Antinociceptive properties of tiletamine-zolazepam improved by addition of xylazine or butorphanol

A combination of tiletamine HCl and zolazepam HCl is frequently used as an anesthetic, but little is known about the antinociceptive properties of tiletamine-zolazepam. The antinociceptive properties of tiletamine-zolazepam alone or combined with xylazine or butorphanol were determined in the adult male rate using the tail-flick test. Changes in tail-flick latency were determined at 15, 45, and 75 min after IP drug administration of sterile water, sodium pentobarbital, morphine, tiletamine-zolazepam, xylazine, butorphanol, and tiletamine-zolazepam plus xylazine or butorphanol. Tail-flick latency approximated 100% maximum possible effect (MPE) at 15-75 min postinjection in morphine-treated rats. Tiletamine-zolazepam, xylazine, and butorphanol alone, at any dose utilized, produced less than 50% MPE. However, the combination of tiletamine-zolazepam with butorphanol or xylazine increased tail-flick latency approximately three times greater than tiletamine-zolazepam alone. These results demonstrate that: a) consonant with earlier findings, analgesia and anesthesia are independent states; b) tiletamine-zolazepam is not an effective combination with respect to analgesia; but c) in concert with appropriate drugs, it can exhibit potent antinociceptive properties.