High
Dose Dexamethasone Suppression
Indications:
In dogs already diagnosed as
having hyperadrenocorticism (by ACTH stimulation or low dose
dexamethasone suppression) this test is useful in differentiating
pituitary from adrenal dependent disease.
Notes:
High dose dexamethasone
suppression is a sensitive test for adrenal neoplasia but is not
highly specific. A small proportion of dogs (10-20%) will show
results consistent with adrenal neoplasia despite having
pituitary dependent disease. For this reason, confirmation by
another modality (abdominal radiography or ultrasonography)
should be sought in animals with apparent adrenal-dependent
disease.
Protocol:
The dexamethasone supplied by
IDEXX Laboratories has a higher concentration of 4mg/ml, which is
higher than in some veterinary products licensed for IV use.
Using our
dexamathasone:
- The total injectable dose (ml) =
(bodyweight (kg) X 0.1) / 4
- Collect 1-2 ml blood in plain/gel tube for basal
cortisol concentration
- Immediately inject dexamethasone (0.1 mg/kg iv)
- Collect second blood sample for suppression test 3
hours post-injection
- Collect third blood sample for suppression test 8
hours post-injection
- Label tubes with name and time of sample. Submit
tubes and request form to the laboratory
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