Although various methods have been developed for diagnosing hyperadrenocorticism in dogs, ACTH stimulation testing is preferred in certain situations.1 In addition, ACTH stimulation testing is the only method of documenting hypoadrenocorticism in dogs and for assessing the response to mitotane, trilostane, or ketoconazole treatment in dogs with hyperadrenocorticism.
To date, the only commercially available form of ACTH proven to be effective for stimulation testing of dogs with adrenal gland disease is cosyntropin. Because the cost of this drug is so high, using a reduced dose would be helpful in decreasing the overall expense of ACTH stimulation testing. However, for reliable diagnosis of hyperadrenocorticism, a dose high enough to provide maximal adrenal gland stimulation must be used. Previous studies2–4 have found that IV administration of cosyntropin at a dose of 5 mg/kg (2.3 mg/lb) provides maximal adrenal gland stimulation, but when the IM route of administration is used, only a dose of 250 mg has been verified to provide maximal stimulation.5 Intramuscular administration could be advantageous in dogs in which IV injection is difficult, such as small or aggressive dogs, and in dogs that weigh < 50 kg (110 lb), use of a dose of 5 mg/kg would be < 250 mg, providing an economic benefit.
The purpose of the study reported here, therefore, was to compare adrenal gland stimulation achieved following administration of cosyntropin at a dose of 5 mg/kg, IM, with stimulation achieved following administration of the same dose IV.
Cortrosyn, Amphastar, Rancho Cucamonga, Calif.
Coat-a-Count cortisol assay, Diagnostic Products Corp, Los Angeles, Calif.
SigmaStat for Windows, version 1.0, Jandel Scientific, SPSS Inc, Chicago, Ill.
Frank LA, DeNovo RC, Kraje AC, et al. Cortisol concentrations following stimulation of healthy and adrenopathic dogs with two doses of tetracosactin. J Small Anim Pract 2000;41:308–311.
Kerl ME, Peterson ME, Wallace MS, et al. Evaluation of a low-dose synthetic adrenocorticotropic hormone stimulation test in clinically normal dogs and dogs with naturally developing hyperadrenocorticism. J Am Vet Med Assoc 1999;214:1497–1501.
Watson ADJ, Church DB, Emslie DR, et al. Plasma cortisol responses to three corticotrophic preparations in normal dogs. Aust Vet Pract 1998;76:255–257.
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Hill KE, Scott-Moncrieff JCR, Moore GE. ACTH stimulation testing: a review and a study comparing synthetic and compounded ACTH products. Vet Med 2004;99:134–146.
Feldman EC, Stabenfeldt GH, Farver TB, et al. Comparison of aqueous porcine ACTH with synthetic ACTH in adrenal stimulation tests of the female dog. Am J Vet Res 1982;43:522–524.