Xylazine (Xylazine HCl) is an alpha-2-adrenergic agonist (α2- adrenergic agonist) that is use as a sedative and analgesic agent in a variety of species, as well as an emetic in cats. It is FDA-approve for use in dogs, cats, horses, deer, and elk to produce a state of sedation with a shorter period of analgesia and as a preanesthetic agent before local anesthesia. It is also approve as a preanesthetic agent before general anesthesia in dogs, cats, and horses.1 Xylazine has a long-standing use for surgical proceures in small animal practices, but it is also use in large animal and wildlife applications. In veterinary anesthesia, xylazine is often use in combination with ketamine.
The sedative and analgesic activity of xylazine is relate to central nervous system depression. It provides muscle relaxation base on inhibition of the intraneural transmission of impulses in the central nervous system.2 The degree of CNS inhibition is such that xylazine provides dose-dependent, deep muscle relaxation and respiratory depression without inhibition of the nervous system’s more critical functions.
Comparative pharmacokinetics of xylazine in several species was reporte by researchers in 1981. Xylazine drug was administer intravenously and intramuscularly at recommender doses. The data was generate by analyzing serum drug concentration in samples obtain at 1, 2, 4, 8, 16, 30 and 120 min after xylazine administration. Compartmental analysis of the data was performe and the data best fitte a two-compartment open model.3,4