title: Elimination kinetics of chlorhexidine in milk following intramammary infusion to stop lactation in mastitic mammary gland quarters of cows.
abstract: OBJECTIVE
  To evaluate the elimination kinetics of chlorhexidine in milk when used as an intramammary infusion to stop lactation in cows.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  6 cows.
  
  
  METHODS
  The study was performed in 2 phases. Three cows were studied in each phase. All cows were treated with chlorhexidine suspension by infusion into a mastitic mammary gland quarter after 2 milkings 24 hours apart. Foremilk samples (100 mL) were collected from treated and untreated (controls) mammary gland quarters of each cow. Chlorhexidine was extracted from raw milk, and residue concentrations were quantified by use of high-performance liquid chromatography. Foremilk samples from days 2, 5, and 8 were analyzed in phase I, and samples from time 0 and days 3, 7, 14, 21, 28, 35, and 42 were analyzed in phase II.
  
  
  RESULTS
  In phases I and II, there was no quantifiable transference of chlorhexidine to milk in untreated mammary gland quarters. Measurable chlorhexidine residues were found in milk from treated mammary gland quarters of 2 cows throughout the 42-day sample period in phase II. Estimated mean elimination half-life for chlorhexidine in milk was 11.5 days.
  
  
  CONCLUSIONS
  On the basis of the long elimination half-life of chlorhexidine in milk from treated mammary gland quarters, the lack of human dietary exposure data to suggest a food tolerance for chlorhexidine in food products, and the Food and Drug Administration's published zero tolerance for chlorhexidine in uncooked edible calf tissues, we do not recommend extralabel use of chlorhexidine suspension as a treatment to stop lactation in mastitic mammary gland quarters of cows.
authors.affiliation: Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Middleton
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Hebert
authors.forename: Lawrence K
authors.initials: LK
authors.lastname: Fox
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tomaszewska
authors.forename: Jeff
authors.initials: J
authors.lastname: Lakritz
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002417:Cattle; D002710:Chlorhexidine / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000662:veterinary; D004350:Drug Residues / Q000032:analysis*; D005260:Female; D007774:Lactation / Q000187:drug effects; D008414:Mastitis, Bovine / Q000188:drug therapy / Q000378:metabolism*; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D011446:Prospective Studies
chemical_list: D000891:Anti-Infective Agents, Local; D002710:Chlorhexidine