Citation

Moller MR, Kauert G, Tonnes S, Schneider E, Theunissen EL, Ramaekers JG. Blutalkohol 2006; 43(5): 361-375.

Affiliation

Starterzentrum, Geb. 07, Uniklinikum des Saarlandes, 66421 Homburg/Saar, Germany

Copyright

(Copyright © 2006, International Committee on Alcohol, Drugs and Traffic Safety and Bund gegen Alkohol und Drogen im Straßenverkehr, Publisher Steintor Verlag)

DOI

unavailable

PMID

unavailable

Abstract

To date, experimental studies regarding the impairment of psycho-physical performance after cannabis use were based on tests with low doses of THC and short observation time. In the present double blind, placebo controlled study, the influence of high doses of THC on performance was tested, measuring skills essentially related to car driving, such as perception, reasoning, impulse control and fine motor skills, were investigated during the first six hours after smoking. On three separate test days, 20 subjects smoked marihuana cigarettes containing 500 (mu)g THC/kg bodyweight, 250 (mu)g THC/kg bodyweight and placebo. In addition, 10 blood and saliva samples were taken at regular intervals for six hours after smoking. For both THC conditions, significant differences from the placebo condition were found on all performance tests, i.e. on fine motor performance, reaction time, perception and reasoning. These differences were demonstrated during the first 2 to 3 hours after smoking, at which THC concentration in serum reached 5-10 ng/ml. Until 5 hours after smoking, a significant effect on fine motor performance was found. At this point THC concentration in serum reached 2-5 ng/ml. No performance differences were demonstrated when THC in serum was below 1 ng /ml. These results confirm earlier statements of the Grenzwertkommission (threshold value commission) that the probability of impairing effects of cannabis is more and more reduced with THC-concentrations below 1 ng/ml, which has been accepted by the BVG (German Supreme Constitution Court) [8]. Immediately after smoking the THC concentration in serum was approximately 60 ng/ml for the low dose and 90 ng/ml for the high dose. After 6 hours, this dropped to about 1 ng/ml in both groups. Standardized saliva samples during the test day demonstrated that THC concentrations in saliva (when measured with GC-MS) and serum generally decrease in parallel, however with great individual variations. Only under favourable conditions and during the first 2 hours after smoking (limit of detection of 20 ng/ml will currently available saliva tests show positive THC concentration.

Keywords: Cannabis impaired driving