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Excretion of Δ9-tetrahydrocannabinol in sweat


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Summary of this paper

(Full Paper Link Below)

Excretion of Δ9-tetrahydrocannabinol in sweat. Our Machine-Learning algorithms scan the text for the most important phrases or passages. These highlights, alongside their respective section titles, are shown below.


Saito et al. reported a validated gas chromatography-mass spectrometry (GC/MS) method with a LOQ of 0.4 ng THC/patch and found concentrations of 0.9 to 3.1 ng THC/patch in several 24-hour sweat patches from one cannabis user [20]. The expected disposition of THC in sweat from chronic cannabis users has not been reported.

Subjects And Study Design

Exact times of dosing were recorded, but target times each day were 0800, 1300 and 1730 h. After five consecutive dosing days, there was a 10-day washout period prior to the next dosing condition. Subjects had five dosing conditions involving placebo, low-dose liquid hemp oil (9 μg/g or a daily dose of 0.39 mg THC), low-dose hemp oil in capsules (92 μg/g or a daily dose of 0.47 mg THC), high-dose hemp oil (347 μg/g or a daily dose of 14.8 mg THC) and dronabinol (2.5 mg/capsule or a daily dose of 7.5 mg THC). Sweat patches were stored at −20°C until THC analysis.

Gc/Ms Analysis

Percent recovery from patches was 44-46%, LOQ was 0.4 ng THC/patch and coefficients of variation were < 10%. All weekly patches were tested. Some daily patches were not tested if no THC was found in the corresponding weekly patch.

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Prior to receiving their first THC dose, frequent cannabis users (Group 2) produced their first negative urine specimen, i.e. less than 10 μg/L, within one to three weeks. During this washout phase, the first weekly sweat patch from two of seven subjects had THC above the assay LOQ. One weekly patch contained 0.93 ng THC/patch, with none of the seven daily sweat patches worn this week positive for THC.


The manufacturer recommends that the patches be worn for one week. In the present study, sweat patches worn by daily cannabis users the first week of monitored abstinence had THC concentrations averaging 3.85 ng/patch. There are no other published studies reporting sweat patch THC concentrations after cessation of use for comparison.


Results of our clinical study indicate that daily cannabis users will excrete THC into sweat in concentrations above the SAMHSA cutoff of 1 ng/patch. During abstinence, negative patches are expected after one week, but some may have a longer washout period of four weeks or more. The sensitivity of sweat patches to detect new drug use following cannabis smoking is not known and requires an independent controlled smoked cannabis administration study.


Marilyn Huestis

University of Maryland School of Medicine – Faculty Member

Professor Dr. Dr. (h.c.) Marilyn A. Huestis recently retired as a tenured senior investigator and Chief, Chemistry and Drug Metabolism Section, National Institute on Drug Abuse, National Institutes of Health, after 23 years of conducting controlled drug administration studies. She is an Adjunct Professor, University of Maryland Baltimore School of Medicine. 


The post Excretion of Δ9-tetrahydrocannabinol in sweat appeared first on Michigan Medical Marijuana.

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