Florfenicol pharmacokinetics in lactating cows after intravenous, intramuscular and intramammary administration |
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| Authors: | S SOBACK † MJ PAAPE† R FILEP† KJ VARMA‡ |
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| Institution: | *Kimron Veterinary Institute, National Residue Control Laboratory, PO Box 12, 50250 Beit Dagan, Israel;?Milk Secretion and Mastitis Laboratory, USDA/ARS, Beltsvilh, 20705 MD, USA;?Schering-Plough Corporation, PO Box 3182, Union 07083–1982, NJ, USA |
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| Abstract: | 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 μg/mL at 360 min after intramammary administration and 2.3 μg/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 μg/mL at 180 min after intravenous and 1.6 μg/mL at 600 min after intramuscular administration. |
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