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. 2008 Oct;32(8):562-9.
doi: 10.1093/jat/32.8.562.

Urinary Elimination of 11-nor-9-carboxy-delta9-tetrahydrocannnabinol in Cannabis Users During Continuously Monitored Abstinence

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Urinary Elimination of 11-nor-9-carboxy-delta9-tetrahydrocannnabinol in Cannabis Users During Continuously Monitored Abstinence

Robert S Goodwin et al. J Anal Toxicol. .
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Abstract

The time course of 11-nor-9-carboxy-Delta9-tetrahydrocannnabinol (THCCOOH) elimination in urine was characterized in 60 cannabis users during 24 h monitored abstinence on a closed research unit for up to 30 days. Six thousand, one hundred fifty-eight individual urine specimens were screened by immunoassay with values > or = 50 ng/mL classified as positive. Urine specimens were confirmed for THCCOOH by gas chromatography-mass spectrometry following base hydrolysis and liquid-liquid or solid-phase extraction. In 60%, the maximum creatinine normalized concentration occurred in the first urine specimen; in 40%, peaks occurred as long as 2.9 days after admission. Data were divided into three groups, 0-50, 51-150, and > 150 ng/mg, based on the creatinine corrected initial THCCOOH concentration. There were statistically significant correlations between groups and number of days until first negative and last positive urine specimens; mean number of days were 0.6 and 4.3, 3.2 and 9.7, and 4.7 and 15.4 days, respectively, for the three groups. These data provide guidelines for interpreting urine cannabinoid test results and suggest appropriate detection windows for differentiating new cannabis use from residual drug excretion.

Figures

Figure 1
Figure 1
Urine cannabinoid data by group (0–50, 51–150 and >150 ng/mg) based on creatinine-normalized THCCOOH concentration in the first urine specimen at the time of admission to the secure research unit. Urine specimens were collected from cannabis users under continuous medical surveillance during cannabis abstinence for up to 30 days: 1.a, Mean number of days before first negative (<50 ng/mL) cannabinoid urine specimen; 1.b, Mean number of days until last positive (≥50 ng/mL) cannabinoid urine specimen; 1.c, Number of days between the first negative (<50 ng/mL) and last positive (≥50 ng/ml) cannabinoid urine specimen; 1.d, Number of urine specimens between the first negative (<50 ng/mL) and last positive (≥50 ng/mL) cannabinoid urine specimen; and 1.e, Cmax THCCOOH/creatinine between first negative (<50 ng/mL) and last positive (≥50 ng/mL) cannabinoid urine specimen.
Figure 2
Figure 2
Title: Mean detection rate each day after the first negative (<50 ng/mL) cannabinoid urine specimen. Cannabis users were separated into three groups (0–50, 51–150 and >150 ng/mg) according to creatinine-normalized THCCOOH concentrations in the first specimen collected at admission. Mean detection rate (number of positive specimens in a day/total number of specimens collected that day multiplied by 100) for the three groups was determined each day after the first negative specimen.
Figure 3
Figure 3
Title: Mean daily creatinine-normalized THCCOOH concentrations according to group. Urine specimens were collected from cannabis users under continuous medical surveillance during cannabis abstinence for up to 30 days. Cannabis users were separated into three groups, 0–50 (panel A), 51–150 (panel B), and >150 ng/mg (panel C) according to creatinine-normalized THCCOOH concentrations in the first specimen collected at admission. The mean THCCOOH concentration was calculated for each participant each day; the mean concentration for the group was then calculated on a daily basis.

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