Trilostane, Mitotane & Treatment Options

Watching your dog drink obsessively from the water bowl, have accidents in the house despite years of reliable potty training, and develop a pot-bellied appearance can be alarming. These are hallmark signs of hyperadrenocorticism, commonly known as Cushing's disease — a condition where the adrenal glands produce excessive cortisol. Approximately 1 to 2 out of every 1,000 dogs develop Cushing's disease each year, making it one of the most frequently diagnosed endocrine disorders in middle-aged and older dogs, according to the Merck Veterinary Manual.

Managing this condition requires a clear understanding of available canine Cushing's medication options, realistic expectations about treatment outcomes, and a commitment to lifelong monitoring. This guide covers everything from diagnosis through daily management so you can walk into your veterinary appointment prepared.

What Is Cushing's Disease in Dogs?

Cushing's disease occurs when a dog's body produces chronically elevated levels of cortisol, the stress hormone. Cortisol is essential for regulating metabolism, immune response, and blood pressure, but too much of it causes widespread systemic damage over time.

There are three forms of the disease:

Understanding which type your dog has is critical because it determines whether canine Cushing's medication alone will suffice or whether surgical intervention offers a better prognosis.

Recognizing the Symptoms: From Early Warnings to Advanced Signs

Cushing's disease is notoriously insidious. Symptoms develop gradually over months or even years, and many owners initially attribute changes to normal aging. Catching the disease early significantly improves treatment outcomes and reduces the risk of secondary complications like diabetes mellitus, urinary tract infections, and hypertension.

Early Warning Signs (Often Missed)

• Increased thirst (polydipsia): Your dog drinks noticeably more water — often exceeding 100 mL per kg of body weight per day (normal is roughly 50–60 mL/kg/day)
• Increased urination (polyuria): More frequent bathroom breaks, larger volumes, or new indoor accidents in a previously house-trained dog
• Increased appetite (polyphagia): Begging more intensely, scavenging, or seeming insatiable at mealtimes
• Mild panting: Heavier breathing at rest without exertion or heat exposure
• Slightly reduced energy: Less enthusiasm for walks, longer naps, slower to get up

Advanced Symptoms (Typically Prompt Veterinary Visits)

• Pot-bellied appearance: Abdominal distension caused by fat redistribution, muscle wasting, and liver enlargement (hepatomegaly)
• Bilateral symmetric hair loss (alopecia): Thinning coat on the flanks, trunk, and abdomen — typically sparing the head and legs
• Thin, fragile skin: Skin tears easily, wounds heal slowly, visible bruising
• Calcinosis cutis: Hard, calcium-encrusted patches on the skin, especially along the back and neck
• Muscle wasting: Visible thinning of the limbs, particularly the temporal and limb muscles, creating a "bony" appearance
• Recurrent skin and urinary tract infections: Cortisol suppresses immune function, making infections more frequent and harder to clear
• Testicular atrophy (intact males) or irregular heat cycles (intact females)

Which Breeds Are Prone to Cushing's Disease?

While any dog can develop Cushing's disease, certain breeds carry significantly higher risk. According to the American Kennel Club, predisposed breeds include:

How Is Cushing's Disease Diagnosed?

Diagnosing Cushing's disease is a multi-step process because no single test provides a definitive answer. Your veterinarian will typically move through screening tests, then confirmatory tests, and finally differentiation tests to determine whether the cause is pituitary or adrenal. Expect the diagnostic process to take 1–3 weeks from initial blood work to final results.

Step 1: Initial Screening

Your vet will start with a complete blood count (CBC), serum biochemistry panel, and urinalysis. While these don't diagnose Cushing's directly, they reveal supporting evidence:

• Elevated alkaline phosphatase (ALP) — seen in approximately 85–90% of Cushing's dogs
• Elevated ALT (liver enzyme)
• Stress leukogram (high neutrophils, low lymphocytes and eosinophils)
• Dilute urine (low specific gravity, often below 1.020)
• Elevated cholesterol and triglycerides

Step 2: Confirmatory Endocrine Tests

Step 3: Differentiation and Imaging

Once Cushing's is confirmed, your vet needs to determine the type:

• High-Dose Dexamethasone Suppression Test (HDDST): Helps differentiate PDH from ADH — pituitary tumors partially suppress at higher doses; adrenal tumors do not. Cost: $200–$350.
• Endogenous ACTH levels: Low ACTH suggests adrenal tumor; high or normal ACTH suggests pituitary tumor. Cost: $150–$250.
• Abdominal ultrasound: Visualizes adrenal gland size — bilateral enlargement suggests PDH; one enlarged and one atrophied gland suggests ADH. Also screens for other abdominal pathology. Cost: $350–$600.
• MRI or CT of the brain: Recommended if neurological signs are present or if a pituitary macrotumor (over 10 mm) is suspected. Cost: $1,500–$3,000.

Canine Cushing's Medication Options: Trilostane, Mitotane & Beyond

Once your veterinarian has confirmed the diagnosis and identified the type, treatment planning begins. The two primary medications used for canine Cushing's disease are trilostane and mitotane. Each has distinct mechanisms, monitoring requirements, and risk profiles.

Trilostane (Vetoryl®) — First-Line Treatment

Trilostane is an FDA-approved medication specifically for treating Cushing's disease in dogs. It works by inhibiting the enzyme 3-beta-hydroxysteroid dehydrogenase, which blocks cortisol synthesis in the adrenal glands. It does not treat the underlying tumor — it manages the hormonal excess.

• Brand name: Vetoryl® (Dechra Pharmaceuticals)
• Dosing: Typically started at 1–3 mg/kg once daily with food, though some veterinarians split dosing to twice daily for smoother cortisol control
• Available capsule sizes: 10 mg, 30 mg, 60 mg, 120 mg
• Cost: Approximately $1.50–$4.00 per capsule depending on dose. Monthly cost for a 30 lb (14 kg) dog: $60–$150. For a 70 lb (32 kg) dog: $120–$280/month.
• Monitoring: ACTH stimulation test at 10–14 days, 30 days, 90 days, then every 3–6 months. Blood work (electrolytes, kidney values) at each recheck.

Mitotane (Lysodren®) — Alternative Option

Mitotane is a chemotherapeutic agent that selectively destroys the cortisol-producing zones of the adrenal cortex. It's an older treatment that was the standard of care before trilostane became available. It's still used in certain cases, particularly when trilostane is ineffective or poorly tolerated.

• Brand name: Lysodren® (also available as compounded generic)
• Dosing: Induction phase (daily dosing for 5–10 days until cortisol levels drop), then maintenance phase (1–2 doses per week)
• Cost: Approximately $1.00–$3.00 per tablet. Monthly maintenance cost: $30–$100.
• Risk profile: Higher risk of Addisonian crisis (overtreatment causing dangerously low cortisol). Requires careful monitoring during induction.

Other Medications and Adjuncts

Surgical Options and When They're Recommended

For dogs with adrenal-dependent Cushing's disease, surgical removal of the affected adrenal gland (adrenalectomy) can be curative. This is typically performed by a board-certified veterinary surgeon at a specialty center.

• Success rate: Approximately 70–80% of dogs with benign adrenal tumors achieve long-term remission after surgery
• Surgical cost: $3,000–$7,000 (includes pre-surgical imaging, anesthesia, hospitalization, and post-operative care)
• Risks: Hemorrhage, pancreatitis, thromboembolism, and perioperative mortality (reported at approximately 10–20% in some studies, lower at experienced centers)
• Post-surgery: If the contralateral adrenal gland is atrophied, the dog may need temporary cortisol supplementation (prednisone) for weeks to months while it recovers function

For pituitary-dependent Cushing's, radiation therapy may be considered if a macrotumor is causing neurological signs (head pressing, circling, vision changes). Hypophysectomy (surgical removal of the pituitary gland) is performed at a limited number of veterinary institutions, primarily in Europe, and is rarely available in the United States.

Prognosis and Life Expectancy

Most dog owners want a straightforward answer: how long will my dog live with Cushing's disease? The prognosis depends on the type, stage at diagnosis, and how well the disease responds to treatment.

These figures represent median survival times from veterinary oncology and internal medicine literature. Individual dogs vary considerably — many dogs with well-controlled pituitary-dependent Cushing's disease live full, comfortable lives for years beyond these medians.

Home Care, Daily Management & Monitoring

Managing a dog on canine Cushing's medication is a long-term commitment that involves daily routines and regular veterinary check-ins. Here's what day-to-day life looks like:

Daily Medication Administration

• Give trilostane with food — absorption is significantly better with a meal containing some fat
• Administer at the same time each day to maintain consistent cortisol suppression
• Never double a dose if you miss one — skip it and resume the next scheduled dose
• Keep a medication log noting the date, time, and any observed side effects

What to Monitor at Home

• Water intake: Measure daily consumption. A decrease from pre-treatment levels is one of the earliest signs the medication is working. Target: return to approximately 50–60 mL/kg/day.
• Urination frequency and volume: Should decrease as cortisol normalizes.
• Appetite: Excessive hunger should moderate within 2–4 weeks of effective treatment.
• Energy levels: Many dogs actually become more active once cortisol is controlled, though some may seem slightly less energetic initially.
• Coat regrowth: Hair typically begins returning within 3–6 months, though full regrowth may take 6–12 months.
• Signs of overtreatment (Addisonian crisis): Vomiting, diarrhea, lethargy, weakness, collapse, loss of appetite — these require immediate veterinary attention.

Lifestyle Adjustments

• Consistent access to water: Never restrict water for a dog with Cushing's, even during the adjustment period. Dehydration can be dangerous.
• Frequent bathroom breaks: Until medication stabilizes cortisol levels, your dog may still need more frequent outdoor access.
• Skin care: Dogs with calcinosis cutis or thin skin may benefit from gentle, moisturizing shampoos. Avoid harsh grooming products. Discuss topical treatments for skin infections with your vet.
• Weight management: As cortisol normalizes, your dog's appetite will decrease. Adjust food portions accordingly to prevent obesity, which compounds joint stress and metabolic risk.
• Infection vigilance: Because immune function is compromised, monitor for recurring ear infections, skin hot spots, and urinary tract infections. Report any signs promptly.

The True Cost of Treating Canine Cushing's Disease

Cushing's disease is a chronic condition requiring lifelong management. Understanding the financial commitment helps you plan realistically and avoid gaps in treatment.

Pet insurance can significantly offset these costs if your dog was enrolled before diagnosis. Many comprehensive policies cover 70–90% of eligible expenses after deductible. However, pre-existing condition exclusions mean that insurance must be in place before symptoms appear to be useful.

Prevention and Risk Reduction

Because the most common form of Cushing's disease (pituitary-dependent) is caused by spontaneous benign tumors, there is no proven way to prevent it. However, you can take steps to reduce risk and catch the disease early:

• Avoid unnecessary corticosteroid use: The one preventable form — iatrogenic Cushing's — results from prolonged steroid administration. Discuss alternatives with your vet before starting long-term prednisone or similar drugs for allergies, arthritis, or other conditions.
• Annual senior wellness exams: Dogs over 7 years old should have annual blood work that includes ALP and other liver enzymes. Elevated ALP on routine blood work is often the first clue.
• Track water consumption: Periodically measure how much water your dog drinks in 24 hours. A sustained increase above 100 mL/kg/day warrants investigation.
• Know your breed's risks: If you own a predisposed breed, maintain heightened awareness of early symptoms and discuss Cushing's screening with your veterinarian during annual visits.

Frequently Asked Questions About Canine Cushing's Medication

Can Cushing's disease in dogs be cured?

Adrenal-dependent Cushing's caused by a benign tumor can potentially be cured through surgical removal of the affected adrenal gland. Pituitary-dependent Cushing's, which accounts for 80–85% of cases, cannot be cured but can be effectively managed with lifelong medication. Most dogs on well-managed trilostane therapy live comfortable lives with good quality of life for years.

How quickly does canine Cushing's medication start working?

Most owners notice reduced thirst and urination within 1–3 weeks of starting trilostane. Appetite normalization typically follows within 2–4 weeks. Coat regrowth is the slowest improvement, often taking 3–6 months to become visible. Your vet will perform an ACTH stimulation test at the 10–14 day mark to verify that cortisol levels are within the target range.

What happens if I can't afford Cushing's medication for my dog?

Untreated Cushing's disease progressively worsens and leads to serious complications including diabetes, pancreatitis, hypertension, kidney damage, and blood clots. If cost is a barrier, discuss options with your veterinarian — some offer payment plans, and compounded trilostane may be available at lower cost than brand-name Vetoryl®. Veterinary schools and nonprofit organizations sometimes offer financial assistance for chronic disease management. Never discontinue medication without veterinary guidance, as abrupt cortisol changes can trigger an Addisonian crisis.

Are there natural or holistic treatments for Cushing's disease?

No natural supplement has been shown to replace canine Cushing's medication as an effective treatment. Some supplements like melatonin and flaxseed lignans may provide mild supportive benefits for coat health and cortisol modulation, but they should only be used as adjuncts alongside prescribed medication, never as substitutes. Always discuss any supplements with your veterinarian, as some can interact with trilostane or affect liver function.

Can my dog live a normal life on Cushing's medication?

Yes. Dogs with well-controlled Cushing's disease typically return to near-normal energy levels, maintain healthy appetites, and enjoy regular activities. Many owners report that their dog seems "years younger" once excess cortisol is managed. The key is consistent medication administration, regular veterinary monitoring, and prompt attention to any changes in symptoms.

What is an Addisonian crisis and how do I prevent it?

An Addisonian crisis occurs when cortisol levels drop too low, typically from medication overdose. Symptoms include severe lethargy, vomiting, diarrhea, weakness, and collapse. It is a life-threatening emergency requiring immediate veterinary intervention with intravenous fluids and glucocorticoid administration. Prevention relies on strict adherence to prescribed dosages, never adjusting medication without veterinary guidance, and keeping all scheduled monitoring appointments so your vet can fine-tune the dose before problems develop.

Sources consulted: Merck Veterinary Manual — Hyperadrenocorticism in Dogs, American Kennel Club — Cushing's Disease in Dogs, AVMA Pet Owner Resources. Treatment decisions should always be made in consultation with your veterinarian, ideally a board-certified veterinary internist for complex cases.