Evaluation of twice-daily, low-dose trilostane treatment administered orally in dogs with naturally occurring hyperadrenocorticism.
OBJECTIVE
To evaluate the effects of twice-daily oral administration of a low-dose of trilostane treatment and assess the duration of effects after once-daily trilostane administration in dogs with naturally occurring hyperadrenocorticism (NOH).


METHODS
Prospective study.


METHODS
28 dogs with NOH.


METHODS
22 dogs received 0.5 to 2.5 mg of trilostane/kg (0.23 to 1.14 mg/lb) orally every 12 hours initially. At intervals, dogs were reevaluated; owner assessment of treatment response was recorded. To assess drug effect duration, 16 of the 22 dogs and 6 additional dogs underwent 2 ACTH stimulation tests 3 to 4 hours and 8 to 9 hours after once-daily trilostane administration.


RESULTS
After 1 to 2 weeks, mean trilostane dosage was 1.4 mg/kg (0.64 mg/lb) every 12 hours (n = 22 dogs; good response [resolution of signs], 8; poor response, 14). Four to 8 weeks later, mean dosage was 1.8 mg/kg (0.82 mg/lb) every 12 or 8 hours (n = 21 and 1 dogs, respectively; good response, 15; poor response, 5; 2 dogs were ill). Eight to 16 weeks after the second reevaluation, remaining dogs had good responses (mean dosages, 1.9 mg/kg [0.86 mg/lb], q 12 h [n = 13 dogs] and 1.3 mg/kg [0.59 mg/lb], q 8 h [3]). At 3 to 4 hours and 8 to 9 hours after once-daily dosing, mean post-ACTH stimulation serum cortisol concentrations were 2.60 and 8.09 Pg/dL, respectively.


CONCLUSIONS
In dogs with NOH, administration of trilostane at low doses every 12 hours was effective, although 2 dogs became ill during treatment. Drug effects diminished within 8 to 9 hours. Because of potential adverse effects, lower doses should be evaluated.
Vaughan
Matthew A
MA
Veterinary Medical Teaching Hospital and the Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Feldman
Edward C
EC
Hoar
Bruce R
BR
Nelson
Richard W
RW
D000284:Administration, Oral; D000308:Adrenocortical Hyperfunction / Q000097:blood / Q000188:drug therapy / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D001774:Blood Chemical Analysis; D013196:Dihydrotestosterone / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D004283:Dog Diseases / Q000097:blood / Q000188:drug therapy*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule / Q000662:veterinary; D004791:Enzyme Inhibitors / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D005260:Female; D008297:Male; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome
D004791:Enzyme Inhibitors; D013196:Dihydrotestosterone; D000324:Adrenocorticotropic Hormone; C009954:trilostane