Effect of Firocoxib and Flunixin Meglumine on Large Colon Mural Thickness of Healthy Horses.
Authors: Bishop Rebecca C, Wilkins Pamela A, Kemper Ann M, Stewart Ruth M, McCoy Annette M
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Firocoxib and Flunixin Meglumine Effects on Equine Colon Whilst COX-2 selective NSAIDs (coxibs) were developed to improve the safety profile of traditional non-selective anti-inflammatory drugs, their specific effects on equine colonic integrity remain poorly characterised. Bishop and colleagues conducted a crossover study in twelve healthy horses, each receiving a five-day course of either firocoxib (0.3 mg/kg loading dose, then 0.1 mg/kg daily) or flunixin meglumine (1.1 mg/kg twice daily), with six months between treatments to allow washout, measuring colon wall thickness ultrasonographically before and after each protocol. Firocoxib induced a substantial median increase in colon wall thickness of 5.8 mm compared to just 3 mm with flunixin (P = 0.003), with subjective colonic oedema observed in eleven of twelve horses treated with firocoxib versus only one horse receiving flunixin—findings that suggest a subclinical inflammatory response in the large colon despite the absence of clinical signs or significant serum chemistry changes. These results warrant reconsideration of firocoxib's perceived gastrointestinal safety advantage in equine practice and support regular ultrasonographic monitoring of colonic health when deploying any NSAID therapeutically, particularly in horses with pre-existing colic risk factors or those requiring extended analgesia.
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Practical Takeaways
- •Firocoxib, despite being a selective COX-2 inhibitor designed to reduce GI side effects, may pose a risk of subclinical colitis in horses and warrants careful consideration when selecting NSAIDs for pain management
- •Regular ultrasonographic monitoring of colon health should be considered when NSAIDs are used clinically, particularly with selective inhibitors, as routine serum chemistry may not detect colonic inflammation
- •Flunixin meglumine appears safer for colonic integrity than firocoxib in this study, though both drugs require judicious use and gastric protection with omeprazole
Key Findings
- •Firocoxib caused significant colon wall thickening (median 5.8 mm post-treatment, P < 0.001) whereas flunixin meglumine did not (P = 0.7)
- •Colonic edema was observed in 11/12 horses after firocoxib treatment versus only 1/12 horses after flunixin treatment
- •Colon wall thickness was significantly greater following firocoxib compared to flunixin (P = 0.003)
- •No clinically significant hematologic changes occurred with either drug, suggesting subclinical gastrointestinal effects may not be detected by routine blood work