title: Disposition of gamithromycin in plasma, pulmonary epithelial lining fluid, bronchoalveolar cells, and lung tissue in cattle.
abstract: OBJECTIVE
  To determine the disposition of gamithromycin in plasma, pulmonary epithelial lining fluid (PELF), bronchoalveolar lavage (BAL) cells, and lung tissue homogenate in cattle.
  
  
  METHODS
  33 healthy Angus calves approximately 7 to 8 months of age.
  
  
  METHODS
  Calves were randomly assigned to 1 of 11 groups consisting of 3 calves each, which differed with respect to sample collection times. In 10 groups, 1 dose of gamithromycin (6 mg/kg) was administered SC in the neck of each calf (0 hours). The remaining 3 calves were not treated. Gamithromycin concentrations in plasma, PELF, lung tissue homogenate, and BAL cells (matrix) were measured at various points by means of high-performance liquid chromatography with tandem mass spectrometry.
  
  
  RESULTS
  Time to maximum gamithromycin concentration was achieved at 1 hour for plasma, 12 hours for lung tissue, and 24 hours for PELF and BAL cells. Maximum gamithromycin concentration was 27.8 μg/g, 17.8 μg/mL, 4.61 μg/mL, and 0.433 μg/mL in lung tissue, BAL cells, PELF, and plasma, respectively. Terminal half-life was longer in BAL cells (125.0 hours) than in lung tissue (93.0 hours), plasma (62.0 hours), and PELF (50.6 hours). The ratio of matrix to plasma concentrations ranged between 4.7 and 127 for PELF, 16 and 650 for lung tissue, and 3.2 and 2,135 for BAL cells.
  
  
  CONCLUSIONS
  Gamithromycin was rapidly absorbed after SC administration. Potentially therapeutic concentrations were achieved in PELF, BAL cells, and lung tissue within 30 minutes after administration and persisted for 7 (PELF) to > 15 (BAL cells and lung tissue) days after administration of a single dose.
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA. gigueres@uga.edu
authors.forename: Steeve
authors.initials: S
authors.lastname: Giguère
authors.forename: Rose
authors.initials: R
authors.lastname: Huang
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Malinski
authors.forename: Paul M
authors.initials: PM
authors.lastname: Dorr
authors.forename: Ronald K
authors.initials: RK
authors.lastname: Tessman
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Somerville
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002417:Cattle; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D008168:Lung / Q000378:metabolism*; D018942:Macrolides / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; C552399:gamithromycin