Drugs in oral fluid in randomly selected drivers
Introduction
A number of jurisdictions around the world have adopted the use of oral fluid to detect the presence of drugs of abuse, particularly in relation to persons driving motor vehicles [1], [2], [3], [4], [5], [6], [7]. The intent has been to detect recent use of an illicit substance at a time when the driver may be at a higher road safety risk to the community.
Blood concentrations of these drugs cannot easily be compared to oral fluid. On average the methamphetamine (MA) concentration in oral fluid is about eight times that of blood, but this will vary according to a number of factors. Δ9-Tetrahydrocannabinol (THC) concentrations are more variable in oral fluid compared to blood and will derive more from leaching out of the tissues within the oral cavity than partitioning from the circulating blood [8]. Nevertheless pharmacokinetic studies have on average shown a reasonable correlation between oral fluid and blood concentrations [9], [10], [11]. Oral fluid concentrations of methamphetamine and THC have been reported to range up to about 1000 and 4000 ng/ml, respectively, following measured doses of these drugs [8].
Recent amendments to the road safety act in the state of Victoria gave police the authority to randomly test drivers for the presence of THC and MA. The purpose of this law was to provide police with an effective deterrence (to taking drugs and driving), similar to the random breath alcohol program that has been in operation in the state for 30 years. Two on-site screening devices, Securetec DrugWipe®, and the Cozart Rapiscan® were selected for use by the police in their on-site screening of drivers as part of a legislative trial. This is the first such program to be conducted in the world.
This paper describes the results of the testing of over 13,000 drivers in the first year of operation and provides unique data on the incidence of amphetamines and cannabis drugs in the general driving population. The results include those of the drug screening devices used at the roadside and in the drug bus and the laboratory confirmation results of specimens sent to the laboratory. This provides data on the performance of these devices for use in point-of-care testing.
Section snippets
Reagents
All general reagents and chemicals were obtained to analytical reagent grade. Pentafluoroisopropanol was obtained from Aldrich Chemicals (Sydney, Australia) and pentafluoropropionyl anhydride was obtained from Regis Chemicals (Melbourne, Australia). Isotopically labeled internal standards were obtained from Cambridge isotope laboratories (Novachem, Melbourne, Australia). Drug standards were obtained from the Division of Analytical Laboratories, Lidcombe, NSW (amphetamines), and Cambridge
Performance characteristics of GC–MS methods
Both GC–MS methods performed reliably during the conduct of these studies using 250 μl of specimen. In some early cases, 500 μL was used but this was reduced to 250 μL when the sensitivity was not an issue. The validation parameters for the two confirmation methods are shown in Table 1. Very similar performance data was obtained for blood (data not shown). Chromatograms were clean and free from interference. There were no matrix “blank” peaks associated with either method for the analytes of
Discussion
The random drug testing program described here has shown a combined incidence of MA and THC of 2.4%, or about one driver in 40, which was more than double the alcohol positive rate in the 13,176 screened drivers and almost five times the long term average incidence of alcohol (1:230) random testing program (Drummer, unpublished data). This was much higher than originally estimated based on the relative incidence of these drugs to alcohol in fatally-injured drivers in Victoria in which THC and
Acknowledgements
The assistance of many staff of the Traffic Alcohol Section of Victoria Police, Vicroads and the Department of Justice are gratefully acknowledged, as is the technical and scientific staff of the toxicology laboratory of the Victorian Institute of Forensic Medicine. The cooperation of technical personnel associated with Securetec, Cozart, and Biomediq were essential to ensure the conduct of this trial.
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