Efficacy of low- and high-dose trilostane treatment in dogs (< 5 kg) with pituitary-dependent hyperadrenocorticism.

Trilostane is commonly used to treat pituitary-dependent hyperadrenocorticism (PDH) in dogs. There are differing opinions regarding the dose and frequency of trilostane administration in dogs with PDH. To compare the efficacy of 2 trilostane protocols in the treatment of dogs with PDH. Sixteen client-owned dogs with PDH and a body weight <5 kg. Prospective observational study. Group A (n=9; low-dose treatment group) received 0.78 ± 0.26 mg of trilostane/kg PO every 12 h and group B (n = 7; high-dose treatment group) 30 mg of trilostane/dog PO every 24 h. All of the dogs were reassessed at 2, 4, 8, 12, 16, and 24 weeks after the initiation of treatment. An improvement in both ACTH-stimulated serum cortisol concentrations and clinical signs occurred more slowly in group A than in group B; however, after 20 weeks of treatment, 2/7 dog in group B had clinical signs and abnormal laboratory findings consistent with hypoadrenocorticism. At 24 weeks, an improvement in the clinical findings of all of the dogs in both groups was detected. In dogs with PDH, twice-daily administration of low-dose trilostane is an effective approach to the management of PDH. In addition, our results suggest fewer potential adverse effects if trilostane is administered twice daily in the lower dose.