title: Effects of multiple intramuscular injections and doses of dexamethasone on plasma cortisol concentrations and adrenal responses to ACTH in horses.
abstract: Adrenocortical function was assessed in horses given multiple IM doses of dexamethasone to determine the duration of adrenocortical suppression and insufficiency caused by 2 commonly used dosages of dexamethasone (0.044 and 0.088 mg/kg of body weight). Dexamethasone was administered at 5-day intervals for a total of 6 injections. Daily blood samples were collected. The plasma was frozen and later assayed for cortisol. An ACTH response test was determined 2 days before the first injection of dexamethasone and again 8 days after the last dexamethasone injection. Maximum suppression of plasma cortisol was observed in horses given both dosages of dexamethasone (0.044 and 0.088 mg/kg). Plasma cortisol concentrations returned to base-line values in all horses by 4 days after dexamethasone injection. Normal ACTH responses observed after 6 dexamethasone injections given at 5-day intervals indicated that measurable adrenal atrophy did not develop under the conditions of this study.
mesh_terms: D000302:Adrenal Cortex / Q000187:drug effects*; D000309:Adrenal Insufficiency / Q000139:chemically induced / Q000662:veterinary; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D003907:Dexamethasone / Q000008:administration & dosage* / Q000494:pharmacology; D005260:Female; D006734:Horse Diseases / Q000139:chemically induced; D006736:Horses / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood*; D007273:Injections, Intramuscular; D008297:Male
chemical_list: D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone