Interestingly, some dogs in the study had clinical evidence of illness (anorexia, lethargy, vomiting) despite cortisol concentrations
that may not be as low as expected. This may be because trilostane may more effectively inhibit mineralocorticoid synthesis
in this population of dogs while cortisol concentrations may be less affected.
Overall, five of the 47 dogs appeared to have adverse reactions to trilostane, but unrelated conditions may have resulted
in the illnesses. Four of the five dogs with adverse effects were receiving doses well below the manufacturer's suggested
dosing, a fact noted even in those dogs that were receiving medication three times a day. Additionally, these effects may
occur at any point during treatment as seen in those dogs that developed problems at two months, six months, and one year
after therapy was initiated.
The author of the study recommends that the goal of therapy should continue to be a post-ACTH cortisol concentration ≤ 5.5
µg/dl and urine specific gravity > 1.020 but that owner observations regarding treatment response also be considered. Trilostane
appears to be effective at lower doses than those recommended in the literature and by the manufacturer, so a lower-dose protocol
may successfully achieve a therapeutic response while decreasing the risk of adverse events. Additionally, the need to increase
dosing frequency should be considered in those dogs that have an appropriate biochemical response but are still exhibiting
Feldman EC. Evaluation of twice-daily lower-dose trilostane treatment administered orally in dogs with naturally occurring
hyperadrenocorticism. J Am Vet Med Assoc 2011;238(11):1441-1451.
This "Hot Literature" update was provided by Jennifer L. Garcia, DVM, DACVIM, a veterinary internal medicine consultant in