Xylazine is an analogue of clonidine and a potent agonist at the ?2 class of adrenergic receptor. Initial hypertension is caused by xylazine�s action at peripheral postsynaptic adrenergic receptors, which produces vascular smooth muscle contraction and vasoconstriction. Eventual reductions in blood pressure are due to decreased sympathetic tone resulting from xylazine�s activation of central and presynaptic sympathetic neuronal alpha2 adrenoceptors.