The Latest on Pain Relief
The horse, as a prey animal, expresses pain in ways that are consistent with strong "flight" responses. In other words, horses don't want to show they are weak or disabled for instinctual fear they will be selected by predators. (Never mind the worst carnivore they have to encounter on an average day is the barn cat.)
For those familiar with horse behavior, some signs are telling. Severely painful conditions elicit the most profound reactions and behavior in horses. For example, a colicky horse might display distress by kicking at his abdomen, biting his flanks, rolling or thrashing on the ground, or frantically trying to escape the "monster" in his belly. Heart and respiratory rates elevate, and his body might be soaked in sweat.
Milder conditions provoke less dramatic responses, with behavior usually correlating to a horse's degree of pain. A horse with mild colic might seem apathetic to surrounding stimuli, while mild musculoskeletal pain might elicit restlessness, distraction, or performance below expectation. A stoic horse might express only subtle changes in mood, gait, or performance-- these individuals are a challenge to identify. Others are more demonstrative in their discomfort, displaying visible lameness or positional changes to relieve a throbbing limb. Lasting chronic painful conditions take their toll; a horse becomes depressed and dull, with associated weight loss from lessened interest in food.
By knowing your horse's normal behavior and reactions to routine situations, you often "sense" when something doesn't seem quite right; then you can apply a proactive approach to discern what the issue might be. A webcam is a relatively inexpensive tool that can be set up in the barn to monitor your horse's behavior patterns when he doesn't have someone viewing him from the stall door.
There is a tendency for horse owners to want to "help" horses by administering one of many pain-relieving drugs when they perceive a problem in their horses. It is sound advice to get your veterinarian involved early for any concern--this will help you avoid unwanted side effects from medications and avert progression of a problem.
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
In addition to the invaluable, time- honored use of cold therapy for pain relief, administration of NSAIDs has been a mainstay in pain control in the horse, so much so that we often take for granted the attendant complications they produce. Nonselective NSAIDs (phenylbutazone, flunixin meglumine, or ketoprofen) exert their effects through inhibition of cyclooxygenase-2 (COX-2) mediators of inflammation, but they also inhibit COX-1, which has beneficial "housekeeping" effects on the stomach, intestines, and kidneys.
Rebecca McConnico, DVM, PhD, Dipl. ACVIM, associate professor of Equine Medicine at Louisiana State University's veterinary school, has investigated adverse effects of NSAIDs. She reports, "Some horses cannot tolerate standard dosing and administration of phenylbutazone (Bute), for example. Harmful effects include stomach and large colon inflammation and ulceration, as well as renal damage and subsequent dysfunction. These signs are not always apparent to a horse owner or handler. A horse may display subtle signs of decreased appetite, weight loss, dull demeanor, or general unthriftiness, whereas more obvious side effects include teeth grinding, diarrhea, edema (fluid swelling) along the lower abdomen or thorax due to associated protein loss, and/or colic. Prolonged phenylbutazone treatment also may lead to poor performance related to these adverse GI effects."
Ironically, many pain-related problems we try to resolve through therapy might actually be created by therapy.
It is common for owners and veterinarians to reach for flunixin meglumine (Banamine) when a horse is showing colic signs. However, McConnico stresses, "If colic signs continue or worsen despite medical treatment (laxatives and oral and/or intravenous fluids), possible surgical intervention may be necessary. Flunixin may mask signs that would otherwise help us make these management decisions. In addition, flunixin can inhibit and even exacerbate intestinal damage by interfering with damaged gut's ability to heal."
Another commonly used--yet erroneous--strategy is for an owner to administer both Bute and Banamine at the same time for musculoskeletal problems. McConnico remarks, "Doubling up these two nonselective NSAIDs is not recommended. There is compelling evidence that this increases the risk of sustaining serious harmful effects to the horse's gastrointestinal tract and kidneys at a faster rate than using these drugs alone. Usually, waiting 24 hours from the use of one drug before starting the other is adequate, as long as no other signs of adverse side effects are present."
McConnico recommends: "Nonselective NSAIDs are best administered with the least amount of drug to achieve pain relief. This is sometimes difficult to determine due to each individual horse's drug response. NSAIDs are not 'one dose fits all' types of drugs--each horse should be evaluated on a case-by-case basis. If prolonged treatment is required, then patient monitoring is critical and should include a thorough physical examination and baseline blood work (total protein, albumin, BUN--blood urine nitrogen, creatinine, and complete blood count)."
She suggests that the COX-1-sparing drug firocoxib (Equioxx, manufactured by Merial) could be a safer alternative NSAID treatment option.
For joint problems related to osteoarthritis, a topical product is available (Surpass), which is a non-steroidal cream containing diclofenac. Craig Shoemaker, DVM, an equine professional services veterinarian for Boehringer Ingelheim Vetmedica Inc. (which markets Surpass, 1% diclofenac sodium) explains, "Liposomal delivery technology is the key to Surpass. Liposomes are microscopic spheres resembling biological membranes. This technology allows targeted treatment of inflammation using smaller drug concentrations than standard systemic treatments. The result is less systemic uptake and smaller drug concentrations to be metabolized and excreted."
Topical diclofenac is considered a safer option over conventional oral NSAIDs because it only achieves very low levels in the horse's systemic blood circulation and, thus, is less apt to adversely affect GI or renal function.
The veterinarian or horse owner rubs a 5-inch-long ribbon of cream gently over an injured area twice daily for up to 10 days. Gloves are recommended for applying Surpass as it can be absorbed through human skin; incidental contact poses little concern and you can wash it away easily with soapy water. Shoemaker remarks, "Most horses show improvement by Day 2 or 3 (of treatment), with response dependent on disease severity. Certainly, more acute and less severe cases respond better than chronic or advanced cases."
In a Colorado State University study comparing Surpass to phenylbutazone, Shoemaker reports, "Both Surpass and phenylbutazone significantly improved lameness scores in horses with experimentally induced osteoarthritis. Surpass produced significant disease-modification properties based on erosion scores and staining characteristics of articular cartilage and on magnetic resonance imaging (MRI) findings."
Surpass is the first NSAID shown to have both symptom- and disease- modifying properties, whereas systemic NSAIDs, such as phenylbutazone, only address symptoms.
A University of Florida study identified only low concentrations of diclofenac in urine and serum following fetlock treatment with fourfold the normal recommended amount. The United States Equestrian Federation (USEF) and American Quarter Horse Association (AQHA) permit its use in competition horses, provided the caretaker discontinues use 12 hours prior to the horse competing and uses the product according to label instructions. Shoemaker stresses, "Specific guidelines for use in other disciplines, including racing, vary and should be understood prior to using Surpass." This medication has a practical role during training or for horses not slated soon for competition.
Other potential uses for Surpass are being investigated, including its use on the cephalic vein (runs along the inner forearm of the horse) during regional limb perfusion for septic limb conditions that elicit marked pain.
Laurie Goodrich, DVM, MS, PhD, Dipl. ACVS, associate professor of Equine Surgery and Lameness at Colorado State University's veterinary teaching hospital, is familiar with painful conditions of horses. According to Goodrich, pain related to hind limb injury has potential to create medical complications, such as impaction colic, gastric ulceration, colitis, or supporting limb laminitis. She explains, "Pain usually starts locally, but becomes generalized, which leads to decreased GI function and motility, then an impaction. Physiological stress from ongoing, uncontrolled pain also commonly leads to gastric ulcers or colitis."
Goodrich notes that initial pain control for orthopedic conditions includes oral NSAIDs. "However," she says, "If this approach is not adequate to produce comfort or if related adverse effects of NSAIDs are of concern, we use epidural analgesia for acute or chronic conditions causing hind limb pain. Examples include severe wounds, joint sepsis, stabilized fractures, or significant soft tissue injury."
Goodrich maintains that a veterinarian can administer an epidural anesthesia with sedatives and/or morphine in the field if he or she is comfortable with the technique.
She continues, "Epidural analgesia is most effective when you intercede early. Once pain becomes chronic, epidural analgesia may not last as long due to a 'wind-up' response--the body synthesizes increased neurotransmitters that increase pain while decreasing the ability to inhibit pain. The objective is to minimize 'wind-up' before it begins."
Goodrich stresses that another goal of epidural analgesia is to enable the hind limbs to bear equal weight. Supporting limb laminitis often results in cases of leg injury because the horse bears more weight than usual on the uninjured opposite limb due to unrelenting pain in the injured leg. She reminds us, "An equine surgeon can perform the most elegant fracture repair, but if it doesn't result in even weight bearing, support limb laminitis may cause the demise of the horse, as occurred with Barbaro."
Recent Developments in Pain Control
Goodrich is excited about other new and effective pain-relieving drugs and techniques that are becoming available. She says, "We have used various constant intravenous infusions of low-dose ketamine and/or butorphanol with some success. Fentanyl transdermal patches, applied over the saphenous vein (runs down the inside of the hind leg) or cephalic vein, have been used successfully to deliver narcotic to the horse's system. There is also a novel system of implanting a subcutaneous catheter in proximity to nerves that supply the lower limb to maintain continuous infusion of anesthetic for a regional nerve block."
These varied strategies present humane options for better equine pain control following serious injury or for managing painful surgical conditions.
Ed Boldt, DVM, owner of Performance Horse Complementary Medicine Services, uses acupuncture, chiropractic, and herbal therapy to manage pain. Boldt stresses that in his experience, "Complementary therapies for pain relief are beneficial to the horse. However, they must be utilized by a qualified veterinarian so a proper diagnosis is achieved and appropriate use of the therapies employed."
Any veterinarian should look at the whole horse, not just the current cause of pain. Boldt said, for example, hock pain is more effectively resolved through recognition of concurrent pelvic or back issues that elicit compensatory gait changes.
Boldt cautions, "I do not recommend acupuncture following an acute injury until the full extent of the injury is known--a fracture or tendon or ligament tear must be identified."
While a single treatment might achieve pain relief, especially with recent problems, Boldt says, "A long-standing problem often requires multiple treatments; the number of treatments is predicated upon a horse's response." Boldt finds that electroacupuncture quickly "sedates" an area to achieve a more prolonged effect.
For colic pain, he has found acupuncture most useful for gas colic, noting, however, "Close monitoring is required as with the use of any other form of pain relief." In addition to using acupuncture for managing eye or joint pain, Boldt includes acupuncture as an adjunctive therapy to conventional medical treatment for heel pain or navicular disease and for generalized back pain related to overwork, "kissing" spines, and poor saddle fit.
When aiming to manage a horse's pain, it is helpful to evaluate his whole body to identify the location of pain, as well as underlying or inciting issues that you and your veterinarian should also address. Consider adverse side effects when using conventional non-steroidal anti-inflammatory therapy. Integrating other pain-relieving strategies can be essential to achieving success. Goodrich urges, "The thing to remember is pain control in horses (just like in people) may have variable results. What works for one may not work for another, so a multitude of approaches is invaluable."
About the Author
Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.
POLL: It's Derby Week!