(EN26) Relationship Between Post ACTH Cortisol Concentration at Diagnosis and Dose of Trilostane in Small-breed Dogs

Abstract:

Background: Only few studies have evaluated the initiation dose and frequency of trilostane medication in small-breed dogs. Further, little is known about the factors that may influence the dose of trilostane required for clinical improvement.

Objectives: This study aimed to investigate the correlation between post-ACTH cortisol concentration at diagnosis and the optimal trilostane dose in small-breed dogs with hyperadrenocorticism.
Animals: Small-breed dogs (n=68, weighing less than 20 kg) diagnosed with hyperadrenocorticism by adrenocorticotropic hormone (ACTH) stimulation test were included. The dogs were given trilostane after diagnosis (starting dose: 1 mg/kg q 12 hr), and the ACTH stimulation test was performed periodically to monitor treatment response. Stable state was defined as having post-ACTH cortisol concentration within 2.0–9.0 µg/dL and clinical improvement. The dose of trilostane in the stable state was regarded as the optimal dose.

Methods: retrospective study

Results: A positive correlation was observed between post-ACTH cortisol concentration at diagnosis and the optimal dose. However, in 61 of 68 dogs, the optimal dose was less than 2.5 mg/kg q 12 hr, which slightly exceeds the authors’ starting dose. Therefore, it is not clinically significant to determine the initial dose of trilostane in proportion to the post-ACTH cortisol concentration at diagnosis.
Conclusions and clinical importance: Starting at a low dose of 1 mg/kg q 12 hr regardless of post-ACTH cortisol concentration at diagnosis is desirable to reach the optimal dose to reduce the side effects caused by trilostane in small-breed dogs.