Small Animal Dermatology, 3rd edition

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)