D9-Tetrahydrocannabinol and Cannabidiol Time Courses in the Sera of “Light Cannabis” Smokers: Discriminating Light Cannabis Use from Illegal and Medical Cannabis Use

Background: D9-tetrahydrocannabinol (THC) and cannabidiol (CBD) time courses in serum and physiological and behavioral effects associated with smoking 1 or 4 “light cannabis” cigarettes were studied. Biomarkers to differentiate light cannabis versus illegal and medical cannabis use were also investigated. Methods: Sera were obtained at different times from 6 healthy light cannabis consumers and 6 individuals who smoked 1 and 4 cigarettes, within 4 hours through a liquid–liquid method and analyzed by liquid chromatography–tandem mass spectrometry. Results: In serum, minimal THC concentration was observed after a single cigarette smoke, while repeated smoking increased it by 1 order of magnitude. CBD concentrations were higher, but did not increase linearly, probably because it does not preferentially volatilize compared with THC. The highest THC and CBD concentrations were observed 0.5 hours after the start of the smoking of 1 cigarette. Serum THC ranged from 2.7 to 5.9 ng/mL, while serum CBD varied from 5.7 to 48.2 ng/mL. Similarly, the highest THC and CBD concentrations were observed 0.5 hours after the smoking of 4 cigarettes. Specifically, the ranges were THC: 11.0–21.8 ng/mL and CBD: 19.4–35.3 ng/mL. In both cases, the mean THC/CBD concentration ratio ranged from 0.2 to 0.9. There were no significant changes in blood pressure, heart rate, and body temperature, but participants who smoked 4 cigarettes experienced severe drowsiness. Conclusions: THC and CBD time courses in the sera of light cannabis smokers were similar to those previously observed in oral fluid and blood. Serum THC/CBD concentration ratio not higher than the mean value of 0.9 might be a useful biomarker to identify use of light cannabis versus that of illegal THC cannabis (where THC/CBD concentration ratios are generally greater than 10) or versus that of medical cannabis (where ratios are greater than 1). Consumers should be advised of possible drowsiness after he repeated smoking of light cannabis cigarettes.