PetMD Editorial
Written by:
PetMD Editorial
Published: March 20, 2013

Drug Info

  • Common Name: Vetoryl
  • Generics: No generics available
  • Drug Type: Adrenocortical suppressant
  • Used For: Hyperadrenocorticism
  • Species: Dogs
  • Administered: Capsules
  • How Dispensed: Prescription Only
  • Available Forms: 10mg, 30mg, 60mg, 120mg Capsules
  • FDA Approved: Yes, for dogs


Trilostane (Vetoryl) is indicated for the treatment of pituitary-dependant hyperadrenocorticism and treatment of hyperadrenocorticism due to adrenocortical tumors in dogs.

Dosage and Administration

Always follow the dosage instructions from your veterinarian. Trilostane (Vetoryl) should be administered with food unless otherwise directed by your veterinarian.

Missed Dose?

If a dose of Trilostane is missed, give it as soon as you remember. If you remember when it is almost time for the next dose, skip the one you missed and get back on your regular schedule. Do NOT double the dosing.

Possible Side Effects

Most common side effects of Trilostane include: 

  • Reduced appetite
  • Vomiting
  • Diarrhea or loose stool
  • Lethargy/dullness
  • Weakness

Occasional but more severe effects include: 

  • Severe depression
  • Hemorrhagic diarrhea
  • Collapse
  • Pale hypoadrenocortical crisis or adrenal necrosis/rupture may occur, and result in death.

Immediately discontinue and contact your veterinarian if you think your dog has any medical problems or side effects while taking Trilostane.


Do not administer to dogs that are allergic to Trilostane. If your pet has any allergic reactions to the medication please contact your veterinarian immediately.

Do not use Trilostane in pregnant dogs.  Studies conducted have shown teratogenic effects and early pregnancy loss.  

Do not give to dogs that have primary liver disease or certain type of kidney diseases. The use of Trilostane may result in your dog developing hypoadrenocorticism disease and /or corticosteroid withdrawal syndrome.


Store at room temperature away from heat and direct sunlight. Additionally, as with any medication, keep out of children’s reach.

Drug Interactions

Consult your veterinarian when giving other medications with Trilostane as interactions may occur. Interactions may occur when given with ACE inhibitors such as Enalapril; potassium-sparing diuretics such as spironolactone, ketoconazole; or potassium supplements.  

If mitotane was given prior, please wait at least one month before starting Trilostane.

Signs of Toxicity/Overdose

Overdose of Trilostane may cause: 

  • Vomiting
  • Lethargy
  • Weakness
  • May collapse

If you suspect or know you dog has had an overdose, please contact your veterinarian or emergency vet clinic immediately.

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