We’ve reported before about increased risk of side effects when mixing nonsteroidal anti-inflammatory medications like phenylbutazone and flunixin. This practice is still being continued in some circles, on the belief that the combinations are much more effective than either drug alone.
A study just published in the American Journal of Veterinary Research, from the veterinary school at the University of Missouri, looked at single or combined drug treatments in 29 horses with naturally occurring front or hind leg lameness.
In 24 hours, there was more improvement after the combination than with phenylbutazone alone, but even the combination was not successful in completely eliminating lameness. Five horses did not change at all. One of the horses in the combination group died of a severe acute colitis, which is one of the side effects of phenylbutazone reported before to increase with combination therapy. In the 2006 study, 1 of 13 horses developed severe colitis and had to be euthanized. The other 12 also showed severe gastric ulceration and/or evidence of loss of protein into their bowel.
Bottom line: We agree that a potential small increase in ability to mask lameness, if any, does not come close to being worth the risk of serious complications when combinations of NSAIDs are used. Drugs in this class should be used responsibly, only for short periods (usually no more than 5 days) and at proper dosages based on accurate body weights.