-----Pituitary Cushing's Syndrome
River Road Veterinary Clinic
Box 309
Norwich, Vermont 05055
Phone: 802-649-3877 Fax: 802-649-1345
email: RRVC@Valley.net.com
www.rrvetclinic.com
Dr. Christine Pinello - Dr. JoAnne Giel - Dr. Kathy Ling Newcomb
o,p' -DDD Treatment of Pituitary Cushing's Syndrome
Article written by: Edward C Feldman
Hyperadrenocorticism (Cushing's Syndrome) refers to a clinical condition
that results from having excess cortisone in the system. A minority
of dogs with this disease have a tumor in one of the two glands that
produce cortisone (the adrenal glands). Your dog, like more than 80
per cent of dogs with the naturally acquired form of this disease, has
a small tumor at the base of the brain in an area called the pituitary
gland. The pituitary gland controls adrenal function. A tumor in the
pituitary can cause excess demand for cortisone production, which, in
turn, causes excess cortisone throughout the body and results in symptoms
recognized by owners ("pituitary-dependant" Cushing's syndrome).
The most common symptoms of Cushing's syndrome in dogs include excess
urination and water consumption, a voracious appetite, hair loss, muscle
weakness, a "potbellied" appearance, panting, thin skin, and
lethargy. Virtually all dogs with Cushing's syndrome have at least one
or two of these signs, but it would be uncommon for a dog to have all
of these symptoms. By evaluation a variety of test results, your veterinarian
has diagnosed your dog as having a pituitary- dependant Cushing's. Now
treatment with o,p' -DDD has been recommended.
During World War II, scientists did research on the insecticide DDT
in an attempt to create an extremely toxic form. One of the forms of
DDT created was o,p' -DDD (Lysodren; mitotane), a chemical that can
destroy the cortisone-producing cells of adrenal glands in dogs. The
drug has been used successfully in thousands of dogs with Cushing's,
but you must remember that it is a "poison" and that it must
be used appropriately. The protocol we use in treating dogs with this
drug is straightforward. A day or two before starting treatment, begin
feeding your dog one third of its normal food allotment twice daily
(each 24 hours it should receive a total of two thirds of the normal
amount). This should make your dog even more hungry, but this is just
for a brief time (we do not recommend use of this drug in dogs with
a poor appetite). After 1 to 2 days of reduced feeding, begin giving
the o,p' -DDD at a dose of 25 mg/kg of body weight twice daily (a dog
weighing 22 pounds would receive one half tablet twice daily; the tablets
contain 500mg). The drug should be given immediately after
the dog eats. So, feed the dog, note how long it takes to finish the
meal, and then give the medication (the drug is absorbed best from a
stomach containing food).
The key to treating these dogs is watching them eat and knowing when
to stop giving the o,p'-DDD. As long as their appetite is ravenous,
give the medication. As soon as you see any reduction in appetite,
STOP giving the drug. Reduction in appetite may be noted as the
dog taking longer to finish the meal; eating half of the food, wandering
away for a drink, and then finishing; or simply looking up at the owner
once or twice before finishing. In other words, we do not want the dog
to stop eating entirely, we wish to see a "reduction" in appetite
as a signal to stop the medication. Other signals include reduced water
intake, vomiting, diarrhea, and listlessness, but appetite reduction
usually precedes these more worrisome symptoms. Most dogs respond to
this drug in 5 to 9 days, a few respond in as little as 1 to 3 days,
and some may take longer than 14 days.
No dog should receive o,p' -DDD for more than 8 days without being tested
for the effect of the drug. The test is done by you veterinarian and
takes 1 to 2 hours. We typically start the treatment on a Sunday and
plan the recheck test 8 days later (Monday), and more than 85 per cent
of owners have stopped medication on the Thursday, Friday, Saturday,
or Sunday before the test is preformed on Monday. When the o,p' -DDD
has been demonstrated to have had an effect, the dog can be returned
to a normal amount of food. The dog will continue to receive o,p' -DDD
for the rest of its life. The initial maintenance dose is usually approximately
50 mg/kg per week (a 22 pound dog would receive one-half tablet twice
weekly). That dose is likely to be increased or decreased on the basis
of testing performed 1 month after maintenance treatment has been started
and testing preformed every 2 to 4 months thereafter. The average dog
(11.5 years old when the syndrome is diagnosed) treated in this manner
lives about 30 months (some live a few weeks and some 6 to 10 years).
The dogs with the longest survival have the owners who are committed
to helping their pet, diligent veterinarians, and luck. Close observation
and frequent veterinary rechecks can only help in the long-term management
of these dogs.