The aim was to identify a reliable parameter for determining appropriate trilostane dose adjustments in dogs being treated for pituitary dependent hyperadrenocorticism (PDH). Eighteen dogs with PDH being treated with trilostane twice daily were prospectively included. Two evaluations were made within a week. Dogs were evaluated alternately, with “day a” first or “day b” first. Day “a” included obtaining a history, complete blood count, serum biochemistry, and completing an ACTH stimulation test (2 hours post-trilostane administration). Day “b” included obtaining blood for serum cortisol concentrations (SCC) 30 minutes prior to trilostane administration (-30), immediately before (0), and then 1, 2, 2.5, 3, 3.5, 4, 6, 8 and 12 hours after. The mean (±SD) SCC at each time point for the 18 dogs were 3.8 ±2.1; 3.9 ±1.4; 3.9 ±2.1; 2.1 ±1.3; 2.8 ±1.6; 2.8 ±1.6; 3.3 ±1.7; 3.3 ±1.8; 3.7 ±1.3; 3.6 ±1.5; 3.9 ±1.7µg/dL, respectively. The lowest mean SCC for the group was at 2.5 hours. Mean SCCs at -30, 0, 1, 6, 8, and 12 hours were not significantly different from each other. These were significantly higher than mean SCCs at 2, 2.5, 3, 3.5 and 4 hours.
No single criterion or SCC at a time point post-trilostane administration was consistently helpful in determining whether or not a dog required a dose adjustment. SCC taken -30 or 0 time were not helpful in identifying well controlled (WC) from poor controlled (PC) dogs. No single time point after trilostane administration was consistently helpful in identifying WC from PC dogs.
Boretti FS, Holzthüm J, Reusch CE, et al. Lack of associa- tion between clinical signs and laboratory parameters before and during trilostane treatment. Schweiz Arch Tierheilkd. 2016 Sep; 158(9):631-638.
Burkhardt WA, Boretti FS, Reusch CE, et al. Evaluation of baseline cortisol, endogenous ACTH, and cortisol/ ACTH ratio to monitor trilostane treatment in dogs with pituitary-dependent hypercortisolism. J Vet Intern Med. 2013 Jul-Aug; 27(4):919-23.
Macfarlane L, Parkin T, Ramsey I. Pre-trilostane and three- hour post-trilostane cortisol to monitor trilostane thera- py in dogs.Vet Rec. 2016 Dec 10; 179(23):597.