Mark Chu

The incidence of drugs in drivers killed in Australian road traffic crashes.

The incidence of alcohol and drugs in fatally injured drivers were determined in three Australian states; Victoria (VIC), New South Wales (NSW) and Western Australia (WA) for the period of 1990-1999. A total of 3398 driver fatalities were investigated which included 2609 car drivers, 650 motorcyclists and 139 truck drivers. Alcohol at or over 0.05 g/100ml (%) was present in 29.1% of all drivers. The highest prevalence was in car drivers (30.3%) and the lowest in truckers (8.6%). WA had the highest rate of alcohol presence of the three states (35.8%). Almost 10% of the cases involved both alcohol and drugs. Drugs (other than alcohol) were present in 26.7% of cases and psychotropic drugs in 23.5%. These drugs comprised cannabis (13.5%), opioids (4.9%), stimulants (4.1%), benzodiazepines (4.1%) and other psychotropic drugs (2.7%). 8.5% of all drivers tested positive for Delta(9)-tetrahydrocannabinol (THC) and the balance of cannabis positive drivers were positive to only the 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (carboxy-THC) metabolite. The range of THC blood concentrations in drivers was 0.1-228 ng/ml, with a median of 9 ng/ml. Opioids consisted mainly of morphine (n=84), codeine (n=89) and methadone (n=33), while stimulants consisted mainly of methamphetamine (n=51), MDMA (n=6), cocaine (n=5), and the ephedrines (n=61). The prevalence of drugs increased over the decade, particularly cannabis and opioids, while alcohol decreased. Cannabis had a larger prevalence in motorcyclists (22.2%), whereas stimulants had a much larger presence in truckers (23%).

The incidence of drugs of impairment in oral fluid from random roadside testing

Oral fluid (OF) has become a popular specimen to test for presence of drugs, particularly in regards to road safety. In Victoria, OF specimens from drivers have been used to test for the presence of methylamphetamine (MA) and Δ(9)-tetrahydrocannabinol (THC) since 2003 and 3,4-methylenedioxy-N-methylamphetamine (MDMA) since 2006. LC-MS/MS has been used to test the most recent 853 submitted OF specimens from Victoria Police for 31 drugs of abuse including those listed in the Australian Standard AS4760-2006. At least one proscribed drug was detected in 96% of drivers, of which MA was the most common (77%), followed by THC (42%), MDMA (17%) and the combination of all three (3.9%). Opioids were detected in 14% of drivers of which 4.8% were positive for 6-acetylmorphine and 3.3% for methadone. The incidence of the opioids tramadol (1.2%) and oxycodone (1.1%) were relatively low. Cocaine (8.0%) was as commonly detected as benzodiazepines (8.0%), and was almost always found in combination with MA (7.9%). Samples positive to benzodiazepines were largely due to diazepam (3.5%) and alprazolam (3.4%), with only 0.2% of drivers combining the two. Ketamine was also detected in 1.5% of cases. While the incidences of the proscribed drugs itself are concerning, it is clear that many drivers are also using other drugs capable of causing impairment.

Residual cannabis levels in blood, urine and oral fluid following heavy cannabis use

An understanding of tetrahydrocannabinol (THC) kinetics and residual levels after cannabis use is essential in interpreting toxicology tests in body fluids from live subjects, particularly when used in forensic settings for drug abuse, traffic and interpersonal violence cases. However the current literature is largely based on laboratory studies using controlled cannabis dosages in experienced users, with limited research investigating the kinetics of residual THC concentrations in regular high dose cannabis users. Twenty-one dependent cannabis users were recruited at admission to two residential detoxification units in Melbourne, Australia. After being provided with information about, and consenting to, the study, subjects volunteered to provide once-daily blood, urine and oral fluid (saliva) samples for seven consecutive days following admission, involving cessation and abstinence from all cannabis use. Blood and oral fluid specimens were analysed for THC and urine specimens for the metabolite THC-COOH. In some subjects THC was detectable in blood for at least 7 days and oral fluid specimens were positive for THC up to 78 h after admission to the unit. Urinary THC-COOH concentrations exceeded 1000 ng/mL for some subjects 129 h after last use. The presented blood THC levels are higher and persist longer in some individuals than previously described, our understanding and interpretation of THC levels in long term heavy cannabis users may need to be reconsidered.

The effect of blood in the oral cavity on breath alcohol analysis

The theory that blood (containing alcohol) present in the oral cavity may falsely increase breath analysis recently led to a successful appeal against a drink driving conviction. Subjects who had previously consumed vodka (37.2% alc/vol), at 30 ml/10 kg and reached a BAC (blood alcohol concentration) of between 0.05 and 0.10% were then given four oral solutions consisting of a control (distilled water), and 0.05, 0.10 and 0.15% aqueous alcohol (ethanol) solutions, administered in coded form. A four-way cross-over, blind, randomized assay was conducted with the solutions, with breath analyses conducted in the presence or absence of solution in the mouth. The first trial group (n = 18) received 2 ml of solution, and we found that the simulated 0.15, 0.10 and 0.05% alcohol solutions in the mouth produced BAC reading increases of 0.0088 +/- 0.0014, 0.0062 +/- 0.0008 and 0.0055 +/- 0.0010% respectively (p < 0.001). The second trial group (n = 20) received 1 ml of solution and produced BAC reading increases of 0.0047 +/- 0.0011 (p < 0.001), 0.0023 +/- 0.0008 (p < 0.01) and 0.0020 +/- 0.0006% (p < 0.05) respectively. In conclusion, these studies indicate that small volumes of blood (containing alcohol) in the mouth would not have a practical effect on breath analysis readings.

An assessment of the stability of MDMA, methamphetamine and THC in oral fluid

The stability of drugs proscribed under the Victorian Road Safety Act 1986 (MDMA, MA and THC) was determined in authentic drug-positive oral fluid following short-term storage at room temperature, 4ºC, fluctuating temperatures and long-term storage at –20 ºC. Following pH adjustment with ammonium carbonate solution, drugs were extracted using chloroform:isopropanol (9:1) and analysed by LC-MS/MS operating in multiple reaction monitoring mode. The results were analysed using Wilcoxon matched-pairs signed ranks and interpreted in the context of AS4760:2006 cut-offs. For MA and MDMA only minor changes occurred following all storage conditions, but THC concentrations were reduced by 70–87% (n=10) following storage at fluctuating temperatures (room temperature to 60°C) for 2 weeks. Of the 10 samples that were positive for THC prior to storage, only one remained positive after 2 weeks. This has significant implications for the interpretation of THC concentrations in cases where the possibility exists that samples were stored at higher temperatures.