After oral administration of Detomidine, an analgesic sedative for large animals, to two stallions and intravenous injection of [3H]-Detomidine into mares, the metabolites in horse urine were studied. After oral doses, a combination of totomidine carboxylic acid and hydroxytomtomidine glucuronic acid was identified in the urine. About 12 hours after the intravenous injection, about half of the radioactivity of [3H]-tomtomidine was excreted into the urine. Dose (80μg/kg). Compared with the highest urine output 2 to 5 hours after urination, most excretion occurs between 5 and 12 hours. The main radioactive metabolite in urine is totomidine carboxylic acid. In all collected urine fractions, totomidine carboxylic acid accounts for more than two-thirds of the total metabolites.