Anti-nociceptive efficacy of the soluble epoxide hydrolase inhibitor t-TUCB in horses with mechanically induced lameness

Abstract

Introduction: Soluble epoxide hydrolase (sEH) inhibitors are novel anti-inflammatory and analgesic agents that could improve pain management in horses. The objective of the present study was to evaluate the anti-nociceptive effect of a single-dose intravenous administration of the sEH inhibitor trans-4-{4-[3-(4-trifluro-methoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid (t-TUCB) using an adjustable heart bar shoe (a-HBS) model of lameness. We hypothesized that t-TUCB would improve objective and subjective lameness measures compared to the control.

Materials and methods: Reversible lameness was induced in 8 horses for 24 h using an a-HBS in a randomized, crossover design. A vehicle-control placebo (DMSO) or t-TUCB (1 mg/kg) was intravenously administered at time 0 following a baseline induced lameness evaluation. Blood was collected and lameness was objectively measured with an inertial sensor system at 0-, 1-, 3-, 6-, 12-, and 24-h time points. Front-facing videos were obtained at each time point for subjective evaluation by three blinded evaluators using a visual analog scale (VAS).

Results: Treatment with t-TUCB significantly decreased (i.e. improved) lameness compared to placebo at 1-h and compared to baseline at 1-, 3-, and 6-h following administration. Lameness significantly increased (i.e. worsened) from baseline in placebo-treated horses 12 h after administration. All horses returned to baseline soundness within 24 h of reversing lameness.

Conclusion: Treatment with single-dose IV administration of t-TUCB improved lameness induced by the a-HSB, suggesting that t-TUCB has anti-nociceptive effects in horses.

Clinical relevance: The soluble epoxide hydrolase inhibitor, t-TUCB, is a promising novel analgesic for horses.

Keywords: Adjustable heart-bar shoe; Analgesia; Equine; Nociception; Soluble epoxide hydrolase inhibitor.