Effects of topical perineural capsaicin in a reversible model of equine foot lameness.

This study demonstrates the analgesic effects of topically applied capsaicin ointment on horses suffering from foot lameness. By applying the ointment to the palmar digital nerves, it was observed that the pain experienced due to lameness was measurably reduced for up to 4 hours.

Objective and Methodology

• The main objective of this study was to test the hypothesis that the topical application of capsaicin ointment along the palmar digital nerves of horses could alleviate the symptoms of equine foot lameness.
• Seven adult horses in good health were selected for the study, all of which were fitted with adjustable heart bar shoes in a unilateral setup.
• To induce lameness—a state in which the horses could not bear weight—the heart bar shoe was tightened.
• The researchers used a crossover design, applying capsaicin ointment over the medial and lateral palmar digital nerves or leaving some horses untreated. This process was reversed after a week.

Results

• The results show that the horses’ heart rate was significantly lower in trials where the capsaicin treatment was applied, observed at 20 and 40 minutes after the application, and between 1.6 to 3.6 hours post-application.
• The lameness score, a measure of the severity of the horse’s condition, decreased significantly at 40 minutes and from 1.3 to 4 hours after the capsaicin treatment.
• The findings support the initial hypothesis, demonstrating that the application of capsaicin ointment did provide noticeable pain relief for up to 4 hours after its application.

Implications and Future Research

• The study marks an interesting development in the veterinary use of capsaicin as an analgesic, especially in the equine demographic.
• However, the researchers conclude that its efficacy and clinical applications in treating horses with spontaneous clinical or induced laminitis or other sources of foot pain must be further investigated.
• The study’s findings may serve as a stepping stone for further research into the use of capsaicin ointment as a pain management solution in veterinary medicine.