THE DOWNSIDES OF NSAIDS

For all the good they can do, nonsteroidal antiinflammatory drugs have some potentially serious side effects.

These side effects stem from the way most NSAIDs work: by blocking the cyclooxygenase (COX) enzyme pathway. This pathway, which can be divided into subsets known as COX-1 and COX-2, is necessary for the production of prostaglandins, which create inflammation and pain. However, the COX pathway, and particularly COX 1, also has some positive effects, such as protecting the stomach and intestinal mucosa. So by blocking the COX enzyme pathway, we inhibit pain and inflammation but also negate their protective effects. It’s a pharmaceutical tradeoff.

That tradeoff means that we can see degradation of the mucosal lining, one of the more common side effects of NSAIDs. These include gastric ulcers and potentially right dorsal colitis, a painful colic that is very difficult to manage.

Inhibiting COX can also affect clotting ability and compromise blood supply to organs, particularly the kidneys. Horses on high doses or long courses of NSAIDs are more likely to develop these side effects, but sensitive horses can develop problems after only a single dose.

One way to minimize the risk of side effects is to use firocoxib, the only systemically administered equine-selective NSAID that targets COX-2 specifically, leaving the protective effects of COX-1 in place. But this medication is substantially more expensive than other NSAIDs, limiting its usefulness in some cases.

The best approach to managing side effects of NSAIDs in horses is to stick to the lowest dose possible and monitor the horse carefully for signs of adverse effects. These include looking colicky, going off his feed, looser stools or general agitation.

By blocking the COX enzyme pathway, we inhibit pain and inflammation but also negate the protective effects. It’s a

pharmaceutical tradeoff.

A blood test can reveal whether the signs are related to NSAID toxicity. If a horse develops NSAID toxicity, the safest course of action is to stop the drug entirely and never use that specific medication again.