Evaluation of 2 Trilostane Protocols for the Treatment of Canine Pituitary‐Dependent Hyperadrenocorticism: Twice Daily versus Once Daily

Background Trilostane is the drug of choice to treat pituitary‐dependent hyperadrenocorticism ( PDH ) in dogs, but there is still controversy about which protocol best controls the clinical signs and results of adrenal functioning test. Objectives To compare the efficacy of twice daily ( BID ) versus once daily ( SID ) trilostane administration and to compare the safety of both protocols in the treatment of dogs with PDH . Animals Thirty‐two client‐owned dogs diagnosed with PDH between 2008 and 2010 and treated with trilostane either BID or SID . Methods In this prospective randomized study, 2 trilostane protocols were evaluated on the basis of the owner′s perception of clinical signs, on the results of laboratory tests, and on the results of the ACTH stimulation test in dogs with PDH . Dogs were followed up for a period of 1 year. Results During the study, more dogs in the BID group had complete clinical recovery than in the SID group. However, there was no significant difference in the mean post‐ ACTH cortisol concentration between groups. Basal cortisol concentration at 6 months was higher in animals treated SID compared with animals treated BID . Mean total daily doses of trilostane used to control PDH , as well as adverse effects observed in the course of the study, in both groups were not statistically different. Conclusion and Clinical Importance Adverse effects were mild using either protocol of treatment. Using trilostane BID might increase the number of dogs with a good clinical response compared with using trilostane SID .