Trilostane for Dogs: A First-Choice Medication for Cushing’s Disease
Key takeaways:
Cushing’s disease is a condition that tends to affect older dogs, and it usually requires lifelong treatment.
Trilostane (Vetoryl) is a typically well-tolerated medication that treats Cushing’s disease. But dogs need to be monitored closely while taking the medication, which can also be expensive.
It’s important to contact your vet right away if you notice any weakness, appetite changes, vomiting, or diarrhea while your dog is taking trilostane. The medication may need to be adjusted or stopped.
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Table of contents
As your dog gets older, you may notice certain changes in their energy levels, appetite, and bathroom habits. While these changes can be part of the normal aging process, they could also indicate something more serious: Cushing’s disease.
Cushing’s disease, a condition that affects the fight-or-flight hormone known as cortisol, is relatively common in dogs — with 1 to 2 cases in every 1,000 dogs per year. In most instances, the condition is managed with long-term medication.
If your dog is diagnosed with Cushing’s disease, your vet may prescribe them a medication called trilostane (Vetoryl). This well-tolerated medication is FDA approved to treat Cushing’s disease.
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Trilostane for dogs at a glance
Common names | Trilostane (Vetoryl) |
What it treats | Cushing’s disease |
How it comes (forms) | Capsules |
Common side effects | Vomiting, diarrhea, loss of appetite, tiredness or weakness |
What is trilostane for dogs?
Trilostane (Vetoryl) is a commonly prescribed FDA-approved treatment for Cushing’s disease in dogs.
Cushing’s disease causes your dog’s adrenal glands to produce too much cortisol. Most often this is due to a tumor that affects the adrenal glands. Trilostane prevents the adrenal glands from making cortisol by blocking the enzyme (protein) needed to make the hormone. This results in less cortisol in the body, which helps to alleviate Cushing’s disease symptoms in your pet. Once treatment is started, you may start to notice some symptom improvement in about a week.
Trilostane is the only FDA-approved medication to help treat Cushing’s disease caused by pituitary or adrenal tumors. But it’s important to know that the medication doesn’t treat the tumors themselves — only some of their effects. Other treatments or procedures may be needed if a tumor is cancerous, starts to grow, or has spread.
What are the side effects of trilostane in dogs?
While cortisol is the culprit behind Cushing’s disease, it’s still necessary for many other processes in your dog’s body to function properly. Since trilostane prevents cortisol from being made, it may lead to side effects related to low cortisol levels, including:
Vomiting
Diarrhea, which may be bloody
Lack of appetite
Appearing tired or weak
If you notice any of the side effects listed above, contact your vet right away. In some cases, cortisol levels can become too low, which can be life-threatening. Your vet can examine your dog and determine if their dosage needs to be adjusted or they need to pause treatment.
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Given the importance of keeping cortisol balanced in the body, your vet will be monitoring your dog closely to make sure that their levels stay on track, especially when they first start treatment. But once a stable dosage is reached, follow-ups will be less frequent.
Serious risk of trilostane for dogs
Trilostane isn't recommended for dogs who have kidney or liver disease or who are pregnant. Trilostane can also cause electrolyte imbalances when taken with certain medications used to treat heart conditions, like ACE inhibitors or spironolactone.
What is the dosage of trilostane for dogs?
Your dog’s trilostane dosage will depend on their weight. The starting dose is 2.2 mg to 6.7 mg per kilogram of body weight. This is given once daily with food so that it’s absorbed better.
Trilostane is available in capsules that come in five different doses:
5 mg
10 mg
30 mg
60 mg
120 mg
But if you need a dose that’s different from the ones listed above, your vet may have you fill your dog’s prescription at a compounding pharmacy where they can customize doses.
As an owner, it’s important to protect yourself from potential exposure to the medication. This means washing your hands after giving your dog a dose and not opening or emptying the capsules.
Don’t handle trilostane if you’re pregnant or trying to become pregnant. Animal studies showed that the medication could be harmful to a fetus.
Will my dog need to take trilostane for the rest of their life?
Cushing’s disease tends to be a lifelong condition, which means that your dog will need to take trilostane long term. And while tumor-removal surgery would seem to be the most effective option, this is usually only possible with adrenal tumors. Even then, surgery can be risky and expensive.
That’s why medications tend to be the preferred way to manage Cushing’s disease in most cases. As described above, diligence is key: Keeping up with regular blood tests and close monitoring from your vet helps flag potential issues and keeps your dog healthy.
How much does trilostane cost?
How much you’ll pay for trilostane depends on your dog’s dosage. In general, the cost ranges from about $35 to $160 for 30 capsules.
Retail pharmacies don’t typically carry trilostane, so you’ll likely need to purchase it online or from a pharmacy that specializes in veterinary medications.
Will insurance cover the cost of trilostane for my dog?
Yes, some pet insurance plans cover the costs of managing Cushing’s disease, including medications. And between treatments, blood work, and follow-up visits, things can add up quickly, so the savings can be significant.
If your dog isn’t already insured, you may run into some challenges getting coverage, since plans don’t typically cover preexisting conditions. But it may be worth talking to your vet or shopping around to see what options are available to make treatment more affordable.
Are there any other treatment options for Cushing’s disease in dogs?
There are a few medications that vets use to treat Cushing’s disease in dogs. Some are FDA approved for animal use, while others are human medications that are used off-label to treat the condition.
Anipryl
Anipryl (selegiline) is the other FDA-approved medication for Cushing’s disease in dogs, but it’s rarely prescribed to dogs. It is a monoamine oxidase inhibitor (MAOI) that is thought to work by raising levels of a brain chemical called dopamine. Raising dopamine levels has been shown to lower the enzymes that tell the adrenal glands to make cortisol. But this doesn’t help with all types of Cushing’s disease in dogs. Anipryl only helps treat Cushing’s disease caused by pituitary tumors.
Lysodren
Lysodren (mitotane) is sometimes prescribed off-label to treat Cushing’s disease in dogs. It’s a cancer medication that works by destroying certain parts of the adrenal glands that make cortisol.
Like with trilostane, dogs taking Lysodren need to be closely monitored since there is a risk of a dangerous drop in cortisol levels. The medication can also cause liver damage.
The bottom line
Cushing’s disease is a lifelong condition that’s relatively common in dogs. It’s usually managed with medications, though surgery is sometimes used to remove the underlying tumor that’s causing symptoms.
Trilostane (Vetoryl) is a medication that’s FDA approved to treat the condition in dogs, but it can be relatively expensive. During treatment, it’s important that your pet is carefully monitored — by you and your vet — for side effects and to make sure that cortisol levels are kept in check.
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References
De Bruin, C., et al. (2009). Cushing's disease in dogs and humans. Hormone Research.
Dechra Veterinary Products. (2024). Vetoryl - trilostane capsule [package insert].
Dechra Veterinary Products. (2024). Vetoryl - trilostane capsule [package insert]. DailyMed.
Embrace Pet Insurance Agency, LLC. (n.d.). Pet insurance that covers pre-existing conditions.
Grognet, J. (2024). Cushing’s disease in dogs. American Kennel Club.
Peterson, M. E. (1999). Medical treatment of pituitary-dependent hyperadrenocorticism in dogs: Should L-deprenyl (Anipryl) ever be used? Journal of Veterinary Internal Medicine.
U.S. Food and Drug Administration. (2023). Treating Cushing’s disease in dogs.
Zoetis Inc. (2022). Anipryl - selegiline hydrochloride tablet [package insert]. DailyMed.
