The Marijuana Detection Window - National Drug Court Institute

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NATIONAL DRUG COURT INSTITUTEspecificity increased, the length of timecannabinoids were being detected in urinedecreased. The greater the cannabinoid testingspecificity, the shorter the detection window.Studies have demonstrated that detectiontimes of cannabinoid metabolites in urinemonitored by immunoassay have decreasedover the past two decades (Huestis, 2002;Huestis, Mitchell, & Cone, 1994). Therefore,the results of cannabinoid eliminationinvestigations performed in the 1980’s mayno longer be applicable to estimating thedetection window for marijuana in urine usingtoday’s testing methodologies. Not to mentionthat twenty years ago, the routine use ofon-site drug testing devices was nonexistent.Studies of chronic marijuana users reportingprolonged cannabinoid excretion profiles haveprovided the basis for the common assumptionthat marijuana can be detected in urinefor weeks or even months following use. Ingeneral, cannabinoid elimination studies thathave manifested exceptionally long detectiontimes suffer from a variety of research designshortcomings that raise concerns about theirusefulness in establishing a reliable cannabinoiddetection window for use in the moderndrug court movement. Table I examinessome of the potentially limiting factors fromstudies that produced prolonged cannabinoiddetection times.The detection window for cannabinoidsin urine must be seen in the propercontext-as a reasonable estimate.The research studies presented in Table 1contain numerous design details that confoundthe use of the data presented in establishinga reasonable and pragmatic cannabinoiddetection window for drug court proceedings.The most serious of these obfuscating factorsis the inability to assure marijuana abstinenceof the subjects during the studies. The adverseeffect of this flaw on determining the truecannabinoid elimination time after marijuanacessation is significant. Drug use during anelimination study would extend the durationcannabinoids would be detected in the urineof subjects and would produce inaccuratelylong detection windows. In several cases, theauthors themselves in their own review ofresults raise this concern. Other study designissues that may limit their usefulness includethe use of detection methods with cannabinoidcutoff concentrations far below those traditionallyutilized in criminal justice programs, theuse of testing methods no longer commerciallyavailable and the use of immunoassay drugtests with reduced cannabinoid specificity (ascompared with current immunoassay testingmethods). It is not the intention of this articleto discredit these studies, but rather to illustratethe degree to which their prolongedcannabinoid detection findings have influencedthe understanding of the length of timecannabinoids can be detected in urine.This critical evaluation (Table 1) is not presentedto imply that these peer-reviewed articlesare unscientific or contain no information ofprobative value. It is insufficient, however, tomerely read the abstract of a scientific paperor the findings of a research study and drawthe conclusion that a drug court client canremain positive for 30 days or longer, basedupon the longest cannabinoid detection timereported therein. The data from these studiesare often misused to make such claims.Despite the potential limitations affecting theinterpretation of the data produced by thestudies in Table 1, the research does presentsome general cannabinoid elimination trendsworth further examination. A closer evaluationof the study by Smith-Kielland, Skuterud, &Morland indicates that even with the factorsidentified as limiting its relevance, the averagetime to the first negative urine sample ata cannabinoid cutoff of 20 ng/mL was just 3.8days for infrequent users and only 11.3 daysfor frequent users (1999). In the Swatek study,eight out of ten chronic subjects tested belowthe 50 ng/mL cutoff after an average of only6
DRUG COURT PRACTITIONER FACT SHEET13 days (range 5-19 days) (1984). Johanssonand Halldin identified only one study subjectthat tested positive for longer than 14 dayswith all thirteen subjects having an averagelast day with detectable levels (using a 20ng/mL cutoff) of 9.8 days (1989). In otherwords, despite the potential factors restrictinginterpretation, those study subjects withexceptionally long cannabinoid detection times(30-plus days) were just that—exceptional.In several of the studies presented in Table 1,only a single subject was the source of themaximum cannabinoid detection time.Unfortunately, these rare occurrences havehad a disproportional influence on the overallcannabinoid detection window discussion ina manner that has led to the general assumptionthat 30-plus day detection times areroutine in drug court clients—regardless ofuse patterns (chronic vs. acute). Moreover,this prolonged elimination assumption andits widespread use as exculpatory evidencehas most likely fostered client denial andhindered legitimate sanctioning efforts.By contrast, the research associated with acutemarijuana usage and resulting cannabinoiddetection window is considerably morestraightforward and less contentious. In a 1995study using six healthy males (under continuousmedical supervision), Huestis, Mitchell,& Cone determined that the mean detectiontimes following a low dose marijuana cigaretteranged from 1 to 5 days and after a high dosecigarette from 3 to 6 days at a 20 ng/mLimmunoassay cutoff concentration (average2.1 days and 3.8 days, respectively) (1995).They also concluded that immunoassays atthe 50 ng/mL cannabinoid cutoff provide onlya narrow window of detection of 1-2 daysfollowing single-event use. In 1996, Huestiset. al. published research focusing on carboxy-THC, the cannabinoid metabolite most oftenidentified by gas chromatography/massspectrometry (GC/MS) confirmation methods.Using the 15 ng/mL GC/MS cutoff, the detectiontime for the last positive urine sample(for six subjects following high dose smoking)was 122 hours—just over five days. In 2001,Niedbala et. al. demonstrated similar resultswith 18 healthy male subjects following thesmoking of cigarettes containing an averageTHC content of 20-25 mg. Analyzing urinesamples at a 50 ng/mL immunoassay cutoffyielded an average cannabinoid detectiontime of 42 hours. These acute marijuanaelimination studies conclude that after singleusage events cannabinoids are detected inurine for no more than a few days.While studies of the cannabinoid detectionwindow in chronic substance users havebeen more difficult to accomplish, researchprotocols have been developed to overcomeconcerns about marijuana usage during thestudy. Using a well-crafted study design,Kouri, Pope, & Lukas in 1999 determined thecannabinoid elimination profiles of 17 chronicusers. Subjects were selected after reportinga history of at least 5000 separate “episodes”of marijuana use in their lifetime (the equivalentof smoking once per day for 13.7 years)plus continuing daily usage. Abstinence duringthe 28-day study was ensured by withdrawingthose subjects whose normalized urinecannabinoid levels (cannabinoid/creatinineratio) indicated evidence of new marijuana use.Kouri, et al, found that five of the 17 subjectsreached non-detectable levels (less than 20ng/mL) within the first week of abstinence,four during the second week, two during thethird week and the remaining six subjectsstill had detectable cannabinoid urinary levelsat the end of the 28-day abstinence period.Unfortunately, analytical results related to thecannabinoid testing in the article were scantas the primary objective of the study was toassess changes in aggressive behavior duringwithdrawal from long-term marijuana use.Even though this represents one of the beststudies of chronic marijuana users, interpretationof this data for cannabinoid eliminationpurposes is limited because the actual drugtesting data is not available. Nonetheless,Kouri, et al, shows that after at least 5000marijuana smoking episodes, 30-day eliminationtimes are possible.7
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