Combination of dexmedetomidine with buprenorphine enhances the antinociceptive effect to a thermal stimulus in the cat compared with either agent alone

Objective To evaluate the sedative and antinociceptive effects of combinations of dexmedetomidine and buprenorphine in cats. Study design Experimental randomized study. Animals Twelve purpose-bred neutered domestic short-hair cats (4 male and 8 female) weighing 4.6 kg (range 3.7-5.5 kg(-1) aged from 2 to 5 years. Methods Six cats per group were administered buprenorphine ( B) at 10 (B10) or 20 mu g kg(-1) (B20) or dexmedetomidine (D) at 20 (D20) or 40 mu g kg(-1) (D40) or a combination of B10/D20. A feline thermal nociceptive threshold testing device was used to evaluate the antinociceptive effects of the drugs before and up to 24 hours after drug treatment. Sedation was scored using a 100 mm visual analogue scale ( VAS). Results Thermal thresholds increased significantly after administration of all but D20. Area under the curve (AUC, hours degrees C) for the first 6 hours (mean +/- SD) for B20 (281 +/- 17.8) was significantly greater than B10 (260 +/- 11.4), D20 (250 +/- 7.9) and D40 (255 +/- 11.4). The AUC for B10/D20 (273 +/- 12.2) was significantly greater than D20 but not the other treatments. No sedation was seen after administration of B10 or B20 and maximal sedation was seen for all animals in the D40 and B10/D20 groups and most animals in the D20 group. Conclusions D20 alone had the smallest analgesic effect; B10 alone provided no sedation but their combination gave good sedation with analgesia comparable with B20.