title: Elimination kinetics of ceftiofur hydrochloride after intramammary administration in lactating dairy cows.
abstract: OBJECTIVE
  To determine the elimination kinetics of ceftiofur hydrochloride in milk after intramammary administration in lactating dairy cows.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  5 lactating dairy cows.
  
  
  METHODS
  After collection of baseline milk samples, 300 mg (6 mL) of ceftiofur was infused into the left front and right rear mammary gland quarters of each cow. Approximately 12 hours later, an additional 300 mg of ceftiofur was administered into the same mammary gland quarters after milking. Milk samples were collected from each mammary gland quarter every 12 hours for 10 days. Concentrations of ceftiofur and its metabolites in each milk sample were determined to assess the rate of ceftiofur elimination.
  
  
  RESULTS
  Although there were considerable variations among mammary gland quarters and individual cows, ceftiofur concentrations in milk from all treated mammary gland quarters were less than the tolerance (0.1 microg/mL) set by the FDA by 168 hours (7 days) after the last intramammary administration of ceftiofur. No drug concentrations were detected in milk samples beyond this period. Ceftiofur was not detected in any milk samples from nontreated mammary gland quarters throughout the study.
  
  
  CONCLUSIONS
  Ceftiofur administered by the intramammary route as an extra-label treatment for mastitis in dairy cows reaches concentrations in milk greater than the tolerance set by the FDA. Results indicated that milk from treated mammary gland quarters should be discarded for a minimum of 7 days after intramammary administration of ceftiofur. Elimination of ceftiofur may be correlated with milk production, and cows producing smaller volumes of milk may have prolonged withdrawal times.
authors.affiliation: Food Animal Residue Avoidance Databank, Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA.
authors.forename: Geof W
authors.initials: GW
authors.lastname: Smith
authors.forename: Ronette
authors.initials: R
authors.lastname: Gehring
authors.forename: Jim E
authors.initials: JE
authors.lastname: Riviere
authors.forename: James L
authors.initials: JL
authors.lastname: Yeatts
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Baynes
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D002417:Cattle; D002511:Cephalosporins / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D004350:Drug Residues / Q000032:analysis*; D005260:Female; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008414:Mastitis, Bovine / Q000188:drug therapy*; D008892:Milk / Q000737:chemistry*; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic / Q000662:veterinary
chemical_list: D000891:Anti-Infective Agents, Local; D002511:Cephalosporins; D011933:Reagent Kits, Diagnostic; C053503:ceftiofur