All About Vetoryl (trilostane)
- Canine Cushing's Alliance
- Dec 23, 2023
- 5 min read
Updated: 3 days ago
What is Vetoryl?
Vetoryl is a prescription drug. It's manufactured by Dechra, a veterinary pharmaceutical company, and is approved by the U.S. Food and Drug Administration (FDA) for the treatment of both pituitary-dependent and adrenal-dependent Cushing’s disease in dogs. The active ingredient in Vetoryl is an enzyme inhibitor called trilostane, which blocks the excessive production of cortisol by the adrenal glands. Vetoryl is currently available in 5 mg, 10 mg, 20 mg, 30 mg, 60 mg, and 120 mg capsules.
Administering Vetoryl
Vetoryl should be given with food since food enhances absorption of the medication. It doesn't have to be a large amount. I normally drop the capsules right into Violet's breakfast in the morning. I give the PM dose with a scoop of yogurt or peanut butter. You can do whatever works for your dog. Please note that splitting or opening the capsules puts you and your pet at risk and should never be done. Consult your veterinarian if you’re struggling to administer Vetoryl to your dog.
Starting Dose
The label for Vetoryl specifies a starting dose of 1 to 3 mg per pound (2.2 to 6.7 mg per kilogram) once a day and recommends starting with the lowest possible dose based on body weight and available combination of capsule sizes.
But new research has found that all dogs should actually be started on a much lower dose than what’s on the label. Specifically, there's less potential for adverse effects when a low, twice-daily dose of Vetoryl is given. Clinical studies also suggest that larger dogs are more sensitive to Vetoryl and need less of it to control their symptoms than smaller dogs.
As a result of this research, many veterinary hospitals have revised their dosing protocols. UC Davis recommends a starting dose of 0.1-0.5 mg/kg every 12 hours, with dogs over 20 kg (44 pounds) starting at the lower end.
The key takeaway: It’s better to begin on a lower dose and work your way up, if needed, than to start on too high of a dose and cause your dog’s cortisol levels to drop too fast. The best advice is to start low and go slow.
See, for example, Trilostane dose versus body weight in the treatment of naturally occurring pituitary-dependent hyperadrenocorticism in dogs.
Monitoring Tests & Dose Adjustments
After starting Vetoryl, your dog will need frequent blood tests to measure cortisol levels and make sure he or she is on the right dose. The traditional monitoring test is an ACTH stimulation (stim) test, but some veterinarians also offer a new method called a pre-Vetoryl cortisol test. Dechra recommends that the ACTH stim test be conducted 4 to 6 hours after you’ve given your dog Vetoryl, with some food or breakfast, in the morning. However, many vets conduct the test between 2 to 4 hours because this is when the medication reaches its peak effect. Either time is fine, as long as it's the same at every recheck.
The first monitoring test takes place about 14 days after starting Vetoryl (or sooner if a dog becomes unwell). The purpose of the 14 day test is to make sure that the amount of Vetoryl your dog is taking isn’t causing cortisol levels to fall too low and too fast. At this point, the veterinarian will determine whether your dog should stay on the same dose or be taken off Vetoryl and restarted at a lower dose. No increase should be made at the 14-day mark, even if symptoms are still present, because cortisol levels can continue to fall for a month after starting the medication.
After 30 days on Vetoryl, your veterinarian will recheck cortisol values and clinical signs. The purpose of this visit is (1) to assess whether your dog is on a sufficient dose to manage symptoms and (2) make sure there are no signs of receiving too much medication. Sometimes, both the dose and dosing frequency (e.g., from once daily to twice daily) need to be adjusted. To minimize the risk of adverse effects, dose increases should generally be no higher than 25 percent.
Finding the dose that works best for your dog can take time. There's no one-size-fits-all with Cushing's disease. Anytime a dose adjustment is made, the testing cycle should be started over. This means that cortisol levels should be checked at 10-14 days after the new dose is started and then rechecked at 30 days. If no dose adjustment is needed after 30 days, subsequent tests are recommended every three months thereafter and should include a re-check of cortisol levels, electrolytes, and kidney and liver function.
NOTE: For insight into interpreting results of ACTH stim tests, see this Vetoryl ACTH monitoring flowchart.
How long does it take to see an improvement in symptoms after starting Vetoryl?
It can take up to a month for Vetoryl to reach its full effect. Some signs, such as increased urinating, tend to improve within a couple of weeks. Other issues, such as hair loss, take more time to resolve.
Potential Side Effects
Vetoryl is generally safe for most dogs, especially if they're started on a low dose. Occasionally, serious side effects, such as collapse, severe sodium/potassium imbalance, and damage to the adrenal gland, can occur. If your dog develops any signs of illness, such as vomiting, diarrhea, loss of appetite, or shaking, stop treatment immediately and seek veterinary care. These are signs that cortisol may be falling too low, which can lead to a life-threatening emergency. For information about stopping and restarting Vetoryl, please see our article, Protocol for Stopping and Restarting Vetoryl (trilostane).
Precautions for Dogs
Vetoryl should not be given to a dogs that have primary liver disease, renal (kidney) insufficiency, or are pregnant. Drugs that reduce adrenal function (e.g. aminoglutethimide, ketoconazole, and mitotane), potassium-sparing diuretics (e.g. spironolactone), and potassium supplements should not be used with Vetoryl.
Dogs that are on Vetoryl and also taking an ACE inhibitor (e.g. benazepril or enalapril) or ARB (e.g. Telmisartan) should have their electrolyte and potassium levels periodically checked. All of these drugs can elevate potassium, which can be dangerous.
Precautions for Humans
Wash your hands after handling Vetoryl capsules, and never split or open the capsules. Don’t handle Vetoryl capsules if you’re pregnant or planning to become pregnant.
References
How to report side effects
Dechra US: Contact Form
Dechra UK: Contact Form
U.S. FDA: How to Report Animal Drug and Device Side Effects and Product Problems. Note: the New Animal Drug Application number for Vetoryl is 141-291 and should be included in your report.