THC and CBD concentrations in blood, oral fluid and urine following a single and repeated administration of "light cannabis".

Background "Light cannabis" is a product legally sold in Europe with Δ9-tetrahydrocannabinol (THC) concentration lower than 0.2% and variable cannabidiol (CBD) content. We studied THC and CBD excretion profiles in blood, oral fluid (OF) and urine after smoking one or four light cannabis cigarettes. Methods Blood, OF and urine samples were obtained from six healthy light cannabis consumers after smoking one 1 g cigarette containing 0.16% THC and 5.8% CBD and from six others after smoking four 1 g cigarettes within 4 h. Sample collection began 0.5 and 4.5 h after smoking one or four cigarettes, respectively. Cannabinoid concentrations were quantified by gas chromatography-mass spectrometry (GC-MS). Results At the first collection, the highest THC and CBD concentrations occurred in blood (THC 7.0-10.8 ng/mL; CBD 30.2-56.1 ng/mL) and OF (THC 5.1-15.5 ng/mL; CBD 14.2-28.1 ng/mL); similar results occurred 0.5 h after the last of four cigarettes in blood (THC 14.1-18.2 ng/mL, and CBD 25.6-45.4 ng/mL) and OF (THC 11.2-24.3 ng/mL; CBD 14.4-37.0 ng/mL). The mean OF to blood ratio ranged from 0.6 to 1.2 after one and 0.6 to 1.9 after four light cannabis cigarettes. THC/CBD ratios in blood and OF were never greater than 2. Urinary 11-nor-9-carboxy-THC concentrations peaked 8 h after one and four cigarettes. Conclusions OF was a valuable alternative to blood in monitoring consumption of light cannabis. Blood and OF THC/CBD concentration ratios, never exceeded 2, possibly providing a useful biomarker to identify light cannabis vs illegal higher THC cannabis use, where THC/CBD ratios are generally greater than 10.