Question of the Day – Friday February 8, 2019

Question – The article cited below notes that xylazine “is marketed as a veterinary drug and used as a sedative, analgesic and muscle relaxant. In humans, it could cause central nervous system depression, respiratory depression, bradycardia, hypotension, and even death.” This substance has been used to adulterate a variety of street drugs including heroin and cocaine. What is the mechanism of action of xylazine?

Answer- The cited article reports “Xylazine is a potent alpha 2-adrenergic agonist that mediates via stimulation of central alpha 2-receptors. The alpha 2 stimulation decreases the release of norepinephrine and dopamine in the central nervous system resulting in sedation, muscle relaxation, and decreased perception of painful stimuli. Its actions may also involve cholinergic, serotonergic, dopaminergic, a-1-adrenergic, histaminergic, or opiate mechanisms.” (Ruiz-Colon K et al. Xylazine intoxication in humans and its importance as an emerging adulterant in abused drugs: A comprehensive review of the literature. 2014 For Sci Int 240:1-8)