GC/MS and EMIT analyses for delta 9-tetrahydrocannabinol metabolites in plasma and urine of human subjects.

Ten male subjects smoked placebo marijuana cigarettes spiked with delta 9-tetrahydrocannabinol (THC) at 150 micrograms/kg body weight. Plasma and urine samples were collected for 22 hr after smoking. Total cross-reacting cannabinoids were measured by immunoassay (EMIT) and THC and major metabolites were identified and quantitated by gas chromatographic/mass spectrometric (GC/MS) procedures. In plasma, THC concentration provided the best indication of recent (less than 6 hr) smoking. In enzyme-hydrolyzed urine, 8 beta, 11-dihydroxy-THC at high concentration was identified in the earliest voidings, falling rapidly to the limit of detection before 22 hr in most subjects. Levels above 15 to 20 ng/mL were indicative of use within the previous 4 to 6 hr.