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ObjectivesThis study aimed to assess the association between positive roadside tests for delta-9-tetrahydrocannabinol (THC) and other driving-impairing substances and THC concentrations and the age and gender of THC-positive drivers.DesignThis study is based on administrative data.Setting, participants and exposuresNational administrative data on drivers who tested positive in confirmation analysis of driving-impairing substances in oral fluid were assessed (2011–2016, 179 645 tests).Primary and secondary outcome measuresFrequencies of positivity for THC, THC alone and THC plus non-THC substances (stratification by age and gender in 2016) and THC concentration were obtained. Comparisons and univariate and multivariate regression analyses were performed.ResultsOf the 65 244 confirmed drug-positive tests, 51 869 were positive for THC (79.5%). In 50.8% of the THC-positive tests, cocaine and amphetamines were also detected. Positivity for THC and non-THC substances predominated among drivers with low THC concentrations and represented 58.6% of those with levels lower than 25 ng/mL. The mean±SD for age was 29.6±7.7 years (year 2016, n=24 941). Men accounted for 96.3% of all THC-positive drivers. With increasing age, positivity for THC decreased (OR 0.948; 95% CI 0.945 to 0.952; p<0.0001), and positivity for THC and non-THC substances increased (OR 1.021; 95% CI 1.017 to 1.024; p<0.0001). Men were associated with higher THC concentrations (OR 1.394; 95% CI 1.188 to 1.636; p<0.0001).ConclusionsCannabis positivity is frequent among drivers, and polysubstance use is common. Hence, focusing on younger drivers and those with low THC concentrations is encouraged. This study provides evidence on the current implementation of roadside drug testing in Spain and aims to characterise driving under the influence (DUI) of cannabis to increase the awareness of all involved to help them avoid DUI.

BackgroundOpioids can impair psychomotor performance, and driving under the influence of opioids is associated with an increased risk of accidents. The goals of this study were i) to determine the prevalence of opioids (heroin, morphine, codeine, methadone and tramadol) in Spanish drivers and ii) to explore the presence of opioids, more specifically whether they are used alone or in combination with other drugs.MethodsThe 2008/9 DRUID database regarding Spain was used, which provided information on 3302 drivers. All drivers included in the study provided a saliva sample and mass-chromatographic analyses were carried out in all cases. To determine the prevalence, the sample was weighted according to traffic intensity. In the case of opioid use combinations, the sample was not weighted. The detection limit for each substance was considered a positive result.ResultsThe prevalence of opioids in Spanish drivers was 1.8% (95% CI, 1.4–2.3). Polydrug detection was common (56.2%): of these, in two out of three cases, two opioids were detected and cocaine was also detected in 86% of the cases. The concentration (median [Q1-Q3] ng/ml) of the substances was low: methadone 1.71 [0.10–15.30], codeine 40.55 [2.10–120.77], 6-acetylmorphine 5.71 [1.53–84.05], and morphine 37.40 [2.84–200.00]. Morphine was always detected with 6-acetylmorphine (heroin use).ConclusionsDriving under the influence of opioids is relatively infrequent, but polydrug use is common. Our study shows that 6 out of 10 drivers with methadone in their OF (likely in methadone maintenance programs) are using other substances. This should be taken into account by health professionals in order to properly inform patients about the added risks of mixing substances when driving.

BackgroundSome drugs impair tasks related to driving, and roadside drug testing remains an important tool for deterring driving under the influence of them.ObjectiveTo assess the presence and concentration of methadone, and their combined use with other drugs (laboratory confirmation after the on-road screening) in Spanish drivers between 2011–2016.MethodsIn Spain, roadside mandatory drug testing using saliva are carried out by the Traffic Police using Dräger DrugTest® 5000, DrugWipe®, or Alere™ DDS®2 Mobile Test System. For positive cases in the period covered, 65244, confirmation analysis and quantification of methadone using chromatographic techniques were performed. Statistical analysis was carried out with R programming language (3.4.1) and SPSS version 23.0.FindingsMethadone was confirmed in 4.1% of positive cases: these tested also positive to 6-acetylmorphine (heroin metabolite, 81.9%) and other illicit drugs, such as cocaine (80%) and cannabis (45%). Only in a minority of methadone positives (0.4%) cases no other substances were detected. Concentration values reached important levels (median 201.4 ng/mL) and there was a relationship with age (R-squared=0.1475, p<0.005).ConclusionsPoly drug use (heroin, cocaine, cannabis) was the rule in drivers with methadone positive confirmation analyses.Policy implicationsAs methadone is a physician prescribed medication, improving opioid prescription, promoting the use of less driving-impairing medications, and giving more clear information to patients (risk communication) is a need.This work was supported by the Instituto de Salud Carlos III, Redes Temáticas de Investigación Cooperativa, Red de Trastornos Adictivos [grant RD16/0017/0006], co-funded by FEDER funds of the European Union: a way to build Europe.