Chronic oral dosing of cannabidiol and cannabidiolic acid full-spectrum hemp oil extracts has no adverse effects in horses: a pharmacokinetic and safety study.

Objective: To compare the pharmacokinetics of cannabidiol (CBD) and cannabidiolic acid (CBDA) in horses and to evaluate the safety of their chronic administration.

Methods: CBD- and CBDA-rich oil (1 mg/kg) were administered orally twice daily to 7 adult horses over 6 weeks in a randomized, crossover design with a 2-week washout period. A 12-hour pharmacokinetic analysis was conducted on day 1 of each 6-week trial, followed by the measurement of peak and trough concentrations at weeks 1, 2, 4, and 6. The cannabinoids safety was assessed via daily physical examination, periodic bloodwork, and liver biopsy at the beginning and end of the study.

Results: 12-hour pharmacokinetics revealed a higher maximum serum concentration (103 vs 12 ng/mL) and greater area under the curve (259 vs 62 ng·h/mL) for CBDA when compared to CBD. Cannabidiolic acid nadir and peak serum levels over time ranged from 46 to 122 ng/mL, which was higher than CBD (12 to 38 ng/mL). Complete blood count and serum chemistry revealed no clinically relevant changes with either CBD or CBDA. No significant abnormalities were detected on liver ultrasonographic and histopathologic evaluation on day 0 and after both phases of the study.

Conclusions: A dose of either 1 mg/kg of CBD or CBDA administered long term appears safe; however, CBDA serum concentrations suggest superior absorption/retention.

Clinical relevance: Chronic cannabinoid supplementation in horses is safe. Considering the higher absorption of CBDA, its use is recommended to evaluate the therapeutic efficacy of this common hemp derived cannabinoid.