Study suggests most single-dose trilostane ingestions stay mild: full analysis

A new toxicology case series may offer some reassurance for clinicians fielding urgent calls about trilostane mishaps. In a retrospective review of 403 dogs reported to the ASPCA Animal Poison Control Center between 2008 and 2023, investigators found that accidental ingestion of a single unintended trilostane dose was usually followed by mild, self-limiting clinical signs and minimal need for intensive veterinary treatment. The study was published in the Journal of Veterinary Emergency and Critical Care. (pmc.ncbi.nlm.nih.gov)

That question comes up often in practice because trilostane is a mainstay treatment for canine hyperadrenocorticism, and many of the affected patients are older dogs on multiple medications. Trilostane works by inhibiting 3β-hydroxysteroid dehydrogenase, reducing glucocorticoid production and, to a lesser extent, mineralocorticoids and sex hormones. Because of that mechanism, the concern after an overdose or extra dose isn’t just GI upset, but excessive adrenal suppression and, in more serious cases, an Addisonian-type crisis. (todaysveterinarypractice.com)

Regulatory and reference sources underscore why this topic matters. The FDA approval file for Vetoryl describes healthy-dog safety studies in which high repeated doses caused significant morbidity and mortality consistent with hypoadrenocorticism, while the current product labeling warns that in case of overdosage, symptomatic treatment with corticosteroids, mineralocorticoids, and IV fluids may be required. The label also notes that serious adverse reactions can occur without warning, and that pet parents should be told to stop therapy and contact their veterinarian immediately if vomiting, diarrhea, lethargy, weakness, collapse, or reduced appetite develop. (animaldrugsatfda.fda.gov)

At the same time, prior literature has suggested that the pharmacologic effect of trilostane is often transient after routine dosing, with plasma concentrations peaking roughly 1.7 to 3.8 hours after administration and returning to baseline by about 12 hours. Review articles also note that while many adverse effects are reversible after stopping the drug, prolonged adrenocortical suppression, permanent hypoadrenocorticism, and adrenal necrosis have all been reported, even if they’re uncommon. That backdrop makes the new 403-case series useful: it helps separate the theoretical worst-case scenario from what poison control data suggest usually happens after a one-time accidental exposure. (pmc.ncbi.nlm.nih.gov)

Direct outside commentary on this specific paper was limited in the public record at the time of writing, but the broader clinical consensus is familiar. Toxicology and internal medicine references consistently frame trilostane exposure as a case that should be assessed promptly, while also recognizing that management depends on the amount ingested, the dog’s size, timing, and whether clinical signs are present. General veterinary toxicology guidance supports early decontamination only in appropriate recent ingestions, rather than reflexively applying it to every case. (merckvetmanual.com)

Why it matters: For veterinary professionals, this study could help reduce unnecessary escalation while still supporting careful risk assessment. If most single unintended doses lead to mild, self-limited signs, that gives ER and primary care teams better footing for counseling pet parents, prioritizing monitoring, and reserving aggressive care for dogs with higher exposures, comorbidities, or signs of adrenal suppression. It may also help standardize poison-control-informed protocols for common medication errors in dogs being treated chronically for Cushing’s disease. (pmc.ncbi.nlm.nih.gov)

There’s also a practical communication angle. Trilostane’s label already places heavy emphasis on close monitoring during treatment adjustments and on rapid response to adverse signs. A study like this can help clinics refine discharge instructions and callback protocols for pet parents who suspect an extra dose, especially since the difference between a watch-and-wait case and a true emergency may depend on signalment, dose exposure, and evolving signs rather than the ingestion alone. (todaysveterinarypractice.com)

What to watch: The next step is whether the full publication provides more granular exposure thresholds, timing data, and treatment-outcome correlations that clinicians can translate into triage algorithms for same-day calls and ER referrals. (pmc.ncbi.nlm.nih.gov)