Canine Cushing's Case Files: The ins and outs of detection and treatment—Case file: Boca (Sponsored by Dechra Veterinary Products)
Case file: BOCA, an 8-year-old spayed female Shih Tzu weighing 14 lb (6.4 kg)
Patient history and initial diagnostic workup
A serum chemistry profile showed elevated alkaline phosphatase (ALP), alanine aminotransferase (ALT), and gamma glutamyl transferase (GGT) activities. Boca's urine specific gravity was 1.014.
An abdominal ultrasonographic examination revealed a biliary mucocele and hepatomegaly. Bocca was subsequently referred to a veterinary surgeon, and her gallbladder was removed.
Adrenal function test results
I discussed two medical treatment options with the owners—mitotane and VETORYL® Capsules (trilostane). I advised the owners that mitotane was not approved for use in dogs and that I had experience with using mitotane to treat canine hyperadrenocorticism but not with VETORYL Capsules. The owners elected to treat Boca with mitotane in an extra-label fashion.
After 11 days of once daily treatment with an induction dose of mitotane, Boca's baseline cortisol concentration was 1.0 µg/dl and her one-hour post-ACTH cortisol concentration was 1.1 µg/dl. Based on these results, the induction dose of mitotane was discontinued and a twice-weekly maintenance dose of mitotane was started. A low dose of prednisone was also given on the mitotane treatment days.
After one month on the maintenance dose of mitotane with prednisone, Boca's owners reported that she had diarrhea and lethargy on the days she received mitotane. Boca's baseline cortisol concentration was 2.8 µg/dl and her one-hour post-ACTH cortisol concentration was 5.2 µg/dl. Her ALP, ALT, and GGT activities were still elevated. Boca's diarrhea was managed with supportive care and the prednisone and mitotane were continued at the same dosages.
After one year of treatment with mitotane and prednisone, Boca presented for evaluation of vomiting and diarrhea with tenesmus. Her ALP, ALT, and GGT activities were still elevated. An ACTH stimulation test showed a baseline cortisol concentration of 6.8 µg/dl and a one-hour post-ACTH cortisol concentration of 24.5 µg/dl.
Because Boca would again need to receive mitotane at an induction dose and she had not tolerated mitotane well to date, I recommended discontinuing treatment with mitotane and prednisone and starting treatment with VETORYL® Capsules (trilostane) one month later.