Evaluation of treatment strategy for Mitotane intolerance in dogs with Cushing s syndrome

Objective: Cushing s syndrome, is the result of excessive production or administration of corticosteroids. Generally, Cushing’s syndrome usually seen in middle-aged to older dogs and certain breeds like Poodle and Terrier. The mechanism of Mitotane is through the destruction of the zonareticularis and zonafascicolata, but Mitotane usage may cause symptoms of drug intolerance in the patients. The aim of this study was to achieve an appropriate strategy to deal with intolerance of Mitotane.Materials methods: In this study, 7 dogs from Terrier, Poodle, Spitz and Dachshund breeds which Cushing’s Syndrome were confirmed in all of them via the diagnostic tests: ACTH Stimulation Test and low and high dose Dexamethasone suppression test, were all treated with Mitotane and Drug intolerance was created experimentally through high doses of 58 mg/kg and drug usage for over 12 days. After intolerance creation, patients initially treated with Prednisolone with a daily dose of 0.8 mg/kg and the dose was reduced to 0.2 mg/kg within a week. The daily dose of Mitotane was also divided into two equal parts and administration interval of 10 hours was considered in 5 of 7 cases as another part of the treatment method.Results Conclusion: The administration of Prednisolone significantly improved the clinical signs and intolerance symptoms in 6 of the cases. Dividing the daily dose of Mitotane has good efficacy in reducing the symptoms of weakness and ataxia in 5 patients but this method reduced the speed of recovery process of symptoms, like the amount of water intake and appetite. Using exogenous Glucocorticoids can mitigate a rapid fall in circulating Cortisol and also can prevent the resulting potential crisis from too little Cortisol. If there is no improvement in symptoms after administration of prednisone, dividing the daily dose of Mitotane is recommended