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
Studies have shown that higher levels of bute increase the risk of side effects significantly but do not increase any 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.