Cannabidiol in the horse: pharmacokinetics and effects of a pelleted supplement on reactivity and movement

A multitude of claims exist regarding therapeutic benefits of cannabidiol (CBD) in human and animal medicine. Though supportive evidence of CBD as a nutraceutical option exists, lack of regulation means that product safety, consistency, and efficacy cannot be guaranteed. Trials for specific conditions and species are needed. The objective of this study was to evaluate CBD safety and use effects on reactivity and movement in the horse. Project 1 examined the bioavailability of a single 50 mg dose of an oil and pelleted CBD product. One of 2 Quarter Horse geldings received the oil product. The second received the pelleted product. Blood samples for serum cannabinoid concentration occurred at 1 h and 2 h post administration. Both products were below LLOQ at 1 h and detectable at 2 h post administration (PEL= 0.163 ng/ml; OIL 0.11 ng/ml). Project 2 examined pharmacokinetics of a single feeding of pelleted CBD at 50 mg (TXT1), 100 mg (TXT2) and 250 mg (TXT3) in 18 stock-type geldings. Blood was collected at 0 (pretreatment), 0.5, 1, 2, 4, and 12 h post treatment for serum CBD concentration. Safety was monitored via serum chemistry and complete blood count. Statistical analysis was completed on serum chemistry values through the PROC MIXED procedure of SAS. Though CBC and serum chemistry results were within reference ranges, treatment differences were observed for creatinine (TXT1=1.41, TXT2=1.22, TXT3=1.49; P ≤0.01) and blood urea nitrogen (BUN; TXT1=15.5, TXT2=16.52, TXT3=18.61; P≤0.03). Peak serum CBD concentrations were observed at 2 h post TXT. The results demonstrated relative safety of a single CBD dose up to 250 mg in the horse, providing foundational knowledge concerning equine dosing. Project 3 evaluated pelleted CBD fed once daily over 6 wk to 24 university riding horses. Pre- and post-TXT evaluations were completed vi on movement parameters and reactivity. Movement analysis examined stride length, and duration of stance and swing phase. Reactivity was observed through a novel object test (NOT). Reactivity scores were documented via live and video evaluators. Heart rate (HR) monitors collected HR data at NOT test points: start, stimulus, and stop. Instructors completed surveys to evaluate movement and behavior patterns of horses during classes. The population was reduced to stock-type geldings (n=17) for NOT and movement statistical analysis. The population was further reduced (n=15) for survey data to only evaluate stock type geldings observed in duplicate (before and after supplementation). Main effects included heart rate (HR), time on stride length (SL), and duration of stance or swing phase. Data was analyzed using the PROC MIXED procedure of SAS and survey data were evaluated using Chi Square for the effect of TXT and age on reactivity scores from the novel object test (NOT). Fisher’s Exact Test was implemented if fewer than 5 responses were observed per observation parameter. No differences were observed in NOT HR values. Low reactivity scores were more frequently observed in TXT horses after 6 wk. During walk, TXT horses spent more time in stance phase (TXT=0.57 sec, CON=0.51 sec; P<0.01) and swing phase (TXT=0.38 sec, CON=0.36 sec; P<0.01). In both groups, walk stance phase duration increased over time (Pre=0.37 sec, Post=0.71 sec; P<0.01), while duration of trot stance (Pre=0.30 sec, Post= 0.26 sec; P<0.01) and swing phase (Pre=0.37 sec, Post= 0.33 sec; P<0.01) decreased. Trot SL shortened by 6 wk (Pre=1.68 m, Post=1.55 m; P=0.03). Survey results indicated a higher instance of positive behaviors when tied and during tack up in TXT horses. Both TXT and CON were best represented in the high suppleness category. Control horses were more frequently rated high for suppleness on a circle and ability to track up. Movement vii analysis revealed no other significant parameters.