Responsibility for non-fatal collision: the abuse of benzodiazepines

This study is part of a larger project examining detection of drugs in the blood of injured drivers and the odds of being responsible for a collision in which the driver is injured. Motorists taken to hospital after a motor vehicle collision in Victoria, Australia, are required to provide a sample of blood for analysis. This sample is routinely analysed for the presence of proscribed drugs and alcohol. The samples were also analysed for impairing substances including benzodiazepines. Collisions were subject to responsibility analysis and the odds of being responsible for collision compared with the drug and alcohol free cohort. 1809 drivers injured in collisions occurring between September 2009 and October 2010 have been included in this study. 184 (10.2 per cent had a benzodiazepine present, mostly diazepam and its metabolites). 20.1 per cent had benzodiazepines in toxic range indicating abuse of medication. The number of drivers with toxic levels of benzodiazepines reflects abuse of medication and all these drivers were responsible for the collision. Benzodiazepines are associated with an increase in odds of being responsible for non-fatal collision. The relative risk is probably dose related which has implications for prescribers and their patients. The combination of benzodiazepines with any amount of alcohol causes synergistic impairment to the extent that 98 per cent of drivers were responsible for the collision in which they were injured. The misuse of benzodiazepines as intoxicants requires attention of legislators and enforcement agencies. Traditional interventions may not be effective as impairment is unlikely to be detected by police if the blood alcohol concentration is low.