Phenylbutazone and flunixin meglumine used singly or in combination in experimental lameness in horses.

The study examines the effectiveness of separately and jointly using two drugs, Phenylbutazone and Flunixin meglumine, to alleviate lameness in horses. The results concluded that the combination of the two was not more effective than using either drug alone.

Research Methodology

• The researchers induced lameness in 8 healthy Thoroughbred horses through an adjustable heart bar shoe model of foot pain and treated them at weekly intervals. The horses received one of four intravenous treatments: saline placebo, Phenylbutazone (PBZ), Flunixin meglumine (FM), or a combination of PBZ and FM.
• Both heart rate (HR) and lameness score (LS) were assessed in a blinded manner every 20 minutes for 5 hours post lameness induction and then hourly for 12 hours post treatment. These measures helped determine the effectiveness of the drugs in relieving pain.
• Blood samples were taken at various intervals and analyzed for drug concentrations. The researchers looked for a correlation between drug concentration and analgesic effect.
• The researchers applied a repeated measures ANOVA and post hoc Tukey’s test to identify the analgesic effects at a significance level of P<0.05.

Research Findings

• Analgesic effects, identified by the decrease in heart rate, were noticed in all the nonsteroidal anti-inflammatory drug (NSAID) -treated trials up to 10 hours post treatment.
• Effects of FM and the combined treatment (PBZ+FM) lasted for 12 hours post treatment.
• Lameness scores decreased earlier in horses treated with PBZ and the combined treatment than those treated with FM alone, and the analgesic effect on the lameness scores lasted for 12 hours for all anti-inflammatory drug trials.
• Peak plasma concentrations for PBZ and FM were measured, with PBZ being significantly higher than FM.
• Despite these results, the research concluded that the combination of PBZ+FM was not more effective than either PBZ or FM alone. This contradicts earlier assumptions that a combined treatment would be more effective in alleviating lameness.

Conclusion

• The study rejects its initial hypothesis that combining Phenylbutazone and Flunixin meglumine would be more efficacious than individual treatments in relieving foot pain.
• The application of these findings is that it is no more beneficial to use both drugs simultaneously than to choose one to treat a lame horse, at least at these specific dosages and in this model of acute foot pain.