Detection of cannabis in oral fluid (saliva) and forehead wipes (sweat) from impaired drivers

Saliva and sweat have been presented as two alternative matrices for the establishment of drug abuse. The noninvasive collection of a saliva or sweat sample, which is relatively easy to perform and can be achieved under close supervision, is one of the most important benefits in a driving-under-the-influence situation. Moreover, the presence of certain analytes in saliva is a better indication of recent use than when the drug is detected in urine, so there is a higher probability that the subject is experiencing pharmacological effects at the time of sampling. We developed an original procedure using gas chromatography-mass spectrometry to test for Δ9-tetrahydrocannabinol (THC), the psychoactive ingredient of cannabis, in oral fluid and forehead wipes, collected with Sarstedt Salivettes(TM) and cosmetic pads, respectively. Blood, urine, oral fluid, and forehead wipes were simultaneously collected from 198 injured drivers admitted to an Emergency Hospital in Strasbourg, France. Of the 22 subjects positive for 11-nor-9-carboxy-THC (THCCOOH) in urine, 14 and 16 were positive for THC in oral fluid (1 to 103 ng/Salivette) and forehead wipe (4 to 152 ng/pad), respectively. 11-Hydroxy-THC and THCCOOH were not detected in these body fluids. Two main limitations of saliva and sweat are apparent: the amount of matrix collected is smaller when compared to urine, and the levels of drugs are higher in urine than in saliva and sweat. A current limitation in the use of these specimens for roadside testing is the absence of a suitable immunoassay that detects the parent compound in sufficiently low concentrations.