SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

M38
Ll9-TETRAHYDROCANNABINOL (THC) IN SWEAT PRIOR TO AND FOLLOWING
CONTROLLED ORAL ADMINISTRATION OF HEMP OIL AND MARINOLTM TO CANNABIS
USERS
Abraham T. Wtsadik 1 *, Karl Scheidweilerl,Takeshi Saito), Richard A. Gustafson 2 , Eric T. Moolchan 1 and
Marilyn A. Huestis l : IChemistry and Drug Metabolism, IRP, NInA, NIH, 5500 Nathan Shock Drive,
Baltimore, MD 21224, 2Jacksonville Naval Air Station, Adams Avenue, Jacksonville, FL 32212
3Department of Forensic Medicine, Tokai University School of Medicine Bohseidai, Isehara, Kanagawa
259-1193 Japan
Six healthy individuals with a history of cannabis use resided on the secure clinical research unit of the
Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health for the 10 to
12 week study. Participants provided informed consent for this Institutional Review Board-approved oral
cannabinoid administration protocol. This was a randomized, double blind, double dummy, placebocontrolled
within-subject study. Sweat was collected throughout the study with PharmCheck sweat
patches worn for 24 hours or 7 days. The initial washout phase of this study lasted from admission until
subjects' urine cannabinoid concentrations were below 10 ng/mL by fluorescence polarization
immunoassay. Sweat patches worn during the initial washout phase enabled investigation of excretion of
THC resulting from previously self- administered cannabis. The dosing phase of the study followed the
initial washout phase, during which the participants were dosed three times a day for five consecutive days
followed by a ten-day washout period before the next dosing session. All subjects ingested commercially
available hemp seed oil of differing THC concentrations: 0, 0.39, 0.47 (contained within capsules), and
14.8 mg THC/day. In addition, 7.5 mg/day dronabinol or Marinol, was administered as a positive control.
PharmChek sweat patches collected throughout the study were frozen at _20DC until analysis. Patches
were extracted in methanol: 0.2M sodium acetate buffer, pH 5.0, 3:1 v/v, followed by solid phase
extraction using Clean Screen, ZSTHC020, (United Chemical Technologies, Bristol, PAl. Dried extracts
were derivatized with trifluoroacetic acid (TFAA) and analyzed using gas chromatography negative
chemical ionization mass spectrometry (GC-NCI-MS) for THC. Daily and weekly sweat patches collected
during the initial washout period were analyzed along with weekly patches collected during and following
dosing. None of the patches worn during or following dosing tested positive for THC with a cutoff of 0.4
ng/patch. Patches worn during the first week of residence on the research unit, reflecting drug excretion
from previously self-administered cannabis tested positive for THC in two individuals. The concentrations
of THC were 0.51 and 0.82 ng THC/patch for patches worn for the first seven days on the research unit.
These participants self-reported cannabis smoking an average of 3.0 and 4.5 days per week and claimed to
have last used cannabis one to two days prior to study enrollment. However, these usage histories did not
differ significantly from those reported by the other four subjects and whose sweat patches tested negative
for THC. In conclusion, this study demonstrates that oral administration ofTHC at, as high a dose as 14.8
mg/day for 5 consecutive days did not produce positive sweat tests for cannabinoids with a 0.4 ng
THC/patch cutoff in patches worn for seven days. The cannabinoid confirmation cutoff for THC in sweat
as proposed by the Substance Abuse Mental Health Services Administration is 1 ng THC/patch. It is
important to note that the bioavailability of oral THC has been estimated to be 6 to 20% and plasma THC
concentrations did not exceed 6.5 ng/mL following any of the dosing regimens during this study. These
data indicate that previously administered THC in daily cannabis smokers did not produce positive
cannabinoid sweat tests when patches were applied at the beginning of abstinence and worn for 7 days if a
1.0 ng THC/patch cutoff is used. In addition, no sweat patches were positive at this cutoff when up to 14.8
mg THC/day for 5 consecutive days was ingested by cannabis users. Ingestion of commercially available
hemp oil products and Marinol up to 7.5 mg/day did not produce positive sweat cannabinoid tests.
Keywords: /':,.9-Tetrahydrocannabinol, Oral Cannabinoids, Sweat Patch
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