Oral cannabidiol increases thermal threshold in horses without physiologic adverse effects.

Research Overview

• This study examined the effects of oral cannabidiol (CBD) on pain thresholds and physiological health markers in horses.
• The research found that oral CBD increased thermal pain threshold without causing adverse physiological effects.

Study Design and Methodology

• Subjects: Six horses (3 geldings and 3 mares) participated.
• Design: Prospective, randomized, masked crossover study conducted over approximately 1.5 months (March to May 2025).
• Treatments: Each horse received either
  • 3.48 mg/kg of CBD oil orally every 24 hours for 3 days, or
  • Placebo oil (sesame oil) on the alternate cycle.
• Measurements:
  • Thermal and mechanical pain thresholds assessed at baseline (before treatment) and at 4 and 12 hours after each treatment administration, daily.
  • Physiologic variables measured simultaneously included heart rate, respiratory rate, and rectal temperature.
• Data Analysis:
  • Generalized mixed model statistics with significance set at P < .05.
  • Student’s t-test for comparing specific time points.

Key Findings

• Thermal Threshold Effects:
  • CBD significantly increased the thermal pain threshold, indicating a temporary reduction in thermal pain sensitivity.
  • This effect was noted on day 2 at the 12-hour measurement and on day 3 at the 4-hour measurement post-dosing.
• Mechanical Threshold Effects:
  • No significant changes in mechanical pain threshold were observed with CBD compared to placebo.
• Physiologic Measures:
  • Respiratory rates averaged 17 breaths/min (CBD) vs. 18 breaths/min (placebo), showing no meaningful difference.
  • Heart rate and rectal temperature were unaffected by CBD treatment at all measured time points.

Conclusions and Implications

• CBD administration at 3.48 mg/kg orally every 24 hours for three days transiently increases thermal pain threshold in horses, demonstrating intermittent antinociceptive effects specifically for thermal pain.
• The lack of effect on mechanical pain threshold suggests that CBD’s analgesic properties may be modality-specific or limited in scope at the dose and duration tested.
• Physiological parameters remained stable, indicating that oral CBD at this dose is safe and well tolerated without causing adverse cardiorespiratory or temperature regulation effects.
• This supports the potential use of CBD as an adjunctive analgesic agent in equine medicine, particularly for conditions involving thermal nociception, with minimal risk of physiological side effects.