Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Mar;106(3):499-506.
doi: 10.1111/j.1360-0443.2010.03228.x. Epub 2010 Dec 6.

Differentiating new cannabis use from residual urinary cannabinoid excretion in chronic, daily cannabis users

Eugene W Schwilke  1 , Rod G Gullberg, William D Darwin, C Nora Chiang, Jean Lud Cadet, David A Gorelick, Harrison G Pope, Marilyn A Huestis
Affiliations

Differentiating new cannabis use from residual urinary cannabinoid excretion in chronic, daily cannabis users

Eugene W Schwilke et al. Addiction. 2011 Mar.

Abstract

Aims: To develop and validate empirically a mathematical model for identifying new cannabis use in chronic, daily cannabis smokers.

Design: Models were based on urinary creatinine-normalized (CN) cannabinoid excretion in chronic cannabis smokers.

Setting: For model development, participants resided on a secure research unit for 30 days. For model validation, participants were abstinent with daily observed urine specimens for 28 days.

Participants: A total of 48 (model development) and 67 (model validation) daily cannabis smokers were recruited.

Measurements: All voided urine was collected and analyzed for 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) by gas chromatography-mass spectrometry (GCMS; limit of quantification 2.5 ng/ml) and creatinine (mg/ml). Urine THCCOOH was normalized to creatinine, yielding ng/mg CN-THCCOOH concentrations. Urine concentration ratios were determined from 123,513 specimen pairs collected 2-30 days apart.

Findings: A mono-exponential model (with two parameters, initial urine specimen CN-THCCOOH concentration and time between specimens), based on the Marquardt-Levenberg algorithm, provided a reasonable data fit. Prediction intervals with varying probability levels (80, 90, 95, 99%) provide upper ratio limits for each urine specimen pair. Ratios above these limits suggest cannabis re-use. Disproportionate numbers of ratios were higher than expected for some participants, prompting development of two additional rules that avoid misidentification of re-use in participants with unusual CN-THCCOOH excretion patterns.

Conclusions: For the first time, a validated model is available to aid in the differentiation of new cannabis use from residual creatinine-normalized 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (CN-THCCOOH) excretion in chronic, daily cannabis users. These models are valuable for clinicians, toxicologists and drug treatment staff and work-place, military and criminal justice drug-testing programs.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest:

This research was supported by the Intramural Research Program, National Institutes of Health, National Institute on Drug Abuse, Contract N01DA-1–8817 to BRCI and by NIDA grants RO1–06522 and R01- DA10346 to Dr. Pope. All coauthors report no competing interests.

Figures

Figure 1
Figure 1
Figure 2
Figure 2
Figure 3
Figure 3
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. UNODC. World Drug Report. 2009. pp. 1–314.
    1. Smith ML, Barnes AJ, Huestis MA. Identifying New Cannabis Use with Urine Creatinine-Normalized THCCOOH Concentrations and Time Intervals Between Specimen Collections. J Anal Toxicol. 2009;33:185–9. - PMC - PubMed
    1. Smith-Kielland A, Skuterud B, Morland J. Urinary Excretion of 11-nor-9-carboxy-delta-9-tetrahydrocannabinol and cannabinoids in frequent and infrequent drug users. J Anal Toxicol. 1999;23:323–332. - PubMed
    1. Goodwin RS, Darwin WD, Chiang CN, et al. Urinary Elimination of 11-Nor-9-Carboxy-Δ9-tetrahydrocannabinol in Cannabis Users During Continuously Monitored Abstinence. J Anal Toxicol. 2008;32:562–6. - PMC - PubMed
    1. Lowe R, Abraham T, Darwin W, et al. Extended Urinary delta 9 Tetrahydrocannabinol Excretion in Chronic Cannabis Users Precludes Use as a Biomarker of New Drug Exposure. Drug Alcohol Depend. 2009;105:24–32. - PMC - PubMed

Publication types

MeSH terms