Trilostane Dose versus Body Weight in the Treatment of Naturally Occurring Pituitary-Dependent Hyperadrenocorticism in Dogs

Background: Trilostane is commonly used in the treatment of dogs with naturally occurring pituitary-dependent hyperadrenocorticism (PDH). Dose recommendations have varied from the manufacturer and the literature. Hypothesis: As body weight increases, dose/kg or dosage/day of trilostane required to control the clinical signs of PDH decreases. Animals: 70 dogs with naturally occurring hyperadrenocorticism. Methods: Retrospective study. Each dog must have been treated for at least 6 months and should have shown a "good response" to trilostane, as determined by owners. Statistical comparisons of dose and dosage were made after the dogs were separated into groups weighing <15 or >15 kg; groups weighing ≤10, 10.1-20, 20.1-30, and ≥30 kg; and then groups based on body surface area versus dose/kg and total amount of trilostane required to control the condition. Results: There was no significant difference in trilostane dose in mg/kg of body weight or in the total amount of trilostane required daily to control clinical signs, except when the dose for dogs weighing >30 kg was compared with that for the other groups. However, despite lack of statistical significance when comparing groups, there was a significant trend using polynomial regression analysis, suggesting that as body weight increases, the amount of trilostane (mg/kg/dose as well as mg/kg/daily dosage) required to control clinical signs decreases. Conclusions and Clinical Importance: Dogs weighing >30 kg, and possibly those weighing >15 kg, might require smaller amounts of trilostane per dose or per day than those weighing less, to control PDH-associated clinical signs.