Pharmacokinetic modelling of orally administered cannabidiol and implications for medication control in horses.
Authors: Eichler Fabienne, Poźniak Błażej, Machnik Marc, Schenk Ina, Wingender Anke, Baudisch Natalie, Thevis Mario, Bäumer Wolfgang, Lischer Christoph, Ehrle Anna
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Pharmacokinetics of Oral Cannabidiol in Horses Cannabidiol (CBD) products are increasingly used in equine practice to manage stress, inflammation and pain, yet their detection windows and doping control implications remain poorly characterised. Researchers administered escalating single doses (0.2–3 mg/kg) and repeated doses (3 mg/kg twice daily for 15 days) of CBD paste to horses, collecting blood and urine samples throughout and for two weeks post-administration, with concentrations analysed by gas chromatography/tandem-mass-spectrometry. Single doses of 3 mg/kg produced a maximum serum concentration (Cmax) of 12.17 ng/mL, whilst multiple dosing revealed an exceptionally long terminal half-life of 161 hours, indicating substantial tissue accumulation and extensive hepatic metabolism (particularly to the metabolite 7-carboxy-CBD). The urine-to-serum concentration ratio remained consistent at 4.45:1, providing doping control laboratories with a means to establish detection cut-offs, though the authors emphasise that therapeutic efficacy thresholds must first be determined. For equine professionals, these findings underscore that CBD persists in detectable concentrations for extended periods even after discontinuation—a critical consideration for competition horses, whilst the favourable safety profile supports continued clinical investigation of its anti-inflammatory potential in non-competing animals.
Read the full abstract on PubMed
Practical Takeaways
- •CBD has a very long elimination half-life (161+ hours), meaning detection in doping tests is possible for extended periods after administration—critical information for competition horses
- •The extensive tissue distribution and metabolism of CBD means effects may be prolonged, but establishing therapeutic cut-off levels requires further investigation of actual clinical efficacy
- •Doping control laboratories can now use the calculated urine-to-serum ratio (4.45) to interpret analytical results and distinguish between recent use and environmental contamination
Key Findings
- •Oral CBD was well-tolerated in horses with a three-compartment pharmacokinetic model and zero-order absorption best describing its properties
- •CBD showed extensive metabolism with a terminal half-life of 161.29 ± 43.65 hours in serum following multiple doses at 3 mg/kg twice daily
- •Single dose of 3 mg/kg CBD produced Cmax of 12.17 ± 2.08 ng/mL with dose proportionality in AUC0-12h but leveling off at higher doses
- •Steady-state urine to serum concentration ratio (Rss) was 4.45 ± 1.04, establishing detection parameters for doping control laboratories