The purpose of this study was to determine the relationship between blood benzodiazepine concentration and crash risk. Blood samples from 2500 injured drivers were analyzed for benzodiazepines and the relationship between concentration and crash risk was assessed using culpability analysis. Benzodiazepine concentrations were expressed as a proportion of the peak concentration of the drug in blood or plasma for a standard therapeutic dose of the drug. There were 68 drivers (2.7%) who tested positive for at least one benzodiazepine. Of these, 16 (23.5%) also tested positive for alcohol. Drivers who tested positive for benzodiazepines, either alone or in combination with alcohol, had a higher culpability rate than drug-free drivers. There was a significant linear relationship between benzodiazepine concentration and culpability for drivers who tested positive for benzodiazepines alone. The results here provide clear evidence of increased culpability associated with benzodiazepine use, which was marked at higher concentrations. (Author/publisher)
Abstract