Pharmacokinetic Characterization of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in Urine Following Acute Oral Cannabis Ingestion in Healthy Adults.
Understanding the urine excretion profile for Δ9-tetrahydrocannabinol (THC) metabolites is important for accurate detection and interpretation of toxicological testing for cannabis use. Prior literature has primarily evaluated the urinary pharmacokinetics of the non-psychoactive THC metabolite 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) following smoked cannabis administration. The present study examined the urine THCCOOH excretion profile following oral cannabis administration in 18 healthy adults. Following ingestion of a cannabis-containing brownie with 10, 25 or 50 mg of THC (N 6 per dose), urine specimens were collected on a closed residential research unit for 6 days, followed by three outpatient visits on Days 7-9. Average maximum concentrations (Cmax) of THCCOOH were 107, 335 and 713 ngmL, and average times to maximum concentration (Tmax) were 8, 6 and 9 h for the 10, 25 and 50 mg THC doses, respectively. Detection windows to first positive and last positive varied as a function of dose higher doses had shorter time to first positive and longer time to last positive. Considerable inter-subject variability was observed on study outcomes. Gas chromatographymass spectrometry (GCMS 15 ngmL cutoff) was used as the criterion to assess sensitivity, specificity and agreement for THCCOOH qualitative immunoassay tests using 20, 50 and 100 ngmL cutoffs. The 50 ngmL cutoff displayed good sensitivity (92.5%), specificity (92.4%) and overall agreement (92.4%), whereas the 20 ngmL cutoff demonstrated poor specificity (58.4%), and the 100 ngmL cutoff exhibited reduced sensitivity (70.9%). Ingestion of cannabis brownies containing the 10 and 25 mg THC doses yielded THCCOOH concentrations that differed in magnitude and time course from those previously reported for the smoked route of administration of comparable doses.