o,p' -DDD Treatment of Pituitary Cushing's Syndrome

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. The above is general veterinary information. Do not begin any course of treatment without consulting your regular veterinarian. All animals should be examined at least once every 12 months.