All five cannabinoids were detected. Seventy‐seven percent of heavy users, 39% of light users and 0% of non‐users tested positive for THC. The sensitivity of detection of THC was 0.77 (0.56–0.91) comparing heavy cannabis smokers with light and non‐users, whereas the sensitivity of other cannabinoids generally was considerably lower. The positive and negative predictive value of detection of THC were 0.57 (0.39–0.74) and 0.91 (0.82–0.97), respectively. A correlation of 0.52 (P < 0.001) was observed between self‐reported monthly cannabis use and THC.
Samples were analysed at Alere Toxicology, Cardiff. Two 1 mL methanol washes were performed on the hair with each wash being removed to waste. An additional aliquot of methanol was added and the tubes placed in an unheated ultrasonic bath overnight. Following ultrasonication, the hair sample extract was then placed in a clean test tube. Sodium hydroxide (1 M) was added to the residual hair sample. The sample was placed in a water bath at 80 °C for 30 min. Following cooling the drugs were extracted with chloroform/isopropanol (9:1 v/v) with solid ammonium sulphate (approximately 1 g) added to each sample. After centrifugation, the aqueous layer was aspirated to waste and the solvent layer decanted into the tube containing the original methanol extract. Following addition of 100 μL 0.2 M hydrochloric acid in methanol, the extract was dried under vacuum. The dried extract was reconstituted in ELISA buffer and submitted to solid phase extraction prior to instrumental analysis.
Cannabinoids in hair: sample preparation
Taylor, M. , Lees, R. , Henderson, G. , Lingford‐Hughes, A. , Macleod, J. , Sullivan, J. , and Hickman, M. (2017) Comparison of cannabinoids in hair with self‐reported cannabis consumption in heavy, light and non‐cannabis users . Drug and Alcohol Review , 36 : 220–226. doi: 10.1111/dar.12412. [PMC free article] [PubMed] [Google Scholar]
All data generated or analyzed during this study are included in this published article.
Cannabis Sativa is a plant species of Cannabis. In addition to its recreational use as a drug of abuse, the plant has widespread alternative uses including the production of food, cosmetics (hemp), textiles and medicinal applications 1 . When toxicology laboratories are required to investigate past exposure to cannabis, analysis of hair can provide powerful evidence. The compounds usually targeted for hair analysis to identify cannabis exposure are: Δ(9)-tetrahydrocannabinol (THC), the main active compound of cannabis, the metabolite [11-nor-Δ(9)-tetrahydrocannabinol-9-carboxylic acid (THC-COOH)] and two cannabinoids (cannabinol (CBN) and cannabidiol (CBD)) 2 . Typically passage of these cannabinoids into the hair includes passive diffusion from blood, diffusion from sweat/sebum or external contamination. One of the key questions to be addressed when interpreting the results of cannabinoid hair analysis is that of proof of consumption. Are the results sufficiently clear to suggest cannabis was consumed, or could the results actually be the result of passive exposure to cannabis smoke, or other mechanisms? Passive exposure is defined by an individual being in an environment that is exposed to drugs, an important public health problem. Cannabis smoke can be inhaled or absorbed into the hair by persons other than the intended smoker/user 3 . Researchers have evaluated second-hand cannabis smoke exposure and the corresponding levels of cannabinoids in biological samples 3 , 4 . Herrmann et al. discovered that in unventilated, confined conditions cannabinoid detection was above threshold and higher concentrations of THC and THC-COOH were found predominantly in the blood, urine and hair 4 . THC and THC-COOH have lower incorporation rates in hair in comparison to other bodily matrices. The low presence of THC may be explained by its weak affinity to melanin while the acidic nature of hair may be the reason for the absence of THC-COOH 5 . Along with the levels of cannabis constituents detected in passive exposure, analysis has been conducted to understand what physiological impact exposure has 3 . Past research has shown evidence of increased heart rate and minor impairments in coordination and memory 4 , 6 , 7 . Identification of THC/CBN/CBD in hair suggests exposure to cannabis, which could be due to low level or infrequent use of cannabis or historic or passive exposure. However, some argue that the presence of cannabinoids in hair, especially THC is indicative of repeated or chronic exposure 5 , 8 . The distinction between external contamination and consumption can be difficult for cannabinoid hair analysis 9 , and the implication of a positive test result can have significant consequences for the individual involved. THC-COOH is only formed inside the body, and the presence of this gives unequivocal proof of consumption when detected in hair samples. The metabolite has never been discovered in cannabis smoke ruling out environmental contamination 10 . With hair analysis, THC-COOH is detectable at very low concentrations. The drawbacks for detection from this biological matrix are the requirement for expensive instrumentation and sample preparation can be a more time-consuming process when compared to urine 11 . Routine laboratory screening of hair for cannabis varies and includes the detection of cannabinoids and/or THC-COOH 8 . Hemp is a variety of Cannabis Sativa and is closely related to Cannabis with the difference being in the percentage of THC 12 . Hemp is grown for industrial use and found in food, lotions, medicines, clothing and construction materials. Hemp oil is extracted by pressing the seeds from the female hemp plant 13 . The legalisation of hemp has caused controversy. This is because research has shown that the use or consumption of hemp products could have the potential to impact on drug testing for cannabis 14 .
In this paper we investigate direct hemp oil application to head hair and the implications on resulting cannabinoid measurements.