Laboratory assessment of trilostane treatment in dogs with pituitary-dependent hyperadrenocorticism.

Abstract

BACKGROUND: Results of ACTH stimulation test (ACTHst), pre- and post-trilostane serum cortisol concentrations (SCCs), urine concentration (urine-specific gravity [USG]), and urine cortisol : creatinine ratios (UCCRs) are common variables used to monitor trilostane treatment of dogs with pituitary-dependent hyperadrenocorticism (PDH). However, none has consistently discriminated dogs receiving an adequate dose (A) from those overdosed (O) or underdosed (U). OBJECTIVES: To assess and compare recommended monitoring variables, including serial SCCs in a cohort of dogs with PDH treated with trilostane. ANIMALS: Privately owned dogs with PDH (n = 22) and 3 healthy dogs (controls). METHODS: Prospective, multicenter, 2-day study. On day "a" (randomized): ACTHst was completed. Day "b" (>2 to <7&#x2009;days later): SCCs were assessed -0.5 hours, immediately before, and 1, 2, 2.5, 3, 3.5, 4, 6, 8, and 12&#x2009;hours after trilostane administration. On the first study day, urine collected at home was assessed for USG, UCCR and owner opinions regarding PDH were categorized as: A (clinical signs resolved), U (remains symptomatic), or ill (possible O). RESULTS: At 27 pairs of evaluations, 7 dogs were categorized as A, 19&#x2009;U, and 1 possible O (excluded from the study). There was overlap in SCC results from the A and U dogs at every time point. Results of USG, UCCR, and ACTHst did not discriminate A from U dogs. Trilostane suppresses SCC within 1 hour of administration and its duration of action in most PDH dogs is <8 hours. CONCLUSIONS AND CLINICAL IMPORTANCE: No single variable or group of variables reliably discriminated A dogs from U dogs during trilostane treatment for PDH.