Hordenine as a stimulating drug in horses

This paper reviews the sources, identification and pharmacokinetics of hord enine. This biogenic amine is generated during the breakdown of tyramine be ginning on the first day of barley germination. It is contained in Cacti as well as in different kinds of reeds (arundinacea, canaris, and aquatica) i ncluding a variety of species cultivated in Poland (such as Motycka, Nakiel ska, and Pulawska) which contain substantial quantities of hordenine. Horse Racing Organisations in some countries consider this chemical compoun d to be a stimulant, yet in fact, hordenine from natural food stuffs contai ned in feed can reach a concentration of up to 18-90 mu g/ml in urea and up to 1 mu g/ml in serum. The pharmacological profile of hordenine shows that its stimulatory action on the respiratory and cardiovascular systems is short-lived and appears on ly when a high dose of the compound is used. Because the effects are limited in time, the compound does not alter psycho motor activity in horses. It seems that hordenine is not a stimulant in the strict sense of the word. No data is available showing its stimulatory eff ect on isolated limbs or on muscle activity. Horses which were given 1 kg barley per day (hordenine content approximate to 0,05% d.m.) could receive approximately 500 mg hordenine (approximate to 1 mg/kg B.W.).