"In the last few years, there has been a large increase in awareness of treating pain in horses; many practitioners want to know how to do it better," began Nora Matthews, DVM, Dipl. ACVA, professor of anesthesia at Texas A&M University. During the 2009 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas, Nev., she discussed the current usage of analgesics (painkillers) in equine medicine and what's needed to improve their use.

The advantages of using painkillers in horses are that they help an injured or ill horse feel better, eat more, lose less weight, stay in the hospital for a shorter time, and often avoid chronic pain, she explained. The potential disadvantages include the possibility that the horse makes the injury worse by being too active because he doesn't hurt as much, the fact that painkillers can slow down the GI tract (potentially contributing to colic), the high cost of many painkillers, and the fact that masking pain can also mask any worsening of the painful condition.

Since a horse can't tell you when, where, or how badly he hurts, veterinarians have to assess his pain by evaluating physical mechanisms (such as heart rate and levels of cortisol, often called the stress hormone), responses to pressure on the sore area, changes in force plate results for lameness cases, and changes in behavior. One of the hardest things about studying pain in horses is that there are various systems for grading pain and improvement; it's much more difficult to objectively assess pain than "harder" targets such as levels of substances in the bloodstream.

Painkillers can be given in a variety of ways, whether systemically (orally, intravenously, intramuscularly, etc.) or locally to block pain in a specific area of the body. Matthews expressed hope for the newer transdermal (through the skin) analgesic options, which are less invasive than many other administration routes and thus better tolerated by horses and their owners