Can we obtain information from urine about recent cannabis con- sumption in DUID cases?

Aim: The nonlinear elimination rate of THC and metabolites in blood complicates the interpretation of last cannabis use, which is an important information in DUID cases. We evaluated cannabinoids in blood and hydrolysed urine from 50 DUID cases in order to gain additional information about last cannabis use. Methods: THC, THC-OH and THC-COOH were analysed in blood and hydrolysed urine (βglucuronidase) by GC-MS-MS. Cannabinoid concentrations in blood and urine were compared. Mann-Whitney-U-Tests were performed to investigate differences between cannabinoid concentrations from recent and older cannabis intake. Blood/urine cannabinoid concentrations of admitted chronic users were compared to occasional users. An approach for cluster analysis is presented. Results: Cannabinoid concentration in blood and urine were strongly correlated. Blood and urine cannabinoid concentrations from recent cannabis consumers differed significantly from the rest of the test group. No difference in blood/urine concentration was found between chronic and occasional users. Results of a cluster analysis approach were promising. Conclusion: In individual cases, an interpretation of last cannabis use is only possible by approximation. However, multivariate data analysis of cannabinoid concentration might facilitate the detection of recent cannabis intake.