Cannabinoid concentrations in hair from documented cannabis users

Abstract

Fifty-three head hair specimens were collected from 38 males with a history of cannabis use documented by questionnaire, urinalysis and controlled, double blind administration of delta9-tetrahydrocannabinol (THC) in an institutional review board approved protocol. The subjects completed a questionnaire indicating daily cannabis use (N=18) or non-daily use, i.e. one to five cannabis cigarettes per week (N=20). Drug use was also documented by a positive cannabinoid urinalysis, a hair specimen was collected from each subject and they were admitted to a closed research unit. Additional hair specimens were collected following smoking of two 2.7% THC cigarettes (N=13) or multiple oral doses totaling 116 mg THC (N=2). Cannabinoid concentrations in all hair specimens were determined by ELISA and GCMSMS. Pre- and post-dose detection rates did not differ statistically, therefore, all 53 specimens were considered as one group for further comparisons. Nineteen specimens (36%) had no detectable THC or 11-nor-9-carboxy-THC (THCCOOH) at the GCMSMS limits of quantification (LOQ) of 1.0 and 0.1 pg/mg hair, respectively. Two specimens (3.8%) had measurable THC only, 14 (26%) THCCOOH only, and 18 (34%) both cannabinoids. Detection rates were significantly different (p<0.05, Fishers' exact test) between daily cannabis users (85%) and non-daily users (52%). There was no difference in detection rates between African-American and Caucasian subjects (p>0.3, Fisher's exact test). For specimens with detectable cannabinoids, concentrations ranged from 3.4 to >100 pg THC/mg and 0.10 to 7.3 pg THCCOOH/mg hair. THC and THCCOOH concentrations were positively correlated (r=0.38, p<0.01, Pearson's product moment correlation). Using an immunoassay cutoff concentration of 5 pg THC equiv./mg hair, 83% of specimens that screened positive were confirmed by GCMSMS at a cutoff concentration of 0.1 pg THCCOOH/mg hair.

Hair testing is taking root

“…The majority of published hair testing methods are for drugs of abuse, including opiates, 42,60,69 cocaine, 64,87,98 amphetamines 66,67,75,84 and cannabinoids, 58,85,86,99 employing GC-MS or LC-MS-MS. Although new methods have been reported using specialist analytical instrumentation including quadruple time-of-flight and matrix-assisted laser desorption/ionization time of flight, 97,100 standard instrumentation and method parameters (temperature programme, ions selected for monitoring, collision energies, etc.)…”

Comparison of cannabinoid concentrations in oral fluid and whole blood between occasional and regular cannabis smokers prior to and after smoking a cannabis joint

“…However, this matrix is not always available, or can be contaminated by cannabis smoke [4] or by contact with dirty hands, thus making its interpretation quite challenging. Furthermore, in comparative studies, discrepancies were found between "positive" urine specimens and hair tested as "negative" [5,6]. Thus, measurement of cannabinoids in biofluids offers another strategy.…”

Using biological samples in epidemiological research on drugs of abuse

“…In a study of 100 users of amphetamines, only 56% had positive hair sample (81), indicating that a negative finding does not exclude the possibility of drug use. For cannabis a positive result is not guaranteed even after daily use (82). In general, hair samples are very well suited for the detection of cocaine use, fairly well suited for detection of amphetamines and benzodiazepines, and not very well suited for detection of cannabis use.…”