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Author: Admin | 2025-04-28
Its muscle relaxant effect is based on inhibition of the intraneural transmission of impulses in the central nervous system.Adverse effects of xylazine can include muscle tremors, seizures or slowed heart rate with partial heart block and slowed breathing rate. Ruminants have increased sensitivity to the sedative/hypnotic effects of α2-agonists compared to other species.3 Being an α-2 adrenergic agonist, xylazine’s effects can be antagonized with the α-antagonists.In cases where remote immobilization is a necessity, and in general with wildlife in the field, drugs with fast induction and shorter recovery times, or drugs that can be readily reversed are ideal. Thus, the search for superior reversal agents for wildlife species is an ongoing proposition. Yohimbine is an α-2 adrenergic antagonist that antagonizes the effects of xylazine and other α-2 adrenergic agonists. A study in horses that received detomidine 0.03 mg/kg IV followed 15 minutes later by yohimbine 0.2 mg/kg IV found that yohimbine rapidly reversed the sedative effects of detomidine, effectively returned heart rate and the percent of atrioventricular conduction disturbances to pre-detomidine values, and effectively reduced detomidine-induced hyperglycemia.5TolazolineTolazoline is an α-antagonist labeled for human use. It is FDA-approved and indicated for the reversal of effects associated with xylazine in horses. It also will reverse the analgesic effects of α-agonists. Tolazoline antagonizes the effects of detomidine more completely, hastens recovery, and lasts longer than atipamezole. Tolazoline is rapid acting, but may not fully reverse effects on sedation or heart rate and rhythm.While both yohimbine and tolazoline have been evaluated as reversal agents for xylazine and other α-2 adrenergic agonists, there are few comparative studies of these where wild and exotic species are concerned.6 Since xylazine is common in veterinary regimens for sedation and anesthesia, the best α-antagonists would be of significant value to shorten the α2-agonist-induced sedation, to eliminate their effects when adverse cardiopulmonary responses occur, and to treat animals receiving an overdose. Based on the available literature, the decision as to whether to choose yohimbine or tolazoline as a reversal agent is largely based upon the species being immobilized, and the experience and preference of the attending veterinarian.1Kilpatrick, H.J., Spohr, M..
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