title: Effect of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs.
abstract: OBJECTIVE
  To determine the effects of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs.
  
  
  METHODS
  10 healthy neutered dogs.
  
  
  METHODS
  Each dog received dexamethasone (0.01 mg/kg), synthetic ACTH (5 μg/kg), or saline (0.9% NaCl) solution (0.5 mL) IV at intervals of ≥ 30 days. Plasma endogenous ACTH concentrations were measured before (baseline; time 0) and 1, 8, 12, and 24 hours after drug administration; serum cortisol concentrations were measured before and 1 hour after synthetic ACTH and saline solution administration and 8 hours after dexamethasone administration.
  
  
  RESULTS
  Analysis of serum cortisol concentrations confirmed effects of drug administration. Dexamethasone significantly decreased the endogenous ACTH concentration from the baseline value at both 8 and 12 hours. Synthetic ACTH administration significantly decreased the endogenous ACTH concentration from the baseline value at 8 hours. Saline solution administration had no significant effect on endogenous ACTH concentration.
  
  
  CONCLUSIONS
  Dexamethasone and synthetic ACTH administered IV at doses used routinely during testing for hyperadrenocorticism caused significant but transient reductions of endogenous ACTH concentrations in healthy dogs. Thus, a 2-hour washout period following ACTH stimulation testing before collection of samples for measurement of the endogenous ACTH concentration may be insufficient. Although this effect has not been verified in dogs with hyperadrenocorticism, these data suggested that samples for measurement of endogenous ACTH concentrations should be obtained before or > 8 hours after initiation of an ACTH stimulation test or before or > 12 hours after the start of a low-dose dexamethasone suppression test.
authors.affiliation: Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Bugbee
authors.forename: Jo R
authors.initials: JR
authors.lastname: Smith
authors.forename: Cynthia R
authors.initials: CR
authors.lastname: Ward
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000008:administration & dosage / Q000097:blood*; D000818:Animals; D003366:Cosyntropin / Q000008:administration & dosage / Q000097:blood*; D018592:Cross-Over Studies; D003907:Dexamethasone / Q000008:administration & dosage / Q000097:blood*; D004285:Dogs / Q000378:metabolism*; D005260:Female; D007275:Injections, Intravenous / Q000662:veterinary; D008163:Luminescent Measurements / Q000662:veterinary; D008297:Male
chemical_list: D003366:Cosyntropin; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone