High concentrations of diazepam and nordiazepam in blood of impaired drivers: association with age, gender and spectrum of other drugs present

Selective Extraction of Diazepam and Its Metabolites from Urine Samples by a Molecularly Imprinted Solid-Phase Extraction (MISPE) Method

In this research, a molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using oxazepam (OZ) as a template molecule and was subsequently applied as a selective sorbent for the extraction of diazepam (DZP) and its metabolites in urine samples using an SPE cartridge. OZ, temazepam (TZ), nordiazepam (NZ) and DZP were analyzed in the final extracts by high-performance liquid chromatography with diode array detection (HPLC-DAD). The SPE extraction steps were optimized, and the evaluation of an imprinting factor was carried out. The selectivity of the method for OZ versus structurally related benzodiazepines (BZDs), such as bromazepam (BRZ), tetrazepam (TTZ) and halazepam (HZ), was investigated. Under the optimum conditions, the proposed methodology provided good linearity in the range of 10-1500 ng/mL, with limit of detection values between 13.5 and 21.1 ng/mL and recovery levels for DZP and its metabolites from 89.0 to 93.9% (RSD ≤ 8%) at a concentration level of 1000 ng/mL. The proposed method exhibited good selectivity, precision and accuracy and was applied to the analysis of urine samples from a real case of DZP intake.

Pharmacokinetics of Diazepam and Its Metabolites in Urine of Chinese Participants

BACKGROUND

Urine is conventionally used as a specimen to document diazepam-related crimes; however, few reports have described the pharmacokinetics of diazepam and its metabolites in urine.

OBJECTIVE

This study aimed to investigate the pharmacokinetics of diazepam and its metabolites, including glucuronide compounds, in the urine of Chinese participants.

METHODS

A total of 28 volunteers were recruited and each participant ingested 5 mg of diazepam orally. Ten milliliters of urine were collected from each participant at post-consumption timepoints of prior (zero), 1, 2, 4, 8, 12, and 24 h and 2, 3, 6, 12, and 15 days. All samples were extracted by solid-phase extraction and analyzed using high-performance liquid chromatography-tandem mass spectrometry. Diazepam and its main metabolites, except for temazepam, were detected in the urine of volunteers. Pharmacokinetic parameters were analyzed using the pharmacokinetic software DAS according to the non-compartment model.

RESULTS

Urinary diazepam peaked at 2.38 ng/mL (C_max) and 1.93 h (T_max). The urinary metabolite nordiazepam peaked at 1.17 ng/mL and 100.21 h; temazepam glucuronide (TG) peaked at 145.61 ng/mL and 41.14 h; and oxazepam glucuronide (OG) peaked at 101.57 ng/mL and 165.86 h. The elimination half-life (t_½z) and clearance (CLz/F) for diazepam were 119.58 h and 65.77 L/h, respectively. The t_½z of the metabolites nordiazepam, TG, and OG was 310.58 h, 200.17 h, and 536.44 h, respectively. Finally, this study found that both diazepam and its main metabolites in urine were detectable for at least 15 days, although there were individual differences.

CONCLUSION

The results regarding diazepam pharmacokinetics in urine would be of great help in forensic science and drug screening.

Analysis of phenazepam and 3-hydroxyphenazepam in post-mortem fluids and tissues

Phenazepam is a benzodiazepine that is predominantly used clinically in the former Soviet states but is being abused throughout the wider world. This study reports the tissue distribution and concentration of both phenazepam and 3-hydroxyphenazepam in 29 cases quantitated by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a variety of post-mortem fluids (subclavian blood, femoral blood, cardiac blood, urine, vitreous humour) and tissues (thalamus, liver and psoas muscle). In 27 cases, the cause of death was not directly related to phenazepam (preserved (fluoride/oxalate) femoral blood phenazepam concentrations 0.007 mg/L to 0.360 mg/L (median 0.097 mg/L). In two cases, phenazepam was either a contributing factor to, or the certified cause of death (preserved (fluoride/oxalate) femoral blood 0.97 mg/L and 1.64 mg/L). The analysis of phenazepam and 3-hydroxyphenazepam in this study suggests that they are unlikely to be subject to large post-mortem redistribution and that there is no direct correlation between tissues/fluid and femoral blood concentrations. Preliminary investigations of phenazepam stability comparing femoral blood phenazepam concentrations in paired preserved (2.5% fluoride/oxalate) and unpreserved blood show that unpreserved samples show on average a 14% lower concentration of phenazepam and we recommend that phenazepam quantitation is carried out using preserved samples wherever possible.

Pregabalin serum levels in apprehended drivers

Pregabalin is a medicinal drug used mainly for the treatment of epilepsy and neuropathic pain. It has been shown to possess an abuse potential and in recent years some reports of illegal use have been published. In order to further evaluate the extent and nature of pregabalin abuse, serum pregabalin levels of drivers apprehended for driving under the influence of drugs (DUID) in Finland in 2012 were assessed. The samples were analysed by an LC-MS/MS system and the results were evaluated in relation to the typical therapeutic range of pregabalin as well as the age and gender of the driver. Pregabalin was detected in 206 samples in the study period. The median (range) serum concentration was 6.2 (0.68-111.6)mg/L. In nearly 50% of the cases the serum concentration was above the typical therapeutic range. In most of the cases the driver had also taken other drugs besides pregabalin, the mean number of concomitantly taken drugs being four. Our data indicate that pregabalin is being used at high doses, probably for recreational purposes. The vast majority of the drivers positive for pregabalin in our study material had used pregabalin as a part of a spectrum of psycho-active drugs and thus qualified as probable drug abusers. In these cases pregabalin probably contributed to their driving impairment but to what extent remained unclear in this study.

Concentrations of drugs determined in blood samples collected from suspected drugged drivers in England and Wales

This communication reports the blood concentrations of alcohol and drugs from 376 cases of alleged driving under the influence of drugs analysed at the Forensic Science Service Chorley and London laboratories between February 2010 and March 2011. The samples were analysed for alcohol, amphetamine, benzodiazepines, cocaine, MDMA, opiates, γ-hydroxybutyrate (GHB), ketamine, methadone and methylmethcathinone (the 4-isomer of which is known as mephedrone). The results were interpreted with respect to the number and type of drugs of abuse detected and the concentrations measured. Alcohol was quantified in 113 cases (30%), and of these a level in excess of the prescribed UK limit for driving of 80 mg% was present in 90 cases. In 80 cases, only the concentration of alcohol was measured, the concentrations of both drugs and alcohol were measured in 33 cases. In the remaining 263 cases, only the concentrations of relevant drugs of abuse were measured. The most common drug of abuse quantified was cocaine which was detected in 92 cases, either as the active drug or as its major metabolite benzoylecgonine, followed by diazepam which was quantified in 76 cases. Concentrations of some new drugs, and drugs rarely reported in driving under the influence cases are also presented.

What non-alcohol drugs are used by drinking drivers in Sweden? Toxicological results from ten years of forensic blood samples

INTRODUCTION AND METHOD

Using a forensic toxicology database (TOXBASE), the toxicological results from 10 years of forensic blood samples from people arrested for driving under the influence of alcohol and/or other drugs were reviewed.

RESULTS

Alcohol was the only drug identified in blood in N=35,704 cases at a median blood-alcohol concentration (BAC) of 1.63 mg/g. The mean age (±SD) of these offenders was 40±15years and 89% were male. The median BAC was lower (1.30 mg/g) in drivers who had consumed alcohol and used a prescription drug before driving (N=1,251). The mean age of this group of traffic offenders was 38±13years and 85% were male. Both the median BAC (0.97 mg/g) and the mean age were lowest (36±11years, 92% male) in N=3,153 drivers who had consumed alcohol and used illicit drugs before driving. Cannabis, amphetamine, cocaine and morphine (metabolite of heroin) were the commonest illicit drugs identified in blood samples. Sedative-hypnotics (benzodiazepines) were the major prescription drugs co-ingested with alcohol. Poly-drug use was a common finding in these traffic delinquents, although individuals who only drank alcohol had a higher median BAC and were also several years older than drinking drivers combining alcohol with other drugs before driving.

IMPACT ON INDUSTRY

Zero-tolerance legislation did not deter hard-core offenders. In future there should be more focus on treatment for alcohol and substance abuse disorder rather than conventional punishments for this type of traffic crime.

First nationwide study on driving under the influence of drugs in Switzerland

In Switzerland, a two-tier system based on impairment by any psychoactive substances which affect the capacity to drive safely and zero tolerance for certain illicit drugs came into force on 1 January 2005. According to the new legislation, the offender is sanctioned if Delta(9)-tetrahydrocannabinol THC is >or=1.5ng/ml or amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyethylamphetamine (MDEA), cocaine, free morphine are >or=15ng/ml in whole blood (confidence interval+/-30%). For all other psychoactive substances, impairment must be proven in applying the so-called "three pillars expertise". At the same time the legal blood alcohol concentration (BAC) limit for driving was lowered from 0.80 to 0.50g/kg. The purpose of this study was to analyze the prevalence of drugs in the first year after the introduction of the revision of the Swiss Traffic Law in the population of drivers suspected of driving under the influence of drugs (DUID). A database was developed to collect the data from all DUID cases submitted by the police or the Justice to the eight Swiss authorized laboratories between January and December 2005. Data collected were anonymous and included the age, gender, date and time of the event, the type of vehicle, the circumstances, the sampling time and the results of all the performed toxicological analyses. The focus was explicitly on DUID; cases of drivers who were suspected to be under the influence of ethanol only were not considered. The final study population included 4794 DUID offenders (4243 males, 543 females). The mean age of all drivers was 31+/-12 years (range 14-92 years). One or more psychoactive drugs were detected in 89% of all analyzed blood samples. In 11% (N=530) of the samples, neither alcohol nor drugs were present. The most frequently encountered drugs in whole blood were cannabinoids (48% of total number of cases), ethanol (35%), cocaine (25%), opiates (10%), amphetamines (7%), benzodiazepines (6%) and methadone (5%). Other medicinal drugs such as antidepressants and benzodiazepine-like were detected less frequently. Poly-drug use was prevalent but it may be underestimated because the laboratories do not always analyze all drugs in a blood sample. This first Swiss study points out that DUID is a serious problem on the roads in Switzerland. Further investigations will show if this situation has changed in the following years.

Differential effects of diazepam treatment and withdrawal on recombinant GABAA receptor expression and functional coupling

Prolonged exposure to benzodiazepines, drugs known to produce tolerance and dependence and also to be abused, leads to adaptive changes in GABA(A) receptors. To further explore the mechanisms responsible for these phenomena, we studied the effects of prolonged diazepam treatment on the recombinant alpha(1)beta(2)gamma(2S) GABA(A) receptors, stably expressed in human embryonic kidney (HEK) 293 cells. The results demonstrating that long-term (48 and 72 h) exposure of cells to a high concentration of diazepam (50 microM) enhanced the maximum number (B(max)) of [(3)H]flunitrazepam, [(3)H]muscimol and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding sites, without changing their affinity (K(d)), suggested the up-regulation of GABA(A) receptors. As demonstrated by cell counting and WST-1 proliferation assay, the observed increase in receptor expression was not a consequence of stimulated growth of cells exposed to diazepam. Semi-quantitative RT-PCR and Western blot analysis, showing elevated levels of alpha(1) subunit mRNA as well as beta(2) and gamma(2) subunit proteins, respectively, suggested that prolonged high dose diazepam treatment induced de novo receptor synthesis by acting at both transcriptional and translational levels. The finding that the number of GABA(A) receptor binding sites returned to control value 24 h following diazepam withdrawal, makes this process less likely to account for the development of benzodiazepine tolerance and dependence. On the other hand, the results demonstrating that observed functional uncoupling between GABA and benzodiazepine binding sites persisted after the termination of diazepam treatment supported the hypothesis of its possible role in these phenomena.

[Illicit drugs, medications and traffic accidents]

The European Union (EU) has 25 member-states and 455 million inhabitants. Statistics on traffic accidents in the EU show that more than 45,000 people are killed annually, including 5200 in France. At the same time, nearly two million persons in the EU require medical treatment for traffic-accident-related injuries, including 109,000 in France. In addition, traffic accidents are the major cause of death of those individuals aged 15 to 24 years. One third of the EU inhabitants will be hospitalized during their life due to a traffic accident with a cost over 160 billion euro (2-3% of the Gross Domestic Product). An important contributing factor to crashes is the use of alcohol and/or illicit drugs or medication when driving, as they exert negative effects on cognition and psychomotor functions. For illicit drugs, abuse of cannabis with or without alcohol is a major concern for the EU. In fact, three million Europeans use cannabis daily and 80% of them drive after use. A number of French studies since 1999 have underlined the high prevalence of cannabis found in the blood of injured or killed drivers. From medical or judicial observations, it is clear that cannabis use increases the risk of traffic accidents. Many groups outside Europe have also shown the association between drug abuse and crashes. The number of casualties related to certain medicines, especially benzodiazepines remains at a high level, particularly in the elderly. In many countries the prevalence of medicinal drugs associated with car accidents is higher than with cannabis. Annex III of the European Union Council Directive of July the 29th 1991 in fact states that a driving license should not be issued to or renewed for applicants or drivers who are dependent on psychotropic substances or use them regularly. Recently, France has categorized the medicinal drugs available in the country by using three pictograms: level one yellow, "be careful"; level two orange, "be very careful"; level three red, "don't drive". It is an important campaign that increases awareness among the public and the medical professionals about the potential dangerous effects of medicinal drugs when driving. The EU objective of reducing the number of fatalities to 25,000 by 2010 will require strengthening measures against the use of alcohol, illicit and medicinal drugs by not well-informed drivers. It is not only a really great challenge, but also a significant investment towards improving public health in France as well as in Europe.

Frequent detection of benzodiazepines in drugged drivers in Norway

OBJECTIVE

To describe the Norwegian system for handling suspected drugged driving cases according to an impairment-based law, with primary focus on benzodiazepines (BZDs), blood concentrations and combination with other psychoactive compounds.

METHODS

Routines for handling suspected driving under the influence of drugs other than alcohol are described. These include primary police investigation, blood sampling, and clinical tests of impairment performed by a police physician, a standard analytical program covering the most relevant illegal drugs and medicines relevant to traffic safety (approximately 25 compounds), and expert witness statements prepared for the court. The drug use patterns, blood drug concentrations, and frequency of multi-drug use have been recorded, with primary focus on benzodiazepines (BZDs). Use of BZDs among apprehended drivers has been compared with patient prescriptions recorded for the same BZDs.

RESULTS

One or more drugs have been detected in approximately 80% of the cases received for analysis every year. BZDs have been the most prevalent drugs and have been detected in 38-57% of the cases, which is more frequent than other common illegal drugs; e.g., tetrahydrocannabinol (THC; 30-43%) and amphetamine (33-39%). The majority of the BZDs have been detected at supratherapeutic blood concentrations and frequently in combination with illegal drugs, other psychoactive medicines, or alcohol. Less than 5% of the BZDs (except for nitrazepam - 7.6%) have been found to be the only drug present at therapeutic blood levels. The majority of the drivers were 20-39 years old (median age 29-33), while the majority of BZDs prescribed were to users over 50 years of age.

CONCLUSIONS

Drivers with BZD detected are probably not representative of ordinary patients with BZD prescriptions, as shown by the age disparity of drivers and patients. The frequent detection of BZDs suggests that these compounds should be included in the analytical program used for blood samples from apprehended drivers and for studies on drug involvement in road traffic accidents and risk calculations.

Predominance of illicit drugs and poly-drug use among drug-impaired drivers in Sweden

OBJECTIVE

After Sweden's zero-tolerance law came into force (1 July 1999), the number of cases of driving under the influence of drugs (DUID) submitted by the police for toxicological analysis increased more than 10-fold. This prompted an in-depth investigation into the kinds of drugs used by DUID offenders, whether licit or illicit, and the frequency of their occurrence.

METHODS

All blood samples from DUID suspects sent by the police for toxicological analysis over a 4-year period (2001-2004) were investigated (N = 22,777 cases). Specimens of blood or urine were subjected to a broad screening analysis by immunoassay methods aimed at detecting amphetamines, cannabis, opiates, cocaine metabolite, and the major benzodiazepines. All positive results from the screening stage were verified by use of more specific analytical methods (e.g., GC-MS, LC-MS, GC-FID, and GC-NPD).

RESULTS

Between 80 and 85% of all the blood samples contained at least one banned substance and many contained two or more therapeutic and/or illicit drugs. About 15% of cases were negative for drugs, although these frequently (30-50%) contained ethanol above the legal limit for driving in Sweden, which is 0.20 mg/g (0.02 g%). Amphetamine was the most prominent illicit drug seen in 55-60% of cases either alone or together with other drugs of abuse. Stimulants like cocaine and/or its metabolite were infrequently encountered ( approximately 1.2% of cases). The next most prevalent illicit drug was cannabis, with positive results for tetrahydrocannabinol (THC) in blood either alone ( approximately 4%) or together with other psychoactive substances ( approximately 20%). Morphine, codeine, and/or 6-acetyl morphine were identified in approximately 2% of all DUID suspects, being indicative of heroin abuse. The major prescription drugs identified in blood were benzodiazepines (10%) as exemplified by diazepam, alprazolam, nitrazepam, and flunitrazepam. Drugs for treating insomnia, zolpidem and zopiclone, were also identified in blood samples from DUID suspects over the study period. Other therapeutic agents were encountered in only 1-2% of all cases.

CONCLUSIONS

The dramatic increase in DUID after the zero-tolerance law came into force probably reflects enhanced police activity and more enthusiasm to apprehend and charge individuals for this offence. Illicit drugs, particularly amphetamine and cannabis, and poly-drug use were predominant compared with use of scheduled prescription drugs. The typical DUID offender in Sweden abuses central stimulants, particularly amphetamine, and has probably done so over many years. Options for treating offenders for their underlying substance abuse problem should be considered instead of the more conventional penalties for drug-impaired driving.

Age- and gender-related differences in blood amphetamine concentrations in apprehended drivers: lack of association with clinical evidence of impairment

BACKGROUND

New legislation aimed at combating driving under the influence of drugs (DUID) in Sweden stipulated zero-concentrations in blood for scheduled substances. DUID suspects (n = 300), with amphetamine as the only psychoactive drug identified in blood, were investigated in relation to age and gender. In a smaller retrospective sample (n = 70) the relationship between clinical tests of impairment were compared with the concentration of amphetamine in blood.

MEASUREMENTS

All forensic blood samples were subjected to a broad toxicological screening analysis by immunoassay methods [enzyme multiplied immunoassay technique/cloned enzyme donor immunoassay (EMIT/CEDIA)] and positive results were verified by gas chromatography-mass spectrometry (GC-MS). The limit of quantitation (LOQ) for determination of amphetamine in blood was 0.03 mg/l. People suspected of being under the influence of drugs were examined by a physician who asked various questions about state of health and use of drugs and also administered simple psychomotor and cognitive tests of impairment. After conducting these tests the physician concluded whether the suspects were not impaired, slightly, moderately or highly impaired by drugs other than alcohol.

FINDINGS

Among 300 DUID suspects with amphetamine in blood there were 246 men (82%) and 54 women (18%). Mean age (+/- SD) of the men was 37.1 +/- 8.7 years compared with 35.5 +/- 7.1 years for the women (P > 0.05). The frequency distribution of blood amphetamine concentration was positively skewed with mean, median and highest values of 1.0 mg/l, 0.9 mg/l and 7.1 mg/l, respectively. The mean concentrations were slightly higher in the women 1.11 mg/l (median 1.0 mg/l) compared with 0.97 mg/l (median 0.8 mg/l) in the men (P > 0.05). There was a weak but statistically significant correlation between the person's age and the concentration of amphetamine in blood (r = 0.18, P < 0.05). The results of clinical tests of impairment showed no relationship with the concentration of amphetamine in blood according to analysis of variance (P > 0.05).

CONCLUSIONS

The lack of association between degree of drug influence and the concentration of amphetamine in blood speaks against the notion of introducing concentration per se limits or graded penalties depending on the blood-concentration of this stimulant. Zero-concentration limits or LOQ-limits are a much more pragmatic way to enforce DUID legislation.

Concentrations of scheduled prescription drugs in blood of impaired drivers: considerations for interpreting the results

We report the concentrations of scheduled prescription drugs in blood samples from people arrested in Sweden for driving under the influence of drugs (DUID). The investigation covered a 2 year period 2004 (N = 7052 cases) and 2005 (N = 7759 cases) and was prompted by recent legislation stipulating zero-concentration limits in blood for controlled substances. However, prescription drugs are exempt from the zero-limit law provided that the medication was being used in accordance with a doctor's prescription. The blood concentrations of various psychoactive substances were compared with the limits of quantitation of the analytic method used and the so-called therapeutic concentration range according to various reference books and tabulations. Diazepam [N = 1950 (26%)] and nordazepam [N = 2168 (28%)] were the therapeutic agents most frequently identified in these forensic blood samples along with other benzodiazepines such as alprazolam [N = 430 (5.6%)], flunitrazepam [N = 308 (4.0%)], and nitrazepam [N = 222 (2.9%)]. The newer hypnotics, exemplified by zolpidem [N = 148 (1.9%)] and zopiclone [N = 111 (1.5%)], were also high on the list of psychoactive substances identified. Interpreting the concentration of a prescription drug in blood in relation to whether the person had taken an overdose or was abusing the substance in question is not always easy. The age, gender, degree of obesity, and ethnicity of the person concerned; the pharmacokinetic profile of the drug; polymorphism of drug-metabolizing enzymes as well as liver and kidney function and blood hematocrit need to be considered. Among preanalytic factors, stability of the drug in blood after sampling, the type of tubes and preservatives used, the dosage form and route of administration deserve consideration. When therapeutic drug monitoring concentrations are compared with forensic toxicology results, then the plasma-to-whole blood distribution ratio of the drug also needs to be considered. In blood samples from DUID suspects, the concentrations of many commonly used sedatives and hypnotics exceeded the accepted therapeutic limits, which gives an indication of the abuse potential of these types of medications.

A rapid fluorimetric screening method for the 1,4-benzodiazepines: Determination of their metabolite oxazepam in urine

Oxazepam is the major metabolite screened in urine samples for the evidence of the use of benzodiazepine drugs. The methods currently used, however, are laborious and time consuming. This paper proposes an oxazepam detection method based on its hydrolysis and cyclization--a reaction catalysed by cerium (IV) in an ortho-phosphoric acid-containing medium--to form 2-chloro-9(10H)-acridinone, a strongly fluorescent molecule. The variables involved in the hydrolysis and cyclization stages were optimised. Oxazepam was detectable in the 5-900 ng mL(-1) range, with a detection limit of 4.15 ng mL(-1) for k=3. The method was successfully used for the determination of oxazepam in urine samples collected at different times after the oral administration of Valium and Tranxilium.

Disability and rehabilitation in the dizzy patient

PURPOSE OF REVIEW

This review focuses on prospective studies of vertigo and balance therapy in the past 3 years, including advances in vertigo-habituation exercises for adults, pediatric intervention, and virtual reality techniques, and, in more depth, the literature pertinent to driving motor vehicles.

RECENT FINDINGS

Increased support has been generated for the efficacy of a minimal, home-based vertigo-habituation program for adults with peripheral vestibular disorders. Vestibular rehabilitation has been shown to be associated with improvements in independence and dynamic visual acuity. Community-based vestibular rehabilitation has been shown to be efficacious for selected patients, after careful screening, when trained personnel provide intervention. Vestibular rehabilitation has been incorporated into the rehabilitation program for head-injured military personnel who will be returned to duty, and multifactorial balance rehabilitation has been shown to be useful for children with hearing and balance impairments. Virtual reality techniques have made significant advances, so immersive environments have potential for rehabilitation for patients with vestibular disorders and for developing training regimens for astronauts to ameliorate some effects of exposure to microgravity. Driving skill, in general, is affected by use of benzodiazepines. For many patients with vestibular impairments driving is a particularly problematic activity of daily living.

SUMMARY

Progress has been made in studies of acute care, community-based, and pediatric vestibular rehabilitation. Work on simulator-based paradigms has moved toward readiness for implementation. Studies of driving have provided some insight into the problems of these patients. More work remains to be done on all of these problems.

Driving under the influence of chlormethiazole

This article describes a case of driving under the influence of the sedative-hypnotic-anticonvulsant drug chlormethiazole. The suspect, who was a physician, was driving dangerously on a busy highway and caused a traffic collision. When apprehended by the police, the man had bloodshot and glazed eyes and pupil size was enlarged. He could not answer the questions properly and his gait was unsteady. A roadside breath-alcohol screening test was positive but an evidential breath-alcohol test conducted about one hour later was below the legal limit for driving of 0.10 mg/L (10 microg/100 mL or 0.021 g/210 L). Because of the special circumstances of the traffic crash and the man's appearance and behaviour, the police suspected that drugs other than alcohol were involved and obtained a venous blood sample for toxicological analysis. The blood contained 0.23 mg/g alcohol, which is above the legal limit for driving in Sweden 0.20 mg/g (20 mg/100 mL or 0.020 g/100 mL), and codeine was also present at a therapeutic concentration of 0.02 mg/L. The conflict between the clinical signs of impairment and the toxicology report prompted a reanalysis of the blood sample with major focus on sedative-hypnotic drugs. Analysis by capillary GC-NPD identified chlormethiazole at a concentration of 5mg/L, the highest so far encountered in traffic cases in Sweden. In 13 other impaired driving cases over 10 years the mean (median) and range of concentrations of chlormethiazole were 1.6 mg/L (1.6 mg/L) and 0.3-3.3 mg/L. This case report underscores the need to consider clinical observations and the person's behaviour in relation to the toxicology report when interpreting and testifying in drug-impaired driving cases.