LAUSR

Despite many studies on cannabinoid pharmacokinetics, the proposals of marker cannabinoids for a recent cannabis use as well as the introduction of mathematical models estimating the time frame between consumption and blood sampling, it is still challenging for forensic toxicologists to estimate the last time of cannabis exposure. In order to assess the informative value of determining (minor) cannabinoids in plasma of cannabis users, detection rates of 14 cannabinoids next to Δ9 -THC and THC-COOH (11-OH-THC, CBC, CBD, CBN, CBDV, THCV, CBG, CBL, Δ8 -THC, THCA, CBDA, CBGA, THCV-COOH, CBN-COOH) were determined. 355 plasma samples, previously tested positive for cannabinoids (Δ9 -THC: approximately 0.4 ng/mL - 125 ng/mL (range), mean: 10.1 ng/mL; THC-COOH: approximately 3.8 ng/mL - 457 ng/mL (range), mean: 71.6 ng/mL), were analyzed by means of LC-MS/MS. All analyzed cannabinoids could be detected in plasma samples with varying incidence. 11-OH-THC, THCA, CBC, CBN and CBD were the most frequent detectable cannabinoids (next to Δ9 -THC and THC-COOH). The dependency of cannabinoid detectability on the plasma Δ9 -THC concentration and on the probable time of consumption (estimated by a model of Huestis and coworkers) was examined. Detection incidences (e.g. 11-OH-THC, CBC) often increased with increasing Δ9 -THC concentration but not for all cannabinoids (e.g. CBD, THCA). The herein presented data for minor cannabinoid findings in plasma can be helpful for a comprehensive interpretation of cannabinoid findings in plasma samples of cannabis users.