CVC 2008 Highlights: Managing atypical and critical cases of primary hypoadrenocorticism in dogs - Veterinary Medicine
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CVC 2008 Highlights: Managing atypical and critical cases of primary hypoadrenocorticism in dogs
Two things you may not know about canine Addison's disease: A history of weight loss or hypoglycemia may precede the typical electrolyte abnormalities, and DOCP can be administered immediately in dogs that may be having an addisonian crisis.


VETERINARY MEDICINE


During that hour, start treating the dog's hypovolemia and hypotension with fluid resuscitation (0.9% sodium chloride solution at 60 to 80 ml/kg for the first one or two hours), administer a glucocorticoid in the form of a dexamethasone salt (1 mg/kg dexamethasone sodium phosphate given intravenously) rather than prednisone so it won't interfere with your ACTH stimulation test results, provide thermal support (e.g. forced-air warming with a Bair Hugger [Arizant Healthcare] or a warm-water- circulating blanket), and administer a mineralocorticoid, such as desoxycorticosterone pivalate (DOCP; Percorten-V—Novartis Animal Health) (1 mg/lb given intramuscularly), right away. Data show that giving DOCP daily to healthy dogs is not harmful,4 and there is no medical disadvantage to giving this drug during a potential addisonian crisis. Administer DOCP intramuscularly during an addisonian crisis because the drug may be poorly absorbed in dehydrated, hypovolemic, hypotensive patients if given subcutaneously.

As an alternative to DOCP, you may administer fludrocortisone acetate (Florinef—Bristol-Myers Squibb), which has mineralocorticoid and glucocorticoid activities. But this drug must be given orally, and addisonian dogs are already likely experiencing gastrointestinal dysfunction such as vomiting or gastric bleeding. Furthermore, DOCP corrects the electrolyte abnormalities that occur with hypoadrenocorticism better than fludrocortisone does.5

After one or two hours, decrease the saline solution administration rate to meet the dog's fluid replacement needs. If the dog doesn't respond well to the above therapy within 24 hours, reassess your diagnostic test results thoroughly.

MAINTENANCE MINERALOCORTICOID AND GLUCOCORTICOID THERAPY

As you transition to maintenance therapy for hypoadrenocorticism, recheck dogs two weeks after the first DOCP injection and every week thereafter, and measure serum electrolyte concentrations. By assessing patients for hyperkalemia and hyponatremia, you will be better able to determine the DOCP administration interval. The frequency of DOCP administration is determined by the time the sodium or potassium concentration, or both, is no longer in the reference range after the initial dose of DOCP.

In my experience, some dogs may require a DOCP dosing interval of every two weeks and others may require a dosing interval of every eight weeks (the labeled dosing interval is every 25 days). Furthermore, I have found that large dogs (> 50 lb) may need only 0.5 mg/lb DOCP, and if their electrolyte concentrations are normal at four weeks after the first injection, you may be able to effectively treat these patients with an even lower dose. DOCP is also effective when given subcutaneously,6 and we have taught our clients how to administer these injections at home, thus saving the expense and time of a trip to the hospital for dogs that are stable.

Fludrocortisone acetate may be used as maintenance mineralocorticoid replacement therapy, but it is inferior to DOCP with respect to normalization of serum sodium and potassium concentrations. And in dogs weighing > 20 to 25 lb, it will be more expensive than DOCP.

In dogs with stable disease, perform a recheck examination and laboratory tests every four to six months and anytime the dog becomes ill.

Glucocorticoid supplementation (0.2 to 0.4 mg/kg prednisone given orally once a day or every other day) will be needed as part of lifelong treatment in dogs receiving DOCP. Instruct clients that the dose will need to be increased in times of illness or other stress, such as hospitalization or boarding. When a stressful episode is anticipated, administer additional glucocorticoids the day before and two or three days after the event.

David S. Bruyette, DVM, DACVIM
VCA West Los Angeles Animal Hospital
1818 S. Sepulveda Blvd.
West Los Angeles, CA 90025

REFERENCES

1. Peterson ME, Kintzer PP, Kass PH. Pretreatment clinical and laboratory findings in dogs with hypoadrenocorticism: 225 cases (1979-1993). J Am Vet Med Assoc 1996;208(1):85-91.

2. Oberbauer AM, Bell JS, Belanger JM, et al. Genetic evaluation of Addison's disease in the Portuguese water dog. BMC Vet Res 2006;2:15.

3. Sadek D, Schaer M. Atypical Addison's disease in the dog: A retrospective survey of 14 cases. J Am Anim Hosp Assoc 1996;32(2):159-163.

4. Chow E, Campbell WR, Turnier JC, et al. Toxicity of desoxycorticosterone pivalate given at high doses to clinically normal Beagles for six months. Am J Vet Res 1993;54(11):1954-1961.

5. Kintzer P, Peterson M. Treatment and long-term follow-up of 205 dogs with hypoadrenocorticism. J Vet Intern Med 1997;11(2):43-49.

6. McCabe MD, Feldman EC, Lynn RC, et al. Subcutaneous administration of desoxycorticosterone pivalate for the treatment of canine hypoadrenocorticism. J Am Anim Hosp Assoc 1995;31(2):151-155.


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