Trilostane for Dogs with Cushing's Disease: Complete Treatment Guide

Cushing's disease (hyperadrenocorticism) is one of the most common endocrine disorders in middle-aged and older dogs, affecting an estimated 1 to 2 out of every 1,000 dogs annually. When your veterinarian confirms the diagnosis, the conversation almost always turns to one medication: trilostane (brand name Vetoryl®). Since receiving FDA approval in 2008, trilostane has become the gold-standard medical treatment for pituitary-dependent Cushing's disease in dogs, replacing older options like mitotane (Lysodren®) as the first-line therapy most veterinary endocrinologists recommend.

This guide walks you through everything you need to know about trilostane for dogs with Cushing's disease — from how the drug works and what dosing looks like, to the real costs of treatment, monitoring schedules, and the red-flag symptoms that mean you need to call your vet immediately. As always, consult your veterinarian before making any changes to your dog's medication or treatment plan.

What Is Cushing's Disease in Dogs?

Cushing's disease occurs when a dog's body produces excessive levels of cortisol, a steroid hormone normally released by the adrenal glands in response to stress. In roughly 80–85% of cases, the root cause is a benign tumor on the pituitary gland (pituitary-dependent hyperadrenocorticism, or PDH) that overstimulates the adrenal glands with adrenocorticotropic hormone (ACTH). The remaining 15–20% of cases stem from a tumor on one or both adrenal glands themselves (adrenal-dependent hyperadrenocorticism, or ADH).

A third form — iatrogenic Cushing's syndrome — occurs when a dog has received prolonged corticosteroid medications (prednisone, dexamethasone) for conditions like allergies or autoimmune disease. This form resolves when the steroid medication is gradually tapered under veterinary supervision.

Left untreated, Cushing's disease progressively damages organ systems. Excess cortisol suppresses the immune system, weakens muscles, thins the skin, and disrupts blood sugar regulation — creating cascading health problems that shorten a dog's life and diminish their quality of life significantly.

Symptoms of Cushing's Disease: What to Watch For

Cushing's disease is sometimes called "the great imitator" because its symptoms develop gradually and overlap with many other conditions — including normal aging. Many owners don't realize their dog was symptomatic until they look back after a diagnosis and recognize the pattern. The table below organizes symptoms by how they typically present, from early subtle changes to advanced clinical signs.

Severity	Symptoms	What Owners Often Notice
Early Warning Signs	Increased thirst (polydipsia) Increased urination (polyuria) Increased appetite (polyphagia) Mild pot-bellied appearance	Water bowl empties faster; more frequent potty breaks or indoor accidents; dog begs for food constantly
Moderate / Progressive Signs	Hair loss (symmetrical, bilateral — typically along flanks and trunk) Thin, fragile skin that bruises easily Muscle wasting (especially in limbs) Noticeable abdominal enlargement Recurrent skin infections Calcium deposits in skin (calcinosis cutis)	Coat looks patchy or "moth-eaten"; dog looks like they've gained weight but feels bony along the spine; skin tears from minor scratches
Advanced / Severe Signs	Lethargy and exercise intolerance Panting excessively at rest Recurrent urinary tract infections High blood pressure Diabetes mellitus (comorbidity) Neurological signs (with macroadenoma): disorientation, pacing, head pressing, seizures Pulmonary thromboembolism (blood clots in lungs)	Dog seems to age rapidly; collapses after mild exertion; confusion or behavioral changes suggest pituitary tumor growth pressing on brain tissue

Important: The neurological symptoms listed under advanced signs — disorientation, head pressing, seizures — may indicate a pituitary macroadenoma (tumor larger than 1 cm) that is compressing brain tissue. This is a veterinary emergency. Call your vet or an emergency clinic immediately.

How Veterinarians Diagnose Cushing's Disease

Diagnosing Cushing's disease is a multi-step process. No single test is definitive on its own, and false positives are common — especially in dogs with other illnesses (a phenomenon called "stress hypercortisolism"). Your veterinarian will typically follow a staged diagnostic approach:

Total diagnostic cost range: $600–$1,500 for a typical uncomplicated case through Step 3, rising to $2,000–$4,500 if advanced imaging is needed. According to the Merck Veterinary Manual, accurate differentiation between PDH and ADH is critical because treatment strategies differ substantially.

Trilostane for Dogs: How It Treats Cushing's Disease

Trilostane (Vetoryl®) is a competitive inhibitor of the enzyme 3-beta-hydroxysteroid dehydrogenase (3β-HSD), which is essential for cortisol synthesis in the adrenal glands. By blocking this enzyme, trilostane reduces cortisol production to more normal levels without destroying adrenal tissue — a key advantage over the older drug mitotane, which works by chemically ablating the adrenal cortex.

Trilostane is FDA-approved for treating PDH in dogs and is also used off-label for ADH in cases where surgery isn't an option. The medication comes in capsule form (available in 10 mg, 30 mg, 60 mg, and 120 mg strengths) and is typically administered once or twice daily with food to improve absorption.

Treatment	Mechanism	Success Rate	Monthly Cost	Key Considerations
Trilostane (Vetoryl®)	Enzyme inhibitor — blocks cortisol synthesis	~80–85% clinical improvement	$40–$180/month depending on dose and dog size	Reversible; requires regular ACTH stim monitoring; must be given with food
Mitotane (Lysodren®)	Adrenocorticolysis — destroys adrenal cortex cells	~75–80% clinical improvement	$25–$80/month	Irreversible; higher risk of permanent Addisonian crisis; less commonly used now
Adrenalectomy (Surgery for ADH)	Surgical removal of affected adrenal gland	~70–80% long-term remission if benign and fully resected	$3,000–$7,000 one-time	Curative potential for ADH; requires experienced surgeon; perioperative risks
Radiation Therapy (for Macroadenoma)	Targets and shrinks pituitary tumor	~75% tumor size reduction; neurological improvement in most cases	$4,000–$8,000 one-time	Does not resolve cortisol excess immediately; trilostane still needed concurrently

Trilostane Dosing Guidelines

Your veterinarian will determine the exact dose based on your dog's weight, clinical signs, and ACTH stimulation test results. The typical starting dose is 0.5–1.0 mg per pound (1–2 mg/kg) once daily, administered with food. Some dogs require twice-daily dosing as treatment progresses. Dose adjustments are made based on monitoring results, not weight alone.

Dog Weight	Typical Starting Dose	Available Capsule Strength
Under 11 lb (5 kg)	10 mg once daily	10 mg capsule
11–22 lb (5–10 kg)	10–30 mg once daily	10 mg or 30 mg capsule
22–44 lb (10–20 kg)	30–60 mg once daily	30 mg or 60 mg capsule
44–88 lb (20–40 kg)	60–120 mg once daily	60 mg or 120 mg capsule
Over 88 lb (40+ kg)	120 mg once or twice daily	120 mg capsule (may need multiple)

Never split or open trilostane capsules. The medication should be given whole. If your dog's calculated dose falls between available capsule strengths, your veterinarian will typically start at the lower dose and adjust upward based on monitoring.

Trilostane Side Effects and Warning Signs

Most dogs tolerate trilostane well, and side effects — when they occur — are usually mild and dose-dependent. However, because trilostane suppresses cortisol production, there is a risk of over-suppression leading to an Addisonian crisis (hypoadrenocorticism), which is life-threatening and requires immediate veterinary intervention.

Side Effect	Frequency	Action Required
Mild lethargy or decreased appetite	Common (15–20% of dogs)	Monitor; report at next check-in; may resolve with dose timing adjustment
Vomiting or diarrhea	Occasional (5–10%)	Withhold dose and contact vet if persistent (>24 hours) or severe
Electrolyte imbalance (elevated potassium)	Uncommon but significant	Detected on monitoring bloodwork; dose adjustment required
Adrenal necrosis (Addisonian crisis)	Rare (2–3%) but life-threatening	EMERGENCY — immediate veterinary care required

Monitoring Schedule: The Key to Safe Trilostane Treatment

The single most important factor in safe, effective trilostane treatment is consistent monitoring. Unlike many medications where you find a dose and stay on it indefinitely, trilostane requires ongoing dose adjustments based on your dog's cortisol response. The monitoring protocol typically follows this schedule:

• 10–14 days after starting trilostane: First ACTH stimulation test and electrolyte panel. Your vet will check whether cortisol levels have decreased to the target range (post-ACTH cortisol between 2–7 µg/dL in most protocols) and screen for potassium elevation.
• 30 days after starting: Second ACTH stimulation test and full blood chemistry panel. Dose adjustments are common at this stage.
• 60 days: Third monitoring visit. Many dogs reach a stable dose by this point.
• Every 3 months for the first year: ACTH stimulation test, blood chemistry, and clinical assessment.
• Every 6 months thereafter: Once stable, most dogs transition to semiannual monitoring for life.

Each monitoring visit typically costs $120–$250 (ACTH stim test plus bloodwork). That means the first year of monitoring alone can cost $500–$1,000 on top of medication costs. This is non-negotiable — skipping monitoring visits is the leading cause of trilostane complications in clinical practice.

A practical tip from experience: Schedule ACTH stimulation tests for the morning and give the trilostane dose at the usual time that morning. The test measures cortisol response 1–2 hours after the dose, which gives your vet the most clinically useful data. Always use the same laboratory for consistency — reference ranges vary between labs, and switching labs can make it difficult to track trends accurately.

Prognosis and Life Expectancy with Cushing's Disease

The prognosis for dogs with Cushing's disease depends heavily on the type (PDH vs. ADH), the presence of complications, and how well the condition is managed. Here's what the data shows:

Condition	Median Survival Time	Key Factors
PDH treated with trilostane	2.0–2.5 years (many live 3–5+ years with good management)	Consistent monitoring, appropriate dose management, absence of macroadenoma
PDH with pituitary macroadenoma	6–18 months (varies with tumor growth rate and treatment)	Radiation therapy can extend survival; neurological signs worsen prognosis
ADH — benign tumor, surgically removed	3–4+ years (potentially curative)	Complete surgical resection; no metastasis; experienced surgeon
ADH — malignant adrenal carcinoma	6–12 months	High metastatic rate; vascular invasion common
Untreated Cushing's disease	Variable, but progressive decline with high complication risk	Diabetes, infections, thromboembolism, and organ failure are common endpoints

These figures represent medians from published veterinary literature, including data referenced by the Journal of the American Veterinary Medical Association. Individual outcomes vary considerably. Many dogs with well-managed PDH live full, comfortable lives for years after diagnosis — I've worked with owners whose dogs thrived for 5+ years on trilostane with diligent monitoring.

The Real Cost of Treating Cushing's Disease in Dogs

Cushing's disease is a chronic condition requiring lifelong management, and the costs add up. Here's a realistic breakdown so you can plan accordingly:

Expense Category	Year 1 (Diagnosis + Stabilization)	Year 2+ (Ongoing Maintenance)
Initial diagnosis (bloodwork, LDDST, imaging)	$600–$1,500	—
Trilostane medication (varies by dose/weight)	$480–$2,160	$480–$2,160
Monitoring visits (ACTH stim + bloodwork)	$500–$1,000 (4–5 visits)	$240–$500 (2 visits)
Managing complications (UTIs, skin infections)	$100–$500	$100–$400
TOTAL ESTIMATED ANNUAL COST	$1,680–$5,160	$820–$3,060

Worst-case scenarios — such as an Addisonian crisis requiring hospitalization ($1,500–$4,000), radiation therapy for a macroadenoma ($4,000–$8,000), or adrenalectomy ($3,000–$7,000) — can push total costs significantly higher. Pet insurance that covers chronic conditions can offset a substantial portion of these costs, but most policies require enrollment before diagnosis. If your dog is already diagnosed, look into prescription discount programs or ask your vet about compounded trilostane, which can be 30–50% less expensive than brand-name Vetoryl®.

Home Care and Daily Management

Managing a dog on trilostane goes beyond giving a pill each morning. Here's what daily life looks like and what you can do at home to support your dog's treatment:

Daily Routine

• Administer trilostane with food — ideally the same meal at the same time each day. A high-fat meal improves absorption. Set a daily phone alarm so you never miss or double a dose.
• Monitor water intake — track how many bowls or cups of water your dog drinks daily. A sudden increase or decrease is worth noting for your vet.
• Watch appetite and energy levels — keep a simple daily log (a notes app works fine) rating your dog's appetite, energy, and any symptoms on a 1–5 scale. This data is invaluable during monitoring visits.
• Manage potty access — even on treatment, some dogs continue to drink and urinate more than normal, especially early on. Ensure consistent outdoor access or indoor potty options.

Lifestyle Adjustments

• Skin care: Dogs with Cushing's have thin, fragile skin. Avoid rough play that causes scratches; use soft brushes; check for hot spots or infections weekly.
• Exercise: Moderate, consistent exercise is beneficial. Avoid sudden intense activity if your dog has muscle wasting. Short daily walks are better than weekend warrior sessions.
• Diet: Feed a balanced, AAFCO-approved diet. Moderate protein and moderate fat are generally recommended. Avoid high-sodium foods, as Cushing's dogs are prone to hypertension. Discuss specific diet choices with your veterinarian.
• Infection vigilance: Cortisol suppression means your dog's immune system is compromised. Watch for recurrent ear infections, UTIs (frequent small urinations, licking genitals, foul-smelling urine), and skin infections. Report these promptly — they won't resolve on their own and can worsen quickly.
• Stress reduction: Stress triggers cortisol release, which counteracts treatment. Keep routines predictable, minimize boarding when possible, and use calming aids (Adaptil® diffusers, calming supplements like L-theanine) during unavoidable stressors like vet visits or travel.

Prevention and Comorbidity Management

There is no way to prevent Cushing's disease itself — pituitary and adrenal tumors are not preventable through diet, exercise, or lifestyle changes. However, you can prevent or minimize secondary complications:

• Prevent iatrogenic Cushing's: If your dog requires corticosteroids for another condition, work with your vet to use the lowest effective dose for the shortest duration. Ask about steroid-sparing alternatives (cyclosporine, oclacitinib/Apoquel®) for chronic allergy management.
• Manage comorbidities: Up to 20% of dogs with Cushing's develop concurrent diabetes mellitus. Regular bloodwork catches this early. Hypertension, pancreatitis, and gallbladder mucoceles are also more common — your vet will screen for these during monitoring visits.
• Dental care: Immunosuppressed dogs are more vulnerable to oral infections. Brush teeth daily or use veterinary-approved dental chews and schedule professional cleanings as recommended.

Frequently Asked Questions About Trilostane and Cushing's Disease

Disclaimer: This article is for informational purposes only and does not replace professional veterinary advice. Cushing's disease diagnosis, treatment, and monitoring must be managed by a licensed veterinarian. Always consult your veterinarian before starting, stopping, or adjusting any medication for your dog.