This disease hits close to home for me since my own horse Prophecy was diagnosed with it at the age of 9 using the morning and night cortisol levels testing method. I have had him on pergolide since that time, which was about four years ago. His symptoms at the time of diagnosis were for the most part very mild and very subtle. He had many episodes of "ain’t doing right,” laziness in the arena and a mild case of laminitis. His owner at that time, having had a dog with Cushing’s disease, asked me to test him. I’m happy to report that he is symptom free today. However, to be on the safe side, I’m starting Prophecy on higher dose vitamin E supplements and will test him using low-dose dexamethasone suppression combined with TRH stimulation. If he tests positive with that method, I will seriously consider trilostane for him.
Close monitoring in the beginning and after any dose adjustment is essential. Discontinue trilostane and contact your veterinarian immediately if signs of intolerance are seen. Common side effects include mild lethargy, vomiting, diarrhea, and appetite reduction, especially in the beginning. Most reactions are minor and are reversed by decreasing the dose or discontinuing therapy, but serious or fatal Addisonian reactions are also possible. Side effects should be followed by electrolyte (sodium and potassium) and ACTH testing. Once symptoms resolve, the drug can be restarted at 50 percent dose reduction.
The drug's most common side effects are poor or reduced appetite, vomiting, lack of energy, diarrhea, and weakness. Occasionally, more serious side effects, including bloody diarrhea, collapse, severe sodium/potassium imbalance, and destruction of the adrenal gland may occur, and may result in death. In 2014, with input from CVM, the manufacturer updated the information about patient monitoring and side effects on the package insert. Although not proven to be caused by Vetoryl, some additional side effects reported to CVM and now included on the package insert are adrenal insufficiency, shaking, elevated liver enzymes and elevated kidney tests.