Pain Management

Controlling pain can actually help improve horse health.

When I graduated from veterinary college, it was common belief that a moderate amount of pain kept injured or post-surgical animals from moving too much and reinjuring themselves or tearing out sutures.

Recent research has shown there is little foundation for that belief and that pain not only delays healing but can also contribute to an injured horse experiencing excessive and even inhumane pain levels.

Aside from the pain we see with severe colic, most horses are fairly stoic and often do not show pain. A horse’s ability to perceive pain is an adaptive mechanism that protects him from further injury. We’ve learned that persistent pain, like that experienced by chronically foundered horses, triggers a series of physiological changes that affects many body systems, such as the immune system.

We now know that injured horses with well-controlled pain:

    • Maintain better appetites
    • Are not depressed or lethargic
    • Are at a lower risk of developing stomach ulcers or severe diarrhea due to colitis
    • Have a normally functioning immune system
    • Heal faster

Researchers in France showed that in a group of horses with severe back pain, 77 percent reacted aggressively toward people. In contrast, horses in the study with mild or no back pain rarely were aggressive. We have to wonder how many “bad-tempered” horses actually suffer from some form of chronic pain.

There are a number of analgesic options available to veterinarians and horse owners:

    •  Non-steroidal anti-inflammatory drugs are used for muscle or hoof pain. They include firocoxib, phenylbutazone, flunixin and ketoprofen. Although effective for moderate pain reduction in horses, they are not effective with extreme pain and are often used with other drugs. High doses of medicine used in an extended period of time can produce significant side effects such as stomach ulcers, especially in foals.
    • Opioid analgesics have been the mainstay of pain relief in both human and veterinary medicine and include drugs such as morphine, fentanyl and tramadol. In non-horses, when used alone, they can produce excitement and should only be used to alleviate pain. Stasis of the gastrointestinal tract is another concern with them and why they are used sparingly for specific medical conditions. The one opioid approved for use in the horse is butorphanol; it is use for pain control or in combination with sedatives.
    •  Alpha 2 agonists such as xylazine and detomidine are used to produce sedation, anesthesia and to alleviate pain. They have also been used to relieve pain for epidural and joint injections. They are commonly used in combination with other injectable analgesics, such as butorphanol.
    • Local injectable analgesics such as lidocaine and carbocaine are injected into nerves or tissue to provide regional pain control for wound repair or into the testicle during castration. They are also commonly injected into joints to aid in the diagnosis of lameness or to control pain.
    • Ketamine has proven effective when provided at a low rate and constantly infused intravenously. It is especially effective, when combined with other pain medication, in controlling pain in horses suffering from severe burns or infected joints that require severe pain control over time.

There is a concerted effort to develop more effective pain-management drugs that can be given to the horse orally or transdermally and last longer.

Dr. Thomas R. Lenz is a trustee of the American Horse Council, is chairman of AQHA’s research committee and is a past president of the American Association of Equine Practitioners.