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

Hyperadrenocorticism (Cushing's Syndrome) refers to a clinicalcondition that results from having excess cortisone in thesystem. A minority of dogs with this disease have a tumor in oneof the two glands that produce cortisone (the adrenal glands).Your dog, like more than 80 per cent of dogs with the naturallyacquired form of this disease, has a small tumor at the base ofthe brain in an area called the pituitary gland. The pituitarygland controls adrenal function. A tumor in the pituitary cancause excess demand for cortisone production, which, in turn,causes excess cortisone throughout the body and results insymptoms recognized by owners ("pituitary-dependant" Cushing'ssyndrome). The most common symptoms of Cushing's syndrome indogs include excess urination and water consumption, a voraciousappetite, hair loss, muscle weakness, a "potbellied" appearance,panting, thin skin, and lethargy. Virtually all dogs with Cushing's syndrome have at least one ortwo of these signs, but it would be uncommon for a dog to haveall 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 beenrecommended.During World War II, scientists did research on the insecticideDDT in an attempt to create an extremely toxic form. One of theforms of DDT created was o,p' -DDD (Lysodren; mitotane), achemical that can destroy the cortisone-producing cells ofadrenal glands in dogs. The drug has been used successfully inthousands of dogs with Cushing's, but you must remember that itis a "poison" and that it must be used appropriately. Theprotocol we use in treating dogs with this drug isstraightforward. A day or two before starting treatment, begin feeding your dogone third of its normal food allotment twice daily (each 24hours it should receive a total of two thirds of the normalamount). This should make your dog even more hungry, but this isjust for a brief time (we do not recommend use of this drug indogs with a poor appetite). After 1 to 2 days of reducedfeeding, begin giving the o,p' -DDD at a dose of 25 mg/kg ofbody weight twice daily (a dog weighing 22 pounds would receiveone half tablet twice daily; the tablets contain 500mg). Thedrug should be given immediately after the dog eats. So, feedthe dog, note how long it takes to finish the meal, and thengive the medication (the drug is absorbed best from a stomachcontaining food).The key to treating these dogs is watching them eat and knowingwhen to stop giving the o,p'-DDD. As long as their appetite isravenous, give the medication. As soon as you see any reductionin appetite, STOP giving the drug. Reduction in appetite may benoted as the dog taking longer to finish the meal; eating halfof the food, wandering away for a drink, and then finishing; orsimply 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 themedication. Other signals include reduced water intake,vomiting, diarrhea, and listlessness, but appetite reductionusually precedes these more worrisome symptoms. Most dogsrespond to this drug in 5 to 9 days, a few respond in as littleas 1 to 3 days, and some may take longer than 14 days.No dog should receive o,p' -DDD for more than 8 days withoutbeing tested for the effect of the drug. The test is done by youveterinarian and takes 1 to 2 hours. We typically start thetreatment on a Sunday and plan the recheck test 8 days later(Monday), and more than 85 per cent of owners have stoppedmedication on the Thursday, Friday, Saturday, or Sunday beforethe test is preformed on Monday. When the o,p' -DDD has beendemonstrated to have had an effect, the dog can be returned to anormal 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/kgper week (a 22 pound dog would receive one-half tablet twiceweekly). That dose is likely to be increased or decreased on thebasis of testing performed 1 month after maintenance treatmenthas been started and testing preformed every 2 to 4 monthsthereafter. The average dog (11.5 years old when the syndrome isdiagnosed) treated in this manner lives about 30 months (somelive a few weeks and some 6 to 10 years). The dogs with thelongest survival have the owners who are committed to helpingtheir pet, diligent veterinarians, and luck. Close observationand frequent veterinary rechecks can only help in the long-termmanagement of these dogs.The above is general veterinary information. Do not beginany course of treatment without consulting your regularveterinarian. All animals should be examined at least once every12 months.