Alpha-2 blockers (or α2 blockers) are a subset of the alpha blocker class of drugs and are antagonists to the α2 adrenergic receptor. They are mainly used in research, having found limited clinical application in human medicine. They are extensively used in veterinary medicine to reverse the effects of alpha-2 agonist drugs used as sedatives, like xylazine, medetomidine and dexmedetomidine. Alpha-2 blockers increase noradrenaline release.