ND DONZE NICOLAS¹, MFR MICHEL ROSSIER¹, MPA MARC AUGSBURGER<sup>2

1</sup>Hôpital du Valais, ICH, Sion, Valais, ²CURML, CHUV, Lausanne, Vaud

Introduction: Addiction, is a developmental disease which typically begins in childhood or adolescence and could be observed in cannabis consumers as well. To get information on the habit of consumption, the measurement of free THC-COOH in blood is becoming an indicator to diagnose cannabis addiction in forensic toxicology. According to M. Fabritius et al., 2013, “… a free THC-COOH concentration below 3 ng/mL suggested an occasional consumption while a concentration higher than 40 ng/mL corresponded to a heavy use” Will THC-COOH concentration in blood therefore become a new clinical chemistry indicator of cannabis consumption and addiction?

Aims: Medical toxicology investigation is mostly performed by immunological screening in urine for drugs, and in blood for alcohol only. In order to evaluate the number of regular cannabis users, the present study analyzed the statistics of forensic cases involving drivers positive for cannabis, and with a value above the 40 ng/mL cut-off.

Methods: According to the Swiss Road traffic law, if policeman suspects drug consumption, urine and blood are collected and analysed by GC-MS (LOQ’s for THC, 11-OH-THC and THC-COOH are respectively 1.0, 1.0 and 4.0 ng/ml).

Results:
In 2014 and 2015, samples from 261 and 315 drivers, respectively, were controlled. Cannabis was positive in 133 (51 %) and 176 (55 %) cases respectively. No cases present value of THC-COOH under 3 ng/ml. More than 50 % of the cannabis cases present a THC-COOH value greater than 40 ng/ml.


Conclusions: More than 50 % of positive drivers appear to be regular consumers, with a THC-COOH concentration in blood above the cut-off value of 40 ng/ml.
These data suggest that a majority of consumers can be considered as regular consumers and it could therefore be useful in medical situations, if a patient announces a consumption of cannabis, to determine if he is a regular consumer