Desoxycortone pivalate (DOCP) (Zycortal®, Dechra) is a pure mineralocorticoid and so concurrent doses of glucocorticoids need to be individually titrated; currently this is done on the basis of clinical signs. In contrast, most dogs treated with fludrocortisone (a mixture of mineralocorticoid and glucocorticoid) do not receive additional glucocorticoid supplementation following stabilisation. The objective of this study was to compare the ACTH concentrations in dogs treated with fludrocortisone with the same dogs when treated with DOCP and prednisolone.

A prospective, cross-over trial was performed using 33 dogs with hypoadrenocorticism who had been previously stabilised on fludrocortisone. Each dog was randomly allocated to one of two groups, each of which were treated with 3 months of fludrocortisone then 3 months of DOCP and prednisolone (or vice versa). The prednisolone dose was adjusted according to clinical signs. Two dogs failed to complete the trial. Three patients received prednisolone concurrently for at least part of the fludrocortisone phase and the data from these dogs in this phase were removed from further analysis. ACTH levels were measured at the start and end of each treatment phase using an immunoradiometric assay (NationWide Laboratories). Tests for normality were performed and Mann-Whitney U tests were used to compare the various ACTH concentrations and the prednisolone doses at the start and end of the DOCP phase. A Pearson correlation was used to compare the final prednisolone dose and ACTH concentrations at the end of the DOCP phase.

There was a significant difference between the ACTH concentrations after DOCP (median=2.5 pg/ml) compared to those after fludrocortisone (median=150 pg/ml) or before starting DOCP (median=128 pg/ml). There was also a significant reduction in prednisolone dose during the DOCP phase from a median starting dose of 0.22 mg/kg to 0.13 mg/kg. After 3 months of treatment with DOCP and prednisolone 21 out of 31 dogs had ACTH concentrations less than 10 pg/ml (suggesting suppression of the ACTH secretion). No significant correlation was found between the final prednisolone dose and the ACTH concentration at the end of the DOCP phase. In contrast, 18 of the 31 dogs had ACTH concentrations more than 100 pg/ml (possibly suggesting inadequate glucocorticoid supplementation) following 3 months of treatment with fludrocortisone.

It is concluded that in many dogs with hypoadrenocorticism being treated with DOCP, the dose of prednisolone has the potential to be further reduced based on ACTH concentrations.

Disclosures

Disclosures to report:

The lead author's position was previously funded by Dechra Ltd, the manufacturer of Zycortal. This study was funded by Dechra.