mu g/mL at 180 min after intramuscular administration, T he bioavailability of florfenicol was 54% and 38% after intramammary a nd 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 aft er intramuscular administration.