By Rania Gollakner, BS, DVM, MPH

What is mitotane?

Mitotane, also known as o,p’-DDD (brand names: Lysodren®, Lisodren®) is an anticancer medication that is toxic to the adrenal gland cells and is used to treat hyperadrenocorticism (Cushing’s disease) or adrenal gland carcinoma.

Its use in dogs and ferrets to treat adrenal disorders is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is mitotane given?

Mitotane is given by mouth in the form of a tablet. It should be given with food, preferably one high in fat. Your veterinarian may provide you with a high fat pet food, or you can give the medication with a little corn oil, butter, or cheese. Wear gloves when administering this medication and do not allow the medication to come into contact with your skin, eyes, or mouth. Wear gloves when handling your pet’s urine, feces, or vomit, as the drug may be present.

Pregnant women should not handle this medication.

This medication should take effect within 1 to 2 days; however, effects are not always visibly obvious and therefore laboratory tests may be needed to evaluate this medication’s effectiveness. Improvement in clinical signs such as improved eating and drinking habits and a decrease in urination should occur within the first 1-2 weeks.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effects include vomiting and diarrhea. Other side effects include lack of appetite, neurologic signs, lethargy, incoordination, weakness, or yellowing of the skin, gums, or whites of the eyes. Any of these side effects may be serious and indicate the need for emergency glucocorticoid supplementation, so please contact your veterinarian for guidance if any side effects occur.

This long-acting medication lasts for at least 4 – 6 weeks and may last longer in pets with kidney or liver disease.

Are there any risk factors for this medication?

Mitotane should not be used in  pets that are allergic to it, that are sick, weak, or frail, or in pets that are pregnant or lactating. It should be used cautiously in pets with diabetes mellitus or kidney or liver disease. Pets that have been injured or are undergoing a stressful event like surgery may be at risk for developing Addison’s disease; during these times, your pet may need to be supplemented with a corticosteroid.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with mitotane: central nervous system (CNS) depressant drugs, fentanyl, insulin, midazolam, phenobarbital, selegiline, spironolactone, or warfarin.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Your veterinarian will monitor your pet to be sure that the medication is working by monitoring clinical effects and performing regular ACTH response tests. Your veterinarian may also monitor liver and kidney values, blood cell counts, blood sugar levels, and blood electrolytes. Regular monitoring at home for adverse/serious side effects is very important in addition to regular monitoring by your veterinarian.

How do I store mitotane?

Store this medication at room temperature between 59°F and 86°F (15°C and 30°C) and protect from light and moisture.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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