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Department of Forensic Medicine and Science, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
In relation to Alcohol, Drugs and Driving, there are two offences set out in the Road Traffic Act of 1988. A charge under Section 4 of the Act is one of impairment under the influence of drink or drugs. The Section 5 offence is one of driving with more than the prescribed limit of alcohol.
Scotland has been relatively late in developing a problem with the misuse of drugs. In 1984, for example, there are only two recorded deaths from the misuse of Heroin in the Registrar Generals Report for Scotland. This figure has increased dramatically to 101 deaths in 1993, and, if present trends are followed, will exceed 120 deaths in the current year. Deaths in the late 1980s involved primarily Heroin but since then, the trend has been towards the use of benzodiazepines, primarily Temazepam, probably as a result of its widespread availability from prescription and, initially because of its ease of use by injection because of the liquid capsule centre. Consequently in 1992, 79% of all drug addict deaths involved a benzodiazephine drug. Temazepam was involved in 90% either alone or in combination with Diazepam.
In 1993, 207 blood samples were received from Police Forces in Scotland. 130 were found to contain drugs. Of these, 97 contained Benzodiazepine drugs either alone or in combination with other drugs.
This paper describes the analytical procedures used, presents the findings and compares them with the results of the investigations of the most recent deaths from the abuse of drugs.
In relation to Alcohol, Drugs and Driving, there are two offences set out in the Road Traffic Act of 1988. A charge under Section 4 of the Act is one of impairment under the influence of drink or drugs. The Section 5 offence is one of driving with more than the prescribed limit of alcohol. Prosecutions for the latter depend on the use of an evidential breath analyser or on the measurement of alcohol in blood or urine using gas chromatography.
Scotland has been relatively late in developing a problem with the misuse of drugs. In 1984, for example, there were only two recorded deaths from the misuse of Heroin in the Registrar Generals Report for Scotland. This figure has increased dramatically to 101 deaths in 1993 (Cassidy et al, 1995) and exceeded 135 deaths in 1994. Deaths in the late 1980s involved primarily Heroin but since then, the trend has been towards the use of benzodiazepines, primarily Temazepam, probably as a result of its widespread availability on prescription. Initially, because of the liquid capsule centre it was easy to use by injection. Consequently in 1992, 79% of all drug addict deaths involved a benzodiazepine drug. Temazepam was involved in 90% either alone or in combination with Diazepam (Cassidy et al. 1995, Hammersley et al, 1995).
In 1993, 256 samples were received from Police Forces in Scotland from drivers suspected of contravening section 4 of the Road Traffic act. This poster outlines the analytical procedures used, presents the findings and compares them with the most recent deaths from the abuse of drugs.
Standing Orders require Police to submit a minimum of 10 millilitres of blood for laboratory investigation. Blood samples are pretreated by extraction with methanol (four volumes). The methanol extract is evaporated carefully to dryness at 40C under Nitrogen. The residue is reconstituted to original volume with RIA-assay buffer and is screened for the presence of Benzodiazepines, opiates, LSD, Cannabinoids, amphetamines, buprenorphine and methadone by radio-immunoassay, (D.P.C. Coat-a-count). Additionally samples of blood are screened for acidic, basic and neutral drugs by H.P.L.C. and G.L.C. All positives are confirmed by GC-MS with derivative formation if required. Drug levels are measured using stable isotope reference materials where available or by internal standard procedures.
On suspicion of impaired driving, a Police surgeon is summoned and is required to carry out an examination of the driver to ascertain impairment through illness, alcohol and/or drugs. Care of the patient is the first priority. If impairment is suspected through drugs or alcohol the doctor is required to take at least 20 millilitres of blood. This specimen is divided into equal portions, labelled and sealed into tamper proof containers. The driver is given the option of choosing a specimen for independant analysis. The other specimen is submitted to the laboratory.
256 specimens were received in 1993. 207 were bood and 49 were urine. Of the blood samples, 135 were found to contain drugs, 122 were from males and 13 were from females. Of the urine samples, 23 contained drugs, 21 from males and 2 from females. 191 drugs were detected in the 135 positive blood samples (Table 1). The most frequently encountered were benzodiazepine drugs and cannabinoids. 63 drugs were detected in the urine samples (Table 2). Again benzodiazepine drugs were the most common. Although a significant number contained cannabinoids, opiates and amphetamines were equally prominant.
Road Traffic Drug Cases (1993) Positive Blood Samples (135) Total Drugs Detected (191)
|Drug Detected||Number||Level Measured mg/litre AVG(LOW - HIGH)||Therapeutic Level mg/litre (Stead & Moffat, 1983)|
|THC*||2||1.1 (0.8 - 2.2)**||-|
|THC-COOH***||24||40.7 (0.1 - 221)**||-|
|Amphetamine||2||0.9 (0.3 - 1.5)||0.5 - 2.0|
|Carbamazepine||3||12.3 (2.4 - 24.6)||3.5 - 9.4|
|Chlordiazepoxide||6||7.5 (0.3 - 25.5)||1.0 - 8.0|
|Desmethyldiazepam||33||0.5 (0.1 - 2.9)||-|
|Diazepam||32||0.6 (0.1 - 2.8)||0.05 - 2.0|
|Temazepam||73||2.2 (0.1 - 13.3)||0.36 - 0.85|
|Morphine||4||0.3 (0.2 - 0.7)||0.04 - 0.5|
|Methadone||3||0.4 (0.3 - 0.6)||0.05 - 1.0|
Road Traffic Drug Cases (1993) Positive Urine Samples (23) Total Drugs Detected (63)
A breakdown of the benzodiazepine drugs shows Temazepam to be, by far, the most commonly encountered drug (Tables 1, 2). This is reflected in the figures from deaths in that year which revealed Temazepam to be the second most frequently encountered drug after Paracetamol (Table 3). In the death figures, cannabinoids and amphetamines were not encountered in significant numbers. The high incidence of opiates (including methadone) is reflected in the road traffic figures.
Drugs in Sudden and Unexpected Deaths (1993)
The diagnosis of impairment is the responsibility of the Police surgeon. The laboratory findings are used primarily for corroboration. The investigation of cannabis resulted in only 2 cases where the pharamacologically active delta-9-tetrahydrocannabinol was detected. In all other cases, only the allegedly inactive metabolite was found.
For all other drugs, very few measurements were below the expected therapeutic range (Table 1). Consequently a statement that there was a potential for impairment from the substance measured was possible in the majority of cases. Attempts to prosecute at very low drug levels without medical backup and without precognition of the analyst generally failed.
The drugs detected in driving cases broadly reflect the availability of drugs that are being misused. The drugs are being detected at significant levels with respect to expected therapeutic values. Misuse of drugs by drivers is predominantly a male problem, a reflection of our findings in drug deaths in 1992 and in 1993. The figures highlight a problem with cannabis. Since samples were taken from drivers who have been diagnosed as being impaired, the finding of an allegedly inactive metabolite indicates a requirement for further reseach.
Cassidy, M.T., Curtis, M., Muir, G. and Oliver, J.S.(1995), "Drug abuse deaths in Glasgow - 1992 (A retrospective study)" Medicine, Science and the Law, in press.
R.Hammersley, R., Cassidy, M.T. and Oliver, J.S.,(1995) "Drugs associated with drug related deaths in Edinburgh and Glasgow, November 1990 to October, 1992" Addiction, in press.
Stead, A.H. and Moffat, A.C., (1983) "A collection of therapeutic, toxic and fatal blood drug concentrations in man" Human Toxicology, 3, 437-464.