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Veterinary medicine and science2026; 12(4); e71061; doi: 10.1002/vms3.71061

Gastroscopic Evaluation of Gastric Mucosa in Horses Treated With Flunixin Meglumine or High-Dose Firocoxib: A Descriptive Pilot Study.

Abstract: Equine Gastric Ulcer Syndrome (EGUS) is common in horses, and nonsteroidal anti-inflammatory drugs (NSAIDs) are a known risk factor for gastrointestinal ulceration. Although COX-2 selective NSAIDs such as firocoxib theoretically offer a better safety profile, endoscopic evidence for their mucosal safety at high off-label doses is lacking. Objective: To compare the effects of label-dose flunixin meglumine and high-dose firocoxib on the gastric mucosa of a small selected group of horses using serial gastroscopy and histopathology in a descriptive pilot study. Methods: Twenty mixed-breed horses were allocated non-randomly to control (n = 10), flunixin meglumine (1.1 mg/kg IM, n = 5), or firocoxib (1.0 mg/kg PO, n = 5) groups, treated once daily for 5 days. Gastroscopic evaluation and histopathological analysis were performed before (Day 1) and after treatment (Day 6). Results: No glandular disease was observed. Low prevalence of pre-existing squamous lesions was found in all groups without progression after treatment. Histopathological scores revealed baseline incomparability, with marked cellular infiltrate present only in the flunixin group at Day 1 (60%). Within-group analyses showed no significant changes between time points (p > 0.05). The use of NSAIDs effectively resolved lameness. Conclusions: In this small descriptive pilot study, limited by non-randomised allocation and small sample size, the study found no detectable short-term gastric mucosal injury associated with high-dose firocoxib within the limits of this study. Due to the non-randomised design, no causal conclusions can be drawn. These hypothesis-generating findings require confirmation in adequately powered randomised trials.
© 2026 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.
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Publication Date: 2026-07-08 PubMed ID: 42418297DOI: 10.1002/vms3.71061Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This pilot study investigated the effects of two types of nonsteroidal anti-inflammatory drugs (NSAIDs)—flunixin meglumine and high-dose firocoxib—on the stomach lining of horses, using gastroscopic exams and tissue analysis.
  • The research aimed to see if high-dose firocoxib, a COX-2 selective NSAID, caused less gastric damage compared to the commonly used flunixin meglumine.

Background

  • Equine Gastric Ulcer Syndrome (EGUS) is a frequent condition in horses, involving lesions in the stomach lining.
  • NSAIDs, often used to reduce pain and inflammation, are known risk factors for causing ulcers and other gastrointestinal problems.
  • Traditional NSAIDs like flunixin meglumine inhibit both COX-1 and COX-2 enzymes, which can contribute to gastric damage.
  • COX-2 selective NSAIDs such as firocoxib ideally spare the COX-1 enzyme, potentially reducing gastrointestinal side effects.
  • Despite theoretical safety advantages, there is limited direct evidence from endoscopy about the effects of high doses of firocoxib on the horse’s gastric mucosa.

Study Objective

  • To compare the effects of label-dose flunixin meglumine and a high off-label dose of firocoxib on the gastric mucosa of horses.
  • Utilized serial gastroscopic examinations and histopathological tissue analyses to assess mucosal condition before and after treatment.

Methods

  • Twenty mixed-breed horses were assigned to three groups:
    • Control group: 10 horses receiving no NSAID treatment.
    • Flunixin meglumine group: 5 horses given 1.1 mg/kg intramuscularly once daily for 5 days.
    • Firocoxib group: 5 horses given 1.0 mg/kg orally once daily for 5 days (high-dose, off-label usage).
  • Gastroscopic evaluations (visual inspection using an endoscope) and histopathological (microscopic tissue) analyses were performed before (Day 1) and after treatment (Day 6).
  • Lameness was monitored to confirm NSAID effectiveness in pain relief.
  • Note the allocation was non-randomized, which is an important limitation affecting causal conclusions.

Results

  • No glandular stomach lesions were observed in any of the groups before or after treatment.
  • Low prevalence of pre-existing squamous (upper stomach lining) lesions was detected in all groups, but these lesions did not worsen following treatment.
  • Histopathological analysis showed differences at baseline:
    • The flunixin group showed a marked cellular infiltrate in 60% of horses at the start, indicating some pre-existing inflammation.
    • No significant changes in cellular infiltration or other markers were observed after treatment in any group, including the firocoxib group.
  • Within-group comparisons (before vs. after treatment) revealed no statistically significant changes in gastric mucosa condition (p > 0.05), suggesting no detectable short-term mucosal injury from either NSAID under the conditions tested.
  • Both NSAIDs effectively resolved lameness, confirming expected therapeutic effects.

Conclusions and Implications

  • The study found no evidence of acute gastric mucosal damage associated with high-dose firocoxib treatment over 5 days in this small group of horses.
  • Due to non-randomized allocation and the small sample size, these results are preliminary and cannot establish causality or generalize to broader populations.
  • The baseline differences, especially the pre-existing inflammation in the flunixin group, complicate direct comparisons between treatments.
  • These findings are important for generating hypotheses for future research but require confirmation with larger, randomized controlled trials for definitive safety assessments.
  • The study supports the potential mucosal safety of high-dose firocoxib but stresses caution in clinical use until further evidence is obtained.

Cite This Article

APA
de Oliveira RA, Correa ADS, Monteiro FDO, Teixeira PPM. (2026). Gastroscopic Evaluation of Gastric Mucosa in Horses Treated With Flunixin Meglumine or High-Dose Firocoxib: A Descriptive Pilot Study. Vet Med Sci, 12(4), e71061. https://doi.org/10.1002/vms3.71061

Publication

Veterinary medicine and science
ISSN: 2053-1095
NlmUniqueID: 101678837
Country: England
Language: English
Volume: 12
Issue: 4
Pages: e71061

Researcher Affiliations

de Oliveira, Renato Abrantes
  • Veterinary Medicine Institute, Federal University of Pará, Castanhal, Pará, Brazil.
Correa, Alexandre da Silva
  • Veterinary Medicine Institute, Federal University of Pará, Castanhal, Pará, Brazil.
Monteiro, Francisco Décio de Oliveira
  • Federal Institute of Tocantins (IFTO), Campus Araguatins, Araguatins, Tocantins, Brazil.
Teixeira, Pedro Paulo Maia
  • Veterinary Medicine Institute, Federal University of Pará, Castanhal, Pará, Brazil.

MeSH Terms

  • Animals
  • 4-Butyrolactone / analogs & derivatives
  • 4-Butyrolactone / adverse effects
  • 4-Butyrolactone / administration & dosage
  • Gastric Mucosa / drug effects
  • Gastric Mucosa / pathology
  • Pilot Projects
  • Anti-Inflammatory Agents, Non-Steroidal / adverse effects
  • Anti-Inflammatory Agents, Non-Steroidal / administration & dosage
  • Sulfones / adverse effects
  • Sulfones / administration & dosage
  • Clonixin / analogs & derivatives
  • Clonixin / adverse effects
  • Clonixin / administration & dosage
  • Gastroscopy / veterinary
  • Horse Diseases / chemically induced
  • Horse Diseases / drug therapy
  • Horses
  • Female
  • Stomach Ulcer / veterinary
  • Stomach Ulcer / chemically induced
  • Male

References

This article includes 26 references
  1. Araújo RA, Sales NAA, Basile RC. Safety Assessment of an Oral Therapeutic Dose of Firocoxib on Healthy Horses. Veterinary Sciences 2023;10(2):79.
    doi: 10.3390/vetsci10020079google scholar: lookup
  2. Arena I, Marliani G, Sabioni S, Gabai G, Bucci D, Accorsi PA. Assessment of Horses' Welfare: Behavioural, Hormonal, and Husbandry Aspects. Journal of Veterinary Behavior 2021;41:82–90.
    doi: 10.1016/j.jveb.2021.01.006google scholar: lookup
  3. Bishop RC, Wilkins PA, Kemper AM, Stewart RM, Roy MF, Koenig J. Effect of Firocoxib and Flunixin Meglumine on Large Colon Mural Thickness of Healthy Horses. Journal of Equine Veterinary Science 2023;126:104529.
    doi: 10.1016/j.jevs.2023.104529google scholar: lookup
  4. Camacho‐Luna P, Buchanan B, Andrews FM. Advances in Diagnostics and Treatments in Horses and Foals With Gastric and Duodenal Ulcers. The Veterinary Clinics of North America Equine Practice 2018;34(1):97–111.
    doi: 10.1016/j.cveq.2017.11.007google scholar: lookup
  5. Carroll CL, Huntington PJ. Body Condition Scoring and Weight Estimation of Horses. Equine Veterinary Journal 1988;20(1):41–45.
    doi: 10.1111/j.2042‐3306.1988.tb01451.xgoogle scholar: lookup
  6. Cook VL, Blikslager AT. The Use of Nonsteroidal Anti‐inflammatory Drugs in Critically Ill Horses. Journal of Veterinary Emergency and Critical Care 2015;25(1):76–88.
    doi: 10.1111/vec.12271google scholar: lookup
  7. Cook VL, Meyer CT, Campbell NB, Blikslager AT. Effect of Firocoxib or Flunixin Meglumine on Recovery of Ischemic‐Injured Equine Jejunum. American Journal of Veterinary Research 2009;70(8):992–1000.
    doi: 10.2460/ajvr.70.8.992google scholar: lookup
  8. Davis JL. Nonsteroidal Anti‐Inflammatory Drug Associated Right Dorsal Colitis in the Horse. Equine Veterinary Education 2017;29(2):104–108.
    doi: 10.1111/eve.12600google scholar: lookup
  9. Duz M, Marshall JF, Parkin TD. Proportion of Non‐Steroidal Anti‐Inflammatory Drug Prescription in Equine Practice. Equine Veterinary Journal 2019;51(2):147–153.
    doi: 10.1111/evj.12997google scholar: lookup
  10. Duz M, Parkin TD, Cullander RM. Effect of Flunixin Meglumine and Firocoxib on Ex Vivo Cyclooxygenase Activity in Horses Undergoing Elective Surgery. American Journal of Veterinary Research 2015;76(10):856–864.
    doi: 10.2460/ajvr.76.10.856google scholar: lookup
  11. Ferlini Agne G, May BE, Lovett A, Simon O, Steel C, Sykes BW. Horse Grimace Scale Does Not Detect Pain in Horses With Equine Gastric Ulcer Syndrome. Animals 2023;13(11):1855.
    doi: 10.3390/ani13111855google scholar: lookup
  12. Flood J, Stewart AJ. Non‐Steroidal Anti‐Inflammatory Drugs and Associated Toxicities in Horses. Animals 2022;12(21):2939.
    doi: 10.3390/ani12212939google scholar: lookup
  13. Frippiat T, Bonhomme M, Dyson S. Evaluation of Owner‐Reported Clinical Signs and Fecal Occult Blood Tests as Predictors of Equine Gastric Ulcer Syndrome in Competition Dressage Horses. Journal of Veterinary Internal Medicine 2025;39(6):e70248.
    doi: 10.1111/jvim.70248google scholar: lookup
  14. MacAllister CG, Morgan SJ, Borne AT, Pollet RA. Comparison of Adverse Effects of Phenylbutazone, Flunixin Meglumine, and Ketoprofen in Horses. Journal of the American Veterinary Medical Association 1993;202(1):71–77.
  15. Martineau H, Thompson H, Taylor D. Pathology of Gastritis and Gastric Ulceration in the Horse. Part 2: A Scoring System. Equine Veterinary Journal 2009;41(7):646–651.
    doi: 10.2746/042516409x464799google scholar: lookup
  16. Mercer MA, Davis JL, McKenzie HC. The Clinical Pharmacology and Therapeutic Evaluation of Non‐Steroidal Anti‐Inflammatory Drugs in Adult Horses. Animals 2023;13(5):942.
    doi: 10.3390/ani13050942google scholar: lookup
  17. Pessoa GO, Trigo P, Neto FDM. Comparative Well‐Being of Horses Kept Under Total or Partial Confinement Prior to Employment for Mounted Patrols. Applied Animal Behaviour Science 2016;184:51–58.
    doi: 10.1016/j.applanim.2016.08.014bgoogle scholar: lookup
  18. Richardson LM, Whitfield-Cargile CM, Cohen ND, Chamoun-Emanuelli AM, Dockery HJ. Effect of Selective Versus Nonselective Cyclooxygenase Inhibitors on Gastric Ulceration Scores and Intestinal Inflammation in Horses. Veterinary Surgery 2018;47(6):784–791.
    doi: 10.1111/vsu.12941google scholar: lookup
  19. Singer ER, Smith MA. Examination of the Horse With Colic: Is It Medical or Surgical?. Equine Veterinary Education 2002;14(3):147–155.
    doi: 10.1111/j.2042-3292.2002.tb00147.xgoogle scholar: lookup
  20. Spanton J. Equine Gastric Ulcer Syndrome and the Challenges Facing Clinicians. UK-Vet Equine 2024;8(2):S17–S23.
    doi: 10.12968/ukve.2024.8.s1.17google scholar: lookup
  21. Stiller C-O, Hjemdahl P. Lessons From 20 Years With COX‐2 Inhibitors: Importance of Dose–Response Considerations and Fair Play in Comparative Trials. Journal of Internal Medicine 2022;292(2):240–256.
    doi: 10.1111/joim.13505google scholar: lookup
  22. Sykes BW, Bowen M, Habershon-Butcher JL, Green M, Hallowell GD. Management Factors and Clinical Implications of Glandular and Squamous Gastric Disease in Horses. Journal of Veterinary Internal Medicine 2019;33(1):233–240.
    doi: 10.1111/jvim.15350google scholar: lookup
  23. Sykes BW, Hewetson M, Hepburn RJ, Luthersson N, Tamzali Y. European College of Equine Internal Medicine Consensus Statement – Equine Gastric Ulcer Syndrome in Adult Horses. Journal of Veterinary Internal Medicine 2015;29(5):1288–1299.
    doi: 10.1111/jvim.13578google scholar: lookup
  24. Van den Boom R. Equine Gastric Ulcer Syndrome in Adult Horses. Veterinary Journal 2022;283:105830.
    doi: 10.1016/j.tvjl.2022.105830google scholar: lookup
  25. Vokes J, Lovett A, Sykes B. Equine Gastric Ulcer Syndrome: An Update on Current Knowledge. Animals 2023;13(8):1267.
    doi: 10.3390/ani13071261google scholar: lookup
  26. Ziegler AL, Freeman CK, Fogle CA. Multicentre, Blinded, Randomised Clinical Trial Comparing the Use of Flunixin Meglumine With Firocoxib in Horses With Small Intestinal Strangulating Obstruction. Equine Veterinary Journal 2019;51(3):329–335.
    doi: 10.1111/evj.13024google scholar: lookup

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