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Try out PMC Labs and tell us what you think. Learn More. There were statistically ificant correlations between groups and of days until first negative and last positive urine specimens; mean of days were 0. These data provide guidelines for interpreting urine cannabinoid test and suggest appropriate detection windows for differentiating new cannabis use from residual drug excretion. Cannabis continues to be the most widely used illicit drug in the United States and in many countries around the world 1 , and is the most commonly detected drug of abuse in workplace urine drug tests 2. An important issue for drug-testing programs is the ability to distinguish recent cannabis use from residual drug excretion.
Exceptionally long detection times have been reported for cannabinoid metabolites in the urine of frequent drug users during abstinence 4 — 8. During the terminal elimination phase, an individual may produce consecutive specimens that test positive, negative, and positive again over time.
This makes interpretation of cannabinoid urine drug test difficult if it is necessary to determine whether positive are indicative of new drug use or reflective of cannabis exposure. Detection time is dependent on pharmacological factors e. Ellis et al. Hawks 10 first proposed adjusting urinary cannabinoid concentrations to for urine dilution.
Manno et al. Huestis and Cone 12 tested this hypothesis in an experiment with controlled THC dosing, collection of all individual urine voids, and residence of participants on a secure research unit throughout the study. These investigators demonstrated that the most accurate differentiation between new cannabis use and residual cannabinoid excretion occurred if this ratio was greater than 0.
The prediction model required a minimum of 24 hours between specimens and provided false negative and false positive rates for different cutoffs to permit drug-testing administrators to select the most appropriate cutoff based on the goals of the program. The aim for the present study was to determine the time course of urinary THCCOOH excretion under monitored abstinence, to better understand patterns of residual cannabinoid excretion and to improve predictions of new cannabis use from urine cannabinoid tests.
Participants included daily and non-daily cannabis smokers. All participants provided written informed consent and were financially compensated for time and inconvenience. Before inclusion, each participant underwent thorough medical physical exam, ECG, blood, and urine chemistries and psychological evaluations, including past and recent drug use history.
All subjects in this study were required to have normal serum creatinine 0. Twenty-four hour medical surveillance prevented access to unauthorized licit or illicit drugs. In addition, random urine drug tests for amphetamines, cannabinoids, cocaine, opiates, and phencyclidine were performed. All individual urine voids were collected ad libitum for up to 30 days. Each urine void was collected in a polypropylene container and refrigerated immediately after urination.
Specimens were thawed just prior to analysis and subjected to only a single freeze-thaw cycle. A modified Jaffe method on an automated clinical analyzer was used to obtain urine creatinine concentrations Data were analyzed to assess which independent variables were predictive of each dependent variable. Independent variables included normalized THCCOOH concentration in the first specimen, average of ts smoked per day, of days used during the last 14 days, days since last use, years of use, body mass index BMI , sex, age, and age at first use.
For each dependent variable, a frequency histogram and scatter plot were created to assess if data were normally distributed. None of the non-log transformed dependent variables were found to be normally distributed. Only the main effect of each independent variable, without interaction terms, was used in the stepwise regression analysis.
Correlations between group and mean values of several dependent variables were graphed and linear correlation coefficients determined Microsoft Office Excel , SP1. Sixty cannabis users 50 African Americans, 5 Caucasians, 3 Hispanics, 1 mixed race, and 1 American Indian , who self-reported daily to weekly cannabis smoking, participated in this residential study of urinary cannabinoid excretion Table 1.
Forty-six males and 14 females with a mean age of Subjects began using cannabis at a mean of Correlation coefficients were determined for the mean interval to the first day with a negative specimen Figure 1. Urine specimens were collected from cannabis users under continuous medical surveillance during cannabis abstinence for up to 30 days: 1. Urine specimens were collected from cannabis users under continuous medical surveillance during cannabis abstinence for up to 30 days. Mean detection rates on the day of the first negative specimen were The mean creatinine-corrected urine concentration for each subject for each day was determined, and the mean for each group for each day was calculated.
Concentrations decreased rapidly during the first three days of monitored abstinence followed by a more gradual reduction over the course of the residential stay. The mean THCCOOH concentration was calculated for each participant each day; the mean concentration for the group was then calculated on a daily basis. The aim of the present research was to characterize the time course of THCCOOH elimination in urine following variable cannabis exposure to provide data for improved interpretation of urine cannabinoid tests. Cannabinoid metabolites have been detected in the urine of frequent cannabis users for prolonged periods during abstinence 4 — 8.
During the terminal elimination phase, alternate positive and negative urine test may occur in consecutive specimens. This makes it problematic to determine whether positive are indicative of new drug use or reflective of cannabis exposure.
Complicating this issue is the fact that there are few studies in which participants are continuously monitored during abstinence to ensure that no illicit drug use has occurred. This study was unique in that it was conducted on a closed research unit with subjects under continuous medical surveillance during cannabis abstinence for up to 30 days. BMI was ificantly correlated with the day of the last positive specimen; i. BMI is a surrogate measure of body adiposity. THC distributes into fat tissue due to its lipophilicity and creates a depot of THC in the body after frequent cannabis use.
Thus, the ificant correlation between BMI and time until last positive urine cannabinoid test. During abstinence, the release of THC from adipose tissue into the blood is highly variable, possibly based on differences in activity, diet, enzymatic activity and other undetermined factors. This release causes fluctuations in blood concentrations that in turn lead to variability in urinary cannabinoid concentrations. Thus, the many poorly studied factors that affect redistribution of THC from adipose tissue, and excretion into urine can result in ificant intra-subject variability of creatinine normalized urinary THCCOOH concentrations.
The higher the creatinine-corrected THCCOOH concentration of the first specimen, the longer the mean interval for the first negative and last positive urine specimen. Intervals prior to the first negative urine specimen ranged from 0 — 16 days after admission; the range for the last positive specimen was 0 — 30 days. The creatinine corrected THCCOOH concentration was positively associated with the of days, of specimens, and C max for specimens collected between the first negative and last positive urine tests.
For 4 of these subjects, this last day of observation represented the 30 th day of monitored drug cessation. Despite this initial low cannabinoid concentration, the last positive urine cannabinoid test occurred on average 4. Thus, the initial normalized THCCOOH concentration is an important factor in determining the time course of urinary cannabinoid excretion. Regardless of the initial concentration, a rapid decrease was seen during the first three days of monitored abstinence followed by a more gradual decrease in concentration during subsequent days.
These urinary cannabinoid excretion data collected under controlled monitored conditions from 60 cannabis users are of value for establishing expected windows of drug detection for the first negative and last positive cannabinoid tests. Furthermore, maximum creatinine-normalized THCCOOH concentrations that should be expected in later urine specimens are suggested, also helping to differentiate new cannabis use from residual drug excretion.
Also, the detection rate data provide insight into the probability of obtaining a positive or negative result on each day after the first negative specimen. This study monitored cannabis users on a closed research unit under continuous medical surveillance during cannabis abstinence for up to 30 days. The greater the creatinine corrected initial THCCOOH concentration, the greater the interval until the first negative and last positive specimens, the greater the window of drug detection and the higher the detection rate of positive specimens.
These data increase our understanding of THCCOOH urinary elimination and provide guidelines for the interpretation of urine cannabinoid test . They also suggest appropriate detection windows for differentiating new cannabis use from residual drug excretion based on creatinine normalized THCCOOH urine data.
National Center for Biotechnology Information , U. J Anal Toxicol. Author manuscript; available in PMC Oct 1. Robert S. Goodwin , 1 William D. Darwin , 1 C. William D. Nora Chiang. Marilyn A. Author information Copyright and information Disclaimer. Huestis, Ph. Suite 05A, Baltimore, MD E-mail: vog.
Copyright notice. The publisher's final edited version of this article is available at J Anal Toxicol. See other articles in PMC that cite the published article. Introduction Cannabis continues to be the most widely used illicit drug in the United States and in many countries around the world 1 , and is the most commonly detected drug of abuse in workplace urine drug tests 2. Specimen collection and analysis Each urine void was collected in a polypropylene container and refrigerated immediately after urination.
Statistics Data were analyzed to assess which independent variables were predictive of each dependent variable. Open in a separate window. Figure 1. Figure 2. Figure 3. Discussion The aim of the present research was to characterize the time course of THCCOOH elimination in urine following variable cannabis exposure to provide data for improved interpretation of urine cannabinoid tests.
Conclusions This study monitored cannabis users on a closed research unit under continuous medical surveillance during cannabis abstinence for up to 30 days.Marijuana urinalysis detection times
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