We compared the cortisol response to 1 and 5 μg/kg Cosyntropin IV in dogs being screened for hyperadrenocorticism (HAC) and in dogs receiving Trilostane or Mitotane for pituitary-dependent HAC. Lowering the Cosyntropin dose needed for ACTH stimulation would make the test more economical. In this study, healthy dogs, client-owned dogs suspected of having  HAC or being treated for pituitary-dependent HAC with Mitotane or Trilostane had two ACTH stimulation tests. For the first test, Cosyntropin (1 μg/kg IV) was administered; the second test was initiated 4 hours after the start of the first (5 μg/kg Cosyntropin IV). For dogs suspected of having HAC, 5 μg/kg Cosyntropin IV is still recommended for ACTH stimulation testing. For dogs receiving Mitotane or Trilostane treatment, a dose of 1 μg/kg

Cosyntropin IV can be used.