Multicentre, blinded, randomised clinical trial comparing the use of flunixin meglumine with firocoxib in horses with small intestinal strangulating obstruction

BACKGROUND: Small intestinal strangulating obstruction (SISO) is associated with endotoxaemia which leads to an increased risk of death. Nonsteroidal anti‐inflammatory drugs (NSAIDs) are used to treat signs of endotoxaemia by inhibiting cyclo‐oxygenases (COX). COX‐1 is expressed constitutively and promotes gut barrier function, whereas COX‐2 is inducible and contributes to the signs of endotoxaemia. In preclinical SISO trials, intestinal barrier recovery was more complete with reductions in endotoxin permeability in horses treated with COX‐2 selective NSAIDs as compared with horses treated with flunixin meglumine. OBJECTIVES: We hypothesised that treatment of post‐surgical SISO horses with firocoxib (COX‐2 selective) would reduce the signs of endotoxaemia to a greater extent than flunixin meglumine (nonselective COX inhibitor) while continuing to provide similar levels of pain control. STUDY DESIGN: Blinded randomised clinical trial. METHODS: In addition to clinical monitoring, preoperative and 12‐, 24‐ and 48‐h post‐operative plasma samples were assessed for prostaglandin E₂ (PGE₂), thromboxane B₂ (TXB₂), TNF⍺ and soluble CD14 (sCD14). RESULTS: In 56 recruited SISO horses, either flunixin meglumine (1.1 mg/kg, i.v., q12h) or firocoxib (0.3 mg/kg, i.v. loading dose; 0.1 mg/kg, i.v., q24h) was given in the post‐operative period in three university hospitals from 2015 to 2017. COX‐2 selectivity was confirmed by a relative lack of inhibition of the COX‐1 prostanoid TXB₂ by firocoxib and significant inhibition by flunixin meglumine (P = 0.014). Both drugs inhibited the COX‐2 prostanoid PGE₂. There were no significant differences in pain scores between groups (P = 0.2). However, there was a 3.23‐fold increased risk (P = 0.04) of increased plasma sCD14 in horses treated with flunixin meglumine, a validated biomarker of equine endotoxaemia. MAIN LIMITATIONS: Horses were all treated with flunixin meglumine prior to referral. In addition, many horses were treated with lidocaine, which has been shown to mitigate the deleterious effects of flunixin meglumine. CONCLUSIONS: In SISO cases, firocoxib reduced a biomarker of endotoxaemia as compared with flunixin meglumine while continuing to provide similar levels of pain control.