Forensic aspects of the metabolism and excretion of cannabinoids following oral ingestion of cannabis resin.

Following oral ingestion of cannabis resin, delta 9-THC-11-oic acid and its O-ester glucuronide were detected using RIA and combined hplc/RIA and shown to be major plasma metabolites of delta 9-THC. delta 9-THC-11-oic acid was not excreted in the urine in significant concentrations, the glucuronide conjugate being the major urinary metabolite detected. delta 9-THC metabolites were detected in blood for up to 5 days and in urine for up to 12 days following a single oral dose of delta 9-THC (20 mg). Estimates for the half life of delta 9-THC-11-oic acid and its glucuronide in plasma, and total metabolites in urine have been obtained. Interpretation of blood or urine total cannabinoid levels is most difficult, however, drug/metabolite ratios and metabolite/metabolite ratios may have potential for indicating recent cannabis use.