If I could carry only three drugs in my truck, one would be a non-steroidal anti-inflammatory. That’s because injured or ill horses frequently show signs of inflammation---swelling, pain and fever. And, although inflammation is needed for healing, when it gets out of hand it becomes a serious issue.
NSAIDs act by inhibiting the enzymes that are precursors to inflammation and bringing under control the signs associated with illness, injury and chronic diseases. Treating inflammation is one of the most important things veterinarians do and---like most of my colleagues---I end up reaching for NSAIDs often in the course of my working day.
But we don’t prescribe without thinking things through first. NSAIDs can make the horse more comfortable and reduce inflammation, but they can also have some serious side effects, and I must weigh these risks when making a prescription. In fact, in some situations I may choose not to use an NSAID.
When I’ve decided a horse will benefit from an NSAID, I have many options. To make the appropriate choice, I’ll weigh many variables, like the type of injury, the horse’s previous experiences with NSAIDs, how long he’s likely to need to be medicated and a host of other factors. Then, based on what’s known about the pharmacology of each drug and my own experiences, I’ll prescribe the NSAID I think is likely to be the most suitable for the job at hand. I often explain to the horse’s owner my reasons so they’ll understand how I arrived at that decision and appreciate the factors that went into it.
To help illustrate how this process might play out, here are a few examples of horses---the very sorts I often see in my practice---with conditions or injuries that could be treated with an NSAID. I’ll reveal which medication I’d most likely choose as part of a treatment plan and why.
Bump on the leg
A misjudged distance in a green hunter class sent rails flying. Cleo, the young mare, took a good whack to her knee from a pole and limped off the course in obvious pain. Thankfully, a radiograph showed no fractures or other serious damage, but the joint swelled from the trauma, indicating an inflamed joint, or synovitis. Cleo would need several weeks off to recover, and she’d benefit from an NSAID to help with that process. Which one should we choose?
I recommend to the owner that we limit Cleo’s exercise until the joint is better, apply ice and administer my anti-inflammatory of choice for joint issues, phenylbutazone (“bute”), the go-to NSAID for acute joint injuries. Bute is one of the most potent NSAIDs when it comes to pain relief as well as one of the most cost-effective. Although horse owners often use bute to treat the “limp,” it isn’t given just for pain control. Phenylbutazone, like other NSAIDs, also facilitates the healing process by controlling inflammation.
Inflammation is a dual-edged sword: It’s a call to arms for healing forces that speeds the cleanup and repair process of damaged tissues. But too much inflammation has a destructive effect, slowing the very healing it’s supposed to be aiding and in some cases further damaging the tissues, even permanently. In the joint, inflammation creates continued destruction, so we need to control it while making the horse more comfortable. NSAIDs do both of these jobs by blocking the production of a family of chemicals known as prostaglandins that cause inflammation. The most important of these are the cyclooxygenase enzymes known as COX-1 and COX-2. Phenylbutazone, like most traditional NSAIDs, blocks both.
Because Cleo weighs 1,000 pounds, I’ll start her at 1.5 grams of bute twice a day (I never give more than two grams twice a day because of the risk of side effects). Studies have shown that higher levels of bute increase the risk of side effects significantly but do not increase any of its benefits. In addition to the toxicity associated with large or prolonged doses, it’s possible for a horse to be especially sensitive to NSAIDs, and if so, we might see side effects after just one or two conservative doses. I explain to Cleo’s owners that they must monitor her for signs of loss of appetite, loosening manure or colic, especially because the mare is a recent purchase and we do not know if she has a sensitivity to bute.
We hope to see an improvement in acute injuries treated with phenylbutazone within three days, at which point I’ll back the dosage down to one gram twice a day or even once a day if the horse is still comfortable at that level. The goal is to have the horse off of bute within 10 days, at which point the injury is healed or healed enough that the body can finish the process without the support of medication.
Jinx had always had a sensitive stomach. He had his first bout with gastric ulcers as a weanling, when the stress of leaving his dam combined with dietary changes triggered the painful erosion of his stomach lining. Now, as a mature event horse, he is still prone to ulcers in the height of competition season, and anytime he is given phenylbutazone he gets irritable. He colicked last year after a week of bute and has not been given that medication since. As an active athlete, however, he could occasionally benefit from an anti-inflammatory medication.
The best option for Jinx is probably firocoxib. Sold under the name Equioxx, firocoxib is a COX-2 inhibitor, meaning it targets only certain classes of cyclooxygenase enzymes---those associated with harmful inflammation ---while typically preserving those that have a protective function. This means that firocoxib can often be given to horses who are sensitive to conventional NSAIDs with much less risk of adverse side effects, particularly right dorsal colitis, a serious condition.
If a horse under my care has a history of bad reactions to NSAIDs that inhibit both COX-1 and COX-2, I will try to use firocoxib as an alternative whenever possible. The problem is that this medication---available only in paste form---can quickly get expensive. For owners who can manage it financially, it’s a great alternative, though.
The standard dose of Equioxx is .1 mg per kilogram of body weight once daily for up to 14 days. I try to not keep horses on it much longer than 10 days. And while there is a much lower risk of side effects, they can occur. That’s because even though almost all the COX-2 prostaglandins we are inhibiting are inflammatory, some have anti- inflammatory properties, and an individual’s immune response can vary.
I also instruct the owner that we may have to give a higher dose the first time to get the blood levels to where they need to be. Jinx tolerates it well, and the owner is relieved that we have another medication we can use to help control inflammation, because he is a hard-working horse.
Rebel lived up to his name in his younger years, but now, at age 20, the gelding is one of the most reliable and requested lesson horses at the barn. He has never had a significant musculo-skeletal injury, but years of use have led to arthritis in several of his joints. He’s noticeably stiff after he walks out of his stall, and his gait doesn’t have the easy-going swing it used to. He’s never had an adverse reaction to NSAIDs and could now use a regular dose to keep him comfortable for the coming years.
Horses like Rebel are great candidates for a daily dose of phenylbutazone. It’s effective and inexpensive for long-term use, and I like both of those things. With the idea of a daily NSAID comes the worry about potential side effects, and while it’s good to be aware of that possibility, it’s also important to know that there are horses who do just fine on such a regimen. Not only can it keep them comfortable in the moment, but it tamps down the inflammation that’s at the root of arthritis, slowing the destructive processes. For all these reasons, if an older horse has no history of gastric ulcers, kidney trouble or adverse reactions to NSAIDs, I see no problem trying them on a daily dose of bute.
I’d typically start a horse like Rebel (1,000 pounds) on half a gram of bute once a day, and if that doesn’t seem to help, I’ll go up to one gram. It’s a dose I’m very comfortable giving, even on a daily basis. Nonetheless, we will still keep a close eye out for loss of appetite, colic, irritability, softer manure or other signs of sensitivity.
If we are concerned, I can have his blood analyzed for the total protein levels; if it’s lowered, that’s a sign of trouble, and we can take the horse off of bute and devise a different strategy.
Mild tummy trouble
The morning grain still untouched at noon was the first indication that something was wrong with Penny. As her owner took a closer look at the 9-year-old mare, the other signs of colic soon became obvious: She was sweating slightly, restless and preoccupied. The veterinarian soon arrived, and after a full diagnostic workup confirmed that the mare was most likely suffering from minor gut pain. A small dose of a particular NSAID might be enough to set her right.
While bute is the go-to NSAID for joint pain, flunixin meglumine---sold as Banamine---is our pharmaceutical first responder for colic. Flunixin can help relieve pain while reducing inflammation in the gut mucosa, which makes it reliably effective for colic. In mild cases of colic, this one-two punch is often enough to resolve the situation. Most of us have known a horse who will look a bit colicky, then perk up in about 45 minutes after a single dose of flunixin. It’s also the reason that many owners, under the guidance of a veterinarian, will keep a tube on hand at the farm.
The dosage for Banamine paste is .5 milligrams per pound, which works out to about three doses per syringe. Banamine is also available as an intramuscular or intravenous injection. I generally advise a client to avoid giving it in the muscle because it has been associated with an increased risk of clostridial0 infections, even when delivered under clean conditions. Intravenous injections must be administered only by a licensed veterinarian or technician due to the risk of a potentially fatal intracarotid injection.
There is a disadvantage to treating colic with Banamine: It can mask pain so well that a potentially serious case may go undiagnosed. Pain is a significant indicator of the severity of colic and the need for surgery. Some owners give Banamine before a horse can be assessed by a veterinarian, but the true extent of the problem may go undetected for hours, with tragic results. Owners must exercise caution when giving a medication without the direction of a veterinarian, and that applies doubly for a horse with colic.
Banjo came up lame after a muddy spring trail ride. The puffy, tender swelling on the back of his cannon bone suggested a strained tendon, which an ultrasound confirmed. The large pony was going to need treatment, rest and careful rehabilitation to ensure the tendon healed completely and avoid the risk of reinjury. In addition to cold hosing and confinement in a small paddock, one particular NSAID could be helpful.
Banamine isn’t just for colic. Because it targets soft tissue with its anti-inflammatory action, it’s also a good choice for lameness caused by injuries to tendons, muscles or ligaments. Again, the goal is twofold: control the horse’s pain, but also keep in check the inflammatory processes that can impede healing.
I’ll generally have the owner deliver dosages via paste. I wanted to reevaluate Banjo’s leg in a week, so to prevent Banamine from masking any pain we administered it for only five days. After an ultrasound we determined he injured his tendon significantly. He would need a lot of time off and controlled rehabilitation. Trail riding would have to wait until next spring.
Beyond athletic injuries, I’ll often reach for Banamine in other cases of soft-tissue trauma. For instance, after I’ve sutured a large wound, I might give the horse an injection of Banamine and have the owner give a few doses of paste over the coming days.
I don’t like to leave a horse on Banamine for more than five days. Not only are there risks of side effects, but it can get expensive. That said, I will prescribe a longer Banamine regimen to treat eye conditions, such as chronic uveitis. Controlling pain can be difficult in these cases, so if Banamine works, we’re going to want to keep using it. We will just watch the horse closely and perhaps protect against ulcers with a preventive treatment of UlcerGard.
One more note about Banamine: It’s my first choice when treating nursing mares for any type of inflammation, be it systemic, soft tissue or even bone-related. Pharmacological studies have shown that there’s less chance of this NSAID being passed to the foal through nursing than others. Since young foals can have ulcer problems to begin with, administering an NSAID to the mother can kick off some serious problems. When treating a nursing mare with Banamine, I’d follow the typical dosing guidelines but then watch both mare and foal for signs of adverse effects.
It took a few days to isolate the source of Georgie’s discomfort. The reining horse had been found standing stock-still in his pasture, head low and refusing to move. After ruling out laminitis, tying up and similarly scary diagnoses, his veterinarian traced the source of the pain to a cracked vertebral process halfway up the neck, likely damaged as he roughhoused with pasturemates. Radiographs showed that the bone was stable enough to heal on its own if Georgie’s movement was limited. We wanted to give him an anti-inflammatory but we faced a big problem. He refuses to eat medications in his feed, hates injections and likes to rear when you give him paste---not good for a neck injury! One specific NSAID could help minimize his discomfort.
If you know the exact anatomical location of a horse’s musculoskele-tal pain, a good choice may be diclofenac, which is a topical NSAID sold as Surpass. This medication is a cream that is rubbed directly onto the treat-- ment area. With this type of administration, the level of the medication in the bloodstream is low, which reduces the risk of adverse side effects. Of course, for all-over soreness or a systemic problem, diclofenac isn’t an option, but if you’ve pinpointed a specific location of trouble, it can be a great help.
Diclofenac can be used on any part of the body and is commonly used to treat arthritic joints. I’ve found that it works particularly well on neck pain, although I’m not exactly sure why. Perhaps it’s easy for owners to visualize where the cream needs to go, although I’ll still clip the target area as a guide and to facilitate penetration of the cream through the skin. The typical dose is a three-inch strip applied twice a day, although if the area is clipped closely, some owners can apply a bit less and still get the desired results (after talking to their veterinarian).
While the risk of side effects is markedly lower with diclofenac than it would be with a drug delivered systemically, some of the medication can still enter a horse’s bloodstream, so I urge owners to watch for signs of possible sensitivity or NSAID toxicity while using diclofenac. It isn’t likely to happen, but that doesn’t mean it can’t.
Joy came back from the show with more than ribbons. The pleasure mount had picked up a respiratory infection somewhere in her travels and was now a feverish, snotty messy. After evaluation and testing it was determined she had strangles, an infection of the upper respiratory tract. With quarantine protocols in place, the veterinarian gave Joy’s owner instructions on supportive nursing care, which included a daily NSAID.
NSAIDs aren’t just for treating injuries and arthritis. Systemic illnesses, such as respiratory infections, are also inflammatory processes. In this case, Banamine, our soft-tissue drug of choice, was used. It helped her feel better by inhibiting inflammation in the respiratory tract and by lowering the fever. But the benefits stretched beyond there: It also helped her breathe easier and because she felt better she was able to continue grazing and drink normally, which helped her avoid impaction colic. The judicious use of NSAIDs can help keep a small illness from snowballing into much larger problems.
I typically go with Banamine to treat a horse with a fever related to a systemic illness, delivering it as an injection myself and leaving the owner with a tube of paste for continued treatment. For a systemic illness, I typically try not to keep a horse on it for more than five days, at which point we’d expect him to be well on the road to recovery.
This article first appeared in EQUUS issue October 2014, #445.