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 Delta 9-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.