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Differentiating New Cannabis Use From Residual Urinary Cannabinoid Excretion

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

Author(s) Schwilke EW, Gullberg RG, Darwin WD, Chiang CN, Cadet JL, Gorelick DA, Pope HG, Huestis MA
Institution Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Biomedical Research Center, Baltimore, MD 21146, USA.
Source Addiction 2011 Mar; 106(3):499-506.
MeSH Adult
Chronic Disease
Diagnosis, Differential
Drug Residues
Gas Chromatography-Mass Spectrometry
Marijuana Abuse
Models, Biological
Nonlinear Dynamics
Predictive Value of Tests
Psychotropic Drugs
Substance Abuse Detection
Time Factors
Young Adult
Abstract To develop and validate empirically a mathematical model for identifying new cannabis use in chronic, daily cannabis smokers.Models were based on urinary creatinine-normalized (CN) cannabinoid excretion in chronic cannabis smokers.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.A total of 48 (model development) and 67 (model validation) daily cannabis smokers were recruited.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.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.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.
Language eng
Pub Type(s) Journal Article
Research Support, N.I.H., Extramural
Research Support, N.I.H., Intramural
Validation Studies
PubMed ID 21134021

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