Evaluation of the Analgesic Effects of Butorphanol Tartrate, Xylazine Hydrochloride, and Flunixin Meglumine in Leopard Frogs (Rana pipiens)

The use of amphibians in biomedical research is increasing; however, very little information exists on the use and effectiveness of analgesics in these animals. Numerous similarities have been documented between the nervous system and pain perceptive pathways of mammals and frogs, thus supporting the need for the use of analgesics in frogs undergoing potentially painful procedures. Leopard frogs were evaluated for the analgesic effects of xylazine hydrochloride, flunixin meglumine, and butorphanol tartrate by intracelomic injections of variable doses of these analgesic agents and measurement of the pain threshold, using acetic acid as the painful stimulus. All three compounds were found to provide good analgesia for 2 to 4 hours, and butorphanol tartrate (25 mg/kg of body weight) was effective for up to 12 hours; however, xylazine hydrochloride (10 mg/kg) induced the best, long-lasting (12 to 24 hours) analgesic effect.