# Canine Hyperadrenocorticism: Treatment Options and Monitoring ## Key Takeaways - Medical management of canine hyperadrenocorticism (HAC) primarily involves trilostane and mitotane, with treatment selection based on tumor type, drug availability, client commitment, and clinician familiarity. - Trilostane competitively inhibits 3-beta-hydroxysteroid dehydrogenase, offering rapid, reversible cortisol reduction with a lower risk of permanent hypoadrenocorticism, but requiring frequent monitoring post-dose change. - Mitotane is an adrenocorticolytic agent that selectively destroys the zona fasciculata and reticularis, leading to delayed onset and a higher risk of permanent hypoadrenocorticism, necessitating intensive induction phase monitoring. - The ACTH stimulation test is the standard biochemical monitoring tool for both agents, assessing adrenal cortex functional reserve, with target post-ACTH cortisol levels typically between 1.0 to 4.1 mcg/dL, interpreted alongside clinical signs. - Common adverse effects for both drugs include gastrointestinal signs (vomiting, diarrhea) and lethargy, with iatrogenic hypoadrenocorticism being the most serious complication requiring immediate drug withdrawal and supportive care. - Monitoring schedules are intensive initially, with rechecks 10-14 days after dose changes for trilostane and frequent testing during induction for mitotane, transitioning to every 3-6 months for long-term management. --- Medical management of canine hyperadrenocorticism (HAC) requires a structured comparison of available adrenosuppressive agents, a clear understanding of their distinct mechanisms and failure modes, and disciplined biochemical monitoring tailored to each drug. This article serves practicing veterinarians selecting initial therapy, adjusting doses, and interpreting monitoring results in dogs with pituitary-dependent and adrenal-dependent disease. It compares trilostane and mitotane as primary medical options, addresses the role of alternative agents, and outlines monitoring protocols that detect both under-treatment and iatrogenic adverse effects. Diagnostic confirmation is assumed and is not reviewed here. Treatment selection hinges on tumor type, drug availability, client commitment, and the clinician's familiarity with each agent's monitoring requirements. The evidence base for medical therapy in canine HAC rests largely on prospective and retrospective clinical studies, with expert consensus guidance available through the American College of Veterinary Internal Medicine consensus statement process [ACVIM consensus statements](https://www.acvim.org/Animal-Owners/Animal-Education/Consensus-Statements). Practicing clinicians should also consult current formulary and label references for dosing specifics, as published protocols continue to evolve. ## At a Glance | Parameter | Trilostane | Mitotane | |---|---|---| | Mechanism | Competitive inhibitor of 3-beta-hydroxysteroid dehydrogenase | Adrenocorticolytic, selectively destroys zona fasciculata and reticularis | | Onset of effect | Rapid, within hours | Delayed, days to weeks | | Primary monitoring test | ACTH stimulation test | ACTH stimulation test | | Target post-ACTH cortisol | 1.0 to 4.1 mcg/dL (varies by reference laboratory) | 1.0 to 4.1 mcg/dL (varies by reference laboratory) | | Common adverse effects | Lethargy, vomiting, diarrhea, weakness | Anorexia, vomiting, lethargy, ataxia | | Risk of permanent hypoadrenocorticism | Low, usually reversible | Higher, may be permanent | | Monitoring frequency | Recheck at 10 to 14 days after dose change, then every 3 to 6 months | Induction phase requires frequent rechecks, then every 3 to 6 months | ## Pathophysiology Relevant to Treatment Hyperadrenocorticism results from chronic glucocorticoid excess, most commonly from a pituitary corticotroph adenoma that drives bilateral adrenal hyperplasia. Adrenal tumors account for a smaller proportion of cases and produce cortisol autonomously, often with blunted or absent ACTH feedback. The treatment target in both forms is the adrenal cortex itself, not the pituitary, because no safe and effective pituitary-directed medical therapy is currently available for dogs. The zona fasciculata and zona reticularis produce cortisol under ACTH drive. The zona glomerulosa produces aldosterone and is regulated primarily by the renin-angiotensin-aldosterone system. Medical therapies differ in their selectivity for these zones, which explains their differing adverse effect profiles. Trilostane inhibits steroidogenesis reversibly across all zones, whereas mitotane causes progressive cellular destruction that can spare or involve the glomerulosa depending on dose and duration. ## Trilostane Trilostane is a synthetic steroid analogue that competitively inhibits 3-beta-hydroxysteroid dehydrogenase, the enzyme that converts pregnenolone to progesterone and 17-hydroxypregnenolone to 17-hydroxyprogesterone. This blockade reduces cortisol synthesis within hours of administration. The effect is reversible, and adrenal function typically recovers when the drug is withdrawn. Trilostane does not destroy adrenocortical cells, which distinguishes it mechanistically from mitotane. The drug is given once or twice daily with food to enhance absorption. Clinical response is usually evident within days, and most dogs show improvement in polyuria, polydipsia, and appetite within the first two weeks. Because the drug's duration of action is shorter than a full day in many dogs, twice-daily dosing is increasingly used when once-daily dosing fails to control clinical signs throughout the day. Adverse effects are dose-related and reflect cortisol withdrawal or oversuppression. Lethargy, vomiting, diarrhea, and decreased appetite are the most common complaints. These signs can occur at any point during therapy, also after dose changes, and they warrant prompt biochemical assessment. Rarely, dogs develop signs of hypocortisolemia with normal post-ACTH cortisol values, a phenomenon attributed to rapid cortisol withdrawal instead of absolute deficiency. ## Mitotane Mitotane is an adrenocorticolytic agent that causes progressive necrosis of the zona fasciculata and zona reticularis while relatively sparing the zona glomerulosa at standard doses. The drug is administered in two phases. The induction phase continues until clinical signs improve or the ACTH stimulation test shows adequate suppression, which typically requires 5 to 14 days. The maintenance phase uses a lower dose given one to three times weekly to sustain adrenocortical destruction. Mitotane requires more intensive monitoring during induction than trilostane. Owners must be instructed to watch for anorexia, vomiting, weakness, or ataxia, any of which may indicate oversuppression and should trigger immediate discontinuation of the drug and biochemical evaluation. The distinction between adequate suppression and iatrogenic hypoadrenocorticism can be narrow, and permanent adrenocortical failure is a recognized complication. Mitotane is less commonly used than trilostane in many regions because of its narrower therapeutic index and more demanding monitoring schedule. However, it remains a valid option, particularly when cost is a limiting factor or when trilostane is unavailable. The choice between the two agents should be made with the owner after a frank discussion of monitoring intensity, adverse effect risk, and the likelihood of permanent hypoadrenocorticism. ## Alternative and Adjunctive Agents Selegiline and ketoconazole have been used historically for canine HAC but are now considered inferior to trilostane and mitotane. Selegiline, a monoamine oxidase inhibitor, has shown inconsistent efficacy and is not recommended as primary therapy. Ketoconazole inhibits adrenal steroidogenesis but has limited potency and requires frequent dosing, making it impractical for long-term management in most dogs. Cabergoline and other dopamine agonists target the pituitary directly and have been used in some dogs with pituitary-dependent HAC. Evidence for their efficacy is limited, and they are not considered first-line therapy. Radiation therapy and hypophysectomy are definitive options for pituitary macroadenomas but are outside the scope of medical management and are addressed in specialty referral settings. ## Monitoring Principles The goal of monitoring is twofold: confirm adequate cortisol suppression and detect oversuppression before it becomes clinically dangerous. The ACTH stimulation test is the standard biochemical monitor for both trilostane and mitotane because it assesses the adrenal cortex's functional reserve under exogenous stimulation. The test should be performed at a consistent time relative to drug administration, and the timing differs between drugs. For trilostane, the ACTH stimulation test is typically performed 4 to 6 hours after the morning dose. For mitotane, the test is performed without regard to the maintenance dose schedule, but it should be done when the dog is clinically stable. Reference intervals for post-ACTH cortisol vary by laboratory, and clinicians should interpret results against their own laboratory's established range instead of a universal number. Clinical response and biochemical results must be interpreted together. A dog with excellent clinical control and a post-ACTH cortisol at the lower end of the target range is well managed, even if the value falls slightly below the laboratory reference interval. Conversely, a dog with persistent polydipsia and a post-ACTH cortisol in the upper target range may require a dose increase despite a numerically acceptable test result. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides practical guidance on interpreting monitoring results in the context of clinical response, and the [ACVIM consensus statement process](https://www.acvim.org/Animal-Owners/Animal-Education/Consensus-Statements) remains the reference framework for monitoring protocols. ## Comparative Selection: Trilostane versus Mitotane The choice between trilostane and mitotane rests on tumor type, clinician experience, client commitment, and financial constraints. For pituitary-dependent hyperadrenocorticism (PDH), trilostane is the most commonly selected first-line agent in contemporary practice because of its reversibility, relatively favorable adverse effect profile, and once-daily dosing options. Mitotane retains a role in cases where trilostane is poorly tolerated, where cost of chronic trilostane therapy is prohibitive, or where the clinician has extensive experience with mitotane protocols. For adrenal-dependent hyperadrenocorticism (ADH), surgical adrenalectomy is the preferred treatment when feasible, but medical management with either agent may be used when surgery is declined or contraindicated. Mitotane is adrenocorticolytic and destroys the zona fasciculata and zona reticularis while sparing the zona glomerulosa at standard dosing. This creates a permanent reduction in cortisol secretory capacity. Trilostane inhibits 3-beta-hydroxysteroid dehydrogenase, blocking cortisol synthesis reversibly without destroying adrenocortical tissue. The practical consequence is that trilostane overdose is managed by drug withdrawal and supportive care, whereas mitotane overdose or iatrogenic destruction may require permanent mineralocorticoid and glucocorticoid replacement. Patient factors that shift the decision include concurrent disease. Dogs with diabetes mellitus, pancreatitis, or hepatic dysfunction may tolerate trilostane better because of its shorter duration of action and lack of cumulative tissue destruction. Dogs with aggressive or rapidly progressive neurologic signs consistent with a macroadenoma are often managed with trilostane while radiation therapy is arranged, since mitotane offers no advantage for mass effect. | Feature | Trilostane | Mitotane | |---|---|---| | Mechanism | Reversible enzyme inhibition | Adrenocorticolytic | | Onset of effect | Days | Days to weeks | | Reversibility | Yes | No | | Mineralocorticoid sparing at standard doses | Usually | Usually, but variable | | Typical monitoring test | ACTH stimulation | ACTH stimulation | | Monitoring frequency | Dense early, then every 3 to 6 months | Dense early, then every 3 to 6 months | | Common adverse effects | Vomiting, diarrhea, lethargy, poor appetite | Vomiting, diarrhea, lethargy, ataxia | | Risk of permanent hypoadrenocorticism | Low | Moderate | | Cost profile | Higher daily cost | Lower daily cost, higher induction cost | | Suitability for PDH | First line | Alternative | | Suitability for ADH | Palliative | Palliative, sometimes preferred | ## Initiation Protocols and Dose Titration Both drugs require a loading or induction phase followed by a maintenance phase, although the structure differs. Trilostane is started at a label-based dose scaled to body weight, with the dose adjusted at recheck intervals based on clinical response and ACTH stimulation results. Current label references and formulary sources must be consulted for starting doses, since published ranges have changed over time and generic formulations may differ in bioavailability. Mitotane induction continues until the ACTH stimulation test shows a specific target cortisol concentration, which typically requires 5 to 14 days of daily dosing. The induction endpoint is defined by the cortisol response, not by clinical improvement, and the owner must be prepared for daily visits or frequent rechecks during this period. Once induction is complete, maintenance dosing is given at intervals that vary by protocol, and the ACTH stimulation test is repeated to confirm adequate control. Dose titration for trilostane is guided by the combination of clinical signs and the post-ACTH cortisol value. The target range depends on the reference used, but most published protocols aim for a post-ACTH cortisol between 2 and 6 micrograms per deciliter. Values below this range raise concern for overtreatment, while values above it with persistent clinical signs support a dose increase. The dose adjustment step is typically 10 to 20 percent of the current dose, and the new dose is reassessed after a defined interval, usually 10 to 14 days. ## Monitoring Parameters and Interpretation The ACTH stimulation test is the central monitoring tool for both drugs. For trilostane, the test is performed 4 to 6 hours after the morning dose, because the drug's effect peaks during this window. For mitotane, the test is performed without regard to dosing time, since the drug's effect is cumulative instead of peak-dependent. The same assay and reference intervals apply to both drugs, which simplifies interpretation. Clinical monitoring is equally important and should not be deferred in favor of laboratory values. Polydipsia and polyuria typically resolve within the first 1 to 2 weeks of effective therapy. Skin changes, hair regrowth, and resolution of potbelly take 3 to 6 months. Owners should be asked specifically about appetite, water intake, urine output, vomiting, diarrhea, and energy level at every recheck. A dog that was polyuric and becomes normally hydrated but then develops lethargy and poor appetite may be overtreated even if the ACTH stimulation result is within the target range. | Monitoring Parameter | What It Detects | Action Threshold | |---|---|---| | Post-ACTH cortisol | Adequacy of blockade or lysis | Below target: reduce dose, above target with signs: increase dose | | Pre-dose cortisol (trilostane) | Basal secretory capacity | Very low values suggest overtreatment | | Sodium and potassium | Mineralocorticoid deficiency | Hyponatremia or hyperkalemia: stop drug, evaluate for hypoadrenocorticism | | Body weight | Fluid status, muscle mass | Weight gain with lethargy suggests overtreatment | | Owner-reported water intake | Early response marker | Failure to improve by 2 weeks: reassess diagnosis or dose | | Liver enzymes | Concurrent disease or drug effect | Persistent elevation: investigate independently | ## Adverse Effects and Complication Management Gastrointestinal signs are the most common adverse effects for both drugs. Mild vomiting or diarrhea in the first days of therapy may be transient, but persistent signs warrant drug withdrawal and re-evaluation. For trilostane, signs typically resolve within 24 to 48 hours of stopping the drug, and therapy can be restarted at a lower dose once the dog is stable. For mitotane, gastrointestinal signs during induction may indicate rapid adrenocortical destruction and require immediate ACTH stimulation testing. Iatrogenic hypoadrenocorticism is the most serious complication. It presents with lethargy, weakness, vomiting, diarrhea, collapse, and laboratory findings of hyponatremia, hyperkalemia, or both. Treatment requires stopping the offending drug, providing fluid therapy, and administering glucocorticoid and mineralocorticoid replacement as needed. Dogs that recover from trilostane-associated hypoadrenocorticism may be restarted at a lower dose after electrolyte and cortisol status normalize. Dogs with mitotane-induced hypoadrenocorticism may require permanent replacement therapy. Neurologic signs in a dog with PDH should prompt evaluation for a pituitary macroadenoma. Worsening lethargy, behavioral change, or visual deficits in a treated dog are not explained by cortisol excess alone and require imaging. The [ACVIM consensus statement on pulmonary hypertension](https://pubmed.ncbi.nlm.nih.gov/32065428/) is not directly relevant to this decision, but it illustrates the value of structured consensus guidance for complex endocrine and cardiovascular interactions. For broader reference on endocrine disease management, the [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides species-specific summaries of drug protocols and monitoring recommendations. ## Monitoring Schedules and Recheck Intervals The first recheck for trilostane occurs 10 to 14 days after starting therapy or after any dose change. The ACTH stimulation test is performed, clinical signs are reviewed, and electrolytes are measured. Once the target cortisol is achieved and clinical signs are improving, the next recheck occurs at 30 days, then at 3 months, and then every 3 to 6 months for the life of the dog. Every recheck includes a physical examination, body weight, owner questionnaire, and ACTH stimulation test. Electrolytes are measured at each recheck during the first 3 months and then at least twice yearly. Mitotane requires more intensive monitoring during induction. The ACTH stimulation test is performed every 5 to 7 days until the induction endpoint is reached. Once maintenance begins, the test is repeated at 30 days, then at 3 months, and then every 3 to 6 months. The same clinical parameters are assessed at each visit. Dogs that are well controlled on a stable dose for more than a year may be monitored at 6-month intervals, but any change in clinical signs warrants an earlier recheck. A dog that relapses after months of good control should be evaluated for progression of the underlying tumor, particularly if the dog has PDH. Imaging of the pituitary or adrenal glands may be indicated if clinical signs change despite stable cortisol values. ## Documentation and Client Communication The medical record should document the drug, dose, formulation, administration time, and the date of every dose change. Each recheck should record the ACTH stimulation result, the time of the last drug dose relative to the test, electrolyte values, body weight, and a structured assessment of each clinical sign. This allows the clinician to distinguish inadequate control from overtreatment and to track trends over time. Client communication should emphasize that treatment is lifelong and that monitoring is mandatory, not optional. Owners should be told what signs to watch for, particularly vomiting, diarrhea, lethargy, and changes in water intake. They should be instructed to call before stopping or adjusting medication on their own. Written instructions for dose changes should be provided at every recheck, and the owner should be asked to confirm their understanding of the new dose and schedule. The choice of monitoring frequency may need to be adapted to the practice setting. A general practice with limited ability to run ACTH stimulation tests in-house may schedule rechecks on specific days when samples are shipped to a reference laboratory. A referral practice may offer same-day testing. Both approaches are acceptable as long as the interval between dose changes and rechecks is consistent with published protocols. ## Recognized Complications and Early Detection Medical therapy for canine hyperadrenocorticism carries predictable failure modes that are best managed by anticipation instead of reaction. Hypoadrenocorticism is the most serious complication of both trilostane and mitotane therapy. Early detection depends on owner vigilance for lethargy, vomiting, diarrhea, inappetence, or collapse, combined with scheduled biochemical monitoring. A dog that was previously stable and becomes dull or anorectic should be assumed to have cortisol depletion until proven otherwise, and treatment should be withheld pending assessment. Trilostane overdose produces a syndrome that can be indistinguishable from naturally occurring hypoadrenocorticism. The discriminating feature is timing: clinical signs typically appear within days of a dose increase or a change in formulation. Electrolyte disturbances, particularly hyperkalemia and hyponatraemia, may lag behind clinical signs, so a dog with normal electrolytes can still be significantly hypocortisolaemic. The reverse is also true, a dog with classic electrolyte changes but minimal clinical signs requires immediate dose reduction. Mitotane carries additional risks related to its cytotoxic mechanism. During the induction phase, signs of cortisol withdrawal, including weakness, anorexia, and vomiting, can occur as the zona fasciculata and zona reticularis are destroyed. Permanent hypoadrenocorticism is an accepted outcome in a proportion of dogs and is not necessarily a treatment failure if it is recognized and managed. The greater concern is inadvertent destruction of the zona glomerulosa, which produces mineralocorticoid deficiency and requires lifelong fludrocortisone or desoxycorticosterone pivalate support. Hepatic enzyme induction is expected with both drugs and does not indicate hepatotoxicity. However, a dog that develops jaundice, pigmenturia, or elevated bilirubin requires investigation for idiosyncratic drug hepatopathy. Pancreatitis has been reported in association with mitotane, particularly in dogs with pre-existing gastrointestinal disease, and should be considered when vomiting is the dominant clinical sign. | Observation | Likely cause | Discriminating check | |---|---|---| | Lethargy, anorexia within days of dose change | Cortisol depletion | Pre-dose cortisol, electrolytes | | Vomiting with normal pre-dose cortisol | Gastrointestinal intolerance or pancreatitis | Abdominal ultrasound, pancreatic lipase | | Polyuria and polydipsia persist despite adequate cortisol suppression | Concurrent disease, incomplete suppression, or diabetes mellitus | Urinalysis, glucose, repeat ACTH stimulation test | | Alopecia and skin changes fail to improve after 6 months | Inadequate duration, concurrent hypothyroidism, or wrong diagnosis | Thyroid panel, repeat baseline cortisol | | Sudden collapse with bradycardia | Hyperkalemia from mineralocorticoid deficiency | Electrolytes, ECG | ## Common Errors and Corrective Action The most frequent error in trilostane monitoring is sampling at the wrong time relative to medication administration. The ACTH stimulation test should be performed four to six hours after the morning trilostane dose, when cortisol suppression is maximal. Sampling before dosing underestimates the degree of suppression and can lead to inappropriate dose escalation. Conversely, sampling too late after dosing overestimates suppression and risks dose reduction that leaves the dog poorly controlled. A second common error is adjusting the dose on the basis of a single clinical sign. Polyuria and polydipsia resolve early in treatment, often within the first two weeks, while dermatologic changes take three to six months. A dog with persistent polydipsia but adequate cortisol suppression should be evaluated for diabetes mellitus or urinary tract infection instead of subjected to further dose increases. Conversely, a dog with normal drinking but persistent muscle weakness may still be underdosed, since weakness is a later sign of control. Less experienced clinicians frequently misinterpret the pre-dose cortisol value in isolation. The pre-dose sample provides useful information about trough suppression, but it does not replace the ACTH stimulation test for dose decisions. A low pre-dose cortisol with an adequate post-ACTH response indicates good 24-hour control, while a low pre-dose cortisol with a blunted post-ACTH response indicates excessive suppression. Mitotane errors often involve the maintenance phase. Owners may discontinue maintenance dosing once clinical signs improve, leading to relapse within weeks. The maintenance schedule must be framed as lifelong, and recheck visits should verify that the owner is administering the drug as prescribed. Another error is using the same monitoring protocol for both drugs without adjustment for their different pharmacodynamics. ## Limitations of the Evidence and Areas of Expert Disagreement The comparative evidence base for trilostane versus mitotane is limited by the absence of large, prospective, randomised trials with long-term follow-up. Most published data derive from retrospective cohorts and referral populations, which may not reflect general practice outcomes. Expert opinion differs on several points, including the target post-ACTH cortisol concentration for trilostane, with some authorities accepting a range that others consider too broad, and the role of routine electrolyte monitoring in asymptomatic dogs on stable trilostane doses. There is ongoing debate about whether mitotane should be reserved for dogs that fail trilostane or whether it remains a first-line option in specific circumstances, such as pituitary-dependent disease with neurologic signs or when cost is a limiting factor. The ACVIM consensus process has not produced a dedicated hyperadrenocorticism statement in recent years, and clinicians should recognize that some recommendations rest on tradition instead of controlled data. The [ACVIM consensus statements](https://www.acvim.org/Animal-Owners/Animal-Education/Consensus-Statements) page provides a useful index of available guidance, but practitioners should check publication dates and weigh older recommendations accordingly. ## Referral, Consultation, and Reporting Referral to an internal medicine specialist is warranted when a dog fails to respond to two or more dose adjustments, when trilostane and mitotane are both contraindicated, or when the diagnosis is uncertain after initial treatment. Dogs with neurologic signs, including stupor, circling, or visual deficits, require urgent referral for imaging and consideration of radiation therapy or hypophysectomy. A dog that develops suspected hypoadrenocorticism and is unstable despite fluid therapy and glucocorticoid supplementation should be hospitalized and managed with intensive monitoring. Laboratory involvement is appropriate when point-of-care cortisol assays give results that conflict with the clinical picture. Commercial reference laboratories can provide confirmatory testing and, in some cases, assay-specific interpretive guidance. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) offers a general pharmacology reference for drug interactions and adverse effect profiles that may be useful when polypharmacy complicates management. Regulatory reporting is rarely required for hyperadrenocorticism therapy, but adverse drug event reporting to the manufacturer or the relevant national pharmacovigilance authority is appropriate for unexpected reactions, particularly suspected idiosyncratic hepatotoxicity or suspected product defects. The [AVMA practice resources](https://www.avma.org/resources-tools) provide guidance on adverse event reporting expectations in the United States, while international practitioners should consult their national veterinary board or the [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) for applicable requirements. ## Frequently Asked Questions ### How do I manage trilostane monitoring when the ACTH stimulation test is not available? When ACTH stimulation testing is unavailable, the resting cortisol concentration offers a practical alternative. A resting cortisol below the reference interval suggests adequate blockade, while a value well above the reference range indicates underdosing. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) describes resting cortisol measurement as a useful screening tool during treatment. Clinical response remains the primary guide. Recheck electrolytes, renal parameters, and appetite at each visit. If resting cortisol is equivocal, consider referral to a facility with ACTH testing capability. Document the monitoring limitation clearly in the record and inform the owner that biochemical confirmation of blockade is less precise with this approach. ### What monitoring adaptations are needed for dogs with concurrent disease? Dogs with diabetes mellitus, cardiac disease, or chronic kidney disease require closer observation during induction. Glucocorticoid excess worsens insulin resistance, so insulin requirements often fall as cortisol production is blocked. Recheck glucose curves within two weeks of each dose change. Cardiac patients may tolerate the volume shifts associated with mineralocorticoid effects poorly, so electrolyte assessment is essential. The [ACVIM consensus statements](https://www.acvim.org/Animal-Owners/Animal-Education/Consensus-Statements) emphasize individualised treatment plans for complex endocrine patients. Reduce starting doses in frail patients and extend titration intervals. Prioritize owner-reported quality of life over laboratory perfection when comorbidities limit therapeutic options. ### How should I respond when a dog develops suspected hypoadrenocorticism during treatment? Suspect iatrogenic hypoadrenocorticism when a treated dog shows lethargy, vomiting, diarrhea, or collapse. Withhold the drug immediately and assess electrolytes, glucose, and cortisol. Confirmatory testing can follow once the patient is stabilized. Most dogs recover within days of drug withdrawal, but some require temporary glucocorticoid and mineralocorticoid support. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) outlines the clinical features of hypoadrenocorticism that overlap with overtreatment. After recovery, restart at a lower dose and recheck sooner than the standard interval. Counsel owners to recognize these signs early, as prompt drug withdrawal can prevent hospitalization. ### What are the cost differences between trilostane and mitotane over a treatment year? Trilostane generally carries higher monthly medication costs but requires fewer monitoring visits after stabilization. Mitotane is less expensive per dose but demands more frequent ACTH stimulation tests during induction and maintenance, and the loading phase requires hospitalization or very close outpatient supervision. Total annual costs often converge, but the payment pattern differs. Owners with limited cash flow may prefer mitotane's lower monthly outlay, while those prioritizing convenience favour trilostane. Discuss both cost structures openly before initiating therapy. The [AVMA practice resources](https://www.avma.org/resources-tools) provide general guidance on discussing financial planning with clients. Document the cost discussion and the owner's informed choice in the medical record. ### How do I explain treatment monitoring to an owner who cannot afford frequent rechecks? Be transparent about the risks of unmonitored therapy. Explain that dose requirements change over time and that both underdosing and overdosing cause harm. Offer a reduced monitoring schedule with explicit caveats: resting cortisol instead of ACTH stimulation, longer intervals between rechecks, and reliance on clinical signs. Ask the owner to keep a simple daily log of appetite, water intake, and energy level. The [ACVIM consensus statements](https://www.acvim.org/Animal-Owners/Animal-Education/Consensus-Statements) support adapting monitoring to individual circumstances. If the owner declines recommended monitoring, document the discussion and the agreed plan. Referral to a low-cost clinic or teaching hospital may reduce costs without sacrificing safety. ### What records should I maintain for a patient on long-term glucocorticoid blockade? Maintain a chronological treatment log that includes drug, dose, body weight, date of each change, and the indication for that change. Record every monitoring result with the test type and the interval since the last dose. Note clinical signs at each visit, owner-reported observations, and any adverse events with their outcome. The [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) emphasize the importance of complete medical records for continuity of care. Include the owner's informed consent for the chosen drug and monitoring plan. This record supports dose decisions years later and protects against liability if complications arise. ## Related Clinical & Scientific Guides * [Feline Hepatic Lipidosis: Nutritional and Medical Management](/knowledge/veterinary-medicine/clinical-internal-medicine/feline-hepatic-lipidosis-nutritional-medical-management) * [Canine Respiratory Infection: Diagnostic Approach and Treatment](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-respiratory-infection-diagnostic-approach-treatment) * [Canine Respiratory Virus: Diagnostic and Management Considerations](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-respiratory-virus-diagnostic-management-considerations) ## References and Further Reading - [ACVIM consensus statement guidelines for the diagnosis, classification, treatment, and monitoring of pulmonary hypertension in dogs.](https://pubmed.ncbi.nlm.nih.gov/32065428/). 2020. - [ISFM Consensus Guidelines on the Diagnosis and Management of Hypertension in Cats.](https://pubmed.ncbi.nlm.nih.gov/28245741/). 2017. - [ACVIM Consensus Statements](https://www.acvim.org/Animal-Owners/Animal-Education/Consensus-Statements). Journal of Veterinary Internal Medicine. - [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual. - [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association. - [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). WOAH. ## Related Articles - [Canine Chronic Hepatitis: Diagnosis and Treatment Monitoring](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-chronic-hepatitis-diagnosis-treatment-monitoring) - [Canine Hypoadrenocorticism: Diagnostic and Therapeutic Monitoring](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-hypoadrenocorticism-diagnostic-therapeutic-monitoring) - [Canine Epilepsy: Antiepileptic Drug Selection and Monitoring](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-epilepsy-antiepileptic-drug-selection-monitoring) - [Canine Acute Pancreatitis: Severity Assessment and Treatment](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-acute-pancreatitis-severity-assessment-treatment) - [Canine Respiratory Infection: Diagnostic Approach and Treatment](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-respiratory-infection-diagnostic-approach-treatment) > This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.