Multicenter clinical comparison of sedative and analgesic effects of medetomidine and xylazine in dogs

Abstract

Objective - To evaluate analgesic and sedative effects of medetomidine hydrochloride in dogs and to compare effects with those of xylazine hydrochloride. Design - Randomized, controlled trial. Animals - 184 dogs that required sedation or analgesia for completion of minor diagnostic or therapeutic procedures Procedure - Dogs were sedated with medetomidine. IV (750 μg/m2 of body surface area) or IM (1,000 μg/m2) or with xylazine, IV (1.1 mg/kg [0.5 mg/lb] of body weight) or IM (2.2 mg/kg [1 mg/lb]). Sedative effects were measured by scoring posture and response to noise. Durations of effects were determined by measuring time intervals between drug administration and changes in posture Analgesic effects were measured by deter- mining toe-pinch pressure needed to elicit a withdrawal response. Clinicians rated sedative and analgesic effects and ease with which diagnostic or therapeutic procedures could be performed. Results - Posture end response to noise scores were significantly higher for dogs given medetomidine. IM, than for dogs given xylazine, IM, and for dogs given medetomidine, IV, than for dogs given xylazine, IV. Time to regaining sternal recumbency and time to regaining ability to stand were longest after IM administration of medetomidine. Toe-pinch pressures were not significantly different among groups. Clinicians rated overall analgesic and sedative effects as excellent significantly more often after administration of medetomidine than after administration of xylazine. Prevalence of adverse effects did not differ among groups Clinical Implications - Medetomidine and xylazine, at doses tested, were effective and safe, out results of subjective measurements indicated that medetomidine provided better sedation and analgesia than did xylazine. Specific α2 -adrenergic antagonists (atipamezole, yohimbine) are available for control of adverse cardiovascular effects.