Effect of low doses of cosyntropin on serum cortisol concentrations in clinically normal dogs.
OBJECTIVE
To determine the lowest of 5 doses of cosyntropin (1.0, 0.5, 0.1, 0.05, or 0.01 microg/kg) administered IV that stimulates maximal cortisol secretion in clinically normal dogs.


METHODS
10 clinically normal dogs.


METHODS
5 dose-response experiments were performed in each of the dogs. Each dog received 5 doses of cosyntropin (1.0, 0.5, 0.1, 0.05, and 0.01 microg/kg) IV in random order (2-week interval between each dose). Serum samples for determination of cortisol concentrations were obtained before (baseline) and at 10, 20, 30, 40, 50, 60, 120, and 240 minutes after cosyntropin administration.


RESULTS
Compared with baseline values, mean serum cortisol concentration in the study dogs increased significantly after administration of each of the 5 cosyntropin doses. Mean peak serum cortisol concentration was significantly lower after administration of 0.01, 0.05, and 0.1 microg of cosyntropin/kg, compared with findings after administration of 0.5 and 1.0 microg of cosyntropin/kg. After administration of 0.5 and 1.0 microg of cosyntropin/kg, mean peak serum cortisol concentration did not differ significantly; higher doses of cosyntropin resulted in more sustained increases in serum cortisol concentration, and peak response developed after a longer interval.


CONCLUSIONS
Administration of cosyntropin IV at a dose of 0.5 microg/kg induced maximal cortisol secretion in healthy dogs. Serum cortisol concentration was reliably increased in all dogs after the administration of each of the 5 doses of cosyntropin. These data should be useful in subsequent studies to evaluate the hypothalamic-pituitary-adrenal axis in healthy and critically ill dogs.
Martin
Linda G
LG
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6610.
Behrend
Ellen N
EN
Mealey
Katrina L
KL
Carpenter
D Mark
DM
Hickey
Kathy C
KC
D000818:Animals; D003366:Cosyntropin / Q000008:administration & dosage* / Q000494:pharmacology*; D004285:Dogs / Q000097:blood* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006262:Health; D006854:Hydrocortisone / Q000097:blood*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D003366:Cosyntropin; D006854:Hydrocortisone