Postoperative analgesia using phenylbutazone, flunixin or carprofen in horses

Horses undergoing surgery were randomly assigned to one of three groups to receive phenylbutazone at 4 mg/kg (n = 72), flunixin at 1 mg/kg (n = 68) or carprofen at 0.7 mg/kg (n = 63) by slow intravenous injection at the end of surgery, just before they were disconnected from halothane. Pain was assessed by either of two resident surgical clinicians (who did not know which non-steroidal anti-inflammatory drug had been given) when the horses first stood up, two and four hours later and the next morning. If repeated doses of analgesic drugs were given the time was recorded and taken as an end point for the study. The presence or absence of side effects was also recorded. In the three groups there was no significant difference between the types of surgery performed, the numbers of horses requiring further analgesia or the pain scores at any time. In the horses needing further analgesia there was a significant difference in the time after surgery at which the further analgesia was given between those in the flunixin group, 12.8 +/- 4.3 hours (mean +/- sd) and those in the phenylbutazone group, 8.4 +/- 4.6 hours; the carprofen group had an intermediate interval of 11.7 +/- 6.9 hours. Significantly fewer of the horses that received butorphanol during surgery needed further analgesia than of those that did not receive any opioid.