THCCOOH concentrations in whole blood: Are they useful in discriminating occasional from heavy smokers?

Abstract

Some forensic and clinical circumstances require knowledge of the frequency of drug use. Care of the patient, administrative, and legal consequences will be different if the subject is a regular or an occasional cannabis smoker. To this end, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) has been proposed as a criterion to help to distinguish between these two groups of users. However, to date this indicator has not been adequately assessed under experimental conditions. We carried out a controlled administration study of smoked cannabis with a placebo. Cannabinoid levels were determined in whole blood using tandem mass spectrometry. Significantly high differences in THCCOOH concentrations were found between the two groups when measured during the screening visit, prior to the smoking session, and throughout the day of the experiment. Receiver operating characteristic (ROC) curves were determined and two threshold criteria were proposed in order to distinguish between these groups: a free THCCOOH concentration below 3 µg/L suggested an occasional consumption (≤ 1 joint/week) while a concentration higher than 40 µg/L corresponded to a heavy use (≥ 10 joints/month). These thresholds were tested and found to be consistent with previously published experimental data. The decision threshold of 40 µg/L could be a cut-off for possible disqualification for driving while under the influence of cannabis. A further medical assessment and follow-up would be necessary for the reissuing of a driving license once abstinence from cannabis has been demonstrated. A THCCOOH level below 3 µg/L would indicate that no medical assessment is required.

Long-Term Effects of Cannabis on Brain Structure

“…Further details regarding the inclusion procedure are indicated in Battistella et al (2013). In both groups of cannabis users, we performed a urine and a blood test during the inclusion process in order to determine the concentration of Δ9-Tetrahydrocannabinol-carboxylic acid (THCCOOH) and confirm the regular use and the extent of cannabis consumption (Fabritius et al , 2013b). Participants also filled out a questionnaire about their usual drug use habits.…”

Development of a rapid column-switching LC-MS/MS method for the quantification of THCCOOH and THCCOOH-glucuronide in whole blood for assessing cannabis consumption frequency

“…After a proven period of abstinence and regular medical checkups, the driver's license may be re-issued. In the study conducted by Fabritius et al [17] the 40 µg/L cut-off for free THCCOOH showed a low sensitivity, implying that its ability to correctly identify heavy users is rather poor. Since THCCOOH in blood is extensively glucuronidated [19], we hypothesize that the free THCCOOH blood level is not solely determined by the consumption frequency, but is also dependent on the individual glucuronidation rate.…”

“…Further biotransformation via phase II glucuronidation produces hydrophilic conjugates that are easily excreted [11]. Due to its long elimination half-life [11] , THCCOOH accumulates in the blood upon regular cannabis use [12][13][14][15] and has therefore been proposed as diagnostic marker to distinguish between occasional and heavy users [16,17]. In Switzerland, a free THCCOOH blood level of 40 µg/L is currently used as cut-off for the classification of impaired drivers as heavy users, as recommended by Fabritius et al [17,18].…”

“…Due to its long elimination half-life [11] , THCCOOH accumulates in the blood upon regular cannabis use [12][13][14][15] and has therefore been proposed as diagnostic marker to distinguish between occasional and heavy users [16,17]. In Switzerland, a free THCCOOH blood level of 40 µg/L is currently used as cut-off for the classification of impaired drivers as heavy users, as recommended by Fabritius et al [17,18]. Since chronic cannabis consumption may imply a long-term unfitness to drive, these drivers suspected of heavy cannabis misuse are required to undergo medical assessment of their fitness to drive, even if no active THC was detected in their blood.…”

The current situation with cannabinoids

“…Fabritius et al [48] in this issue recommend a way forward, based on the combination of findings from analysis of whole blood THC and a medical interview of the driver, in the context of the zero tolerance policy in their country, Switzerland. This is not a trivial consideration and can have cost implications for governments that consider it important to have follow-up investigations of offending drivers to answer this question.…”