Yohimbine hydrochloride is an alpha 2-adrenoreceptor antagonist, blocking the pre- and postsynaptic alpha-2 adrenoreceptors and causing an increased release of noradrenaline and dopamine.It is an antagonist to xylazine hydrochloride-ketamine hydrochloride immobilization of white-tailed deer. Yohimbine has been used as a mydriatic and in the treatment of impotence. It is also alleged to be an aphrodisiac.