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Trilostane for Dogs and Cats

By Barbara Forney, VMD

Last reviewed: 7/14/2022

Commonly prescribed for: Cushing’s Disease

Species: Dogs and Cats

Therapeutic Class: Steroidogenesis Inhibitor

General Drug Information and Indications

Trilostane is a synthetic enzyme inhibiting drug that is used to treat Cushing’s Disease in dogs and cats. Trilostane decreases the production of excessive cortisol hormone by the adrenal gland. This disease is not cured by trilostane but can be managed successfully.

Before treatment is started, your veterinarian will perform routine blood-tests and a urinalysis, followed by more specialized blood tests to confirm the diagnosis of Cushing’s disease. Your dog usually will start to respond to trilostane therapy within two to four weeks. Researchers report that trilostane is effective in about 80% of treated dogs. Although most dogs tolerate trilostane well, there is a wide range of individual variation regarding dose and your veterinarian will need to monitor your dog closely, particularly at the beginning of treatment.

Trilostane also may be used to treat Cushing’s disease in cats. Cushing’s disease is quite rare in the cat and it may not respond as well. Frequently cats with Cushing’s disease also have underlying diabetes mellitus. Trilostane does not appear to change their insulin requirements.

Trilostane was approved recently by the FDA for use in animals. In some instances the appropriate size and dose is not available from the pharmaceutical manufacturer, and in those circumstances, it may be compounded by a specialty pharmacy.

How to Give this Medication

Give this medication to your pet exactly as your veterinarian prescribes. If you miss giving your pet a dose of trilostane, give the next dose as soon as you remember or, if it is close to the next scheduled dose, return to the regular schedule. Do not double dose to catch up.

Oral trilostane is absorbed rapidly and usually is given with food.

Wash your hands after giving your pet this medication.

Side Effects

Be sure to discuss any side-effects with your veterinarian immediately. Particularly with a drug like trilostane, which affects hormone levels, side effects may be related to lower than normal hormone levels, causing metabolic disturbances. Your veterinarian may recommend discontinuing the trilostane until blood tests can be performed and analyzed.

The more-common side effects include loss of appetite, lethargy, weakness, vomiting, and diarrhea. Rarely, fatalities have been reported.

Very rarely, trilostane can cause the adrenal gland to stop functioning totally. If this occurs, the change is permanent and your animal will need to be on lifelong supplementation of both corticosteroids and mineralocorticoids.


Keep this and all drugs out of reach of children. Trilostane is a prescription drug and should be used according to your veterinarian’s directions, and given only to the animal for which it was prescribed. Do not give this medication to a person.

Trilostane may affect the levels of some of the other hormones produced in the adrenal gland. There are some dogs in which trilostane blocks the synthesis of these other hormones (mineralocorticoids) more effectively than the targeted corticosteroid. These dogs are at increased risk for metabolic problems including dehydration, weakness, and abnormal serum electrolyte levels.

Trilostane is metabolized by the liver. It generally is not used in animals with liver or kidney problems. Trilostane should be used with caution in animals that are anemic.

Trilostane should not be used in animals that are pregnant or nursing.

Drug Interactions

Be sure to review with your veterinarian any medications or supplements your pet may be receiving.

Potassium-sparing diuretics should be avoided because of potential high serum potassium levels.


If you suspect your pet or another animal was overdosed accidentally or has eaten this medication inadvertently, contact your veterinarian or the A.S.P.C.A.’s Animal Poison Control Center at 888.426.4435. Always bring the prescription container with you when you take your pet for treatment.

If you or someone else has accidentally ingested this medication call the National Capital Poison Center at 800.222.1222.


Different strengths or dosage forms of trilostane may have different storage requirements. Read the labeling or ask your pharmacist for the storage requirements of the prescription you receive.

More Information About This Medication

Cushing’s disease (hyperadrenocorticism) is caused by excess corticosteroid. Animals with Cushing’s disease usually present to the veterinarian with clinical signs that may include increased thirst and urination, excessive hunger, weight gain, decreased activity, chronic skin infections, hair loss, and occasionally, behavior changes.

In the dog, about 85% of cases of Cushing’s disease are due to pituitary-dependant hyperadrenocorticism (PDH). PDH is caused by a benign tumor on the pituitary gland, which overstimulates the adrenal gland. PDH is a disease of middle-aged dogs and some breeds, including West Highland White Terriers, Poodles, Dachshunds, Boston Terriers and Boxers, have a higher incidence of PDH. Less common causes of Cushing’s disease include malignant or benign tumors of the adrenal gland and overuse of corticosteroid drugs.
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Popular Trilostane Dosage Forms

Dosage options starting at $0.58 per dose

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Trilostane: Oral Suspension

Water based oral suspension with a wide variety of flavoring options.