image of various medications

How does Trilostane work and what is it 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.

What are the 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:

  • Contraindicated in animals with primary hepatic disease
  • Contraindicated in animals with renal insufficiency
  • Contraindicated in pregnant or nursing bitches or in any animals intended for breeding
  • Contraindicated in dogs weighing less than 3kg
  • Contraindicated in pets who have had an allergic reaction to Trilostane or like products before
  • Contraindicated in pets taking mitotane - an interval of at least one month should elapse between cessation of mitotane and the introduction of trilostane

 

Does Trilostane interact with other drugs?

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. 

What should I do if my pet misses a 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 Trilostane 

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. 

What should I do if my pet has taken too much Trilostane?

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.

Alternative and Related Medications

  • Mitotane
  • Ketoconazole

References:

  • VIN Veterinary drug handbook:  https://www.vin.com/members/cms/project/defaultadv1.aspx?pId=13468&id=7273053&f5=1
  • VIN client drug information sheets:  https://www.vin.com/members/cms/project/defaultadv1.aspx?pid=369&id=10064503&f5=1
  • https://elabels.apvma.gov.au/60620ELBL.pdf
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5855282/
  • https://www.vin.com/apputil/content/defaultadv1.aspx?id=7054636&pid=12886&print=1