Mitotane in Dogs
Generic: Mitotane
Mitotane is a cytotoxic chemotherapy agent used primarily in the management of pituitary-dependent hyperadrenocorticism in dogs by selectively destroying the cortisol-producing cells of the adrenal cortex.
This medication is intended for dogs.
Overview
Mitotane is a derivative of the insecticide DDT and serves as a powerful adrenal-cortical suppressant used in veterinary medicine to manage canine hyperadrenocorticism (Cushing's disease). It is often considered a traditional treatment alternative to Trilostane, which functions as a competitive enzyme inhibitor rather than a cytotoxic agent. Clinical use involves a strictly monitored induction phase followed by a long-term maintenance phase, as the drug irreversibly damages the zona fasciculata and zona reticularis layers of the adrenal glands.
Because the action of Mitotane is so profound, it requires meticulous endocrine monitoring to prevent iatrogenic hypoadrenocorticism, or Addison's disease. Owners must be highly observant of their dog's appetite, energy levels, and water intake, as these serve as critical clinical indicators of the drug's efficacy. While newer agents like Trilostane are frequently used first, Mitotane remains an essential option, particularly for patients with adrenal-dependent Cushing's syndrome where surgical intervention may not be possible or desired.
Clinicians often manage secondary endocrine conditions alongside Cushing's disease, such as diabetes mellitus requiring Insulin or, in rarer cases where hypothyroidism co-occurs, Levothyroxine. Managing these concurrent diseases is complex, as the reduction of cortisol levels can alter insulin requirements and metabolic rates. Consequently, veterinary teams must carefully calibrate the hormonal environment of the patient throughout the entire treatment process.
Safety is paramount when handling Mitotane, as it is a potent cytotoxic medication. It is strongly advised that owners avoid crushing or splitting tablets and wear gloves during administration to prevent accidental ingestion or skin contact. The therapeutic window for Mitotane is quite narrow, and the clinical management is a lifelong commitment that demands a strong partnership between the primary veterinarian and the pet owner to ensure the animal remains stable and comfortable.
What It Treats
- Pituitary-Dependent Hyperadrenocorticism: Used to kill overactive cortisol-producing cells in the adrenal glands.
- Adrenal-Dependent Hyperadrenocorticism: Sometimes used for malignant adrenal tumors when surgical removal is not an option.
- Cushing's Syndrome clinical signs: Assists in reducing symptoms like excessive thirst (polydipsia), excessive urination (polyuria), and muscle wasting.
How It Works
Mitotane works through direct cytotoxic action on the adrenal cortex. Once ingested, it accumulates in the adrenal gland cells and undergoes metabolic conversion, which triggers the destruction of the mitochondrial enzymes necessary for cortisol synthesis. By targeting the zona fasciculata and zona reticularis, the medication causes atrophy of these specific layers, thereby permanently decreasing the adrenal gland's ability to produce cortisol in response to stimulation. Unlike reversible inhibitors, the damage caused by Mitotane is often permanent to the affected cell populations. The dosage is carefully calculated to reduce the adrenal function to a level where normal physiologic requirements are met without inducing total adrenal failure. This necessitates constant testing via ACTH stimulation tests to ensure the cortisol levels are suppressed sufficiently but remain within a safe, non-life-threatening range.
Dosage
Dosage is highly individualized and varies drastically between the induction phase and the maintenance phase. It is strictly determined by the dog's body weight and the results of periodic endocrine blood tests. Owners must follow their veterinarian's exact dosing schedule without deviation, as over-dosing can lead to irreversible and fatal adrenal destruction.
Administration
Mitotane is administered orally and should be given with a fatty meal. Providing the medication with food improves absorption and helps reduce the potential for gastrointestinal irritation. It is vital to handle the tablets carefully, utilizing gloves if possible, and ensuring the animal swallows the entire dose without spitting out fragments.
Storage
Store Mitotane at controlled room temperature, typically between 20°C and 25°C (68°F to 77°F). It should be kept in a tightly closed, child-resistant container, away from moisture, heat, and direct light, and stored well out of the reach of children and other household pets.
Contraindications
Mitotane is contraindicated in patients with known hypersensitivity to the drug or those with preexisting severe liver or kidney disease, as these organs are responsible for the drug's metabolism and excretion. It should also be avoided in pregnant or nursing dogs, as the cytotoxic nature of the drug may harm fetal development. Furthermore, if a patient has already been diagnosed with primary hypoadrenocorticism (Addison's disease), Mitotane must not be used, as it would worsen the deficiency. Extreme caution is exercised in patients who are dehydrated or suffering from other concurrent debilitating illnesses until the dog is medically stable enough to tolerate potential side effects.
Interactions
Mitotane is known to interact with various medications because it can induce hepatic microsomal enzymes, potentially accelerating the metabolism of other drugs. Concurrent use of other medications like [Insulin](/medications/insulin-caninsulin-vetsulin-in-dogs-and-cats) or [Levothyroxine](/medications/levothyroxine-in-dogs) may require significant dosage adjustments during treatment, as cortisol levels directly impact insulin requirements and metabolic rates. Additionally, drugs that affect liver enzyme pathways should be used with caution, and owners should provide a complete list of all supplements and medications to their veterinarian. Sudden changes in the patient's diet or lifestyle can also complicate the metabolic stability of the patient, and any new drugs should be vetted by a specialist to ensure no negative interference with the Mitotane therapy.
Side Effects
- Lethargy or severe weakness
- Decreased appetite or anorexia
- Vomiting and diarrhea
- Ataxia (loss of coordination)
- Iatrogenic hypoadrenocorticism (Addisonian crisis)
- Increased thirst and urination (temporary or as a sign of under-dosage)
- Neurological symptoms in rare cases
Sources & References
Frequently Asked Questions
This information is educational only and not a substitute for professional veterinary advice. Always consult a licensed veterinarian before starting or changing any medication.