Midazolam enhances the analgesic properties of dexmedetomidine in the rat

To investigate the analgesic properties of different dose combinations of midazolam and dexmedetomidine administered intraperitoneally (IP) in the rat. Prospective experimental trial. Seventy adult male Sprague Dawley rats weighing 250-300 g. Dexmedetomidine (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. Midazolam 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