The Marijuana Detection Window - National Drug Court Institute

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NATIONAL DRUG COURT INSTITUTEGenerally speaking, the following factorsaffect the marijuana detection windowaccordingly:• Drug DoseThe higher the dose; the longer the detectionwindow. The percentage of psychologicallyactive delta-9 THC in marijuana plant materialvaries considerably, making dosage difficultto estimate.• Route of EntryInhalation (smoking) is the only route ofadministration to be evaluated in this review.• Duration/Frequency of UseThe longer the duration and the greater thefrequency of cannabinoid usage (chronic);the greater the body storage of fat-solublemetabolites; the longer the cannabinoiddetection window. Drug surveillance programsmay be able to define use patternsbased on client self-reporting, arrest reports,documentation of previous treatment, orother court records.• Metabolism RateThe higher the metabolic functions of the client;the faster cannabinoids are broken down;the shorter the detection window. Monitoringprograms cannot determine this parameter.• Test SensitivityThe lower the cutoff concentration; the moresensitivity the testing method toward cannabinoids;the longer the detection window. Courtstaff can select between various cannabinoidtesting cutoffs.• Test SpecificityThe less specific the testing method; thegreater number of cannabinoid metabolitesdetected; the longer the detection window.This is difficult for monitoring programs toassess without technical assistance.Of these variables, drug courts are effectivelylimited to controlling only the sensitivity ofthe drug test itself (i.e., cutoff concentration).Initial screening test cutoffs for cannabinoidsin urine generally include thresholds at 20, 50,and 100 ng/mL. The choice of testing cutoffhas a profound effect on the cannabinoiddetection window. The only other factor thatcan assist the court in the interpretation ofcannabinoid testing results and the estimationof a client’s detection window is attemptingto define the duration and extent of a client’smarijuana use over time (acute or chronic).The differentiation between acute (a singleuse event or occasional use) versus chronic(persistent, long-term, continued usage) isimportant to establishing reliable detectionbenchmarks. As a result, drug court practitionersshould attempt to gather as much informationas they can about client drug use behaviorand patterns.Finally, the detection window by its verynature is subject to the timing of eventsoutside the purview of the court. The last useof marijuana by a client prior to a positive testis often unknown to drug court staff. Thus,the real interval between drug usage andfirst detection can rarely be ascertained.For example, if a client smoked marijuana onMonday and a urine sample collected onFriday produced a positive result, the windowof detection is 4 days shorter than if that sameclient had smoked on Thursday and produced apositive cannabinoid test on Friday. Therefore,the actual detection window for marijuana willalmost always be longer than the analyticallyderived detection window as determined viapositive tests.RESEARCH REVIEWResearch associated with the detection windowof cannabinoids in urine spans several decades.While these studies have produced a significantamount of valuable information aboutmarijuana elimination, older studies (primarilythose performed in the 1980’s) have alsoyielded some unintended consequences aspertains to the detection window. The technologiesof drug testing and the methodologiesused in drug detection have advanced rapidlyin recent years. Consequently, cannabinoiddetection studies performed twenty yearsago (employing older immunoassays methods)utilized drug testing methods that are eitherno longer in widespread use or assays thathave been extensively reformulated.As cannabinoid screening tests evolved, theseimproved assays became more selective inthe manner in which they detected marijuanametabolites (breakdown products). As detection4
DRUG COURT PRACTITIONER FACT SHEETTable 1. Review of Cannabinoid Studies Reporting Long Detection TimesMaximumDetection TimesDetermined forCannabinoidsFactors Potentially Affecting the Relevanceof Study Findings to Cannabinoid DetectionWindow InterpretationYearAuthor36 days Retrospective case study of a single patient; reporton 6 similar cases included; no testing data providedin publication; no cannabinoid cutoff given37 days 27 subjects studied, no testing data provided in publication;cannabinoid cutoff not provided; “calculated” cannabinoidcutoff less than 10 ng/mL; 37 day detection derived from95% confidence interval for calculated elimination half-life;actual length of positivity averaged 9.7 days (5-20 days);authors acknowledge subjects may have been able toobtain marijuana during study; possibility supported bystaff monitoring subjects40 days 10 subjects studied; self-reported as chronic users; subjectshoused on unrestricted drug treatment ward; marijuanause during study suspected by authors and confirmed byseveral subjects67 days 86 subjects studied; self-reported as chronic users; subjectstreated on “closely supervised” ward; single case of anindividual’s time to last positive urine (at or above 20 ng/mL) of 67 days (77 days to drop below the cutoff calibratorfor ten consecutive days); spikes in urine cannabinoidlevels during the study are not explained by the authors25 days 11 subjects studied for cannabinoid elimination patterns(70 participants in entire study); only one subjectremained positive for 25 days; mean elimination forself-reported “heavy” users was 13 days; immunoassayused in study not commercially available since 1995.25 days 13 subjects studied; self-reported as chronic users; subjectabstinence not supervised during study; subjects allowedto smoke marijuana before and on the day of test drugadministration; only one subject tested positive beyond14 days25 days Subject detection times determined using methods witha 5 ng/mL cannabinoid cutoff concentration32 days 19 subjects studied - half withdrew from study prior tocompletion; subjects were prisoners housed in generalpopulation with no additional surveillance; participantsnot asked to report new drug use during study; marijuanause during study suspected by authors1982 Dackiset al.1983 Cridlandet al.1984 Swatek1985 Ellis et al.1985 Schwartzet al.1989 Johansson& Halldin1994 Iten1999 Smith-Kiellandet al.5
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