Trilostane, sold under the brand names Modrenal and Vetoryl among others, is a medication that has been used in the treatment of Cushing's syndrome, Conn's syndrome, and postmenopausal breast cancer in humans. It was withdrawn for use in humans in the United States in the 1990s but was subsequently approved for use in veterinary medicine in the 2000s to treat Cushing's syndrome in dogs. It is taken by mouth.
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 variations 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 are 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.
Precautions
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.