Efficacy of single-dose intravenous phenylbutazone and flunixin meglumine before, during and after exercise in an experimental reversible model of foot lameness in horses.

This study examined how effective single doses of the nonsteroidal anti-inflammatory drugs (NSAIDs) phenylbutazone and flunixin meglumine are in reducing foot lameness in horses before, during, and after exercise. The result demonstrated the definite clinical effectiveness of these drugs.

Study Overview

The study was designed to deliver objective blind efficacy data on the effect of single-dose intravenous (i.v.) NSAIDs on horses both before, during, and after exercise. The tested hypothesis was that a single i.v. dose of either phenylbutazone (PBZ) or flunixin meglumine (FM) would prove more efficacious than a saline control (SAL) when administered before, during, and after exercise in a reversible model of foot lameness.

Methodology

• Six Quarter Horse mares were used in the experiment and a reversible model of foot lameness was artificially induced in the horses.
• An hour before treatment, the lameness was induced by tightening a set screw against a heart bar shoe.
• The treatments were randomized and blinded and included PBZ, FM, and SAL.
• The heart rate and lameness scores (LS) of the horse were recorded at varying intervals before and after the exercise, as well as during the treadmill workloads.
• The data collected was analyzed using RM ANOVA and Student-Newman-Keul’s test and Wilcoxon signed rank test, with statistical significance set at P < 0.05.

Results

• The NSAIDs reduced the pre-exercise mean heart rate compared to the saline control from 1:20-4 hours after the treatment.
• The lameness score (LS) also decreased significantly for both NSAIDs in comparison to the saline control.
• After exercise, while there was no difference in heart rate between the different treatments, the lameness score decreased more for the horses treated with NSAIDs compared to those treated with saline.
• The mean recovery heart rate was also lower for the horses treated with PBZ and FM in comparison to the saline control.

Conclusions

The main conclusion of the study is that both PBZ and FM proved clinically efficacious in managing foot lameness in horses when administered before, during, or after exercise. However, the use of these single doses during competition may mask lameness, potentially affecting the ability of judges to accurately assess the horses’ soundness in competition.