Trilostane: the dog drinks heavily again in the evening. What next?
11-year-old Maltese with pituitary-dependent hyperadrenocorticism on once-daily morning trilostane for 2 months. He has improved, but the owner notices that in the evening and at night he drinks and begs for food again. He is bright, eating well and electrolytes are normal.
What is the most reasonable adjustment?
chevron_right Show answer and explanation
A. Switch to mitotane, because trilostane has failed
This is not a failure: the dog responds, but the effect does not last 24 hours. Mitotane carries more risks and is not justified here.
B. Double the morning dose
A larger single dose produces a deeper peak of suppression (more risk of hypocortisolism) without much lengthening of the effect.
C. Keep the same regimen: evening signs are not clinically relevant
The goal of treatment is to control the signs that bother the owner and the dog; nocturnal polyuria and polyphagia indicate inadequate control.
D. Split the trilostane into two daily doses, every 12 hours, with food
Correct. In many dogs the effect of trilostane lasts less than 24 hours. Splitting the dose into two daily doses usually gives better control with a similar or lower total dose, then adjusted on signs and cortisol.
lightbulb Key takeaway
If a dog on trilostane improves but signs return late in the day, think of the short duration of effect: move to twice-daily dosing rather than increasing a single dose. Always check electrolytes and cortisol at rechecks.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.