Trilostane for Dogs: Uses, Side Effects & Dosage for Cushing's Disease Management
Trilostane is a medication that veterinarians discuss for the management of hyperadrenocorticism, commonly known as Cushing's disease, in dogs. It is available as the FDA-approved commercial product VetORYL and through compounded formulations at veterinary pharmacies like Mixlab. Trilostane requires a valid prescription, careful dose individualization and regular monitoring through ACTH stimulation testing to ensure both safety and appropriate management of the underlying condition.
What Is Cushing's Disease in Dogs and Why Is Trilostane Discussed?
Hyperadrenocorticism, also known as Cushing's disease, occurs when the adrenal glands produce excess cortisol. In dogs, the most common form is pituitary-dependent, meaning the overproduction is driven by a small tumor on the pituitary gland that signals the adrenal glands to overproduce. A less common form involves a tumor directly on one of the adrenal glands.
Excess cortisol affects multiple organ systems, and dogs with Cushing's disease often present with a cluster of signs that develop gradually over months or years. A veterinarian who suspects Cushing's disease will pursue specific diagnostic testing, including urine cortisol-to-creatinine ratio, low-dose dexamethasone suppression testing or ACTH stimulation testing, before beginning any management approach.
Trilostane works by inhibiting an enzyme involved in the production of cortisol in the adrenal gland. In doing so, it can reduce the amount of cortisol the body produces, a key goal of Cushing's disease management.
What Signs Lead Veterinarians to Evaluate a Dog for Cushing's Disease?
Dogs with hyperadrenocorticism commonly exhibit increased thirst and urination, increased appetite, a pot-bellied appearance, hair loss on the trunk, thinning skin and reduced activity. Because these signs can overlap with other conditions, including diabetes, kidney disease and hypothyroidism, the diagnostic workup is an important step before any treatment discussion begins.
Cushing's disease is most commonly diagnosed in middle-aged to older dogs, and certain breeds including Poodles, Dachshunds, Boxers and Yorkshire Terriers appear to be overrepresented. That said, the condition can affect any breed, and veterinarians evaluate each case individually.
The decision to begin trilostane is made after diagnosis is confirmed and after a discussion between the veterinarian and the dog's owner about the dog's overall health status and the goals of management.
What Are the Side Effects of Trilostane for Dogs?
Trilostane's primary mechanism, reducing cortisol production, also introduces the main risk associated with its use: insufficient cortisol, or hypoadrenocorticism. Because cortisol is essential for normal physiologic function, a dog who produces too little can experience lethargy, loss of appetite, vomiting, diarrhea and, in serious cases, an addisonian crisis. This is why ACTH stimulation testing is not optional. It is the primary tool veterinarians use to confirm that cortisol levels remain in an appropriate range.
Less serious effects observed when trilostane is first started can include mild lethargy, reduced appetite or loose stool in the first days of therapy. These are commonly transient, but owners are typically asked to monitor closely and contact their veterinarian if symptoms persist or worsen.
Any dog on trilostane who develops sudden lethargy, vomiting, weakness or refusal to eat should be seen by a veterinarian promptly. These signs may indicate the cortisol level has dropped too low and require immediate evaluation.
Why Does Trilostane Require Regular ACTH Stimulation Testing?
ACTH stimulation testing is the cornerstone of trilostane monitoring. Because the goal of treatment is to reduce cortisol to an appropriate range (not to eliminate it entirely) testing confirms where a dog's cortisol level falls at a specific point after dosing. Results inform whether the dose is appropriate, too low to be effective or too high and risking hypoadrenocorticism.
Veterinarians typically schedule ACTH stimulation testing at approximately 10 to 14 days after starting trilostane or after any dose change, again at 30 days, and then at longer intervals as the dog stabilizes. This monitoring schedule requires owner commitment and is a core part of responsible trilostane management, not an optional add-on.
What Are the Commercial and Compounded Options for Trilostane?
VetORYL is the FDA-approved commercial trilostane product for use in dogs with hyperadrenocorticism. It is available in multiple capsule strengths, which allows veterinarians to start close to the target dose for many dogs. As a full-service veterinary pharmacy, Mixlab carries VetORYL and can dispense it with a valid veterinarian prescription.
Compounded trilostane is also available through Mixlab for dogs whose dose does not align with the available commercial capsule strengths. This is particularly relevant for very small dogs or dogs who require a dose between available VetORYL strengths. Precise dosing in Cushing's disease management matters because the therapeutic window involves balancing cortisol reduction against the risk of inducing hypoadrenocorticism. Compounded medications are prepared by a licensed pharmacy for an individual patient based on a veterinarian's prescription. Unlike FDA-approved drugs, they have not been evaluated by the FDA for safety and effectiveness.
Among compounded trilostane prescriptions filled at Mixlab, capsules account for just over half of fills (53%), oral suspensions for about 28%, flavored chews for 14% and mini tablets for the remainder, reflecting how compounding formulation is tailored to a dog's size and swallowing ability rather than a one-size-fits-all approach.
Frequently Asked Questions About Trilostane for Dogs
What Is the Trilostane Dosage for Dogs?
Trilostane dosing for dogs is weight-based and adjusted based on ACTH stimulation test results. It is not a fixed dose. Your veterinarian will determine the starting dose and will refine it through monitoring. Because the effective dose varies considerably between individual dogs, do not adjust the dose without consulting your veterinarian and reviewing current testing results.
Does Trilostane Interact With Other Medications?
Trilostane can interact with certain other medications, particularly those that affect the adrenal glands or cortisol levels, including other medications used in Cushing's management or medications used to treat Addison's disease. It is important to give your veterinarian a complete picture of everything your dog is currently taking, including supplements. Your veterinarian will evaluate potential interactions before prescribing and will let you know if any adjustments are needed. Never start or stop a medication without consulting your veterinarian first.
What Should I Do If My Dog Misses a Dose of Trilostane?
If you miss a dose, give it as soon as you remember, unless it is close to the time of the next scheduled dose, in which case skip the missed dose and continue as normal. Never give two doses at once to make up for a missed one. If you are unsure what to do, contact your veterinarian for guidance.
What Is the Difference Between VetORYL and Compounded Trilostane?
VetORYL is the FDA-approved commercial trilostane capsule for dogs with hyperadrenocorticism. Compounded trilostane refers to a formulation prepared by a veterinary compounding pharmacy in a strength not commercially available. This is often used when a dog needs a dose that falls between VetORYL's available capsule strengths. Your veterinarian will determine which formulation is appropriate based on the prescribed dose.
How Long Do Dogs Stay on Trilostane?
Trilostane is typically used as a long-term medication for dogs with hyperadrenocorticism. Cushing's disease requires ongoing management rather than a short course of treatment. Your veterinarian will continue monitoring through regular ACTH stimulation testing and will adjust the plan based on how your dog responds over time.
Can a Dog's Signs of Cushing's Resolve on Trilostane?
Many owners report noticing changes in their dog's clinical signs, including decreased thirst and urination, improved coat and increased activity, over the weeks and months following the start of trilostane therapy. The pace and degree of change vary by individual dog. Your veterinarian will track progress through monitoring and will discuss what responses are realistic to expect based on your dog's specific situation.
Key Takeaway
Trilostane is a prescription medication that veterinarians discuss for dogs diagnosed with hyperadrenocorticism (Cushing's disease). It is available as VetORYL (the FDA-approved commercial product) and as compounded formulations for dogs needing doses between available capsule strengths. Regular ACTH stimulation testing is an essential part of management because the goal is to reduce cortisol appropriately without driving it too low. Mixlab carries both VetORYL and compounded trilostane, and orders require a valid veterinarian prescription. If your dog has been diagnosed with Cushing's disease, discuss monitoring frequency and formulation options with your veterinarian at the next appointment.