By Rania Gollakner, BS, DVM, MPH

What is trilostane?

Trilostane (brand names: Vetoryl®, Desopan®, Modrastane®, or Modrenal®) is used for the treatment of hyperadrenocorticism in dogs (Cushing’s disease) and cats and Alopecia X in dogs.

How is trilostane given?

Trilostane is given orally (by mouth) in the form of capsules. It should be given with food, and preferably in the morning if once daily dosing. This medication should take effect within 1 to 2 days.

Wash hands after administering the medication. If you are pregnant or trying to become pregnant, do not handle this medication. Do not empty the capsule and do not divide the capsules.


What if I miss giving my pet the medication or my shipment is late?

If you miss a dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Do not stop this drug without consulting your veterinarian.

Are there any potential side effects?

Trilostane is a short-acting medication that typically stops working within 24 hours and is generally well-tolerated; however, side effects can include lethargy, vomiting, diarrhea, and lack of appetite during the first few days of therapy. Reducing the dose and slowly increasing to the recommended schedule may reduce the side effects. Speak to your veterinarian if your pet experiences these sings. These side effects are usually mild and resolve on their own.

Hypoadrenocorticism can occur and is usually reversible once the medication is discontinued, but in very rare cases, adrenal gland damage and death can occur in dogs.

In cats, side effects include lethargy, anorexia, and dulled mental activity.

A life-threatening condition, called an Addisonian crisis, can occur while using this medication. Your pet should be monitored closely for vomiting, diarrhea, lethargy, shaking, increased drinking or urination, weakness, or collapse.

Are there any risk factors for this medication?

Trilostane should not be used in pet that are hypersensitive or allergic to it or in pregnant animals. Trilostane should be used with caution in pets with kidney or liver impairment or in nursing animals. Safe use has not been evaluated in male dogs used for breeding.

Are there any drug interactions I should be aware of?

Trilostane should be used with caution when given with the following drugs: ACE inhibitors (such as benazepril or enalapril), aminoglutethimide, ketoconazole, mitotane, potassium-sparing diuretics (spironolactone), and potassium supplements.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

You should monitor your pet closely for adverse effects. After starting the medication, frequent and regular rechecks with your veterinarian are important. Adrenocorticotropic hormone (ACTH) stimulation tests and other laboratory tests will be needed to monitor for adverse effects, efficacy, and dose appropriateness.

How do I store trilostane?

Trilostane capsules should be stored in tight, light-resistant containers at room temperature 25°C (77°F), with brief excursions at 15° - 30°C (59° - 86°F) permitted.

What should I do in case of emergency?

In the case of an Addisonian crisis, glucocorticoids should be administered immediately, followed by veterinary care. Your veterinarian should provide you with an emergency supply of glucocorticoids as a precaution.

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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