title: Elimination kinetics of tilmicosin following intramammary administration in lactating dairy cattle.
abstract: OBJECTIVE
  To determine elimination kinetics of tilmicosin in milk following intramammary administration in lactating dairy cattle.
  
  
  METHODS
  Prospective pharmacokinetic study.
  
  
  METHODS
  6 lactating dairy cows.
  
  
  METHODS
  Following collection of baseline milk samples, 1,200 mg (4 mL) of tilmicosin was infused into the left front and right rear mammary glands of each cow. Approximately 12 hours later, an additional 1,200 mg of tilmicosin was infused into the left front and right rear glands after milking. Milk samples were then collected from each gland at milking time for 40 days. Concentration of tilmicosin was determined by means of ultraperformance liquid chromatography-mass spectrometry, and a milk withdrawal interval for tilmicosin was calculated on the basis of the tolerance limit method.
  
  
  RESULTS
  Although there was considerable variation between glands, concentration of tilmicosin was high in milk from treated glands and had a long half-life in treated and untreated glands. Tilmicosin was detected in all treated glands for the entire 40-day study period and was detected in untreated glands for approximately 30 to 35 days.
  
  
  CONCLUSIONS
  Findings indicated that tilmicosin should not be administered by the intramammary route in lactating dairy cows. Milk from all glands of any cows accidentally treated should be discarded for a minimum of 82 days following intramammary administration.
authors.affiliation: 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: Jennifer L
authors.initials: JL
authors.lastname: Davis
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Baynes
authors.forename: James L
authors.initials: JL
authors.lastname: Yeatts
authors.forename: Beth M
authors.initials: BM
authors.lastname: Barlow
authors.forename: Jim E
authors.initials: JE
authors.lastname: Riviere
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000662:veterinary; D004350:Drug Residues / Q000032:analysis*; D005260:Female; D007263:Infusions, Parenteral / Q000662:veterinary; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008414:Mastitis, Bovine / Q000188:drug therapy* / Q000378:metabolism; D008657:Metabolic Clearance Rate; D008892:Milk / Q000737:chemistry*; D011446:Prospective Studies; D015645:Tylosin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000032:analysis / Q000493:pharmacokinetics
chemical_list: D000900:Anti-Bacterial Agents; C052319:tilmicosin; D015645:Tylosin