Effect of Intravenous or Perivascular Injection of Synthetic Adrenocorticotropic Hormone on Stimulation Test Results in Dogs.

BACKGROUND: Standard protocols for adrenocorticotropic hormone (ACTH) stimulation testing (ACTHst) often involve intravenous (IV) injection of corticotropin. ACTH might be unintentionally injected into the perivascular (PV) space. OBJECTIVE: To compare stimulation test results after IV and PV injections of ACTH. ANIMALS: Twenty privately owned dogs were studied: 10 healthy and 10 with trilostane-treated naturally occurring hyperadrenocorticism (HAC). METHODS: Prospective study. Each of 20 dogs underwent 2 ACTHst not <4 nor more than 14 days apart. Five healthy and 5 HAC dogs had an IV ACTHst first and PV second; 5 healthy and 5 HAC dogs had a PV ACTHst first and IV second. Blood samples for measurement of serum cortisol concentration were collected before and 1 hour after ACTH administration. RESULTS: No significant difference in results was demonstrated when comparing serum cortisol concentrations after IV and PV ACTH administration in all 20 dogs (median µg/dL; interval µg/dL: 8.2; 1.4-17.4 versus 7.8; 0.9-16.9; P = .23). No significant difference in results was demonstrated when comparing serum cortisol concentrations after IV and PV ACTH administration in the 10 healthy dogs (median µg/dL; interval µg/dL: 10.9; 7.3-17.4 versus 10.6; 7.1-16.9; P = .54) or in the 10 HAC dogs (median µg/dL; interval µg/dL: 6.3; 1.4-8.6 versus 5.2; 0.9-8.7; P = .061). CONCLUSIONS AND CLINICAL IMPORTANCE: Perivascular administration of ACTH does not significantly alter stimulation test results in healthy dogs or in dogs with HAC undergoing therapy with trilostane.

Comparison of adrenocorticotropic hormone stimulation test results started 2 versus 4 hours after trilostane administration in dogs with naturally occurring hyperadrenocorticism.

BACKGROUND: Trilostane medical treatment of naturally occurring hyperadrenocorticism (NOH) in dogs is common, as is use of the adrenocorticotropic hormone (ACTH) stimulation test (ACTHst) in monitoring response to treatment. There is uncertainty regarding when the ACTHst should be started relative to time of trilostane administration. OBJECTIVE: To compare ACTHst results in dogs being treated for NOH with trilostane when the test is begun 2 versus 4 hours after trilostane administration. ANIMALS: Twenty-one privately owned dogs with NOH, each treated with trilostane for at least 30 days. METHODS: Each dog had 2 ACTHst completed, 1 started 2 hours and the other 4 hours after trilostane administration. The second test was started no sooner than 46 hours and no later than 74 hours after the first. RESULTS: For all 21 dogs, the mean post-ACTH serum cortisol concentration from tests started 2 hours after trilostane administration (5.4 ± 3.7 µg/dL) was significantly lower (P = .03) as compared with results from the tests started 4 hours after administration (6.5 ± 4.5 µg/dL). CONCLUSIONS: Results of ACTHst started at different times yield significantly different results. Dogs with NOH, treated with trilostane, and monitored with ACTHst results should have all of their subsequent ACTHst tests begun at or about the same time after trilostane administration.

Comparison of IV and IM formulations of synthetic ACTH for ACTH stimulation tests in healthy dogs.

BACKGROUND: Two commercially available forms of synthetic ACTH are used to diagnose and monitor hyper- and hypoadrenocorticism in dogs. OBJECTIVE: To compare the biologic activity of the liquid and lyophilized forms of cosyntropin. ANIMALS: Eighteen privately owned healthy dogs were included. METHODS: Dogs were assigned to one of 2 groups of 9 dogs each. Group 1 dogs were tested with the lyophilized product first and the liquid solution 30-60 days later. The Group 2 dogs were tested with the liquid solution first and the lyophilized drug 30-60 days later. For the ACTH stimulation tests, serum samples were collected before and 1 hour after IM administration of 0.25 mg reconstituted lyophilized product or 1 hour after IV administration of 0.25 mg of liquid solution. Cortisol concentrations of all serum samples were measured by use of a commercial cortisol radioimmunoassay. RESULTS: Serum cortisol concentrations before and after ACTH stimulation did not differ significantly between groups (P = .57). In addition, no individual dog had as much as a 20% difference in serum cortisol concentrations after administration of either ACTH formulation. CONCLUSIONS AND CLINICAL IMPORTANCE: Given the lack of significant differences of the ACTH stimulation test results, the lyophilized and liquid solution products can be used interchangeably.