If your dog has been diagnosed with Cushing’s disease, your veterinarian may recommend trilostane to help bring their cortisol levels back under control. Cushing’s disease, also known as hyperadrenocorticism or hypercortisolism, causes the body to produce too much cortisol and can lead to familiar symptoms like constant thirst, frequent urination, increased hunger, excessive panting, muscle weakness, and a pot-bellied appearance.
Vetoryl (Trilostane) works by reducing cortisol production in the adrenal glands, which can help ease many of these symptoms and improve your dog’s quality of life. However, finding the right dose is important. Too much trilostane can lower cortisol levels too far, so dogs taking the medication need regular veterinary monitoring and may require dose adjustments over time.
Key Takeaways
Trilostane is primarily used to manage pituitary-dependent and adrenal-dependent Cushing’s disease in dogs.
The medication reduces cortisol production rather than eliminating the underlying pituitary or adrenal tumor responsible for many cases of Cushing’s disease.
Dosage must be individualized. Your veterinarian considers your dog's weight, clinical response, laboratory results, and tolerance rather than relying on a universal dose.
Common side effects include reduced appetite, lethargy, vomiting, diarrhea, and weakness. More serious adverse effects can occur if cortisol production becomes excessively suppressed.
Regular veterinary examinations and blood testing are essential throughout treatment.
What Is Trilostane?
Trilostane is an adrenal-suppressing medication used primarily to manage canine hyperadrenocorticism, commonly known as Cushing’s disease.
The FDA-approved veterinary formulation is sold under the brand name Vetoryl. It is available in multiple capsule strengths so veterinarians can adjust treatment according to an individual dog's needs.
Cushing’s disease causes chronic exposure to excessive cortisol. Although cortisol is essential for normal metabolism, blood pressure, stress responses, immune regulation, and other functions, excessive concentrations over long periods cause characteristic physical and metabolic changes.
Trilostane helps restore a healthier cortisol balance by reducing the adrenal glands’ ability to produce the hormone.
What Is Trilostane Used for in Dogs?
Trilostane is used to manage both major forms of naturally occurring Cushing’s disease in dogs: pituitary-dependent hyperadrenocorticism (PDH) and adrenal-dependent hyperadrenocorticism (ADH).
Pituitary-dependent Cushing’s occurs when a pituitary tumor produces excessive adrenocorticotropic hormone (ACTH). ACTH continuously stimulates the adrenal glands, resulting in excessive cortisol production.
Adrenal-dependent Cushing’s develops when a tumor of an adrenal gland produces excessive cortisol independently of normal pituitary regulation.
Trilostane can reduce cortisol production in either situation, although treatment decisions for an adrenal tumor may also involve evaluating whether surgical removal is appropriate.
How Does Trilostane Work?
Trilostane works by inhibiting an adrenal enzyme called 3-beta-hydroxysteroid dehydrogenase, which is required for several steps in steroid hormone production.
Blocking this enzyme reduces the adrenal glands’ ability to synthesize cortisol. Production of some other adrenal steroid hormones can also be affected.
This mechanism is why careful dosing is essential.
The goal is not to eliminate cortisol. Your dog needs cortisol for normal physiological function. Instead, treatment aims to reduce excessive cortisol enough to control Cushing’s symptoms while maintaining sufficient adrenal function.
If cortisol production becomes excessively suppressed, your dog can develop signs of hypoadrenocorticism, or Addison’s disease.
What Symptoms Can Trilostane Improve?
Successful trilostane treatment can improve many of the characteristic clinical signs caused by excessive cortisol.
These include:
- Excessive thirst
- Frequent urination
- Increased appetite
- Excessive panting
- Pot-bellied abdomen
- Muscle weakness
- Reduced exercise tolerance
- Skin and coat changes
- Recurrent infections
Not every symptom improves at the same speed.
Changes in excessive drinking, urination, appetite, and panting may become noticeable relatively early. Hair regrowth, skin improvement, muscle recovery, and changes in body shape generally take longer because damaged tissues need time to recover.
Your veterinarian will evaluate both laboratory findings and changes you observe at home when determining whether treatment is working.
What Is the Trilostane Dosage for Dogs?
Trilostane dosage must be prescribed and adjusted by a veterinarian because dogs vary considerably in their response to the medication.
The U.S. prescribing information for Vetoryl lists an initial dosage range of 2.2–6.7 mg/kg (1–3 mg/lb) orally once daily, using the lowest possible dose based on body weight and available capsule sizes.
However, this labeled range should not be used as a do-it-yourself dosing formula.
Veterinarians increasingly use individualized dosing strategies, and published studies have investigated lower-dose and twice-daily protocols. The appropriate approach depends on your dog's disease, clinical signs, laboratory findings, response to treatment, and veterinarian's assessment.
Never increase, decrease, split, or change the frequency of trilostane without veterinary guidance.
Should Trilostane Be Given With Food?
Yes. Vetoryl prescribing information recommends administering trilostane with food.
Giving the medication consistently in relation to meals helps provide more predictable absorption and makes monitoring results easier to interpret.
Try to give each dose at approximately the same time and in the same manner every day.
Consistency becomes particularly important when your veterinarian performs monitoring tests because cortisol measurements may be interpreted in relation to when your dog received the medication.
If your dog stops eating, becomes ill, vomits, develops diarrhea, or appears unusually lethargic or weak, contact your veterinarian rather than simply giving the next dose as usual.
Is Trilostane Given Once or Twice a Day?
The FDA-approved Vetoryl labeling recommends once-daily administration initially. However, some dogs do not maintain adequate symptom control throughout the entire 24-hour period.
Veterinarians may consider twice-daily administration in selected dogs when the clinical response does not last through the day.
Veterinary studies have also investigated lower-dose twice-daily protocols, with some demonstrating effective control of canine hyperadrenocorticism.
That does not mean twice-daily dosing is automatically better. More frequent administration can change the degree and duration of adrenal suppression, so dosing frequency should only be changed by the veterinarian monitoring your dog.
How Long Does Trilostane Take to Work?
Some Cushing’s symptoms may begin improving within the first few weeks of treatment, but the complete response takes longer.
Excessive drinking, urination, appetite, and panting are often among the first changes owners notice.
Physical changes such as muscle weakness, a pot-bellied appearance, thin skin, and hair loss may require several months to improve.
Finding the appropriate dose can also take time. Your veterinarian may need to adjust treatment based on your dog's clinical response and monitoring results.
Cushing’s disease is generally managed as a long-term condition, so the objective is consistent control rather than an immediate cure.
How Is a Dog Monitored While Taking Trilostane?
Close monitoring is essential because both inadequate and excessive cortisol suppression can cause problems.
The Vetoryl monitoring protocol recommends reassessment after treatment begins, followed by additional checks as therapy continues. Monitoring commonly involves your dog's clinical signs, physical examination, serum biochemistry and electrolytes, and assessment of adrenal function.
Monitoring is particularly important after any dose change.
Your veterinarian will also want to know what you observe at home, including changes in:
- Water consumption
- Urination
- Appetite
- Energy
- Panting
- Vomiting or diarrhea
- Weakness
Never skip follow-up testing simply because your dog appears better. A dog can develop abnormal adrenal function before every problem is obvious at home.
What Is an ACTH Stimulation Test?
An ACTH stimulation test evaluates how your dog's adrenal glands respond when stimulated by synthetic adrenocorticotropic hormone.
Blood is collected to measure cortisol, ACTH is administered, and cortisol is measured again after stimulation.
The test has traditionally been used alongside clinical signs and blood chemistry to monitor dogs receiving trilostane.
Timing matters because trilostane's effect on cortisol changes during the hours after administration. Vetoryl guidance specifies ACTH stimulation testing approximately four to six hours after the medication is administered with food.
Monitoring approaches continue to evolve, and veterinarians may incorporate other cortisol measurements and clinical assessments depending on the patient and current protocols.
What Are the Common Side Effects of Trilostane in Dogs?
The most commonly reported adverse effects include gastrointestinal symptoms and decreased energy.
Potential side effects include:
- Reduced appetite
- Lethargy or depression
- Vomiting
- Diarrhea
- Weakness
- Shaking or shivering
Changes in kidney values, liver enzymes, sodium, and potassium can also occur, which is one reason routine blood testing is necessary.
Mild gastrointestinal symptoms still deserve veterinary attention because they can overlap with early signs of excessive adrenal suppression.
Do not assume vomiting or lethargy is simply a harmless adjustment to the medication.
What Are the Serious Side Effects of Trilostane?
The most important risk of trilostane is excessive suppression of adrenal hormone production.
This can result in hypoadrenocorticism, commonly called Addison’s disease, or an Addisonian crisis in severe cases.
Warning signs can include:
- Severe lethargy
- Weakness
- Loss of appetite
- Repeated vomiting
- Diarrhea
- Shaking
- Collapse
Serious electrolyte abnormalities can also develop. Rarely, adrenal gland injury or necrosis has been reported.
These complications can become life-threatening.
If your dog becomes unwell while taking trilostane, follow your veterinarian's instructions regarding withholding medication and contact the veterinary practice promptly. Severe weakness, collapse, repeated vomiting, or other signs of acute illness warrant urgent veterinary care.
Can Trilostane Cause Addison’s Disease?
Studies have shown that Trilostane can cause Addison's disease in dogs. This occurs when a dogs adrenal function is suppressed enough to cause hypoadrenocorticism.
Cushing’s disease involves excessive cortisol, while Addison’s disease involves insufficient adrenal hormone activity. Treatment therefore requires finding a therapeutic balance between these two extremes.
Some cases of trilostane-associated adrenal suppression resolve after the medication is discontinued and appropriate supportive care is provided. More severe adrenal injury may result in prolonged or potentially permanent adrenal insufficiency.
This risk is one of the main reasons trilostane should never be administered without regular veterinary supervision.
Which Dogs Should Not Take Trilostane?
Trilostane is not appropriate for every dog.
According to U.S. Vetoryl safety information, it should not be used in dogs with primary liver or kidney disease or in pregnant dogs. Important drug interactions and other health conditions must also be considered before treatment begins.
Your veterinarian may perform bloodwork and other diagnostic testing before prescribing trilostane to evaluate organ function and establish baseline values.
Provide your veterinarian with a complete list of prescription medications, supplements, herbal products, and other therapies your dog receives.
What Should You Do If You Miss a Trilostane Dose?
If you forget a dose, contact your veterinarian or follow the specific missed-dose instructions they have provided.
Do not automatically double the next dose to compensate.
Because trilostane directly influences adrenal hormone production, maintaining an appropriate dosing schedule is important, but avoiding excessive suppression is more important than attempting to compensate for a forgotten capsule.
If your dog repeatedly misses doses, tell your veterinarian because inconsistent administration can also make clinical signs and monitoring results more difficult to interpret.
What Should You Do If Your Dog Vomits After Trilostane?
Contact your veterinarian if your dog vomits after receiving trilostane, particularly when vomiting is repeated or accompanied by diarrhea, poor appetite, weakness, shaking, or lethargy.
Do not automatically administer another capsule because you cannot reliably determine how much medication was absorbed before your dog vomited.
Vomiting can also be an adverse reaction or a sign of excessive adrenal suppression.
Your veterinarian can advise whether treatment should be temporarily withheld and whether your dog needs examination or laboratory testing.
Can Dogs Take Trilostane Long Term?
Yes. Many dogs with Cushing’s disease require trilostane for the remainder of their lives.
Trilostane controls excessive cortisol production but usually does not remove the underlying pituitary or adrenal abnormality responsible for the disease.
Long-term treatment therefore requires ongoing monitoring.
A dose that works well initially may need adjustment later as your dog's condition, body weight, concurrent illnesses, or response to medication changes.
Regular veterinary follow-ups remain important even after Cushing’s symptoms appear stable.
What Is the Prognosis for Dogs Taking Trilostane?
Many dogs with appropriately managed Cushing’s disease experience substantial improvement in clinical signs and quality of life.
The individual outlook depends on whether Cushing’s is pituitary- or adrenal-dependent, the size and behavior of any underlying tumor, your dog's age, concurrent diseases, and how well cortisol excess can be controlled.
Successful treatment may reduce excessive thirst, urination, appetite, panting, and other uncomfortable symptoms while gradually improving strength, skin health, and overall activity.
Treatment does not eliminate every risk associated with Cushing’s disease, which is why continued monitoring remains important even when your dog seems much better.
Are There Natural Alternative Options to Trilostane?
Some dog owners and integrative veterinarians use natural approaches such as lignans with melatonin and adrenal-support formulas as part of a broader Cushing’s management plan. Lignans are plant-derived compounds that may influence hormone metabolism, while melatonin can affect adrenal steroid pathways and has been used in some veterinary protocols for dogs with adrenal hormone abnormalities.
These options are generally considered most appropriate as supportive or complementary therapies rather than direct replacements for trilostane in dogs with significant hypercortisolism.
Prana Pets Adrenal Support combines herbs such as ashwagandha, astragalus, turmeric, dandelion root, and other botanicals intended to support normal adrenal function, stress response, and overall endocrine balance.
Several of these ingredients have demonstrated anti-inflammatory, antioxidant, adaptogenic, or metabolic effects in broader research, which may make them useful as part of an integrative wellness approach for some dogs.
Current clinical evidence for lignans, melatonin, and herbal adrenal formulas in dogs with Cushing’s disease is still much more limited than the evidence supporting trilostane. More controlled veterinary studies are needed to determine how effective these natural approaches are, which dogs are most likely to benefit, and whether they work best alone or alongside conventional treatment.
Frequently Asked Questions
Is trilostane a cure for Cushing’s disease?
No. Trilostane controls Cushing’s disease by reducing excessive cortisol production, but it generally does not eliminate the pituitary or adrenal abnormality causing the disease. Most dogs therefore require ongoing treatment and monitoring.
How do I know if trilostane is working?
Reduced thirst, urination, appetite, and panting are common early indications that cortisol excess is becoming better controlled. Your veterinarian will combine these changes with physical examination and laboratory monitoring to determine whether the dosage is appropriate.
What happens if the trilostane dose is too high?
Too much trilostane can excessively suppress adrenal hormone production and cause hypoadrenocorticism. Warning signs include poor appetite, vomiting, diarrhea, severe lethargy, weakness, shaking, and collapse. Contact your veterinarian immediately if your dog becomes unwell during treatment.
Does trilostane shrink a pituitary tumor?
No. Trilostane primarily reduces cortisol production by inhibiting steroid synthesis within the adrenal glands. It does not directly shrink the pituitary tumor responsible for most cases of canine Cushing’s disease.
Does trilostane shrink an adrenal tumor?
No. Trilostane can control excessive cortisol production from an adrenal tumor but does not remove the tumor itself. Veterinarians may evaluate whether surgery is appropriate for dogs with adrenal-dependent Cushing’s disease.
Should trilostane be given in the morning or evening?
Vetoryl is commonly administered in the morning with food when prescribed once daily, which also facilitates appropriately timed veterinary monitoring. Follow your veterinarian's specific instructions because some dogs receive different dosing schedules.
What should I monitor at home while my dog takes trilostane?
Pay particular attention to appetite, drinking, urination, energy, panting, vomiting, diarrhea, weakness, and your dog's general demeanor. Improvements can indicate treatment response, while loss of appetite, gastrointestinal problems, unusual lethargy, weakness, or collapse can indicate an adverse reaction requiring veterinary attention.
Can I stop trilostane if my dog seems better?
Do not stop or alter long-term trilostane treatment simply because your dog's Cushing’s symptoms improve. Improvement generally means the medication is controlling cortisol production rather than that the underlying disease has disappeared. Changes should be made with your veterinarian.
References
U.S. Food and Drug Administration. Treating Cushing's Disease in Dogs. U.S. FDA.
Dechra Veterinary Products. Vetoryl (trilostane) Capsules Prescribing Information.
Cook AK, Bond KG. Evaluation of the use of baseline cortisol concentration as a monitoring tool for dogs receiving trilostane as a treatment for hyperadrenocorticism. Journal of the American Veterinary Medical Association. 2010;237(7):801-805.
Feldman EC. Evaluation of twice-daily, low-dose trilostane treatment administered orally in dogs with naturally occurring hyperadrenocorticism. Journal of the American Veterinary Medical Association. 2008;232(9):1321-1328.
Vaughan MA, Feldman EC, Hoar BR, Nelson RW. Evaluation of twice-daily lower-dose trilostane treatment administered orally in dogs with naturally occurring hyperadrenocorticism. Journal of the American Veterinary Medical Association. 2011;238(11):1441-1451.
Behrend EN, Kooistra HS, Nelson R, Reusch CE, Scott-Moncrieff JC. Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement. Journal of Veterinary Internal Medicine. 2013;27(6):1292-1304.
