• Christine A Boehm, Elizabeth L Carney, Ronald J Tallarida, and Ronald P Wilson.
• Laboratory Animal Resources, Florida State University, Tallahassee, FL, USA.
• Vet Anaesth Analg. 2010 Nov 1; 37 (6): 550-6.

ObjectiveTo investigate the analgesic properties of different dose combinations of midazolam and dexmedetomidine administered intraperitoneally (IP) in the rat.Study DesignProspective experimental trial.AnimalsSeventy adult male Sprague Dawley rats weighing 250-300 g.MethodsDexmedetomidine (D) 0.03, 0.06, 0.09, 0.12, 0.15, 0.18, 0.21 mg kg(-1) and midazolam (M) 5, 10, 25, 50 mg kg(-1) were administered IP, alone then in combinations ranging from 0.03 D:5 M to 0.18 D:30 M mg kg(-1). Analgesia was evaluated using the tail-flick test at time 0 (before injection), 15, 30, 45, 60 and 75 minutes.ResultsMidazolam at all doses administered (5-50 mg kg(-1)) did not significantly change tail-flick latencies from baseline values whereas D showed clear dose-dependent increases in tail-flick latency for doses administered in the range of 0.03-0.18 mg kg(-1). Tail-flick latencies in rats administered D+M combinations were significantly greater than D alone (p<0.05).ConclusionsA dose-related analgesic effect was demonstrated for D in the rat, which was enhanced by co-administration of M.Clinical RelevanceThe combination of D+M administered IP to rats at doses of 0.12:20 and 0.09:15 mg kg(-1) was shown to be a good combination to provide sedation/analgesia with a duration of action greater than 60 minutes. The onset of sedation was rapid (1-3 minutes), and onset of profound analgesia was reached within 5-10 minutes.© 2010 The Authors. Veterinary Anaesthesia and Analgesia © 2010 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

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