Vetoryl for dogs


Hard capsules

Active ingredient



Hormone medication

What is Vetoryl?

Vetoryl is a brand name of the drug trilostane. It is prescribed to dogs with Cushing’s disease (hyperadrenocorticism), a condition where the adrenal gland produces excess cortisol (a type of hormone).

Vetoryl is a man-made steroid. It works by blocking the action of certain enzymes in the adrenal glands (enzymes are types of proteins that facilitate production of new substances.). This reduces excess cortisol production  in dogs with Cushing’s disease. In this way, Vetoryl minimises the clinical signs of Cushing’s disease and reduces the risk of serious health consequences.

What does Vetoryl do?

Vetoryl reduces excess cortisol production in dogs with Cushing’s disease. 

Normally, cortisol is produced by a system of enzymes in the adrenal glands. Cortisol has many important functions (e.g. regulating immunity, metabolism and stress responses). However, if the adrenal gland overproduces cortisol, Cushing’s disease (hyperadrenocorticism) occurs.

Vetoryl is a man-made steroid that binds to cortisol-producing enzymes. As a result, these enzymes cannot bind to the molecules that they use to produce cortisol. Thus, cortisol production is decreased. 

In this way, Vetoryl manages the signs of Cushing’s disease (e.g. excessive drinking and urination, skin problems). Vetoryl also reduces the risk of serious consequences from untreated Cushing’s (e.g. diabetes, blood clots). It’s important to understand that Vetoryl manages the signs of Cushing’s diseases, but does not cure it.

What is Vetoryl for?

Vetoryl is prescribed to manage two common types of Cushing’s disease:

  • Pituitary-dependent Cushing’s disease: ~80-85% of dogs with Cushing’s disease have this condition. This condition occurs when there is a tumour in the pituitary gland (the pituitary gland is located at the base of the brain). This tumour causes overproduction of the ACTH hormone. Excess ACTH stimulates cortisol overproduction by the adrenal gland.
  • Adrenal-dependent Cushing’s disease: ~15-20% of dogs with Cushing’s disease have adrenal tumours that cause cortisol overproduction.

Vetoryl regulates cortisol production in both types of Cushing’s disease. This addresses the symptoms of Cushing’s disease (e.g. increased thirst, appetite, lethargy).

What are the side effects of Vetoryl in Dogs?

As with all medicines, Vetoryl can have side effects. These include:

Addison’s Disease (hypoadrenocorticism): Monitor your pet closely while they are on Vetoryl. While Vetoryl is tolerated well by most dogs, there is a risk of your dog experiencing abnormally low cortisol levels (Addison’s disease)  if the dose of Vetoryl is too high.

Addison’s disease usually presents in two forms. It can manifest as a collection of vague clinical signs (e.g. diarrhoea, vomiting, increased thirst/urination, trembling, weakness) that mimic other diseases. However, if cortisol levels become critically low, an “Addisonian crisis” can be triggered. Dogs in an Addisonian crisis display signs such as severe vomiting and diarrhoea, sudden weakness or even collapse. Addison’s disease is an emergency that requires immediate veterinary attention.

Vomiting or diarrhoea: Some pets may have temporary digestive upset when starting Vetoryl. This should improve as their body adjusts to the medication. Prolonged, frequent or severe vomiting/diarrhoea should be reported to your vet immediately.

Lethargy or weakness: Occasionally, pets might show signs of tiredness. This is usually mild and temporary, but it’s crucial to monitor to see if it develops to prolonged lethargy.

Little or no appetite/water consumption: As Vetoryl reduces excess cortisol levels, your dog’s appetite and water consumption should return to normal. However, if your dog has poor appetite and water intake, contact your vet immediately.

Unmasked arthritis: Vetoryl may sometimes unmask hidden joint inflammation (arthritis) in dogs. Signs include limping.

Incoordination: This is a rare side side effect, but contact your vet immediately if you notice your dog wobbling or seeming uncoordinated.

Bloating: This is a rare side effect, but contact your vet immediately if you notice bloat in your dog.

Remember, not all pets will experience these side effects, and the benefits of using Vetoryl often outweigh the risks, especially in pets with serious health conditions. However, if you notice any concerning symptoms or changes in your pet’s behaviour or health while they are taking Vetoryl, it’s important to contact your vet immediately. They can provide guidance and adjust the treatment plan if necessary to ensure your pet’s safety and well-being.

Which pets is Vetoryl not suitable for?

Vetoryl is not suitable for the following dogs:

-Dogs with liver or kidney issues
-Pregnant or lactating dogs
-Dogs that are allergic to Vetoryl or any of its ingredients.

How to give Vetoryl safely

  1. Follow vet instructions: Always use Vetoryl exactly as your vet has prescribed. This includes the right dose and frequency. Never adjust the dose on your own, even if your dog seems to be feeling better or worse. If you aren’t sure of the dose prescribed, please call your vet to confirm.
  2. Do not break capsules: Vetoryl capsules should be given whole.
  3. Give Vetoryl with food: Vetoryl is more effective when given with food. Generally, Vetoryl is best given in the morning – but do check with your vet regarding the best timing for your dog.
  4. Check with your vet if giving anything else: There is a higher risk of side effects if Vetoryl is given along with certain drugs (e.g. ACE inhibitors like Benazecare). Therefore, check with your vet before giving Vetoryl if your dog is on any medications. While your vet should be aware of other drugs your pet is on, it’s always worth double-checking in case there’s been a miscommunication somewhere. If your dog is on supplements or non-prescription treatments you should also tell your vet when they prescribe Vetoryl, as they may not be suitable to be given together.
  5. Storage and Handling: Store Vetoryl  according to the instructions on the label, usually in a cool and dry place. Make sure it’s out of reach of children and other pets. Women who are pregnant or are intending to become pregnant should not handle Vetoryl.
  6. Report any accidental overdose to your vet immediately: If you have mistakenly given too much Vetoryl, report it to your vet as soon as you realise the error.  Your dog may be at risk of Addison’s disease. Your vet may recommend blood tests, intravenous fluids, medication or monitoring, depending on the severity of the overdose.

Vetoryl FAQs

How long does it take for Cushing’s syndrome to go away in dogs?

Cushing’s syndrome typically does not go away in dogs. Cushing’s syndrome is typically a lifelong condition that requires lifelong medication.

For more information about Cushing’s, our vets have written an e-learning course that might help. Check out Canine Cushing’s Disease.

What does Vetoryl do to dogs?

Vetoryl binds to the enzymes in the body that produce cortisol. By binding to these enzymes, the Vetoryl stops the body from producing cortisol, therefore reducing the symptoms of Cushing’s.

Should I treat my old dog for Cushing’s?

If your dog has symptoms of Cushing’s, it’s best to head to a vet to get a diagnosis. If Cushing’s disease is diagnosed, your vet will talk you through the treatment options. Generally, it’s recommended to treat Cushing’s – even in senior dogs – to help your dog’s quality of life.

For more information about Cushing’s and deciding whether to treat it, our vet-written resource Cushing’s in Dogs is packed with information.

How long can a dog be on Vetoryl?

Vetoryl is usually needed for the rest of your dog’s life, after they’ve been diagnosed with Cushing’s. It’s designed to be given long-term.

Vetoryl Datasheet

All drugs have a manufacturer’s datasheet, which gives information about the drug’s use and possible side effects. There is usually one in your Vetoryl box, but if you have lost it you can click on the button below to be taken on an online version.

Courses related to Vetoryl

If your dog or cat is on Vetoryl, you might be interested in learning more about their condition with our interactive, vet-written courses. Each one of our courses has been carefully written by qualified vets and e-learning specialists, and you have access to it – including all updates – for the rest of your pets’ life.

Please note that the information contained herein is provided for informational purposes only. Although it has been written by a vet, we cannot consider the individual nature of your pet’s problems so it does not constitute veterinary advice. If you have questions about your pet’s medication or their health you should contact a vet, who will be able to help.