Cushing's Disease - Treatment Instructions with Mitotane for Dogs

By Malcolm Weir, DVM, MSc, MPH; Ernest Ward, DVM

Treatment with mitotane (brand name Lysodren®) involves an initiating phase and a maintenance phase. The initiating phase arrests the disease and restores the dog to a more normal state. Some of the clinical signs, especially increased food and water intake, should stop within the first 1-3 weeks. Other signs, such as a poor hair coat or a bloated abdomen, may take several weeks or months to correct. The maintenance phase represents the phase of long-term therapy. This phase lasts the rest of the dog's life.

You must continually monitor your dog's food and water intake. Both should return to a normal level. Water intake should be less than 1 ounce per pound (66 ml per kilogram) of body weight per day, but do not limit the water if your dog needs to drink more. Your dog should drink _______ ounces (_______ ml) per day if water intake has returned to normal. The amount of food should also be measured each day. At least two feedings per day are preferred.

Initiating Phase of treatment:

1) Give _______ Lysodren® tablet(s) one time per day beginning on _______ for _______ days or until one of the following occurs

a) Your dog's water intake drops to 1 oz per pound (66 ml per kilogram) per day, which is _______  per day.

b) Your dog's appetite returns to normal or it takes 15-30 minutes to eat when it would normally eat in much less time.

c) Your dog does not eat a regular meal.

d) Your dog vomits.

e) Your dog has diarrhea.

f) Your dog becomes unusually listless.

2) Return in _______ days or when one of the above occurs for another ACTH stimulation test. This test should be done early in the morning and will require your dog to be in the hospital for about 2-4 hours. If the test is still abnormal, the initiating phase will continue. If the test is normal, the maintenance phase will begin.


3) If loss of appetite, vomiting, diarrhea, or listlessness occurs, give _______   tablet(s) (_______ mg) of prednisone or _______________  twice daily for ________ days. DISCONTINUE THE LYSODREN® TABLETS. If vomiting prevents oral administration, your dog must be seen by a veterinarian for administration of proper medication by injection. When you begin this treatment, please call us for consultation and instructions.

Following the first ________  days of treatment with ________  tablet(s) twice daily, give ________  tablet(s) twice daily for ________  more days,

then ________ tablet(s) twice daily for ________ days,

then ________ tablet(s) once every other day for ________ week(s).

At the end of that time, make an appointment so we can assess the situation and give you further instructions on Lysodren® administration.

4) Report any other changes in your dog's behavior that are out of the ordinary. This disease, and this treatment, can result in several abnormal behaviors. However, your dog can also have other diseases that occur at the same time, but independently, of Cushing's disease. It is important that we differentiate between the two situations so that proper treatment can be taken.

5) Stay cautiously optimistic. This is a serious disease, but many dogs with Cushing's disease enjoy a greatly improved quality of life for many years.

Maintenance Phase of treatment:

Once regulated, your dog will take Lysodren® approximately once weekly, but your veterinarian will determine the best dosing schedule for your dog. An ACTH stimulation test will be necessary about every 3-4 months to be sure that regulation is satisfactory. At the appropriate time, the specifics of the maintenance phase will be explained.

Give ________ tablet(s) every ________ days.

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