A comparison of transdermal fentanyl versus epidural morphine for analgesia in dogs undergoing major orthopedic surgery.

Postoperative analgesia provided by transdermal fentanyl was compared with that provided by epidural morphine in dogs undergoing major orthopedic surgery. Dogs randomly were assigned to receive either a 100 microg per hour transdermal fentanyl patch 24 hours prior to surgery (n=8) or epidural morphine (0.1 mg/kg body weight) administered following induction of anesthesia (n=10). Temperature, heart rate, respiratory rate, and pain score were recorded prior to surgery and zero, six, 18, 30, and 42 hours after surgery. Blood samples were collected from the dogs in the transdermal fentanyl group beginning 24 hours preoperatively to 42 hours postoperatively. Fentanyl concentrations were determined by radioimmunoassay. When all time periods after surgery were combined, dogs in the transdermal fentanyl group were experiencing significantly less pain after surgery than dogs given epidural morphine. The transdermal fentanyl provided analgesia after major orthopedic surgery greater than or equivalent to that of epidural morphine.