title: Florfenicol pharmacokinetics in lactating cows after intravenous, intramuscular and intramammary administration.
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 (Cmax) were 6.9 micrograms/mL at 360 min after intramammary administration and 2.3 micrograms/mL at 180 min after intramuscular administration. The bioavailability of florfenicol was 54% and 38% after intramammary and intramuscular administration, respectively. The Cmax in milk was 5.4 micrograms/mL at 180 min after intravenous and 1.6 micrograms/mL at 600 min after intramuscular administration.
authors.affiliation: National Residue Control Laboratory, Kimron Veterinary Institute, Beit Dagan, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Soback
authors.forename: M J
authors.initials: MJ
authors.lastname: Paape
authors.forename: R
authors.initials: R
authors.lastname: Filep
authors.forename: K J
authors.initials: KJ
authors.lastname: Varma
mesh_terms: D000042:Absorption; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D001682:Biological Availability; D002417:Cattle / Q000378:metabolism*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006207:Half-Life; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism; D008892:Milk / Q000378:metabolism; D013839:Thiamphenicol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics
chemical_list: D000900:Anti-Bacterial Agents; C035534:florfenicol; D013839:Thiamphenicol