Effects of acepromazine and xylazine on subjective and objective assessments of forelimb lameness.

Abstract

BACKGROUND\nTo facilitate lameness evaluation, sedatives such as xylazine and acepromazine are regularly used in the clinical setting, despite concerns that they may confound lameness assessment.\n\n\nOBJECTIVES\nThe objective of this study was to determine the effect of low doses of acepromazine and xylazine on subjective and objective lameness assessment.\n\n\nSTUDY DESIGN\nRandomised, blinded, crossover study.\n\n\nMETHODS\nSix horses with experimentally induced solar pain were evaluated over a one-hour period after treatment with intravenous xylazine (0.1 or 0.2 mg/kg), intravenous acepromazine (0.02 or 0.04 mg/kg), intravenous saline (1 ml), or local analgesia (4 ml 2% mepivacaine administered subcutaneously). Lameness was assessed objectively with inertial sensors and subjectively on a scale from 0 to 5. Lameness assessments were compared with logistic regression analysis to account for the repeated measures and cross-over study design (P<0.05).\n\n\nRESULTS\nXylazine (0.1 and 0.2 mg/kg) or acepromazine (0.02 and 0.04 mg/kg) did not result in significant differences in objective lameness assessment (vector sum) or average subjective lameness grade. Local analgesia was associated with a decrease in subjective lameness grade (OR 0.32 [0.11 - 0.92], P = 0.03). Objective measures of lameness (vector sum) were significantly decreased 45 minutes (vector sum 41.8, P = 0.04) and 60 minutes (vector sum 47.3, P = 0.03) following local analgesia administration compared to baseline (vector sum 121.4).\n\n\nMAIN LIMITATIONS\nExtrapolation of the experimental model of moderate lameness used in this study to broad range of clinical lameness situations should be performed carefully.\n\n\nCONCLUSIONS\nThese results support the use of low doses of xylazine or acepromazine to facilitate forelimb lameness evaluation up to one hour in duration.