Local Analgesia Aids Castration Pain Control

Adding a local analgesic to the systemic pain medications used during castration relieved pain in colts, researchers recently reported.

The researchers observed three groups of 12 colts. All of the horses received pain medication before and after surgery. One group received butorphanol, a morphine derivative; one received phenylbutazone, an anti-inflammatory; and the third received both drugs. All of the horses also received an injection of lidocaine into each testicle at the time of castration.

The researchers assessed the horses' pain several times a day before, during, and for four days after castration by reviewing the animals' cortisol levels, pain scores, behavior, body weight, eating and drinking, gastrointestinal motility, and physical activity.

"Our study showed that when a local anesthetic like lidocaine is used under anesthesia, there is no advantage of using butorphanol over phenylbutazone," said Macarena G. Sanz, DVM, MS, Dipl. ACVIM, who was with Washington State University during the study, but is now with the University of Pretoria in South Africa.

Because butorphanol, a controlled substance, is more expensive and harder to administer than phenylbutazone, phenylbutazone might be a better choice for pain management during castration when lidocaine is added. The group did not observe an advantage to pairing butorphanol and phenylbutazone.

"It is important to understand that castration is a surgery, and like any surgery, causes pain," Sanz said. "In the past, we did not pay sufficient attention to the management of the pain and inflammation after castration. The fact that we didn't do it doesn't mean that it is not important. We have all realized the importance of animal welfare. As veterinarians and horse owners it is our responsibility to provide the best care for our animals."

The study, "Analgesic effects of butorphanol tartrate and phenylbutazone administered alone and in combination in young horses undergoing routine castration," was published in the Nov. 15, 2009, Journal of the American Veterinary Medical Association. The abstract is available on PubMed.

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