Page 118 - Clinical Small Animal Internal Medicine

86 Section 2 Endocrine Disease

mineralocorticoid supplementation (fludrocortisone or DOCP injections must also receive a glucocorticoid, as
VetBooks.ir DOCP) is provided following definitive diagnosis of DOCP has no glucocorticoid activity.
Side‐effects of DOCP are uncommon, but polyuria/
HOAC. Dexamethasone should be continued at a dose
of 0.15–0.2 mg/kg/day until prednisone can be given
due to concurrent prednisone administration. However,
orally. Prednisone is then started at 0.5 mg/kg BID. polydipsia (PU/PD) has been reported. This is usually
Following discharge of the patient, prednisone is usu- PU/PD is occasionally reported to be worse immediately
ally tapered to approximately 0.5 mg/kg per day, and following DOCP injection, and to improve throughout
then decreased based on clinical signs, as discussed in the month. In these cases, prolonging the dose interval
chronic management. or decreasing the dose, while monitoring electrolytes,
Most patients in Addisonian crisis respond quickly to may result in improvement.
treatment (within hours), although more severely debili- Fludrocortisone is a shorter‐acting oral mineralo-
tated patients may take 2–3 days to demonstrate dra- corticoid that is available in 0.1 mg pills. The starting
matic improvement. Dogs are usually discharged 3–5 dose is 0.01 mg/kg twice daily. Electrolytes are meas-
days after initial presentation. ured in one‐week increments until they are within
the reference range. If hyponatremia and/or hyper-
Chronic Management kalemia are present, the dose is increased by 0.05–
Chronic therapy for hypoadrenocorticism consists 0.1 mg/day. If hypernatremia and/or hypokalemia are
of life‐long glucocorticoid and mineralocorticoid present, the dose is decreased. Once the dose has
supplementation to replace the missing cortisol and normalized, electrolyte concentrations are rechecked
aldosterone. every 3–6 months. The dose often increases during
Mineralocorticoids are given to correct hyper- the first 1–2 years of therapy. Since fludrocortisone
kalemia, hyponatremia, and hypochloremia. Either a has some glucocorticoid activity, only approximately
monthly injection or a twice‐daily pill can be used. 50% of dogs need additional glucocorticoids long
Desoxy corticosterone pivalate is a long‐acting, inject- term. However, all dogs are started on concurrent
able mineralocorticoid. It is initially administered at a prednisone therapy at initial diagnosis, which is then
dose of 2.2 mg/kg, subcutaneously or intramuscularly, tapered as necessary.
every 25 days. Electrolyte concentrations are then Polyuria, polydipsia, polyphagia, and panting are the
measured two weeks and 25 days following the first most commonly reported side‐effects of fludrocortisone
injection. The 14‐day measurement helps determine therapy. Most of these are due to the glucocorticoid
whether the dose is sufficient, whereas the 25‐day properties of fludrocortisone, and resolve when the
recheck confirms that the interval is acceptable. If patient is switched to DOCP.
hyperkalemia and/or hyponatremia are present, the DOCP is available in two veterinary‐approved
dose (14‐day recheck) is increased by 10–15%, or the products (Zycortal®, Dechra; Percorten‐V®, Elanco).
interval is decreased by two days (25‐day recheck). Fludrocortisone is available thro ugh human
The author usually increases the dosing interval by pharmacies.
2–3 days each month, measuring the electrolytes Glucocorticoids are used to control the nonspecific
before each injection to ensure that they are within and gastrointestinal signs associated with hypoadreno-
reference range, until the interval reaches 30–31 days, corticism, and prednisone is most frequently used. All
for owner convenience. Most dogs also do not require dogs receiving DOCP need glucocorticoid supplemen-
the entire 2.2 U/kg, and since DOCP is expensive, the tation, and about 50% of dogs taking fludrocortisone
dose can be decreased by approximately 10% per will need additional glucocorticoid supplementation
month, measuring electrolytes immediately prior to long term. The physiologic dose of prednisone is 0.1–
each injection to ensure that the electrolyte concen- 0.25 mg/kg/day, although many dogs (particularly
trations are still acceptable. The author usually starts larger breeds) do well on 0.05 mg/kg/day or less. The
with 1.5 mg/kg and rarely decreases below 1 mg/kg/ dose is tapered to effect, based on the clinical signs. If
month. Clients must understand that using lower the dog has any gastrointestinal signs or continues to
doses leaves room for less error and requires tight display vague clinical signs, the dose is increased. If
adherence to the dosing schedule. Owners must be PU/PD, polyphagia, or panting occur, the dose needs
warned not to prolong the dosing interval to save to be decreased. Remember that the dose is adjusted
money without veterinary advice; this often results in based on clinical signs, and that an ACTH stimulation
Addisonian crisis, which is significantly more expen- test is never required to monitor patients with primary
sive to treat than a single injection of DOCP. hypoadrenocorticism.
Following stabilization of DOCP dose, electrolytes During times of stress, the prednisone dose is usually
should be measured every 3–6 months. Dogs receiving increased by 2–4 times (two times is usually sufficient).