Trilostane monitoring: low cortisol in a lethargic dog
10-year-old Maltese with pituitary-dependent hyperadrenocorticism, on trilostane for 3 weeks. For 2 days it has been lethargic, anorexic and vomiting. The ACTH test was done 4 h after dosing.
| Parameter | Result | Reference |
|---|---|---|
| Post-ACTH cortisol | 0.6 µg/dL | Target 1.45–5.4 |
| Sodium | 135 mEq/L | 144–154 |
| Potassium | 6.4 mEq/L | 3.6–5.5 |
What should you do?
chevron_right Show answer and explanation
A. Keep the dose: a low post-ACTH cortisol indicates good control
A post-ACTH cortisol below target, with clinical signs and electrolyte changes, is not good control but adrenal insufficiency.
B. Reduce the dose by 25% and recheck in 2 weeks
A dose reduction might be reasonable in a well dog with slightly low cortisol, but not in one with signs of hypoadrenocorticism and hyperkalaemia, which needs the drug stopped and treatment now.
C. Stop trilostane and treat iatrogenic hypoadrenocorticism
Correct. Very low post-ACTH cortisol, hyponatraemia, hyperkalaemia and gastrointestinal signs indicate hypocortisolism, here with mineralocorticoid deficiency too. Stop the drug, treat with fluids and glucocorticoids (and mineralocorticoids if the electrolyte disturbance persists) and reassess before restarting: adrenal necrosis may occur and be long-lasting.
D. Treat gastroenteritis with antiemetics and continue trilostane
Attributing the signs to gastroenteritis is a common mistake. The combination of very low cortisol and sodium and potassium changes points to the drug.
lightbulb Key takeaway
Trilostane is adjusted according to clinical signs and cortisol (post-ACTH or pre-pill, depending on the protocol). Warn owners: if the dog becomes lethargic, vomits or stops eating, they must stop the drug and come in; always measure electrolytes.
Test yourself with 10 random questions
Clinical pathology · 100 questions, a different test every time
Related questions
Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.