Marijuana Research Today is a free monthly online journal that collates and summarizes the latest research about Marijuana, including details on benefits, cancer, effects, uses, addiction. | ||||||||
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Excretion of Delta9-tetrahydrocannabinol in sweat.Huestis MA, Scheidweiler KB, Saito T, Fortner N, Abraham T, Gustafson RA, Smith ML Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA. mhuestis@intra.nida.nih.gov Sweat testing is a noninvasive technique for monitoring drug exposure over a 7-day period in treatment, criminal justice, and employment settings. We evaluated Delta(9)-tetrahydrocannabinol (THC) excretion in 11 daily cannabis users after cessation of drug use. PharmChek sweat patches worn for 7 days were analyzed for THC by gas chromatography-mass spectrometry (GC/MS). The limit of quantification (LOQ) for the method was 0.4 ng THC/patch. Sweat patches worn the first week of continuously monitored abstinence had THC above the United States Substance Abuse Mental Health Services Administration's proposed cutoff concentration for federal workplace testing of 1 ng THC/patch. Mean+/-S.E.M. THC concentrations were 3.85+/-0.86 ng THC/patch. Eight of 11 subjects had negative patches the second week and one produced THC positive patches for 4 weeks of monitored abstinence. We also tested daily and weekly sweat patches from seven subjects who were administered oral doses of up to 14.8 mg THC/day for five consecutive days. In this oral THC administration study, no daily or weekly patches had THC above the LOQ; concurrent plasma THC concentrations were all less than 6.1 microg/L. In conclusion, using proposed federal cutoff concentrations, most daily cannabis users will have a positive sweat patch in the first week after ceasing drug use and a negative patch after subsequent weeks, although patches may remain positive for 4 weeks or more. Oral ingestion of up to 14.8 mg THC daily does not produce a THC positive sweat patch test. Published 14 January 2008 in Forensic Sci Int, 174(2): 173-7.
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