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

BACKGROUND: 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. OBJECTIVES: 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.