There’s a reason why nonsteroidal anti-inflammatory drugs (NSAIDs) are found in horse barns across America. Phenylbutazone, flunixin meglumine and other frequently prescribed NSAIDs are well understood, easy on the wallet and effective. Indeed, rare is the horse owner who hasn’t administered NSAIDs, under a veterinarian’s supervision, to ease a horse’s aches, pains or digestive discomfort.
Yet as familiar and indispensable as NSAIDs are, questions can still arise about how best to use them and what their effects might be. Of course, an internet search will yield plenty of general information. But for practical guidance, as well as insights that only experience confers, it’s best to turn to experts—veterinarians and researchers—with direct experience treating horses with NSAIDs. Of course, you’ll want to consult your veterinarian regarding your own horse’s care. But read on for answers to common questions about NSAID use in managing equine injuries and diseases.
▶ Veterinarians often prescribe NSAIDs to reduce pain associated with injury or illness. How are NSAIDs different from painkillers?
Reducing inflammation can alleviate discomfort, but NSAIDs are not considered painkillers. “Often, inflammation is the underlying problem causing the pain,” explains Duncan Peters, DVM, DACVSMR. “But a painkiller has a different mechanism of action. It merely targets pain, rather than quieting down the whole process in which one symptom is pain.”
Opioids
Take, for example, one well-known class of painkillers: opioids. “These primarily act on the opioid receptors in the brain, diminishing the sensation of pain,” explains Mary Robinson, PhD, VMD, DACVCP. “Morphine is a classic example. It’s a drug that has been used for thousands of years.” A less potent analgesic option is acetaminophen, which is available over the counter.
Local blocking agents
Local blocking agents are another type of painkillers commonly used in horses. “These drugs block transmission of signals from the site of the pain to the brain,” says Robinson. “An example would be a nerve blocking agent that a veterinarian injects into a horse’s leg to try to figure out where the horse is hurting. Going up the leg and blocking nerves in different places allows veterinarians to see how blocking different pathways affects lameness.”
NSAIDS
By contrast, Robinson says, NSAIDs are administered to manage the body’s inflammatory processes, which contribute to healing in cases of both injury and some illnesses. NSAIDs primarily inhibit enzymes called COX (Cyclooxygenases) that facilitate production of prostaglandins. Hormone-like substances involved in a variety of body processes, prostaglandins play a significant role in promoting inflammation and signaling pain.
So how do veterinarians decide which type of medication to prescribe for an injured or ill horse? “There are times it is better to use NSAIDs and other times it’s better to use a painkiller,” Robinson says. “Horses tend to respond to opioids with excitation. Even though the opioid is suppressing their pain, horses may become excited and unmanageable. This is why we generally do not reach for an opioid to alleviate pain in horses, at least not on the farm. Sometimes in the hospital we use opioids locally.”
In addition, some conditions in horses respond best to a two-pronged approach, using both painkillers and NSAIDs. For a horse with laminitis, “ … we may want to block the pain, to break that cycle and give some relief,” says Peters. “But if we don’t deal with the underlying inflammation, we will be right back in the same spot fairly quickly.”
▶ Inflammation is part of the body’s healing process. Given that NSAIDs work to suppress inflammation, can administering them inadvertently delay healing?
Inflammation is a protective reaction to irritation, injury or infection. So, it’s natural to worry that introducing an agent that interferes with the inflammatory response might slow healing. “The jury is still out on whether [administration of NSAIDs] is beneficial or harmful in many situations,” Robinson says.
What is clear, though, is that the body often produces too much inflammation in response to an injury. And that’s where NSAIDs come in. “Often NSAIDs are beneficial because the body tends to overreact to the problem (with too much inflammation),” Peters says. “What we are trying to do by giving NSAIDs is modulate that inflammatory response. We don’t want more inflammation than is needed to assist healing.”
Too much inflammation
Excessive inflammation not only increases discomfort but slows the body’s repair efforts. “Swelling that continues for a long period of time can create compression problems. It can also inhibit blood flow to that area,” Peters says. “If we can minimize some of that inflammation, we allow the body to better use its own processes, to get back to normal.”
This is especially true for wounds and other injuries for which antibiotics are part of the treatment. “Reducing some of the swelling enables the antibiotic to get into that area better,” says Peters. “It helps the whole healing process.”
Finally, some veterinarians recommend administering NSAIDs prior to surgery to reduce the amount of inflammation that will occur later. “If a horse has a broken leg, I will give him an anti-inflammatory. This will help him feel better and reduce swelling and inflammation around the area where I will be doing surgery,” says Ryan Carpenter, DVM, of the Equine Medical Center in Cypress, California. “This makes the horse a better candidate for surgery and makes him comfortable until I get him to surgery. Then, when I do the procedure and have stabilized the fracture with screws or plates, having NSAIDs in his system will result in better comfort for the horse.”
▶ In people and in horses, the link between non-selective NSAIDs and gastrointestinal problems is well known. How long can NSAIDs be safely administered?
The side effects of NSAIDs in horses are well documented. High doses and extended treatment regimens increase susceptibility to gastric ulcers, gastro-intestinal bleeding and kidney problems. Nonetheless, says Peters, “there is no set rule of thumb for how long a treatment regimen can be. Each horse is a little different. The veterinarian and owner must determine what is a safe level and length of time for treating that particular horse.”
Still, many equestrian organizations place limitations on NSAID use in competition horses. “For instance, the USEF has rules addressing the use of NSAIDs,” Peters points out. “Most NSAIDs are given for five days in a row and then two days off, and then five days in a row and two days off, to minimize the negative side effects of long-term use,” he notes. “Equioxx (firocoxib), however, is allowed to be given for 10 days in a row and then a few days off.” (For more about COX-2 selective NSAIDs, see sidebar, “COX-1 and COX-2,” page 18.)
Whether subject to such rules or not, most people try to use NSAIDs for as short a period and as low a dose as needed to keep a horse comfortable and facilitate healing. Some experimentation may be necessary to find the right balance, says Peters. “If you try to go longer periods and/or higher dose, you will probably see some of the unwanted conditions. If you go longer with a lower dose, you may get the benefits you want but be able to stay away from some of those side effects.”
Starting with a diagnosis
The key is starting with a specific diagnosis, selecting the right medication and anticipating, if possible, how the horse’s body is likely to respond. Just like people, some horses are more or less sensitive to specific medications. “I’ve had horses on one gram of bute for 45 to 60 days in a row and not had any problems with side effects yet having the benefits of being more comfortable, such as an older horse with arthritis,” Peters says.
For her part, Robinson says, “I don’t like to give non-selective NSAIDs [which inhibit both COX-1 and COX-2] for more than a week. But this is just my general rule of thumb. It’s not scientifically proven. There is a study that one of my predecessors did here at Penn that showed that by the time they had given bute twice a day for five to seven days at a fairly high dose, they were starting to see some side effects like right dorsal colitis. Thus, I get nervous giving it for more than a week.”
Conditions that persist for a week or more without improvement merit further investigation, she says. “If whatever is causing the inflammation is lasting for more than a week, you probably need to look a bit harder at the problem,” Robinson explains. “NSAIDs are not meant for long-term administration, at least not with the doses we use and the way we typically use them.”
COX-2 inhibitors
As for the COX-2 inhibiting NSAID firocoxib (brand name Equioxx), Peters notes that one of its benefits is fewer side effects, even when it is part of a longer regimen. “It’s not uncommon for people to use the prescribed dose of Equioxx for 30 to 45 days,” he says. “Most veterinarians probably prescribe something like ‘Use this for 30 days and then take the horse off it for three to five days. Then use it again for another month.’ It helps to give the horse a break for a while.”
Robinson agrees that longer term administration of firocoxib carries fewer risks. Nonetheless, “when you are balancing the risks versus benefits, you don’t want the horse to be in pain. But if you are dealing with a chronic condition, an NSAID may not be the best choice,” she says. “Work with your veterinarian to determine the best course of treatment. Some people have experimented with other medications, such as gabapentin, for more chronic pain. It seems to have fewer risks.”
▶ Both corticosteroids and NSAIDs have anti-inflammatory effects. How do veterinarians decide which to prescribe?
Key differences between NSAIDs and steroids make one or the other a better choice in particular treatment scenarios.
Because steroids act on multiple pathways within the body, they are usually reserved for short-term treatments to address allergic reactions, severe pain and other acute problems. “Steroids are generally used if you need to knock down the inflammation immediately,” Peters says. “Skin problems like hives, bee stings, insect and spider bites are a good example. If the horse is reacting adversely, one treatment with a steroid can be very helpful to halt that process.”
But the potential side effects of steroids are wide ranging. In addition to suppressing the immune system, steroid administration can precipitate imbalances that increase susceptibility to laminitis, digestive problems and hormonal issues.
“Steroids are produced in the body by the adrenal gland. They are critical for regulating all types of body processes. There are corticosteroid receptors in every cell in the body,” Robinson explains. “That means that even one or two doses of a corticosteroid can upset the body’s natural balance. If you give a steroid—even into the joint—it suppresses the body’s production of hydrocortisone, which is the naturally produced corticosteroid.”
The significance of these effects depends on the dose and the drug. But they may last for several days. “We did a study here at Penn, looking at Triamcinolone, and found that an intra-articular injection of a typical dose into the joint will depress the naturally produced hydrocortisone for up to six days after the injection,” she says.
When NSAIDs work best
By comparison, NSAIDs provide more targeted action. “Most of NSAIDs work by breaking the cycle of inflammation…there is some variation, depending on which NSAID you use, but basically the mechanism is to block the inflammatory cascade that occurs at different points of that cycle,” Peters says. “Some are more effective because they are at the higher end of where they block it, and some are lower down and more specific in what they target and block.”
Chronic conditions like arthritis may call for longer-term use of NSAIDs, albeit with precautions and careful monitoring. “Bute and Banamine are both commonly used. But they may have some adverse effects on the GI tract in horses that tend to be stressed or traveling, or older horses. We may also see some toxicity problems in the kidneys, etc. In these situations, we may want to use a different NSAID like firocoxib,” Peters says.
In general, he says, “the advantage of using NSAIDs rather that steroids is that you can use the NSAID for a longer period of time.”
▶ It’s customary to give horses with orthopedic problems phenylbutazone and those with digestive pain flunixin meglumine. Why are some NSAIDs more suitable for addressing certain types of inflammation than others?
The short answer is that they are not. True, most veterinarians have favorite go-to NSAIDs for specific problems. And in many of these cases, a medication is preferred because of where it works on the inflammatory cycle. “There are different receptor sites for inflammation associated with muscle/skeletal concerns versus soft tissues or abdominal concerns, respiratory problems or eye concerns,” says Peters.
But, he adds, “these receptor sites are not so specific that we only use one NSAID for a condition, even though we do have a preference of certain drugs for some conditions. This is why we use Banamine for colic, bute for musculoskeletal problems, and Equioxx or firocoxib for situations where we want fewer side effects on the GI tract.”
Practical experience
In other words, NSAID selections tend to be grounded in practical experience more than scientific studies. “Most horse owners have probably heard that it’s best to use flunixin for colic and bute for musculoskeletal problems,” Robinson says. “This is anecdotal. There is actually not good data to support this. It is based on practitioners’ experiences and clinical impressions. There is no study I can point to that says this is why flunixin is better for colic or bute is better for other things.”
In his California practice, Carpenter sees this in action. “Our clinical impression is that some NSAIDs are more suitable than others for certain problems. Equine practitioners will tell you that Banamine is better for eye pain and GI tract pain, while bute is better for orthopedic pain—joints and muscles,” says Carpenter. “From a purely scientific medical perspective, it doesn’t make a lot of sense because these drugs are very similar, and they act in very similar manner. But from a clinical perspective we feel there are differences. That’s where there is always a leap between the textbook, research literature and the doctor’s clinical impression when looking at the patient face to face.”
Real-life experiences are the best gauge to use, says Carpenter. “Research only takes us so far. Our boots on the ground and hands on the patient takes us to the next level. Although we rely heavily on research, we can’t ignore the patient just because the research tells us something. We have to actually evaluate the patient’s response to our treatment and make adjustments accordingly—case by case.”
▶ Veterinarians sometimes administer antibiotics prior to surgery to head off infection. Can NSAIDs given before a horse show, competition or another type of exertion help to manage the inflammatory response?
Experts have differing opinions on the prophylactic use of NSAIDs.
“There are pros and cons to pre-loading with NSAIDs. If you know an older horse will be working especially hard, you may want to give him an NSAID because it will decrease some of the inflammation before it gets a chance to really take off,” says Peters. “On the other hand, if a horse is taken on a long trail ride, he may become a little dehydrated. Then having an NSAID in his system could lead to other problems with the GI tract or kidneys.”
Prevention vs. treatment
The way Carpenter views it, “it’s easier to prevent inflammation and pain than it is to treat it.” A prime example is a horse scheduled to undergo throat surgery. “The horse going in is completely normal, happy and in no pain. But then I am going to make an incision, spread the muscles, disrupt the tissues and do some dissection. This will cause some local swelling and trauma,” Carpenter says. “If I simply deal with this after it happens, I will have a harder time maintaining patient comfort than if I treat that horse beforehand and for a few days afterward. The last thing you want after throat surgery is a horse that is so sore that he won’t eat or drink. Then he might become dehydrated, and the manure will become too firm. You can create complications by not providing effective pain management in the beginning. I’m going to give an NSAID before the procedure.”
The same thing might apply to a horse ridden only occasionally. “If you are a weekend warrior and your horse stands in a stall the rest of the time, it would be like you sitting on the couch eating potato chips all week and then, on Saturday, trying to run three miles,” Carpenter says. “You would be pretty sore afterward. You can prevent some of the soreness by being more proactive.”
What the research says
Yet, Robinson points to a study in humans that investigated the benefits of giving NSAIDs before or after exercise. “The people who received the NSAID before exercise still developed inflammation and needed the medication again afterward.” While conceding that “there is not much good data on this question,” Robinson prefers to administer NSAIDs after exertion or surgery.
That said, Robinson emphasizes that she would not wait for inflammation to develop before administering NSAIDs. “I would do the exercise or event and then give the horse a dose that evening, before he is really stiff and sore,” she says. “In my opinion, it’s best to give medication when you are doing all the other after-event things like cooling them out and icing the legs.”
In the past couple of decades, research has yielded many new and improved methods for helping horses heal. Will protein rich plasma (PRP), interleukin-1 Receptor Antagonist Protein (IRAP) or other innovative therapies one day displace NSAIDs on the roster of equine veterinary treatments? Not likely, say experts.
Peters predicts that NSAIDs will continue to be vital in managing equine health, “partly because they are effective and partly because they are less expensive than the biologics, and more convenient.”
“As with aspirin for people, it’s a lot cheaper than having your knee injected with PRP,” he says.
Robinson agrees, noting that it’s hard to beat NSAIDs in terms of availability, ease of administration and relative safety. “There will always be a role for NSAIDs in managing equine health,” she says.
