How long does a single oral dose of cannabidiol persist in plasma? Findings from three clinical trials.

A growing number of clinical trials (CTs) are investigating the therapeutic potential of cannabidiol (CBD), a non-intoxicating phytocannabinoid found in Cannabis sativa. These CTs often use crossover experimental designs requiring 'washout' (clearance) periods. However, the length of time CBD persists in plasma (its 'window of detection') is unclear and could be significant. Indeed, the structurally related phytocannabinoid, Δ9 -tetrahydrocannabinol (THC), has a long window of detection in plasma. We investigated the extent to which CBD and its major metabolites persist in plasma. Data from three CTs that measured plasma cannabinoid concentrations ≥7 days after administering a single oral dose of CBD were pooled. The CBD doses were as follows: CT #1: 300 mg; CT #2: 200 mg (and 10 mg THC); and CT #3: 15, 300 and 1500 mg (one per treatment session). Thirty-two participants were included in the analysis, 17 of whom (from CT #3) provided repeated measures. Overall, 0% (15 mg), 60% (200 mg), 28% (300 mg) and 100% (1500 mg) of participants had detectable concentrations (i.e., >0.25 ng·ml-1 ) of CBD in plasma ≥7 days post-treatment (some, several weeks post-treatment). A zero-inflated negative binomial mixed-effects regression analysis (R2 m = 0.44; R2 c = 0.73) predicted that, on average, a 13 day washout period would reduce plasma CBD concentrations to 'zero' (i.e., <0.25 ng·ml-1 ) if a single oral dose of 300 mg was consumed. Higher doses require longer washout periods; concomitant medications may also affect clearance. In conclusion, CBD has a long window of detection in plasma. Crossover studies involving CBD should, therefore, be conducted with caution, particularly when higher doses and/or chronic dosing regimens are used.

Effects of Cannabidiol on Exercise Physiology and Bioenergetics: A Randomised Controlled Pilot Trial.

BACKGROUND: Cannabidiol (CBD) has demonstrated anti-inflammatory, analgesic, anxiolytic and neuroprotective effects that have the potential to benefit athletes. This pilot study investigated the effects of acute, oral CBD treatment on physiological and psychological responses to aerobic exercise to determine its practical utility within the sporting context. METHODS: On two occasions, nine endurance-trained males (mean ± SD V̇O2max: 57.4 ± 4.0 mL·min-1·kg-1) ran for 60 min at a fixed intensity (70% V̇O2max) (RUN 1) before completing an incremental run to exhaustion (RUN 2). Participants received CBD (300 mg; oral) or placebo 1.5 h before exercise in a randomised, double-blind design. Respiratory gases (V̇O2), respiratory exchange ratio (RER), heart rate (HR), blood glucose (BG) and lactate (BL) concentrations, and ratings of perceived exertion (RPE) and pleasure-displeasure were measured at three timepoints (T1-3) during RUN 1. V̇O2max, RERmax, HRmax and time to exhaustion (TTE) were recorded during RUN 2. Venous blood was drawn at Baseline, Pre- and Post-RUN 1, Post-RUN 2 and 1 h Post-RUN 2. Data were synthesised using Cohen's dz effect sizes and 85% confidence intervals (CIs). Effects were considered worthy of further investigation if the 85% CI included ± 0.5 but not zero. RESULTS: CBD appeared to increase V̇O2 (T2: + 38 ± 48 mL·min-1, dz: 0.25-1.35), ratings of pleasure (T1: + 0.7 ± 0.9, dz: 0.22-1.32; T2: + 0.8 ± 1.1, dz: 0.17-1.25) and BL (T2: + 3.3 ± 6.4 mmol·L-1, dz: > 0.00-1.03) during RUN 1 compared to placebo. No differences in HR, RPE, BG or RER were observed between treatments. CBD appeared to increase V̇O2max (+ 119 ± 206 mL·min-1, dz: 0.06-1.10) and RERmax (+ 0.04 ± 0.05 dz: 0.24-1.34) during RUN 2 compared to placebo. No differences in TTE or HRmax were observed between treatments. Exercise increased serum interleukin (IL)-6, IL-1ß, tumour necrosis factor-α, lipopolysaccharide and myoglobin concentrations (i.e. Baseline vs. Post-RUN 1, Post-RUN 2 and/or 1-h Post-RUN 2, p's < 0.05). However, the changes were small, making it difficult to reliably evaluate the effect of CBD, where an effect appeared to be present. Plasma concentrations of the endogenous cannabinoid, anandamide (AEA), increased Post-RUN 1 and Post-RUN 2, relative to Baseline and Pre-RUN 1 (p's < 0.05). CBD appeared to reduce AEA concentrations Post-RUN 2, compared to placebo (- 0.95 ± 0.64 pmol·mL-1, dz: - 2.19, - 0.79). CONCLUSION: CBD appears to alter some key physiological and psychological responses to aerobic exercise without impairing performance. Larger studies are required to confirm and better understand these preliminary findings. Trial Registration This investigation was approved by the Sydney Local Health District's Human Research Ethics Committee (2020/ETH00226) and registered with the Australia and New Zealand Clinical Trials Registry (ACTRN12620000941965).