Cannabinoid concentrations in confiscated cannabis samples and in whole blood and urine after smoking CBD-rich cannabis as a “tobacco substitute”


In Switzerland, only cannabis with a total Δ9-tetrahydrocannabinol (THC) content higher than 1% is controlled by the narcotics legislation. Cannabis products rich in cannabidiol (CBD) and low in THC can be legally sold as tobacco substitutes. In this paper, we address analytical and forensic toxicological issues related to the increasing availability and consumption of these products. Based on the analysis of 531 confiscated cannabis samples, we could establish classification thresholds: plant material with a ratio of total THC/total CBD ≥ 3 is graded as THC-rich/CBD-poor, whereas samples with a ratio ≤ 0.33 are categorized as CBD-rich/THC-poor cannabis. We also evaluated an on-site test kit as a rapid alternative to the laborious liquid or gas chromatography (LC or GC)-based techniques normally used for the differentiation between THC- and CBD-cannabis. Furthermore, we determined whole blood and urine cannabinoid levels after smoking different doses of legal CBD-cannabis. A male volunteer smoked one cigarette within 15 min and four cigarettes within 1 h and within 30 min, respectively. Cigarettes contained on average 42.7 mg CBD and 2.2 mg THC. Blood samples were collected up to 1.1 h and urine samples up to 27.3 h after the beginning of smoking. All urine samples tested negative by three immunochemical assays for detection of cannabis use. This is an important finding for abstinence monitoring. However, we found that the trace amounts of THC present in CBD-cannabis can produce THC blood levels above the Swiss legal limit for driving, and thus render the consumer unable to drive from a legal point of view.

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The authors gratefully acknowledge Alain Broillet, Beatrice Grossen, and Severine Krönert for the evaluation of the on-site test kit and the analyses of confiscated cannabis samples, Thomas Wüthrich for his support with LC-MS/MS data acquisition and the whole team of the Forensic Toxicology laboratory at the Institute of Forensic Medicine Bern for supporting this project.

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Corresponding author

Correspondence to Wolfgang Weinmann.

Ethics declarations

According to the ethics committee of the Canton of Bern, Switzerland, this study does not apply to Art. 3a of the Federal Act on Research involving Human Beings (Human Research Act) since it is a study only involving one participant—who was the principal investigator himself in a self-experiment. Therefore, they did not decide on the application listed with the project ID No. 2018-01037. However, written informed consent was obtained from the participant of the cannabis smoking study.

All procedures performed were in accordance with the ethical standards of the institutional research committee and the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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The authors declare that they have no conflict of interest.

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Hädener, M., Gelmi, T.J., Martin-Fabritius, M. et al. Cannabinoid concentrations in confiscated cannabis samples and in whole blood and urine after smoking CBD-rich cannabis as a “tobacco substitute”. Int J Legal Med 133, 821–832 (2019).

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  • Tetrahydrocannabinol
  • Cannabidiol
  • Classification
  • Drug of abuse testing
  • Driving while impaired