Urinary cortisol level intra-articular dexamethasone treatment in horse

Recently, Abraham et al. (2009) proved that, in horses, the repeat therapeutic dermal application of desamethasone (DEX) reduces the plasma cortisol (F) level and alters leukocyte distribution for at least fifteen days, causing potential risks even at recommended dosages. In cattle the fall of urinary F level was proved as a good marker to evaluate the systemic absorption of DEX administered orally and at very low dosage for anabolic purposes (Capolongo et al 2007). On that basis urine can be considered a suitable matrix to be sampled to monitor DEX systemic absorption and the incidence of adverse effect, when other topical route are adopted in horse therapy such as intra-articular administration, more frequently used than the dermal one. For this purposes the urine of 7 horses therapeutically treated once, with DEX at 4 mg/head, were collected at time 0 (immediately before administration) and after 24, 48, 72 and 96 hrs. The urine samples were analyzed to detect F by RIA and 6betaOHcortisol (6betaOHF) and DEX by ELISA. While residue level of DEX were detected only in urine collected at 24 hrs, the excretion of F and 6betaOHF was reduced up to 48 hours. Preliminary results confirm that entity and duration of systemic effect in horse treated with DEX by intra-articular route are strictly related to the short term treatment. This project was supported by University of Padua: CPDA077393