Hydrocortisone concentrations in post-race urine from horses

As hydrocortisone is an endogenous substance, it is first necessary to esta blish its normal concentrations so as to be able to control its use in raci ng animals. This study was designed to establish the hydrocortisone concent rations in post-race urine samples of horses racing in Brazil and also to e valuate the results in relation to the international threshold set for this drug. Urine samples were analysed by HPLC-UV. The results were evaluated a ccording to the concentration range as well as sex and time of sample colle ction (afternoon or evening races). The results showed a high degree of var iation in the concentrations of hydrocortisone in the urine (93 +/- 69 ng/m l). The maximum concentration observed was 646 ng/ml, although only a few h orses (around 1%) showed levels within the range 500-650 ng/ml, 91% being i n the range 0-150 ng/ml. The data suggested a normal distribution curve. St atistical analysis showed no significant influence of sex or time of sample collection.