Last Updated: 29/12/2025
Trilostane (Vetoryl) for Dogs: Medication Guide
Trilostane (Vetoryl) is a vital medication for managing Cushing's syndrome in dogs. Our comprehensive guide covers how it works, potential side effects, and important handling safety tips to help your pet live a happy, comfortable life.
Author: Dr Jenny Eales BVSc (Hons)
Reading Time: 6 minutes - short read
Managing a chronic condition like Cushing's syndrome can feel like a bit of a whirlwind for any pet parent. If your veterinarian has prescribed Trilostane - commonly known by the brand name Vetoryl - you likely have plenty of questions about how it helps your furry friend feel their best again. This medication plays a crucial role in balancing hormone levels, helping to reduce those classic symptoms like excessive thirst and a pot-bellied appearance. Understanding how to safely administer and monitor this treatment is the first step in helping your pet enjoy their golden years with a wagging tail.
How Trilostane works and what it's used for
Trilostane is a short acting competitive inhibitor of the enzyme used for synthesis of cortisol and all other steroids. It inhibits the production of glucocorticoids, and to a lesser extent mineralocorticoids and sex hormones. It acts on the adrenal gland to stop it making excessive amounts of steroids.
Trilostane is used for the treatment of pituitary-dependent and adrenal-dependent hyperadrenocorticism (Cushing's syndrome) in dogs.
It may also be used off label in cats and horses to treat hyperadrenocorticism and in dogs for treatment of alopecia X. Off-label use means that it has not been registered for use in these cases so please follow the directions of your treating Veterinarian closely.
Read more about common conditions for which Trilostane may be prescribed:
How is it administered?
Trilostane comes in capsule form (Vetoryl) and is taken orally once or twice a day with food.
Vetoryl is available in 5mg, 10mg, 30mg, 60mg and 120mg capsules. A combination of different sized capsules may be needed to make the correct dose. Vetoryl capsules should never be opened or divided.
How quickly does it work?
Trilostane starts to work approximately 1-2 hours after ingestion, but you may not notice a change in your pets symptoms until 9-12 days after starting the medication.
If you are concerned that there are no noticeable changes please contact your veterinarian.
Potential side effects of Trilostane
While trilostane is usually well tolerated by dogs, side effects can occur. These are usually mild and self limiting. The most common are:
- Lethargy
- Weakness
- Loss of appetite in the first few days
- Vomiting
- Diarrhoea
- Respiratory signs
- Changes to electrolytes (sodium and potassium)
Other more serious potential side effects include:
- Severe depression
- Hemorrhagic (bloody) diarrhoea
- Collapse
- Addisonian crisis
- Hypoadrenocorticism
- Lameness or worsening of arthritis
- Urinary tract infection
- Neurological signs
- Haematuria (blood in urine)
- Cardiopulmonary signs
- Renal failure
- Adrenal necrosis
- Sudden death (rare)
It is extremely important to follow your veterinarians advise regarding monitoring and dose changes while your pet is taking Trilostane. If you notice anything unusual, contact your veterinarian immediately.
Precautions and contraindications
Precautions:
- Caution should be used in animals being treated with NSAIDs (non steroidal anti-inflammatories) for arthritis
- Caution should be used in animals with hyperkalemia
- This medication should be used with caution in pets with low circulating red blood cells (anemia)
Contraindications:
- Animals with primary hepatic disease
- Animals with renal insufficiency
- Pregnant or nursing bitches or in any animals intended for breeding
- Dogs weighing less than 3kg
- Pets who have had an allergic reaction to Trilostane or like products before
- Pets taking mitotane - an interval of at least one month should elapse between cessation of mitotane and the introduction of trilostane
Drug interactions
Drugs that can interact with trilostane include:
- Potassium-sparing diuretics (spironolactone)
- ACE inhibitors (benazepril, enalapril)
- Ketoconazole
- Mitotane
- Potassium supplements or high potassium food
- Possibly non steroidal anti-inflammatory drugs (NSAIDs)
Trilostane may interact with other medications and food, so it is extremely important to let you veterinarian know of any medication (including supplements, vitamins and herbal therapies). Do not give any new food or medications without first talking to your veterinarian.
If your pet experiences any unusual reactions when taking multiple medications, contact your veterinarian.
Storage and handling
Storage
Store in a childproof container below 25°C and away from heat and direct sunlight. Keep the blister strips in the carton.
Handling
- DO NOT handle this product if you are pregnant or trying to conceive.
- This medication is potentially harmful to humans.
- Wash your hands well after handling.
- DO NOT open or divide capsules. in the event of accidental breakage and contact of granules with eyes or skin wash immediately with plenty of water and seek medical advice
- Keep out of reach of children and pets
- Not for human use
- This product is harmful if swallowed
- People with known hypersensitivity to trilostane or any of the excipients should avoid contact with the product
- If ingested seek medical advice immediately
To avoid accidental ingestion, administer the medication to your pet immediately after removal from the package, and observe your pet closely to ensure that the entire dose has been consumed. Keep out of reach and sight of children.
Dosage
Vetoryl capsules are usually administered once daily with food, but in some cases your veterinarian may advise twice daily administration.
The starting dose is approximately 2 - 6 mg/kg, based on available combinations of capsule sizes. This dose may need to be changed depending on your pet's response to the medication.
It is crucial that you follow your Veterinarian's specific instructions regarding dosage for your individual pet.
Missed dose
If you miss giving your pet a dose of Vetoryl give it as soon as you remember. However, if it is close to the time for the next dose, skip the missed dose and resume the dosing schedule as normal - do not give two doses at once.
Stopping the medication
Do not stop giving your pet Trilostane without first discussing it with your veterinarian. Any cessation or change to your pet's medication should only be done under the close supervision and recommendation of your treating Veterinarian.
Missed doses reduce the effectiveness of therapy. This drug will likely need to be taken for the rest of your pet's life.
Overdose
If you suspect or know that your pet has taken too much Trilostane contact your veterinarian or an emergency veterinarian immediately.
Importance of Veterinary monitoring
It is very important that you follow your veterinarian's advice regarding when to take your pet back for monitoring or blood tests while your pet is taking trilostane.
Periodic blood work to monitor your pet's health and the effects that taking this medication is having on your pet's body is recommended as long-term therapy is often necessary. Dose adjustments may be made based upon these results and an assessment of how your pet is responding clinically.
Related medications
- Mitotane
- Ketoconazole
FAQs
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