Published: Journal of Analytical Toxicology, Volume
23,
Number 5,
September 1999,
pp.323-332 .
Urinary Excretion of 11-nor-9-Carboxy-D9-Tetrahydrocannabinol
and Cannabinoids in
Frequent and Infrequent Drug Users*
Anne Smith-Kielland , Bjørn Skuterud, and Jørg
Mørland
Urinary excretion of 11-nor-9-carboxy-D9-tetrahydrocannabinol
(THCCOOH) and cannabinoids was monitored in prison inmates. Urinary specimens
were collected up to five times per day. EMIT™ (cutoff 20 ng/mL; EMIT20)
and gas chromatography (GC) (cutoff 10.3 ng/mL, LOD 1.4 ng/mL) were used for cannabinoid
screening and THCCOOH confirmation, respectively. Urinary creatinine concentrations
were recorded. Of the samples with positive EMIT screens, 78% were confirmed by
GC analysis. The plotting of THCCOOH/creatinine ratios (THCCOOH/C) versus time
gave smoother excretion curves than THCCOOH concentrations alone. Based on THCCOOH/C
the first 5 days after the last reported intake, the mean urinary excretion half-life
was 1.3 days in infrequent users, and a median of 1.4 days was found in frequent
users. In the latter group, apparent terminal urinary excretion half-lives up
to 10.3 days were observed. The last positive specimens were found after 4 days
for THCCOOH with cutoff 15.0 ng/mL (NIDA/SAMSHA), 5 days for THCCOOH with cutoff
10.3 ng/mL, and 12 days for cannabinoids (EMIT20) in infrequent users and after
17, 22, and 27 days, respectively, in frequent users. Increases in urinary cannabinoids
were sometimes found without concomitant increase in THCCOOH or THCCOOH/C. One
subject admitted new cannabis intake, after which marked increases in THCCOOH
and THCCOOH/C were observed. In others, new intake was suspected. Considerable
variations between consecutive specimens were also observed in THCCOOH concentration
and THCCOOH/C ratio without suspicion of a new intake.
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