CHAPTER 26 HYPERADRENOCORTICISM, CANINE 401
ADH:
Administer mitotane at highest tolerated dosage beginning with 50 mg/kg
q24h as a loading dose
Administer prednisone at 0.2 mg/kg PO q24h during induction
Monitoring similar to PDH.
Trilostane:
Inactive steroid analog that competitively inhibits 3-beta-hydroxysteroid dehy-
drogenase
Prevents production of cortisol and aldosterone
Competitive inhibition is reversible and dose dependent
Side effects include lethargy, anorexia, vomiting, dehydration, weakness, and
hyponatremia/hyperkalemia
Irreversible acute adrenal necrosis may occur
Anecdotal reports of acute death shortly after initiating therapy
Give with food for maximum absorption
Do not use in pregnant or nursing bitches, animals intended for breeding, or
patients with renal or hepatic disease or evidence of anemia
Trilostane may block estrogen receptors, thus causing increased levels of adrenal
sex hormones. Do not use in breeding animals
Dosage guidelines: 3–6 mg/kg PO q24h; many dogs are controlled with a lower
dose of 1.3–3 mg/kg PO BID
Dosage based on body weight: large dogs (>30 kg) may require a lower dose
compared to small dogs (<15 kg):
<3 kg body weight=starting dose of 10 mg q24h
>3kgand<10 kg=starting dose of 30 mg q24h
>10 kg and<20 kg=starting dose of 60 mg q24h
>20 kg and<40 kg=starting dose of 120 mg q24h
>40 kg=starting dose of 180 mg q24h
Doses can be given once daily or divided twice daily; some dogs may require
three times daily administration
Dose is adjusted based on ACTH stimulation test cortisol levels
Most patients show clinical improvement within 7 days
Repeat ACTH stimulation test 1–2 weeks after starting medication (4–6 hours
post pill; some endocrinologists recommend 2–4 hours post pill)
Monitor levels by ACTH stimulation test at 1 month, 2 months, 3 months, 6
months post initiation of medication and then every 3–6 months if the levels are
stable
Basal serum cortisol concentrations or post-ACTH stimulation test cortisol levels
may be used for monitoring response
Ideal target range for basal serum cortisol: 1.3–2.9μg/dL (35–80 nmol/L) or less
than or equal to 50% of the pretreatment baseline cortisol concentration
Ideal target range for cortisol concentrations post ACTH stimulation: 1.45–
5.4μg/dL (40–150 nmol/L)