Journal of Analytical Toxicology, Vol. 21, July/August 1997
] Letter to the Editor
A PositiveTHC UrinalysisFrom Hemp (Cannabis) SeedOil
To the Editor:
Most varieties of hemp (i.e., non-drug Cannabis sativa L.) have very low levels of tetrahydrocannabinol (THC), typically
less than 1.0%, although other cannabinoids may still be present in considerable amounts (1). Even though the seed does
not contain measurable amounts of any cannabinoid (2,3), trace amounts of THC have been detected in some samples of
hemp seed oil (4), apparently from the contamination of pressed seed by adherent resin or other plant material.
We would like to report on the possibility of achieving a positive urinalysis for THC metabolite(s) after the modest consumption of commercially available hemp seed oil in Cannabis-naive individuals. Because hemp seed oil is an excellent
source of essential fatty acids (EFAs, i.e., linoleic and linolenic acids) (5), it is sold in some stores as a dietary supplement
for these and other biologically important unsaturated fatty acids. Thus, in the absence of recreational drug use, it may become necessary to consider this source as a viable explanation for cannabinoid metabolites in urine. The importance of this
distinction was recently highlighted in an article that reported a positive urine test for THC metabolites after the consumption of a commercially available snack that contained hemp seeds (6). Considering the lipophilic sequestering of THC and
other cannabinoids, we were interested to know if modest consumption of hemp seed oil would result in a positive urinalysis for THC with standard laboratory methods.
In the present report, two individuals who had not used any other form of Cannabis consumed various amounts of commercially available hemp seed oil, which was purchased from the refrigerated section of health food stores in the Miami
area. Initial urine samples, which were collected before
consumption of any hemp seed oil, gave negative results by
Table II. Experiment 2. UrinalysesSubsequentto the
EMIT.
Acute Administration of 24 Hemp Seed Oil Gelatin
In a chronic experiment (experiment 1), an individual
Capsules*
consumed approximately 10 mUday of hemp seed oil over a
period of 29 days. The oil was never heated or used in
Elapsedtime
EMIT
GC-MS
cooking, but rather applied to food just before consumpSample
Time of day
(h)
(ng/mL)
(ng/mt)
tion. In an acute experiment (experiment 2), another individual consumed 24 hemp seed oil capsules at one time,
1
07:50
2.3
+t
3
2
09:10
3.7
+
10
containing 1000 mg of oil each (24 g of oil total). Subse3
10:00
4.5
+
4
quent urine samples from both individuals gave positive
4
11:15
5.8
+
4
tests for THC.
5
12:10
6.7
+
7
The presence of THC was determined by EMIT and
6
13:30
8.0
+
7
verified by gas chromatography-mass spectrometry
Table I. Experiment 1. UrinalysesAfter Chronic
Administration of Two Brandsof Hemp Seed Oil*
Sample
Day
EMIT
(ng/mL)
GC-MS
(ng/mL)
It
2s
3
4"
25
27
29
32
+*
+
+
+
36
72
87
66
* All urine sampleswere obtained from the first urination of each day.
t- Sample 1 shows THC metabolite levels after the consumption of Brand A after 10
mL/day for 25 days.
:1: Positive samplesexceededthe responsefor a 20-ng/mLcalibration standard.
w Sample 2 shows THC metabolite levels after switching to Brand B at day 27.
II Sample 4 was obtained on day 32 after 3 days of abstinence.
7
8
9
10
11
12
13
14
15
14:45
15:50
17:00
19:50
21:00
05:00
07:50
10:40
12:45
9.3
10.3
11.5
14.3
15.5
23.5
26.3
29.2
31.3
+/-*
+/+
+
+/+/+
+/_s
4
3
7
5
3
4
5
5
3
16
14:30
17
18
17:40
07:55
33.0
-
2
36.2
50.4
-
2
3
* Each capsule contained 1000 mg oil. The entire dose (24 g) was taken at 05:00,
and the first urine samplewas collected at 07:50. Samplesfrom all subsequent
urinations were collected over 50 h.
+ Samplesexceededthe responsefor a 20-ng/mL calibration standard.
:~ Sampleswere of an intermediatevalue.
w Sampleswere equivalent to the negativecalibrator.
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319
Journal of Analytical Toxicology, Vol. 21, July/August 1997
(GC-MS) (7). Nearly 87 ng/rnL of A9-THC-11-carboxylicacid was quantitated by GC-MS after chronic consumption of
the oil (experiment 1), whereas less than 10 ng/mL was quantitated in urine samples from experiment 2.
In experiment 1, THC metabolite levels remained high after consuming 10 mL of oil per day for 25 days (Brand A).
Directly following that period, 10 mL/day of another hemp seed oil (Brand B) was consumed for four additional days, followed by a three-day period of abstinence. These data are presented in Table I and show the highest levels of THC
metabolite, which suggests a cumulative effect after regular consumption, along with the possibility of varying cannabinoid content in different brands of oil.
In experiment 2, the effect from an acute dose of 24 g hemp seed oil in gelatin capsules was followedover a 50-h
period (Table II). In this case, THC metabolites were undetectable after 30 h, and overall metabolite levels were not as
high as in experiment 1.
Low levels of THC, and probably other cannabinoids, apparently contaminate hemp seed oil as a byproduct of the
extraction process. THC levels were recently reported to be 0.025% in a sample of commercial hemp seed oil and
0.375% in oil pressed from a drug variety of Cannabis seed (8), presumably as the orally inactive carboxylicacid. The
same study also reported no THC for oil pressed from either carefully cleaned hemp or drug-Cannabis seeds.
These levels are not sufficient for drug purposes, even if all THC were in an orally active form, and neither volunteer
reported associated psychoactivity in the present study. However,because of the lipophilic nature of THC and other
cannabinoids, bioaccurnulation and subsequent excretion of rnetabolites can result in a positive urine test as determined
by EMIT and GC-MS methodologies.
J.C. Callaway1, R.A.Weeks2, L.P. Raymon3, H.C.Walls3,
and W.L. Hearn 2
1Department of Pharmaceutical Chemistry, Universityof
Kuopio POB 1627, FIN-70211 Kuopio, Finland; 2Dade
County Medical Examiner Department, Number One
Bob Hope Road, Miami, Florida 33136; and 3Department
of Pathology, Forensic ToxicologyLaboratory, 12500 SW
152nd Street, Building B, Miami, Florida 33177
References
1. E. de Meijer, H. Van der Kamp, and F. Van Eeuwijk. Characterisation of Cannabis accessions with regard to cannabinoid content
in relation to other plant characters. Euphytica 62:187-200 (1992).
2. Botany: the unstabilized species. In Marihuana in Science and Medicine. M. Paris and G.G. Nahas, Eds. Raven Press, NY, 1984.
pp 3-36.
3. J.E. Viera, L.C. Abreu, and J.R. Valle. On the pharmacology of hemp seed oil. Med. Pharmacol. Exp. (Int. J. Exp. Med.) 16:219-24
(1967).
4. T. Matsunaga, H. Nagatomo, I. Yamamoto, and H. Yoshimura. Identification and determination of cannabinoids in commercially
available Cannabis seed. Eisei Kagaku 36(6): 545-47 (1990).
5. M.S. Manku. Clinical biochemistry of essential fatty acids. In Omega-6 Essential Fatty Acids: Pathophysiology and Roles in
ClinicalMedicine, D.F. Horrobin, Ed. Alan R. Liss, New York, NY, 1990. pp 21-53.
6. Snack causes marijuana-positive drug tests. MRO Update, October 1996. p 3.
7. R. Clouette, M. Jacob, R Koteel, and M. Spain. Confirmation of 11-nor-A9-tetrahydrocannabinol in urine as its t-butyldimethylsilyl derivative using GC/MS. J. Anal. Toxicol. 17:1-4 (1993).
8. I. B6csa and P. M~th~. Can cannabinoids occur in hemp seed oil? J. Int. Hemp Assoc. 2(2): 59 (1995).
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