Free and Glucuronidated Cannabinoids, Subjective, Physiological and Psychomotor Effects and In Vitro Cannabinoid Stability Following Controlled Smoked Cannabis Administration

Abstract

Delta9-tetrahydrocannabinol (THC) is the illicit drug most frequently observed in accident and driving under the influence of drugs (DUID) investigations. Whole blood is often the only available specimen collected during such investigations. However, whole blood cannabinoid concentrations (including phase II cannabinoid glucuronide metabolites) and relationships between subjective and psychomotor effects and cannabinoid blood concentrations following cannabis smoking have not been examined. Furthermore, there was no analytical method to investigate whole blood cannabinoid glucuronides directly. Nine male and one female chronic, heavy cannabis smokers resided on a closed research unit and smoked ad libitum one 6.8% THC cannabis cigarette. Whole blood and plasma specimens were collected up to 22 h after smoking. THC, 11-hydroxy-THC (11-OH-THC), 11-nor-9-carboxy-THC (THCCOOH), cannabidiol (CBD), cannabinol (CBN), THC-glucuronide and THCCOOH-glucuronide were directly quantified by a new, validated liquid chromatography-tandem mass spectrometry method. Specimens were analyzed within 24 h of collection to obviate stability issues. Assessments were performed before and up to 6 h after smoking, including subjective (visual analog scales [VAS] and Likert scales), physiological (heart rate, blood pressure, respirations) and psychomotor (critical tracking and divided attention tasks) measures. Analytical method linearity (R<super>2</super> ≥ 0.997) ranged from 0.5-50 μg/L (THC-glucuronide), 1.0-100 μg/L (THC, 11-OH-THC, THCCOOH, CBD and CBN) and 5.0-250 μg/L (THCCOOH-glucuronide). Median whole blood (plasma) observed C_max were 50 (76), 6.4 (10), 41 (67), 1.3 (2.0), 2.4 (3.6), 89 (190), and 0.7 (1.4) μg/L 0.25 h after starting smoking for THC, 11-OH-THC, THCCOOH, CBD, CBN, and THCCOOH-glucuronide, respectively, and 0.5 h for THC-glucuronide. CBD and CBN were not detectable after 1 h. THC significantly increased VAS responses and heart rate, with concentration-effect curves demonstrating counter-clockwise hysteresis. No differences were observed for critical tracking or divided attention task performance in this cohort of heavy, chronic cannabis smokers. These are the first authentic human whole blood cannabinoid metabolite data following controlled cannabis smoking. Minor cannabinoids and cannabinoid glucuronide data were evaluated as markers of recent cannabis use. These findings will improve interpretation of whole blood and plasma cannabinoid results, further identification of recent cannabis intake, and inform our understanding of impairment and subjective effects following acute smoked cannabis.