Effects of Atipamezole on the Analgesic Activity of Butorphanol in Rats

The aim of this study was to evaluate the effect of atipamezole on the analgesic efficacy of butorphanol in rats. Forty adult male Wistar rats were used, with the heart rate, respiratory rate, and plantar withdrawal latency being measured prior to and following injection of butorphanol (B), atipamezole (A), butorphanol followed by atipamezole (BA), and saline solution (S). Heart and respiratory rates in Group A were consistently higher than in all other groups, and in Group BA these physiologic parameters were higher than that in Group B. Plantar withdrawal latency was significantly prolonged in Group B, while it was significantly reduced in Group A at multiple time points when compared with Group S. B. There were no significant differences between groups BA and S. Results obtained from this investigation indicate that atipamezole induces a partial or complete antagonism of butorphanol and its analgesic activity, which is very important when a combination of α2-agonist agents and butorphanol is used as a premedication protocol before major surgical procedures, as the atipamezole administration reverses both drugs. In these cases, it is suitable to use another analgesic drug with α2-agonist agents to ensure adequate postoperative analgesia.