HUMAN URINARY-EXCRETION PROFILE AFTER SMOKING AND ORAL-ADMINISTRATION OF [C-14] DELTA-1-TETRAHYDROCANNABINOL

The urinary excretion profiles of Δ1-tetrahydrocannabinol (Δ1-THC) metabolites have been evaluated in two chronic and two naive marijuana users after smoking and oral administration of [14C]Δ1-THC. Urine was collected for five days after each administration route and analyzed for total Δ1-THC metabolites by radioactivity determination, for Δ1-THC-7-oic acid by high-performance liquid chromatography, and for cross-reacting cannabinoids by the EMIT d.a.u. cannabinoid assay. The average urinary excretion half-life of 14C-labeled Δ1-THC metabolites was calculated to be 18.2 ± 4.9 h (± SD). The excretion profiles of Δ1-THC-7-oic acid and EMIT readings were similar to the excretion profile of 14C-labeled metabolites in the naive users. However, in the chronic users the excretion profiles of Δ1-THC-7-oic acid and EMIT readings did not resemble the radioactive excretion due to the heavy influence from previous Cannabis use. Between 8–14% of the radioactive dose was recovered in the urine in both user groups after oral administration. Lower urinary recovery was obtained both in the chronic and naive users after smoking—5 and 2%, respectively. © 1989 Oxford University Press.