Atipamezole reverses ketamine-dexmedetomidine anesthesia without altering the antinociceptive effects of butorphanol and buprenorphine in female C57BL/6J mice.

Butorphanol and buprenorphine are common analgesics used in laboratory mice. Inadvertent attenuation of the antinociceptive effects of these analgesics via the administration of an anesthetic reversal agent could result in postprocedural pain and distress, with subsequent negative effects on animal welfare, study outcomes, and regulatory compliance. This study was undertaken to determine whether atipamezole reverses ketamine-dexmedetomidine anesthesia and alters the antinociceptive effects of butorphanol and buprenorphine in female C57BL/6J mice. Atipamezole reliably reversed the anesthetic effects of ketamine-dexmedetomidine, and mice were ambulatory 17.4 ± 30.6 min after administration of the α2-adrenoreceptor antagonist. Atipamezole alone had no significant effect on tail-flick latency and did not alter the antinociceptive properties of butorphanol or low-dose (0.05 mg/kg) or high-dose (0.1 mg/kg) buprenorphine in female C57BL/6J mice. After reversal of ketamine-dexmedetomidine anesthesia, tail-flick latency at 30, 60, and 150 min after analgesic treatment differed significantly between mice treated with atipamezole alone and those given atipamezole followed by butorphanol or high-dose buprenorphine. These results suggest that the analgesic effects of butorphanol and buprenorphine are not affected by atipamezole. Buprenorphine (0.1 mg/kg) administered 30 min prior to or at the time of anesthesia resulted in a greater magnitude of antinociception after antagonism of anesthesia than when given at the time of reversal. Given these results, we recommend the use of ketamine-dexmedetomidine anesthesia with buprenorphine administered either preemptively or at the time of anesthetic induction to provide a defined period of surgical anesthesia that is effectively reversed by atipamezole.