The effect of orally administered
ketoconazole on plasma
cortisol concentration in dogs with
hyperadrenocorticism was evaluated. Every 30 minutes from 0800 hours through 1600 hours and again at 1800 hours, 2000 hours, and 0800 hours the following morning, 15 clinically normal dogs and 49 dogs with
hyperadrenocorticism had plasma samples obtained and analyzed for
cortisol concentration. The mean (+/- SD) plasma
cortisol concentration for the initial 8-hour testing period was highest in 18 dogs with adrenocortical
tumor (5.3 +/- 1.6 micrograms/dl), lowest in 15 control dogs (1.3 +/- 0.5 micrograms/dl), and intermediate in 31 dogs with pituitary-dependent
hyperadrenocorticism (PDH; 3.4 +/- 1.2 micrograms/dl). Results in each of the 2 groups of dogs with
hyperadrenocorticism were significantly (P less than 0.05) different from results in control dogs, but not from each other. The same
cortisol secretory experiment was performed, using 8 dogs with
hyperadrenocorticism (5 with PDH; 3 with adrenocortical
tumor) before and after administration at 0800 hours of 15 mg of
ketoconazole/kg of
body weight. Significant (P less than 0.05) decrease in the 8-hour mean plasma
cortisol concentration (0.9 +/- 0.2 microgram/dl) was observed, with return to baseline plasma
cortisol concentration 24 hours later. Twenty dogs with
hyperadrenocorticism (11 with PDH, 9 with adrenocortical
tumor) were treated with
ketoconazole at a dosage of 15 mg/kg given every 12 hours for a half month to 12 months. The disease in 2 dogs with PDH failed to respond to treatment, but 18 dogs had complete resolution of clinical signs of
hyperadrenocorticism and significant (P less than 0.05) reduction in plasma
cortisol responsiveness to exogenous
adrenocorticotropin (
ACTH).(ABSTRACT TRUNCATED AT 250 WORDS)