MULTICENTER CLINICAL COMPARISON OF SEDATIVE AND ANALGESIC EFFECTS OF MEDETOMIDINE AND XYLAZINE IN DOGS

Objective-To evaluate analgesic and sedative effects of medetomidine h ydrochloride in dogs and to compare effects with those of xylazine hyd rochloride. 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 mu g/m(2) of body surface area) or IM (1,000 mu g/m(2)) or wi th xylazine, IV (1.1 mg/kg [0.5 mg/lb] of body weight) or IM (2.2 mg/k g [1 mg/lb]). Sedative effects were measured by scoring posture and re sponse to noise. Durations of effects were determined by measuring tim e intervals between drug administration and changes in posture. Analge sic effects were measured by determining 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 and response to noise scores were signi ficantly higher for dogs given medetomidine, IM, than for dogs given x ylazine, IM, and for dogs given medetomidine, IV, than for dogs given xylazine, IV. Time to regaining sternal recumbency and time to regaini ng ability to stand were longest after IM administration of medetomidi ne. 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 aft er administration of xylazine, Prevalence of adverse effects did not d iffer among groups. Clinical Implications-Medetomidine and xylazine, a t doses tested, were effective and safe, but results of subjective mea surements indicated that medetomidine provided better sedation and ana lgesia than did xylazine. Specific alpha(2)-adrenergic antagonists (at ipamezole, yohimbine) are available for control of adverse cardiovascu lar effects.